NASA / CP-2001-210427 

Proceedings of the 4th Conference 

on Aerospace Materials, Processes, 

and Environmental Technology 

D. E. Griffin, D. Cross Stanley, Editors 

Marshall Space Flight Center, Marshall Space Flight Center, Alabama 

Proceedings of a conference held in 

Huntsville, Alabama, September 18-20, 2000 

National Aeronautics and 

Space Administration 

Marshall Space Flight Center MSFC, Alabama 35812 

February 2001 
Proceedings of the 4th Conference 

on Aerospace Materials, Pr 

and Environmental Technology 

D.E. Gnffm, D. Cross Stanley. Edifors 

hfarshall Space Flight Center, Marshall Space Flight Center, Alabama 

February 2001 
Available from: 

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Sponsoring Agencies 

National Aeronautics and Space Administration 

George C. Marshall Space Flight Center 

MSFC, AL 358 12-9999 

NASA Operational Environment Team 

George C. Marshall Space Flight Center 

MSFC, AL 358 12-9999 

NASA’s Materials and Processes Working Group 

Attn.: Dennis Griffin, Chainman 

Mailstop: ED35 

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3025 Boardwalk Street 

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Aerospace Industries Association 

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National Center for Advanced Manufacturing 

Attn: John Vickers 

Mailstop: ED35 

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University of New Orleans 

College of Engineering 

New Orleans. LA 70 I48 
Proceedings of qfh Conference on Aerospace Materials, Processes and 

Environmental Technology (AMPET) 

Opening Session 

Challenges for Aerospace Materials & Processes 

Dr. Charles E. Browning 

Advanced Space Flight and Environmental Concerns 

Dr. Ann F. Whitaker 

Session A1 : Engineering Evaluation of Solvent Substitutes 

Nonjlunimuble, Nonaqueous, Low Atmospheric Impact, High Performance Cleaning Solvents 

Patrick M. Dhooge, Suzanne M. Glass, and Jonathan S. Nimitz 

Aerospace Applications for AK-225 

Kenroh Kitamura, Masaaki Tsuzaki. and Stephen D. Stagliano 

HFEs In The Aerospace Industry: A Logical Alternative To CFCs And Other Halogenated Cleaning 

Solvents 

David A. Hesselroth 

Elimination Of MEK And Lacquer Thinner In Department Of Defense Painting Operations 

Joseph A. Lucas and Eric Lethe 

Session A2: Advances In Materials Development 

Lightweight Multi-Layer Structural Materials 

H.H. Lcgner. W.T. Laughtin, V. Di Cristina, D. Marshall, and R. Singler 

Asbestos Free Insulation Development For The Space Shuttle Solid Propellant Rocket Motor 

(RSRM) 

Larry D. Allred and Norman F. Eddy 

Aerogel Projects Ongoing In MSFC 's Engineering Directorate 

David Shular. Gweneth Sinithers, and Joel Plawsky 

Electroactive Polymers As Artificial Muscles - Reality And Challenges 

Yoseph Bar-Cohen 
Session A3: National Center For Advanced Manufacturing Workshop 

National Center For Advanced Manufacturing Overview 

John Vickers 

Advanced Engineering Environments - Implications For Aerospace Manufacturing 

Dale Thomas 

State, Industry, And Education Partnerships Expanding Education To Meet Workforce Challenges 

James E. Swindell. Donna C. Bass. and William R. Reynolds 

Composite Manufacturing For Space Launch Vehicles 

Donna Y, Knezevich 

Session B1: Elimination Of Heavy Metals 

Laser Cladding/Giuzing As A Surface Coating Alternative 

Rob Hull, Dave Firsich, Chuck Woods, and John Eric 

Testing Of Environmentally Preferable Aluminum Pretreatments And Coating Systems For Use On 

Space Shuttle Solid Rocket Boosters (SRBs) 

Catherine Clayton, Lee Zook, and Randy Raley 

Trivalent Chromium/Organically -Modified Silicate Composite Coatings For Corrosion Protection Of 

Aluminum Alloys 

Edward Knobbe. Elvira Stesikova. Tammy Metroke, and Olga Kachurina 

HVOF Thermal Spray Coating As An Alternative To Hard Chrome Plating On Military Aircraft 

Bruce D. Sartwell 

The Use Of Ion Vapor Deposited (IVD) Aluminum For The Space Shuttle Solid Rocket Booster 

Howard Novak, Bill Imre. and Randy Raley 

Session B2: Advances In Materials Analysis And Testing Techniques I 

High Temperature Material Performance Testing Using Continuous Wave Carbon Dioxide Lasers 

Timothy Johnson 

Thermographic Nondestructive Evaluation Of The Space Shuttle Main Engine Nozzle 

Ven3cation Of Shearography NDE Methods On Space Shuttle, X-33, And Delta IV Launch Vehicles 

James L. Walker, Samuel S. Russell, Matthew D. Lansing. and Paul Caraccioli 

John W. Newman 

Thermographic Analysis Of Composite Cobonds On The X-33 

James L. Walker, Matthew D. Lansing. and Samuel S. Russell 
Session B3: Developments In Metals Processes I 

Evaluation Of Forces On The Welding Probe Of The Automated Retractable Pin-Tool (RPT) 

R. Jet’frcy Ding 

Friction Stir Weld Modeling At MSFC: Kinematics 

Arthur C. Nunes, Jr. 

Aluminum Lithium Alloy 2195 Fusion Welding Improvements With New Filler Wire 

Carolyn Russell 

Session B4: Non-Metals Processes I 

Fabrication Of Composite Combustion Chamber/Nozzle For Fastrac Engine 

T. Lawrence, R. Beshears, S. Burlingame. W. Peters. M. Prince. M. Suits, S. Tillery. L. Bums, M. Kovach, and 

K. Roberts 

Large Composite Structures Processing Technologies For Reusable Launch Vehicles 

R.G. Clinton. Jr.. John H. Vickers, A. B. Hulcher, Norman J. Johnston, William M. McMahon, R. J. Cano, H. L. Belvin, 

Walter Franklin. Don Sidwell, Keith Mclver. Tod Palm. and Robert Biggs 

Composite, Cryogenic, Conformal, Common Bulkhead, Aerogel-Insulated Tank (CBAT) 

Materials And Processing Methodologies 

Michacl P. Kovach. .I. Keith Roberts, William M. McMahon, and Jeffery L. Finckenor 

Session C1: Developments In Coating Removal Processes 

Coating Removal Technology Using Starch Based Abrasives, A Review Of Current Aerospace 

Applications Using The Envirostrip@ Dry Stripping Process 

Dcnih hlonette and Cameron Drake 

Removal Of Zirconia Thermal Barrier Coatings And MCrAlY Bond Coatings From Turbine Bludes: 

A Comparison Of Methods Based On Chemical Stripping, Water Jet, And Salt Bath 

A. Scrivani. U. Bardi. G. Ballerini, D. Bonacclii, M. Fantini, R. Groppetti, S. lanelli. and G. Rizzi 

Joint EPMNASMUSA F Interagency Depainting Study 

Marceia Clark-lngram 

Evaluation Of Various Depainting Processes On Mechanical Properties Of 2024-T3 Aluminum 

Substrate 

Preston B. McGill 
Session C2: Ceramic Matrix Composites 

Concept For Determining The Life Of Ceramic Matrix Composites Using Nondestructive 

Characterization Techniques 

Michacl Effinger, Bill Ellingson, Todd Spohnholtz, and John Koenig 

Low-Cost Ceramic Matrix Composites 

Witold Kowbel, C. Bruce, K.T. Tsou, and J.C. Withers 

Fabrication and Testing of Ceramic Matrix Composite Propulsion Components 

Michcal Effnger. R. G. Clinton, Jr., Jay Dennis, Sandra Elam, Gary Gengc, J. Doug Kiser, Andy Eckel. Martha 

Jaskowiak and Jerry Land 

Rapid Fabrication Of Monolithic Ceramic Parts Reinforced With Fibrous Monoliths For Aerospace 

Applications 

R. Vaidyanathan, J. Walish, J.L. Lombardi. M. Fox, M. Rigali. and M. Sutaria 

Session C3: Rapid Prototyping 

Solid Free form Fabrication Of Continuous Fiber Rein forced Composites For Propulsion 

Applications 

R. Vaidyanathan, J. Walish, M. Fox, M. Rigali, M. Sutaria, J.W. Gillespic, Jr., S. Yarlagadda, and 

M. Effinger 

An Example Of Economic Value In Rapid Prototyping 

John R. Reagan, Edward P. Braunscheidel, and Robert L. Haucr 

High-Efficiency Monolithic Lightweight Aluminum Cast Structure 

John Bowkett 

Preliminary Component Integration Utilizing Rapid Prototyping Techniques 

Ken Cooper and Pat Salvail 

Session C4: Innovative Materials Applications 

Multifunctional Carbon Foams For Aerospace Applications 

Daren K. Rogers and Janusz Plucinski 

Polymer Matrix Composite Materials Oxygen Compatibility 

Tim Vaughn, Tom Owens, and Robert Jacobs 

Low Density Monolithic Metal Honeycombs by Thermul Chemical Processing 

Jim Lee, Joe Cochran. Dave McDowell, and Tom Sanders 

TransHab Materials Selection 

Michael Pcdley 
Session D1: Evaluating Pollution Prevention Methodologies 

Identi’cation Of High Performance, Low Environmental Impact Materials And Processes 

Using Systematic Substitution (Sys) 

Patrick M. Dhoogc and Jonathan S. Nimitz 

Selection Criteria For Alternative Technologies, As A Method Of Hazardous Waste 

Minimization 

Eric Lcthe 

Joint Group On Pollution Prevention, Partnering For Progress 

Robert P. Hill and Michael McCall 

Liquid Filtration For Component Reliability And Waste Minimization 

Edward Kanegsberg and Barbara Kanegsberg 

Chemical Aging Of Environmentally Friendly Cleaners 

L.L. Biegcrt, K.B. Eiaiis, B. D. Olsen, and B.L. Weber 

Session D2: Advanced Materials For Extreme Environments 

NAtional Materials In formation System 

Jeff Ciuthric 

Durability Characterization Of Advanced Polymeric Composites At Cryogenic Temperatures 

Thomas S. Gates 

Development Of Metal Matrix Composites For NASA’s Advanced Propulsion Systems 

Jonathan A. Lee and Sandy Elam 

Inorganic-Organic Hybrid Polymers For High Temperature Aerospace Applications 

Teddy M. Keller 

Session D3: Manufacturing Technology Topics 

Integrated High Payoff Rocket Propulsion Technologies Program Material Development Plan 

R.G. Clinton. Jr.. Brian Reed, Michael Stropki, Dan Cleyrat, Brian Stucke, and Shawn Phillips 

X-33 LH2 Tank Failure Investigation Findings 

Mindy Niedermeyer 

Assessment Of The State-Of-The-Art In The Design And Manufacturing Of Large Composite 

Structures 

Charles E. Harris 
Session D4: Evaluation Of Cleaning And Bonding Materials And Processes 

A Mass Spectrometer-Based Tool For In-Process Analysis Of RSRM Components 

Michael Mcltzer, Carolyn Koestcr, and Neil Sagers 

Effects And Detection Of Silicone And HD2 Grease Contaminants 

Jerrell W. Blanks 

Physical Evaluation Of Cleaning Performance - We Are Only Fooling Ourselves 

Earl Pratz 

Session E 1 : Alternatives For Chemical Replacements 

Low Environmental Impact, High Performance Foam Blowing Agents Based On lodofluorocarbons 

Patrick M. Dhooge, Suzanne M. Glass. and Jonathan S. Nimitz 

Update: HFC 245fa Blown Foam Development With External Tank Spray Foams 

Simon Davis 

High-Performance, Low Environmental Impact Refrigerants 

Patrick M. Dhoogc, Edward T. McCullough, Suzanne M. Glass, and Jonathan S. Nimitz 

VOC Compliant Wax Removal Process 

Alan Brown, Datid Grimtnett, and Margarite Sylvia 

Highly Effective, Low Toxicity, Low Environmental Impact Total Flooding Fire Suppressants 

Patrick M. Dhoogc, Suzanne M. Glass, and Jonathan S. Nimitz 

Session E2: Advances In Materials Analysis And Testing Techniques I1 

Promoted Combustion Of Metals In A High-pressure, Flowing Oxygen Environment 

Migucl J. Maes and Joel M. Stoltzfus 

Problem Solving Applications Of Chemical Fingerprinting 

Michael 0. Killpack, Dennis J. Fife, Chad R. Saunders. Charles R. Whitworth, and William H. McClennen 

Resources Available For Hazards Analysis Of Aerospace Fluids 

Stephen S. Woods, Walter F. Stewart, David L. Baker, and Harold D. Bceson 

Chemical Fingerprinting Of Materials Developed Due To Environmental Issues 

Doris A. Smith 

Use Of GUMS And Microtome Techniques To Evaluate ODC Cleaner Diffusion And Evaporation 

In Insulation And Phenolic Case Material 

L.L. Biegert 
Session E3: Non-Metals Processes I1 

Electron Beam-Cured Polymer Matrix Composites: Processing And Properties 

(icorgc Wrenn, Barbara Iranic, Brian Jensen. and Alan Nettles 

Manu facture Of Porous Ceramic Materials By Combustion Synthesis 

1.. A. Whelan Robinson. H. C. Yi, and J.Y. GuignC 

The Composites Affordability Initiative 

John Mistrctta 

Advanced Ceramic Matrix Composites for Aerospace Applications 

John Gamier, Bill Patterson, Bob Klacka and Paul Gray 

Session E4: Developments In Metals Processes I1 

Aluminum Investment Cast Spacecraft And Aerospace Structures 

John Bowkett 

Vacuum Plasma Spray Of Cu-8Cr-4Nb Alloys For Advanced Liquid-Fuel Combustion Chambers 

Frank Zimmerman. Sandra Elan, David Ellis, Hcather Miller, Timothy McKcchnic and Robert Hickman 

Dynamic Oxidation Of A Plasma-Sprayed Cu-Cr Coating 

K.T. Chiang 

Manufacturing Challenges Implementing Material Changes For Super Lightweight Tank: A 

Welding Process Perspective 

Chip Joncs and Kirby G. Lam less 

Cryogenic Tank Technology Program (CTTP) 

Tim Vaughn 

Session Fl : Methods For Cleaning And Cleanliness Verification 

Elimination of Carbon Tetrachloride for Quantitative Hydrocarbon Surface Analysis 

Vonnie M. Douglas 

Ellipsometric Verification And Evaluation Of Clean Surfaces 

Waync Thompson 

Improved Detection Technique For Solvent Rinse Cleanliness Verification 

Steven D. Hornung and Harold D. Beeson 

Criteria For NVR Solvent Replacement 

Kenneth Lucy. Dianne J. Coleman. Joseph C. Uht. and Graham S. Arnold 

Critical Surface Cleaning And Verification Alternatives 

Donald M. Melton 
Session F2: Advanced Metals Research 

Effects Of Cryogenic Treatment On The Residual Stress And Mechanical Properties Of An Aerospace 

Aluminum Alloy 

Po Clien, Robert Bond, Tina Malonc, and Pablo Torres 

Toughness Of Ultra High Strength AFI410 Type Steels 

Luana E. lorio and Warren M. Garrison, Jr. 

Segregation Behavior Of Sulfur And Other Impurities Onto The Free Surfaces In ED-Ni Deposits 

Binayak Panda and Gregory Jerman 

Statistical Analysis Of Strength Data For An Aerospace Aluminum Alloy 

Lynn Neergaard and Tina Malone 

Electrostatic Levitation Processing Of Bulk Metallic Glass Forming Liquids 

C. C. Hayes, J. Schroers, U. Gcyer, and W. L. Johnson 

Session F3: Emerging Technologies 

Residual Stress Prediction 112 Machined Workpiece Surface 

Troy Marusich and Paul Bayer 

Easily Processable High Temperature And Flame Resistant Phthalonitrile composites For 

Aerospace Applications 

Teddy M. Keller and Harry N. Jones 

Real Time Video Recording Of Extremely High Temperature Processes 

Thad Hoffman 

Vapor Grown Carbon Fiber/Phenolic Matrix Composites For Rocket Nozzles And Heat Shields 

R. D. Patton, C. U. Pittman, Jr.. L. Wang. J. R. Hill, and A. Day 

Session F4: Environmental Monitoring Methods 

Ambient Air Monitoring Of Respirable Particulate Matter (PM,, ) And Total Suspended Particulate 

(TSP) From The RD180 Rocket Engine Tests At The NASA Marshall Space Flight Center 

John Hughes and Kathy Lehr 

Gas Emission Measurements From The RD 180 Rocket Engine Tests At The NASA Marshall Space 

Flight Center 

H. Richard Ross 

Overview of the City of Huntsville Air Pollution Control Program 

Daniel Shea 

Potential Effects on the Huntsville Area of Revised National Ambient Air Quality Standards for 

Ozone and Fine Particulate Matter 

Daniel Shea 
Posters 

Development Of Lead-Free Energy For Space Shuttle Blast Container 

Donald Balies, Thomas Ingram, Howard Novak, and Albert Schricker 

Polymer Matrix Composites (PMCs) Cryopipe For Rocket Engine Lines And Ducts 

David Bettinger 

Nanotechnology Concepts At Marshall Space Flight Center - Engineering Directorate 

Biliyar Bhat, Raj Kaul, Sandeep Shah, Gweneth Sniithers, and Michael D. Watson 

Microstructure, Mechanical Properties, Hot-Die Forming, And Joining Of 47XD Gamma TiAl 

Rolled Sheets 

G. Das, S. Draper, J.D. Whittenberger, and P.A. Bartolotta 

At Last, Something New! Cleaning Without Chemistry, And Reusing The Waste Water! 

John Durkee 

Polymer Matrix Composite (PMC) Analog Processes For Lightweight Aluminum Matrix Composite 

(AMC) Structures 

Brian Gordon 

Further Studies Of Materials Compatibility In High- Test Hydrogen Peroxide 

Rudy Gostowski and Tom Owens 

X- Traktor: A Rookie Robot, Simple, Yet Complex, Impeccably Designed, A Very Innovative 

Multidisciplinary Engineering Masterpiece 

Arthur J. Henderson, Jr. 

Laser Surface Modification of TiAl Intermetallics 

Sherman McElroy and Ramana Reddy 

Characterization Of Ceramic Matrix Composite Combustor Components: Pre And 

Post Exposure 

G. Ojard, G. Linsey, J. Brennan, R. Naik, R. Cairo, R. Stephan, J. Hornick, 

and D. Brewer 

Automated Acquisition And Analysis Of Digital Radiographic Images 

Richard Poland, David Inniel, Boyd Howard, Randy Singer, and Bob Moore 

Fabrication Of Low-Cost, High- Temperature Composites For Rocket Propulsion Systems 

Mark J. Rigali, Manish Sutaria, Anthony C. Mulligan, and Ranji Vaidyanathan 

Electro Spark Alloy Processing for Aerospace Components 

Michael Riley 

Detection, Identification, and Quantification of Surface Contamination 

M. Martin Szczesniak. Michael Beecroft. and Phillip Mattison 

Quadruple Lap Shear Processing Evaluation 

Tony N. Thornton 
5th Conference on 

Aerospace Materials, 

Processes, and 

Environmental 

Technology 

(AMPET) 

Week of September 16, 2002 (tentative) 

Von Braun Center 

Huntsville, Alabama 

Objective: The purpose of this conference is to provide a forum for materials and processes 

engineers, manufacturing engineers, environmental engineers, scientists, and managers to describe, 

review, and critically assess the evolving advances in materials, manufacturing, replacement, and clean 

propulsion technologies from the standpoint of their significance, application, impact on aerospace 

systems, and utilization by the research and development community. 

For additional information, contact Dawn Cross Stanley, Administrative Chair 

Telephone: 256-544- 1835 

E-mail: dawn.cross@jmsfc.nasa.gov 

Conference URL: 11 ttp:.:’/amiiet.tnsfc .nasa.povI’ 
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Session E I (continwd) 

High performame. Low 

Envinmmentd Impact Refrigerants 

Patrick L?hmge, fhrd T. 

M&-itlknigh. Suzanne M. Glass, 

Jonathan S. Nimitz (fnvimtal 

T~hnology VC fducation Center) 

Volatile Organic Compound 

Cornpliant Wax RemoMl Process 

Alan Brown, Dad Gmt. 

Margade Sylvia (The Boeing 

Company - Rocketdyne) 

Highly Efktive. Low Toxicity, Low 

Environmental Impact Totd Flooding 

Fire Suppnrssants 

Patrick Dhoogr. Suzanne M. das. 

Jonathan S. Nimitz (Envimtal 

Tectrdogy S Education Center} 

i2:30 - 

2:00pm 

I :30 pm Demonstration 

session F I (Orrhestra) 

Methods lor Cleaning and Ueanliness 

Verification 

Chair: Jerrell Blanks, 

Thiokd Prquh Groyp 

Elimination of 6mOn Tetrachloride 

for QtMntitatiw Hydrocarbon 

Analysis 

Vonnie Douglas (The Boeing 

Cbnqpany . Metdyne) 

Ellipsmetric Verification and 

Evduation of Clean SurQces 

Wayne Thompson (univerrity of 

Alabama in Huntsvilk) 

Imp4 @et& Technique lor 

Solvent Rime Cleanliness Verification 

s tm 0. hng (Fbwpd); 

tiadd Ekwm (White Sad Test 

FXiXtY) 

Replacement 

Criteria tor NVR Solvent 

Kmh Luey. Dane J. CXman. 

Jospph C. Uht. &ham 5. Ad 

(The Aenym Copmtkm) 

Critical Surface Cleaning and 

Verifation Alternatives 

An~kfM. Wtm (Lockhttd 

Marrjn MWiQwath) 

Session E2 (continued) 

Rescu~es Avaibble for Hazards 

Analysis of Aerospace Fluids 

Kurt Rathgetw (Honq/well); Ste 

S. Woods (Allied Signal T&id 

Setvim Copmtim); Walter F. 

Stewart (LgM Terhdogis, Im.); 

Dad L. Baker. Hadseffon 

(White Sad Test Facility) 

Chemiial Fingerprinting of Materiais 

Developed due to Envinmmental 

lrmes 

Doris Smith. Mary Gpezza. fmile 

f vans, Laurie Rainlo (Luckheed 

Martin Space Systems) 

Use of GUMS and Microtome 

Techniques to Evaluate OK Free 

Ueaner Diffusion and Evaporation in 

Insulation and Phenolic Case Material 

L. L. &egeri (Thiokol Propulsion 

(;roupJ 

jession E3 (continwd) 

The Composites Affordabiliy 

lnit iat ive 

john Mistretta (Wright Patterson 

Air Force Bag) 

u Advanced Ceramic Matrix 

Composites tor Aerospace 

Applications 

Jdm Gamier, Bill Patterson. Bob 

Klacka. Paul Gray. Sm Hemtad 

(hnepdll Advad hptes) 

Lunch --- Poster Session People's Choice Award --- Exhibits 

Hybrid Propulsion (Exhibit Area) 

Terry Abel (Marshall Space Flight Center) 

Session F2 (Salon I A) 

Advanced Metds Research 

Chair Eric fichinger, 

Rokng 

The EMS of Cryogenic Treatment 

on the Memanical Properties of an 

AI-Li Alloy 2 I95 

Po Chen. h'& Bond (/IT Rseatrh 

hiMe); Tina Malm. Pabb Tom 

(Marshall Spm Flight Catw) 

Toughness of Ultra Strength AF 

Warn M. Gartisun. Jr.. Luam 

kKi0 (Camegie Mdh Univmt y) 

Segtqation Wi of Sulfur and 

Other impriks onto the Free 

Surfaces in ED-Ni Deposits 

6im yak Panda (UT Resea& 

kitute); Gqoiy Jerman (Marshall 

me Flight bter) 

Statisticd Analysis of AIU 2 I95 

Strength and Toughllgs Data 

L yrm Nmguanl (UT Rsa& 

Institute); Tina Malm (MJ&// 

We Flight Ctntw) 

Electrostatic Levitation Processing of 

blk Metallic &ss Forming Liquids 

CC. Hays. 1. Sdum, U. Gtyer, 

W. L. Johnxn (Calihotnia Institute of 

141OTypeSteels 

TK-1 

Session F3 (Sdon I B) 

Emerging T&nolcgies 

Chair R.D. Patton. 

Mksissi~~ State Uniwrsity 

Residual Stm Pdiion in 

Machined Wokpiece Surfaces 

Paul Bayer, Troy Ma~sich (Third 

wave systems. IN.) 

Easily Processable High 

Temperature and Flame Resistant 

Phthdonirde Composites for 

AeruspaceApplicatiis 

Teddy M. Kdk, Harry N. Jones 

(Naval Research labomtoiy) 

Real Time Video Recording of 

Extemely High Tenymatue 

ProCesseS 

Thad Hoffman (bntrd Vision. Inc) 

Phenolic Matrix Composites for 

Rocket Nodes and Heat Shields 

R. D. Patton. CU. Pittman, Jr., L. 

Wang (MWpi State University); 

J.R. Hill (Chakton Air Fm 

Base); A. Day (Thiokd) 

VaporGmCamOnFber/ 

Session E4 (continwd) 

Manulacturing Challenges 

Implementing Material Changes for 

Super Lightweight Tank: A Welding 

Process Perspeaive 

Chip hes. Kihy G. Lades 

(Marshall Space Flight Ctntm) 

Cryotank Technology Program 

(mp) 

&tw) 

Tim Vaughn (Ma&ll Space Flight 

&on F4 (Salon 2) 

Environmental Monitoring Methods 

chair: Greg Smith, 

AJT & Associats, Inc. 

p Ambient Air Monitoring of 

Respirable Particulate Matter 

(PM IO) and Total Suspended 

Particulate (TSP) During the RDI80 Rocket Engine Tests at the 

NASA Marshall Space Flight Center 

John Hughes, khthy Lehr (GB Terh) 

I Gas Emission Measurements from 

the R@- I80 Rocket Engine Tests at 

the NASA Marshall Space Flight 

Center 

H. Richard ROSF (GB Tech) 

http: / /am pet .msfc.nasa.gov 
SEPTEMBER 20, 2000 

SessiiDI (Sdon IA) 

Eduating Pollution 

Prewntion Methodologies 

char: ahn spnwro. 

NASA Headquartem 

Identification of High Performance. 

Low Envimmentd Impact Materials 

and Pm Using Systematic 

Substitution (SyS) 

Patrick M. Dboge, Jonathan S. 

Nimitz (Environmental Tt~hlogy f 

Education hter) 

%ion Criteria for Alternate 

Technologies as a Method of 

Hazardous Waste Minimization 

Eric L& (inlad T&nology, 

Joint Group on Fbllution Prewntion. 

Robert Hill (Kennedy Space cpnterl; 

MiM M&II (Concurrent 

T~hrw~bcorpOration) 

Liquid Filtration for Comporwnt 

Reliability and Waste Minimization 

Edwardbnegderg, Barbara 

Kanegdwg(BFKSolufions) 

Incorpor~M 

partnering for Progress 

Chemicd Aging of Environmentally 

L.L. Bqert, K.B. Evans, B.P. Oh. 

B. L. W& (Want T~~b: 

lhiokd Prqukim) 

FnendlyueanerS 

1o:oo - 

m30 am 

IO: I 5 am Demonstration 

SessionEl (Salon IA) 

Ahematices for 

Chair AimBrown 

The &ng Company. Wetdyne 

Mrmance Foam Wng Agents 

Basedon~~m~ 

Patrick Dhooge. Suzanne M. Glass. 

Jonathan S. Nhitz (Enwrvtmm~ 

T~hology E Education Center) 

Update: HFC 245fa Blown Foam 

De&pment with Extemd Tank 

Spray Foams 

sinm Davis (L0ckhm-i Martin 

CkmiicdReplacement 

Low Envimtal Impact, HighSF systems) 

(continued on nart page) 

Session 02 (Salon 16) 

Advanced Materials 

for Extreme Envimnments 

Chair: Teddy M. Kdkr. 

Naval Research Labratory 

National Materials Information 

kfiiey Guthrie (AMPTlAq 

9 Durability Characterization of 

Ahnced Polymeric Composites at 

Cryogenic Temperaturn 

Thomas S. Gates (Langky 

Research Ctnter) 

Development of Metal Matrix 

Composites for NASA’s Advanced 

Propulsion Systems 

Jonathan A. Le. Sandy Earn 

(Marshdl Spacp Flight Ctnttq) 

InorganicQpnic Hybrid Polymers 

for High Temperature Aerospace 

Applications 

Teddy M. Kelkr (Naval Research 

Laboratq) 

system 

Sgsi D3 (Orchestra) 

Manufacturing 

Technokgy Topicf 

Chair: Charles &ms, 

Langley Research Center 

Integrated High-kydf kckd 

Propulsion Technologies Program 

Materials Dewlopment Plan 

R. G. Clinton (Marshall Space Flighr 

Center); &an Reed (Ghn Research 

Center); Michael stropki. Dan 

Ckyrat, Brian Stucke, Shawn 

Phillips (Air Force hksearch 

Labratoy) 

Findings from the X-33 Hy&ogen 

Tank Failure Investigation 

Mindy Nidwneyer (X4arshall 

Spaw Flight Center) 

Assgsment of the State of the Art 

in the Design and Manufacturing of 

Large Composite Structures 

Charles E. Harris (Langley karch 

Ctnter) 

Break --- Exhibits 

Pneumatic impact (Exhibit Area) 

Kurt Rathgeber (Honeywell) 

Session E2 (Salon I B) 

Advances in Materids Analysis 

and Testing Techniques II 

Chair: Fmnk Key 

Native Amskin Smkw, Inc. 

- Promted combustion of Metals in 

a High-pressure, Flawing Oxygen 

Environment 

Migwl 1. Mats (Allid Signal 

Terhniwl Services Chporation); 

Joel M. Stdtlfu, (White Sands Test 

FaCiitd 

ProMem Solving Applications of 

Chemical Fingerprinting 

MiM 0. Killpack. hnis J. Fife, 

chad R. Saudm, Chak R. 

Whiwh. William H, McCltnnen 

(Thiokol Propuh Gmp) 

(contiinwd on rwxt page) 

sgsii E3 (Sdon 2) 

N~n-Metal~ Procgse~ II 

Chair: R.G. Clinton 

Marshall Space Flight Center 

Elearn Beam-Cud Polymer 

Matrix Composites: Pmessing and 

(Oak Ria‘’ National htoy); 

Brian Jtnm (Langley Research 

btet); Alan Nmk (Marshall 

Space Flight Center) 

Manufaaule of Porn Ceramic 

Materials by Combustion Synthesis 

LA. Wan Robim. H.C. Yi, 

J. Y. Guigne ’ (Guigw ’ International 

Ltd.) 

(contin& on rwxt pas) 

Propertie5 

&I&? wm. Barbam fm 

Session D4 (Salon 2) 

Eduation of Cleaning and 

Bonding Materials and Pnxesses 

Chair: Jill Keen, 

ThikdPrupukion Gmp 

A Mass Spxtrometer-Based Tool for 

In-Process Analysis of RSRM 

MiMMeltzw. Grolyn Kcester 

(Lawme Livm NatMnal 

labomtory); MI SageB (Thiokd 

Effects and Detection of Silicone and 

HD2 Grease Contaminants 

,cpmJlBiartks(l~dPropulsiw? 

components 

Prupuh) 

c;roupl 

phvslcal Evaluation of Cleaning 

performance - We Are Only Fooling 

Ourselves 

fad Pratz (Lockhtd Martin Space 

SY-llS) 

Session E4 (orchgtra) 

Dewlopments in Met& Pnlcgses U 

Chair: Carolyn Rdl 

Marshall Space Flight Cmter 

Aluminum Inwment Cast 

Spacecrafi and Aerospace Structures 

John 8owket1 (Nu-Gst, Inc.) 

Vacuum Plasma Spray of CuCrNb 

Alloy for Low-Cost. LqLife 

Combustion Chamben 

Frank Ziman (Marshall 3bacp 

Flight Center) 

Dynamic Oxidation of a Plasma 

Sprayed h-G Coating 

K. T. Chiang (The &ng hpan y) 

(continwd on nexi page) 

ht tp : / /am pet .msfc.nasa . gov 
Development of Lead-Free Energy Absorber for Space Shuttle Blast Container PEOPLE’S CHOKE AWARD 

Poster Session visitors will choose one @onaid Balles. Thomas Ingram. Howard Novak. Albert Schricker (United Space Alliance) 

Polymer Matrix Composites (PMCs) Cryopipe for Rocket Engine Lines and Ducts 

@avid Bettinger (The Technology PartnershipJ 

Nanotechnology Concepts at Marshall Space Flight Center - Engineering Directorate 

Biliyar Bhat. Raj Kaul. Sandeep Shah. Gweneth Smithers. Michael I?. Watson (Marshall Space 

Flight Center} 

Microstructure. Mechanical Properties. HotDie Forming, and Joining of 4 7 XD Gamma TiAl Rolled 

Sheets 

(3. Pas (Pratt f Whitney}; 5. @raper. 1.0. Whittenberger. P.A. Bartolotta (Glenn Research Center) 

At Last. Something New! Cleaning without Chemistry, and Reusing the Waste Water! 

John @urkee (Creative EnterpriZes) 

Polymer Matrix Composite (PMC) Analog Processes for Lightweight Aluminum Matrix Composite 

(AMC) Structures 

Brian Gordon (Touchstone Research Laboratory) 

Further Studies of Materials Compatibility in High Test Hydrogen Peroxide 

Rudy Gostowski (Austin Peay State University); Tom Owens (Marshall Space Flight Center) 

X-Traktor: A Rookie Robot. Simple, Yet Complex. Impeccably Designed. A Very Innovative 

Multidisciplinary Engineering Masterpiece 

Arthur .I. Henderson. Jr. (Marshall Space Flight Center) 

Lasrr Surface Modification of TiAl Intermetallics 

Sherman McElroy. R.G. Reddy (The University of Alabama, Tuscaloosa) 

poster presentation to receive the People’s 

Choice Award. 

9 Posters will be judged on relevance, 

creativity, and speaker’s presentation. 

Each Poster Session visitor who attends 

at least 4 presentations may vote for 3 

pmtations. 

Poster Session visitors who cast their 

ballots for the People’s Choice Award 

will be entered in drawings for 

conference door prizes Drawings will 

be immediately after the Poster Session 

(7 Pm). 

The presentation receiving the most 

votes will win the People’s Choice 

Award. 

Presentations that receive the second 

and third most votes will win runnerup prizes. 

The People’s Choice Award and 

runner-up recognitions will be 

presented at the Wednesday luncheon. 

Characterization of Ceramic Matrix Composite Combustor Components: Pre and Post Exposure 

G. Oiard. G. Linsey. J. Brmnan (United Technologies Research Center); R. Naik, R. Cairo. R. 

Stephan, J. Hornick (Pratt & Whitney); P. Brewer (Glenn Research Center) 

POSTER SESSION FORMAT 

followed by 5-minute question-andanswer periods. 

Presentations will be repeated 

throughout the Poster Session length. 

Detailed discussions can be scheduled 

with the presenter from 7 am - 4 pm 

Wednesday in the Break-Out Room. 

Automated Acquisition and Analysis of Digital Radiographic Images 

Richard Poland. David Inmel. Boyd Howard. Randy Singer. Bob Moore (Westinghouse Savannah 

River Company) 

Mark J. Rigali. Manish Sutaria. Anthony C. Mulligan, Ranji Vaidyanathan (Advanced Ceramics 

Research. Inc.) 

Electro Spark Alloy Processing for Aerospace Components 

Michael Riley (Surface Treatment Technologies. Inc.) 

htect ion. ldent ificat ion, and Quantification of Surface Contamination 

PRSentatiOnS will be 5 minute, 

Fabrication of Low-Cost. High-Temperature Composites for Rocket Propulsion Systems 

M. Martin Szczesniak. Michael Beecroft, Phillip Mattison (Surface Optics Corporation) 

Quadruple Lap Shear Processing Evaluation 

Tony N. Thornton (Thiokol Propulsion. SEH@ Operations) INSTRUCTIONS FOR POSTER SESSION 

PRESENTERS 

Poster assembly in the North Hall 

Gallery must be completed by 9:30 am 

on Tuesday. You may set up your 

poster as early as Monday afternoon. 

Posters may be removed between 2 pm 

and 6 pm Wednesday. 

You must be available at your poster 

site during the Poster Session. 

The Break-Out Room is reserved from 

7 am - 4 pm Wednesday for one-onone or round.table discussions about 

your poster topic. Reserve space at the 

conference registration table. 

htt p: / /ampet .msfc. nasa. gov 
Session B I (continued) 

HVOF Thennal Spray Coating as 

an Alternative to Hard Chrome 

Plating on Military Aircraft 

&ure 0. .%rmdl Pval 

Rmmh Laboraroryl 

The Use of bn Vapor Deposited 

Aluminum (IVD) for the Space 

Shuttle Solid Rockt Booster 

Howad kvak. Bill he. Randy 

Raky (Unitd we Allime) 

3:30 - 

4:oopm 

3:45 pm Demonstration 

Session C I (Salon 2) 

Developments in 

Coating Removal Pnxresses 

Chair Mama Clark-lngram 

Marshau Flight Center 

Coating Remcual Technology Using 

of Cum Aerospace Applications 

Using the EnviroStrip@Dry 

Stripping Process 

DtnEs We, CHnerW? Dtake 

(ALN4/EnGmStrip Djvkion) 

Rem1 of Zirconia Thermal 

Barrier Coatings and MCrAlY Bond 

Coatings from Turbine Bbdes: A 

Chemical Stripping, Water Jet, and 

Salt Bath 

A. krivani, U. Bad, 6. Ballerini, 

D. Bonamhi (Univekty of Fime); 

M. fantini (Gatvaniica Pam); R. 

Grqwtri, S. laneili (University of 

Farma); G. RizI (Turbocoating 

S.p.A.) 

Intempq Depainting Study 

Man-& Clark-hgmm (Marshall 

Saxe Right Center) 

Evduation of Various Depainting 

Processes on Mechaniil Properties 

of 2024-T3 Aluminum Substrate 

Pmtm MI (Marshall Space 

Flight Gwter) 

Starch-Based Abn- A Review 

Comparison of Methods Based on 

Joint EPA/MSA/USAF 

Break --- Exhibits 

Robot Expo (Exhibit Area) 

Patriot J (DaimlerChrysler/Bob Jones High School. Athens, Alabama); 

Oscar (PRO-BOTS, Atlanta, Georgia) 

X- Traktor (MSFC/Lee High School, Huntsville, Alabama); 

Session C2 (Orchestra) 

Ceramic Matrix Composites 

Chak Mike Effinger 

Marshall +ace flight hter 

Concept for Determining the Life of 

Ceramic Matrix Composites Using 

Nondestructiw Chamterizat'm 

Tedrniqws 

Michael Effinger (Marshall Space 

Right Cented; gill €llinp. Tc& 

spohnhdz (Argonne National 

Lahratory); John Kmk 

(Southern Research lnstituie) 

Low Cost Ceramic Matrix 

bmposites 

GlQoration) 

hponents 

Witold K&, C he. K. T. 

Tw, J.C. With (MER 

Fabrication and Testing of Ceramic 

Matrix Composne Propulsion 

MW Etiinger, RG. Clinton. Jr.. 

Jay Dtnnis, Sandra Elam. Gary 

Gmge (Marshall Space Flight 

Cenrer); J. Doug Kk, Andy F&d. 

Martha Jaskowhk, kny Lang 

Rqnd fabrication of Monolithic 

Ceramic Rrts Rknfmed with 

Fibrous Mondiths for Aerospace 

bnj Vajdyanathan. 1. Walish, J. I. 

lmbardi. D. Dent, M. Rigali, M. 

5utaria (Advanced Cwamics 

(c;lpnn Reseafch Cmter) 

Apprlcations 

Resean-h. k.) 

jession C3 (Salon I B) 

Rapid Prototyping 

Chair Km Cooper 

Marshall Space Fight C-enttU 

1 Soli Freeform Fabrication of 

Continuous Fiber Reinforced 

Composites br Propulsion 

Applications 

Rani; Vaidyanathan, 1. Waiish. M. 

Fox. M. Kigali, M. hria 

(Aa'vanctd Ceramics Resea&, k.); 

1. W. GiHtyie. Jr.., S. Ya&& 

(Uniwrsy of DtJawar): M. Efiger 

(Marshall Space Right Cmtm} 

b An Example of Economic Vdue in 

Rapid Prototyping 

Uoh L. Hawre John R. Reagan, 

EhniF. &aumM, t-kdwt A. 

Lawrrnre, Jr. (Glenn &amh 

&tW) 

' High.Efficiency Mdithc 

Lightweight Aluminum Cast 

Structure 

Preliminary Component Integration 

Utilizing Rapid Pmtotyping 

Ken CLnaper (Matshall Space Fii&t 

&tu); Fat Salvail (UT Rpsearch 

Institute) 

Joh BdvkAt (NlJ-bst, lnc.) 

hion C4 (Salon I A) 

Innovative Materids Applications 

Chair MiM Pedley 

Johncon Space Cmter 

Multifunctional Carbon foams for 

Aerospace Applications 

Brian+. Lhm kbgm, Janus2 

fluchski(Ta&fm Rexh 

Iabtatory) 

LOX Compatibility of Composite 

Materials 

Tim Vaughn (Marshall !+ace Fiight 

Gnter) 

Low Density Monolithic Metal 

Honeycombs by Thennal Chemical 

Processing 

Jim Lee, Joe Mmn. Dave 

Mc~l. Tom Sanders (Gmgia 

kitufe of Terhndogyl 

Tmshab Materids seledion 

MiM Pedky (Johnson Space 

Gnter) 

Relax and enjoy hors d'ueuvres and other refreshments with our conference exhibitors and your colleagues. 

http:/ /ampet.msfc.nasa.gov 
Session AI (ordwstra) 

Engineering Evaluation of Solvent Substitutes 

Lockkl Martin Space Systems 

Chalr: Ralph L&Wf 

- Nonlbmmable. Nonaqueous Lw Atmospheric 

Impact. High Rrrtormance Cleaning Solvents 

Patrick M. Dhoogr. hhan S. Nimitz. 

Suzanne M. Glass. (Envirunnmtd Techdogy uf 

Educlltion Cmter) 

Ktntvh Kitamura, Masaaki Tstwki. and Stephen 

0. Stagliano (Asahi Glass) 

HFEs in the Aerospace Industry: A Logical 

Alternative to CFCs and Other Habgemted 

Cleaning Solwnts 

@avid A. Mroth (3M Company) 

Elimination of MEK and Lacquer Thinner in 

Department of Detense Painting Operations 

Joseph A. LWJS, Eric Lethe (hiand T~hnology 

Aempce Applications h AK-225 

lnwwrJt4 

12:00n - 

I :30 pm 

I : I 5 pm Demonstration 

Sgsion A2 (Salon I B) 

Advances in Materials Development 

Chair: John Gandkr 

The Boring Gnnpany 

Lightweight MultLLayer Structural Materials 

H. H Legner, W T. Laughlin (Physial Science, 

Scimcs); R. Singer (Ttxtron Systm) 

* Asbestos free Insulation Devdopmt for the 

Space Shuttle Solid Propellant Rocket Motor 

Lany P. Allmi (Thiokd Propulsbn Gmp) 

- Aerogel Pro@ts Ongoing in MSFC’s Engineering 

Directorate 

David hlar. hmeth Smith (Marshall Space 

Flight hter): Joel Pidy (Rem-ekw 

Polyt&nic Institute) 

Eiectroactive Polymers as Artificial Muscles - Reality and Challenges 

Yoseph Bar-Cohen (NDEAA Technologies) 

k,): v. l?i cnst/na. @. Marshal /Thmoph*l 

(RSRM) 

1 unch --- Exhibits 

Rapid Prototyping (Exhibit Area) 

Ken Cooper (Marshall Space Flight Center) 

SeSsiBI (Sdon IA) 

Elimination of Heavy Metds 

Chair bard bak 

United Space Alliance 

Laser Uadding/&ing as a 

Surfm Coating Alternative 

Rob Hull (Antm Gpnth); 

@ave Firis4 (Inorgaic Sptwalists); 

Matnitacturing solutions): John 

ErEc (AFRL/MLPJ) 

Testing of Envimnmentdly 

Preferable Aluminum 

Pretreatments and Coating 

Systems for Use on Space Shuttle 

Randy Raky (United Spacr 

Allim) 

Trivalent Chmium/OrganicaltyModifd Silicate Composite 

Coatings for Corrosion Protection 

of Aluminum Alloys 

Tammy hktde, Edwani 

Knobbe. Bin 5tesikovaa. Olga 

khtina (oldduma State 

University) 

chudc wood(G/o&?l 

wi RCcket Boosters (SRBS) 

&thlF ad)’TOf?. LtFzOok. 

(mtMmnextpJge,) 

Session B2 (Sdon I B) 

hnces in Materids Andysls and 

Testing Technique I 

Chair: Sam Wl 

Marshall +ace Flight Center 

High TemperatuR Material 

Mormance Testing Usmg 

Continuous Waw Cartwn Dioxide 

Laser5 

Timothy /ohm (Antm 

Therm0gr;phicNOndestr~aive 

Eduath of the Space Shuttle 

Main Engine Nozzle 

hmes L. Walker, Sad S. 

RusFA(I. ManhAy D. Laming. Paul 

Cadi (Mahll Space Flight 

htw) 

Vdidati of Shearography NE 

MetM on Space Shuttle, X-33. 

and klta IV Launch Mick 

John Newman (Laser TEhnohgy. 

w 

Thermogtyhic Analysis of 

Composite Cobonds on the X-33 

James L. Walker, Sad S. 

Wi, Matthtw D. Lansing 

(Marshall Space Flight btw) 

Gpmtim) 

i 6 for uestions and answers. 

Session A3 (Salon I A) 

Nationd Center for Advanced 

Manufacturing Workshop 

Chak John Vickm 

Mahll Space Flkht Center 

Owrview of the Nationd Center for Advanced 

Manufacturing (NCAM) 

John Vickm (Marshall Sm Flight bter) 

Implications for Aerospace Manufacturing 

Dale Thomas (Marshall Space Flight hter) 

pdrtnershi Expanding Education and Meeting 

Workforce Challenges 

James E. Swimfell, Richard Carpenter (Calhoun 

Community College); Donna C. 6ass (Abbama 

Industrial I3ev-t Training); William R. 

Reynolds (bbeing. Mta IV Qwatiuns) 

Composite Manubduring for Space Launch 

Vehiicles 

Donna Y. Knezekh {Lockkdhk~n Space 

Ahanced Engineering Environments - 

Education. Industry and Government 

systems) 

sgsion 63 (orchestra) 

Dedopments in Metals P~xresses I 

Chair: Am Bdsd 

LdMMartin Spe Systm 

Evaluation of Forces on the Welding 

Probe of the Automated RetractaMe 

Pin-Td (RPT) 

R. kffq Ding (Marshall Space 

Flight htw) 

Friction Stir Weld Mcdeling at 

MSFC: Kinematics 

Arthur C. b. Jr. (Matshall 

Spxe Flight htw) 

= Aluminum Lithium Alloy 2 195 

Fusion Wdmg Imprwements with 

New Filler Wire 

Gerry winan (LdMMartin 

!+ace Systems); Carolyn Russd/ 

(Marshall Space Flight htw) 

Session B4 (Salon 2) 

Non-Metal~ I 

Chair: Teny Dillard 

Thiokd PropUrsion Gmp 

Fabrication of Compostte 

Combustion Chamber/Nozzle for 

Fastrac Engine 

Timothy Lame, R. Bedwats, S. 

Budingame. W Petm, M. Prince, 

M. Suits. S. iiliery (Marshall Space 

Flight Cenrer): L. Bum, M. 

Kmarh. K. Rolwrts (Thiokd 

Propula;on Gmp) 

La~CaposneStructurrs 

ProcesSng Technologies For 

ReusaMeLaunchvehides 

RG. Clinton. Jr., John ti. Vkkers, 

William M. MoMahon. et. d., 

(-1 +ae Flight hter); 

Norman J. Johnson (Langle y 

hposite, Gyopenic. Conformal. 

Insulated Tank (CENT) Materials 

and Processing Methoddogies 

MW P.Kovach. 1. Keith 

Gmp): Wlliam M. Mh, 

kffi L. Finckmr (Marshall 

!+we Flight Center) 

ResafCh hter) 

cMmonBulkhead,AeKlgelROberts(Thi0kdP~~ 

http://ampet.msfc.nasa.gov 
FOURTH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTALTECHNOLOGY 

SEPTEMBER IS, 2000 

AMPET Conference Venues 

Von Braun Center 

(Conference Venue) 

Huntsville Museum of Art 

(Welcoming Reception) 

Hilton Huntsville 0 (Lodging and Tour Start) 

1:OO pm 

5:OO pm 

Buses depart from the Hilton Huntsville 

US Citizens lour 

Boeing Delta IV Plant 

MSFC Productivity Enhancement Complex 

MSFC International Space Station Manufacturing Facility 

International Guests lour 

US Space and Rocket Center 

(/MAX theater, guided tour, bus 

tour of MSFC) 

Buses return to the Hilton Huntsville 

Enjoy an evening of art and southern hospitality at the AMPET Welcoming Reception in the elegant Great Hall 

of the Huntsville Museum of Art, overlooking Big Spring Park. This nationally accredited museum is the premier 

visual arts center in North Alabama and Southern Tennessee. In its seven spacious galleries, visitors enjoy a wide 

array of exhibitions, prestigious traveling exhibitions, works by nationally and regionally acclaimed contemporary artists, and shows featuring some of the 2,300 works in the Museum’s permanent collection. 

SEPTEMBER 19, 2000 

9:15 - 1O:oOam 

9:30 am 

Conference Welcome Dr. Ann F. Whitaker 

Deputy Director, Science Directorate 

NASA/MSFC 

Keynote Addresses 

Advanced Space Flight and 

Environmental Concerns 

Dr. Ann F. Whitaker 

Deputy Director, Science Directorate 

NASA/MSFC 

Science and Technology - 

Then and Now 

Dr. Owen K. Garriott 

NASA Astronaut, Retired 

Interim Director, National Space Science and Technology Center 

Materials Advancements in 

Aerospace 

Dr. Charles E. Browning 

Director, Materials and Manufacturing Directorate 

Air Force Materiel Command 

Wright-Patterson Air Force Base 

Break - Exhibit A rea 

Foster area (North Hall Gallery) opens for viewing. 

http: / /ampet. msfc. nasa. gov 
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Nonflammable, Nonaqueous, Low Atmospheric Impact, High Performance Cleaning 

Solvents 

Patrick M. Dhooge, Suzanne M. Glass, and Jonathan S. Nimitz 

Environmental Technology and Education Center (ETEC) 

4500-B Hawkins St. NE 

Albuquerque, NM 87 109-45 17 

Phone: (505) 345-2707 

http://www .etec-nni.com 

pdhooge - @ e tec -nm .corn jnimitz@etec-nm.com 

INTRODUCTION 

For many years, chlorofluorocarbon (CFC) and chlorocarbon solvents have played an 

important part in aerospace operations. These solvents found extensive use as cleaning and 

analysis [EPA] solvents in precision and critical cleaning. However, CFCs and chlorocarbon 

solvents have deleterious effects on the ozone layer, are relatively strong greenhouse gases, and 

some are suspect or known carcinogens. Because of their ozone-depletion potential (ODP), the 

Montreal Protocol and its amendments, as well as other environmental regulations, have resulted 

in the phaseout of CFC-113 and 1,1,1 -trichloroethane (TCA). Although alternatives have been 

recommended, they do not perform as well as the original solvents. In addition, some analyses, 

such as the infrared analysis of extracted hydrocarbons, cannot be performed with the substitute 

solvents that contain C-H bonds. 

CFC-I 13 solvent has been used for many critical aerospace applications. CFC-I 13, also 

known as Freon’’ TF, has been used extensively in NASA’s cleaning facilities for precision and 

critical cleaning, in particular the final rinsing in Class 100 areas, with gas chromatography 

analysis of rinse residue. While some cleaning can be accomplished by other processes, there are 

certain critical applications where CFC-113 or a similar solvent is highly cost-effective and 

ensures safety. Oxygen system components are one example where a solvent compatible with 

oxygen and capable of removing fluorocarbon grease is needed. Electronic components and 

precision mechanical components can also be damaged by aggressive cleaning solvents. 

A number of alternative cleaning processes and solvents have been promoted in the last 

few years. 

Supercritical carbon dioxide can provide excellent cleaning, but has the drawbacks that 

the high-pressure systems used are expensive and limited in size. The cleanliness obtained with 

supercritical CO;! depends strongly on the pressure and temperature of the system, so these 

parameters must be closely controlled. In addition, the rapid temperature and pressure changes 

may damage structures and affect components. 

Many conventional solvents (e.g., hydrocarbons) are effective cleaners but are 

flammable, not compatible with oxygen, and require special precautions. 

Ethyl lactate has been developed as an effective, zero ODP, low GWP, biodegradable, 

low toxicity, solvent that can be made from renewable resources. However, its boiling point and 
other physical properties are not suitable for cleaning many components and assemblies, as it 

evaporates too slowly and can become entrapped in small spaces. In addition, it is not compatible 

with oxygen. 

Isopropyl alcohol (IPA) can be used in some cleaning, but engineering and safety 

measures are needed to minimize flammability risk. As a result, systems designed for IPA are 

expensive (on the order of $lOO,OOO). In addition, large volumes of IPA are often needed as 

final rinse and dry, generating large volumes of solvent waste. 

Hydrofluorocarbons (HFCs) are nonflammable, have zero ODP and low toxicity, but they 

also have poor solvency and moderately high GWP. Some blends containing HFCs are under 

investigation. 

Hydrofluoroethers (HFEs) have recently been introduced by 3M as cleaning solvents. 

HFEs possess the attractive properties of some solvency for oils and greases, low toxicity, 

reasonable cost, no ozone depletion, and modest global warming. However, their performance 

for many applications has had to be augmented by addition of better solvents such as 

dichloroethylene, which puts them back in the chlorinated solvent category. 

One alternative solvent that is being investigated heavily and used in some applications is 

I -bromopropane (EnSolv@ and similar products). This solvent has good cleaning ability, 

relatively fast evaporation, is not flammable, and can be used in some precision cleaning 

applications. However, it is not compatible with oxygen, and there have been some reports of 

toxicity from exposure to 1 -bromopropane. Haloalkanes also tend to be carcinogens. 

Volatile methyl siloxane (VMS ) solvents have been developed by Dow Coming. These 

compounds show promise as nonflammable (but combustible) cleaning solvents with good 

environmental properties. However, they are not compatible with oxygen and have relatively 

high boiling points and low volatilities, thus requiring longer drying times. 

Plasma cleaning is being developed as a solvent-less process, but it requires sophisticated 

equipment and is not suitable for all materials. 

lodofluorocarbon (IFC) Solvents 

Iodofluorocarbons (IFCs) were identified by Jon Nimitz and Lance Lankford as 

potentially attractive nonflammable, nonaqueous solvents for replacement of CFC and 

chlorocarbon solvents. The 3-carbon to 6-carbon IFCs containing one iodine atom have low 

boiling points. high volatilities, low viscosities, and low surface tension, which make them 

attractive candidates as alternative solvents. In addition, they have essentially zero ODP 

(<0.0025), extremely low global warming potential (GWP), acceptable toxicity, and good 

thermal stability. They are chemically similar enough to chlorofluorocarbon and chlorocarbon 

solvents that they also promised to have good soil removal abilities. 

Although IFC solvents appeared to have much promise, there were a number of issues. 

There were little or no toxicity, stability, biodegradability, and compatibility data available on 

the compounds. For oxygen system cleaning, compatibility with liquid oxygen needed to be 
determined. Atmospheric lifetime had to be calculated to obtain a good estimate of ODP and 

GWP. Cleaning abilities compared to CFC- 1 13 and other solvents had to be established, as well 

as ability to purify and reuse the IFC solvent. Perhaps most importantly, since the IFCs are not 

bulk commercial products, a low cost synthetic route had to be identified. 

From 1995 to 1999, in projects sponsored by the Air Force Research Laboratory and 

NASA, ETEC developed two new solvents, Ikon@ Solvent P and Ikon@ Solvent M, based on 

iodofluorocarbons (IFCs). The Air Force's interest in new solvents was for replacement of CFC1 13 in mission-critical aircraft maintenance operations. NASA's interest in the solvents resulted 

from difficulties replacing CFC- 1 13 in oxygen system cleaning. 

RESULTS AND DISCUSSION 

Cleaning Ability and Recovery for Reuse 

A preliminary series of cleaning tests were performed with the three-carbon, four-carbon, 

and six-carbon IFCs. Testing was performed based on a procedure developed at Sandia National 

Laboratories. One by three inch tared coupons of substrate material were intentionally soiled 

with one of six representative soils: the three perfluorinated greases Braycote" 601 EF, Krytox' 

240, and Tribolube" 16; Amoco Rykon' Grease No. 2EP (a hydrocarbon grease); Dow-Corning 

DC-55M (a silicone grease); and Royco 782 Superclean Hydraulic Fluid MIL-H-83282 (a fireresistant hydraulic fluid containing phosphate esters). Soiling levels were from 1 .O to 5.0 g/ft'. 

Each coupon was weighed to measure the amount of soil, then cleaned, air dried, and reweighed 

to determine soil removal effectiveness. Figure 1 shows some of the results from this testing. 

Perfluoro-n-butyl iodide ( CF~CF~CFZCF~I, 1 -CSFgI, Ikon@ Solvent P), specified hereafter in this 

paper as PFBI, was identified as the most attractive cleaning solvent from this group, and as can 

be seen it removes perfluorinated greases significantly faster than CFC- 1 13. 

PERFLUORINATED GREASE 

; 100 

CT 60 

> 

w 

80 

$ 40 

20 8 

0 

0.0 2.0 4.0 6.0 

TIME (MINS) 

+TCA 

-.clTCE 

CFC-113 

mw'b 1 -C3F7l 

+k 1 -C4F91 

..IC. I -C6F13l 

- 

Figure 1. Removal of Pertluorinated Grease by Selected Solvents 
Continued cleaning tests examined the ability of the IFC solvents and CFC- 1 13 to 

remove a soil when the solvent was already saturated with that soil. Braycote“ 601, Rykon ’ 

Grease No. 2, and Dow-Corning DC-55M were chosen as representative soils. The results of 

these tests were even more encouraging than the tests with clean solvents. As shown in Figure 2, 

Ikon Solvent P (PFBI) consistently removed the three soils from 316 stainless steel significantly 

faster than CFC- I 13, indicating superior cleaning ability over extended use applications. 

100 

90 

SO 

70 

60 

50 

40 

30 

20 

10 

0 

OPercent Soil Removed aner 1 lshute CFC-113 

BPercent Soil Removed after I minute Ikon Solvent P 

I 

Perfluorinated Grease Hydrocarbon Grease Silicone Grease 

Figure 2. Soil Removal Ability of Soil-Saturated CFC-113 and Soil-Saturated PFBI 

Upon determination of our best replacement solvent candidate, it was considered 

worthwhile to explore testing ability to recover the solvent to reduce its cost of use and the 

amount of waste solvent generated. This study was performed at the Air Force Research 

LaboratoryMLBT. They found that used or “dirty” PFBI could easily be distilled to a purity 

equal to that of new or unused solvent. At least 85-90% of the solvent was recoverable. 

AFRLMLBT concluded that PFBI could be recovered easily and economically, greatly reducing 

the cost of using the solvent and the amount of waste solvent generated. 

Compatibility and Stability 

Compatibility tests consisted immersing selected materials in PFBI for 10 days at room 

temperature. 

Of nineteen polymers and elastomers tested in this manner for compatibility, only Aflas, 

silicone rubber, and urethane were found to be incompatible. Compatible polymers included 

polyacrylic, cyanate ester, graphite/epoxy composite, nylon, phenolic, polyimide, poly (vinyl 
chloride) and Teflon. Compatible elastomers included Buna-N, neoprene, EPDM, fluorosilicone, 

and Viton. 

Compatibility tests were conducted with aluminum alloys 2024, 5052, 6061, and 7075T6: 

stainless steels 303 and 4 16; titanium; mild steel; cast iron; magnesium; copper; brass; bronze: 

acid-core solder; plumbing solder; and rosin core solder. PFBI was completely compatible with 

all metals tested except mild steel. Mild steel showed significant oxidation (rust), which was 

likely due to air and moisture that were not rigorously excluded, because there is no reaction 

between iron and PFBI alone that could have formed iron oxide. At the temperatures expected in 

cleaning operations, PFBI is also compatible with other common solvents, water, and adsorbents. 

One indication of the relatively high stability of PFBI is its compatibility with liquid 

oxygen. This is a harsh test for any solvent, and almost all solvents will react with oxygen under 

these test conditions. In this test, a sample of the solvent is frozen in a pool of liquid oxygen and 

struck with a striker to attempt to initiate reaction. CFC- 1 13 passes this test at 72 ft-lbs striking 

force. Only two out of seventeen samples of PFBI reacted at 72 ft-lbs, and none out of 20 

samples at 65 ft-lbs. Thus, PFBI appears to be only slightly more reactive toward oxidation than 

CFC- 113. 

The autogenous ignition temperature of PFBI in 100% oxygen at 13.8 Mpa (2000 psia) 

was measured as 17 1 - 175°C. This test also reveals excellent stability for PFBI. In fact, PFBI is 

a known combustion suppressant. 

Suppliers package, ship, and store PFBI without any special precautions. During our 

cleaning tests, PFBI was re-purified by distillation and reused many times without evidence of 

significant decomposition. PFBI often comes from the supplier with a slight pink color from free 

iodine in solution, and left out in the sun or under fluorescent lights for an extended period of 

time it will always develop a pink color from free iodine. The free iodine is a photolysis product 

from exposure of the solvent to UV light. The amount of iodine produced under these conditions 

is very small, at most several parts per million, and can easily be removed from the solvent with 

activated carbon. 

Atmospheric Lifetime, ODP, and GWP 

The estimated low atmospheric impact of the IFCs is a result of their susceptibility to 

short wavelength ultraviolet light. The carbon-iodine bond in these compounds is weak enough 

that UV wavelength photons in sunlight can break it. Breaking the C-I bond begins a 

decomposition chain that proceeds completely to CO2, HF, and HI, as the fluorinated free radical 

from the C-I bond breakage reacts with water to form fluorinated alcohols that are highly 

unstable and quickly decompose. 

Other than their susceptibility to photolysis, normal IFCs containing one iodine atom are 

stable because the fluorine atoms withdraw electron density from the iodine atom and make it 

much less reactive. The fluorines also block back-side attack on the iodinated carbon atom. 

The atmospheric lifetimes, ODPs, and GWPs of the three-carbon, four-carbon, and sixcarbon IFCs were determined by Dr. Don Wuebbles at the Department of Atmospheric Sciences 
at the University of Illinois (Urbana-Champaign). Dr. Wuebbles is one of the world’s foremost 

researchers on ODP and GWP. He concluded that the atmospheric lifetimes for these compounds 

are approximately 2 days. This is extremely short compared to most fluorinated chemicals, 

which have lifetimes ranging from years to centuries. He concludes that the ODPs of FICs are 

less than or equal to 0.0025, “much less than is of concern within the U.S. and international 

guidelines.” The GWPs are also extremely small, less than 6 relative to COz for the 20 year time 

horizon and less than 2 for the 100 and 500 year time horizons. Dr. Wuebbles concluded that 

“these results imply essentially a negligible effect on future climate from use of 1 -C3F71, 1 -C&I, 

and 1 -C$J~I.” 

Toxicity and Biodegradability 

Toxicity studies on PFBI were conducted by Huntingdon Life Sciences (IUS). 

PFBI was found non-mutagenic in the Ames test and non-clastogenic in the human 

lymphocyte chromosome aberration test. 

Twenty-eight day rat subchronic inhalation (6 hrs per day) exposure tests were 

performed. Results showed somewhat elevated thyroid hormone levels at 100 ppm exposure; 

elevated thyroid hormone, triglyceride, and iodide levels in the I ,OOO and 10,000 ppm test 

groups; and some physical effects in the males (low weight and enlarged livers) at 10,000 ppm 

exposure. A medical expert in thyroid chemistry who has reviewed inhalation test data for the 

related compound CF3I has noted that rats are much more sensitive to iodine levels than humans, 

and concluded that humans should suffer no effects at the recommended average 8-hour 

exposure level (AEL) of 150 ppmv for CFJ (Capen). It cannot be stated positively that the same 

reasoning can be applied to the IFC solvents, but it seems likely. 

Cardiac sensitization inhalation tests were performed on PFBI. Many gaseous or volatile 

hydrocarbons and halocarbons sensitize animal hearts to adrenalin through the inhalation 

pathway. The possibility of death from heart fibrillation after exposure to a halocarbon was first 

realized in the 1960s. A standard test was developed at that time to measure the relative cardiac 

sensitization of compounds. The test uses Beagle dogs that are injected with enough 

ephinephrine (adrenalin) to be barely under the amount that would cause that dogs’ heart to go 

into fibrillation (this dosage is determined for each individual dog in the test group). After 

injection, the dogs ,\le exposed to concentrations of the test compound in air. The minimum 

amount of the compound found to induce heart irregularities is the LOAEL, or Lowest 

Observable Affect Exposure Limit. The NOAEL, or No Observable Affect Exposure Limit, is 

the maximum concentration the dog can be exposed to with no affect. This test is quite rigorous, 

since the dogs are already just below the point of fibrillation due to the very high ephinephrine 

level, and the test was not originally intended to established exposure limits. It has been 

estimated that the ephinephrine levels used in this test may be 100 times or more higher than 

would be seen in even a very frightened test subject (Vinegar). The cardiac sensitization test’s 

relevance is being questioned, but it remains the standard at this time. PFBI had a No Observable 

Adverse Effects Limit (NOAEL) of 0.4% (4,000 pprn), and a Low Observable Adverse Effects 

Limit (LOAEL) of 0.6% (6,000 ppm) in this test. PFBI’s NOAEL is significantly higher than 

that of TCA (i.e., it is significantly less cardiac sensitizing than TCA), and only slightly lower 

than that of trichloroethylene (TCE). Figure 3 shows the comparison graphically. 
Acute Toxicity - Cardiac Sensitization - Dog 

12000 h 

E 2 10000 Y 

8000 

6000 

3 

v1 

w 

v1 

6 4000 

f 2000 

3 

- 

0 

Ea LOAEL 

6,000 

5,000 

I Ikon Solvent P 1,1,1-Trichbroethane Trichloroethylene 

Figure 3. Comparison of Cardiac Sensitization NOAELS and LOAELS for Solvents 

The aquatic toxicity of PFBI is considerably greater than for common chlorinated 

solvents. The 96 hour Fathead minnow LC50 was 2.3 ppm by weight for PFBI, compared to 40 

ppm by weight for TCE and 53 ppm by weight for TCA. 

Biodegradability testing was conducted by HLS in accordance with EEC Methods for 

Determination of Ecotoxicity Annex to Directive 92/69/EEC (O.J. No. L383A, 29.12.92) Part C, 

Method 4-E “Determination of Ready Biodegradability Closed Bottle Test” and the OECD 

Guideline for Testing of Chemicals No. 30 ID “Ready Biodegradability: Closed Bottle Test.” 

Over 28 days, a mean PFBI concentration of 59 mg/L showed maximum oxygen depletion in the 

test vessels equivalent to 9% biodegradation, relative to the theoretical oxygen demand. 

Therefore, PFBI cannot be termed readily biodegradable as the ‘pass level’ of 60% was not 

attained. However, PFBI was not found to be inhibitory to activated sewage sludge bacteria 

under the conditions of this test. 

Regulatory Status 

PFBI is not a RCRA listed substance, but spent solvents are typically RCRA listed. The 

value of PFBI and its recoverability make it highly unlikely that spent liquid PFBI would be 

disposed of as hazardous waste. 

For regulatory purposes, a chemical is classified as a volatile organic compound (VOC) 

if, when released into the air in the presence of sunlight and other common urban air 

contaminants, its breakdown results in production of higher ozone levels than an equivalent 

amount of ethane released (the standard). VOC testing on PFBI was conducted by the 

Environmental Science and Engineering Department at the University of North Carolina at 

Chapel Hill under the direction of Dr. Harvey Jeffries. The test is conducted on a summer day 

with high solar irradiance. Shortly before dawn a synthetic mixture simulating urban smog is 

injected into both of two large, clear plastic chambers, followed by samples of ethane into one 

chamber and the test substance into the other. The temperature, solar irradiance, and levels of 

ozone and nitrogen oxides are monitored until after sunset (about 13-hours total for the test). 

PFBI created more ozone than the ethane, and so would probably not be VOC-exempt, although 

there is an exclusion for point sources below a certain level of emissions per year. 
The U.S. Environmental Protection Agency (EPA)’s Significant New Alternatives Policy 

(SNAP) program approves replacements for ozone-depleting substances. An application for 

Ikon’ Solvent P has been submitted to EPA. 

Occupational Exposure Assessment 

Waldemar S. Nelson and Company, Inc. (Nelson) performed an occupational exposure 

assessment on PFBI. PFBI was compared to trichloroethylene, 1,1, I -trichloroethane, 1,1,2- 

trichloroethane, and CFC- 1 13 using existing data to assess its relative occupational exposure. 

Nelson concluded that worker exposure to PFBI needed to be limited to 73 ppmv or less at 

present to freely substitute PFBI for other solvent chemicals without a potential increased health 

risk. This assumed the worst case (Le., maximum continuous exposure level at the TLV) for the 

solvent, and it was Nelson’s opinion that this assumption exaggerated anticipated exposure levels 

in a modern cleaning facility. Nelson stated, “It is unlikely that the exposure levels at a modern 

degreasing facility would approach the TLV for the solvent in use. If the real exposure level was 

far below the TLV, it would be far easier to achieve a level of comfort with the anticipated 

exposure to IKON-P.” Nelson concluded that site-specific exposure information would be 

needed to evaluate this properly. Personnel protection equipment Nelson recommended for PFBI 

was similar to that for I, 1,1 -trichloroethane and trichloroethylene. 

Synthesis, Price, and Availability of the IFC Solvent 

One of the greatest barriers to widespread use of IFC-based solvents is their current high 

cost. At present they are still essentially research chemicals, although PFBI’s price continues to 

decrease and is now at about $60/lb versus over $200/lb several years ago. Successful 

introduction will require manufacturing PFBI at a sufficiently low cost that its selling price will 

be competitive with other alternative solvents. 

The current method used for manufacturing PFBI is not disclosed in the literature, but we 

know from published patents and personal communications that PFBI is now made from 

tetrafluoroethylene. Tetrafluoroethylene (CF?=CF?) is a relatively inexpensive monomer used in 

manufacturing Teflon (a polymer of tetrafluoroethylene). Appropriate reactions of 

tetrafluoroethylene yield pentaiodoethane and higher even-carbon homologs, as shown in 

Reactions [ 11 and [2]. 

CF~CFZI + CF?=CFz 1 -C4FgI + 1 -C$,?I + higher homologs PI 

ETEC personnel identified and evaluated a number of alternative synthetic routes, 

including the Hunsdiecker reaction (iodination with decarboxylation of a fluorinated carboxylic 

acid), and alternative gas-phase reactions of several types. It was found that a modification of the 

gas-phase synthesis of PFBI from tetrafluoroethylene was by far the least expensive synthetic 

method. The yield reported in the literature is about 90% PFBI. ETEC’s chemical engineering 

personnel prepared a conceptual design for a facility based on this process, producing 5 million 

pounds of PFBI per year. Equipment costs, materials costs, and operating costs were estimated 

from the design. Iodine is the principal cost driver in the synthesis. At the present bulk iodine 

cost of about $22/kg, the estimated cost of PFBI production is $18/kg. Assuming a markup of 

25% by the manufacturer, 30% by the distributor, and a royalty of about $2/kg, this gives a retail 

selling price for PFBI of about $3 lkg. This price is competitive with other fluorinated solvents 
such as HFE-7 100, and PFBI is a much more effective cleaning solvent than HFE-7 100. 

Assuming bulk iodine price drops back to near its historic level, say $1 Ikg, PFBI could be 

produced for an estimated $15/kg. Under the same assumptions as above, the retail price of PFBI 

would be about $26/kg, significantly less than HFE-7 100. 

The available data indicate that iodine supply for producing PFBI and other ECs as 

replacements for CFCs, HCFCs, and halons will not be a problem. Present world production of 

iodine is approximately I5 million kilograms per year. Currently, iodine prices are near a modern 

all time high due to China's decision several years ago to iodize their table salt. This decision 

caught iodine producers by surprise and raised iodine prices. New iodine production facilities are 

being built. Iodine price should return closer to its historic level of about $1 1 kg. Proven 

worldwide reserves of iodine recoverable at less than $15kg are about 6.4 billion kilograms 

(Bureau of Mines). In addition, the oceans contain an estimated 34.5 billion kilograms of iodine, 

part of which can be recovered directly during extraction of chlorine, bromine, or magnesium 

from seawater, or indirectly by collecting and processing kelp. Seaweeds of the Laminaria family 

accumulate up to 0.45% iodine on a dry weight basis; before 1959 seaweed represented a major 

source of iodine. At least one company in China is now producing iodine extracted from seaweed 

at a quoted price of $23.50/kg. The price of iodine recovered from seaweed should decrease as 

production volume increases. Cultivation and harvesting of seaweed for iodine and food products 

such as alginates can create an alternative source of income for coastal peoples, reducing 

economic pressure to over-fish and providing marine habitat. 

CONCLUSIONS 

If PFBI is produced in quantity at a reasonable cost, it should be an effective substitute 

for CFC-113 and chlorinated solvents in a variety of critical cleaning and analytical applications. 

ACKNOWLEDGEMENTS 

The funding for this work was provided by the U.S. Air Force Research 

LaboratoryMLBT and NASA Kennedy Space Center. We would like to thank Dr. Edward 

Snyder of Wright Laboratories and Dr. Jamie Palou of NASA KSC for their valuable technical 

support during the efforts. We would also like to acknowledge the contribution of Ms. Kirby 

Olson, who performed many of the cleaning tests. 

REFERENCES 

Bureau of Mines, Mineral Commodity Summaries 1993, U.S. Department of the Interior, Washington, 

Capen, C. C., Letter report to S. Skaggs, Pacific Scientific, Re: Report "90-Day Nose-Only Inhalation 

Toxicology Study of Trifluoroiodomethane (CF3I) to Male and Female Fischer 344 Rats," of study 

conducted by Mantech Environmental Technology, Inc., February 12, 1996. 

EPA, Method 41 3.1 in Methods for Chemical Analysis of Water and Wastes (EPA-600/4-79-020) and 

also Method 5520B in Standard Methods for The Examination of Water and Wastewater. 18" Edition. 

DC, 1993, pp. 86-87. 
Aerospace Applications for AK-225 

Kenroh Kitamura, Masaaki Tsuzaki and Stephen Stagliano" 

Technology and Process Development Center 

Performance Chemicals General Division 

Asahi Glass Co., Ltd. 

10. Goikaigan, Ichihara-shi. Chiba 290-8566, JAPAN 

Phone: +8 1-436-23-3 15 1, Fax: +8 1-436-23-3 164 

* AGA Chemicals, Inc. 

220 1 Water Ridge Parkway, Suite 400, Charlotte, NC 282 17 

Phone: 704-357-363 1, Fax: 704-357-6308 

1. Introduction 

HCFC-225 products are environmentally sensible alternatives in a variety of applications to 

CFC-113, perfluorocarbons (PFCs) and other hydrochlorofluorocarbons with high ODP values 

such as HCFC-14lb. Many azeotrope-like mixtures and blends of AK-225 (a mixture of two 

isomers, HCFC-225ca ( CF3CF2CHCI,) and HCFC-225cb (CCIF2CF2CHC1F)) and AK-225G 

(HCFC-225cb) have been commercialized by Asahi Glass'.''. These HCFC-225 products are 

very similar to CFC-I 13 and its mixtures in physical properties, material compatibilities, and 

cleaning performance and are widely used in precision cleaning, electronics cleaning and a carrier 

solvent of fluorinated lubricants and silicones. 

HCFC-225 products are thermally stable and non-flammable. They have substantially lower 

c global warming potential (GWP) than PFCs and hydrofluorocarbons and an extremely low ozone 

depletion potential (ODP). AK-225 and most of HCFC-225 products are recoverable by 

distillation with no decomposition. 

An azeotrope-like mixture of AK-225, ethanol and stabilizers (called AK-225AES) is 

suitable for many defluxing applications. The mixture of AK-225, ethanol, hydrocarbon and 

stabilizers (AK-225T) that provides increased solvency was developed to solve a white residue 

problem which occasionally forms on printed circuit boards cleaned with AK-225AES". 

A blend of AK-225 and a surfactant (AK-225DH) for displacement drying after aqueous 
cleaning and other processes using water was also developed. A few plastics such as acrylic resin 

and stressed polycarbonate may crack with AK-225. AK-225FPL, a mixture of AK-225 and a 

fluorinated solvent, was specifically developed for these plastic cleaning applications. 

In this paper, fundamental properties and material compatibility of HCFC-225 products and 

their applications for aerospace related industries such as bearings, precision parts and PCBs will 

be discussed. Typical cleaning procedures of HCFC-225 products, the toxicological data and the 

status of regulations will be also described. 

2. Fundamental Properties of HCFC-225 Products 

Physical properties of HCFC-225 products are shown in Table 1 and 2. The boiling point, 

surface tension, KB value and latent heat of vaporization are critical properties for cleaning 

agents. To clean parts without raising their temperature to the point where the temperature 

sensitive materials are affected is of utmost importance. A boiling point in the range from 40 to 

60 "C is suitable. A low surface tension enables a cleaning agent to penetrate into narrow gaps. 

KB value shows the solvency of a solvent. KB value around 30-40 shows a selective solvency to 

remove soils such as oil, grease and dirt without damage to materials. Smaller latent heat of 

vaporization results in less energy consumption for vaporization of a solvent and easier drying. 

HCFC-225 products have similar properties to those of CFC-113. 

Table 3 shows the effect of AK-225 and CFC-113 on 20 kinds of plastics under typical 

cleaning conditions (at the boiling point for five minutes). The compatibilities of AK-225 are 

similar to those of CFC-I 13 except for acrylic resin. There are some cases where AK-225 shows 

cracking in parts made of polycarbonate that is caused by the residual stress from an injection 

molding process. Although some kinds of ABS resins are affected by AK-225, most ABS resins 

are compatible as shown in Table 3. AK-225FPL was developed to solve this issue. It is 

compatible with acrylic resin, stressed polycarbonate and ABS resin. Concerning AK-225G, the 

compatibilities are almost identical to those of AK-225. 

The effects of AK-225 and CFC-113 on elastomers under boiling point exposure conditions 

for three days are shown in Table 4. The effects of AK-225 are slightly stronger than those of 

CFC-113. Gaskets and/or seals used in cleaning equipment should be made of 

polytetrafluoroethylene, EPDM or chloroprene. Mechanical pump seals in solvent recirculation 

pumps should be polytetrafluoroethylene. Sealless pumps are ideal. 
AK-225 products are compatible with common metals. 

Material compatibility can be affected by variations in material manufacturing and it is 

advisable to recheck critical components under use conditions before a final commitment is made 

to AK-225 products. 

3. Applications of HCFC-225 Products in Precision Cleaning 

AK-225 and AK-225G are mainly used in precision cleaning applications. Its cleaning 

perforniance is very similar to that of CFC-113. Cleaning procedures consist of immersing a work 

load into a warm solvent, rinsing or spraying with a cool solvent and drying in a solvent vapor. 

Figures 1 and 2 show the procedure in typical cleaning equipment. 

AK-225 and AK-225G are applied for degreasing and dust removing of precision parts such 

as coils, relays, connectors, bearings, rocket engines and so on. These parts usually must avoid 

contact with water and they cannot be easily dried with aqueous, semi-aqueous and hydrocarbon 

cleaning systems because of their minute and complicated shapes. 

Parts for medical equipment which are made of plastics are cleaned well with AK-225, AK2256 or AK-225FPL. The cleaning of the parts is difficult with other solvents due to the 

compatibility of plastics and requirement of high cleanliness. 

Miniature bearings are precision parts requiring size accuracy and high reliability. In the 

manufacturing process, various processing oils are used for cutting and polishing. After 

assembling the bearings, the oils should be cleaned completely and an anti-rust agent would be 

administered simultaneously. AK-225 is used for cleaning and coating of anti-rust agents. The 

bearings are immersed in AK-225 to completely remove oils. During this process ultrasonic 

oscillation is sometimes used. They are then immersed in AK-225 and a few percent anti-rust 

agent solution to coat the surface. 

AK-225 is also used to remove a fluorinated grease on bearings for maintenance cleaning. 

Other cleaning agents including HCFC-141 b cannot dissolve the grease. 

AK-225 and AK-225G are nonflammable and stable solvents and are compatible with liquid 

oxygen. It is used to manufacture rocket parts and manned spacecraft. In the steel manufacturing 

industry, AK-225 is used for maintenance of tubing, containers, valves, gauges and so on. 
Systems using liquid oxygen should be cleaned completely. If a small amount of organic 

contamination remains on the surface, the liquid oxygen can easily ignite because of the strong 

oxidizing properties of oxygen that supports combustion. 

Parts made of ceramic such as IC packages and parts made of sintered metal have very 

porous surfaces. It is difficult to clean them with an aqueous cleaning process due to the hgh 

surface tension of the rinse water. AK-225 has been adopted to remove soils on the their surface 

because of its very low surface tension, low viscosity, low latent heat of vaporization and high 

relative evaporation rate. 

4. Applications of HCFC-225 Products in Electronics Cleaning 

High reliability and durability are required for printed circuit boards (PCBs) installed in 

automobiles and other high technology equipment including aerospace equipment. Therefore, 

many are usually coated by resins. The manufacturing process of the PCBs consists of soldering 

electronic devices, cleaning and coating. It is necessary to clean them in a short time because of 

the huge number of PCBs for automobiles that are produced. 

There are many manufacturers using AK-225AES for defluxing these PCBs. Most of them 

use fluxes and solder pastes developed for AK-225AES to shorten cleaning time and improve 

cleaning efficiency. 

The cleaning procedure of AK-225AES is the same as that of AK-225 previously described. 

Usually, tact time for AK-225AES is shorter than that for AK-225. These customers do not 

clean all PCBs that had cleaned with CFC-113 several years ago. They evaluate the necessity of 

each cleaning application and use AK-225AES only in applications where it is essential. They 

also use AK-225AES with recovery and/or distillation equipment to reduce the consumption and 

solvent emission. 

AK-225AES is also used for the defluxing of flexible circuits for printers, hard disk dives and 

so on. It is difficult to deflwc them with aqueous and semi-aqueous cleaners, because flexible 

circuits are made of polyimide that is not compatible with alkaline and easily absorbs water. 

Some fluxes and solder pastes for CFC-113 cause white residue on PCBs when the boards 

are cleaned with AK-225AES. AK-225T has developed to solve the problem. AK-225T can be 

used for removing most fluxes and solder pastes on PCBs. 
5. Other Applications of HCFC-225 Products 

AK-225 is used for rehgeration cycle cleaning where CFC-11 was used. It has also been 

adopted to verify cleanliness after cleaning in this application as well as others. 

AK-225 is used as carrier solvents for silicones which is coated on needles of syringes and of 

fluorinated lubricants which is coated on hard disks. It is also used as a solvent in chemical 

reactions. 

Aqueous or semi-aqueous cleaning is widely used to remove soils from parts. There are 

many cases that the drying of parts is difficult or may be the rate-determining step. Ak-225DH is 

a displacement drying system that can resolve this issue. AK225DH is used in a specially 

desigped vapor degreaser with three or more sumps as shown in Figure 3. The procedure is as 

follows: wet parts are immersed in the dewatering sump containing boiling AK-225DH. Water 

adhering to the surface of the parts is separated by the surfactant in AK-225DH. The water rises 

to the surface of AK-225DH due to the density difference between them. It is necessary to rinse 

the treated parts with boiling AK-225 to remove the surfactant on the surface. At the end of the 

rinse, hold parts in the vapor zone of AK-225 to dry them and minimize solvent loss. Upon 

removal, parts are dry and spot free. AK-225DH is also used to dewater and dry wet parts after 

metal plating in the manufacturing of pin grid arrays and ball grid arrays. 

6. Toxicological Studies 

Many kinds of toxicological testing of HCFC-225 were carried out under the consortium of 

global fluorocarbon manufacturers called the Programme for Alternative Fluorocarbon Toxicity 

Testing (PAFT). Tests were conducted on HCFC-225ca and HCFC-225cb isomers and as a 

45/55 weight percent mixture. 

Data from acute toxicity studies indicate that HCFC-225ca and HCFC-225cb have very low 

acute toxicity. Neither isomer causes eye irritation nor dermal toxicity in standardized tests; skin 

application of both isomers at high dose (2,OOOmgkg body weight) produces no adverse effects. 

Therefore, the demial LD5Os are greater than 2,00Omg/kg body weight. Oral administration of 

either isomer at high doses (5,OOOmgkg body weight) does not cause any mortality and the oral 

LD5Os are greater than 5,OOOmgkg body weight. Both isomers also have very low acute 

inhalation toxicity as measured by the concentration that cause 50% mortality in experimental 
animals, the LC50. The 4-hour exposure LC5Os for both isomers are approximately 37,000ppm 

in rats. Cardiac sensitization response in dogs is observed at approximately 15,000ppm for the 

mixture of HCFC-225cd225cb (45/55% by weight) and 20,000ppm for HCFC-225cb. By 

comparison, a cardiac sensitization response is observed with CFC-113 at approximately 

5,000ppm. 

In 28-day inhalation studies with rat, the activity and responsiveness of the animals was 

reduced at 5,000ppm or greater for each isomer. Toxicity was otherwise confined to the liver; 

liver enlargement and induction of peroxisomes was seen following treatment with either of the 

isomers. HCFC-225ca was more potent than HCFC-225cb in eliciting these liver effects. In 90- 

day study of HCFC-225cd225cb mixture (45/55% by weight) with rat, toxic effects were 

observed in liver; liver enlargement and induction of peroxisomes. In 28-day study with 

marmoset, exposure to HCFC-225ca at 1,000ppm caused effects on the liver, such as slight fat 

deposition associated with changes in serum biochemical parameters. In the same study, exposure 

to HCFC-225cb at 5,000ppm caused somnolence during exposure and an increase of cytochrome 

P-450, indicative of an adoptive response to HCFC-225cb. However, no liver enlargement was 

seen and virtually no peroxisome induction was observed in either isomer. 

Animal testing with HCFC-225d225cb mixture (45/55% by weight) indicates that the 

compounds are not teratogenic. The compounds do not produce genetic damage in bacterial cell 

cultures (Ames Assay), CHL, and in vivo unscheduled DNA syntheses assay. The evidence from 

these studies implies that neither isomer is genotoxic. 

Based on the test results, the AELs (Acceptable Exposure Limits) of AK-225 and AK2256 have been set as 50ppm 8-hrs TWA and 250ppm 8-hrs TWA, respectively. 

7. Status of Regulation of HCFC-225 

HCFC-225 is regulated under the Montreal Protocol. The production will be phased out in 

2020 in most of developed countries. In the U.S. and the E.U., it will be phased out in 20 15. 

Final rule of Significant New Alternative Policy (SNAP) program based on Section 612 of 

the Clean Air Act Amendments of 1990 was published on June 13, 1995. HCFC-225 is listed as 

an acceptable substitute for electronics cleaning and precision cleaning applications. Concerning 

aerosol applications, HCFC-225 is also an acceptable substitute under SNAP program as 

described in the April 28, 1999 Federal Register. 
HCFC-225 is exempted from VOC regulations by the U.S. EPA as written in the Federal 

Register published October 8, 1996. 

8. Conclusion 

CFC-113 was banned at the end of 1995 in non-Article 5 countries based on the Montreal 

Protocol. Solvent applications of HCFC-141 b were banned at the end of 1996 in the U. S. based 

on the SNAP program. The applications have been frozen in 2000 and will be phased out by 

2010 in Japan based on the guideline of MITI. HCFC-225 is an HCFC and considered as a 

transitional alternative which will be phased out by 2020 based on the Montreal Protocol and 

will be banned in 2015 in the US. and the E.U. However, as described in the report of the 

fifteenth meeting of the open-ended working group of the parties to the Montreal Protocol", 

certain HCFC-225 applications and uses have been cited as critical. In view of the lack of 

appropriate alternatives with good technical or environmental performance, exemptions for AK225 may be granted. 

Such applications would include cleaning parts that require high reliability, and for newly 

developed applications that essentially require the performance of HCFC-225. 

References 

1. K. Kitamura et al.: Proceedings of the 1994 International CFC & Halon Alternatives 

Conference, p. 585, October 1994, Washington, D.C. 

2. K. Kitamura et al.: ibid., p. 779, October 1995, Washington, D.C. 

3. K. Kitamura et al.: Proceedings of the 1996 International Conference on Ozone Protection 

Technologies, p. 669, October 1996, Washington, D.C. 

4. UNEP: Report of the fifteenth meeting of the open-ended working group of the parties to the 

Montreal Protocol (INEP/Ozl.Pro./WG. 1/15/5, 12 June 1997). 
Table 1. Physical Properties of AK-225, AK-225G and CFC-113 

AK-225 AK-225G CFC-I I3 

Molecular Weight 202.94 202.94 187.38 

Boiling Point ("C) 54.0 56.1 47.6 

Freezing Point ("C) 

Density (g/cm3 25 "C) 

Viscosity (cP, 25 "C) 

Surface Tension (dynehi, 25 "C) 

Vapor Pressure (kg/cm2, 25 "CO 

Latent Heat of Vaporization (cal/g, b.p.) 

Specific Heat (cal/g"C, 25 "C) 

Solubility of Water (wt%, 25 "C) 

Solubility in Water (W%, 25 "C) 

Flash Point ("C) 

KB Value 

-131 

1.55 

0.59 

16.2 

283 

34.6 

0.24 

0.03 1 

0.033 

None 

31 

-1 16 

1.56 

0.60 

16.9 

265 

35.0 

0.26 

0.027 

0.0 16 

None 

30 

-3 5 

1.57 

0.65 

17.3 

335 

36.1 

0.23 

0.01 1 

0.017 

None 

31 

Solubility Parameter 6.9 6.9 7.5 

Ozone Depletion Potential (CFC-11 = 1 .O) 0.03 0.033 0.80 

Global WarmingPotential(COz=l .O, 100yr) 3 70 530 5000 

Table2. Physical Properties of AK-225AES, AK-225T and CFC-1 I3AES 

AK-225AES AK-225T CFC-I 13AES*' 

Boiling Point ("C) 52 54 46.5 

Density (dcm2, 25 "C) 1.49 1.34 1.50 

Viscosity (cP, 25 "C) 0.6 1 0.6 1 0.66 

Surface Tension (dyne/cm, 25 "C) 16.8 17.6 18.5*' 

Vapor Pressure (mmHg 25 "C) 29 1 265 360 

Latent Heat ofvaporization (cab'& b.p.) 40.6 47.2 42.9 

Relative Evap omt ion Rat e (Et her= 1 00) 81 72 120 

Solubility of Water (wt%, 25 "C) 0.33 0.33 0.25 

Solubility in Water (wt%, 25 "C) 0.053 0.062 --- 

Flash Point ("CJ None None None 

KB Value 41 63 39 

OzoneDepletion Potential (CFC-11=1.0) 0.03 0.03 0.8 

Global WarmingPotential (COz=l .O, 10Oyr) 350 310 4800 

Freezing Point ("C) -138 -139 -41.8 

* 1 CFC- 11 3AES is an azeotrope of CFC-113 and ethanol. *2 measured at 20 "C 
Table 3. Effect of AK-225 on Unstressed Plastics for 5 minutes at Boiling Point 
Table 4. Effect of AK-225 on Elastomers for 3 davs at Boiling Point 

Polysulfide rubber FA (T) 

Natural rubber (NR) 

Urethane rubber (U) 

Polychloroprene (CR) 

Isobutylene isoprene 

AK-225 

Wt Change Linear 

(%) Swell (%) 

67.1 14.1 

23.5 6.1 

105.4 21.4 

9.2 -0.2 

21.6 3.8 

Extractables 

CFC-113 

Wt Change I Linear I Extractables 

(%) 

6.2 

2.9 

0.2 

14.4 

7.3 

- 

(%) Swell (%) (%) 

<0. 1 0.7 <o. 1 

3.5 0.3 2.1 

1.1 0.3 <o. 1 

4.7 0.3 3.3 

1.1 <o. 1 0.6: 

Fig. 1 Schematic Diagram of three-sump 

type cleaning equipment 

Fluoroelastomer E (FKM) 

Chlorosulfonated 

polyethylene (CS M) 

Fig. 2 Schematic Diagram of vertical twosump type cleaning equipment 

106.3 18.8 2.0 0.4 <o. 1 <0. 1 

1.1 -3.1 17.4 0.9 <0. 1 0.8 

Silicone rubber (Q) 

Nitryl Rubber (NBR) 

Ethylene propylene diene 

terpolymer (EPDM) 

199.8 41.5 2.2 19.3 4.8 0.3 

102.5 21.7 11.4 0.8 <0. 1 0.5 

9.5 -0. I 14.4 4.7 0.3 3.6 
Fig. 3 Dewatering and Drying System for HCFC-225DH 
HFEs in the Aerospace Industry: A Logical Alternative to CFCs and other 

Halogenated Cleaning Solvents. 

David A. Hesselroth 

3M Performance Materials 

Introduction 

The past several years have seen an effort to find suitable replacements for ozonedepleting substances (ODSs) such as CFC- 1 13, HCFC- 14 1 b and 1,l. 1 trichlorethane 

(TCA), as well as chlorinated solvents such as trichlorethylene, (TCE), and methylene 

chloride (CHzC12). Replacement solvents must meet more stringent environmental and 

toxicological requirements, and maintain the performance and compatibility 

characteristics of the products they are replacing. Segregated hydrofluoroethers ( HFEs) 

are ethers with fluorocarbon on one side of the oxygen atom and hydrocarbon on the 

other. Non-segregated HFEs may have both hydrogen and fluorine on one or both sides 

of the oxygen. Tests have shown that the segregated HFEs have superior environmental 

properties. HFEs are non-ozone depleting, have a relatively low global warming potential 

(GWP) and most are exempt as volatile organic compounds (VOC) legislation. The 

commercially available HFEs have excellent toxicological properties. The HFEs and 

many of their azeotropes and co-solvents have excellent compatibility characteristics 

enabling them to be used with sensitive materials such as polycarbonate or acrylic. The 

use of HFEs neat, as azeotropic bends, or co-solvents enables them to clean a wide range 

of soils including light oils, silicones, waxes and heavy greases. HFEs have been used as 

direct replacement cleaning solvents in many applications. 

As with CFC- 1 13, HFEs can be used in a variety of non-cleaning applications. Heat 

transfer and electrical properties make them a suitable replacement in chillers, direct and 

indirect cooling, as well as dielectric constant temperature baths. HFEs and some of their 

azeotropes are used as carrier solvents for deposition of fluorochemical and silicone 

greases and coatings. HFEs with lubricious additives have proven to be an excellent near 

dry lubricant for drilling and machining aluminum, replacing CFC- 1 13 with a similar 

additive. With performance and compatibility properties similar to CFC- 1 13, HFEs can 

be a safe alternative with little or no modification to the existing systems. 

Environmental 

Background 

The past decade has brought many changes in the way solvents are perceived for cleaning 

and other applications. The Montreal Protocol [I ] forced the evaluation, reduction and 

elimination of ODSs. The elimination of CFC- 1 13 and TCA production and phase out 

dates for HCFC- 14 1 b in 2001 /2003, HCFC-225 in 20 15, have established cut-off dates 

for conversion to solvents with better environmental properties. The Kyoto Protocol [2] 

established a classification system for GWPs. Although an actual phase out date has not 

been set, the GWP of a solvent should be considered. The protocol calls for voluntary 

reduction of green house gas emissions to be 5% below 1990 levels in 2008-20 12. The 
uses of VOCs have been restricted in many regions to help control the release of 

chemicals that contribute to the formation of photochemical smog. Most restrictions 

cover an entire site making it difficult to monitor emissions. These factors as well as the 

worker environment, are things that must be considered when evaluating alternatives. 

The decomposition of chlorine or bromine containing molecules in the atmosphere 

contributes to stratospheric ozone depletion. Ozone or 03 protects the earth from strong 

UV rays generated by the sun. Ozone absorbs the harmful UV rays. In this region the UV 

energy from the sun is at the proper level to decompose the solvent molecules releasing a 

chlorine or bromine free radical atom. The free radical enters a catalyic cycle that 

converts 03 to 02. 

Global warming is being addressed for materials that have the potential to alter the 

earth’s natural climatic balance. Water, CO, and other naturally occurring materials 

absorb some of the infrared (IR) radiation from the sun’s rays to keep the earth at a 

relatively constant temperature. Greenhouse gasses upset this balance by adding 

additional IR absorbing materials or materials that absorb in IR regions that are naturally 

transparent. In either case the radiant heat from the earth’s surface that typically passes 

through the atmosphere is absorbed by the greenhouse gases and not permitted to leave 

the earth’s atmosphere. The term “greenhouse” is used to enable one to visualize the 

glass in a greenhouse as the gasses that accumulate in the atmosphere. When the sun‘s 

rays pass through the glass, the objects inside are warmed. The heat from the objects 

radiates inside the greenhouse warming the air. Objects outside the greenhouse are 

reflecting the same amount of heat, but without the glass, the reflected heat is permitted 

to disperse in the atmosphere. Reducing potential global warming materials emitted to the 

atmosphere will help maintain the earth’s natural balance. 

The GWP of a material is determined by two factors. One is the length of time that a 

material remains in the atmosphere. The other is the amount of IR radiation the material 

absorbs and/or the region of the IR spectrum in which it absorbs. The generally accepted 

scale sets COZ at a GWP of 1 on a 100-year horizon. A GWP is calculated based on the 

global warming contribution of a material compared to the equivalent contribution of and 

equal amount of CO2 over a 100 year period of time. Both atmospheric lifetime and the 

level of IR absorption are used to calculate the GWP of a material. 

Where greenhouse gases are typically found throughout the atmosphere, ODSs affect the 

ozone layer in the stratosphere about 50 km above the earth’s surface. VOCs can cause 

problems in the lower atmosphere with contribution to the formation of ground level 

smog. Organic compounds, such as gasoline, hydrocarbon paint thinners, and many 

solvents, decompose in the lower atmosphere. Through a series of reactions the 

decomposition products change the 02, to 03 or ozone. At ground level, ozone reacts 

with the organic compounds to form that brown layer seen around large cities on bad 

smog days. The restriction of VOC emission is designed to reduce the overall 

concentration of materials that contribute to ground level smog. 
Segregated HFEs have a balance of properties that is favorable in all three areas. As they 

are exempt as VOCs and do not contribute to smog formation, they can be used 

unrestricted in areas such as California's south coast and bay areas. They do not 

contribute to ozone depletion. The segregated HFEs global warming potentials are up to 

10 times lower than their HCFC and HFC counterparts. Table 1 shows the properties of 

selected HFEs. Table 2 shows properties of solvents scheduled for phase out and other 

proposed replacement solvents. 

SNAP 

Approved 

Table 1: Environmental Properties 

NO NO Ye5 No No NO 

1) An azeotropic blend of 50?0 HFE-7 100 and 50% trans-dichloroethylene 2) An azeotropic blend of 

52.7% HFE-7 100. 2.7% ethyl alcohol and 44.6% trans-dichloroethylene 3) An azeotropic blend of9S"i 

HFE-7100 and 5% isopropyl alcohol. 4) CFC-I 1=1.0 

Research & Monitoring Project, Report No. 44, 1998 

5) C02 = I, Source: WMO Global Ozone 

Table 2: Environmental Properties 

Segregation of the hydrocarbon and fluorocarbon portion of the ethers gives the HFEs 

favorable global warming properties. [3] Table 3 compares the GWP of 

hydrofluorocarbons (HFCs) and their HFE homologues. Table 4 shows the atmospheric 

lifetimes of segregated HFEs. 
Table 3 

Atmospheric Lifetimes and GWPs of Isomericallv Similar HFEs and HFCs 

Compound Halocarbon Number Atm. Lifetime 

(yrs) [3] 

CHiCF; HFC- 143a 53.5 

GWP[3] 

( 100 Yr JTH) 

5,400 

CHIOCF; 

CFzHCFT 

CF2HOCF 1 

CFICFHCF: 

CFJCFHOCF: 

CFiCHzCF3 

C'FiCH7OCF: 

HFE- l43a 5.7 970 

HFC- 125 32.6 3 800 

HFE-125 165 15,300 

HFC-227ea 36.5 3,800 

HFE-227ea II 1 so0 

HFC-236fa 226 9,400 

HFE-236fa 3.7 470 

CF;CH:CHF? 

CFICH~OCHF~ 

CFiCFzOCH : 

Cj FqOC H i 

C~FYOC~H;, 

Solvent Safety 

HFC-245fa 7.4 820 

HFE-245fa 4.4 570 

HFE-245cb2 1.2 160 

HFE-449~1 (HFE-7100) 4.1 320 

HFE-569sfZ (HFE-7200) 0.8 5s 

Compound 

RtIOCH; (bp = IOOOC) 

RI-OCHI (bp = l00"C) 

Atm. 

Lifetime 

R?OClH5 (bp = 130OC) 

1 R,?OCH; (br, = 150°C) I 4.2 I 

2.5 

Worker safety is an important consideration when evaluating a new material. While most 

any chemical can be handled safely, the margin of safety is important for comparing 
different cleaning processes. Exposure limits including 8 hr. Time Weighted Average 

(TWA), No Effect Level (NOEL), ceiling exposure guidelines plus others should be 

known prior to evaluating candidates. 

Product toxicity reveals significant differences in the margin of safety inherent to each 

solvent. Toxicological properties of common cleaning solvents are listed in Table 5. A 

compound’s short term or acute toxicity, reflected in the 4-hour LCso, needs to be 

considered in the event that a worker is exposed to high concentrations over a short 

period of time, as could be the case in the occurrence ofa spill or equipment failure. The 

lower a compound’s LC50, the higher its short-term toxicity, resulting in a smaller 

margin of safety. 

A compound’s exposure guideline (EG), typically an %hour time-weighted average, is an 

indication of a materials chronic or long-term toxicity. This number represents the timeweighted average concentration for a conventional 8-hour workday and a 40-hour 

workweek to which it is believed that nearly all workers may be repeatedly exposed, day 

after day, without adverse affect. A high exposure guideline will permit a greater margin 

of safety. Compounds with low exposure guidelines may require more extensive solvent 

containment or the use of some type of breathing apparatus to ensure the workers 

maintain an exposure level below recommended levels. 

Concentration 

I ) 6-hour exposurc 

2) ACGHl, 6Ih Edition ofthe “Documentation of the Threshold Limit Values and Biological Exposure 

indices” 

HFE Qualifications 

When qualifying new solvents, the environmental and safety properties are only the 

beginning. Materials compatibility and performance also are critical. Selected HFEs, 

both commercial and experimental have been tested and meet the requirements for use in 

certain military and aerospace applications. The selective solvency enables the HFEs to 

fit in a variety of applications. The neat HFEs pass the most stringent oxygen 

compatibility tests, qualifying them for the NASA procurement specification SES-0073. 

HFEs and the 50% 1,2 trans dichloroethyene azeotrope blend has passed the primary 

testing for typical aerospace compatibility, required for various specifications such as the 
Boeing, BAC D6- 17487, Aerospace Materials, AMS 1526B and the AMCOM 

specification ADS-6 1 -PRS, rev. P. 

Table 6 contains the typical testing that is required for aerospace applications. HFE-7 100, 

HFE-7200 conform to all the test requirements. HFE-7 1 DE conforms to all test 

requirements except for acrylic stress crazing. ASTM 484. Table 7 contains additional 

testing typically required for oxygen compatibility. 

Table 6, Compatibilitv TestinP: HFE-7100, HFE-7200 and HFE-71DE 

- Effect on Painted Surfaces (ASTM F502) 

- Residue Test (ASTM F485) 

- Sandwich Corrosion Test (ASTM F11 IO) 

- Acrylic Stress Crazing Test (ASTM F484) 

- Cadmium Removal Test (ASTM F483) 

- Low-Embrit. Cadmium Plate (ASTM F5 19, 1C) 

Flash Point (ASTM D56) 

Immersion Corrosion Test (ASTM F483) 

Stress Corrosion (ASTM D945) 

- Stress Corrosion ( modified") (ASTM D945) 

- 

- 

- 

Testing pei;fbrnzed tg, Scieri tl f ic Materials In ternat ion ai. 

* 3M performed ASTM D945 (modified) It was developed to accommodate solvents 

that are near residue free. In lieu of thc short solvent exposure and high temperature 

exposure, the samples here held in the boiling solvents for five days. 8 hrs per day. 

- 

- 

Table 7 : OxvPen Comsatibilitv Testing 

-Mechanical Impact (NASA test) 

-Autogenous Ignition Temp. (ASTM G72 - 82) 

'Te\titig pcr/ornicd b?.. ,2:-1S.4, ./ohriwii Spucr Cenlei. Wh[e Sriridv TPSI Fuciliri. 

HFE- 71 00 and HFE- 7200 met test criteria. 

Solutions for aerospace cleaning challenges 

Cleanliness is of vital importance for parts and equipment used in military and aerospace 

applications. However, when evaluating cleaning products, compatibility is as important 

as cleaning ability. This is not surprising, given the risks associated with poor 

compatibility in these applications. Qualification of new materials is an onerous and 

expensive process. Because of this, CFC-113 is still used in many applications. 

Replacement solvents must provide adequate cleaning performance and exhibit excellent 

materials compatibility. Extensive compatibility testing is performed before adopting a 

new cleaning process. 
Another strong driver for selecting new cleaning processes is the environmental profile. 

Since qualification of new cleaning processes is neither cheap nor easy, users give the 

environmental profile of a replacement product more weight than other industries, in an 

effort to avoid future re-qualifications resulting from evolving environmental policy or 

new regulations. In addition, qualified product must be used throughout the world. 

Therefore, it is desirable that global regulatory bodies accept a new cleaning compound 

or process. 

Cleaning gyroscopes and altimeters 

Challenge: Find replacement for CFC-I 13 for use in a vapor degreaser that removed 

various hydrocarbon and silicone oils, as well as particulate. The cleaner had to perform 

quickly enough that it didn't affect the sensitive materials on the assemblies. The solvent 

of choice was to have zero ODP, low GWP, and provide users with a safety margin 

similar to that of CFC- 1 13. 

Solution: In cleaning altimeters and gyroscopes, the US Army and Airforce chose to 

qualify HFE-7 1 DE, an azeotrope of HFE-7 100 and trans- 1, 2-dichloroethylene. An 

independent laboratory performed candidate screening and much of the qualification 

testing. The decision to employ HFE-7 1DE was based not only on the excellent cleaning 

results achieved, but also on comparative environmental and safety properties. 

Oxygen gauge cleaning 

Clzallenge: Find replacement for CFC- 1 13 to remove light oils and particulate from 

oxygen gauges. The solution must be oxygen compatible and leave no residue. The 

process is listed in Mil Std. 1330 D. 

Solution: For oxygen lines and storage tanks, an aqueous cleaning process (NOX) is 

used. However, the tight clearances on gauges require a solvent-based cleaner in order to 

avoid problematic residues. 

For most oxygen gauge cleaning applications, HFE-7 100 was found to be a suitable 

solution. However, where more aggressive cleaning is needed, a two-solvent process is 

being evaluated. The process will use HFE-7 1 DE cold cleaning, followed by an HFE7 100 rinse. The HFE-7 1 DE will easily remove the soils found in oxygen equipment. 

Rinsing with HFE-7 100 ensures a clean and particulate-free part. The system uses 

products with the same base solvent (HFE-7 100) to ensure good mixing, resulting in an 

efficient rinse. 

The above same-solvent philosophy factored into the decision by the Royal Australian 

Air Force to approve an HFE-7 1 DE clean/HFE-7 100 rinse process for cleaning oxygen 

lines. 

Cleaning transmissions, hydraulics, and various mechanical parts 
Challenge: Replace chlorinated solvents for a variety of cleaning applications with a 

more environmentally acceptable and less toxic product. The process must be easy to 

operate and cannot introduce a corrosion risk. 

Solzition: Given the wide range of soils and substrates cleaned, process flexibility was 

important. The user decided on a co-solvent process, utilizing Petroferm's, solvating 

agent, SA-70 and HFE-7 100. Aqueous cleaning was eliminated due to the risk of 

subsequent corrosion. The co-solvent process uses a high-boiling hydrocarbon solvent as 

a solvating agent to remove the soils. The solvating agent is miscible with HFE-7100 

(the rinse solvent), allowing the user to vary operating temperature and ensuring a 

complete rinse. The solvating agent has extremely good solvency (Kauri Butanol value 

> I50), yet is not aggressive toward sensitive parts. This, too, improves the flexibility of 

the process, allowing one machine to be used for a variety of cleaning applications. 

CIeaning aircraft bearings. 

Cl~allengc~: Removing soils that vary from light oils to very heavy greases from aircraft 

bearings. 

Solzition: A co-solvent process is under evaluation to replace a multi-step hydrocarbon 

solvent cleaning process. The improved flexibility of the co-solvent process has shown 

excellent cleaning results and will eliminate VOC emissions. The only emission from 

this process is the loss of the rinsing agent, HFE-7 100. This allows for unrestricted use 

of the process to anywhere in the US. 

Cleaning silicone mold-release from polycarbonate medical device parts 

Chu//t.ngc~: Replace CFC- 1 13 in a process used to remove silicone mold release from 

highly stressed, injection molded polycarbonate medical devices. The process must be of 

high enough solvency to remove the silicone, yet be compatible with the sensitive 

substrate. 

Solution: Several potential solutions were evaluated. The first evaluation centered on 

using neat vapor cleaning with either HFE-7 IO0 or HFE-7200. Cleaning with the HFE7200 was found to be adequate, but the higher temperature resulted in increased stress 

cracking compared to the CFC- 1 13 control. Stress cracking was not as prevalent with 

HFE-7 100, but cleaning was not adequate. 

An azeotrope of HFE-7 100 and isopropyl alcohol, HFE-7 1 IPA was evaluated and found 

to have good cleaning with compatibility similar to the control. It was noted that the 

slight decrease in boiling point, from 6 1 "C to 56OC, significantly reduced the stress 

cracking. 

A second solution proved to have the best performance. A co-solvent process used a 

blend of 90% HFE-7100 and 10% Isopar M as the solvating agent and HFE-7100 as the 

rinse aid. This solution resulted in excellent cleaning results and virtually no stress 

cracking, noticeably less than what was seen with CFC- 1 13. However, the process 
required close monitoring of the boil sump composition in order to maintain temperatures 

below 57°C. Ultimately, the manufacturer chose to implement HFE-7 1 IPA cleaning, as 

it was an easier process. 

Cleaning of polyurethane catheters 

Challenge: To remove light oils and particulate from a polyurethane catheter. The 

manufacturer traditionally used a chlorinated solvent for cleaning applications but found 

them to be too aggressive on the sensitive catheters. In addition to compatibility, a 

second concern was that the parts had to be cleaned on the production floor in close 

proximity to production personnel and it would be difficult to control exposure of the 

cleaning solvent below 25ppm. 

Solution; Given that application involved only light cleaning and that compatibility was 

the chief concern, HFE-7100 and HFE-71IPA were evaluated. Both proved to be 

effective cleaners for this application. Compatibility studies showed a negligible amount 

of extraction from the tubing on exposure to HFE-7 100. Testing with HFE-7 1 IPA 

showed a very low level of extraction (0.1%); even at this low level, a change in 

appearance and feel was observed. Due to this difference, neat cleaning with HFE-7 100 

was implemented. 

Flux removal after high temperature soldering 

Challenge: Replace methylene chloride in the removal of flux residue from a ceramic 

circuit board that had undergone solder reflow at 260°C. The manufacturer required no 

residual contamination visible on inspection under a 20X microscope and UV light. The 

evaluation was made more difficult as the parts were cleaned not immediately following 

the solder process but about one-week later. 

Solution: Several boards were submitted for evaluation with different cleaning products 

and processes. A defluxing azeotrope was tested but did not adequately remove the 

residue--traces were visible on inspection. Co-solvent cleaning using SA-70 and HFE7 100 formulated to boil at 80°C in the boil sump and rinsing with HFE-7 100. Ultrasonic 

agitation was used in both the boil and the rinse sump. The process, involving a sixminute dwell in the boil sump and a two-minute rinse, provided excellent cleaning 

results. 

Drilling aluminum during assembly operations 

Challenge: Find a replacement for Freon TB-1 and Boelube used to lubricate drilling 

operations during assembly of aircraft subassemblies and major components. Boelube 

has replaced Freon TB- 1 in most operations. but requires significant effort to remove 

drilling residues from surfaces that will later be sealed or painted. In most cases, this 

cleaning is done by hand with solvents and wipes adding to labor costs and slowing 

production. 

Solirtioii: HFE-7100 based drilling fluids, MW-2400 and MW-2410 can be used much as 

Freon TB-1 was used in the past with good drilling performance, but does not leave oily, 

sticky drilling residues. Both MW fluids are formulated to lubricate aluminum drilling 
when applied as a low volume jet or spray directed at the tooling. Both the HFE-7 100 

and the additives are fully volatile which leaves a clean and dry work surface, a dry work 

area (not slippery). and minimizes cleanup to removal of dry chips. 

Conclusion 

The conversion from ODSs or other chlorinated solvents, to more environmentally 

acceptable substitutes for cleaning applications continues. While many applications were 

a relatively easy conversion, there remain a number of more challenging applications for 

which a replacement is not easily found. Developing solutions for these difficult cleaning 

challenges requires a problem-solving mindset. Manufacturers need not sacrifice safety 

and environmental properties in exchange for performance. Effective and acceptable 

replacements can be found when suppliers and end-users work together to tailor an 

innovative solution to a specific application. 

[ 11 

[2] 

[3] 

Montreal Protocol on Substances that Deplete the Ozone Layer and its attendant 

amendments, United Nations Environment Programme, 1987. 

Kyoto Protocol to the United Nations Framework Convention on Climate 

Change, United Nations Environment Programme, 1997. 

Owens, J.G., Segregated Hydrofluoroethers: Low GWP Alternatives to HFCs and 

PFCs, Proceedings of the Joint IPCCITEAP Expert Meeting on Options for the 

Limitation of Emissions of HFCs and PFCs, Energieonderzoek Centrum 

Nederland, Petten, The Netherlands, 1999. 
Lightweight Multi-layer Structural Materials 

H.H. LEGNER and W.T. Laughlin 

Physical Sciences, Inc. 

20 New England Business Center 

Andover, MA 0 I8 IO USA 

Phone: 978-689-0003 or 978-983-2234 

Fax: 978-689-3232 

E-mail1 lemerhhxicom.com i 

V. Di Cristina 

ThermoPhysical Sciences 

D. Marshall and R. Singler 

Textron Systems 

A new lightweight composite material with combined structural and thermal protection 

capability has been developed for both air vehicle and spacecraft application. The basic concept 

consists of the integration of a high-density outer layer with a low-density foam core, using stitching 

loops to integrate the material three-dimensionally. The layers are chemically bonded and 

mechanically linked. The generalization of this technique to integrated structural materials with two 

high-density face plates sandwiching the low-density inner layer provides an entirely new approach 

to fabricating cost-effective aero-shell and spacecraft structural materials. These materials have been 

evaluated structurally, as well as thermally in arc-jet and laser tests. Thermal insulation performance 

exceeds that of standard heat protection materials. Measured compressive and bending strengths 

have shown substantial residual load-carrying capabilities. In addition, damage tolerance and crush 

strength properties have been demonstrated to be superior to comparable honeycomb structures. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc. nasa.gov 
ELIMINATION OF MEK AND LACQUER THINNER 

IN DEPARTMENT OF DEFENSE PAINTING OPERATIONS 

Authored by: Mr. Joseph Lucas and Mr. Eric Lethe 

lnland Technology Incorporated 

401 East 27th Street 

Tacoma. WA 98421 

(253) 383-1 177 I inland@inlandtech.com I 

Painting operations at aerospace and Department of Defense facilities create large and problematic waste 

streams as well as major emissions of hazardous air pollutants and VOC's. Some of these emissions are a result of 

the composition of the paints used. and as a result, create a waste stream that can only be addressed by a 

reformulation of the specific paints and coatings. However, the greatest percentage of waste and emissions 

generated by painting operations is a result of the use of MEK and lacquer thinner in clean up and surface 

preparation activities. Usage of these hazardous materials account for an excess of 509" of the overall waste 

generated by a painting facility. The successful elimination of MEK and lacquer thinner for these painting activities 

would clearly assist these facilities in meeting the requirements of the Aerospace NESHAPS and Executive Order # 

12856. and would facilitate a considerable reduction in the overall generation of hazardous waste. 

This presentation is an exemplary representation of successful replacement projects that have taken place at 

civilian manufacturers, aerospace. and Department of Defense installations. It will detail the substitution process 

from a chemical developnient standpoint. and will discuss the equipment validation procedures, work practice 

changes. and training required to make the substitution process successful. In each case study, the end result was a 

replacement process and chemistry that was more environmentally responsible and less regulated than the original 

process. In addition, each substitution project resulted in demonstrable cost savings. 

Case Study #I 1 

US Army, Aberdeen Proving Ground had a strong incentive to reduce the hazardous waste generation 

caused by the use of paint thinner as a cleaning solvent at the Auto Body Shop. Ms. Amy Borman and Mr. Keith 

Katz determined the necessity for a substitution project. following an environmental audit which the safety and 

environmental officers conducted. The pre-existing conditions were; paint gun cleaning that consumed 70 or more 

gallons of lacquer thinner each month, and evaporative loss and contamination from usage, creating the need for 

frequent disposal of dirty lacquer thinner and replenishment with fresh material. This frequent disposal of lacquer 

thinner makes the cleaning process a major source of emissions and hazardous waste. The challenge for the research 

team was to provide a cleaning solution that would eliminate these problems. It was first necessary to develop a 

technology that would make the alternative material cost effective to use. The new cleaning solution ideally would 

contain no hazardous air pollutants, be non-flammable, and have minimal worker exposure risks associated with its 

use. The new material, therefore, would present considerable differences in behavior, even while accomplishing the 

cleaning task it was designed to do. Additionally, training procedures and work practice modifications required 

development in order to accommodate the differing characteristics between the new cleaner and the old style 

thinner. The research team took these criteria into the laboratory for experimentation. 

The Solution-From a Chemical Standwint 

lnland Technology developed and patented "a low toxicity solvent composition" known as EP-93 Th'. This 

solvent alternative was developed to mimic the Hansen's Solubility Parameters of MEK almost perfectly. It 

contains less than 1% VOC, has no ozone depleting or EPA 17 chemicals in the formula, and has a flashpoint of 

1.56" F. EP-921Tb' eliminating the fire risks associated Kith lacquer thinner or MEK. This new cleaner proved 

effective in the removal of & uncured and senu-cured paints used by the Army, including the chemical resistant 

CARC coating. In December of 1998 EP-92 1 Ihl was awarded a toxicity clearance from the US Army Center for 

Health Promotion and Preventative Medicine 
The Solution - From an Equipment Standpoint 

In order to maximize the cost effectiveness ofthe new cleaning compound. new equipment was engineered 

for the cleaning process. The Edge TekTM Filtration System filters the EP-92 1 Thl on line as the cleaning station is 

heing used. The system filters down to .I micron nominal, and removes a major portion ofthe paint solids. This 

allows the EP-92 ITM to be re-used for a niemure of months. Typically, the only wastes being disposed of are the 

filter elements, and a small amount of settled paint solids. The volume of hazardous waste disposed is reduced by 

greater than 85%. 

The Solution -Work Practices, Training and Putting It A11 Together 

Since there is no evaporative loss associated with EP-92 IThf, most of the training and work practices 

necessary for the implementation of EP-92 In' into a paint shop involve consendon techniques. It is also critically 

important to develop techniques for the removal of unevaporated EP-921TM from the surfaces ofthe painting 

equipment. Conservation techniques involve cascading the extremely dirty EP-92 IT" into a gross-cleaning 

operation. capture of the rinsate material. separation of the paint solids from the EP-92 lTM3 and filtration ofthat 

material in order to extend the usable life ofthe cleaner. The EP-92 I TM is unique in that its chemistry is able to 

attract the paint from the surfaces ofthe application equipment (paint lines, spray guns, pressure pots and cups) and 

form micelles of the free-floating paint. However, the paint has no opportunity to bond with or emulsify within the 

EP-921N. The greater specific gravity ofthe paint allows the paint to settle out, or to be easily filtered out. of the 

EP-92P. This lack of emulsification also prevents the EP-92 lThl From losing effectiveness, since the cleaner is not 

becoming saturated with paint. This exemplifies the nature of EP-92 ITM as a use-specilic product which cannot be 

used as a surface preparation or thinner for paint or coating. 

Final removal of EP-92 IT" from painting equipment involves the \viping ofthe surfaces with a dry rag 

inside the cup or pot and outside of the cup and gun head. Either rinse the inside of the clip with Teksol EPCk', or. 

refill the cup or pot with Fresh paint, and shoot it through the gun head into the waste paint container. The painter is 

now ready to begin the next painting job. It is of the utmost importance that the painter do a "pattern check" spray, 

(this takes 5 seconds or less spraying) to make sure all the EP-92 IT" is out of the gun head. 

The Results 

In May of 1996, two paint gun cleaning stations were filled with an initial charge of 5 gallons of EP-92 ITM 

and were put into service. A review ofthe performance w~s conducted 47 months later. It is notable that these 

same gun cleaning stations are still in use today. The records show that the total purchases for the stations during 

that 47-month period, consist of95 gallons ofEP-921TM and 15 cases of 12 Edge Teknl Filter Elements, however. 

not all of these had been consumed after the 47 months. Enussions of hazardous air pollutants, VOC's, and EPA 17 

chemicals have been cut to nearly zero. In a cost comparison with lacquer thinner, 47 months usage would have 

been 3.290 gallons at a cost of approximately $ 2.00 per gallon for a total of $ 6.580.00. The disposal volume for 

that same period would have been approximately 1,64S gatlons. at a cost of $ 5.00 per gallon totaling $ 8,225.00 The 

costs ofthe traditional method of painting equipment cleaning had a total cost of $ 14,805. By comparison, the use 

of EP-921m and the Edge Teknl Filter System was: Acqiiisition of 95 gallons of EP-92 Irk' at a cost of $28.95 per 

gallon, totaling $ 2,702.7.5, and the Edge TekT*I Filters, at a cost of $ 13.30 per filter element. totaling $ 2,079.48. 

The disposal cost for the 156 filter elements was $360.00. These filter elenients were contained in one 55 gallon 

drum. The total cost for the 47 months usage ofthe EP-92Imb was $ 5,142.23. This represents a cost savings 

of nearly 300%! This cost savings is strictly a monetary assessment: while volume of airborne emissions was 

reduced from 11.515 pounds of hazardous air pollutants from the cleaning process to E pounds. 

Case Studv #2 

Another example of the opportunity for nuninlization of airborne emissions from the painting equipment 

cleaning operations took place at Eglin Air Force Base. The point ofcontact was Mr. AI Holley, Painting 

Supervisor for the small parts painting shop. The inissioii at hand was to replace MEK in use as a clean-up solvent 

for the painting equipment. The replacement cleaner would have to be non-VOC, non-HAP, contain no ozone 

depleting chemicals, and contain none of the EPA 17 chemicals. The alternative clean-up solvent would need to be 
erfective in the removal of uncured epoxy primers and polyurethane topcoat paints, iis well as have a compatibility 

with the gaskets and seals present in the painting equipment. 

The previous conditions that were encountered at the sinall parts painting shop were: five full time painters 

who worked a day shifi and a swing shiff using high solids epoxy primers, and polyurethane top coats. The yearly 

consumption for the cleaning of the paint guns was approximately 5,200 gallons of MEK. The blend of waste paint 

and MEK accounted for 27,400 pounds of hazardous waste generated by this small shop per year. Additionally. the 

air emissions assessment for this shop showed niore than 14.000 pounds of Ilazardous air pollutants and VOC 

emitted per year. Incoming MEK purchases totaled !j h,OOO.OO per year. however, add to that the hazardous ~vaste 

disposal cost of $ 12,450.00 per year. 

The combined Eglin AFB, Inland Technology Task Force gathered data in order to develop and iniplenient 

the ideal solution both for the air emission and solid waste issues. From interviews with the painters, it was learned 

that the current cleaning tanks were inefficient at cleaning all of the small openings and valves in the paint guns that 

were in use. After the paint guns were flushed in the tanks, the painters needed to disassemble the guns and hand 

detail all of the paits with a sinall bucket of MEK and a brush. The ideal piece of equipment would allow for both 

flushing of the gun heads, as well as detail work. This would be done preferably in the same piece of equipment, 

and with a non-hazardous cleaner. The perfbnnance criteria are the same as the previous case study, with a special 

emphasis on cleaning ofhigh solids paints. If the paint is not completely removed from the equipment, the gun head 

will clog or spray in an erratic pattan. The high solids paints are also very prone to ”clabbering” or congealing in 

the presence of water or incompatible solvent cleaners. The congealing of the paint in the gun head will cause such 

severe clogging. that the gun will need to be detailed with a stripper compound. This takes a long time, and the 

strippers are often destructive to the seals inside the gn head. The environniental criteria was driven by the need to 

reduce the generation of hazardous waste, with an emphasis on worker health and safety. Determination was made 

(using off-line trials) that the EP-92ITLZ would remove the uncured and srnu-cured paints used at Eglin AFB. The 

next order was to comply with the request for a piece ofeqiiipment which would allow for the flushing of the gun 

head assemblies, cleaning of the cup interiors. and cleaning of the cup and gun exteriors. Such a machine would 

need an air-operated pump. and would utilize the Edge TekTM Filter System to minimize the disposal ofthe used EP92 I‘M. The cleaning unit would need to be of a stainless steel construction in order to %sure a long usable life for 

the unit. Rased upon the requests ofthe en\ironmental officers and the painting crew, the IT-45SSEKTM WIS 

conceived. 

Unit specifications fnr the lT-45SSERT*J Paint Gun Washer 

Measurements: 37” x 3 I” x 71“ high, constructed of 14-gauge schedule 304 stainless steel, utilizes an airoperdted diaphragm pump. and is equipped with the Edge TekT” Filter System including a 25-micron resin prelilter. 

The training procedures for implementing the EP-92 lTb* and the IT-45SSERT”’ were overseen by the 

environmeutal officers. as well as the Paint Quality Assurance Team. Initially the new unit was placed along side 

the old style cleaning tanks. This provided a “security blanket” for the painters while they wete becoming 

accustomed to using the non-evaporating EP-92 IM. After several days. in which the painters discovered that the 

EP-92IThf was even more effective in the cleaning of the orilices of the gun heads, the old tanks were removed. The 

most radical change the painters experienced was the ability to clean the guns and cups in an open tank, without 

breathing the unpleasant funies of the MEK. The other change was the need to follow the cleaning with a dry rag 

wipe to the exterior surfaces of the gun head and cup. as well as the interior ofthe cup. The EP-92iTb1, which 

remained in the “barrel” of the gun head, was completely flushed away by the initial pattern-check spny of the next 

charge of paint. All of the various types of paint and primer that were cleaned in the old style washer were 

successfully tested in the IT-4.5SSERTh’ exhibiting no degradation of the gun seals. and no clogging of the spray 

ports in the gun heads. 

After an assessment period of 14 months, the IT-4SSSERTM at Eglin AFB showed these results: The shop 

now uses no MEK, and as a consequence. the paint shop einits zero Hazardous Air Pollutants or VOC’s from the 

cleaning process. Additionally, the shop generates only 30 gallons (or 240 pounds) per year of hazardous waste 

froiii the cleaning of the painting equipment. Perhaps the most startling outconie is that the initial charge of 25 

gallons of EP-92 lThl has lasted over one year. This is a comparable chemical purchase cost of$ 723.75 instead of %; 

6.000.00. In addition, a volume reduction of hazardous waste of niore than 27.000 pounds! The 1T-45SSERTM Paint 
Gun Washer and EP-921Thf have now been given National Stock Numbers, and are currently in use in all branches 

of the Department of Defense. 

In conclusion, these case studies are examples of successful process substitution projects. It should be 

noted that no one chemical, or piece of equipment, should be supposed to solve all environniental concerns. The 

greatest efforts were those involving the training and modifying of the SOP'S (Standard Operating Procedures) for 

cleaning of the painting equipment and handling of the resultant wastes. It is a testimony to those training efforts. 

more than simply purchase of a new product. which resulted in the dramatic reduction of hazardous wastes from 

these sites. 
Asbestos Free Insulation Development for the 

Space Shuttle Solid Propellant Rocket Motor (RSRM) 

Larry D. Allred and Norman F. Eddy 

Thiokol Propulsion 

P.O. Box 707 

Brigham City, Ut& 

(435) 863-6692 

)allreld@thiokol.com I 

(435) 863-2440 

eddynf(ujthiokol.com I 

Copyright 2000 Thiokol Propulsion. 

A Division ofCordant Tcchnoloycs Inc 

All rights roscnrcd 
/ Asbestos Free Insulation Development for the 

Space Shuttle Solid Propellant Rocket Motor (RSRM) 

ABS TRACT 

Asbestos has been used for many years as an ablation inhibitor in insulating materials. It has been a 

constituent ofthe AS/NBR insulation used to protect the steel case of the RSRM (Reusable Solid Rocket Motor) 

since its inception. This paper discusses the development of a potential replacement RSRM insulation design, 

several of the numerous design issues that were worked and processing problems that were resolved. The earlier 

design demonstration on FSM-5 (Flight Support Motor) ofthe selected 7%) and 1 l‘h Kevlar” filled EPDM 

(KF/EPDM) candidate materials was expanded. Full-scale process simulation articles were built and FSM-8 was 

manufactured using multiple Asbestos Free (AF) components and materials. 

Two major problems had to be overcome in developing the AF design. First, bondline corrosion, which 

occurred in the double-cured region of the aft dome. had to be eliminated. Second, KFiEPDM creates high levels of 

electrostatic energy (ESE), which does not readily dissipate from the insulation surface. An uncontrolled 

electrostatic discharge (ESD) of this surface energy during many phases of production could create serious safety 

hazards. Numerous processing changes were implemented and a conductive paint was developed to prevent exposed 

external insulation surfaces from generating ESE/ESD. 

Additionally, special internal instrumentation was incorporated into FSM-X to record real-time internal 

motor environment data. These data included inhibitor insulation erosion rates and internal thermal environments. 

The FSM-X static test was successfully conducted in February 2000 and much valuable data were obtained to 

characterize the AF insulation design. 

INTRODUCTION 

The primary insulation used on the current space shuttle RSRM is an asbestos and silicon dioxide filld 

acrylonitrile butadiene rubber (ASINBR). Asbestos is also used in some RSRM adhesives, litw and astable inhibitor. 

Asbestos is a commercial term for a group of naturally occurring fibrous crystals made of hydrated silicates. Some 

forms of asbestos are considered a serious health hazard. Since the current regulatory policy in the United States 

does not differentiate between types of asbestos, the use ofall asbestos could be restricted with little warning, which 

could affect production of the RSRM. Elimination of asbestos containing materials is also motivated by liability 

issues during the handling and processing of asbestos containing materials and the recurring costs associated with 

OSHA regulation compliance and indemnification. (4) 

A development program was initiated in 1986 and numerous Asbestos Free (AF) insulation candidates 

were evaluated using seventy-pound charge (SPC) motors and Modified NASA (MNASA) motors. KevlarK filled 

ethylene pmpyla diene monomer (KF/EPDM) insulation had previously been selected for use in several solid 

rocket motors (SICBM, CASTOR 4B. CASTOR 120). Several modifications of this KF/EPDM formulation were 

made to meet structural and ablation requirements and a 7% KFEPDM was selected as the primary insulation for 

the AF RSRM. 

This paper discuses the AF insulation design and wme raults of a full-scale static test using AF mataials in 

the major components ofthe motor. The resolution of two major problems that had to be overcome in developing the 

AF design is also disassed. First, bondline corrosion, which occurred in the double-cured region of the aft dome, 

had to be eliminated. Second. KF/EPDM creates a high level of electrostatic energy (ESE), which does not readily 

dissipate from the insulation surface. An uncontrolled electrostatic discharge (ESD) of this surface energy during 

many phases of production could create serious safety hazards. Numerous processing changes were implemented 

and a conductive paint uas developed to prevent exposed external insulation surfaces from generating ESE/ESD. 

OVERVIEW 

The thermal-ablative insulation development effort began by evaluating several families of base polymers 

(polyisopra. styrene-butadiene, silicone, EPDM, NBR, etc). fiber fillers (Kevlar’, Kynol’, polybenzimidazole, etc.), 

flame retadant md curaive packages The insulations we developed to provide emsion performance. The best 

formulatiom forerosion resistance were a hily of Kevlar“ fiber filled materials. An initial I lo/; KFEPDM 

Copyright 2000 T’hiokol Propulsion. 

A Division of Curdant Tcchnologics Inc. 

All rights rcsencd 
formulation had been developed with aresin curative system and had bm used in sewral space lrunch anl strategic 

SRMs. The AF progm developed a sulhr curd 7% KFiEPDM as the primary insulation. A sulfw-based cure was 

selacted over a resin-bwed cute system for similarity ofshrink charadenstics with ASiNBR, higher strain capability and 

lower stitbess uhile srrrificing some ablation capability and perhaps acrossply tiacture toughness. A backup I I?;, 

KF/EPDM was fomiulated to be similar to the 7% KF/EPDM that could be usid in the aft dome in case of 

unexpectedly sewe 70/0 KFI'EPDM ablation with motor scaleup. Results of detailed structural chamcterintion of the 

7'1 ,, KF,'EPDM design showed the 7% KFiEPDM to have maginal acrossply and perpendiculx to fiber stress ard 

intala;iina hciure toughness capabilities. The margiwl interlamina caphilitie result fiom the bae polymers, 

Kevlar . fie retxdant and antioxidant fillers used to meet other process and design requirements. A silica filled NBR 

(SFNBR) ww selected for use in high structural lad regions such as the propellant stress relief flap terminus. (I) 

Theoriginal AF bign pal was to have a single maerial replacement br theRSRM. The design wuld 

directly substitute an qual thicknes of7Y0 KFIEPDM in place ofASINBR and a7 increased thicknes of 7% 

KFiEPDM in placeof carbon fiber filled EPDM (CFIEPDM) in the aff dome. During thedevelopnent p-ocess. the AF 

insulation was tested in prograsively larger sub-scale motors. The KFiEPDM was fitst tested in seventy-pound 

propellant charge (SPC) motors. The SPC motor consists of an enrl burning propellant grain and attached blast tube. 

KFiEPDM rubbers md the RSRM brselins of CFiEPDM mbber and ASiNBR weR then tested in modified National 

Aermautic and Space Adnlinistraion (MNASA) motors. The MNASA motor ha a 115 scale RSRM aft segment blast 

tubeand a 10,00@pound, centerperfcrated p-opellmt chxge. The MNASA motor surpzses the SPC motor m 

reliability of results, but it has gleater msts ad cycle time. Thermal-ablaive cTability of 7% KFiEPDM in sub-sde 

mota was equivdent to ASINBR The thermal-ablative crpability of 1 In41 KFiEPDM was equivalent to CFIEPDM 

and its eraion rate was up to 40',;1 laver thm ASINBR. (I) 

The 7% KF/EPDM and I 10'0 KFiEPDM were tested in the aft dome and partial aft segment regions of the 

full-scale static motor designated FSM-5. The 1 I% KFiEPDM performed as expected and equivalent to CFiEPDM 

in all but the two aft-most ablation stations designated 9.3 and 10.7-inch stations (measured axially from the nozzle 

boss). The within-motor variation was less than or equivalent to CFIEPDM. The CFiEPDM also shows increased 

ablation in these aft-most stations on static test motors, but is much less severe. The 7?h KFIEPDM performed 

slightly worse than expected, in general. The surprising result was that 7% KFiEPDM performed better than the 

I lei; KFI'EPDM at the 9.3-inch station. This condition was likely due to the asymmetrical erosion caused by 

nozzle vectoring. The results of the FSM-5 fullscale static test showed that the baseline CFIEFDM wai vastly 

supgior to both KFI'EPDM materials in the aff domeenvironment. CFiEPDM is used in RSRM aft domes because 

of its high thermal-ablative resistance. CFiEPDM remained the aft dome insulation for severs exposure regions in 

the AF design. ( I ) 

RESULTS AND DISCUSSION 

Asbetos Fm Insulation Design Confwuration 

The AF insulation design that lesulted following FSM-5 uses four insulaion materials to saisfL competing 

stmtural and thermal-~lativerequirements. A 7% KFIEPDM was selected as the ovemll best replacement insulaion 

for igniter compcnents, nozzle flex boot and the internal acreage regions ofeach sgment. A comparison of the RSRM 

versus the AF RSRM is sbown in Figure 1. The aft dome design uses I I%KF/EPDM as asubstlae to CFiEPDM in 

a smdwich constwtion similar to the currmt RSRM. The CFiEPDM was implemented as a result ofthe severe 

erosion expienced on FSM-5 in the ati dome region The 1 IYo KFIEPDM w dewloped for highly ablative 

environments with low structural loads. 'The detailed ail dome design is shown in Figure 2. The 1 10/0 KFiEPDM 

substrate pvids greater erosion mxgin than theAS/NBR with minimal impact on production and mst. 

The AF design usa 7'3'0 KFI'EPDM in the case cylinderregicns of mch segment, in the igniter conipments 

and in thenozle flex boot. The cud KFiEPDM is an orthotropic material. As such, it wai shown to haw marginal 

across-ply and pependimlar to fiber stress and interlaminar fiacture toughness capabilities. Because of the lower tensile 

capability of the KFiEPDM in tk acratis-ply and perpendiadar to ply orientations, structud sakty faciors cauld not be 

met in seval high stms regions. In these regicns, SFiNBR was used to satis@ the struduml requirenents. SFiNBR 

provides much higher structural capabilities with minimal impact on production. Theareas in thesegments, the igniter 

and the adrpter where SF/NBR was used are low them1 exposure mvironments. Therehre. the lower thermal 

capability of the SFiNBR providd adquate p-otection for these areas of the motor. 
AS-NBR Igniter 

Current RSRM Design (2-material system) 

?/e KF-EPDM 

Asbestos Free Insulation Design (4-material system) 

Figure 1 -Comparison ofRSRM and AF Insulation Designs 

RSRWAF RSRM 

NomiT' 

C F - E P D M 

SRM CF-EPDM 

S-NBR interface 

KF-EPDM 

AF RSRM CF-EPOW 11 % Interface Chemlok 

7% KF-EPDM Bonding Ply 

7% KF-EPDM 

AO44,*,. 

/ 

Chemlok 

11% KF-EPDM I 

Chemlok primer 

Chemlok 

Figure 2 - AF Aft Dome insulation Design 
FShl-8 Desim Demonstration 

The intention ofthe AF insulation dwelopment program was to msture the design to the point that a 

denimstration ofall major design t'eaures and components would be completed. Favomble raults from a full-sale 

static test would confirm the wlidity of the desig. However. full qualification ofthe design would quireadditional 

static tests and other qualifiation efforts Thus FSM4 was selected as the demomtntim test bed fbr the AF design. 

To aver tk major design features, AF insulation, materials and proceses wae implemented on key portions ofthe 

static test motor in suport ofthe AF replacement progran. Thee area are listed below and shown in Figure 3. 

Inttmal imulation -- igniter chamber (ID. OD and xal disks), adapter. initiator (helmet ad seal disk) forwad 

Joints - igniter inner (to adapter) ad outer (to hnvard dome)joints, aft field joint 

Liner - igniter chamber. initistor, &/center segment and aft Egment 

Castable inhibitor -- fonvard scgment and afb'center segnialt 

Fowd-bang molded inhibitor- amcenter segmem and afi segment 

Adhaive - initiator. igniter chamber, initiator to adapter joint, seal disk bonds and insulation repais 

segment igniter boot region, afficenter segment. ati segment and nozzle flex boot 

Erosion data from MNASA motors indicsted tha the performance ofthe AF insulation mould be similar to the 

RSRM insulaion. However. since the only actual pe6ormme data from a fullscale motor waj in the aft dome region 

of FSM-5, the insulation thickness wm increaed in untested regions to meet a 2.0 thermal safety factoctor. Minimal 

inipxt WM expected due to the incrmed insulation thickness fix eitha ballistic or them1 performance. 

'4s mentioned, the initiaor to adapter joint was completed with AF adhaive. The igniter inner pint. mating 

the igniter adapter to the igniter chamber. was made of AF insulation. tn orda to hae an AF igniter outer joint, the 

insulation at the forwad dome mating surface was made 0f7~h KFIEPDM. The aff and &/center segnents. made of 

AF insulation, wae mated to form an AF aft field joint. Because the center field joint would have mated dissimilar 

niataials nd served no demonstration hnction. the mating surfixe of the aWcenter segment was changed to match the 

ASiNBR ofthe fonvard!'center segment. A conflict of demonstration objectives existed on the FSM4 nozzle-to-caje 

joint. Because this joint had previously been sucmshlly denimstrated on FSM-5, the mating sulface msterial at the 

node-to-me joint was changed to AS/NBR. 

The igniterchanikr and initiator wele lined with AF lina, as were the entire afiicenter nd afi segments. The 

AF liner was similar to the RSRM liner excq the ajbestcr; fibes were replaced with Snow-Tex clay (silica) and a 

difkrent thixotropic agent was used. 

The AF castable inhibitor was applied to the FSM-8 fonvad segment to dmionstrate the full-face inhibitor and 

to the aftlcenter segment, which is a short fie inhibitcx. The AF castable inhibitor was a mataial similar to the AF 

lina except forthe amcunt ofthixotrope used. 

The RSRM faward4acing inhibitor thickness was maintained even though this wtq a first time demonstration 

on B MI-sale motor. To compensate for the unproven inhibitor perfomance, the acreage insulation was increased to 

protect agrdnst inhibitor failure at motor ignition This af-feced the insulation thicknes in the acreage aras immediately 

aft of the inhibitors on the ati segment and on the aftimter segment. 

AF dhesive was prt ofthe AF baseline promses ad was also lsed for insulation iepairs. The adhesiw was 

thesame epoxy adhesiveused on the RSRM with the asbestos fibeIs being replaced with Kevlar' fibecs. The fiba 

loachng required in the epoxy wds less with the KevlarK fibers becase of their higher strength. The AF adhesive was 

used to semndarily bond several insulated components where the insulation had already been cured The insulation 

bondlines that use the asbestos filled adhesive on the RSRM werecomplcted using the AF adhesiveon FSM-8. In 

addition. the igruter nozzle w;~i apms-cud phenolic ring tha was bonded to thesteel case with the AF adhesive. 

Bondline Corrosion Corrective Action 

Originally the AF insulation design had selected a Chemlok' 205 and Chemlok' 236X as the 

adhesive/primer system tor the case to KFiEPDM insulation bondline. During subsequent process variability 

testing. indications ofcorrosion were found at the test specimen bondline. The corrosion on the specimens was 

generally accompanied by reductions in bondline strength, some of which were significant. Extensive testing was 

completed using design of experiment techniques to determine the cause of the bondline induced failures. The 

results indicated there were 6 factors that have some intluence on the bondline corrosion formation. These factors 

\vex cure temperature. cure time. Chemlok" 305 age, Chemlok" 236X age. Chemlok" 205 thickness and Chemlok' 

136X thickness. 

An additional test effort was conducted to determine corrective actions that would eliminate the corrosion 

from the bondline. Three potential corrective actions were investigated. The corrective actions were to modify the 

cure cycle, to replace the Chemlok" 236X or to modify the ChemlokR 236X by adding a Dow Epoxy Resin 33 1 

(DER331 ) additive to the Chenilok'. It was concluded from this testing, that using the Chemlok' 236X with the 

modified cure cycle was an acceptable solution to the corrosion problem. Significant corrosion reductions were 

observed at all processing variable conditions and no corrosion was seen with the nominal process conditions. It 

\vas also found that the replacement ChemlokK was clearly better than Chemlok' 236X or ChemlokN 236X/DER33 1 

adhesives for corrosion inhibition and strength. This was particularly evident for the more corrosive environment 

using 2 year-old Chemlokw 205 primer under extended cure times and at the high side of the allowable cure 

temperature range. 

The decision was made to replace Chemlok" 236X at the case to KFiEPDM insulation bondline because 

the replacement provided equal or better corrosion resistance and strength when using new Chemlok" 205. The more 

robust Chemlok " adhesive system provided by the replacement also allows greater process and material variations 

without creating bondline corrosion. This was the baseline planned for demonstration on FSM-8. 

Prior to the actual build of the FSM-8 insulated components, process simulation articles were fabricated to 

evaluate the design and practice the manufacturing processes used in this design. The process simulation articles 

were built in a normal production environment using AF production procedures and materials. Part of the normal 

procedures \vas to construct witness panels that follou. the full-scale hardware and were intended to represent. as 

close as possible. the material and bondlines that exist on the hardware. When the witness panels that represent the 

ati dome insulation configuration were tested. a shift in the bondline failure mode was noted. These witness panels 

typically fail cohesively within the insulation itself, indicating that the bondline is somewhat stronger than the 

material. However, the peel specimens indicated reduced peel strengths from what had been measured in the past 

and some failures were at the bondline rather than cohesive failures within the insulation. 

An investigation of this bondline failure mode shift was initiated since this was the first time this 

observation had been seen on the program. Further laboratory investigation of this failure mode shift revealed that 

the Chenilokh system contains ingredients that may react with moisture in a slow exothermic reaction that occurs 

above 220 OF. During the extended cure times above 220 OF that the aft dome insulation bondline experiences. the 

reaction can occur and weaken the Chemlok" to KF/EPDM bond. KFiEPDM is cold stored prior to installation, 

which can result in moisture condensation on the rubber surface. This moisture can be trapped at the insulation to 

case interface and may not be absorbed into the rubber because ofthe hydrophobic nature of EPDMs. The RSRM 

does not experience this problem. The bond strength reduction and failure mode shift were duplicated in lab 

testing. The ma,jor contributors were determined to be full-scale double cure cycles. older Chemlok' 205 primer 

and higher moisture content in the bondline. The shift does not occur for shorter cure cycles, but only occurs with 

the extended cure times associated with the double cured aft dome. The final conclusion was that a combination of 

conditions in the af dome must be present for the failure mode shifi to occur, but their occurrence was a possibility 

on a full-scale motor in the aft dome region. 

For FSM-8. a temporary solution to the problem was to install a thin ply of AS/NBR against the case and 

then vulcanize KF/EPDM to this ply. All of the bondlines that were created for this revised configuration had 

previously been tested and therefore represented an acceptable solution. This configuration had also previously been 

built on an earlier process simulation article. Other alternative solutions had not been fully developed at that time 

and any further development effort would have delayed the static test firing. 
ESE/ESD Issue and Resolution 

The AS/NBR used on the RSRM is a naturally dissipative insulation, which resists static charge 

generation. Any charge that is created dissipates throughout the insulation to the case and to a ground source. 

KF/EPDM is a very non-conductive and highly static producing insulation. This creates two major potential 

hazards during processing. The first hazard is from flammable vaporlair mixture ignition and the second is 

propellant ignition through a discharge from the insulation surface due to triboelectric charge build-up that cannot 

migrate to ground. The general approach to eliminating these potential hazards was to engineer the hazards out of 

the AF design and production processes rather than prove that the high voltage electrical charge generated during 

motor processing would not have sufficient energy to ignite vapors or propellant. 

Process materials and operations were reviewed where improvements or changes could be made to reduce or 

eliminate the ESE/ESD potential. Slowing down contact-electrification type operations controlled many ESE 

generation processes. Use of ionizers, dissipative floor mats, conductive shoes and eliminating dry wipes were 

implemented. Vapor levels present in operations involving flammable solvents were monitored to ensure 

concentration levels were below acceptable limits. Wet abrading was required on all insulation surface repairs. 

Operators were retrained in dealing with ESE hazards. Inert process simulation articles were used to test changes 

made to the processes and to monitor levels of ESE generation. These implemented changes were sufficient to 

create safe operating environments in all areas and were demonstrated by monitoring hardware and personnel. 

Other changs werc made to the engineering design. For ample, abrasion and cleaning of the RSRM field 

joints and igniter joints mating suhces wzs doneon loded segments. Testing detamined that hrasion of thee joints 

could be cmpletd on the insulated mmponents prior to loading with pmpellmt without creating a hd and uithout 

impxting the bondline strength Prior to lining, the RSRM curd internal irsulated segment is hand cleaned with a 

flammable when< which has tk potatial to create a flammable vapor/air mixture inside the segment. It was noted 

that operators do routinely contact the KFiEPDM and could geneme ESE in loalized areas. To eliminate this potential 

hazxd, another deaning solvent, which is mn-static producing and non-flammable, as tested for cured insulation and 

demonstratd on FSM-8. 

Thelargest ESEiESD conem existed tbr theexposed extemal surfaces of KFIEFDM. These surfaces are 

susqtible to contact-dectrificaticn both during plannd pmcasing as well as from incidental contact. The first 

approach to this issue was to select or devdop a static dissipaive pant that would mimic the bulk dissipative properties 

of AS:'NBR. Even though conductive pints ak used in secmal industria. an acceptdde disipative paint could not be 

fourd. Therefore, it was determined to mod@ the Hypalon' pamt used to cover the RSRM tbrwadfacing inhibitors 

and make it dissipative by using dopd semiomductor additives f?om the paint industry. Several ElectreCondudi\,e 

powders wele selected to achiew the targeted surfze resistivity. Sexml of the additives were able to initially match the 

desired surface mistivity, but the surface resistivity of each paint formulation w'ed &er acposure to humidity, 

temperature and deformations. The daa suggested that mh of these type exposures changed the spatial relatiaship of 

theconductive powder, which affected the number ofconnecting paths within the paint. Sim segment exposure to 

these conditions could mt be amtrolled, the final resistivity would vary depending on the initial resistivity and the 

deglee of ecposule to these enbironnmts. 

The solution of this issue was to make the ESE paint more conductive by increasing the concentration of 

Electro-Conductive powders in the Hypalon paint. A conductive paint complicated the processing by requiring that 

it be grounded at all times, but it allowed paint exposure to a much wider range of processing environments. The 

conductive paint was developed, tested on process simulation articles and then all live operations were monitored 

during the entire FSM-8 production process to assure safe operations. 

The ESE/ESD hazards were successfully managed for FSM-8. although most operations were much more 

complicated and required more monitoring than was desired. An effort has been undertaken to modify the 

KF/EPDM itself and make it dissipative like ASMBR. Several lab mixes of rubber have matched the ASNBR 

ESE properties. However, any modification would be best if the themial-ablative and structural material properties 

are not reduced. Combinations of conductive additives and polymer replacements have been tested. Full-scale 

production batches are planned and will be tested for acceptable material properties. 
FSM-8 Test Results 

FSM-X was successfully static tested on February 17, 2000. The post-test evaluations indicated the 

components pdhricated with AF insulation. liner or adhesives, performed as expected. Post-test inspections of the 

segments indicated no abnormal erosion or other abnormal conditions. 

i\F Irrniter Comoonents 

The AF insulation in all igniter components performed as expected and all minimum thermal safety factors 

were acceptable. Generally, the igniter AF insulation performance was equal to that ofthe baseline AS/NBR 

insulation. No abnormal conditions were found. The Material Decomposition Depths (MDDs) for the FSM-8 

igniter chamber and adapter were calculated from pre-fire and post-test insulation thicknesses. Data evaluations show 

that median MDDs for the FSM-8 igniter were slightly less than those for the FShl database tor all but two 

stations. The increased MDDs at these two stations were only slightly higher. The adapter insulation performed as 

expected. The igniter chamber outer insulation appeared nominal. The 7% KFiEPDM had a thick char cap 

remaining. The underlying KFiEPDM was intact and uniform with small bubbles in the heat affected layer. No 

anomalous conditions were noted. The AF initiator helmet performed nominally. The entire helmet was intact and 

remained bonded to the initiator chamber. Heat effects and char of the KF/EPDM helmet were typical of static 

tested motors. 

'Itin 

The performance of the AF insulation in the FSM-8 segments was as expected and no abnormal conditions 

were observed. The aft dome region of the motor experiences the most severe erosion environment. AF insulation 

had previously been tested in the aft dome of FSM-5 and some areas of severe pocket erosion resulted. The revised 

AF design on the FSM-X aft dome region. with CFiEPDM used on the flame front. indicated no abnormal erosion. 

In the aft dome region where KFiEPDM was exposed, the MDDs were equal to or slightly better than the static test 

database. Aft of station 2 15, which is near the middle of the segment, to the stiffener factory joint, the MDDs were 

slightly higher than the database. Fonvard of station 2 15. in the low exposure locations of the segment, the MDDs 

u.ere higher than the database. This may be due to different performance characteristics such as how the char layer 

was established or may have been affected by the AF liner that was also used on this segment. If the liner erosion 

were more severe for the AF liner, then the resulting MDDs would show this impact most dramatically in the low 

exposure areas. 

Erosion performance of the AF 796 KFiEPDM in the aft segment acreage areas was near the predicted 

performance. Plots ofperformance. as shown by comparing median MDDs for FSM-X aft segment versus the FSM 

static test database, are included in Figure 4. Similar observations can be made for the centeriaft segment. Figure 5 

indicates the 7O4 KF/EPDM has lower MDDs in the higher exposure region at the aft end of the segment. From 

station 40 going forward in the segment to station 275, these stations represent low exposure areas, which again 

indicate higher MDDs for FSM-X than the database. The stations forward of 275 had liner remaining post-test and 

indicated no insulation erosion. All minimum safety factors for the AF case acreage insulation were acceptable. 

AF Nozzle Hvbe Boot 

Some concern existed regarding the first-time use of 7% KFiEPDM in the nozzle flex boot. Although char 

tenacity tests had been conducted, it was still unknown how the AF insulation would perform with the standard 

nozzle vectoring duty cycle during a static test. The first 4 plies of the FSM-8 flex boot were 7% KFiEPDM and 

the remaining 3 plies were AS/'NBR. Post-test inspections of the flex boot revealed it was in good condition. Of 

the original 7 plies of insulation, the number of remaining plies was nominal and was well within the static test 

experience. All performance thermal safety factor requirements were met. 

,4F Joint3 

The aft field joint was fabricated ot'AF insulation. The joint appeared to have remained sealed during 

motor operation with no leak paths observed. The post-test inspection of the pressure sensitive adhesive applied to 
the joint mating surfaces indicated that typical bondline contact had been made. The exposed joint surfaces showed 

typical erosion. The igniter inner and oiiterjoints also performed as designed and exhibited no leak paths 

AF Liner and Castable Inhibitor 

The AF liner that remained was heavily heat-affected. but intact. and appeared to function well with no 

indication of unacceptable performance. Inspection of the acreage insulation gave no indication of liner or castable 

inhibitor failures that would result in increased erosion or might be indicated by pressure blips during motor 

operation. 

AF Forward-facinq Inhibito rs 

The AF fonvard-facing inhibitor heights were normal for a static test and indicated no abnormal areas of 

missing material. The remaining forward-facing inhibitors were measured on the aft and centeriaft segments. Both 

ofthese inhibitors were made from 7%) KFiEPDM and performed similar to the baseline AS/NBR insulation. The 

median remaining AF inhibitor heights were only slightly different than the median remaining static test inhibitor 

heights. 

1.5 

1.0 

MDD 

0.5 

FSM-8 Aft Segment 

r-tFsM.R - + - & 

0.0 30 45 50 75 90 105 120 135 150 165 180 195 210 

1 i 225 240 255 27'0 285 300 315 330 345 360 375 3% 

Station 

Figure 4 - Aft Segment Comparison of FSM-8 to Database 
a5 

a4 

a3 

a2 

a1 

0 

0 

I 

ao 

FSM-8 Center Aft 

1- FSM4 - -*- - Database 

I Station 

Figure 5 - Center/Aft Segment Comparison of FSM-8 to Database 

Real-time Instrumentation Data 

The RSRM fonvard-facing inhibitors restrict propellant surface burning on the forward face ofthe aft and 

center segments by insulating the propellant grain from the hot combustion gases, even though the inhibitors 

themsehes are thernially ablating in the severe themial environment. In the past. attempts have been made to 

predict the thermal performance of these inhibitors. However, since there is only a stub remaining for the aft joint 

and center joint inhibitors, it has been impossible to confirm the accuracy of these analyses. The FSM-8 aft and 

aftlcenter segment inhibitors were made of AF 700 KF/EPDM. These inhibitors were instrumented to obtain 

measured real-time inhibitor char line recession data for model calibration purposes and for a direct measurement of 

inhibitor safety factors. The instrumentation consisted of thermocouples and eroding potentiometers. The eroding 

potentiometer consisted of two small (3 mils diameter) twisted resistive wires that were polyimide insulated. (2) 

The wires were placed in the inhibitor during insulation lay-up parallel to the direction of erosion. During motor 

operation, the inhibitor eroded away. exposing the tip ofthe instrument to the heat of the internal motor 

environment, causing it to recede also. As the wires were heated. the polyimide insulation broke down at or near 

the tip and made an electrical junction. The electrical resistance of the wire pair decreased as its length receded and 

was measured as a function of time. Because the breakdown of the polyimide occurred near the pyrolysis/char 

interface ofthe decomposing insulation. the eroding potentipmeter measured the continuous real-time char line 

recession of the inhibitors. 

FSM-8 demonstrated the performance of the 7% KFiEPDM inhibitors in the motor environment. Realtime inhibitor eroding potentiometer and thermocouple data were successfully collected during motor operation for 

the first time on FSM-8. The comparison of the thermocouple data with the eroding potentiometer data gave good 

agreement, which indicated that the potentiometers worked well. The data showed the 7% KFiEPDM inhibitors 

performed well and there were no abnormally high char rates. The measured data verified that the thermal safety 

factors were greater than the I .S requirement for an assumed minimum inhibitor thickness. (3) 

Conclusion 

An Asbestos Free insulation design was successfully demonstrated on a full-scale Flight Support Motor. 

Major components were manufactured and shown to function well and as expected. Insulation thermal performance 

safety factors were calculated based on pre-test and post-test measurements and were found to meet all requirements. 

Several design issues were worked and acceptable solutions demonstrated. Some additional development work was 

started to make the design less complicated from a production standpoint. Further demonstration of the final design 

will be required prior to implementing an asbestos free insulation onto flight motors. 
REFERENCES 

1) 

2) 

3) 

4) 

Fitch, V. and Eddy, N.. Space Shuttle Solid Rocket Motors. Asbestos Filled Insulation Replacement, 

AIAA 97-2992 Publication. July 1997. 

McWhorter, B. B., Johnson. M. A, Bryner, B. B. and Ewing. M. E., An lnstrument for Real-time 

Measurements of Solid Rocket Motor Insulation Erosion, AIAA 99-2 I36 Publication, June 1999. 

McWhorter, B. B.. Analysis of FSM-8 Inhibitor Instrumentation Data, TWR-77 162, Thiokol Propulsion 

Publication. June 2000. 

Mossman, B. T., Bignon, J., Corn, M., Seaton, A. and Gee. J. B. L.. Ashestns: Sciciitjfic D~.~’eln~~”if~”t.s 

urd Iniplicnfioris. jiv- Pithlie Poliq?. Science, Vol. 247, pp. 294-301, January 1990. 
Aerogel Projects Ongoing in MSFC’s Engineering Directorate 

David A. Shular 

MSFC/NASA 

Mailstop: ED25 

Huntsville, AL 35812 

(256) 544-8734 (ph) 

(256) 544-0800 (0 

emai 1: T.,a \, i if. ,A . ti h 11 I Y~CI t n st;. ri ;i s ;i .go \ 

Gweneth A. Smithers 

MSFCiNASA 

Mailstop: ED34 

(256) 544-0282 (ph) 

(256) 544-7255 

emai 1: G it e nc‘t h .5 111 tjwwg; insf;:. iia b‘i. gcn 

Joel L. Plawsky 

Rensselaer Polytechnic Institute 

Troy, NY 12 180-3590 

In trod uc tion 

When we speak of an aerogel material, we are referring more to process and structure 

than to a specific substance. Aerogel, considered the lightest solid material, has been made from 

silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more 

recently. However, aerogel can be made from almost any type of substance, even lead. Because 

an aerogel is mostly air (about 99 YO). the solid substance used will affect the weight very little. 

The term “aerogel” connotes the sol-gel process used to manufacture the material. The 

aerogel begins as a liquid “sol,” becomes a solid “alcogel,” and is then dried to become an 

“aerogel.” The final product has a unique structure, usefbl for exploitation. It is an “open pore” 

system with nano-sized particles and pores, has very high surface area, and is highly 

interconnected. Besides low weight, aerogels have ultimate (lowest) values in other properties: 

thermal conductivity, refractive index, sound speed, and dielectric constant. Aerogels were first 

prepared in 193 1 by Steven Kistler, who used a supercritical drying step to replace the liquid in a 

gel with air, preserving the structure ( 1 ). Kistler’s procedure involved a water-to-alcohol 

exchange step: in the 1970’s, this step was eliminated when a French investigator introduced the 

use of tetramethylorthosilicate. Still, alcohol drying involved dangerously high temperatures 

and pressures. In the 1980’s, the Microstructured Materials Group at Berkeley Laboratory found 

that the alcohol in the gel could be replaced with liquid carbon dioxide before supercritical 

drying, which greatly improved safety (2). The most recent major contribution has been that of 

Deshpande, Smith and Brinker in New Mexico, who are working to eliminate the supercritical 

drying step (3). When aerogels were first being developed, they were evaporatively dried. 

However, the wet gel, when dried, underwent severe shrinkage and cracking; this product was 

termed “xerogel.” When the autoclave drying step was introduced, the final product was without 
cracks and showed only minimal shrinkage; this product was termed “aerogel.” In the 1990’s, 

Deshpande, Smith and Brinker developed an evaporative drying procedure in which the wet gel 

is chemically “capped” so that the material, which undergoes shrinkage, springs back to its 

original size when evaporatively dried. This new type of xerogel, while uncracked and almost 

the same size as the wet gel, differs from the autoclave-dried product in that it is less porous 

(approximately 70%, as compared to 99% for aerogels). 

The unique structure of an aerogel has suggested many diverse applications. In addition 

to the focus on superinsulation, aerogel has been considered or used in the following 

applications: catalyst support, micrometeroid capture, subatomic particle detection, impaction 

safety, desalination, toxicity sensing, acoustic and electrical insulation, and optical coatings (4, 

5). Nanocomposite work is an active area in aerogel research. Aerogels are nanomaterials 

because of their nano-sized pores and particles. When aerogels are used in composite 

manufacture, the aerogel is the substrate, to which another phase (nano or larger) is added. The 

second phase can be added during the sol-gel processing (before drying), through the vapor 

phase (after drying), or the aerogel backbone can be chemically modified through reactive gas 

treatment. 

The problem with aerogels is their low tensile strength and lack of elasticity. Therefore, 

the challenge is to find ways to make them stronger or ways to circumvent the strength issue. 

Organic aerogels have slightly higher strength than base silica aerogels, while the carbonized 

version has 3-5 times the break strength of the base aerogel. 

A standard silica aerogel has a thermal conductivity of about 17 mW/M-”K (0.00980075 

BTU-ft/hr-ft2-F). This is an order of magnitude lower than the cryogenic foams that NASA 

currently uses today. A carbonized silica has about 13 mW/M-”K (0.0075 BTU-ft/hr-ft’-F). 

These values are at atmospheric pressure. At pressures of around 50 torr, these values drop (and 

flatten out) to 8 and 4 mW/M-”K (0.0046 and 0.0023 BTU-ft/hr-ft’-F) respectively. 

The passage of thermal energy occurs in three modes, solid conductivity, gaseous 

conductivity, and radiative transmission. Solid conduction is limited due to the fact that the 

aerogels possess such a small amount of solid material. These solids consist of very small 

particles linked together in a three-dimensional network with many “dead-ends.’’ This makes 

any thermal conduction extremely ineffective. Gaseous conduction is limited by the fact that the 

gas must follow a tortuous path, and with pore sizes less than the mean free path of air, the 

gaseous molecules are more likely to impact the pore surface before they collide with another 

gas molecule. The third method of transport, radiative transmission, is the primary mode of heat 

transfer in aerogels. Basic silica aerogels are reasonably transparent in the infrared region, 

especially between 3-5 microns. At low temperatures the radiative component is not a significant 

problem. At higher temperatures, carbon can be added as an effective absorber of infrared 

radiation. 

There is work going on at NASA’s Ames Research Center, and other places, to address 

radiative heat transfer. One method involves infusion or encapsulation of the aerogel into another 

material. Ames has developed an aerogel infused AETB (Alumina Enhanced Thermal Barrier) 
tile, like what is currently flown on Shuttle, in hope of producing a single material that performs 

both cry0 and aero-heating insulation duties in a single material. 

In the Engineering Directorate at MSFC, our approach to the research and development 

of aerogel materials recognizes our relative inexperience in this technology area. We have 

chosen to partner with other NASA Centers, universities and industry to make the most of our 

mutual efforts in aerogel research. 

Composite, Cryogenic, Conformal, Common Bulkhead, Aerogel-insulated Tank 

Through award of a NASA Research Announcement (NRA), a Composite, Cryogenic. 

Conformal, Common Bulkhead, Aerogel-insulated Tank (CBAT) is being developed at MSFC. 

The CBAT team includes engineers fi-om the Structures, Mechanics & Thermal Department 

(S,M & T) and the Materials, Processes & Manufacturing Department (MPM). Thiokol and 

S\.erdrup also provide engineering support. This work is funded as a next generation RLV 

project. The intended propellants are liquid oxygen (LOX) and high-grade kerosene (RP); 

however, liquid nitrogen and water will be used to test this subscale tank. The tank will contain 

enough propellant to fire the Fastrac engine for 15 seconds. Tank pressure and compressive 

loads will also be based on the Fastrac engine. Aerogel insulation is being used at two locations: 

in the common bulkhead area (between the LOX and RP tanks) and around the skirt that 

surrounds the two tanks. 

We explored a number of aerogel possibilities for the common bulkhead area. At the 

current time, Nanogel Th' (an evaporatively dried, silica-based xerogel which has been powdered 

and compressed, with additives, into a near monolith) is our baseline component. For testing, 

we obtained 8-inch diameter, - inch thick disk samples of Nanogel TM from Nanopore, Inc. in 

Albuquerque. The ASTM procedure for thermal conductivity testing requires samples of this 

size and shape. Because of the loads which will be experienced by the xerogel when the tank is 

pressurized, we asked Nanopore to compact this material at 75 psi, instead of 15 psi which is 

standard practice. Nanopore normally seals the material under a slight vacuum with a 

metallized, plastic laminate wrapper. We requested three types of samples: vacuum-sealed with 

air; sealed without vacuum; and krypton filled, sealed without vacuum. We also obtained one 

sample (vacuum-sealed with air) which was compacted with the standard 15 psi. The 75 psi 

samples were tested for thermal conductivity and compression strength. The 15 psi sample was 

tested for compression strength only. The results of these tests are shown in Tables 1 through 3 

and Figures 1 through 4. Since the vacuum-sealed sample should insulate better than the 

Krypton-filled sample, we believe the vacuum-sealed sample may have lost vacuum. Attempts 

to perform thermal conductivity testing at cryogenic temperatures were not successful. The 

Holometrix Micromet Model GHP-200 employed was designed for higher temperatures. We are 

currently making plans to perform cryogenic testing of these samples at another facility. 

Thermal conductivity testing was performed by Scott Taylor of ASRI; he used ASTM Method 

C- 177, Standard Test Method for Steady-State Heat Flux Measurements and Thermal 

Transmission Properties by Means of the Guarded-Hot-Plate Apparatus. Compressive fatigue 

testing was performed by Andrew Hodge, MPM Department. 
In cooperation with Dr. Susan White at NASA's Ames Research Center, we are also 

pursuing an alternative type of aerogel for the common bulkhead area. NomexT" honeycomb 

was cut into &inch disks here at MSFC, and subsequently shipped to Ames. In Dr. White's 

laboratory, an organic aerogel, formulated for compatibility with the honeycomb material will be 

used to fill the honeycombs, which will then be supercritically dried in an autoclave. These 

samples will be shipped back to MSFC for testing. 

Around the skirt, we plan to install an aerogel blanket system. Because of his experience 

with aerogel blankets, we asked Mr. James Fesmire of Kennedy Space Center to assist us in this 

effort. The insulation system will include a Teflon-coated fiberglass cloth (beta cloth) on the 

cold side, an aerogel composite blanket (from Aspen Systems in Boston), and SilverluxTM film 

on the warm side. We are currently devising a mechanism by which CBAT team members at 

MSFC and Cryogenic Testbed personnel at KSC can exchange services in a way that is 

beneficial to both Centers. 

Xerogel Optical Toxicity Sensor 

Because of his expertise in aerogel materials, Dr. Joel Plawsky, a professor at Rensselaer 

Polytechnic Institute, was invited to spend the summers of 1999 and 2000 as a Faculty Fellow in 

the MPM Department at MSFC. Our awareness of the environmental and safety issues 

associated with the standard autoclave procedure used in production of aerogel and our study of 

recent advances in elimination of the autoclaved, supercritical drying step, led us to pursue, with 

Dr. Plawsky, aerogel production which employed evaporative drying rather than autolcave 

drying. This work, performed in 1999, laid the foundation for work performed in 2000 to 

develop an optical toxicity sensor. 

Our goal during the summer of 1999 was to determine if the evaporative drying step used 

for thin-film aerogels in Dr. Plawsky's lab at RPI could be adapted to produce thicker, 

monolithic aerogels. Tetraethoxysilane (TEOS), ethanol, water, and hydrochloric acid were 

mixed and heated for 90 minutes. Acid catalysis promoted hydrolysis of the TEOS and initial 

polymerization. The precursor sol was then mixed with a solution of ammonium hydroxide. At 

room temperature, base catalysis promoted branching and crosslinking of the sol leading to gel 

formation in about 40 minutes. The wet gel was aged in a two-step process, performed at room 

temperature. In the first step, the gel was placed in a solution of ammonium hydroxide and 

ethanol, where it remained on a shaker table for 24 hours. The gel was then rinsed in ethanol and 

immersed in a solution of TEOS and ethanol. The gel was then aged from 24 to 72 hours at 

room temperature. Following this step, the gel was thoroughly rinsed in ethanol. Afterwards, 

the gel was immersed in hexamethyldisiloxane (HMDSO), and the capping agent was slowly 

added to yield a 10 mole% solution of trimethylchlorosilane in HMDSO. Gels were allowed to 

sit in the capping solution for 24 -48 hours on the shaker table. Subsequently they were flipped 

and immersed in a new solution to ensure complete treatment. After capping, the gels were 

washed in HMDSO again before drying began. Initial experiments drying the gels at room 

temperature failed. Eventually, the procedure was modified and resulted in successhlly dried 

gels. The gel was placed in a closed petri dish (2" in diameter) which was drilled with a 1/16" 

hole at the top. The gels were placed on x-shaped teflon supports to elevate them from the 

bottom surface of the dish and remove any capillary suction there. This allowed the gels to 
expand and contract freely during drying. The petri dishes were set on a hot plate, on top of a 

crucible insulator, and covered with a 600 ml fritted glass filter. The filter controlled the 

evaporation rate and kept the draft from the hood away from the specimen. Depending on the 

sample, drying took from 3 to 24 hours. Samples produced were 1/8” thick. 

Aerogels exhibit high surface area, stability, and transparency. They can easily transport 

gases and can be filled with other phases. These properties make aerogels well-suited for use in 

optical sensors. When Dr. Plawsky returned to MSFC in the summer of 2000, we began work on 

a toxicity sensor which might have application in a closed-system situation like Space Station, 

where toxic chemicals must be monitored at a highly sensitive level. Figure 5 illustrates the plan 

for this sensor. Our plan for the summer was to continue development of various types of 

aerogel using the manufacturing procedure developed during the previous summer. These 

aerogels would be candidates for the layer that covers the waveguide. The waveguide element 

of this device is being developed at RPI by Dr. Plawsky and his graduate students. The aerogel 

or xerogel material forms the cladding of an integrated optical waveguide. The core material can 

be made of anything that has a higher refractive index than the xerogel and that the xerogel will 

adhere to. The xerogel component acts as the sensing element of the device since it can contain 

organic functionality that will interact with materials in the atmosphere. These are absorbed into 

the xerogel, changing its optical properties. The changes are read by the waveguide either as a 

change in the propagation characteristics of the waveguide or as a change in the intensity of the 

light as it passes through the waveguide. The sensitivity of the device comes from the great 

surface area of the xerogel and the large optical interaction length of the waveguide. At this 

writing, we are completing manufacture of these types of xerogels at MSFC. Two are hybrid 

silica-titania and silica-zirconia gels. These materials can be used as oxidation substrates for 

destruction of volatile organic compounds (6) in spacecraft. The high surface area of xerogels 

makes them well-suited for making compact chemical reactor systems (7). We are also making 

organic/inorganic hybrid xerogels with amino, mercapto, cyano, and saturated hydrocarbon 

functionality. Amino functional groups can be used to absorb and sense acid vapors, mercapto 

groups are useful for incorporating metals into the gels and using the metals as sensing elements, 

cyano groups are reactive functional groups to acidic and basic groups and the hydrocarbon 

groups are meant for absorption of nonpolar organic constituents. In addition, the amino and 

cyano groups can also be used to immobilize enzymes or antibodies into the gels for biological 

operations (8). In all cases the interaction of the compound of interest with the functional groups 

in the xerogel changes the optical properties of the xerogel and provides for the sensing function 

when the xerogel is used as a cladding for the optical waveguide. 

Thermally Integrated Structures 

Thermally Integrated Structures (ThIS) are a long-term goal at MSFC. NASA needs a 

reusable launch vehicle (RLV), single-stage-to-orbit, which utilizes liquid oxygen/liquid 

hydrogen chemical propulsion. To attain this goal, vehicle mass fraction must be high, 0.9 or 

greater. Vacuum specific impulse must be maximized, but realistically will be limited to - 460 

seconds. The vehicle should look and operate as an aircraft. Vehicle volume must be reasonable 

to enable handling and operability. 
A major difference between aircraft and RLV’s is the “use temperature” of major 

structures. RLV aerodynamic surfaces can be exposed to environments resulting in surface 

temperatures up to 1800°F (leading edges, up to 3000°F). These hot surfaces must be noncatalytic. Cryogenic tankage will be exposed to 420”F, and must be compatible with liquid and 

gaseous oxygen and hydrogen. Heat leakage through the structure must be small. No 

cryopumping within the structure can be tolerated: the structure must be impermeable. The 

system must be durable. easily weatherproofed, lightweight, manufacturable and maintainable. 

It must have low operational costs. Material systems must be manufacturable in large sections. 

Joining and attachment techniques must be easily implemented. 

Like aircraft, our current design approach includes use of lightweight materials of 

construction. Unlike aircraft, we add a Thermal Protection System (TPS) and cryogenic 

insulators to enable use temperatures for these structures. These additions add weight and cost, 

while reducing operability. These systems also add complexity in the area of attachments and 

add requirements such as allowable bond-line temperatures, complicating the design problem. 

Estimates of RLV GLOW have indicated that this design approach, with these materials 

of construction and LOX/LH2 propulsion, does not meet SSTO feasibility requirements (mass 

fraction at an operable vehicle volume). Graphite-epoxy dry structures and integral cryotankage 

were thought to offer weight efficiency sufficient to enable SSTO, but if current RLV estimates 

derived from X-33 experience do not enable SSTO, then alternate approaches must be 

considered. One promising technology for RLV is advanced and integrated fundamental 

materials of construction for airframe and cryotank structures. We want to investigate feasibility 

of development of lightweight Thermally Integrated Structures with a large range of operating 

temperatures, and low heat transfer through the thickness of the material system. 

The weight of such a material system must be significantly less than standard designs 

(which use lightweight materials with lightweight cryogenic insulators and TPS materials. For an 

investigation like this, we are considering a titanium honeycomb (use temperature - 1200F) 

filled with a high temperature aerogel. Very low heat transfer from face to face would be the goal 

of such as system, with all materials capable of withstanding both cryogenic to aero entry use 

temperature, as well as temperature gradients across the structure. Life should be at least 100 

thermal/structural cycles. Manufacturability in very large sections is a key to operability. A 

severe limitation in the areas of cost and operability for current TPS material systems is the need 

to attach thousands of piece parts to very large structures. 

The Thermodynamics and Heat Transfer Group in the Structures, Mechanics &Thermal 

Department (SMT) at MSFC have prepared a computational model which employs a titanium 

honeycomb core utilizing solid fill carbon aerogel. The facesheets are aluminum on the inside 

surface and titanium on the outer surface. The core dimensions consist of 318” diameter centers 

with a wall thickness of 0.005”. The baseline design is for a 1” thick panel with counterbores of 

2” diameter and 3/8” deep. The counterbores are oriented such that there is a slight overlap in 

order to provide a design in which there is no direct conduction path through the thickness of the 

panel. In the actual panel to be constructed, the counterbores will probably be square such that 

the edges can be aligned in order to ensure that there are no gaps created by the overlying circles 

which might allow for a more direct conduction path. Several densities of carbon aerogel have 
been considered in an attempt to learn which density may be the best choice. According to the 

literature from the national labs, radiation is the primary mechanism of energy transport at 

elevated temperatures for generic aerogels; the solid conductivity is small in comparison. 

1 lowever, since this design is a closed system with direct contact among all materials (and the 

added carbon is an infrared absorber) conduction has been the primary focus. Property data is 

still being collected. The SMT and the MPM Departments are writing proposals and actively 

seeking funding for Thermally Integrated Structures projects. 

Table 1. Apparent Thermal Conductivity of NanogelTA’TI-6000, 800 mbar abs. No Vacuum 

Snniplc Positiori 

Top 

Bottom 

Thickricw (ttim) Dinmeter (nint) MlN (g) Detisio- (kg/ni ’) 

13.20 203.20 96.20 224.73 

1330 203.20 94. 10 2 10.27 

Aftwi TcmpcwrtiircJ. Drgrres C‘ (Deg F) 

4.2 (39.6) 

4.2 (39.6) 

9.4 (49.0) 

9.4 (48.9) 

18.4 (65.1) 

IX.4 (65.2) 

35.1 (95.1) 

35.0 (95.0) 

56.4 (133.5) 

60.2 (140.3) 

Appuretit Thrr-mil C’oridircriiiti~. W/mK 

0.01 6466 

0.0 I6826 

0.017191 

0.0 I7326 

0.0 I8205 

0.0 18246 

0.0 19066 

0.0 18990 

0.020265 

0.020675 

Su niple Posit ioti Th ich c~ss (miir) Diameter. (tntii) ,bfll.s.s Ig) 

Top 12.50 203.20 97.80 

Bottom 12.40 203.20 94.50 

Densig- (kgini ‘) 

24 I .26 

235.00 

13.8 (57) 

I X.3 (65) 

32.8 (91) 

477(1IX) 

0.0 12672 

0.012885 

0.013585 

0.012485 

Snmplc Position 

Top 

Rottom 

Thicknrss (mni) Diameter (mni) Muss (g) Densiti. (kgh ’) 

12.80 203.20 96.90 233.44 

13 70 203.20 99.40 223.73 

Alcwti Tiwiptwrtiire. Degrt~cs c‘ (Deg F) 

1. I (34) 

6.1 (43) 

21.7(71) 

32.X (91) 

Ap,wrrti~ Tliimiul Conduct1 1’1 119, W/ni K 

0.0 102 16 

0.01 0266 

0.01 1066 

0.012039 
0 500 I000 I500 2000 2500 3000 3500 4000 

Time (Seconds) 

Figure 1. Compressive Fatigue Test of Xerogel Disk (75 psi, No Vacuum) 

0.2 

0.18 

0. I6 

0.142 u 

S u 

0.12 E 

0.08 g 

3 

‘2 m - 

0.1 9 

6 

0.06 

0.04 

0.02 

0 

140 

I20 

100 

- - 

W 

E 80 

g 

4 I / 

g 60 

40 

20 

0 

07 

0.18 

0 I6 

0.14 

012 

01 :: 

- 

f 

E 

- 

0 

- cf 

008 ; 

0 06 

0 04 

0 03 

0 

0 500 1000 1500 2000 2500 3000 3500 4000 4500 

Time (Seconds) 

Figure 2. Compressive Fatigue Test of Xerogel Disk (75 psi, Vacuum) 
I30 + Pressure 

I20 

I 00 

40 

20 

0 

LVDT Displaceinent 1 -2 0.18 

0 500 1000 IS00 1000 2500 3000 3500 4000 3500 

Time (seconds) 

0.16 

- 0.14 

S .- - 0.12 E 

Y 

0.1 8 

a 

=: 

- d 

0.08 5 

0.06 

0.04 

0.02 

0 

Figure 3. Compresive Fatigue Test of Xerogel Disk (75 psi, Krypton Filled) 
I40 

+ Pressurc psi 

I20 

-1 

40 

20 

0 

0 500 1000 1500 1000 2500 3000 3500 4000 4500 

The (seconds) 

Figure 4. Compressive Fatigue Test of Xerogel Disk (IS psi, Vacuum) 

0.2 

0.15 

0. I 

0.05 

0 

-0.05 

!- 

a 

> 

4 
Templnted Nanoporous 

Srrogel 

Figure 5. Xerogel Sensor Concept 
References 

I. S. S. Kistler, J. Phys. Chem., 33, 52 (1932). 

2. Berkeley National Laboratory web site. 

3. R. Deshpande, D.M. Smith and C.J. Brinker, US patent application (1992). 

4. L. W. Hrubesh, Aerogel Applications, J. NonCryst. Solids, 225, 335, (1998). 

5. Pacific-Sierra Research web site. 

6. L.M. Hair, Coronado, P.R. and Reynolds, J.G. Mixed-metal Oxide Aerogels for Oxidation of Volatile Organic 

Compounds, J. NonCryst. Solids, 270, 115, (2000). 

7. A. Sayari, Catalysis by Crystalline Mesoporous Molecular Sieves, Chemistry of Materials, 8, 1840, ( 1996). 

8. M.A. Doody, Baker, G.A.. Pandley, S., and Bright, F.V., Affinity and Mobility of Polyclonal Anti-Dansyl 

Antibodies Sequestered within Sol-Gel Derived Biogels, Chemistry of Materials, 12, 1 142, (2000). 

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P 
Advanced Engineering Environments - 

Implications for Aerospace Manufacturing 

Dale Thomas, Ph.D., P.E. 

NASA Marshall Space Flight Center 

Mail Stop VS IO 

Huntsvillc, Alabama 358 12 

Telephone: 256-544- I 180 

Email: dale.Thomas@msfc.nasa.gov 

ISTKODLC'TION 

There are significant challenges facing today's aerospace industry. Global competition, more complex 

products, geographically-distributed design teams, demands for lower cost, higher reliability and safer vehicles. and 

the need to incorporate the latest technologies quicker, all face the developer of aerospace systems. New 

information technologies offer promising opportunities to dcvclop advanced cngineering environments ( AEEs) to 

meet these challenges. Significant advances in the state-of-the-art of aerospace engineering practice arc envisioned 

in the areas of engineering design and analytical tools, cost and risk tools, collaborative engineering, and highfidelity simulations early in the development cycle. These advances will enable modeling and simulation of 

manufacturing methods. which will in turn allow manufacturing considerations to be included much earlier in the 

system development cycle. Significant cost savings, increased quality, and decreased manufacturing cycle time are 

expected to result. 

This papcr will give an overview of the NASA's lntelligent Synthesis Environment. the agency initiative to 

dcvclop an AEE, with a focus on the anticipated benefits in aerospace manufacturing. 

BACKGROUND 

The development of aerospace systems has historically been a costly and time-consuming endeavor, 

particularly so for the systems developed for NASA missions. To illustrate, consider that the Apollo Saturn V 

launch vehicle required X years to develop (through first launch) at a cost of -$5B, while the Space Shuttle required 

1 I years to develop at a cost of -$11B; the unmanned Ariane V launch vehicle required 10 years and -$7B to 

develop (all costs reflect actual year dollars). It should also be noted that the Ariane V may be considered to be an 

evolutionary development of the Ariane IV, otherwise the time and cost to develop would have been greater. A 

space transportation system typically includes a launch vehicle, a spacecraft, a ground launch processing 

infrastructure. and a mission operations infrastructure. Each of these component systems represents a significant 

development effort in its own right: developed in conjunction, the complexity of the development only increases. 

In planning for the next generation of aerospace systems, NASA has chosen to focus on the life cycle cost 

of the system. In the case of a space transportation system, this would include a launch vehicle as well as its 

associated system components. The costs include the amortized cost to develop, the fabrication costs of the launch 

vehicle, and the development and operations costs of thc associatedisupport systems. The operations costs are not 

negligible, even when compared to the significant development costs given in the foregoing paragraph. Consider 

that - 140,000 direct labor hours are required to process the Space Shuttle between flights, excluding propulsion 

elements and any servicing required on the launch pad. Hence, clcarly all elements of the life cycle must be 

considered in development of any future space transportation systcm. 
C L’ R RE N T S 1’ ST E M DE \7 E LO P RI E I\; T EN \ ’ I R 0 N Rl EN T 

KASA aerospace systems are typified by small production lot size, complex architecture, and relatively 

little design heritage. Attempts to utilize legacy parts in a new design often result in spectacular failures. as 

cvidenced by the failure of the inaugural launch of the Ariane V. (Glcick) In this instancc, an Arianc 1V 

subassembly and associated software used within the Ariane V Guidance, Navigation, and Control subsystem 

functioned per Arianc I\’ specification. but in a mode inconsistent with the Ariane V design. This subtle functional 

characteristic was not detected in the Arianc V qualification testing. As is commonly the case in complex systems 

including software, system testing can catch only the anticipated failure modes. 

These development challenges are exacerbated by the nature of the development team. The development 

team typically consists of a systems integrator and many component vendors; the development team itself is usually 

dispersed across a large geographical area, often across international boundaries. Furthermore, the development 

team is rarely located proximate to the customer. When the complexity of the system development is considered, 

thc communications problem becomes evident. Since the quality of any system engineering task depends on 

technical communication, the difficulty of system engineering grows as a function of geographical dispersion. Also, 

as the quantity of embedded software in today’s systems grows. the system engineering challenge grows. Indeed, 

the Ariane V failure discussed in the foregoing paragraph has been attributed to poor system engineering. (Gerard, 

1997) Likewise. failures in recent NASA missions have cited poor system engineering as a root cause. (McDonald, 

Spear, Stephenson, Young) 

While advances in information technology havc led to significant advances in engineering tools and 

infrastructure, engineering processes have remained largely unchanged since the days of drafting tables. The current 

engineering life cycle of a space transportation system is illustrated in Figure I; this life cycle may be considered 

typical of the aerospace system life cycle. This traditional process is largely sequential in nature, usually requires 

long development times. and does not easily integrate customers and suppliers into the design process. Furthermore, 

following traditional design practices, approximately 90% of the total cost of an aerospace vehicle is built into the 

design in the first 10% of the development cycle. Unfortunately, the total cumulative knowledge of the design is still 

very low at this point, about I5-20% of the knowledge available at the end of the development cycle. 

Efforts to accelerate the development cycle within NASA, commonly referred to as “Faster, Better, and 

Cheaper.” have met with limited success. While in many cases the developmcnt cycle time and cost havc indeed 

decreased, the mission succcss rate has likewise decreased. (Dickey) Given that the overall engineering process 

remains fundamentally unchanged. complex systems remain exceptionally expensive and time consuming to 

develop. as the quantum improvements in efficiency and quality that are characteristic of information technology 

applications in general havc proven elusive. 

ADVANCED ENGINEERING ENVIRONMENTS 

Let the engineering environment be defined as the processes, tools. and infrastructure used by people to 

engineer systems. Here the engineering process describes the structured methods and procedures by which a 

complex system evolves through the conceptual definition, design, manufacture, integration and testing, and 

delivery for operations. The tools consist of hardware devices and software codes used by engineers to perform the 

various component tasks comprising the engineering process. The infrastructure is commonly described as the 

“physical plant’’ including office space, thermal vacuum chambers, etc. but has come to include the data networks 

and other elements of a computational and communications infrastructure. 

AEEs are defined as particular implementations of computational and communications systems that create 

integrated virtual and/or distributed environments which link researchers. technologists, designers, analysts, 

manufacturers. suppliers, customers and managers involved in mission-oriented. leading-edge engineering teams 

comprised of industry, government, and academia. (NRC) 
Development @$- Development Testing 

Assembly 

Verffiration 

lntegrntion / O&M 

>”% &I Xp1’W6*8*n 

Training 

..... _.__.____._____._ .......... ... _.....__. ..... 

F:xetotive Mrnagrment. Evrloation. Safety, Finance, I.egaL Regulatory. Penonael. PR. 1.ogistics. Sopply Chain MgC. Projecl Me.. Of, FsdliriPs 

Figure 1. Current Life Cycle 

THE INTELLIGENT SYNTHESIS ENVIRONMENT USE) CONCEPT 

To meet NASA’s unique needs the future product and mission development environment must 

accommodate different groups of people, such as engineers, designers, scientists and technology developers. These 

groups must be able to work together eollaboratively, and must also be able to integrate both customers’ and 

suppliers’ requirements into the process (Goldin. Goldin, Noor). These diverse teams will collaborate in utilizing 

new computational resources in innovative and meaningful ways. Teams will not be in one location, so the design 

environment must support collaboration of geographically distributed teams. Computational tools that are utilized 

within this environment must be easy and intuitive to use, and make use of a balanced mix of multi-sensory 

technologies. The design environment must allow scientists to interact with simulated vehicles and missions so as to 

study science payload, mission performance and interaction of science requirements with vehicle and mission 

engineering. Ultimately, this environment should be usable by engineers, scientists, operators, program sponsors, 

and stakeholders. 

Therefore, the vision of this new design and mission synthesis environment is: 

To e@[ o cultural change Ihal iiitegt-cites iiito prrrctice wideli. distribiilcd srieiicc. technolo&? arid 

cngirieering team IO rapidlj- create innovative. affbrdahle products. This is ucconiplished hj. 

using n ccrrnhirintiori of‘ technologies io huild,~n.s.senihle an in tegia tcd /iitelligent S?mllre.sis 

Eiivir-onnieiil (HE), jbr creative engirieering nnd science. 
ISE: A NEW NASA INITIATIVE 

In order for NASA to meet its unique mission needs in space science. human exploration, earth 

science and aeronautics, NASA proposes a new Initiative to develop an Intelligent Synthesis Environment 

(ISE). ISE will utilize computational intelligence to synthesize existing, newly developing and future 

relevant technologies to provide the future product and mission development environment. In the ISE. 

synthesis takes place in three ways: 

Collaborative synthesis of scientists, engineers. technology developers, operational personnel 

and training personnel all working in geographically, as well as temporally, distributed locations; 

Synthesis of cutting-edge technologies and diverse, life cycle design tools seanilessly integrated 

together both horizontally and vertically at all levels of fidelity: 

Synthesis of humans, computers, intelligent hardware (e.g.. robotics) and the synthetic (virtual 

reality) simulated designs and design languages. 

The intelligent nature of ISE is derived from its concentrated use of non-traditional, intelligent 

computational systems such as intelligent product objects. intelligent agents and intelligent computational 

methods. The computational intelligence. which will be built into the design environment, will guide the 

utilization of the vast rcsourccs of knowledge and predictive capability to which the environment will have 

access. 

Very importantly, the ISE program will make meaningful use of related developments sponsored 

by other government agencies and industry. This will be accomplished through the use of R&D ISE 

laboratories in which technologies from government, industry and universities will be synthesized, 

assessed. validated and demonstrated. To this end, NASA will form partnerships and coalitions with other 

government agencies, the software vendor industry, aerospace and non-aerospace industries and 

universities. In addition, ISE Large-Scale testbeds will be created to apply new ISE products to engineering 

projects and science missions of importance to NASA. These testbeds will be distributed geographically 

and will be reconfigurable to meet new requirements as these are identified. They will provide a showcase 

for demonstrating how state-of-the-art cotnputational and communication facilities and tools can be 

synthesized with engineering, science, manufacturing, operations and training teams to dramatically 

improve productivity, enhance creativity and foster innovation at all levels of product and mission 

development. 

THE ISE IN PRACTICE 

The ISE Initiative will develop, validate, assess and demonstrate, through ISE Largescale 

Applications, a revolutionary product and mission development environment which synthesizes existing. 

newly developing and future relevant technologies to provide the future environment for collaborative 

science, engineering. designing, manufacturing, certifying, operating and training. Such an environment 

will revolutionize design so that the conceptual, preliminary and detailed design phases merge, therefore 

dramatically shrinking the design cycle. Products and missions will be rapidly configured and assessed for 

scientific payoff or product performance leading to innovative and creative design solutions. Production, 

operations and training issues will be addressed early, and costs and risks accurately predicted and 

draniatically reduced. Redesign and manufacturing rework costs will be virtually eliminated. Certification 

testing requirements and costs will be dramatically reduced. In total, ISE will result in significant increases 

in productivity, affordability and performance. 

Thc ISE is a comprehensive, completely integrated environment. It provides a holistic view ot' the 

product development process. It addresses the entire mission and life cycle of the aerospace system. It 

makes effective use of intelligent agents to increase the creativity bandwidth of the science and engineering 

teams. CEC's will be assenibledibuilt to demonstrate the ISE concept, and to help in identifying technology 

developments needed for realizing its full potential in large-scale science and engineering applications. The 
tcstbeds will be re-configurable, and will rapidly accommodate new synthesis paradigms as neu' 

technologies develop. 

SPACE TRANSPORTATION SYSTEM DEVELOPMENT IN AN AEE 

To illustrate the ISE concept of an AEE, consider the development of the NASA Spaceliner 100. 

(Lyles) The process of developing and deploying this vehicle is in its earliest stages such that the AEE can 

be illustrated throughout the full life cycle. Following are the primary goals for the vehicle: 

Increase Crew Safety 

111 .000,000 probability of crew loss 

Increase over current crew safety by a factor of over 10,000 

Increase Vehicle Reliability 

111,000,000 probability of vehicle loss 

Increase over current reliability by a factor of over 10,000 

Lower launch vehicle costs 

$100 per pound to LEO 

Decrease current costs by a factor of 100. 

The following paragraphs very briefly discuss the derivation of AEE tunctional requirements based on 

these Spaceliner 100 goals. 

Orders of magnitude of vehicle endurance improvement are required. Specifically, the vehicle 

must turn out to be about 10,000 times more reliableisafe than the baseline vchiclc - the Space Shuttle. 

This will require a combination of dramatic improvements involving principally materials and structural 

design - focused on increasing the overall fatigue life of the vehicle system, subsystems, and components. 

This focus will affect the conceptual through detailed design phases, as well as the manufacturing!' 

production phases. Thus, in order to support this focus, the AEE must facilitate design, materials selection. 

and loading simulation, and the AEE must facilitate the application of performance and fatiguc life 

prediction tools at the vehicle system, subsystem, and component levels. This must include a probabilistic 

design approach that will provide multiple design alternatives, which will foster the understanding and 

reduction of risk, sensitivity and uncertainty. The AEE must enable and facilitate the prediction of 

performance and fatigue life at a level of accuracy far improved over such predictive capabilities as were 

available at the time of the Shuttle design. (Note, for example, that the Shuttle design plan predicted that 

the main engines would have to be removed and refurbished only after _20+ flights. As it turned out. they 

must be removed and refurbished after flight ~ and at great cost.) In addition, the AEE must facilitate 

integration of comprehensive safety considerations and the "ilities" into the overall process and in all 

supporting subprocesses, as well. 

The Spaceliner 100 goals require two orders of magnitude reduction in vehicle life cycle costs, 

with specific emphasis on the operations phase of the life cycle. Vchicle delclopnierit cost is highly 

dependent on the overall length of time taken to complete the development. (The standing army of 

dei,elopers generally stays on thc payroll throughout this length of time.) Thus, the AEE must provide 

methods and capabilities to acceleratc the overall development process. A proposed, future, AEE-enabled 

engineering life cycle process is illustrated in Figure 2. This process utilizes state-of-the-art information 

technology to significantly reduce the vehicle development cycle time while simultaneously increasing the 

quality and thoroughness of the system engineering process as measured by increascd system safety and 

reliability. The derived requirements for this AEE arc further described in three paragraphs that follow. 

Subsequently, the AEE architecture will be described. 
MarketKustomer 

Requirements 

r 

I 

Testing Deployment & Distributbn I 

Integration t 

Verification 

Pcrsunnel, PR. Logi 

Figure 2. Future Life Cycle 

O&M 

Vehicle ilt~i~t~lopt~irtzt (and ultimately operations) costs are principally driven by the decisions 

made in thc conceptual and preliminary design phases. These decisions arc based on lessons lcamcd and 

particularly on the results of iterative rules-based design analyses. Vehicle perfonnance and endurance 

capabilities are predicted based on anticipated loadingiduty cycle/etc. These decisions include tradcs 

relativc to utilization of actual and planned technology capabilities, such as materials performance 

characteristics. The speed at which these decisions can be made is dependent on thc speed at which the 

computationally intensive iterations can occur in converging to a satisfactory design plan. Thus, in order to 

shorten the design phase while improving the quality of the outcome, the AEE must facilitate: rapid access 

to lessons learned and corporate knowledge, seamless integration of designianalysis tools, rapid completion 

of design and analysis stepsiiterations, rapid insertion of alternative; improved analysis tools, and 

intelligent selection of neededicompatible tools and techniques. These AEE-provided capabilities will 

require (and enable) a substantial accompanying process change from that of today sincc information 

derived in one process step/iteration will be immediately and seamlessly available as inputs for other 

process steps'itcrations. This process change will enable the capability for essentially real-timeiparallel 

processing among the engineering and analytical disciplines. To fully cnablc and implement this 

parallclism, thc AEE implementation must facilitate integration of the people which support the 

engineering and analytical subprocesses. They must be trained to work in an environment that does not 

includc tlic long periods of time -waiting for computations to complete, waiting for a colleague or supplier 

to finish a step. etc. ~ as is characteristic of current design environments. 

The conceptual AEE architecture employs a building block approach to achieving the required 

AEE end-product capabilities. As shown in Figure 3 the blocks are analogous to the International 

Organization for Standardization (ISO) Open Systems Interconnect Model. Infrastructure blocks support 

tool and application blocks, and the aggregate of the blocks will be assembled within the architecture for a 

transportation vehicle - nominally the Spacclincr 100. It is noted that this architecture is readily applicable 

for the requirements of the other space transportation systems. The architecture provides these highlights: 

On-lineirapid connectivity and collaboration within MSFC and between MSFC and its supporting 

contractor, academic, and supplier communities. This enables the parallcl processing required for 

shortening design cycles and/or enabling larger numbers of analysis iterations. 

On-lineirapid connectivity and collaboration between MSFC and the NASA Centers of 

Excellence. This enables MSFC organizations to expand the rapidiparallel processing capability 

to includc Programs and Projects at the other Centers. This c.x-tei.tiul connectivity and 
collaboration is planned to be facilitated by tlic NASA Intelligent Synthesis Environment (ISE) 

Program. The AEE requirements in this regard will be developed to ensure MSFC’s iiircrml 

processes, tools. and infrastructure evolvc to be compatible with the ISE. 

Tools integration and process automation environment. This enablcs the engineers and analysts to 

utilize the best tools available for each discipline in a plug-and-play environment. It also enables 

definition of multi-discipline analyses and optimization processes for automated solution 

convergence/ closure. 

NASA, Government, Academia, Industry 

Transportation, Science, Space Products, 

Propulsion Microgravity, Optics 

MSFC 

A Space 

Figure 3. AEE Architecture 

IMPLICATIONS FOR AEROSPACE MANUFACTURING 

The NextGeneration Manufacturing Project (bGM) was initiated in I995 to dcvclop a framework 

for action that manufacturers can use to chart a course for success in an increasingly complex and 

competitive global environment. The NGM Project idcntified three high-leverage technology-related 

imperatives within an overall set of ten generic enabling practiccs and technologies deemcd critical for 

NGM success: 

Pervasive Modeling & Simulation, 

Adaptive, Responsive Information Systems. 

Next-Generation Manufacturing Processes and Equipment, 

Of these three imperatives, the second - Pervasive Modeling & Simulation, is most directly aligned with 

the goals and objectives of the Intelligent Synthesis Environment. 

“In the NGM Enterprise. modeling and simulation (M&S) will reflect a new way of 

doing business rather than a supporting technology. It will make virtual production a 

reality. All production decisions will be made on the basis of modcling and simulation 

methods, rather than on build-and-test methods. M&S tools will move from being thc 

domain of the technologist, to being a tool for all involved in the product realization, 

production, and business processes. M&S will eliminate the need for developing 

hardware prototypes and allow for lot sizes of one. This will dramatically decrease time- 
to-market for new products and services. It will provide products and services optimized 

for the customer and other stakeholders. It will require significantly fewer resources in 

the development process than build-and-tcst methods” (NGM) 

Clearly. the inclusion of manufacturing M&S within the overall aerospace system development process 

will enable the consideration of manufacturing tradcoffs including the plant, the equipment, and the 

production processes at a much earlier point in thc systcm design process than is typical today. 

Furthermore. this earlier inclusion of manufacturing considerations will include a higher degree of fidelity, 

enabling manufacturing plans to more appropriately influence the system design. 

REMARKS 

Today, the developer of an aerospace system is faced with more complex products, 

geographically-distributed design teams, demands for lower cost, higher reliability and safer vehicles. and 

the need to incorporate the latest technologies quicker. Within NASA, multiplc technology development 

and demonstration projects are underway toward the objectives of safe, reliable, and affordable access to 

space. AEEs incorporating new information technologies offer promising opportunities to meet these 

challenges. The preceding discussion has identificd significant advances in the state-of-the-art of acrospacc 

engineering practice that are envisioned in the areas of engineering design and analytical tools, cost and 

risk tools. collaborative engineering, and high-fidelity simulations early in the development cycle for 

NASA aerospace systems. Furthermore, the implications of these advances within the specific context of 

acrospacc manufacturing were discussed - namely, the routine usage of advanced manufacturing modeling 

and simulation methods, enabling manufacturing considerations to influence the system design much 

earlier in the development cycle than is common today. 

REFERENCES 

Dickey. B. “Midcourse Correction.” Government Executive, September 2000. 

Gerard. L. L. “Analysis of the Ariane V Flight 501 Failure - A System Engineering Perspective.” 

Proceedings of thc IEEE Conference and Workshop on Engineering of Comtwter-Based Systems, 

March 14-27. 1997. Monterey, California, pp. 339-46. 

Gleick. J. M. “A Bug and a Crash.’‘ The New York Times Magazine, I December 1996 

Goldin, D. S., S. L. Venneri, and A. K. Noor. “Beyond Incremental Change”. ComDuter, Vol. 3 I, No. 10, 

Oct. 1998, pp. 3 1-39, 

Goldin, D.S.. S. L. Venneri, A. K. Noor. “A New Frontier in Engineering”. Mechanical Engineering 

Lyles, G. M. “Spaceliner 100 - Developing the Technologies to Enable 3rd Generation Launch Vehicles,” 

Proceedings of the 1999 Space Transportation Day Conference, October 27, 1999, Huntsville, 

Alabama. 

Magazine, Vol. 120, No. 2. Feb. 1998, pp. 62-69. 

McDonald. H. (Chair) “Space Shuttle Independent Assessment Team - Report to Associate Administrator 

Office of Spacc Flight.’‘ March 7, 2000. 

NGM (Next-Generation Manufacturing Project). 1997. Next-Generation Manufacturing Report, Volume 1, 

p. 48. Bethlehem, Pennsylvania: Agility Forum 

Noor. A.K., S. L. Venneri,, J. M. Housner, and J. C. Peterson. “A Virtual Environment for Intelligent 

Design”. AerosDace America, Vol. 35, No. 4, April 1997, pp. 28-35. 

NRC (National Research Council). 1999. Advanced Engineering Environments: Achieving the Vision. 

Washington, D.C. National Academy Press. 
Spear. T. (FBC Task Master). “NASA Faster, Better. Cheaper Task Final Rcport,” March 2000. 

Stephenson. A. G. (Chair). ”Report on Project Managcment in NASA by thc Mars Climate Orbiter Mishap 

Investigation Board,” March 13, 2000. 

Young, T. (Chair). “The Mars Program Indcpcndent Assessment Team Report.” March 14, 2000. 
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Sewoil A3 National Ccrito fo/ Advmcrd Mnriolac fimq Workshop 

p,Lj 2- J 01 " 

Composite Manufacturing for Space Launch Vehicles 

DONNA Y. KNEZEVlCH 

Lockheed Martin Space Systems/D-4800 

P.O. Box 29304 

New Orleans, LA 701 89 USA 

Phone: 504-257-2445 

E-mail:ldonna.v.knezevich@,maf.nasa.gov I 

Composite materials offer a large potential for performance increase and weight reduction 

over metallic components for advanced launch vehicles. Building composite hardware for large 

high-efficiency launch vehicles is one of the most demanding engineering challenges from the 

aspects of materials science, structure, and manufacturing. Modern launch vehicles require robust, 

durable, and reliable components capable of operating in cryogenic, high-pressure, and high-temperature environments, while in contact with highly volatile oxidizers and hels. 

technologies for this effort by building, testing, and flight qualifying composite hardware for launch 

vehicle applications for numerous projects, such as the Space Shuttle, X-33, X-34, and the A2 100 

Satellite. Composite hardware built and tested by Lockheed Martin Space Systems Company includes high-temperature vehicle fairings and nosecones, launch vehicle intertank skirts, high-pressure cryogenic helium tanks, cryogenic liquid hydrogen and liquid oxygen tanks, feedlines. and tank 

coverplates. Composite manufacturing for space launch vehicles will soon be enhanced by activation 

of the National Center for Advanced Manufacturing (NCAM). Located at Michoud, NCAM will 

partner government, industry, and academia and bring on line fiber placement and autoclave capabilities that are required for production of large composite structures. 

Lockheed Martin Space Systems Company, Michoud Operations, has developed critical 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:/lampef.msfc.nasa.gov 
Laser Cladding / Glazing as a Surface Coating Alternative 

Authors 

Mr. Rob Hull, Anteon Corporation, 5100 Springfield Pike, Dayton, 

Phone (937) 252-3132 ~3009; Fax (937) 152-0418: e-mail: 

Dr. Dave Firsich. Inorganic Specialists. 710 Mound Ave, COS-327. Miamisburg. OH 45343 

Phone (937) 865-4491: Fax (937) 865-3680; e-mail:lfirsich@coax.net 

Dr. Chuck Woods, Global Manufacturing Solutions, 720 Mound Ave. B-3, Miamisburg. OH 45343; Phone (937) 

I 

1 

865-5039: Fax (937) 865-4749: e-mail:lcwoods@globalms.com 

Phone (937) 3552334x3 165; Fax (937) 255-1 128: e-mai&ohn.wcfi ml..1frl.af.ini1 

1 

Mr. John Eric, AFRUMLPJ, 3005 P Street Suite 1 ,Wright-Patterson AFB. OH, 45433 

I 

Abstract 

Increasing environmental regulations and rising waste disposal costs are driving the need for economic 

chrome plating replacement technologies. This paper summarizes one of several chrome replacement research & 

development programs funded by the Air Force Pollution Prevention office. This work focuses on two laser-based 

coating processes - laser cladding and laser glazing - for the application of a thick (5-25 mils) uniform coating with 

similar if not superior mechanical performance to that of hard (wet) chrome plating. All experiments were 

performed using a flattop continuous wave carbon dioxide laser, operating at 10.6 microns. 

This paper describes the laser cladding and glazing techniques, the processing parameters developed and 

the mechanical performance of the resultant coatings. Emphasis will be placed on the laser glazing technique 

developed under this effort. The technique uses the laser’s rapid surface heating effect to melt, re-flow and 

consolidate protective coatings deposited using any type of thermal spray technique - in this case, a flame-spray 

coating system. Post flame-spray treatment using laser glazing transformed an economical but porous coating into a 

uniform. pore-free coating with superior performance characteristics to that of chrome. Materials characterization 

and mechanical property test results are discussed. 

Introduction 

For many years, chromium plating has been an inexpensive standard Air Force (AF) processing technique 

for providing corrosion protection, friction reduction, wear resistance, and the ability to build-up worn surfaces. 

Chrome plating or electroplated chrome is an electrochemical process for depositing a bonded layer of chromium 

metal on aerospace parts of various base materials. The process, which involves large vats of chromium metal to 

deposit the coating and chemical stripping or traditional machining facilities for the removal of the chrome coating 

prior to rebuild and repair, produces a large stream of toxic waste. Changing emission regulations and 

Environmental Protection Agency (EPA) chemical reduction policies (EPA- 17), along with rising disposal costs, 

made it necessary for the AF to develop alternative treatment methods to chrome plating. Estimates of the disposal 

costs associated with this process topped $16M/year in FY95. Preliminary studies indicate that laser deposition of 

metals or other laser-assisted surface treatments might offer acceptable replacement techniques. 

Conventional chrome plating is used to apply a wide range of thicknesses, corresponding to different 

applications. Thin chrome coatings (1-10 mils) can be used for corrosion protection, while thick chrome coatings 

(10-40 mils) are often used to build up surfaces, which have worn down through extended use. The primary 

challenge in developing a substitute process for chrome plating was to provide most, if not all, of the desirable 

properties of chrome - hardness, adhesion, corrosion protection, lubricity, surface finish. and the ability to build-up 
worn surfaces - with one alternative process. Providing one or two of these characteristics is relatively easy; to 

simultaneously provide all of these characteristics is a formidable task. The AF and other chrome platers are finding 

that one replacement technique for all chrome plating applications may nor be practical but that a \.ariety of 

application-specific solutions may be required. 

The Air Force Research Laboratory Materials & Manufacturing Directorate (AFRUML), as part of their 

Pollution Prevention Special Emphasis Area. funded Anteon Corporation to investigate laser-based surface 

treatment techniques as possible replacement technologies for electroplated chrome. This project would expand 

upon laser processing activities Anteon was already performing as part of their operation and support contract for 

the Laser Hardened Materials Evaluation Laboratory (LHMEL). a state-of-the-art materials effects test facility 

housing a number of high energy lasers. 

The results of laser processing work at LHMEL - both with laser cladding and with laser glazing of 

thermally sprayed coatings - have shown that laser processing is a viable and feasible process for producing well 

consolidated, corrosion and wear resistant coatings. The common feature of the two is that they each melt the 

coating layer, reducing its porosity and sealing the surface against air or water permeation, a critical requirement for 

preventing corrosion of the underlying metal. Results also showed that these laser-processed coatings could satisfy 

the majority of the performance requirements currently fulfilled by electro-deposited chrome plating. especially 

where large thickness build-up is necessary. 

The laser used for these experiments was the LHMEL I device, a 15-kW continuous wave flattop carbon 

dioxide laser. This is a very well characterized and repeatable research 81 development laser used by the Air Force 

for a variety of materials interaction experiments. The high energy output provided by this device allowed these 

laser processing experiments to be performed using larger beam sizes than are typically demonstrated. Larger beam 

sizes will equate to faster processing speeds in actual applications. Laser glazing samples were rotated on a small 

lathe during laser processing while the part was translated laterally through the beam using a CNC table. Clad 

samples were prepared using the same CNC controlled table. 

The authors wish to recognize their government sponsors, Mr. Jay Tiley and Ms. Mary Ann Phillips from 

AFRLML at Wright-Patterson AFB, OH. 

Laser Glazing of Flame-Sprayed Coatings 

Flame spraying is an inexpensive method of applying wear or corrosion resistant coatings. The process uses 

a modified acetylene-fueled torch to heat a powdered metal, which is then deposited on the substrate surface via a 

gas-assisted delivery system. The process, however, produces a relatively low velocity spray resulting in a slightly 

porous coating with limited adhesion to the substrate. The quality of a flame-sprayed coating may, however, be 

improved using a process called laser glazing. Laser glazing utilizes the laser’s rapid surface heating effects to melt, 

re-flow and consolidate the flame-sprayed coatings thus reducing its porosity and improving the bonding. The 

remaining porosity seen in flame-sprayedlaser glazed coatings is comparable to that seen in conventional chrome 

electroplate. The remaining porosity also appears to be closed-cell, suggesting that the glazed coating is not 

permeable, and in fact, a glazed part has passed 196 hours of salt-spray testing. 

Laser glazing experiments were conducted using approximately 7.5-kW of power on target, deposited in a 

1.3-cm diameter beam. The samples used were cylindrical rods approximately 12” long and 1” in diameter. The 

rods were mounted on a small lathe bed and were rotated during the glazing process. The rotating rod was then 

translated through the laser beam on a CNC controlled table. Typical translation speeds of X feet per minute were 

used for these experiments. 
' , *ii 

.. - -. 

< . .> 

Figure 1: Cross-section of a flame-sprayed coating, before and after laser glazing. (2OOX) 

Two types of coating materials were investigated under this study. The first coating was Versalloy 50; a 

nickel-based coating selected for corrosion resistance applications. The second coating was a mixture of Versalloy 

50 with tungsten-carbide cobalt (WC-Co). selected for wear resistance applications. These two coating materials 

were flame sprayed on a variety of substrate materials including AIS1 1030 steel. D2 tool steel and AIS1 4340 alloy 

steel. While good results were obtained with both powders, the WC-CoNersalloy mixture proved the most 

interesting. 

SEM analyses of the WC-CoNersalloy coating showed that an interdiffusion had take place between the 

WC particles and the surrounding Versalloy matrix or nickel (Ni) matrix, resulting in a microstructure consisting of 

WC particles surrounded by a transition layer. encased in the Ni rich matrix material. This interdiffusion creates a 

continuous transition layer from the hard WC particles to the ductile Ni rich matrix. The transition layer not only 

facilitates an excellent bond between the particles and substrate. but also provides a region of transition in physical 

properties. such as thermal expansion etc. The figures below show the results of analyses of these coatings applied 

to a D-2 tool steel substrate. 

Figure 2: SEM Micrograph showing phases in WCICoNersalloy 50 coating. Note homogeneous coating. 

Figure 3 depicts a higher magnification of the laser glazed WC-CoNersalloy coating and shows that Wrich particles. which were once WC, have now been alloyed with the matrix material yet still retain the hard 

complex carbides. 
Figure 3: Higher magnification image of "altered" WC particles in Versalloy 50 

Figure 4 hrther magnifies the WC particle that is undergoing dissolution and alloying. The carbon 

becomes more diffuse and there is an exchange of elements with the surrounding matrix materials. This results in a 

complex distribution of complex carbides that are nicely compatible with the surrounding matrix and results in a 

tough coating. 

Figure 4: High magnification SEM micrograph of WC particle surrounded by Versalloy matrix. Note 

transition zone from particle to matrix. 

After laser glazing, the WCICoNersalloy coating was welded to the substrate. No discrete interface layer 

appeared to exist between the coating and the substrate material. The welding occurs over about a 4 mil thick layer 

in the substrate. This is shown in the two figures below. 
Figure 5: SEM Micrograph of interface region between the WC-CoNersalloy coating and the D3 

substrate. 

: I 

Figure 6: WC particle found 3-mils into the D2 steel substrate. 

Excellent laser glazing results were obtained with both the VersalloySO and WC-CoNersalloy mixture. It 

was much more difficult to laser glaze the Versalloy 50 alone, however. This is most likely due to the difference in 

specular reflectivity of the powders. The WC-CoNersalloy is less reflective than the Versalloy alone. The powder 

mixture allows for a wider range of laser power to achieve melting, whereas the Versalloy alone had to be taken 

right up to the limit of melting, where it becomes more absorbent and sometimes over-absorbed and burned through. 

It should be noted that thermal spray parameters do indeed play a major role on the ability to successfully 

glaze a part, and effect the integrity of the glazed coating produced. It is not just adequate to have the powder 
adhere to the surface. The density of the powder sprayed and the integrity of the bond between the substrate and the 

sprayed powder profoundly effects the glazing process. Results of this study seem to indicate that the bond integrity 

of the flame-sprayed coating effects the thermal conductivity of the powder/substrate combination. which in turn 

influenced the laser processing parameters needed to produce a sound glazed coating. 

Analysis of the substrate after the laser glazing process was applied revealed that, in some cases, fresh 

martensite was formed in the heat-affected zone below the coating layer. This was particularly true for the WCCoNersalloy coatings on heat treatable substrates such as D-2 and 4340. A low temperature tempering will 

probably be needed after the laser glazing process to convert the fresh martensite and stabilize the mechanical 

properties of the substrate. 

Another brief set of experiments were performed to demonstrate that damaged or worn laser glazed 

coatings could be repaired and returned to service without the need for costly coating removal and disposal. To 

demonstrate this fact, selected rods damaged in testing were flame-sprayed again and then re-glazed. The coatings 

produced were as uniform as the original coating with little or no noticeable transition between the original and 

repaired areas. This repairability factor could make laser glazing a much more appealing replacement for chrome 

than other candidate processes that cannot support this ability. 

Laser Cladding 

The second laser processing technique investigated was laser cladding. This process uses laser energy to 

simultaneously heat the substrate surface and melt a coating material - in powder or wire form - to produce a 

uniform surface coating at a variety of thicknesses. 

For the LHMEL cladding experiments, a powder feed system was used to deliver the powder and laser 

energy simultaneously onto a flat sample. The powder was injected along the sample's axis of translation at a 15- 

degree angle to the surface. The samples were translated over a four pass track with overlaps of 2S% to 45% 

between passes. The nozzle orientation provided the best powder deposition pattern but variations were seen 

depending on whether the nozzle was in a leading or trailing relative to the laser beam. Leading deposition seemed 

to produce the more uniform coating. 

The large spot sizes achievable with the LHMEL I device were again utilized for these laser cladding 

experiments. Laser power on target was held constant at 5-kW with a beam size of 0.5" diameter. Samples were 

flat pieces of steel, 7" wide x 6" long x %" thick. Typical translation speeds of 0.25" per second were used for these 

experiments. The samples were placed on a CNC table and were translated in both the x- and y-directions during 

the cladding process. 

All laser cladding experiments were conducted on AIS1 1018 carbon steel substrates. Powders selected for 

laser cladding experiments were the same as were used for the laser glazing study - the Versalloy SO nickel-based 

powder and the WC-CoNersalloy mixture. The nickel-based powder was much easier to clad and produced 

smooth, uniform beads of coating on each pass with good overlapping. The tungsten carbide mixture produced a 

rougher. less uniform coating that was clearly going to require extensive machining to produce an acceptable 

coating. Since funds were limited on this study and the challenge of machining the WC-CoNersalloy mixture 
seemed excessive, further cladding work concentrated on the Versalloy 50 coating alone. 

Results of the tests were very promising. The laser cladding process produced a smooth uniform coating 

with thicknesses in the range of 10-25 mils. A representative clad sample was sectioned and examined: it appeared 

to have a dense and well-bonded coating as shown in Figure 7. Another item of note regarding the coatings shown 

in this figure is that the coating was produced by two separate 4-pass treatments. The two groups of passes were 

overlapping and offset by approximately 1/8". As can be seen in the micrographs and despite being formed in two 

separate passes, the coating appears as a single uniform layer. This fact validates the assumption that worn or 

damaged laser clad surfaces can be easily repaired with no impact on the coating performance. 

Figure 7: Micrographs of laser clad Versalloy 50 on 1018 steel 

Corrosion tests also confirmed that this coating provided a pore-free protective layer that easily survived 

196 hours of salt spray exposure. While additional work is required to demonstrate this process on cylindrical or 

other more complex shapes. the results offer great promise for a very versatile yet durable coating process. 

Mechanical Testing 

Mechanical property tests revealed that both the laser glazed and laser clad coatings produced durable, nonporous coatings. The laser glazed and laser clad Versalloy 50 coatings, originally selected as corrosion resistance 

coatings, perfornied well in the salt spray booth, easily surviving the standard 196 hour durability test. 

Unexpectedly, the laser glazed WC-Co / Versalloy SO mix coating also survived remarkably in the salt spray tests. 

After surviving the initial 196-hour test, samples were left in the salt spray for an extended period until any sign of 

visible corrosion or pitting occurred on the sample surface. The samples survived a remarkable 2700 hours in salt 

spray before showing one or two small pits. 

The laser clad and glazed samples were also subjected to wear tests to assess their durability and wear 

resistance. Flat circular samples were placed in a pin-on-disk wear fixture and tested at 300 RPM with a 2OO-gram 

load for 25,000 cycles. A similar chrome plated sample was also placed in the test to serve as a comparison to 

current Performance. As was expected. the Versalloy 50 corrosion resistant coating wore slightly faster than the 

chrome plated sample. The WC-CoNersalloy wear resistant sample's performance was roughly equivalent to that 

of the chrome coating. 
Summary 

It has been demonstrated that flame sprayed coatings can be successfully applied to a substrate then laser 

glazed to produce excellent high density, corrosion resistant. wear resistant coatings. Successful laser glazing was 

performed on rods coated with Versalloy-50 and on rods coated with a mixture of Versalloyflungsten Carbide 

Cobalt. The reproducibility of the process was far greater for the mixture, which melted at a much higher 

temperature and introduced more heat into the substrate. It has also been shown that the laser glazing process has 

very little effect on the underlying substrate microstructure and that the integrity of the flame sprayed coating plays 

an important role in determining the integrity of the resultant laser glazed coating. Microstructures produced by laser 

glazing of the WC-CoNersalloy coating resulted in partial dissolution of the carbides into the nickel rich matrix. 

This creates a very strong and hermetically sealed coating that should withstand corrosion and thermal cycling 

environments very well. 

Laser cladding has also been demonstrated as a viable chrome-plating alternative. This method can 

produce pore-free, well-bonded coatings of varying thicknesses on a variety of substrates. Under this study. 

cladding experiments gave better results with Versalloy-50 powder alone than with the WC-Co/Versalloy powder 

mixture. Corrosion and wear tests on the clad samples showed comparable performance to that of chrome. 

This effort also demonstrated tho successful repair of worn or damaged parts using either laser glazing or 

laser cladding. The ability to apply a second layer of coating without creating any apparent interface between it and 

the original suggests that cladding and/or glazing can be used to build-up or repair worn parts without the added 

costs of prior coating removal and the subsequent disposal of the waste stream. 
Testing of Environmentally Preferable Aluminum 

Pretreatments and Coating Systems for Use on 

Space Shuttle Solid Rocket Boosters (SRB) 

By 

Catherine Clayton 

United Space Alliance 

8550 Astronaut Blvd., M/C USK-821 

Cape Canaveral, FI 32920-4304 

(claytonc@usasrb.ksc.nasa.gov 1 (321) 853-0523 

Randy Raley 

United Space Alliance 

8550 Astronaut Blvd., M/C USK-821 

Cape Canaveral, FI 32920-4304 

(321) 853-0521 I raleyr@usasrb.ksc.nasa.gov I 

Lee Zook 

United Space Alliance 

8550 Astronaut Blvd., M/C USK-C52 

Cape Canaveral, Fl32920-4304 

I zookim@usano.ksc.nasa.gov I (321) 861-5611 

Abstract 

The SRB has historically used a chromate conversion coating prior to protective finish application. After 

conversion coating, an organic paint system consisting of a chromated epoxy primer and polyurethane topcoat is 

applied. An overall systems approach was selected to reduce waste generation from the coatings application and 

removal processes. While the most obvious waste reduction opportunity involved elimination of the chromate 

conversion coating, several other coating system configurations were explored in an attempt to reduce the total 

waste. This paper will briefly discuss the use of a systems \4ew to reduce waste generation from the coating process 

and present the results of the qualification testing of nonchromated aluminum pretreatments and alternate coating 

systems configurations. 

Introduction 

United Space Alliance - Solid Rocket Boosters (USA-SRB) refurbishes the non-motor components of the 

SRB. The structural components are primarily constructed of aluminum alloy (AA) 2219 or Alclad 7075. The 

aluminum is chromate conversion coated with MIL-C-81706 (Alodine 1 200S/l201), primed with Deft primer 44- 

GN-7 and then topcoated with Deft topcoat 03-W- 127A. 

MIL-C-8 1706 specifies chromate-based solutions used in the formation of a conversion coating to provide 

a protective layer on an aluminum surface. This conversion coating is used by industry for its corrosion protection 

properties and to promote adhesion of paints to the aluminum. However, the high copper content in AA 2219 

negates the corrosion protection properties of the chromate conversion coating. Since much of the aluminum 

components of the SRBs are 22 19, the pretreatment is only used to promote and stabilize paint adhesion. The waste 

stream for this process is one of the largest at Kennedy Space Center (KSC). Anywhere from 20 to 50°/0 of 

chromate conversion coatings are chromic acid. Hexavalent chromium, which is present in these solutions, has been 

determined to have serious acute and chronic exposure hazards. The Occupational Safety and Health Administration 

(OSHA) continues to move toward stricter regulations for the use of chromium in the work place. The 

Environmental Protection Agency is also continuing to tighten regulations related to airborne and liquid releases of 

these materials. 
The Deft paint systeni is used to coat the aluminum and Comosion Resistant Steel (CKES) alloys. Deft was 

chosen iis the paint system on these metel sui-f;iccs for its lower volatile organic compound (VOC:) content and 

contpatibility with the thermal protection system (TPS) materials. The Dcft paint system has se\wal processing 

limitations which include a short pot life fot both primer and topcoat. prinier curing issues and topcoat catalyst 

moisture sensitivity. These processing problems result in process efficiency limitations that currently have no 

options to avoid or mitigate thein. The primer also uses a hexavalent chromium corrosion inhibitor, which is under 

the same regulatory pressure as the pretreatment. Finally, these coatings which cover and protect 95% of the SIiB 

hardware are sole sourced with no alternates. .4 tire or other disaster at the manufacturer’s plant could pIace space 

shuttle schedules in jeopardy. For these reasons the Alternate SKI3 Aluminum Coating Project was undertaken to 

identify and qualitL alternatives for the current coating and pretreatment system. 

Experimental Design 

The Alternate SRB Aluminum Coating Project consisted of tluee phases: down selection, qualification. and 

implementation. After review of vendor information, such as data sheets. and MSDSs six pretreatments and six 

coating systems were tested in the down selection portion of the project. Time pretreatments and tllree coating 

system were chosen from the down selection testing for qualification. Consult “Alternative SRR .4luminuni 

Coating Systein Down Select Test Report” (8) for a disciission of how the candidates were chosen. The candidate 

niaterials chosen for qualification testing are listed in Table 1*. In addition to testing new materials for a straight 

drop in replacements, this qualification program has also considered a new flight configuration, which consists of 

prinier as the only coating. The goal was to certify the prette~rmient’prinit.r configuration without topcoat in ue3s 

that are stripped every flight. All coating candidates (primer and topcoats) were evaluated on each candidate 

pretreatment and the baseline pretreatment (Alodine 1201). .4dditionally, the baseline coatings (Deft 44GN7 primer 

and 03W0127 topcoat) \wre evaluated on all pretreatments. Testing included the currently used SRB coating 

configiration as a baseline to assist in the performance assessment of the candidate materials. The full factorial 

experiment design panel matrix used for each test required 104 separate conditions to be produced which, with 

duplication. would mean 208 test surfnces. The alloys tested included aluminum alloys 22 19, 606 I. and 7075; also 

304 stainless steel. Where appropriate, the number of material variables was reduced to simplify testing and data 

analysis. 

Table 1. Candidates Selected for Qualification Testing 

Pretreatments 

Alodine 120 I 

Alodine 5700 

Chemidize 72 7A 

Okenicoat 4500 

Primers 

Deft 44CiN7 

PRC-DeSoto 

152A:B 

Hentzen Corp. 

055 IOWEP-XI’ 

OS5 1 I CEH-X 

Lord Corp. 9929A/B 

‘Topcoats 

Deft 03W I27A 

PRC-DeSoto 

EUAW098AI 

EUAC082B 

Hentzen Corp. 

4636WUX-3I 

4600CHA-SG 

Lord Corp. A276 

When a coating was found to be unsatisfactory for qualification at any point, testing of that pretreamient 

andior coating system was halted. One pretreatment and one coating were dropped durutg the qualification testing. 

Okemcoat 4500 pretreatment and the PRC-DeSoto coating system. 

Testing was conducted in accordance with “Alternative SKB Aluminum Coating Systcin Qualification Test 

Plan,” CPC-054-98MP (8) which gathered corosion protection, bond strength, compatibility with other SRB 

materials, batch-to-batch consistency. and theinial environments data. A coniplete copy of the test data along with 

pertinent digital photographs has been placed on computer disk and is available upon request. 
Methods 

Testing conducted to quality the candidate pretreatments md coating system consisted of analysis in these 

areas: Corrosion, bond strength, compatibility with other SKB materials, batch-to-batch consistency. and thermal 

environments. 

Thc corrosion protection of‘fered by a coating system relies upon the adhesion of the coating to the metal 

surface. corrosion inhibition properties of the pigments within the coating and the resistance of the coating to 

moisture absorptioiv’pemieation. It is veiy difficult to torinulate a single product to encoinpass all of these 

considerations. To maximize the corrosion protection, several classes of products are used. These include adhesion 

promoters (prctrcatments). primers (incorporating corrosion inhibiting pigments) and topcoats (to minimize moisture 

permeation). The level of corrosion protection required for a particular componentkystem should be based upon the 

me cnvironnmclnt and service (refurbishment cycle) requirements. 

Corrosion testing of the candidate pretreatments and coating system was conducted to detLmnine the 

efectiveness of the corrosion preventative properties of the candidate materials. The evaluations included beach 

exposure, seawater immersion, and Electrochemical Impedance Spectroscopy (EIS). These test rcgiines were 

selected to provide an aggressive real life performance evaluation of the candidates conihined with a practical 

laboratory evaluation technique. While the SRB iises several aluminum alloys. AA 2219 was sclected for all 

corrosion testing due tri its inherent poor corrosion resistance. 

Seawater inimcrsion testing was conducted to reflect the actual use environment of the SRB hardware. 

After launch, the SKB lands in the ocean and is towed back to port. The SRB normally spends 23 to 48 hours in 

seawater but Itas been immersed more than twice that long when problenis were encountered in recovery. The 

coupons used in the seawater immersion test were then used for the beach esposure test. The coupoiis were placed 

;it the Kennedy Space Center (KSC‘) Atmospheric CoiTosion Test site within 48 hours of removal from the seawater. 

These coupons went through both tests scribed. The exposure times were six and twelve months. 

The final corrosion test conducted was Electrical Impedance Spectroscopy (EIS). With EIS. a small 

amplitude AC voltage is applied to the test coupon and the coating response is measured. This process is rqeated 

over a range of frequencies to generate a broad response spectrum. EIS technique is considered to be nondestructive 

to the coating. this allows the change in coating performance to be ineasured over time. Each clccti-olytic cell over 

the test coupon contained 200 ml of liltered seawater. Measurements were taken at 4, 168, and 672 hours. 

The most critical physical property for SKB coatings is the ability to act ;IS an adhesive base for the thermal 

protection system materials. Bond strength testing was conducted to ensure that the coating systems adhere to the 

pertinent SKB substrates and to themselves. Next the testing \viis expanded to look at the effects of different 

cnvironinents, themial cycling. water immersion, and damage resistance or flexibility. Adhesion testing was 

conducted per ASTM D 4541 -95 “Pull-C)ff Strength oL‘ Coatings Using Portable Adhesion Testers” (6). Adhesion of 

the coatings in high temperature cnviroiinients was tested per ASTM D 1623-78 “Tensile and Tensile Adhesion 

Properties of Rigid Cellular Plestics” (7). A failure during a water immersion test could be an indication of a 

deficiency in the coating itself or inadequate surface preparation provided by the candidate pretreatment. Coatings 

used on the SRB need to be able to adhere under these conditions. Water resistance is not a corrosion test and there 

is no correlation with immersion into the Atlantic Ocean. Testing was conducted per ASTM D 870-97 “Testing 

Water Resistance of Coatings Using Water Imniersion” (3 j. Flexibility testing was conducted to deterniine the 

resistances of the candidate coatings to cracking on metal substrates as those substrates are defoinied. This is a 

nieaswe of dainagc. resistance. The testing wils conducted per ASTM D 522-93a “Mandrel Bend Test of Attached 

Organic Coatings” (5). 

Any coating system used on SKI3 surfaces must be compatible with the chemicals and materials that will 

come in contact with the coating system. This includes thermal protection system, sealants. cleaners and possible 

incidental contact with various chemical compounds. Materials applied to the coating system must be able to adhere 

to the coating system at flight temperatures as well as at room temperature. The testing for iiiaterial adherence and 

chemical comp;itibility was conducted per ASTM D 1623 “Tensile and Tensile Adhesion Properties of Rigid 

Cellular Plastics” (7). ASTM D 3541-95 “Pull-Off Strength of Coatings Using Portable Adhesion Testers” (6). and 

ASTM I 502-93 “eflkct of Cleaning and Chemical Maintenance Materials on Painted Aircraft Surfaces” (4). 
The candidate coatings and pretreatments must be able to withstand the thennal cnvironmeiits of space 

flight. The candidate coatings were sub-jected, hare and with the thermal protection system in placc. to convective 

testing perfoniied in the National Aeronautic Space Administration / hfarshall Space Flight Center (NASA:MSFC) 

Improved Hot Gas Facility (IHGF). The IHGF is a nominal MACH 4.1 aerothertnal tunnel that burns a lean nlixture 

of hydrogen (GHJ and air to produce temperatures up to 2200°F ;it total pressures up to 200 psia (pounds per square 

inch atmospheric). The coatings and pretreatments used on SRB flight hardware must not be able to support 

combustion. Testing for flammability of the pretreatments and coatings was conducted per. 4.1 of NHB 8060.1 t3 

“Flaminability, Odor, and Off-gassing Requirements and Test Procedures for Materials in Environinents that 

Support Combustion” (2). 

To ensure that the xendors of the candidate coatings and pretreatments could supply a consistent product 

from lot to lot. repeatability testing was conducted. This tcsting consisted of EIS testing, adhesion testing. and 

compatibility testing to Spirit 126 (cleaner used on coated surfaces). 

Results 

The amount of data produced from the tests discussed above was substantial. Aluniiiiuin alloy 2219 was 

selected for all corrosion testing. The exposure tests conducted were more severe than tests used in past coating 

qualifications. The sen water immersion results showed that the Chemidize 727!Hcntzen primer coating 

configuration was significantly worse at thc end of the exposure period than the bascline coatingipirtreatment 

system. AI1 other coatings were considered nominal. The coupons used for the sea water iininersion were then used 

for the beach exposurc testing. After exposure, no coupons werc found to have either filiform corrosion or any 

biological growth. The Alodirie 5700 pretreatment with Lord primer and the Alodine 5700 with the Lord prinier and 

topcoat had the least amount of coiTosion other than the baseline configuration. The PRC-DeSoto prinier was the 

poorest perfomiing primer regardless of the prctreafnient configuration. At the time of the corrosion testing the 

PRC-DeSoto announced that they would no longer produce the topcoat that was in the test prograni. Testing 

continued with the primer for further ~i~l~ittion of the product. The results of tlie corrosion data showed that the 

PRC-DeSoto prinier was not an acceptable coating for SRB use 

The EIS testing showed no sigiiificant difference betwccn the pretrcatments of the primed and topcoated 

coupons. However. the performance of the primer-only coupons did show some differences for the Deft and 

Hentzen coatings. Both of these priniers over Chemidize 727 pretreatnient sliowed a dccrcase in performance, see 

Figure I*. 

The bond strength testing includes data of the pretreatments and coatings on 2219 TX7 aluminum, 7075 

Alclad aluniiiiuin, and 304 stainless steel. The coatings were tested on the 304 stainless steel without pretreatment. 

The coatings adhered to the stainless steel better than to the aluminum alloys. There was no significant difference in 

the coating inaterial adhesioii attributable to the pretreatment material. After tlie alloy and prctiratnicnt factor is 

removed from the results, the Deft topcoat performance appeared to be better thm the candidates by about 12 06. 

Still the adhesion values of the candidates are close to double the niiniinum requirement of 700 ponds per square 

inch (psi). The averages range from 1266 psi for Lord ptimer over Chenlidize 727 on 7075 Alelad to 2469 psi for 

RA topcoat 011 304 stainless steel. 

For repair purposes. testing was coiiducted to deteiniiiie the streiigth of the candidates over each other. 

This included all variations of prinien and topcoats. Thc values of the adhesion results were within expected 

population of the noniinal values obtained froiii the preyious adhesion tests with a majority of the vnlues above I400 

psi. The range was 1259 psi to 2647 psi. Some high performance coatings develop vcry inert surface layers due to 

side reactions or level of cure and cross-linking. For this reason adhesion testing was conducted on double-coated 

coupons. The first coat was fully cured prior to application of the second coat. The results of the tests were nominal 

as compared with the previous adhesion test results with the average of the values being IS00 psi. 
184 I 

te-a 

Figure 1. Magnitude for Chemidize 727 With Primer Candidates 

...... ........... ..................... 

To ensure the coatings could withstand multiple flights before having to be removed, Cyclic high 

temperahire testing was conducted, The coupons \vere cycled to 350°F from room temperature ten times with 

adhesion tcsting being conducted after five and ten cycles. The Hentzen and Lord primers did not show any 

significant change in strength throughout the cycling. Ths shows a stability that was expected for these materials. 

The baseline Deft primer showed a decrease in strength throughout the cycling. One possible explanation is that the 

DeA primer remains more reactive after it has dried. This would cause it to oxidize readily when exposed to a more 

reactive (hotter) cnvironnient. The pretreatments had no influence on the results of this test. 

Flatwise-tensile testing was conducted to deterinine how well the pretreatments and coating systenis adhere 

at 35Wl:, the worst case SiUj temperahire environment. One pattern emerged hm the testing. The Lord coatings 

had a marked tendency to fail at the or near the pretreatment at the elevated teinptrature. This was even morc 

pronounced when Lord coatings were over Chemidize 727 pretreatment. The lowest value ofthe Lord coating with 

tlc primcr.'pretreamicnt failure was I81 psi. The average of'all the tests was 259 psi. This shows a drop in strength, 

however there is no minimum strength requirement for ;I paint to adhere at 350°F. Our criteria is that the coatings 

exceed TPS strength in the same cnviroimient. Therefore, all the paints are considered acceptable for program use. 

Water immersion testing was conducted on scribed pnds of the candidate coating systeins per ASTM 

D870-97 "Testing Water Resistance of Coatings Using Water Immersion" (3). A failure during this test could be :in 

indication of a deficiency in the coating itself or inadequate surface preparation. The principal criteria were to have 

no lifting of the coating and no active corrosion under the coating. Every panel, regardless of' alloy, which was 

pretreated with Okeincoat 4500 and then coated with PRC-DeSoto failed due to blistering and flaking of the coating, 

both at the scribe and in the general acreage. With other pretreatments the PRC-DeSoto coatings would develop 

sinall blisters on about 46Oh of the panels which "healed" when the panels dried. Panels pretreated with Okemcoat 

4500 developed blisters on 65% of the panel area. If the C'hernidize 727 pretreatnient was not completely rinsed 
from the panels, the edges could flrlke. Some level of blistering was obsenwl on all panels coated with Hentzen 

over Cheniidize 727. The AIodine 1201 and Aldiiie 5700 had minor blistering observed at the edges. This 

underscored the importance of thorough rinsing and draining during the application process 

The flexibility test was used to (leternline the resistances of the candidate coatings to cracking on metal 

substrates 3s those substrates are deformed. The results of this test showed one pretreatment. Okemcoat 4500. had 

significantly poorer propcrties. The Okenicoat 4500 did not cause the paint to crack. the pretreatiiient failed in shear 

loading along the bend leading to delamination of the coating with cracking and peeling. There are no SRB program 

acceptance or rejection criteria for elongation, but the failure in shear is felt to be not acceptable due to 

environments that the coating would see. For this reason and the results of the water immersion. Okemcoat 4500 

was droppcd from the qualification program. The other pretreatiiients did not influence the result.. . The coatings 

were all comparable with the exception of the Hentzen topcoat. It was significantly more rigid than the other 

coatings but still acceptable. Fiye 2" shows exaniples of coupons that passed versus a failure of the Mandrel Bend 

Test. 

Figure 2. Mandrel Bend Coating Failure 

Acceptable >32% elongation 

Acceptable -20% elongation 

Failure - Coating Delamination 

Material compatibility testing was conducted to eiisure that the inaterials applied over to the SRB coated 

surface would adhere to the candidate coating systems. The following materials were tested with the candidates: 

MCC- I PR- I422 CORK PIS 870 BTA RT4 5 5 

VC'I 368 LPS Hardcoat DeSoto repair Primer DeSoto Repair topcoat 

Hypalon PK- 1 770 Insta-Foam KTV 133 KSNA EA-934 
Some of the materials have minimum strength requirements. All the tensile strength requirenicnts were 

met. The values were nominal iis compared to the baseline and past tensile studies. The Hentzen topcoat did show a 

marked decrease in bond strength at room teniperature wit11 RTV 133. The drop in bond strength was about 53%. 

There is no miniinuni strength requirtment for RTV 133. All failures were between the RTV 133 and the Hentzen 

topcoat. A change in surface preparation prior to bonding silicone sealants may be needed. The drop in bond 

strength for RTV 133 over Hentzen did not follow through to the high temperature testing. The values for RTV 1-33 

over Hentzen ;it 350°F were nominal as compared to the other candidates and the hiiselhe. The DeSoto repair 

topcoat showed a great affinity to tlic Hentzen and Lord primers. The average strength of the DeSoto repair 

compatibility testing was 1469 psi. whereas the average of the DeSoto topcoat over Hentzen and Lord primers was 

2655 psi. 

In addition to room teinpcrature testing, the thennal protection systeni (TPS) and sealants were also tested 

at elevated temperature to ensure that they could adhere to the candidate coatings during flight. There is no 

mini tnuni tensile strength requirement for elevated tenipcrature adhesion, only that the matetial deinonstratc 

adherence. MCC-I. K5NA. Cork, RT455, HTA. and RTV 133 were tested at 350°F. PR-1422 was tested at 275”F, 

PR- 1770 was tested at 2800F, and Pis 870 was tested at 235°F. The polysulfide sealants werc tested at a lower 

teniperature due to their respective softtming temperatures. As was .seen in earlier flatwjsc tensile testing ;it elevated 

tenipcraturcs the Lord coatings over Chemidize 727 failed between the primer and the pretreatment. Thc PR- 1422 

with I-ord primer also had failures between the primer anti Okeincoat 4500, Alodine 1201, and Alodine .5700. There 

\vas significant variation witlun thc material of the PR-I 770 sealant, influencing the rcsiilts of that particular test 

data. The rest of the test results weir nominal as compared to the baseline configuration. 

Cheniical exposure tests were conducted to determine if contact to cleaning fluids and incidental contact to 

pertinent chemicals would affect the candidate coatings. A drop of 2 pencil grade is considered a failure in this test. 

The candidate coatings were exposed to following compounds at 9YF: 

Spirit 126 Pri IllC PF Degreawr 

I-t(!i Citric Acid 13% Sodium Hydroxide 

The exposure tcinperahire for the following compounds was room temperature due to their ilamniability: 

Isopropyl Alcohol (PA) Acetone DS- i 04 

Hydraulic F1 iiid Tolu cne Methyl Ethyl Ketone (MEK) 

Spirit 126, Prime, PI: Degreaser, hydraulic fluid, 13% sodium hydroxide, and 14% citric acid did not affect 

any of the candidate coatings. Okemcoat 4500 had been withdmwn fkom the test program prior to compatibility 

testing. IP.4 did affect PRC IkSoto topcoat. The other solvents, MEK, DS-104. tolucne, and ac,etoiie arc 

aggressive solvents that would affect or strip a coating. These solvents are used to remove tenacious contaminates. 

A drop in 2 pencil grade is not considered a failure for these solvents. Acetone did have a definite affect 011 PRC 

DeSoto and Deft topcoats. DS-104 affected Deft. PRC DeSoto, and Hentzen topcoats. DS- 104 also had some effect 

on Hentzen primer. A second test was conducted with these solvents to more clearly determine their effect on the 

candidate coatings in a handwipe situation. These solvents are only used on SRB coatings in handwipe processes. 

A h;ind wipe rub test was conducted per MIL-C-85285B “Coating: Polyurethane, High Solids” (1). All candidate 

cleancrs passed thc rub test for all solvents. Okemcoat 4500 and PRC-DeSoto had been withdrawn from the test 

program prior to the rub test. The candidate coatings were also exposed to hydrazine. All of the candidate coaling 

systeins passed the hydrazine conipatibility test. 

To ensure that the candidate coatings systena are able to withstand the thennal environments of space 

flight. thermal testing at hlSFC IHGF was conducted. All the candidates passed thermal testing with TPS applied to 

the surface and without TPS applied to the surface. Paiiels without TPS were tested at 5 BTWf and TPS panels 

were tested at 7 BTU/ft’. Okemcoat 4500 and PKC-DeSoto were dropped during the thermal testing and were not 

included in the results. 
The coatings and pretreatments were tested to ensure that they would not be able to support combustion. 

All pretreatments and coatings passed the tlaminabilitp tests. The bum lengths were less than 6 inches with a burn 

time of less than 10 minutes. There was no sparking, sputtering. or dripping. The panels that had Okeincoat 4500 

pretreatinent had the longest burn leiigth with an average of 0.8 inches. The aieiage of. all the otlier pnnels was 0.25 

inches. 

Pretreatment 

Alodiiie 1 20 I 

Alodiiie 120 1 

Alodine 120 1 

Alotline 5700 

Alodiiie 5700 

Alocline 5700 

Cheniidize 727 

Cheniidize 727 

To ensure that the vendors of the candidate coatings and pretreatments could supply a consistent product 

from lot to lot. repeatability testing was conducted. This testing consisted of EIS testing, adhesion testing. end 

compatibility testing to Spirit i 26 (cleaner used on coatcd surfaces). The EIS testing showed very little performance 

difference for the candidate configurations. One notable exception is the performance of Deft primer. The spectrum 

for lot 2 of Deft prinier was niorc typical of a spectrum for a coating performing as a barrier. Lots I and -3 were niore 

indicative of a damaged coating. Visual examination of the Deft primer coupons showed blister on the Deft primer 

over Cheinidize 727 lot I coupon and on all of the lot 3 Deft pritner coupons. Despite the variation In the Deft 

primer performance. the second and third lots still indicate performance equal to or better than the first lot tests. 

Primer l’opcoat 

Deft 44GN 7 Deft 03w127 

Hentzcn OS5 10WEP-X/0551 ICEH-X Hentzen 4636WUX-3/4600CHA-SG 

Lord 9929.443 Lord A276 

Deft 44GN7 Deft 03w127 

Hentzen 055 10WEP-X/055 1 ICEH-X Hentzen 4636WUX-3/4600CHA-SG 

Lord 9929AIB Lord A276 

Lord 9929A/U Lord A276 

Deft 44GN7 Deft 03W127 

The adhesion repeatability testing showed no significant difference from the first to second lot for all the 

candidate configurations. Lot iiumber three howewr. is significantly lower in adhesion than the previous two lots 

for all niaterials. Looking at the three charts it is possible to deduce that the drop is independent of any of the 

variables that were being tested. The following variables were then reviewed for a possible answer to the drop in 

strength: adhesive. temperahirc, hunlidity, test procedures, and personnel. Adhesive, temperature, humidity, and test 

procedure all turn oiit to be negative. However, the variation in bonding the test stubs and preparing the bond site is 

suspected to have been great enough from one analyst to another to causc the drop in bond strength. The results of 

the repeatability testing of chemical compatibility of Spirit 126 to three lots of the candidate coatings showed no 

variation from lot to lot. 

Conclusion 

The coating configurations acceptable for use on the SRB alunlinutn components are list in the Table 2*. 

Note that the pretreatment and primer only configuration is acceptable for sufiices which have the coating removed 

after each flight cycle. The primers and topcoats listcd are also qualified for stainless steel surfaces. For furtlier 

information about this test program, please refer to CPC-025-00MP “Alternate SRB Aluminum Coating System 

Qualification Test Report” [IO). 

l‘able 2. Coating Configurations Heconiniended for Use on SKB Aluminum Components 
Heferences 

4. 

5. 

6. 

7. 

s. 

9. 

10. 

“Coating: Polyurethanc. High-Solids,” MlL-C-852SSU (AS), Military Specification. I3 May 1988. Irgbrtnution 

Handling Simicw, 1 999. 

“Flaininability. Odor, and Offgassing Requirements ant1 Test Procedures for Materiels in Environments That 

Support Combustion“ NHB 8060.1 B, section 4.1. 

”Stdilrd Practice for Testing Water Resistance of Coatings Using Water Immersion’‘ ASTM: D X70-97. 

.4nnrrul Book of ASTM Stctnclurcls Section 6 Paints. Reluted Coutings, urd Aromutics. Vol. 06.0 1, ASTM. Wcst 

Conshohocken, PA. 1999. pp. 84-86. 

“Standard Test Method for Effect of Cleening and Chemical Maintenance Materials on Painted Aircraft 

Surfaces” ASTM F 502-93, ASTM, 1nfi)miurioii Hcirrdling Seniw.~, 1999. 

“Standard Test Method for Mandrel Bend Test of Attached Organic Coatings” ASTM D 522-93a. Annual 

Book o/’ AS7J1 Stondurtfs Section 6 I’oinr.s, Itd(i[t?d Cotrririgs, arid Aroniutics. Vol. 06.0 1, ASTM. West 

Conshohocken. P4. 1999, pp. 29-32. 

“Standard Test Method for Pull-Off Strength of. Coatings Using Portable Adhesion Testers,” ASTM D 4341 - 95, ASTM. Infimiurion Hondlitig Scwict~s, 1 999. 

“Standard Test Method for Tensile and Tensile Atlhesion Properties of Rigid Cellular Plastics,” ASTM: 

Ul623, Antmu1 /hok,for ASlBl S~undm~d.c.jut~ Plustics &don 8, Vol. S,OIT ASTM, Philadelphia, PA. 1093. 

pp. 494-499. 

Thcinrul Quulificutioii Tmiiig of un .41twnute Aluniinurn Coating ,Q.vtmz jiJr the SRB. USA SRB Report No. 

SA-AR-0040-2000 

Look, L.. Altetnotive SRh’ Aliitninftm Couting Svstem f)onn Sekt Test Report, USBI Keport No. CPC-070- 

98MP. 

Zook. L.. Altertwii,e SRB Ahuttimurt~ Coccting System Quul$fimtion Test Report, USBl Report No. CPC-025- 

OOMP. 
Triva-ent ChromiumlOrganically- lodified Silicate Composite Coatings for Corrosion Protection of 

Aluminum Alloys 

Elvira Stesikova, Tammy L. Metroke, Olga Kachurina and Edward T. Knobbe* 

Departnient of Cheniistni and the Environmental Institute. Okiahonia State Universi<v, Stillwater. OK 740 78 

Address: 003 LSE, Stillwater, OK 74078 

Phone : (405)744-9994 

knobbe@okway.okstate.edu 

Abstract 

Deposition of either trivalent chromium, Cr( 111)-based, or Cr(V1)-based, conversion coatings onto aluminum 

2024-T3 alloy (AA) was followed by the deposition of hybrid silicate materials; these coatings were produced by 

hydrolysis and condensation of tetraethylorthosilicate!vinyltrimethoxysilane~3-( trimethoxysilyl)propyl-methacrylate. 

The potentiodynamic study of the Cr(VI)/silicate and Cr( III)/silicate composite coatings showed a significant shift 

of the polarization curves toward higher values of corrosion potential and lower values of corrosion current, relative 

to bare AA. Moreover, augmentation of corrosion resistance from 2.8 kRcn? for bare AA, to 79-95 k2cm’ for the 

hybrid silicate coatings and hrther to 162-362 kncm’ for the composite films was observed. The results of 

potentiodynamic polarization and salt spray analysis ultimately suggest that AA with the composite coatings resist 

corrosion much better than those with bare surface or single layer silicate coating. The impact of the Cr(lI1) 

conversion coating on corrosion resistance of the composite films is comparable to that of the Cr(V1)-based surface 

pretreatments. This implies that the environmentally compliant and non-toxic trivalent chromium conversion 

coating is a very good alternative for the hazardous and carcinogenic hexavalent chromium treatment. 

Introduction 

Corrosion of aluminum alloys (AA) remains a subject of intensive investigation due to the everyday 

importance of these materials [ 1-41. To prevent interaction between the metal and the environment, protective 

layers such as chromate conversion coatings [5], e.g. Alodine. are currently used. Such coatings replace the native 

metal oxide film, e.g. alumina, with another oxide layer, thus converting the surface of the substrate to a more stable 

state, less susceptible to corrosion [6-71. Despite excellent protection of the metal and inhibition of the cathodic and 

anodic corrosion reactions [8], Cr(V1)-containing compounds are carcinogenic, very hazardous soil and groundwater 

pollutants [9]. 

Extensive research for alternative non-toxic corrosion inhibitors resulted in a number of novel coating 

processes, including rare earth-based conversion coatings [ 10-1 I], Co-rich oxide layers [ 121, and trivalent chromium 

films [ 131. The latter were formed in a simple one-step immersion process yielding films on aluminum alloys that 

are comparable in corrosion resistance to those of conventional Cr(V1)-based conversion coatings but without their 

toxicity [ 141. This finding prompted extensive investigation of corrosion protective properties of Cr( 111) conversion 

films on AA surfaces. 

Recent studies have shown hybrid silicate films to be good corrosion protective coatings for AA surfaces 

[15]. However. 

significant improvement of AA corrosion resistance can be achieved when a silicate coating is combined with a 

corrosion inhibiting conversion layer [ 161, yielding a composite film. In this study, two types of composite coatings, 

Cr(V1)isilicate and Cr(II1)isilicate. were investigated using polarization curve analysis and salt spray testing. Their 

properties were compared to those of the silicate films coated on bare AA surface free of conversion layer. The 

results reveal that the presence of conversion coating, either hexavalent chromium. Le. Alodine, or trivalent 

chromium, in the composite film augments the inhibition of corrosion of AA. Based on their equally good 

performance, the trivalent chromium conversion coating is suggested as a good alternative for the hexavalent 

chromium-based treatment. since it does not have Alodine s toxicity. 

These films function by providing a good barrier to the penetration of corrosion initiators. 

1 
Experimental 

hdateriuls 

Silicate precursors tetraethyl orthosilicate, TEOS, 3-(trimethoxysilyl)propyl methacrylate, MTMOS, and 

vinyltrimethoxysilane, VTMOS, were purchased from Aldrich and were used as received. Sodium chloride (reagent 

A.C.S.. Spectrum) and nitric acid (NF grade, Fisher) were used without further purification. Water was purified by 

an ion-exchange and filtration system to produce specific resistivity 18 MRm*cm. 

ORMOSIL Preparation 

A series of hybrid silicate systems was synthesized based on TEOSNTMOSIMTMOS precursor mixture. 

Various amounts of 0.05 M aqueous solution of nitric acid, pH=2, were added to the mixture to achieve the desired 

[Si-OR] [HlO] molar ratios of 1 : 1, I :2 or 1 :3. The mixtures were allowed to stir for one hour. 

Preparation of Trivalent Chromium Solittion for Conversion Coatings 

A trivalent chromium solution was prepared according to the procedure developed by Pearlstein and 

Agarwala [13]. The solution was prepared by adding 0.6 g of Cr4(S04)S(OH)2 (XoO Cr203 and 23-23'0 Na2S04) 

and 0.8 g of K2ZrF6 to one liter of deionized water under continuous stirring for several hours. This solution was 

then allowed to stand for one week. The pH of the solution was found to decrease from 5.0 in the freshly prepared 

to about 3.7 in the "aged" solution. 

Coating Techniques 

Aluminum 2024T3 alloy substrates used for both polarization measurements and salt spray testing were 

freshly degreased and deoxidized using the following cleaning process. AA substrates were, first, treated in Oakite163 cleaner solution for 15 minutes at 65 "C, and then in Turco Smut-Go deoxidizing solution for 7- 10 minutes at 25 

"C under rigorous air agitation. Each one of these treatments was followed by thorough rinsing for 2 minutes using 

tap water at 50 "C. 

AA surface pretreatment was done using either commercial Alodine 1200 solution or trivalent chromium 

solution. AA substrates were immersed into Alodine 1200 solution for 2 minutes to yield a uniform, golden 

conversion coating on the surface. In order to produce Cr(lI1) conversion coatings, AA substrates were sprayed with 

the trivalent chromium solution for 10 minutes. The synthesized hybrid silicates were subsequently applied onto 

bare or pretreated AA by a spray coating technique using commercial airbrush setup. The coatings were allowed to 

dry at ambient conditions for at least 24 hours prior to their characterization. 

Polarization Measitrements 

Electrochemical measurements were performed using a CV-50-W unit and a three electrode cell equipped 

with a platinum counter electrode. a AgiAgCl/CI- (3M KCI) reference electrode and an AA 2024-T3 panel as the 

working electrode. The latter was either coated or not coated with a film and had an exposed area of 0.36 cm2. All 

measurements were conducted in an aqueous 1M NaCl working solution at 25 f 1 "C. The reported values of 

potentials both shown in the polarization curves and listed in the tables are given relative to the AgIAgCIICIreference electrode. Oxygen was removed by purging the solution with purified nitrogen during the polarization 

measurements. 

In order to reach steady potential, the electrodes were kept in the working solution for 30 minutes prior to 

the measurements with the electrical circuit open. Then the acquisition of polarization curves was started from this 

open circuit potential, with a constant sweep of 1 mVisec. Corrosion current values, I,,,, reported herein correspond 

to a 50 mV stretch between the cathodic and anodic parts of the polarization curve. Corrosion resistance was 

calculated using the equation: so, = 5OmVi' I,,. This differs from the previously described definition of the 

corrosion resistance,' however, it allows for the derivation the parameter, so,, for the entire pool of polarization 

curves collected in this study regardless of their shift along the abscissa. Pitting potential, Eplt, corresponds to the 

point of sharp rising of the anodic current in a linear scale. 
.4ccelerated Salt Sprq, Testing 

and ASTM B 1 17. 

Ormosil-coated test coupons were placed in 59.6 salt spray at 35 f 1.7 "C for 168 hours as per Mil-C-554 1 

Results and Discussion 

Coniparison of Trivalent Chromium and Alodine Conversion Coatings 

The impact of Alodine and trivalent chromium conversion coatings on the electrochemical and corrosion 

resistance behavior of 2024-T3 AA was studied using potentiodynamic polarization curves and accelerated salt 

spray testing, respectively. Electrochemical analysis of Alodine was hindered by the solubility of the treatment in 

water. Figure 1 depicts the acquired polarization curves for the bare AA (trace A) and AA substrates coated with the 

trivalent chromium conversion coatings by spray application (trace B). The results indicate that the presence of the 

Cr(II1) coating shifts corrosion potentials of AA substrates to more positive values, converting the surface of the 

substrates to more stable states less susceptible to corrosion. This behavior is anticipated for chemical conversion 

coatings. Thus, within the accuracy of the experiment, f 16 mV. the corrosion potential of bare AA was measured 

to be -725 mV in 1M NaCl which is in the agreement with data published by other authors I-. This value is 

approximately 160 mV lower than that of the Cr(II1)-coated AA substrates, which for different exposure times and 

the deposition techniques appears in a relatively narrow range of -560 k 22 mV. 

-400 1 b 

-500 

-700 

-800 

-8 -6 -4 -2 

Log I (Alcm 2) 

Figure 1. Potentiodynamic polarization curves measured in aqueous 1M NaCl solution at 25 "C for (a) bare 

2024-T3 aluminum alloy sample and (b) aluminum alloy samples coated with Cr(II1) conversion layers by 

spraying coating. 

The corrosion resistance values for AA substrates coated with Cr( 111) conversion layers were determined 

from the corresponding polarization curves as it described in experimental section. For the Cr(II1) conversion layers 

produced by spray application, the resistance values were in the range 18.1 f 2.7 WZ*cm'. The data indicate that 

Cr(II1) coated substrates exhibit significant elevation of corrosion resistance, as compared to that of uncoated AA, 

2.8 kR:km'. Together with the corrosion potentials, the corrosion resistance data confirms that formation of the 

Cr(II1) conversion layer on the surface of aluminum alloy provides it with better corrosion stability. 

Figure 2 shows the results of 168 hour salt spray tests for bare AA, Alodine, and Cr(II1)-treated AA 

substrates. Both the Alodine and trivalent chromium conversion coating exhibited remarkable corrosion resistance, 

significantly better than that of the bare AA substrate. No pitting was observed on the Alodine-treated panels and 

only a few small pits were observed for the Cr(lI1)-treated panels. Additional specimens using hybrid coatings on 
top of either Alodine or Cr (111) conversion coatings were prepared in order to determine if the presence of a 

conversion coating under barrier sol-gel coatings could produce composite films with improved corrosion resistance. 

Figure 2: Results of 168 hour salt spray test for (a) Bare AA, (b) Alodine-treated AA, and (c) 

Cr(lI1)-treated AA. These photos represent approximate 2” x 2” segments from the center of a 

3” x 5” coupon. 

Conversion LaycrtORMOSIL Composite Film 

Figure 3 shows potentiodynamic polarization curves acquired for non-coated AA (curve a}, AA coated with 

hybrid silicate coatings prepared using [Si-OR]/[H20] molar ratios of I :4 (b), composite coatings containing Cr( VI) 

(e). and Cr( 111) (d) conversion layers, respectively. The latter was produced by spraying the trivalent chromium 

solution onto AA substrate for 10 minutes. The results indicate that the coatings studied in this experiment yield a 

significant shift of the polarization curve toward higher values of the corrosion potential and lower values of the 

corros~on current. 

Important electrochemical characteristics assessed from the polarization curves acquired for AA substrates 

coated with different hybrid coatings with and without conversion layers are listed in Table 1. Thus, E,,, value is 

changed from -7 19 mV for a bare AA to -582 mV for the 1 :4 hybrid silicate coating and further to 459 and -503 

mV for the Cr(V1) and Cr(ll1) composite coatings, respectively. The corrosion current values decreased by two 

orders of magnitude for the coated aluminum alloys, when compared to the non-coated AA. It is noteworthy that 

corrosion resistance of the bare AA is very small, 2.8 kR*cm’, whereas KO, values for the coated AA samples fall 

in the range of 80-350 kR*cm’. These observations provide strong evidence that corrosion of AA substrates is 

significantly inhibited by the presence of the composite coating. 

More detailed analysis of the corrosion data implies that both composite coatings exhibit much better values of 

I,,. and increased values of E,, and KO,. The latter parameter is of special importance, since it reflects a two to 

four-fold increment of corrosion resistance of the composite films relative to the single layer hybrid silicate coatings. 

Thus, for the 1 :J hybrid silicate coating. KO, is changed from 79.2 kR*cm’ for the single layer coating to 350.0 and 

28 1 .O kR*cm’ for the composite coatings containing Alodine and Cr( 111) layers, respectively. 

The study of composite films allows for a comparison of the corrosion characteristics of the conversion 

layers. which is not possible otherwise due to the solubility of the Alodine films in aqueous solutions. Analysis of 

the electrochemical characteristics of the AA substrates coated with composite films containing Cr(V1) and Cr( 111) 

conversion layers indicates insignificant differences in the I,,,, E,,, and KO, values between these two systems. 

This suggests that corrosion protection of AA finished by either Cr(V1) or Cr(1II) conversion layers are equivalent. 

This is a rather significant understanding, since it offers environmentally compliant Cr(II1) treatment as an 

alternative to toxic and hazardous Cr(V1)-based protection of Alodine films. 

4 
-400 1 

-400 - 

-500 

-600 . 

-700 

-800 4 1 1 m 

-9 -7 -5 -3 

C 

-800 

-9 -7 -5 -3 

Log I (A/cm2) 

Figure 3. Potentiodynamic polarization curves measured in aqueous 1 M NaCl solution at 25 "C for non-coated AA 

2024-T3 (a); AA coated with: 1:4 hybrid silicate (b), composite films of Alodine and 1.4 hybrid silicate (c). 

composite film of Cr (111) conversion layer and hybrid l:4 silicate (d). 

5 
Table 1. Electrochemical characteristics derived from potentiodynamic polarization curves for 2024-T3 

aluminum alloy substrates coated with different hybrid coatings with and without conversion layers. 

Coating Conbersion Layer Water Ratto I,; IO‘, E,,,. E,,,, K*m 

A, cm’ ni V mV k~ 1 cm’ 

None I82 -719 -540 2.8 

Hybrid Silicate 

1:l 5.89 -450 -419 84.9 

1 :2 5.25 -512 -150 95.3 

1 :4 6.3 I -582 -475 79.2 

Hybrid SilicateiCr(V1) 

Hybrid Silicate;Cr( 111) 

I:1 1.38 -460 -453 362.0 

I :2 3.10 -507 481 162.0 

I :4 2.00 -459 -403 350.0 

I:I 2.40 373 -450 208.3 

1 :2 1.60 -599 -439 312.5 

1 :1 1.78 -503 -409 28 I .o 

From the results of the potentiodynamic study, it can be inferred that the composite films comprised of both 

hybrid silicate and conversion layers provide corrosion protection of AA. which is superior to that of either one of 

the film components. This is further supported by the results of accelerated corrosion testing conducted for the same 

specimens. Figure 4 shows images of a bare AA substrate (a) and those coated with the 1 :4 hybrid silicate film (b) 

and composite films (c,d) exposed to a corrosive salt fog atmosphere for 168 hours. Based on the amount of pitting 

observed on these panels. it is possible to conclude that AA with the composite coatings resists the corrosive 

environment in a manner superior to AA coated with the single layer silicate coating or no coating at all. 

Conclusions 

AA substrates coated with composite films comprising both hybrid silicate and conversion layers, trivalent 

or hexavalent chromium, exhibited excellent corrosion resistance. The impact of the trivalent chromium conversion 

coating on the corrosion resistance of the composite films is comparable to that of the Cr(V1)-based conversion 

coating, i.e. Alodine. This implies that the trivalent chromium conversion coating, which is an environmentally 

compliant and non-toxic. is a very good alternative for the hazardous and carcinogenic Cr(V1)-based surface 

pretreatments. 

6 
A 

B 

C 

D 

Figure 4. Aluminum 2024-T3 alloy substrates exposed to salt fog atmosphere at 35 “C for 168 

hours. Coating systems: (A) bare AA, (B) AA coated with 1:4 hybrid silicate, (C) composite 

films of Alodine and I :4 hybrid silicate, and (D) composite film of Cr (111) conversion layer and 

hybrid 1:4 silicate. These photos represent 3” x 5” coupons. 

7 
Acknowledgement 

This research was supported by the U.S. Department of Defense through Prime Contract k RCSR-98-D-SBIR 

ivith Lear-Siegler Service, Inc., subcontracted to OSU through SBIRE under subcontract number SBIRE-S98-00 1. 

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6. 

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13. M.P. Schriever, Non-Chromated Cobalt Conversion Coating, European Patent 0488430 A?. 

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5,30425 7. 

I.). V.S. Aganvala. Trivalent Chromium Solutions for Applying Chemical Conversion Coatings to Aluminum 

Alloys: Naval Airfare Center, Aircraft Division, Code 434000A, MS-3, Patuxent River. MD. 

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C. Blank. B. Lavelle and G. Mankowski, Corros. Sci. 1997,39,495. 

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391. 

R. G. King, Surface Treatment and Finishing of Aluminium, Pergamon Press, Oxford, 1988, pg 5 I. 

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M Kabasakaloglu.; Aydin, H.; Aydin, H.; Aksu, M.L. Materials and Corrosion. 1997,48, 744. 

N. I. Sax. Dangerous Properties of Industrial Materials, Fifth Edn, Van Nostrand Reinhold Company, New 

York, 1979, pg. 504. 

8 
HVOF Thermal Spray Coatings as an Alternative 

to Hard Chrome Plating on Military Aircraft 

Bruce D. Sartwell 

Naval Research Laboratory 

Code 6 170 

Washington, DC 20375 

I sartwelliiunrl.navv.mil I (202) 767-0722 

Introduction 

Functional hard chrome plating is a critical process associated with manufacturing and maintenance operations 

on aircraft, vehicles, and ships, both in the civilian and military sectors. Since chromium is on the Environmental 

Protection Agency list of I7 toxic materials, fairly stringent air and wastewater emission limits have been 

established by the EPA. Also, hard chrome plating utilizes chromium in thc hexavalent state (hex-Cr). which is a 

known carcinogen. As a result, the Occupational Safety and Health Administration (OSHA) has established 

permissible cxposure limits (PEL) for hex-Cr in the workplace at a level of 0.1 mgim’. However, recent studies 

have indicated that the cancer risk is significantly increased at this level, so it is anticipated that OSHA will issue a 

new hex-Cr PEL that is substantially less than the current value. This would unquestionably increase the cost of 

plating operations that may be prohibitive in certain activities. 

Compliance with increasingly stringent regulations under the broad category of environment, safety and 

occupational health (ESOH) is leading many organizations to investigate alternative coating processes. However, it 

is also found that in many instances the in-service perfonnance of hard chrome plating is not satisfactory, so some 

organizations have investigated and qualified alternative processes solely on the basis of performance, but these 

have generally been on a piecemeal basis instead of an across-the-board qualification. As a result of these types of 

studies. it is apparent that as opposed to many ESOH-drivcn projects that seek an alternative processimaterial that is 

the ”next-best thing” to the presently used process, for chrome plating replacement, it is possible to identify 

alternative processes that not only address ESOH issues but also improve performance. Improved perfonnance is 

then translated into reduced life-cyclc costs of the affected system. 

In ternis of identifying those technologies that are viable candidates for replacing hard chrome plating, it is 

essential to understand the current uses for chrome. Looking specifically at the aircraft industry, chrome plating is 

used in several different ways: 

0 As a wear-resistant coating, typically applied by OEMs to thicknesses ranging from 25 to 100 micrometers 

(0.001” to 0.004”), mostly for external wear areas 

As a rebuild coating, up to 0.5 mm (0.020”) thick, to bring worn and/or machined components back to 

their specified dimensions 

As a light abrasionicorrosion barrier for many internal areas (designated as thin dense chrome or flash 

chrome), typically 5- I0 micrometers thick. 

The largest uses of hard chrome in the aerospace industry are: 

Hydraulic actuator rods 

Landing gear (gas-over-fluid hydraulics) - inner cylinders, axles. and pins 

Journals and shafts in engines 

Lugs and other wear surfaces 

Internal diameters (ID’S) of hydraulic and landing gear outer cylinders (frequently thin dense chrome) 

Due to the types of components and applications for which hard chrome is currently used in the aircraft 

industry, there arc many types of coating technologies that would not be viable alternatives even though they can 

produce coatings with superior properties. These include chemical vapor deposition and the vacuum-based coating 
technologies such as ion plating, sputtering, and cathodic arc deposition. The types of coatings that are most widely 

1,iewed as being capable of replacing hard chrome are the thermal spray technologies. especially high-velocity 

oxygen-fuel (HVOF) thermal spraying. With this process, the coating material, in powder form, is fed into the 

combustion chamber of a gun where a fuel. such as hydrogen, ethylene, or kerosene, is burned with oxygen. and the 

heated and softened powder is expelled as a spray with the supersonic gases. Powders deposited using HVOF 

include pure mctals, metal alloys, cermets, and certain ceramics and polymers. The reason why HVOF is the 

preferred thernial spray process for chrome replacement is because it produccs low-porosity (< 1 “A), higlily adherent 

(bond strength > 80 MPa ( 10.000 psi)) coatings which generally have an oxide content less than I”.” even for 

reactive metals. A5 it tkxiblc dry-coating technology it avoids high-volume waste streams and provides a choice of 

coating materials for each application. The use of hard chrome is so widespread that there is no single replacement 

technology or material. hut the HVOF cobalt-cemented tungsten carbides are some of the easiest materials to spray 

and have shown the widest range of successful applications. 

One of the clear advantages of HVOF is the high deposition rates that can be achieved. The instantaneous 

deposition rate is approximately 50 micrometers (0.002”) per minute although in normal operation the HVOF gun is 

mounted on a robot or other articulating arm and the component being coated is also manipulated (e.&., a cylinder 

will be rotated). Figure I is a photograph of an HVOF WCKo coating being applied to a Boeing 737 nose landing 

gear cylinder. which is approximately 0.5 meters long and 0.1 meters in diameter. It generally takes less than 20 

minutes to deposit a 100-micrometer-thick (0.004”) coating onto this component. 

Figure I. HVOF thermal spraying of WCiCo coating onto a nose landing gear cylinder from a Boeing 737 

Establishment of DoD Program and Generic Materials Testing 

Within the C.S. Department of Defense (DoD), the Hard Chrome Alternatives Team (HCAT; www.hcat.org) 

was fornied in 1996 under the principal sponsorship of the DoD Environmental Security Technology Certification 

Program. Its objective is to demonstrate and validate HVOF coatings as a cost-effective and technologically 

superior alternative to hard chrome in most maintenance operations at Navy, Air Force, and Army aircraft overhaul 

and repair (O&R) depots and in manufacturing operations at DoD OEMs. The organizations that comprise the 

HCAT include DoD research laboratories. aircraft depots, aircraft OEMs, materials testing laboratories. an HVOF 

cquipnient manufacturer and an FAA-certified repair facility that has chrome plating and thermal spray capability. 

The HCAT initially sought a more generic qualification of HVOF coatings by selecting base materials that 

Lvere representative of the families of materials onto which hard chrome is deposited, applying two different HVOF 

coatings, and then conducting materials testing to demonstrate equivalent or superior performance. The base 

materials that were selected were AIS1 4340 high-strength steel, ?075-T73 aluminum alloy, and PH 13-8Mo stainless 

steel. The HVOF coatings were WCKo (83%11?%) and Tribaloy 400, a cobalt-molybdenum-chromium alloy. 

deposited to a thickness of 100 micrometers (0.004”). The microhardness values for the three coatings were as 

follows: 
Hard chrome IO. I GPa 

WCICO 12.8 GPa 

Tribaloy400 5.7GPa 

Extensive fatigue. corrosion, and abrasive wear testing was conducted on the coated materials compared to 

hard chrome deposited to the same thickness in accordance with standard specifications for aircraft components. 

The results of these studies have been reported previously.’.’ They indicated that the fatigue performance of the 

HVOF coatings either met or exceeded that of the hard chrome. The cabinet corrosion testing (ASTM B I 17) 

indicated virtually no differencc between the three coatings and the abrasive wear testing indicated superior 

performance for the HVOF WCiCo because of its higher hardness, but inferior performance for the Tribaloy 400. 

Although the cabinet corrosion testing showed essentially equivalent performance for the HVOF coatings 

compared to hard chrome, atmospheric corrosion testing was recently completed on thc various coatingisubstrate 

combinations, with the results being somewhat different. In this case, the test coupons consisted of IO cm by IS cm 

(4” x 6”) flat plates onto which the three coatings were deposited to a thickness of 100 micrometers. The specimens 

were mounted onto atmospheric test racks near the scashore at the Navy Marine Test Facility in Key West, FL. 

Some ofthe specimens were sprayed with a salt water solution once a week to accelerate the corrosion. 

It can be seen in figure 2 that both the hard chrome and the Tribaloy coatings have extensive corrosion whereas 

the WCKo coatings are virtually pristine. As stated above, this result is significantly different from that of the 

cabinet testing, which might be a further indication that the B I I7 test does not accurately reflect corrosion behavior 

in the real world. 

Figure 2. Representative specimens of 4340 steel plates coated with HVOF WCiCo and Tribaloy 400, and hard 

chrome after 18 months atmospheric exposure plus once weekly spraying with salt water 

Execution of Separate Projects on Qualification of HVOF Coatings as a Hard Chrome Replacement 

All of the previous studies demonstrated what might be called the technological viability of HVOF coatings as 

a replacement for hard chrome plating. But it was clear through discussions with individuals who make up the 

stakeholder community within the DoD aerospace sector (e.&., repair depot technical representatives and 

engineering authorities, weapons systems program managers, and structural engineers from the three services and 

the OEMs) that it would not be possible to have a generic qualification of HVOF for all types of aircraft 

components. Because hard chrome plating does in fact protect a variety of aircraft components, this means that 

different stakeholders would be involved in the qualification process for each type of component. As a result, the 

HCAT has established partnerships with two other DoD organizations that execute projects related to qualifying and 

inserting technologies that can have an impact related to environmental concerns (e.&., pollution prevention) and 
also litk-cycle costs. l’he tirst is the Joint Group on Pollution Prevention (JG-PP; www.jgpp.com) and the second is 

thc Propulsion Environmental Working Group ( PEWG; www.pewg.com). 

lhe partnership with the JG-PP has led to the establishment of separate projects related to qualitication ot 

HVOF thermal spray coatings on the following classes of aircraft components: 

Landing Gear - inner cylinders, axles, pins, actuators (in conjunction with Boeing and the landing gear 

manufacturers. BF GoodrichiMenasco, Heroux and Messier-Dowty). 

Propeller Hubs (in conjunction with Hamilton Sundstrand) 

Hydraulic actuators for systems other than landing gear (OEMs to be identified) 

Hclicopter Dynamic Components - including transmission and rotor head components (in conjunction with 

Boeing Philadelphia and Sikorsky) 

The partnership with the PEWG has led to a project related to replacement of hard chrome on gas turbine 

engine components and is being executed in conjunction with GE Aircraft Engines, Pratt & Whitney, and RollsRoyce Allison. 

The execution plan for each project tirst involves the development of Joint Test Protocols (JTP) following a 

methodology de\wloped by the JG-PP. The JTP defines all of the testing required for full qualification of the 

alternative process which generally includes both materials testing on coupons for fatigue, corrosion, wear, and 

other properties, and actual component testing involving installation of coated components into test rigs and into 

operational aircraft where performancc is tracked over extended periods of fmc. In addition to preparation and 

execution of the JTPs. the projects also involve establishing production-level HVOF facilitics at the appropriate 

military aircraft maintenance facilities, training personnel at those facilities, analyzing costs. and developing 

standards and specifications for application, grinding. and stripping of the HVOF coatings on the categories of 

aircraft components. 

Execution of Project on Landing Gear 

The remainder of the paper will be concerned with the execution of the project related to qualification of 

HVOF thennal spray coatings as a chrome replacement on landing gear since that is the one closest to completion. 

This is a joint project between the United States and Canada. In 1997, the Canadian Department of National 

Defence (DND) and Industry Canada (IC) became interested in the HCAT program because of the considerable 

number of military aircraft in DND and because Canadian companies manufacture more than two thirds of the 

landing gear on military and commercial aircraft in North America. As a result, a formal Project Arrangement was 

established between the two countries and a Canadian team (C-HCAT) was formed to execute some of the testing. 

In July 1998 a meeting was held that involved members of the U.S. and Canadian HCAT teams and 

representatives from all of the DoD, DND and OEM stakeholders for the purpose of developing the JTP for landing 

gear. It was decided that it would be issued in two parts, with the first part describing the materials (coupon) testing 

and the second part describing the component (rig and flight) testing. Part I was complctcd and was endorsed by the 

stakeholders in 1999 and testing is in progress. 

Only two types of HVOF coatings are being evaluated in the landing gear project on three base materials. 

Testing is also being conducted on hard chrome plating as a baseline. The U.S. team is evaluating WC/Co 

(83O/b/ 17%) and the Canadian team is evaluating WC/CoCr (86Yb/100/b-4%) deposited onto 4340, 300M. and Aermet 

IO0 steels. Materials testing includes fatigue, corrosion. sliding wear, impact (both particle erosion and ball drop), 

and hydrogen embrittlement. (The entire 50-page JTP is available at uww.hcat.org). 

In order to ensure reproducibility in the test results, the JTP specifically defines all aspects of the specimen 

preparation, coating deposition, and testing parameters. For coupon preparation. the machining, heat treatment, 

grinding. etching, shot peening (if applicable), and grit blasting (if applicable) are all described. Deposition of the 

hard chrome is specified to be in accordance with Military Standard 1501 supported by commercial standard QQ-C320. Deposition of the HVOF coatings is specified to be in accordance with Boeing Aircraft Corporation Standard 

585 1, Class 2, Type I with hydrogen used as the fuel gas. Coating thicknesses are specified at either 75 micrometers 

(0.003“) or 250 micrometers (0.0 Io”). 
Because the majority of components onto which hard chrome is currently applied are fatigue-sensitive, special 

attention has been paid to the internal stress of the HVOF coatings. Based on tlie generic studies conducted earlier 

that showed a correlation between compressive stress and improved fatigue, it was determined that when the 

coatings are applied to coupons or components, they should also be simultaneously applied to almen strips (which 

are commonly used for measuring stress induced by shot peening). For the HVOF coatings being evaluation in the 

landing gear project, almen N values ranging from 3 to I2 (compressive stress) are specified. 

Surface Finish 

Surface finish is a critical issue, especially for items such as hydraulic rods that run against seals. For this type 

of application chrome plate is typically specified with a 0.2-0.4 micrometers (8-1 6 microinches) finish (average 

roughness, or Ra value). This pennits the surface of the chrome to hold some hydraulic fluid in its pattern of 

microcracks. However, because of its higher hardness, a WC/'Co surface with a finish grcater than 0.2 micromcters 

can potentially damage tlie seal material. Therefore, in the JTP, the surface finish for the HVOF coatings is 

specified at either 0. I or 0.2 micrometers. It is becoming clear. however, that merely defining tlie Ra value is 

inadequate and that for these types of coatings it may be necessary to adopt a more thorough specification of surface 

finish to better define the topography. 

Fatigue 

The fatigue tests are being conducted in accordance with ASTM E466-96 which specifies axial load control at 

constant amplitude. The number of stress levels to be evaluated is four, with five specimens tested at each stress 

Icvel. In general, hourglass geometry is used for the specimens, although in a few cases smooth gage is used. 

Coating thicknesses are either 75 or 250 micrometers, tlie R values for the fatigue test are either -1 or 0.1. and the 

environment is either laboratory air at ambient temperature or 40" C, or immersion in a 3.5% haC1 solution at 

ambient temperature. More than I300 separate fatigue tests will be conducted. 

Some of tlie results have been obtained for the fatigue testing on the HVOF WCiCo coatings. Figure 3 

pro\ides the data an cycles to failure at different stress levels for tlie 75-micrometer-thick hard chrome and HVOF 

WCiCo coatings on 4340 steel with an R value of 0. I. The figure also shows the effect of shot peening of tlie base 

material prior to application of the coating. The results indicate superior performance for the HVOF coating and 

also indicate the superior performance associated with the shot peening. 

I 

Figure 3. Results of fatigue testing for peened and un-peened 4340 steel hourglass specimens onto which hard 

chrome plating or HVOF WCKo coatings had been applied 
Wear tests are being conducted to provide information on manufacturing variables and wear conditions 

including coating material, surface finish, lubrication, side loads. velocities. type of wear, and other wear 

environment factors. Two test methods arc being employed: 

Oscillating pistonibushing at low frequency and long stroke with a load applied to the bushing 

perpendicular to the direction of motion ofthe piston (see figure 4) 

Fretting block-on-shoe test at high frequency and short stroke with a load applied to the shoe 

perpendicular to the direction of motion of the block (see figure 5) 

The piston and bushing oscillating wear tcst is being used to reflect typical conditions of use under a side load. 

The f'retting wear test is being used to reflect typical actuator piston dithering or vibration movement. The shoe and 

block materials correspond to the piston and bushing/seal materials. The base material for thc piston and shoe is 

4340 steel and the hard chrome and HVOF coatings arc applied to only these components. Table I provides the 

wear material test matrix. 

Because there are so many variables in the wear testing, a statistical design-of-experiments methodology is 

being followed. During testing of the pistonibushing. the coefficient of friction is monitored and then subsequent to 

the test, thc coatings are examined to measure the extcnt of wear, if any. 

Table 1. Wear test material matrix 

Piston/coating 

material (Fretting 

ShoeKoating ) 

4340iHard Chrome 

Plate 

4340'HVOF WCco 

3340, HVOF M'CBushing materia1 

(Fretting Block) 

4340 steel 

~~ 

AhlS 4646 (AI-Nibronze) 

Anodized aluminum 

Caron B on AI 

bronze 

Nitrilei'PTFE Tscals ill 4340 

** _- _- _IIC_ 

Figure 4. Cross-sectional schematic of piston and 

bushing oscillating wear test 

Figure 5. Cross-sectional schematic of fretting test 
Flight Testing 

Flight testing of HVOF-coated components which are normally chromc-plated is an essential part of- the 

program. Several components have becn coated and arc either currently in flight testing or are ready to be installed 

on operational aircraft. Figure 6 is a photograph of a Navy P3 (four-engine turboprop) main landing gear onto 

which a 100-micrometer-thick WC/Co coating has been applied to the piston (center of photograph) and axle 

journals. These components were installed in April 1999 and were inspected in December 1999 after 241 landings. 

The coatings showed no signs ofdegradation and were still in pristine condition. 

Figure 7 shows two components from a Navy EA-6B (attack jet) main landing gear piston assembly which 

were coated with HVOF WC/Co to a thickness of 100 micrometers. Note the multiple locations on the long Lshaped piston and also that an internal surface was coated on the collar. It is possible to deposit the coatings with a 

spray angle up to 45 degrees off normal such that some shallow internal surfaces can be coated. It is expected that 

these components will be installed on an operational aircraft sometime in June 2000. 

Production, Lifetime, and Cost Issues 

Several analyses have been made in recent years of the cost of HVOF coatings compared with chromc plating. 

Based on different types of components and different scenarios their results reflect the wide range of situations in 

which chrome is used. For most manufacturers. total production cost, rather than process cost alone. is thc most 

important issue. while for most users, life-cycle cost (or cost of-ownership) is the critical issue. 

For aerospace OEMs the primary cost savings tend to come from elimination of the need to heat treat high 

strength steels to prevent hydrogen embrittlement. This reduces production time with its associated inventory and 

cost-of-money. This makes HVOF especially cost-effcctivc for large items such as landing gear and hydraulics. 

For users, the primary cost savings in extending time between overhauls and reducing the loss of revenucgenerating time to overhaul. At Jacksonville Naval Aviation Depot there have now been several occasions when a 

previously-chromed item has becn coated with HVOF WC-Co, with the result that it has never returned for 

overhaul. The permissible lit: of many aircraft componcnts is often defined by fatigue limits (maximum allowahlc 

flight hours) or by repair limits (maximum number of repairs or total thickness of repair). When the repair coating 

life is 3-5 times that of chrome, it becomes possible to protect the component with a ”lifetime coating’’ that will last 

the entire life of the item, eliminating further strip-down and repair costs. 

Summary 

Currently, there are several ongoing DoDiindustry programs to qualify HVOF thermal spray coatings as a 

chrome replacement on different types of aircraft components. Testing to date has shown that HVOF WCiCo 

coatings generally demonstrate superior performance to hard chrome with regard to fatigue, corrosion, and wear. As 

more and more data is generated and the results are obtained from rig and flight testing, the qualification process 

should accelerate, leading to actual insertion of this technology in manufacturing operations and at military overhaul 

and repair depots. The higher performance of HVOF-coated components should ultimately lead to rcduced 

maintenance, lowering the total-cost-of ownership to DoD for its aircraft. 

References 

1. 

Aer-o.s~ac.e/Airliiie Plating Fnrirni, p. 97- IO5 ( 1998) 

2. Sartwell, Bruce D., and Bretz, Philip E., Adrariued Mum-icrLy arid Pi-ncc~ssc.~, p. 25-29 (August 1999) 

Sartwell, B. D., Natishan, P. M., Legg, K. O., Schell, J. D. and Sauer, J. P., Proceediizgs ?/’the AESF 
Figure 6. Photograph of Navy P3 main landing gear with the piston and axle journals coated with HVOF WCiCo 

c * r 

Figure 7. Photograph of Navy EA-6B main landing gear piston assembly showing the arcas onto which the HVOF 

WCXo coating was applicd and also showing a cross-section micrograph of’thc coating 
The Use of Ion Vapor Deposited (IVD) Aluminum for the Space Shuttle Solid Rocket Booster 

William Imre. Howard Novali, Rand) Raley 

United Space Alliance 

8550 Astronaut Blvd. 

Cape Canaveral. FL 32920 

Introduction 

Deposited (IVD) aluminum coating as a replacement for cadmium plating, and chromated paint primers on both 

Ground Support Equipment (GSE) and Solid Rocket Booster (SRB) non-insulated flight hardware. IVD aluminum 

provides an extremely tenacious, environmentally compatible coating. that lends itself to many items presently 

requiring repainting or hazardous plating removal and greasing of steel parts to prevent subsequent corrosion from 

seawater and seacoast environment. A Technical Directive (TD) was issued by the Marshall Space Flight Center 

(MSFC) SRB Program Office to evaluate the applications of IVD aluminum to SRB hardware. 

USA SRB Element Materials and Processes (M&P) Department had recommended the use of Ion Vapor 

Discussion 

MSFC Corrosion Lab. performed Electrochemical Impedance Spectroscopy (EIS) testing, to confirm the excellent 

corrosion protection properties of IVD aluminum. The authors worked with the Kennedy Space Center - Florida 

Materials Science Division personnel. including Beach Corrosion Test Site. and the Seawater Immersion Facilities. 

The Naval Research Laboratory, located in Key West. Florida. performed unfiltered seawater immersion and 

alternate immersion testing of IVD aluminum coated test plates and SRB test hardware. Florida Atlantic University. 

Marine Engineering Division. located in Boca Raton, Florida. performed beach exposure. alternate immersion 

testing in filtered seawater, and electrochemical testing of IVD aluminum coatings on both steel and aluminum test 

plates and non-flight SRB parts. Much research involved IVD work done by the Air Force, Nay, and Army 

Logistics Centers at various locations within the United States. 

Previous to the work done on this Program, and with test samples provided by the USBI Co. M&P Dept.. 

Process Description 

The IVD process is very similar to conventional plating technology. requiring surface preparation. 

processing and finishing operations in order to correctly process the parts to be coated. Surface preparation consists 

of degreasing to remove gross contaminants prior to an aluminum oxide blast treatment, which provides an anchor 

pattern and residual oxide free surface. Figure 1 shows the overall view of an Ion Vapor Deposition Facility. A 

special air suspension rack (shown at the right side of Figure 1) is used to transport the prepared parts to the IVD 

vacuum chamber; as shown in Figure 2 with the chamber door open and racked parts (test panels) positioned in the 

chamber. After the chamber door is closed, the vessel is evacuated to a pressure of 8X 10-5 Torr to purge the system 

of residual moisture emanating from the parts and internal pressure vessel hardware. The chamber is then back-filled 

with low dew-point pure Argon gas to a chamber pressure of 2x10-2 Torr. At this pressure the parts are subjected to 

a glow discharge cleaning or sputtering operation. A high negative potential is applied between the parts being 

coated and the evaporation source. The Argon gas in the chamber ionizes and creates a glow discharge around the 

parts bombarding them with positive ions. (This ion bombardment of the part surface effects a frnal cleaning 

operation prior to coating). Pure aluminum wire is evaporated in resistance heated crucibles. and known as an 

"evaporator boat system". Aluminum vapors pass through the glow discharge, where it combines with the ionized 

Argon gas and is rapidly transported to the part surface. The IVD process provides a uniform, dense. and adherent 

coating. After the coating operation is complete, parts are removed from the chamber and glass bead peened to 

densify the coating and also to provide a quality check on coating adhesion. An optional conversion coating may 

then be applied to the IVD aluminum surface. 

1 
FIGURE 1. OVERALL VIEW OF AN ION VAPOR DEPOSITION FACILITY 

FIGURE 2. IVD CHAMBER WITH DOOR OPEN AND RACKED PANELS 

2 
Equipment Components 

aluminum evaporation source. and a high voltage power supply as shown in Figure 3. 

The Ivadizer8 consists of a steel vacuum chamber, a gas pumping system, a parts racking device, an 

High Voltage 

Power Supply 

Substrate Holder 

TCa thode 

^^e LWire Feeders 

Evaporator 

Power Supply 

FIGURE 3. SCHEMATIC OF AN ION VAPOR DEPOSITION SYSTEM 

The system utilizes conventional vacuum pumping technology components controlled by a microprocessor based 

control system capable of monitoring stem sequencing. system alarms, process timing, and data recording 

functions. A special Cry0 (cryogenic cooling) Pump is an optional piece of equipment that is used during chamber 

pump down to help condense and freeze moisture rapidly. It significantly reduces pump down time for the oil 

diffusion to obtain high vacuum values of 8x10-5 Torr. As shown in Figure 1, only the fi-ont end of the vacuum 

chamber needs to be placed in a humidity controlled (air conditioned) environment. Parts rack and prepared parts are 

also kept in the air conditioned room to preclude moisture absorption prior to chamber insertion. The rear section of 

the chamber. vacuum pumps, Argon gas supply, and vents can be effectively kept at outside ambient conditions 

thereby significantly reducing air conditioning requirements. Another optional piece of equipment is known as a 

“Barrel Coater”, that allows the coating of hundreds of small parts by utilizing a specially designed tumbling fixture 

that rotates inside the Ivadizer8 vacuum chamber during processing. 

Coating Properties 

IVD aluminum coatings are very uniform and provide excellent area coverage. They are not limited to line-ofsight coverage and can produce a range of thickness’ from approximately 0.0001” - 0.005”+. IVD coatings do 

not build up or leave holidays on sharp edges, regardless of the applied coating thickness. Figure 4 shows a 

typical test panel with excellent uniformity and density of IVD aluminum coating. It is possible to hard-coat 

anodize a portion of the relatively soft, pure aluminum IVD coating, thereby providing a very hard and 

durableinon-conductive surface. By leaving a soft compliant inner layer as shown in Figure 5, fracture 

toughness properties of a high strength aluminum or titanium alloy substrate will not be effected. IVD 

aluminum with supplemental treatment using MIL-C-554 I, Class 3 material, meets the electrical contact 

resistance requirements of MIL-C-8 1706. Testing done on a previous program, allowed for evaluation of IVD 

aluminum coatings on various steel. aluminum and titanium alloy substrates. Salt fog testing per ASTM B 

1 17, along with both beach exposure, seawater immersion and 

3 
alternate immersion testing. showed the outstanding corrosion protection afforded those substrates. NASA-MSFC 

M&P Laboratory evaluated various IVD coatingisubstrate combinations, and reported excellent results in NASA 

TM- 108425. Electrochemical Impedance testing was also performed on uncoated steel alloy test panels and are 

published in NASA TP-2820 and serves as an excellent comparison of corrosion effects between coated and 

uncoated materials. McDonnell Aircraft Company published a 3 Phase Report No. C-87-101602 (2-1 -88 to 8-3 1-93) 

for the Air Force, describing thousands of tests performed with IVD coatings used for corrosion prevention. IT 

Environmental Programs. Inc. published a report CETHA-TS-CR-91054, in April. 1992. for the US Ammy Corps of 

Engineers; concerning the evaluation of IVD aluminum at the Anniston Army Depot in Anniston, Alabama. In 

1996. the USBl Co. Vice President's Office received a Letter of Appreciation from Lockheed Martin Corp.i'Johnson 

Controls on the recommendation of USBl Co. IR&D for using IVD Aluminum on Titan IV platform sheaves on 

the IUS element. Over 800 man-hours of maintenance was saved due to the superior corrosion protection of the IVD 

aluminum coating. 

FIGURE 4. IVD ALUMINUM COATING 

FIGURE 5. IVD ALUMINUMlHARDCOAT ANODIZE COATINGS 

4 
Selection of First SRB Flight Hardware Item for IVD Application 

As a result of conversations between MSFC-SRB Program Management, USA SRB Element Mechanical 

Engineering, Procurement, Program Management, and M&P, it was decided to select the Drogue Ratchet Assembly 

for the first SRB flight hardware item IVD Aluminum coating application. One of the key reasons for selecting the 

Drogue Ratchet Assembly was the difficulty that Procurement encountered in obtaining ne%’ hardware. It was 

therefore necessary to certify the Ratchet Assemblies for multi-flight use. IVD aluminum coating is extremely 

tenacious, affords excellent corrosion protection and it was estimated that because of these excellent properties. will 

allow for multi-flight use of the Ratchet Assemblies before having to re-apply the IVD aluminum coating. Figure 6 

shows the overall configuration of the Drogue/Pilot Parachute Assembly, contained by the Frustum. as part of the 

SRB Forward Assembly. Figure 7 shows a close-up of the Cadmium plated Drogue Ratchet Assembly. 

FIGURE 6. DROGUE/PILOT PARACHUTE ASSEMBL\’ 

5 
FIGURE 7. CADMIUM PLATED DROGUE PARACHUTE RATCHET ASSEMBLY 

Corrosion Testing of IVD Coated Ratchet Assembly 

Corrosion testing of Drogue Ratchet assemblies was performed at the KSC Beach Exposure / Seawater 

Immersion Corrosion sites. Ratchet assemblies were mounted to specially designed racks, facing the ocean, and 

located approximately 100 feet from the high tide line. Environmental effects at the Beach Exposure site are severe. 

and include salt fog and spray, wind driven sand. high ultra-violet exposure, solar heating, condensation of salt 

laden air at night, and SRB exhaust during lift-off of the Space Shuttle. For seawater immersion testing. Ratchet 

assemblies were first tethered, then suspended in a seawater immersion - corrosion test tank. Fresh filtered seawater 

was pumped from the Ocean to flow once through the tank to drain. Tanks were exposed to sunlight, so significant 

algae growth was experienced during the test program. 

Beach Exposure Testing 

It was the intent of this program to photo-document all testing at periodic intervals using a high resolution 

Digital Imaging Camera. Digital images were readily transferred to personal computers and inserted in report format. 

Rack mounted IVD coated Ratchet assemblies and disassembled sub-parts, were tested for over one year at the KSC 

Beach Exposure site. Figure 8 shows a typical Beach Exposure Rack with mounted parts. A general comment on 

Beach Exposure testing is: that all IVD aluminum coated hardware remained in the same rack locations without 

human interference for the extent of the test program. Periodic photo documentation helped the evaluation process. 

IVD coated hardware performed very consistently over the testing period, and assemblies tested did not fail the 

exposure criteria of visible "Red-Rust. Formal testing was completed on December 8, 1999; however. parts were 

allowed to remain on the racks and have not shown signs of failure to date. 

6 
FIGURE 8. IVD COATED RATCHETS MOUNTED TO BEACH EXPOSURE RACK 

Seawater Immersion Testing 

the KSC Seawater Immersion Facility. Because of solar radiation effects, significant algae growth was experienced 

on test parts. Photo documentation showed algae growth before and after wiping down at each inspection interval. 

There were some calcerious deposits on the base of Ratchet assembly parts shielded from the sun, and on those areas 

shielded from the sun, there was virtually no algae growth. Photos document the excellent resistance that IVD 

aluminum coating has to the seawater immersion corrosion environment. No "Red-Rust" was evident on any of the 

test items at the end of the test period, and to date there is no change in the appearance of the IVD aluminum 

coating. Figures 9 and 10 show Ratchet assemblies after 3 months of testing with algae growth and after hand wipe. 

Over three months of seawater immersion-corrosion testing of Drogue Ratchet assemblies was completed at 

7 
FIGURE 9. IVD COATED RATCHET AFTER SEAWATER IMMERSION /ALGAE GROWTH 

FIG 

8 
Conclusions 

As a result of a carefully executed and documented test program at USA SRB Florida Operations, it was 

found that the IVD aluminum coating process has many potential uses on SRB flight hardware and GSE. The 

replacement of toxic coatings such as cadmium plating, and chromate bearing paint primers with the IVD process 

should help mitigate or eliminate hazardous waste streams and human exposure to those materials. IVD is a very 

robust coating and it is visualized that it will be able to fly Multi-Missions before replacement. It is a perfect 

candidate material for Wash-Dry-Fly scenarios. Drogue Ratchet Assembly drawings have been changed to reflect 

the use of the environmentally compatible IVD aluminum coating. Flight hardware items are in process of being 

coated at this time. 

9 
High Temperature Material Performance Testing Using Continuous Wave Carbon 

Dioxide Lasers 

Timothy N. Johnson 

Anteon Corporation 

P. 0. Box 33647 

Wright Patterson AFB, Ohio 45433 

Phone: (937) 252-3132 x3016; Fax: (937) 252-0418 

e-mail1 timothy.johnson2@,ml.wpafb.af.mil I 

ABSTRACT 

A key aspect of material development is the ability to simulate the anticipated real world 

application in a controlled laboratory environment. The use of continuous wave carbon 

dioxide lasers to simulate anticipated heat loads on high temperature materials is an efficient 

and cost effective tool for evaluating the performance of aerospace materials. This paper 

describes the use of lasers to simulate heat loads in the evaluation of aerospace material 

performance. Test methodology and diagnostics are described with representative data 

presented. 

The use of continuous wave lasers as radiant heating sources have many advantages in the 

evaluation of high temperature materials. Thousands of material performance tests have been 

conducted at the Laser Hardened Material Evaluation Laboratory (LHMEL) on many of the 

internal ablative insulation materials used in solid rocket motors. The testing has 

encompassed incident heat flux rates from 25 W/cm' to 5000 Wkm', and a maximum 

measured surface temperature greater than 7000°F. 

Analytical modeling benefits greatly from data gathered during laser material testing by 

correlating the transient response of mathematical material models against the high fidelity 

test data acquired. The lasers at the LHMEL facility can deliver up to 100 kW of power on 

target with a uniform spatial distribution. By providing a flat heat flux profile, simple 

geometric models can be used to ensure the proper physics of material response are being 

modeling. Historical material response data collected for modeling support includes, but is 

not limited to, temperature profiles, density profiles, pressure profiles, surface temperature 

response, and mass loss measurements. Specimens have been tested in environmental 

conditions ranging from a high vacuum (IxlO-' Torr) to high velocity flow (up to Mach 2.2) 

in either oxidizing or inert atmospheres. 

1 
1. Introduction 

The interaction of laser irradiation with materials has been investigated extensively over the 

past three decades. Laser systems ranging in power from milliwatts to multi-kilowatts are 

used in materials processing applications such as welding, cutting and surface modification as 

well as in testing applications to characterize the optical and thermal response of materials. 

Materials processing and materials testing/characterization are two applications that require 

rigid controllability and temporal stability of the amount of laser energy delivered to a 

materials surface. For the former, a high quality beam is required to allow near-diffraction 

limited focal conditions to be achieved and maintained. For the latter, a uniform spatial 

intensity distribution is desired over the surface of the test sample. It is this last category 

that must be achieved in order to use a laser source as a thermal simulation tool for high-heatflux engineering applications. In addition, the thermal conditions created at a sample surface 

by a laser must be matched to conditions indicative of the normal operating environment of 

interest. The Laser Hardened Materials Evaluation Laboratory (LHMEL), located at WrightPatterson Air Force Base, Ohio, is a robust multi-laser test facility capable of producing 

extreme thermal environments in open-air, high velocity flow, and in vacuum. This paper 

describes the laser, environmental simulation, and diagnostics systems available at LHMEL 

for thermal characterization testing. A brief description of thermal response testing 

performed at the facility is included. 

2. Thermal Simulation Using Laser Systems 

For thermal response characterization of a material or system, laser energy delivered to the 

test surface must have high spatial uniformity and temporal stability so that precise, 

repeatable and controllable characteristics are produced at the target. Under ideal 

circumstances for the materials or systems tester, the laser should be nothing more than a well 

characterized and dependable tool. The following sections describe the performance 

capabilities of the carbon dioxide laser devices available at LHMEL. LHMEL lasers are 

thoroughly characterized for testing purposes with output power measurement systems 

calibrated on an annual basis to the National Institute of Standards and Technology (NIST) 

primary standard for laser measurement'. 

2.1. LHMEL Carbon Dioxide Lasers 

The carbon dioxide (C02) laser systems available at the LHMEL facility are capable of 

producing output beams that have temporally stable, radially symmetric intensity 

distributions. Besides high performance reliability, beam spatial uniformity, and 

economically favorable operating characteristics, a between firing turn-around time on the 

order of minutes makes them very attractive for test applications. The laser systems are 

continuous wave C02 eIectric discharge coaxial lasers. Each laser operates at a wavelength of 

10.6pm and produces a multimode output beam having a flat top spatial intensity 

distribution. Figure 1 shows the spatial intensity distribution measured for the output beam 

2 
PEV Profile, Run#95041203. Rotating Reflector Plate, 16 Frame Average 

I 

012345678910 

Horizontal Posdion (cm) at 4 87 cm Vertical 

Figure 1 The spatial intensity distribution of the LHMEL I 

output beam varies no more than 17% from the average intensity 

across the beam diameter. 

produced by the LHMEL I 15kW laser device. The measurement was made using the 

pyroelectric vidicon camera system discussed in section 4.1 of this paper. The maximum and 

minimum values deviate from the average intensity across the beam diameter by only +17%. 

The uniformity of this spatial intensity distribution is ideal for thermal characterization 

testing requirements. 

The LHMEL lasers can maintain power levels on target to within an average variation of 

f596. This stability is maintained over the entire target irradiation time lasting up to 80 

seconds at maximum power. Longer shot durations are achieved when the lasers are operated 

at lower power levels. These reliable and repeatable lasers allow measurements of thermal 

properties to be made consistently, accurately and in a way that is easily modeled and 

analyzed using standard thermodynamics computer codes. 

Testing applications aimed at characterizing the performance of materials and systems in 

high heat environments call for well defined thermal sources. These thermal sources must be 

capable of producing uniform heat loads over areas up to 5cm' for high heat flux applications' 

and up to 300cm2 for applications requiring cooling for high heat load optical components'. 

LHMEL s beam transfer optics can produce beam diameters ranging from 0.6 to lOOcm (0.25 

to 30 inches). Figure 2 shows the maximum laser beam irradiance levels achievable for beam 

diameters ranging from 1 to 100cm. The lines shown correspond to the maximum output 

power delivered to a sample surface by the lasers listed. Each laser can be operated at lower 

powers allowing irradiance conditions anywhere below these maximum levels to be achieved. 

3 
LHMEL Testing Envelope 

1 - - - LHMEL lndustnal Laser (1 2kW) 10 100 

Beam Diameter (cm) LHMEL I (15kW) 

-LHMEL II (135kW) 

Figure 2 LHMEL carbon dioxide lasers can achieve irradiance levels up to the values shown for 

laser beam diameters ranging from 1 to 100 centimeters. 

3. Environmental Simulation 

Many testing applications investigate the response of materials or systems subjected to 

thermal energy input while experiencing specific environmental conditions local to the 

sample. The environmental simulation capability available at LHMEL consists of 1 ) 

environmental chambers allowing specific pressure andor gas composition conditions, 2) 

wind tunnel systems providing specific velocity andor thermal transfer conditions, and, 3) 

dynamic mechanical loading up to 55,000 pounds. 

3.1. Environmental Chambers 

Two environmental chambers are available at the LHMEL facility. The operating 

characteristics of these environmental chambers are summarized in Table 1. These chambers 

are equipped with pumping capability to attain vacuum levels to 1~10-~ torr or can be filled 

with specific gases or gas compositions up to two atmospheres (30 psia). Each chamber is 

equipped with a window allowing laser output to be delivered to a test sample. A 30 inch 

diameter chamber, 40 inches in length, can accommodate a maximum test article dimension of 

4 
20cm (8 inches). The second chamber is 7 feet in diameter by 9 feet in length and can 

accommodate a maximum sample dimension of 120cm (47 inches). 

Table 1 LHMEL environmental chambers 

Chamber Dimensions (diameter x length) 

Routine Vacuum 

Average Pumpdown time 

Minimum Laser Spot Size on Target 

(Diameter) 

Maximum Laser Spot Size on Target 

(Diameter) 

Instrumentation Ports (viewing) 

High Vacuum Signal Feedthrough 

Maximum Number of Pumpdown Sequences 

per Day 

15cm I 1.6cm 

4 (2-3/4in. 0.d.) 7 (2-3/4in. 

3.2. LHMEL wind tunnels 

Wind tunnels are available to provide air or nitrogen gas flow over material test specimens 

during irradiation. The wind tunnels are blow-down systems hven by a regulated 

high-pressure supply that exhausts into a plenum upstream of converging nozzle. The 

LHMEL wind tunnels can be equipped with one of two converging nozzles (5x5cm and 

5xlOcm) each producing subsonic flow ranging from 0.05 to 0.9 Mach. An expansion nozzle 

can also be attached to the 5xkm converging nozzle allowing supersonic conditions up to 

Mach 2.0 to be achieved. Table 2 summarizes the performance capabilities of the wind 

tunnels available at the LHMEL facility. Figure 3 shows a typical test arrangement, in this 

case, using the supersonic nozzle configuration. Test specimens are positioned in the center 

of the characterized flow stream. They are held in place by thermally insulated mounts that 

prevent heat transfer from the test sample into the mount structure. The test sample and 

mounting plate are positioned with upper and lower walls to form a three-wall channel. The 

three-wall channel maximizes flow uniformity across the face of the test sample. A step, 

producing turbulence proportional to size, can be incorporated at the nozzle exit. The laser 

beam is directed to the sample surface through the open section of the three-wall channel. The 

LHMEL I wind tunnel can be rotated in Sdegree increments about the axis of symmetry of 

the exhaust jet if laser irradiance other than normal to the surface is desired. In addition, the 

optical delivery system for both lasers can be adjusted for incidence angles up to 60 degrees. 

Exhaust ducts are provided to remove sample debris and wind tunnel gasses. 

5 
Table 2 LHMEL wind tunnel operating characteristics 

Operating Medium 

Operating Mode 

Test Section Type 

I Parameter I LHMELWindTunnel I 

Air or Nitrogen 

Blow-down, Bottled 

Compressed Gas 

Free Jet, Channel or Flat Plate 

I MachNumber I 0.05 to 2.0 I 

I Nozzle Exit Sizes 1 5x5cm, 5x 1 ~cm I 

I Mass Transfer Coefficient I 0.02 to 0.13lbdft' sec I 

Figure 3 An expansion nozzle attached to a subsonic converging nozzle allows supersonic flow 

up to Mach 2.0 to be achieved. The sample mounting position is located immediately 

downstream of the nozzle. (Dimensions in inches) 

3.3. Mechanical loading 

Two tensile test machines are available to load test specimens concurrent with laser and 

wind tunnel operation. One is a Tinius-Olsen tensile test machine (Model Super L) with a 

maximum loading of 55,0001b. The second machine is an Instron model 4204 test machine 

with a maximum loading of 10,0001b. Both tensile test machines can be used either with 

LHMEL I or LHMEL I1 testing. Various mounting jaws arc available for use with each 

machine to provide a wide range of testing configurations. 

6 
4. Test Diagnostics 

4.1. Surface Temperature 

systems testing. 

temperature measurements. 

Surface temperature is one of the most important parameters to measure during materials or 

Accordingly, the LHMEL uses a variety of methods to make surface 

4.1.1. Thermocouples 

One of the most basic and accurate ways of measuring surface temperature is through the 

use of thermocouples. Thermocouples make direct contact measurements of changes in 

temperature during a test. Type K thermocouples located outside the perimeter of the laser 

irradiated area can accurately measure temperatures up to 1,270"C. Thermocouples can also 

be embedded into the depth of a material or mounted on the back face of a sample. 

Calibration of thermocouples to a reference block is accomplished prior to every test ensuring 

signal continuity and measurement accuracy. 

4.1.2. Pyrometers 

Several non-contact methods of measuring surface temperature are available at LHMEL. A 

variety of pyrometers spanning the range of measurement from 600 to 6,OOO"C are used to 

measure surface temperatures within the irradiated area of the test sample. For absolute 

measurements of surface temperature using pyrometers, sample emissivity must be known. 

An example of this measurement is shown in Figure 4. 

Figure 4: The measured surface temperature response of a carbon cloth composite when 

exposed to a laser irradiance of 5 kilowatts per square centimeter. 

7 
4.1.3. Infrared Imaging Systems 

An infra-red camera system is also available for non-intrusive temperature measurements of 

test articles. The system presents a colored image of the imaged sample area with the 

different colors corresponding to different temperatures. The camera employs a 30-element 

mercury cadmium telluride, thermoelectrically-cooled detector sensitive to infrared radiation 

in the 3.2 to 5.6-m region. It can detect temperature differences in thermal patterns from 

0°C to 600°C with a sensitivity of 0.1"C. The field of view is 20" in the vertical direction 

and 27" in the horizontal direction. Up to 128 video temperature levels can be displayed in 

color or black and white in 525 line/60 Hz format. 

In addition to the infra-red camera, a pyroelectric vidicon camera (PEV), discussed 

previously in section 2.1 of this paper, is used to image the target plane. The pyroelectric 

vidicon camera uses a tri-glyceride-sulfide crystalline matrix, sensitive to infrared radiation in 

the 8 to 12pm region. The thermal sensitivity of the camera is approximately 0.2"C at 100°C 

and is uniform across the PEV crystal to within +6%. The PEV camera has a RS 170 format, 

which can be recorded on a video recorder or interfaced with a frame grabber and associated 

computer software. Up to 16 frames taken at pre-determined time intervals during the laser 

run time can be stored for later processing. The software capabilities for beam profile display 

include 2-D contour plots, line profile plots and 3-D surface plots. Analysis functions 

include the ability to locate the peak intensity, calibrate peak-to-average power ratio, and 

calculate distribution statistics over a defined area of interest. 

4.2. Video and photographic equipment 

The LHMEL facility has a variety of equipment suitable for video recording of 

laser/sample interactions. Black-and-white and color CCD cameras are available for use along 

with video cassette recorders. A variety of lenses are available for use to provide wide angle 

or magnified views. The LHMEL staff relies upon a broad range of experience to produce 

optimum visual records by selecting lenses, exposure settings and gelatin neutral density 

filters appropriate to materials properties and laser irradiance levels. 

Still photographic coverage can also be accommodated by the LHMEL facility. An 

experienced photographer is on staff to advise or take 35-mm pre-test and post-test sample 

photographs. Camera lenses that provide wide angle or highly magnified views are available 

for use. Cameras may also be used to record experimental set-ups including beam trains, 

sample configurations, and diagnostic equipment locations. 

The LHMEL facility has available two Hycam 16-mm cameras (20 to 11,000 frames per 

second) and one Locam I1 16-mm camera (2 to 500 frames per second) along with associated 

optics, lighting, and mounts. IRIG timing pulses can be placed on the edge of the film by one 

of the Hycam cameras. The cameras can accept rolls of film up to 400ft in length. Cameras 

and lighting are actuated automatically in sequence with the laser. 

8 
5. Material Performance Testing 

Recent tests performed at the LHMEL facility have demonstrated that C02 laser radiation 

can be used to evaluate the performance of composite ablative insulation materials at extreme 

temperatures and heating rates. Two primary aerospace applications of composite ablative 

insulation are heat shields for atmospheric reentry velucles, and nozzle liner material used in 

solid rocket motors. To date, materials used for both of these applications have been 

successfully tested at the LHMEL facility. 

The primary heat transfer mechanisms within the dynamic internal environment of an 

active solid rocket nozzle are convection and radiation, as compared with a primarily 

convective environment for heat shields. Comparatively, a laser heats a surface purely by 

radiative transfer of energy. Fortunately, carbon phenolic is an optically opaque material, 

meaning that radiation is absorbed within a few microns at the surface. This also means that 

the thermal response of carbon phenolic will be identical for both radiative and convective 

heating conditions. Therefore, the laser can simulate the equivalent heating conditions 

expected during rocket nozzle firing or a reentry of a heat shield by establishing irradiance 

conditions matching the net heat flux into the material surface and establishing the proper 

environmental conditions to match the rate of surface recession during exposure. 

There are situations when the optimum combination of material surface heating rates and 

environmental boundary conditions cannot be reproduced in the laboratory. In these 

situations, relative material performance evaluations can be conducted by exploiting the 

controlled performance characteristics and the extensive instrumentation capabilities of the 

LHMEL facility. By conducting a short series of experiments with properly instrumented 

specimens, a baseline performance for that material can be obtained. A performance 

comparison can be obtained by repeating these experiments with other candidate materials. 

Although the exact conditions do not directly represent the actual flight condition, the relative 

performance of the materials can be evaluated in conditions representative of the flight 

condition. 

The LHMEL facility is ideal for generating data for use in analytical model development 

and validation. A material test can be instrumented to such detail that a fblly bounded set of 

response data is generated. For example, by measuring the surface temperature response of a 

sample with the use of an optical pyrometer, monitoring the in-depth and back face thermal 

response with imbedded thermocouples, the complete transient thermal profile of the 

specimen is obtained. This type of complete data is invaluable to the analyst, since it 

eliminates many of the uncertainties generally associated with other conventional means of 

obtaining high temperature and high heating rate material performance data. The ability to 

have a clear and unobstructed view of the exposed specimen surface is a great advantage to 

laser material response testing. This ability is usually not available when conducting fullscale flight or sub-scale static tests, or when using other laboratory convective heating 

sources. 

9 
5.1. Material Performance Testing of Solid Rocket Motor Nozzle Liner Materials 

An extensive series of laser experiments has been performed on the carbon cloth phenolic 

used as a nozzle liner ablative insulation for the solid rocket motors used on the Space 

Shuttle. The carbon dioxide lasers and high velocity flow capabilities at LHMEL were 

combined to investigate the response of carbon phenolic test samples'. 

A series of experiments have been developed and conducted to obtain material performance 

data on carbon cloth phenolic as it is exposed to extreme heating rates. Each of these 

experiments was specifically designed to obtain a specific piece of material performance data 

for direct support of analytical material model development. If possible, the experiments 

were designed to measure material performance as the test specimen was being irradiated. 

This type of experiment is commonly referred to as a real time experiment. 

The real time material performance data that has been obtained from these experiments 

includes, but is not limited to; flame surface, in-depth, and back face temperatures, in-depth 

density profiles, specimen weight loss, flame surface erosion rates, decomposition kinetics, 

internal pyrolysis gas pressure distributions, the kinetic energy of pyrolysis gas flow exiting 

the flame surface, the permeability of a forming and cooling char layer, as well as the physical 

swelling of a partially restrained specimen. The data obtained from these experiments, 

combined with existing historical material performance data have given insight into material 

performance issues that have been debated over the past 30 years. Figure 5 shows an 

example of the data generated during a series of tests in which a known incident laser 

intensity was delivered to the sample5. The samples were tested under fully characterized 

compressed air flow (0.5 Mach) conditions for comparison with theoretical predictions in 

order to validate the test method. Each of the data curves displayed in Figure 5 was gathered 

from an individual test specimen. Due to the consistent performance of the laser system, the 

data gathered from discrete tests can be treated as though it were all gathered on a single 

specimen. 

Figure 6 shows an example of the consistency of data produced at the LHMEL facility and 

the repeated accuracy of the test procedures. The ability to treat the gathered data in a 

manner such as this greatly reduced the required complexity of test fixture design and raises 

the confidence associated with each of the gathered data sets. The data collected, along with 

other material performance thermal distribution data collected with LHMEL infrared cameras, 

allowed a more accurate model to be constructed predicting the thermal response for these 

materials. 

10 
Composite Material Performance 

Real Time Data Overlay 

Pressure ~ Tempwature - Density 

0 5 10 15 20 

6000 1 

5500 0 95 

5000 09 

4500 0 85 - 

n 

$ 4000 08 

2 s 4 3000 0' 1 

H 3500 075 

u^ 

2500 065 d 

- im 06 

1500 0 55 

F 

1000 05 

MO 0 45 

0 04 

0 5 10 15 20 

nrne (SK) 

Figure 5: A more complete picture of material performance by overlaying data gathered from 

tests conducted with identical parameters. 

Repeated Thermal Response of Carbon Cloth Composite 

Tasted at the LHMEL Fxlllty 

5030 

490 

4000 

3500 

i 3030 

r 2500 

a E 2000 

1500 

1 030 

500 

0 

0 10 20 30 40 50 60 

Tim (SKI 

Figure 6: An example of the consistency of data generated at the LHMEL facility. Two 

independent temperature response tests conducted with the identical boundary conditions. 

11 
The data produced during this test series represents the first qualitative investigation of the 

overall response of carbon phenolic when exposed to the specific levels of thermal flux 

corresponding to the high heat flux environment found within an operating rocket nozzle. 

The test demonstrated that the use of a laser for the evaluation of rocket nozzle materials 

offers several advantages over alternate testing methods: 1) Lasers can simulate the thermal 

load experienced by rocket nozzle materials and can do so in a diagnostics-friendly 

environment. 2) Rocket nozzle materials can be tested under significant thermal conditions 

without producing the effluents and violent conditions resulting from the operation of a 

rocket nozzle - previously the only method used to evaluate the performance of the materials 

of interest. 3) The reliability and repeatability of the carbon dioxide lasers at the LHMEL 

facility allows a quantitative investigation of the thermal response of rocket nozzle materials 

where previous testing techniques provided limited meaningful data. 4) The resulting data, 

current and future, will allow considerable tightening in the materials tolerances relevant to 

designing solid rocket motor nozzles. 5) The cost of testing these materials at LHMEL is 

substantially lower than any other identified option. 

5.2. Thermal Response Characterization Testing of Heat Shield Materials 

A recent test series was conducted to evaluate the capability of the LHMEL facility to 

obtain high quality data to support the development and enhancement of current analytical 

models to predict the performance of heat shield ablative insulations. Three separate 

experiment test series were conducted to obtain specific material response data for the 

ablative insulation. Data obtained from the testing included surface and in-depth temperature 

response, transient mass loss, transient density profiles, and a measurement of the swell of 

the flame surface as the material is heated. The overall test series was completed with the 

successful gathering of data for each individual measurement. The experiments conducted for 

this series were identical to those conducted over the past three years for the nozzle liner 

material used in the Space Shuttle solid rocket motors. The data gathered from this test series 

is currently being review and processes and therefore is not available for publication in this 

paper. 

6. Conclusion 

The Laser Hardened Materials Evaluation Laboratory has applied a unique combination of 

high energy carbon dioxide lasers, environmental simulation and material response diagnostic 

capabilities to successfully simulate specific thermal conditions required for high heat flux 

testing applications. The highly controllable and repeatable characteristics of these high 

energy laser devices allow specific thermal conditions to be created at the surface of the test 

samples. The accuracy, repeatability and volume of data produced during these tests has 

been significant and has substantiated or corrected calculated predictions of material thermal 

and structural performance of various materials. 

' M. L. Lander, J. 0. Bagford, D. B. Seibert 11, R. J. Hull, High power calibration of commercial power 

meters using an NIST-traceable secondary standard, Jounzal of Laser. Applications 8, 103- 107, ( 1996). 

12 
' J. H. Rosenfeld, R. Schumaker, R. D. Watson, and J. M. McDonald, Porous media heat exchangers for high 

heat flux applications, High Hcat Flux Engineering, Proc. SPIE 1997,53-64 (1993). 

' F. M. Anthony, High heat load optics: an historical overview, Opt. Eiig. 34 (t), 3 13-320 (Feb. 1995). 

' W. T. Laughlin, J. R. Koenig, Laser Analog Test Capabilities, Presented at the 1994 JANNAF Rocket 

Nozzle Technology Subcommittee MeetingSeattle, WA ( 15- I 7 November 1994). 

' T. N. Johnson, Final Test Report for PTP-0390 - Nozzle Material Integrity - High-Rate Decomposition 

Testing of CCP. Thiokol Wasatch Report #75979. (1998). 

13 
THERMOGRAPHIC NONDESTRUCTIVE EVALUATION 

OF THE SPACE SHUTTLE MAIN ENGINE NOZZLE 

James L. Walker 

Nondestructive Evaluation Team 

NASA Marshall Space Flight Center 

james.l.walker@msfc.nasa.gov 

(256) 961-1784 

Matthew D. Lansing 

Nonmetallic Materials Group 

NASA Marshall Space Flight Center 

niatt.lansing(a msfc.nasa.goi 

(256) 544-3953 

Samuel S. Russell 

Nondestructive Evaluation Team 

NASA Marshall Space Flight Center 

sam.russell@ msfc.nasa.gov 

(256) 544-441 1 

Paul Caraccioli 

SSME Project Officc 

NASA Marshall Spacc Flight Center 

paul.caracciolilri msfc.nasa.gov 

(2.56) 544-0064 

ABSTRACT 

The methods and results presented in this summary address the thermographic identification of interstitial leaks in 

the Space Shuttle Main Engine nozzles. A highly sensitive digital infrared camera is used to record the minute 

cooling effects associated with a leak source, such as a crack or pinhole, hidden within the nozzle wall by observing 

the inner “hot wall” surface as the nozzle is pressurized. These images are enhanced by digitally subtracting a 

thennal reference image taken before pressurization, greatly diminishing background noise. Thc method provides a 

iionintrusive way of localizing the tube that is leaking and the exact leak source position to within a very small axial 

distance. Many of the factors that influence the inspectability of the nozzle are addressed; including pressure rate, 

peak pressure, gas type, ambient temperature and surface preparation. 

INTRODUCTION 

The nozzles of the Space Shuttle Main Engines (SSME) consist of over one thousand tapered lnconel coolant tubes 

brazed to a stainless steel structural jacket (Figure I). Liquid hydrogen flows through the tubing under high 

pressure, from the aft to forward end of the nozzle, to maintain a thermal balance between the rocket exhaust and the 

nozzle wall. Three potential problems occur within the SSME nozzle coolant tubes as a result of manufacturing 

anomalies and the highly volatile service environment. These problems include poor or incomplete bonding of the 

tubes to the structural jacket, leaks into the interstices between the tubes and jacket, and leaks into the inner “hot 

wall” or “flame” side of the nozzle. Identification of hot wall leaks can be accomplished with the application of a 

liquid leak chcck solution to the inner surface ofthe nozzle while it is pressurized with helium gas. X-ray 

techniques are utilized for characterizing the condition of the braze line. The identification of interstitial leaks 

between the tubing and structural jacket is not as well defined and has historically been the most problematic. 

If a small leak occurs between the tubing and structural jacket the gas flows down the interstices and vents 

hannlessly out the aft end of the nozzle. As the leak grows though the potential exists for the nozzle to fail by 
pushing il section of tubing into the hot exhaust path which in turn can cause them to rupture. If the rupture is severe 

enough the engine will be starved of hydrogen. and thus become oxygen rich. ‘This at best rcduccs the thrust oftlic 

engine and in the worst case can endanger the launch vehicle. 

Interstitial leaks are often found by first identifying which tubes are leaking by the application ofa liquid leak check 

solution where the interstices vent at the aft end of the nozzle. Thcn, through a trial and error approach, tubes are 

cut open and an angioplasty device inserted to block offa specific region ofthe tube. A boroscopc is then used to 

look at the inside of suspect tubes but leak source identification is difficult due to their typically microscopic size. 

With the suspect tube blocked from the pressure circuit, pressure is reapplied and the interstices leak checked again. 

This process is rcpcatcd until the source is located or all suspect tubes are tcstcd. If the leak is severe enough and it 

cannot be found, then the nozzle must be pulled from service. Identification ofwhich tube is leaking is difficult due 

to manifolding between interstices through braze line voids, resulting in the opening and inspection of many tubes 

that were previously undamaged. Also. when the leak originates from multiple sources it is difficult to tell if the 

angioplasty device has isolated a leaking tube. 

BACKGROUND AND THEOR\’ 

Leaks in pressurized systems can be some ofthe simplest and easiest defects to identify, or they can be extremely 

challenging to locate. A low pressure leak check using a liquid bubble solution applied to the vessel with a brush or 

hottlc is usually adequate if the vessel is geometrically simple and has unrestricted in access. With this method, not 

only can the leak be located. the leak rate can often be determined by observing the bubble formations produced in 

the leak check solution. Frequently though, applications exist where the leak source is inaccessible due to structural 

complexity. In these situations it may be possible to measure the effects ofthe leak on the physical condition ofthe 

structure. For example the leak may produce an audible, or ultrasonic, “hiss”. For practical leak rates the magnitude 

of the “hiss” from the leak source may be very small making it difficult to identify over the interference from 

background noises. Another altcrnative is to record the temperature change associated with the expansion ofa gas 

though the leak source. Here, even if the vessel has a complicated geometry, restricted asscss, chemical sensitivity, 

or a large area, an infrared video camera may be useful for identifying. locating, and characterizing leaks. The 

tcinperaturc change due to il hidden leak may be observed on the outer surface of the structure provided a direct heat 

path is present and the structural material has an appropriate thermal conductivity. Also, infrared \,ideo cameras can 

inspect large areas very rapidly and with out contacting the cornponcnt. 

In real systems, with hidden leaks, the leak geometry is usually unknown and unpredictable making it difficult to 

uniquely define the physical phenomena active at the leak. The leak niay act like a throttle valve, a nozzle. or a 

combination of both. Also, transient effects may be present including the pressurization of the gas already in the 

vessel. causing work on the trapped gas. For the detection of a leak, these effects do not usually need resolution or 

understanding. A local temperature change is simply detected. However, an understanding, or as a substitute 

empirical data, may be needed to locate and approximate leak rate. A discussion of some of these effects, some 

competing. follows. 

The Joule-Thompson effect is classically exhibited in flow through a throttling restriction or valve. The flow 

through the restriction causes no work to be done and is considered adiabatic. For real gasses the temperature can 

either increase or decrease depending on the type of gas, temperature, and pressure. For each given gas there is an 

inversion temperature at which no temperature change occurs for the throttling process. This inversion temperature 

is a weak function of temperature. Below the inversion temperature the gas heats and above the gas cools upon 

throttling. This critical temperature is below standard conditions for hydrogen (202 K) and helium (25 K) and above 

standard conditions for nitrogen (62 1 K). air (603 K), argon (723 K). and CO, (I 500 K). 

A leak may occur in a region that has a flow cross-section that geometrically resembles a converging-diverging 

nozzle. An example ofthis is a cooling tube that has a crack, or small hole, that opens into another confined region. 

For the converging-diverging nozzle and compressible gasses, supersonic flow is possible if the internal pressure of 

the contained gas is (for air) greater than 1.893 times the absolute outside pressure’. Under normal atmospheric 

conditions this is a tank pressure of about 90 kPa ( 13 psig). If the flow at the opening of the pressure vessel is sonic 

then for air the temperature drop may be as low as -29 “C for a tank temperature of 20 “C. If the geometry acts as a 

converging-diverging nozzle the temperature drop away from the leak will be even larger ifthe flow is supersonic 

and will be a major factor in the detected temperature change. 
The Joule-Thompson and compressible gas nozzle effects previously mentioned are usually predicated upon steadystate flow. Thcre may be good reasons not to use a steady state condition during inspection. An examplc ofa 

transient inspection will be presented later. For complex geometries during rapid pressurization, gasses contained in 

confined regions of the vessel may be compressed by the pressure incrcasc. Work is then done on this confined slug 

of gas by the incoming gas. This causes a decrease of volume of tlie slug and a corresponding temperature increase. 

1 

7 

3 

As an illustration of how leaks behave thermally, a series of tests were performed on a single 5.08 mm (0.20 inch) 

diameter tube with a 0.127 mm (0.005 inch) hole. The tube was painted flat black, giving it an emissivity of 

approximately 0.85 and imaged with a high resolution (256 x 256 pixel) high sensitivity (0.025 “C per A/D output 

bit value) infrared camera. The tube was capped on one end and connected to a K-bottle containing the test gas. 

Four gasses in all were tested including nitrogen, argon, helium and carbon dioxide. The pressure regulator on the 

K-bottle was set to deliver 40 psig and was valved to provide that pressure to tlic tube in less than 2 seconds. The 

tube was purged with each test gas prior to pressurization to ensure that the tube contained only that test gas. The 

infrared imager was set to acquire one unpressurized reference image then one frame every 1 /60 of a second for I0 

seconds. 

>2 Foaming 

2 to so Bubbling 

SO to IO0 Strong bubbling that burst and 

re-fonn 

The images shown in Figure 2 demonstrate the thennal behavior ofcach gas as it escapes through the hole in thc 

side of the tube. Two images are given for each gas type, the source peak temperature frame and the end frame. A 

time-tempcrature plot is also given depicting the transient thermal behavior of each gas. By referring to the timetempcrature plot onc can easily see how each gas has its own unique thcnnal response. First, and most obvious, note 

that when the nitrogen, argon and carbon dioxide were used an increase in tetnperaturc occurs when pressure is first 

applied as opposed to when the helium was used which begins to cool immediately. Secondly, notice that the 

nitrogen, argon and helium pressurized tubes all showed some cooling after the pressure had been applied for a long 

period of time, whereas the carbon dioxide pressurized hrbe retunicd to room temperature, 

BUBBLE LEAK CHECK APPLICATION TO THE SSME NOZZLE 

The circumferential location of interstitial leaking can be identified by the application of a liquid leak check solution 

in the openings where tlic interstices vent out the aft end of the nozzle, while the tubes are pressurized. The nozzle 

is pressurized with helium gas to 25 psig and the liquid solution is squirted into the interstitial vent. When the leak 

solution bubbles at the nozzle aft end, the leak is classified as described in Table I, and if it is severe enough actions 

are taken to fix the leak. Due to cross linking of the interstices many interstitial vents may bubble when only one 

tube is actually leaking, making it difficult to not only locate which tube or tubes are leaking but also to determine 

the magnitude of the leak. If the leak is seen to manifold across several tubes it is impossible to tell if all the tubes 

are leaking at the degree seen at the bottom of the nozzle or if the leak is cross-linking from a single source with 

sufficient flow to create all the indications. 

Table 1. Flow rate 

Class I Flow rate I Description 

4 I > 100 I Blowing (Bubbles cant persist) 

scim = Standard cubic inch per niinutc 

Onc method for isolating the defect tube and determining where along its length the leak source is located is to cut 

open the suspect tubes one at a time, insert an angioplasty device to close off a portion of the tube, and then 

repressurizing the system. In theory by using this method the leak can be isolatcd to a givcn tube by moving the 

angioplasty device along the length of the nozzle. Although this method requires no specialized equipment (other 

than the angioplasty device) many inspection induced repairs must be made to cover all the holes cut into the tubes 

for the angioplasty device. Also, due to the additional heating required by the hot wall repair, new cold wall 

“interstitial” leaks may be produced in the process of trying to find one leak. 
Another method is to boroscopc the inside of the tubes and to visually locate the leak. Since the boroscopc can only 

cover a finite tube length and since it is impossible to identify which tube (to the right or left of the identified 

interstitial) is leaking, many extra and undesired repairs must be made to fix just one leak. Also. due to the small 

size of’the fracture required to generate a critical leak, the defect may not be detectable through the boroscope. 

Source Thermal Peak Time = I1 seconds 

21 4 

21 3 

- 21 2 u_ 

5 211 

I g 21 

t 

?O 9 

20 R 

?O - 0 4 6 8 10 12 

TI- (S.cond.) 

Nitrogen 

Time = 2 seconds Time = 1 I seconds 

22 4 

= 212 3 

?I 8 

?I 6 

21 4 

0 ? I 6 8 I0 12 

Time lMCndS, 

Helium 

Figure 2. Thermal behavior of leaks. 

Source Thermal Peak Time = 11 seconds 

225 

22 4 

22 3 

2 b222 

E 22 

.,* 1 

21 9 

?1 8 

21 7 

0 2 4 6 e 10 12 

T,rn(Sacm&) 

Argon 

Source Thermal Peak Time = 1 I seconds 

23 2 

23 1 

- 23 01 

s 229 

g =* 

E 227 

22 6 

22 5 

22 4 

0 4 6 0 10 l? 

Ttme iSecoodsl 

Carbon Dioxide 

THERMOGRAPHIC LEAK CHECK OF THE SSME NOZZLE 
For the work described herein an Amber Radiance 1 camera with 15 mm lens controlled by Thermal Wave Imaging 

software was utilized. Inspections and tests were performed on sections cut from the forward and aft end of a scrap 

nozzle (Figure 3). The aft end section was fitted with a pressure manifold which permitted eight tubes to bc 

pressurized simultaneously. The forward nozzle section, with its existing manifold intact was plumbed so that all 

the tubes were pressurized simultaneously. These sections were initially inspected using both a standard liquid leak 

check at the vented interstices and thermographically and determined to be free of any leaks. Artificial leaks were 

then manufacturcd in each nozzle segment to represent both class II and class III leaks. These artificial defects were 

fabricated by cutting open the tubing on the hot wall side ofthe nozzle, then puncturing the tube into the interstitial 

region and finally resealing the tube hot wall through a typical welding repair operation. During the reweld 

operation the hot wall surface ofthe tubes had to be cleaned with a wire brush which left the surface shiny, greatly 

limiting the thermographic inspection capability. Many methods were investigated to dull the surface of the nozzle, 

increasing the local emissivity to 0.8 or greater. without damaging the fragile nickel coating of the tubes. A water 

washable plat black spray paint was found to work well thermographically, but due to traces of sulfur, was deemed 

not acceptable from a chemical compatibility standpoint. Additional work is ongoing to find a paint that will be 

acceptable thermographically and chemically. 

Aft End Segment Forward End Segment 

Figure 3. Nozzle segments. 

The artificially damaged panels were then thermographically inspected with various flow rates, peak pressure Icvcls, 

ambient temperatures, gas temperatures and with a range of gasses to bound the dctcction capability. The 

pressurization rate was found to have a strong influence on the ability to detect the leak with higher pressurization 

rates yielding the best thermal response for most gasses (Figure 4). When the pressurization rate is too slow the 

thennal signature is lost due to the highly diffusive nature of the tubing material. In general it was found that a 

pressure transient less than 8 seconds (25 psiisec) was required for adequate thermal contrast of the defect to the 

background. The exception to the rule was found for carbon dioxide which was unaffected by pressurization rate 

and could be performed with ramp times in excess of 40 seconds. The only factor limiting the ramp time for carbon 

dioxide being the in-plane conductivity of the nozzle itself. 
0.05 1 

0.03 4 

0.01 / ,, 

2 /’ 3 4 5 6 7 8 

m c 

6 0.02 

n 

0 

Rate (Psikec) 

Figure 4. Thermal response as a function of pressurization rate for nitrogen. 

The maximum pressure was found to have a large effect on thcrmal detectability of the leak. For example, as shown 

in Figure 5 the thermal response, as determined by computing the maximum difference between the IR camera 

values in the defect region and acreage region, increases nearly linearly with increasing pressure. The thermograms 

in Figure h clearly demonstrate the need for higher pressures to bc able to uniquely identify the leak source. In the 

figure, the Class 3 leak appears as a large cool (dark) region just above thc uppcr repair patch. The Class 2 leak is 

not visible at 171 kPa (25 psig) yet is clearly visible above the lower repair patch at 3 IO kPa (45 psig). The limiting 

factor for thc magnitude of the pressure used was controlled by safety related issues. 

Figure 5. Thermal response at three pressures. 

I72 kPa (25 psig) 241 kPa (35 psig) 3 IO kPa (45 psig) 

Figure 6. Thermograms at three pressure levels. 

When the leaks were inspected using different pressurizing gas types it was found that the thermal response not only 

varied with gas type but also with the location of the leak along the nozzle length. For example, when helium was 

used to pressurize the aft nozzle segment no indication was present yet on the forward end of the nozzlc it gave the 

bcst response (Figure 7). 
Tests were also conducted to determine if the blockage associated with a repair could produce a false call for a leak. 

Calculations showed that the largest flow rate expected for a nozzle leak check would be below 12.2 meters/sec (40 

feet per second). Two weld repair restrictions were fabricated by opening the tubing, applying braze to the bottom 

of thc hole and then welding the tubes closed. Nitrogen gas was flowed through the tubes and its velocity measured 

with a hot wire anemometer at a distance of 3. I75 mm ( 1 :8 inch) from the tube opening. The tests dcmonstratcd 

(Figure 8) that the flow rate threshold for thermal detection ofa 50% area restriction is above 12.2 mctersisec. That 

is, below 12.2 nietersisec the signature ofthe restriction is to small for repeatable detection. Based upon thcsc 

findings it is highly unlikely that a restriction alone would create a false positive signature during a thermal 

inspection of the nozzle. 

1, 

0.8 

o^ 

c0.6 

z 0.4 

0.2 

0 

m - U 

Nitogen Argon Helium 

Forward end of Nozzle 

Figure 7. Effect of gas types on thermal leak signature. 

1 I 

0.8 

0.6 

0.4 

0.2 

0 

m - U 

Nitogen Argon Helium 

Aft end of Nozzle 

ao 

60 

$40 

m 

20 

0 

60 

50 

40 $ 

30 2 

10 

rc 

20 gj 

0 

0 0.02 0.04 0.06 0.08 0.1 0.12 

Delta T (C) 

Figure 8. Flow Blockage Analysis. 

APPLICATION POTENTIAL TO A FULL NOZZLE 

The logistics of performing a thermographic inspection on a full nozzle were also investigated. Safety of the 

inspection crew and thc hardware was the primary factor driving the development of the inspection procedures. To 

that end it was desired to limit the amount of time spent by the inspecting personnel inside the nozzle, minimize the 

number of pressure cycles and restrict the movement of the nozzle. 

As shown in Figure 9 the nozzle is positioned vertically on three stands which support it approximately three feet off 

of the shop floor and a small personnel lift is placed under the nozzle cone. An initial liquid leak check is performed 

on the aft end of the nozzle and any leaking interstices identified. A band of tubes extending 20 tubes to either side 

of the leak zone is then marked at the aft end of the nozzle and reference foil markers are temporarily attached to the 

outermost tubes of the suspect region on six inch intervals along the length of the nozzle. A foil number is then 

placed next to every other marker to permit identification of camera position. Regions in the inspection area are 

visually inspected for hot wall leaks and prior repair work. Hot wall leaks are first repaired. Then all repairs are 

sprayed with an flat black paint. 
Thc themiography canicra is mounted to a pan and tilt unit on a tripod and an external focus unit is attached to thc 

cameras lens. Starting at either end. each marked region of the nozzle is then thennographically monitored as the 

pressure inside thc tubing is ramped and then vented. Any leak signature is marked with a foil tape and classified 

based upon its thermal intensity. Once the entire length ofthe nozzle has becn inspected measures arc takcn to 

repair the defective tube and the inspection is repeated. 

Figure 9. Thermal imager inside Nozzle. 

CONCLUSIONS 

The limitations and requirements for thennographic identification of interstitial leaking of the Space Shuttle Main 

Engine Nozzle have been addressed. With a standard themiographic test procedure established for the nozzle it 

should be possible to reliably locate and quantify the nature of interstitial leaking in the SSME nozzle. From these 

results it has been determined that the following conditions must be met to ensure adequate confidence that all 

critical lcvel class II leaks are detected. First, the flow rate of gas into the nozzle must be sufficiently high to permit 

the transient thermal signature ofthe leak to be detected before it is lost to thermal conduction. Rise times to peak 

prcssure less than 8 seconds greatly inhibit defect resolution. Next, the greater the maximum pressure reached 

during the pressurization the better the ability to detect a leak. Although the liquid leak check is perfonned at 25 

psig it was found that for the best thcniial response pressures of'at least 40 psig were required. Carbon dioxide gas 

was found to give the best thermal indications ofa class I1 or greater leak throughout the nozzle. At the forward end 

ot the nozzle Helium was found to also work well, while at the aft end of the nozzle, either Argon or Nitrogen was 

found to work satisfactorily. A gas temperature slightly below ambient was required to get the desired thennal 

gradient and an ambient temperature between 70 OF to 90 OF was required. Optically. it was determined that the 

spatial resolution of the camera system must be able to uniquely identify individual tubes and the infrared imager 

needed to have a thermal resolution of at least 0.025 "CiLevel. Finally, a surface emissivity of 0.8 or greater was 

required to allow measurement of the thermal gradient produced by the leak. 

ACKNOWLEDGMENTS 

The authors are grateful to Melvin Bryant of the NASA Marshall Space Flight Center and Ron Daniel of Boeing 

North .4tnerican/Rocketdyne for their technical support in this investigation. 

REFERENCES 

1, Mechanical Eneineering Reference Manual, Eighth Edition, Michael Lindeburg. 
9. 3 

j f . SCSS~O~I BZ Adv;l/~ce\ ~IJ MXcnak Ariaiysis aikl TPsbiliJ ~~III~IICS / /. - 

Verification of Shearography NDE Methods on Space Shuttle, X-33, and Delta IV Launch 

Vehicles 

JOHN W. NEWMAN 

Laser Technology, Inc. 

105 S. Germantown Pike 

Norristown, PA 19403 USA 

Phone: 6 10-63 1-5043 

Fax: 6 10-63 1-0934 

Laser shearography nondestructive evaluation (NDE) was first implemented in aerospace 

production of the U.S.A.F. B-2 program in the 1980s. Since then, it has become widely accepted for 

the inspection of metal engine components, composites, honeycomb structures, and thermal protection material on launch vehicle systems. Shearography NDE images surface strain caused by the 

presence of subsurface anomalies when a repetitive load is applied to the structure. Very successful, 

high-speed inspection techniques have been developed using shearography with acoustic stress to 

image disbonds under sprayed-on foam insulation (SOFI) applied to aluminum cryogenic fuel tanks. 

Typically, 6 to 8 square feet of surface area are inspected in less than 1 second. 

A large robotic shearography system has been implemented in production for the LO, and 

LH, tanks on the Delta IV using this technology. In addition, shearography methods were vaiidated 

andimplemented on the X-33 XRS-2200 aerospike rocket engine thrust ramps. Both the cooling 

channels and the metal honeycomb support structure were inspected. This provided rapid engineering for production engineering refinement of processes and on-site NDE in near-real time, which 

reduced costs and allowed inspection of braze bonds that otherwise would not have been able to be 

inspected. 

This paper will discuss the technology and quality and cost benefits of shearography NDE as 

applied to rapid launch vehicle NDE and health monitoring. It will also provide specific examples of 

NDE verification on three programs. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampe t. rns fc. nasa . go v 
THERMOGRAPHIC ANALYSIS OF COMPOSITE COBONDS ON THE X-33 

Samuel S. Russell Jaines L. Walker Matthew D. Lansing 

NASA Marshall Space Flight Center 

Nondcstntctive Evaluation Team Nondestructive Evaluation Team Nonmetallic Materials Group 

NASA Marshall Space Flight Center NASA Marshall Space Flight Center 

(256)544-3953 

ABSTRACT 

During the manufacture ofthe X-33 liquid hydrogen (LH,) Tank 2, a total of thirty-six reinforcing caps were 

inspected tlieniiograpliically. The cured reinforcing sheets of graphiteiepoxy were bonded to the tank using a wet 

cobond process with vacuum bagging and low temperature curing. A foam filler matcrial wedge separated the 

reinforcing caps from the outer skin of the tank. Manufacturing difficulties caused by a combination of the size of 

the reinforcing caps and their complex geometry lead to a potential for trapping air in the bond line. An inspection 

process was desired to ensure that the bond line was free ofvoids before it had cured so that measures could be 

taken to rub out the entrapped air or remove the cap and perfonn additional surface matching. 

Infrared therniography was used to perfonn the precure "wet bond" inspection as well as to document the final 

"cured" condition of the caps. The thermal map of the bond line was acquired by heating the cap with either a flash 

lamp or a set of high intensity quartz lamps and then viewing it during cool down. The inspections were performed 

through the vacuum bag and voids were characterized by localized hot spots. In order to ensure that the cap had 

bonded to the tank properly, a post cure "flash heating" thennographic investigation was performed with the vacuum 

bag removed. Any regions that had opened up after the preliminary inspection or that were hidden during the 

bagging operation were marked and tilled by drilling small holes in the cap and injecting resin. This process was 

repeated until all critical sized voids were filled. 

INTRODUCTION 

The X-33 reusable launch vehicle technology demonstrator was designed to store liquid hydrogen fuel in a pair of 

composite fuel tanks, shown in Figure 1. Each multi-lobed tank is an integral part of the vehicle's load bearing 

primary structure. The tanks are attached to the rest of the airframe at points around their forward and aft ends. 

Adjacent to each ofthese attachment points, a cast structural foam tiller and bonded reinforcing cap are used to 

distribute loads to the tank skins. The general locations of these caps are shown in Figure 2, viewing one of the 

tanks from thc aft perspective. The typical cap geometry is evident from the photographs of bonded caps shown in 

Figurc 3. 

Figure 1. X-33 internal structure. Figure 2. Locations ofreinforcing caps on tank. i 
-. 

4 

I‘ 

Figure 3. Photograplis of reinforcing caps at various locations. 

The method of thermographic inspection employed to inspect the bond lines consists of exposing the reinforcing cap 

surface to a rapid heat flux by pulsing a pair of high intensity flash lamps or slowly saturating the surface with heat 

using lower intensity hand-held quartz lamps. After the cap has been heated, an infrared camera is used to record 

the surface temperature as the heat transfers into the structure and the cap begins to cool. A void between the cap 

and underlying foam acts as an insulator. and that region of the cap will retain higher temperatures over the void 

than the surrounding area. Bond line voids arc thus indicated as bright “hot” regions in the thennographic images. 

Thermographic inspections of the wet bond line prior to curing required a novel bagging method. The 

thermographic imager was capable of viewing the temperature of the cap surface through thc bagging and release 

ply material, but could not image through a traditional breather cloth, used to ensure thorough evacuation of the 

vacuum bag. It was also determined that when air was trapped in the bond line it was very difficult to get it to move 

to the edge of the cap so that it could be evacuated. The solution to this problem involved drilling a grid of vent 

holes over the acreage of the cap and placing a scries of split, cut in half along their length, plastic tubes over the cap 

vent holes to facilitate evacuation. This arrangement required that minimal breather cloth only be used around the 

cap edges and over the tubing, allowing the camera to image most of the cap area. The region covered by the tubes, 

however. remained obstructed from view. 

TEST APPARATUS 

A digital thermography system was used to inspect most of the caps during bonding and all of the caps after the 

bonding process was complete and the vacuum bagging materials removed. An Amber Radiance IT infrared 

camera. with a 13 mm lens and a 12’‘ x 12” field of view, was used to image the caps after flash heating. A Thermal 

Wave Imaging EchoThenn data acquisition system was used to record the digital images from the camera to files on 

a PC hard drive. A Thermal Wave Imaging flash hood set to deliver 6.4 kJ of energy was used to rapidly heat the 

caps prior to image acquisition. 

An analog thermography system was also used for some of the cap inspections. The analog system, although lower 

in sensitivity than the digital system gave real-time images of the uncured bond line and as such gave the fabrication 

team more time to work out any trapped air. Here, an Inframetrics SC-1000 infrared camera was used to image the 

caps after slow heating by way of a pair of500W hand-held quartz shop lamps. Thermal images from the camera 

were recorded to VHS tape. 

DEFECT STANDARDS 

Reinforcing Cap Defects 

Inspection of the wet bond line may have also detected defects in the reinforcing caps above the bond line. Defect 

standards were fabricated to simulate defects in the reinforcing caps themselves. Inserts were fabricated into sample 

panels betwecn plies at various depths to simulate internal unbonds. Thc images shown in Figure 4 were acquired 
with thc digital system prc\;iously described, with the exception that a 25 mm lens (6”x6”) ficld ofview was 

employed. In the images the depth of the insert is given as a fraction of the panel thickness (T). Three insert 

diameters were used including 0.50,0.3 and 0. I25 inch. 

I FRONT SIDE BACK SIDE I 

Bond line Defects 

As a method to simulate unbonds during cure a defect panel was fabricated with inserts in the wet bond line. The 

simulated \wid shown thermographically in Figure 5 was produced by inserting a 0.5 inch diameter rubber O-ring 

bctween thc simulated cap and underlying material. The cap was covered with a layer of release ply and vacuum 

bagged. Narrow strips of breather cloth were used in this instance rather than the split plastic breather tubes. The 

part was then inspected by heating the surface with a pair of shop lamps for about 10 seconds. Note how the void 

trapped within the O-ring remains hotter than the surrounding bond line demonstrating the presence of a void. 

Figure 5. Thcrmographic detection of simulated wet bond line void. 
INSPECTION RESULTS 

A. During cure 

As previously described, the initial inspections were performed when the caps were still under the vacuum bag. In 

this manner, voids or air pockets, trapped under the cap could be eliminated before the cure was complete or if thc 

void was less than a previously determined critical size it could be accepted. Figure 6 demonstrates a thermogram 

of a cap section with two small, but acceptable. voids. When the part was cured and the bag removed a second 

inspection was performed (Figure 6b) revealing the first two known defects (B and C) as well as on that was hidden 

(A) beneath the breather ply strip. 

B. Post cure 

On average it took six image sequences to fully cover each cap. The results of thermography inspection of a 

reinforcing cap which did not reveal any unacceptable unbonds are shown in Figure 7. The images shown here were 

obtained after the bond line had cured and the vacuum bag had been removed. Minor temperature variations exist 

due to differences in the thickness of a foam filler material beneath the cap. A grid of hot points is visible where 

vent ports were drilled in the reinforcing cap to prevent the entrapment of air between the foam and the cap. 

The results of thermography inspection of a reinforcing cap which revealed an unacceptable unbond are shown in 

Figure 8. Again, these images were obtained after the vacuum bag had been rcmoved. A branching unbond is 

visible in the upper left sector with a maximum length of approximately 4.4 inches. The unbond was just barely 

visible in the thermograms taken before the vacuum bag was removed being all but totally obscured by breather 

tubes and cloth that was placed around the outer edge of the panel. 

Since this defect was unacceptably large an action was taken to try to fill the void with epoxy. To aid in the repair 

process lead foil tape markers were placed on the cap identifying the exact location of each leg of the void and 

verified by re-inspecting the region. Holes were then drilled in the reinforcing cap over the void and injected with 

epoxy to fill it. Thermograms were taken at various stages in this process are shown in Figure 9. After the third 

injection of epoxy, the size of the void had been diminished sufficiently that it mas deemed acceptable. 

The same process of thermographically inspecting each cap during and after cure was performed for the rest of the 

tank. Defects found after the post cure inspections were measured and if deemed necessary filled with resin. A final 

post repair check was then performed to complete the inspection process. 
Figure 7. Sector inspections of a reinforcing cap with no unacceptable unbonds. 

Figure 8. Sector insDections of a reinforcine cap with an unacceDtable 4.4" long unbond luDDer left). 
Second attempt Post Repair (Third attempt) 

Figure 9. Repair ofa void in the wet bond line by epoxy injection. 

CONCLUSIONS 

Thermographic inspection proved largely successful in the detection of voids in the wet bond line bctwcen 

reinforcing caps and underlying foam filler on the X-33 LH2 Tank 2. Voids that were detected precurc were often 

eliminated by rubbing them out or removing and reshaping the cap. There wm some undetcctcd voids that had 

either opened up after the initial thermographic inspection or were obscured by the breather tubes used in vacuum 

bagging. Epoxy was injected to fill these voids, resulting in an acceptable repair. 

ACKNOWLEDGEMENTS 

The authors would like to acknowledge the Lockheed Martin and Alliant Techsystems composite fabrication crew 

and Don Bryan (NASA MSFC Thennodynamics and Heat Transfer Group) for their assistance in this effort. 
1,. //’ + 7- S?~WJU HI Dcwiopiriciiti /!I Mrmii F’m (ai\( i i i /’ 

Evaluation of Forces on the Welding Probe of the Automated Retractable Pin-Tool (RPT) 

R. JEFFREY DING 

Marshall Space Flight Center/ED33 

Huntsville, AL 358 12 USA 

Phone: 256-544-2700 

Fax: 256-544- 1660 

jeff,din&msfc.nasa.gov I 

The NASA invention entitled “The Hydraulic Controlled Auto-Adjustable Pin Tool for 

Friction Stir Welding” (U.S. Patent 5,893,507), better known as the Retractable Pin-Tool (RPT), has 

been instrumented with a load-detecting device allowing the forces placed on the welding probe to 

be measured. As the welding probe is plunged into the material, the forces placed on the probe can 

now be characterized. Of particular interest are those forces experienced as the welding probe comes 

within close proximity to the back-up anvil. For a given material, it is believed that unique forces are 

generated relative to the distance between the welding probe and the anvil. The forces have been 

measured and characterized for several materials, and correlations have been made between these 

forces and the pin’s position relative to the backside of the weld material. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. rnsfc. nasa.gov 
FRICTION STIR WELDING AT MSFC: KINEMATICS 

Arthur C. Nunes, Jr. 

Marshall Space Flight Center 

ED33. Huntsville. AL 358 12 

artliur.nunes(tqinsfk.nasa.gov 

(256) 544-2699 

Introduction. In 1991 The Welding Institute ofthe United Kingdom patented the Friction Stir Welding (FSW) 

process (Thomas PI NI.). In FSW a rotating pin-tool is inserted into a weld seam and literally stirs the faying surfaces 

together as it moves up the seam. By April 2000 the American Welding Society International Welding and 

Fabricating Exposition featured several exhibits of commercial FSW processes and the 8 1 st Annual Convention 

devoted a technical session to the process. 

The FSU' process is of. interest to Marshall Space Flight Center (MSFC) as a means of avoiding hotcracking problems presented by the 2 195 aluminum-lithium alloy, which is the primary constituent of the 

Lightweight Space Shuttle External Tank. The process has been under development at MSFC for External Tank 

applications since the early 1990's. 

Early development of the FSW process proceeded by cut-and-try empirical methods. A substantial and 

complex body of data resulted. A theoretical model was wanted to deal with the complexity and reduce thc data to 

concepts serviceable for process diagnostics, optimization, parameter selection etc. 

A tkst step in understanding the FSW process is to determine the kinematics, i.e. the flow field, in the 

metal in the vicinity of the pin-tool. Given the kinematics, the dynamics, i.c. the forces, can be targeted. Given a 

completed model of the FSW process, attempts at rational design of tools and selection of process parameters can be 

made. 

The dynamic anomaly. The attempts to model the FSW process at MSFC began with a cylindrical rotating flow 

matching the surface speed of the rotating pin-tool at the pin surface and extending out to some radius at which the 

flow stops. The heat generated would leak out radially into the workpiece, and the mechanical work would balance 

the heat loss. At steady state the moments on a ring element cut out of the swirl would balance to zero. A simple 

systcm of equations could be written to model the distribution of angular velocity throughout the deformation zone. 

The stress on the outside of a ring element has the advantage over that on the inner surface. The area is 

bigger; the moment arm is longer. For equilibrium, then, the flow stress has to decrease with increasing radius. For 

metals the flow stress is not greatly affected by shearing rate, but mainly by temperature. Hence, the temperature 

must increase with radius. The heat generated from the plastic flow has to flow backwards down the temperature 

gradient into the tool! But what if the tool were insulated? With an insulated tool, backflow of heat and the required 

temperature rise with radius could not occur. This consequence of the plasticity of the workpiece seemed peculiar. It 

was dubbed a "dynamic anomaly." It led to a reevaluation of assumptions. There are several ways to alter the 

original assumptions to circumvent the "dynamic anomaly". 

Alteration of the constitutive equation of the metal to make the metal viscous would reduce stresses at 

greater radii by reducing the strain rate so as to make it unnecessary for the temperature to drop. This approach was 

rejected because no good justification for attributing viscous behavior to a metal could be found. See Appendix 2. 

Withdrawal of the assumption of steady-state flow in favor of an oscillatory flow might allow a plausible 

solution. Stick-slip flow is well known in friction situations. This approach was rejected because oscillations were 

not observed in FSW flow. 

Withdrawal of the assumption of a radially distributed shear in favor of a slip discontinuity. a slip envelope, 

would also allow a plausible solution. Slip discontinuities arc characteristic of plastic flows. This approach was 

adopted. 
The rotating plug model. The rotating plug model superposes two flows: (1) rapid shear over an approximately 

discontinuous cylindrical boundary separating a plug of mctal rotating with the tool from the stationary workpiecc 

mctal. and (2) a relatively slow rotating motion driven by the threads on the tool and wrapped around the tool in ;I 

ring 1-ortcs configuration. See Figure I. 

Figure I. The rotating plug model comprises: (I) a rapidly rotating plug of metal attached to the pin-tool and 

slipping with respect to the workpiece on a cylindrical surface surrounding the pin-tool, and (2) a relatively slow 

circulation driven by the threads surrounding the pin as a vortex ring. 

As the tool moves it is necessary for metal to pass from the front to the back of the tool. One way for this to 

occur is by a wiping motion. A wiping motion can be modeled by superposing a rotating disc velocity field 

upon the velocity field ofa uniform displacement 

- v =-vi 

- 

It is noted in passing that if volume is conserved (v*v = 0) in each of the fields, it is conserved in their 

superposition. The velocities ofthe superposition field on the disc are 
dx 

dt 

- = -(ya + v) 

and 

dY -=xR 

dt 

The trajectory on the disc is computed by equating expressions for dt in the above equations 

xdx +( y + g)d( y + :) = 0 

x2 +(y+:)2 =Constant 

-- 

The resultant trajectories are circles displaced towards the forward moving side of the rotating disc (or the vxa 

v 

direction). The resultant flow field is shown in Figure 2. For FSW nonnally - << r, whcrc r is the radius of the 

R 

rotating plug. Hence the metal flow takes place in a thin laycr on the surface of t1ic rotating plug. Figure 3 greatly 

exaggerates the width of the wiping deformation laycr just under the surfacc of thc rotating plug. 

Figure 2. Wiping flow is modeled by superposing a rotating disc on a uniform translation. Trajectories on the disc 

V 

L2 

are circles with radius displaced by - towards the advancing side of the disc. When ra >> v. as is generally the 

V 

R 

case for FSW, flow about the central plug takes place in a thin layer ranging from zero to 2 - in thickness. Note 

that in this model inetal exits the disc at the same position that it enters. 
Because it is easy to visualize this model using people walking across a merry-go-round. it is soinetimes 

rcfkrrcd to as the "mcrry-go-round" model. Imagine a person walking towards and stepping onto a merry-go-round. 

If' the person continues to \valk in the same direction (not an easy feat on a real merry-go-round), he moves into the 

rotating disc until he passes the disc center. then he nioves out to the edge again in a symmetric trajectory. Because 

of the symmetry. he gets off at the same distance from the centerline as he gets on. That is. the rotation does not shift 

his ultimate y-position. 

Tracer Experiments. Traecr experiments (See Figure 3) have been carried out at the University of South Carolina 

(Reynold\ ('1 ([I) where a FS weld is passed through a band of tracer metal of different, distinguishable composition 

Figure 3. FSW tracer experiments. 

A trailing parabolic loop of tracer metal is left behind the tool. The observed dimensions of the loop seem to agree 

with the rotating plug concept in that the particles appear to be displaced back from the original band by 

approximately the chord of the plug circle. Further, there is a forward pointing spur of tracer ahead of the original 

band on the forward moving side of the plug as if material being carried around the plug surface dropped off before 
completing the circuit around the plug. The premature exiting of material from the rotating plug can be attributed to 

the secondary vortex flow. 

Steel shot tracer experiments carried out at Boeing Company's Seattle, Washington. plant (Colligan) reveal 

a coinplex behavior that can be interpreted in terms of( I) the basic wiping flow characterized in Figure 2, (2) the 

variation in plug diameter with depth. and (3) a shifting ofmaterial with respect to the plug by the secondary flow. 

For example, shot entrained by the rotating plug is not left behind at the same distance from the centerline 

as it entered. This is because the vortex circulation shifts the shot into an axial site where the plug radius is different. 

If the plug radius variation is large with respect to axial displacement along the pin close to the tool shoulder, the 

lateral displacement of the shot becomes more sensitive to slight variations in axial displacement. This is taken to be 

the reason why the shot patterns exhibit a great deal of scatter in the proximity of the tool shoulder. 

At Marshall Space Flight Center the effect ofthe FSW tool on wire tracers (Bemstcin c'/ crl.) was found to 

support the concept of the rotating plug model. Copper wires were inserted into holes drilled perpcndicular to the 

weld interface at different plate depth levels. The wires on the forward moving side of the pin-tool were bent 

forward and broken. The wires on the retreating side of the pin-tool were swept backwards into a trailing curve. The 

shapes of thc trailing curves were computed for different distributions of angular velocity around the pin-tool. The 

computations that agreed best with the observations were those for the sharpest drop-off' of tlie angular velocity, i.e. 

the computations closest to the sharp discontinuity of the rotating plug model. 

Strain Rates. The idealized wiping model presented here does not yield a strain rate. Each stream of metal 

approaching the rotating plug at a different lateral position receives its own instantaneous shear increment as it 

crosses the shear interface. The sheared metal has a certain time at tlie temperature of the shear zone for recovery. 

Then the metal receives a second shear increment as it exits from the rotating plug. 

It is possible to estimate a representative shear rate, however. The metal flows into the plug ofradius r over 

a path of width 2r. By the time it has been swept to the side of the plug, - , the stream of metal is narrowed to 

7T 

2R 

V rR 

R V 

2 - for a tensile strain of -. The strain rate & is approximately 

If r = 0.22 inches, V = 5.25 inchesiminutc. and R = 2n( 350 RPM), then the resulting strain rate is 2 I50 see-'. This is 

high, in the range of metal cutting strain rates. 

This strain rate estimate. more of a lower bound, perhaps, than a mean, is of interest in that it appears to 

have a potential for estimating the microstructure of a FS weld. 

One approach is to approximate the link between mechanical strain and resulting microstructure by a 

dynamic recovery process. These softening processes all involve "single dislocations, which are annihilated in 

individual events" (McQueen and Jonas p. 438). A correlation has been published (McQueen and Jonas p. 409) 

between the subgrain diameter d of commercial purity aluminum and the Zener-Holloman parameter (Zener and 

Holloman). z &e see.', where & is the applied strain rate, R, the Gas Constant, and T the absolute 

temperature during deformation: 

- 

17.300 

1 

0.08 log Z - 0.6 

d= 
The approximate corrclation holds for z’s Icss than IO”. The highest strain rate listed in the experimental data is 

’I9 sec :. 

An attempt (Frigaard cv til) was made to use this relation to work backwards from measured subgrain 

diameters and estimate the strain rates in FS welds in AA6082 and AA7 I08 aluminum extrusions (conforming to 

6082-TO and 7108-T79 alloys). Rates obtained in this way were extremely low, 1 to 20 sec-’. Frigaard L‘/ a1 attribute 

the discrepancy between their low strain rate estimates and the much higher strain rates expected from the nature of 

the mechanical process to melting “a liquid film at the toolimatrix interface”. 

An explanation morc in consonance with the concept of the FSW process expressed herein would be that at 

the high strain rates dynamic recrystallization. “where dislocations are annihilated in large numbers through thc 

migration of a high angle boundary“ (McQueen and Jonas p.438). accounts for much of the structural transformation 

during mechanical deformation. 

In any case a means for linking the mechanically estimated strains with the FSW microstructure does not 

exist at present. The understanding of the transformations that annihilate dislocations at high strain rates is not 

adequate. 

Conclusions. The rotating plug model of the FSW process explains complex-seeming results of tracer experiments 

\vel1 and simply. It is thought to be fairly well substantiated. 

The model pcnnits a rudimentary estimate of the FSW strain rate. An estimation of the FSW microstructure 

from the strain rate, however. awaits a better understanding of recovery and recrystallization dynamics at high strain 

rates. 

Even in its present state of development, the model is a potentially useful tool in fault diagnostics, and a 

correct kinematics is a prerequisite for constructing a dynamics (Nunes e/ al) ofthe FSW process. 

References. 

Rackofen, Walter A. 1072. Dcforrnation Processing. Addison-Wesley Publishing Company: Reading, MA. 

Rernstein, E.L. and Nunes, A.C., Jr. 2000. The Plastic Flow Field in the Vicinity ofthe Pin-Tool during Friction Stir 

Colligan, K. 1999. Material Flow Behavior during Friction Stir Welding of Aluminum. u.b/ding Jourrru/ 78( 7): 

C‘randall, Steven H. 1956. Ei~giizt~~ring ,4/iu/i:sis: A Sitnx<i~ u,”nimn.icd procwhrr.~. McGraw-Hill Book Company. 

Frigaard, 63.. Grong, D., H.jelen, J., Dulbrandsen-Dahl, S. and Midling, O.T. 1999. Characterization of’the subgrain 

Welding. Under review by Weldirzg .JoiirriuI. 

2395 to 2375. 

Inc.: New York. 

structure in friction stir welded aluminium alloys using the SEM-ERSD technique. Is: IriiCi.iiN:i(~izNI 

S\viposizinz oii Friciiorz Stir M’elding, Rockwell Science Center, Thousand Oaks, CA. June 14-1 6. 

Hill. R. I Y50. The Maflieniufical Thee)?, qj’Plasticip. Oxford at the Clarendon Press: New York. 

McQueen. H.J. and Jonas. J.J. 1975. Recovery and Recrystallization during High Temperature Deformation. 

Treatise 011 Malerials Science arid Technolog\: Volunze 6: Plastic Deformation of‘ Meiu1.s. R.J. Arsenault, 

Ed. Academic Press: New York. 393-493. 

AWS Annual Convention. Chicago, IL, April 25-28. 

Friction Stir Weld. /sr Oirermtionul Siwiposiuni 011 Frirtinti Stir Welding, Rockwell Science 

Center, Thousand Oaks, CA. June 14- 16. 

NLI~KS, A.C., Jr., Bernstein, E.L. and McClure. J.C. 2000. A Rotating Plug Model for Friction Stir Welding. 81st 

Reynolds, A.P., Seidel, T.U., and Simonsen, M. 1999. Visualization of Material Flow in an Autogenous 

Thomas. W.M., et (11.. Dec. 1991. Friction Stir Welding. U.S. Patent 5,460,317. 

Zcner. C. and Hollornan, J.H. 1944. Effect of Strain Rate Upon Plastic Flow of Steel. Joirrrzal of’Applied Phj:sic.s. 

15% January.22-32. 
APPENDIX 1 

Komenclature 

- 

t 

V 

V 

X 

Y 

Subgrain diameter 

Unit vectors in x- and y-directions 

respectively 

Time 

Translational velocity of pin-tool 

Weld speed 

Distance from center of rotating 

pin in direction of mo\~emcnt 

Distance from center of rotating 

pin perpendicular to linear 

movement in direction of retreating 

side of pin 

& Strain rate 

- 

Angular velocity of pin 

of pin 

R Magnitude of angular velocity 

APPENDIX 2 

Viscous theories of the FSM' flow field. It is tempting to try to construct a viscous model ofthe FSW flow field. A 

viscous flow tield will be continuous and distributed as initially expected. But the assumption of viscosity requires 

physical justification. As the apparent operating temperatures are substantially below the alloy solidus temperature. 

justification of the assumption of viscosity presented greater difficulties than abandonment of the cxpcctation of a 

continuous, distributed FSW flow field. 

Metals have flow characteristics unlike those of gases or liquids. When a layer of gas is sheared, gas 

molecules with speeds matched to the moving boundaries by collisions with the boundaries transfer momentum by 

intermolecular collisions through the layers of gas between the boundaries. The momentum transfer results in a 

viscous shear force on the boundaries. A rise in temperature promotes more momentum transfer so that the viscosity 

of gases goes up with increasing temperature. 

When a layer of liquid is sheared random local structural rearrangements ease the shear forcc transmitted 

by the elastic character of thc liquid. In doing so they determine the level of stress across the liquid layer. These 

local structural rearrangements come into play at the lowest of stress levels and in whatever direction the stress is 

acting. Thus liquids exhibit \iscous behavior. The viscosity of liquids, unlike that of gases, goes down with 

increasing temperature, however, because thermal energy aids local structural rearrangements of liquids. 

When a layer of metal is sheared. the metal at tirst deforms elastically. Only after a sufficiently high stress 

is imposed do the internal dislocation sources begin to cmit so that plastic flow occurs. If structural changes leading 

to work hardening are ignored, the flow stress of a metal remains constant. Metals are not viscous. They are plastic. 

That is, the stress is whatever is applied up to the flow stress, but a stress higher than the flow stress cannot be 

applied; the metal merely flows at this point. 

Because the flow stress of metals is only weakly dependent upon strain rate, the metallic stress-strain curve 

is more or less independent of strain rate, which is not at all the case for viscous materials. A simple dislocation 

mechanism of metallic flow yields a dependence of flow stress on the logarithm of thc strain rate. Although metals 

arc not viscous, the dislocation emission process is thermally activated so that the flow stress of metals depends 

strongly upon temperature. 

This is why plasticity theory (Hill, Backofen), which amounts to the solution of a hyperbolic system of 

equations (Crandall), where characteristic lines exist along which there can be discontinuities. is so different from a 

(incompressible) viscous flow theory, which employs parabolic or elliptical systems of equations. 
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Fabrication of Composite Combustion Chamber/Nozzle For Fastrac Engine 

T. Lawrence 

Marshall Space Flight Center 

hlailstop: ED34 

Huntsville, AL 35812 

Ernail: 1 tirn.lawrenceb!msfc.nasa.pov I 

R. Beshears, S. Burlingame, W. Peters, M. Prince, hl. Suits, S. Tillery, Marshall Space Flight Center 

L. Burns, ill. Kovach, K. Roberts, Thiokol Propulsion Group 

Abstract 

The Fastrac Engine developed by the Marshall Space Flight Center for the X-34 vehicle began as a 

low cost engine development program for a small booster system. One of the key components to reducing 

the engine cost was the development of an inexpensive combustion chamberhozzle. Fabrication of. a 

regeneratively cooled thrust chamber and nozzle was considered too expensive and time consuming. In 

looking for an alternate design concept, the Space Shuttle’s Reusable Solid Rocket Motor Project provided 

an extensive background with ablative composite materials in a combustion environment. An integral 

combustion chamberinozzle was designed and fabricated with a silica/phenolic ablative liner and a 

carbon/epoxy structural overwrap. This paper describes the fabrication process and developmental hurdles 

overcome for the Fastrac engine one-piece composite combustion chamber/nozzle. 

Introduction 

The Fastrac 60,000 pound thrust engine (60K) combustion chamberinozzle, referred to henceforth 

as the nozzle, began as part of a low cost technology demonstration ef-fort. Development began at the IS 

thousand pound thrust (1 5K) size with material performance testing and was scaled up to the 40 thousand 

pound thrust (40K) “flight” type demonstration size. The final 60K design has the same inner contour as 

the 40K with changes driven by process development and X-34 flight requirements. The technology efforts 

were combined into a low cost engine design under NASA’s Low Cost Booster Technology project to 

demonstrate that a robust, low cost engine was an attainable goal. 

As part of the Low Cost Booster Technology project, the engine was designed for use in an 

expendable booster. This significantly impacted the material selection and engine packaging. A composite 

liner and structural overwrap with bonded metal attach hardware were selected for development. In 

comparison to a regeneratively cooled thrust chamber assembly, composites were an order of magnitude 

cheaper and could be produced in less than one-sixth the time. With a composite design the combustion 

chamber and nozzle could be fabricated in a single unit, removing the complexity and weight ofa joint 

design. The composite design also reduced the complexity of the engine since no fuel would be pumped 

through the component walls for cooling. 

Siltca/phenolic was selected as the ablative liner material and carbordepoxy was selected as the 

structural overwrap. The silica/phenolic material selection was made based on knowledge and experience 

gained from the Space Shuttle’s Reuseable Solid Rocket Motor (RSRM) and the Solid Propulsion Integrity 

Program. The composite processing knowledge and automated processing capabilities at the Marshall 

Space Flight Center (MSFC) provided the foundation to combine the materials into a single unit and to 

achieve the goal oflou cost. 

When the engine was switched from the expendable booster to the reusable X-34 the biggest 

problem was the packaging. Nozzle changeout was not considered a critical issue with the expendable 

dcsign so easy changeout was not incorporated. The turbopump, gas generator, and thrust vector 

attachment were all packaged to attach to the nozzle. Had the original purpose been a reusable design all of 

these would have been packaged on the powerhead so thc nozzle could be easily replaced. 
The remainder of the paper will describe processing of the liner, overwrap, and bonding. Included 

will be the lcssons learned in each section. The majority of the lessons learned came after the failure of 

60K-0 I. which will be described in greater detail in the liner processing section. Nothing can replace 

learning by doing and this project, having been worked from initial concept to hot fire testing, has provided 

a tremendous Icaming opportunity tor all those involved. 

The Liner Process 

The purpose of the liner is to form the flame side contour and to protect the structural overwrap 

and bondlines from excessive temperaturcs. For the 60K engine to meet its performance goal, erosion had 

to be almost zero. To minimize erosion, a small percentage of fuel is sprayed down the chamber wall to 

provide a layer of film coolant. The film coolant also helps to prevent hot spots and streaking in the 

chamber. Testing to date has shown no measurable erosion with an accumulated test time ofup to 341 

seconds. Flight requirements call for the engine to fire for 159 seconds. 

Liner processing is the first step in fabrication of the Fastrac nozzle. Silicdphenolic bias tape, 

FMSiOl, is tapewrapped onto a steel mandrel using a horizontal tapewrap machine. The ply angle, the 

angle of the tape to the flame surface of the liner, directly affects erosion performance and stress levels of 

the part. Based on thermal-structural analysis, this ply anglc had to be changed twice. once in the throat 

and once just aft of the throat (see Figures 1 & 3). This was accomplished by tapewrapping past the ply 

angle change and then machining a new ramp anglc in the uncured silica/phenolic. Computed tomography 

X-ray (CT) of the ovenvrappcd part and posttest sectioning demonstrate a well-consolidated part at the ply 

angle change. 

60K 

Tape Wrap 

30 to 1 
Once the tapewrapping is complete the part is vacuum bagged and cured in an autoclave. Bccausc 

of the complex shapo of the nozzle and the sensitivity ofsilica/phenolic to cracking during cure. 

development of an appropriate cure cycle was critical. The cure cycle was established using data generated 

from instrumented panels of similar thickness and the cure model developed by the RSRM project. 

Figrrrx, 3. Cured 

Si-P Iirier hillct 

After liner cure the forward tag end is machined and the liner is removed from the mandrel. The 

liner is returned to the machine shop to have the outer diameter contoured in preparation for the overwrap 

process. The machined surfaces are inspected for wet line indications by alcohol wipe and then sent to the 

overwrap step. 

Lessons Learned 

As a result of lessons learned, several minor changes were made to the fabrication process and one 

significant changc was made to the silicaphenolic tape to improve the quality of the liner. Onc minor 

change involved modification of the machining process used to cut the new ply angles in the uncured 

silica/phenolic. The first ply angle ramps were machined roughly and produced resin pockets visible in the 

post-cured computed tomography images. Once the ply angle ramp machining was improved to provide a 

smoother ramp, the resin pockets were essentially eliminated. Another process change was made because 

the 60K-03 and 04 nozzles had very poor consolidation and flow in the throat region. This problem in the 

throat developed because the O-ring in the throat centerline joint of the mandrel was improperly sized and 

leaking. Rather than reworking the mandrel, the planning was changed so that the joint was filled with 
room tcmpcraturc \ulcanized silicone rubber (RTV) during mandrel assembly. The problem has not 

recurred. 

During the investigation of the problem with the mandrel leakage it was determined that the part 

was too large tor only an aft tag end. Thc mandrel was modified to increase the chamber length 

sufficiently for a forward tag end. The forward tag end is removed after liner cure and prior to the 

overwrap process. The data from thc tag ends is charted and evaluated for any trends indicating a shift in 

the process or in the properties of thc liner or overwrap materials. 

Early in the nozzle development process, most of the cured components had dry regions because 

thc material was overstaged during tapewrap. There were regions where the plies were rolled over on the 

inside surface because of significant tape to mandrel gaps. The operators performing the tapewrapping 

were asked to look at the cured componcnt and once they saw how the final part looked and how their work 

could affect the part, significant improvement was made in the part quality. 

The last minor change to be discussed involved the silicaiphenolic specification for resin flow. 

One lot ofmaterial received had a resin flow that was on the low end ofthe specification. This material 

produced an acceptable part but was much harder to tapewrap and the resin did not flow as well during 

curc. The cured part resin content exceeded the upper specification limit and additional testing had to be 

pcrfoniicd. To keep the cured part within resin content specifications, the lower flow hiit tor the 

silica!phcnolic was raised on subsequent material orders. 

The most significant change to the liner began with the failure of nozzle 60K-01 during ignition 

on its third hot fire test. Prior to the third test. scheduled to be 120 seconds, 60K-01 had undergone a 20- 

second and I2 second test. Although the nozzle was designed for a single use, testing during the 40K test 

series had demonstrated that multiple short duration tests could be run on a nozzle without jeopardizing its 

suwivability. At ignition the liner failed approximately 2 inches aft of the throat region. Since the 

pcrfonnancc of the combustion chamber was not affected, the test was continued for 59 seconds to gain 

needed injector pcrformancc data. The exposed structural overwrap burned, destroying data that would 

have been useful to the failure investigation team. Review of the high-speed video and reassembled liner 

pieces showed the exit cone portion of the nozzle was ejected as a single piece at ignition. The liner broke 

into pieces as it struck thc ground and was then tumbled across the test pad by the engine exhaust plume. 

The cause of the failure was determined to be a delamination that extended through the entire 

thickness ot'the liner, combined with a poor liner to overwrap bondline from the delamination point aft. 

Posttest CT found an axial crack in the liner which ran through the chamber and throat and ended at the 

delamination in the exit cone (see Figure 4). With the liner continuity broken there was nothing holding it 

in place. Thc poor bondline was caused by the inadvertent omission ofa dry cycle, which is discussed in 

the ovenvrap section. 

The primary cause of the liner failure turned out to be a supposedly transparent material change in 

the silicaiphenolic. For the 40K program FM5504 silicaiphenolic was used. Between the time that the 40K 

material was purchased and the time the material was purchased for the 60K program, Fiberite bought the 

producer ofFM5504 and decided to phase it out and manufacture only their version of the same product, 

MX2600. Since both materials had been qualified for use on the RSRM and met the same specification, it 

was believed they would behave in a similar manner. The material change was made with no preliminary 

testing; a test matrix was to be performed concurrently with the fabrication and hot fire testing of the 6OK 

components. 

To evaluate the material differences, cylinders with a diameter the size of the 60K throat were 

made ofthe two materials and hoop tensile tests run at Southern Research Institute. The results, shown in 

Figure 5, clearly show the problem with the MX 2600. With reduced strain capability the MX 2600 could 

not survive the stresses put into the liner during overwrap cure. This was demonstrated when several liners 

made with MX 2600 and possessing good bondlines cracked axially in the chamber and throat down 

through the nozzle until they were stopped by a 360 degree liner delamination. With this information 

Fiherite agreed to supply the FM5504 and no problems have been encountered with the liners cracking. 
Forward end 

i 

silic 7- 

liner liner 

r 

I 

?. 

overwrap 

iozzle 

:hroat 

epoxy 

FigirrcJ 4. CT lnrage 01 Axial Crack iri 60K-01 C'lraniher arid Tiir.ori/ 

The old FM 5504 data listed on the plot is material from the 40K devclopmcnt series (old) made at 

the original manufacturer's facility. The new FM5504 data is from material made at the Fiberite facility 

(new) after the original manufacturer was purchased. With thc return to FM 5504, no liners have cracked 

in the chamber and throat regions in a total of 40 units built. The old lesson relearned many times in this 

industry was again demonstrated; though materials may meet the same specification, that does not 

guarantee that they will perform the same. The selected material must be well understood and no change 

should be viewed as insignificant. 

Figrrrc 5. Ring Tensile Dm/rr,fbr FA45504 vs. MX2600 
The Overwrap Process 

The purpose of the overwrap is to provide structural support to the silicaiphenolic liner. The 

materials and processes were originally selected based on low-cost and minimized part count. Much of the 

process development work was done during the investigation of the 60KOI failure. The standard ovenvrap 

material is carbon/epoxy although several nozzles were overwrapped with fiberglassiepoxy. The 

tiberglass/epoxy was chosen as a result of the failure investigation with the intent of more closely matching 

the thermal expansion of the liner and overwrap materials. 

The first step of the overwrap process is the liner dry cycle. The liner is subjected to high 

temperature to dri\ c the moisture from the machined silica/phenolic surface. Moisture can negatively 

impact the bondline between the silica/phenolic and the carbodepoxy. The teinperaturc of the 

silica/phenolic must bc ramped slowly to avoid potential cracking. 

After the dry cycle. the liner is mounted onto the filament winding mandrel and the stainless steel 

tlangc is mated to thc combustion chamber portion of the liner using HysolB EA 9628 film adhesive. Film 

adhesive is applied to the entire liner surface and carbodepoxy is then wet wound over the film adhesive 

(Figure 6). Thornel@ T-300-12K carbon fiber and EponB 828 resin were chosen because oftheir low-cost 

and commercial availability. Epi-Cure@ W curing agent was chosen because it has an extended pot life 

which acconimodates the time required for winding and curing of such a large part. 

The overwrap is vacuum-bag-oven-cured with a temperature cycle that, like the dry cycle, 

involves a slow ramp rate to avoid cracking of the silica/phenolic. After cure, the ends of the nozzle are cut 

off using a grinding wheel mounted to the vertical carriage of the filament winding machine. The mandrel 

is then removed and the nozzle is machined in preparation for bonding ofthe inctal hardware. 

Lessons Learned 

During the development of the overwrap process several challenges were overcome. Many were a 

result of work done during the investigation of the 60K-0 I failure. Some of the most notable challenges 
were wrinkling of the overwrap in the throat region after cure, bridging ofthe fibers in the transition 

regions, crack initiation in the nozzle at the very aft end and mandrel expansion during cure. 

The overwrap mandrel is a “Christmas Tree” design that supports the liner in the combustion 

chamber area and two places in the nozzle region (Figure 7). The forward end is attached by the 

combustion chamber flange to a domc/pin ring. The domeipin ring is held in place by a large nut with a 

spring washer. The spring washer serves to apply pressure to the flange and keep it properly seated on the 

combustion chamber portion ofthe liner as the mandrel expands during cure. During the development of 

the overwrap process, slippage between the mandrel and the inner liner surface was suspected. Nitrile 

butadiene rubber (NBR) was placed on the aluminum mandrel rings to prevent slippage. 

The NBR also serves another purpose. Tlic liner at the aft end tapered down to a tine edge that 

was easily chipped. The chipped area allowed cracks to initiate and propagate into the aft end ofthe liner. 

The potential for crack propagation was exacerbated by the wedge effect ofthe mandrel. The \\..edge effect 

is caused by the expansion ofthe liner during cure with the spring washer forcing the liner onto the mandrcl 

rings. The mandrel rings act as a wedge that tries to open the nozzle portion of’the liner, This problem was 

solved by machining the aft end of the liner to a flat edge before the overwrap process to prevent crack 

initiation. Application of the NBR to the mandrel rings also helped alleviate the potential for cracking by 

isolating the rings from the liner surface to allow! relative movement during expansion and contraction. 

Another issue that was overcome was wrinkling of the ovenvrap in the throat region. The bagging 

technique was adjusted to trap resin in the composite. This was accomplished by switching from perforated 

to non-perforated release film. The non-perforated release film was selectively punctured in and around the 

throat region to allow volatiles to escape but minimize the amount of resin lost. After several iterations the 

wrinkling was eliminated. This process also accomplished the task of increasing the diameter of the throat. 
The throat area is machined for the application of the belly band hardware so a larger throat diameter 

assured that cnough composite would be present for machining. 

After the failure of60K-01, the residual stress in the bondline between the overwrap and the liner 

became an important issue. One of the reasons for the residual stress in the bondline was the tooling and 

vacuum bag configuration. At the aft end, the wound fibers and vacuum bag are suspended between the 

pin ring and the end of the nozzle. The vacuum forces this suspended area down and increases fiber 

tension (see Figure 7). To minimize the impact ofthis effect. the first wound layer is cut flush with the aft 

end of the nozzle. This relieves the tension in the first layer of fibers and therefore reduces the amount of 

residual stress created during cure between the overwrap and the liner. Relieving the tension in the first 

layer also serves to reduce the potential for bridging of the wound fiber over the transition from the throat 

to the nozzle and the bump in the liner for the actuator attachment ring. 

NonDestructive Evaluation 

Once the ovenvrap is machined and prior to bonding on the metal attachment hardware, the nozzle 

is inspected by CT and ultrasonic spectroscopy (Ultraspec). These are two state oftlie art nondestructive 

evaluation (NDE) techniques that give excellent insight into the consistency of the process and the resulting 

part. The CT inspection looks for cracks, delaminations. and density gradients in the component which are 

unacceptable or out of family. The Ultraspec inspection is a technique developed by Southern Research 

Institute that detects debonds between the liner and the overwrap. Kissing debonds cannot be detected by 

CT but the Ultraspec can detect them. The Ultraspec was added to the program during the 60K-01 failure 

investigation. Several papers could be written on what has been Icamed through the use of these tools and 

it will be left to the appropriate experts to perform that task. Let it suffice to say that these advanced 

techniques have been instrumental in the success of this project. 

The Bonding Process 

After the overwrap is machined and NDE is performed, additional metal and composite hardware 

are physically bonded to the nozzle. This additional hardware facilitates attachment ofthe nozzle to the 

injector and the Thrust Vector Actuation (TVA) system. This hardware also provides mechanical support 

for components such as the gas generatorhrbopump, igniter, exhaust duct, valve brackets, and drain lines. 

Figure 8 shows a nozzle with all hardware bonded and the Themial Protection System (TPS) applied and 

painted. 

Fig, 

Exhairst DMI Support Bruckrt 

' 11'1 

the 

rh 

7 

all 

PS 

The first three components bonded to the nozzle are the gas generatorlturbopumpligniter support 

belly band, the actuator attachment ring (AAR), and the exhaust duct support bracket. These components 
arc machined from 300 series stainless steel. The remaining components. the valve bracket and dram line 

support pads, are molded from a composite sheet molding compound (SMC). LytexTM 9063, manufacturcd 

by Quantum Composites Inc. 

All of the bonding operations are performed in much the same manner. The hardware is placed in 

a fixture or tooling is put in place to insure accurate positioning. The hardware is then dry fitted to the 

nozzle to verify positioning and to determine shimming requircments. The shim aid in placement ofthe 

hardware during actual bonding and also provide a minimum bondline thickness for the adhesive. The next 

step is surface preparation. The exact surface preparation method is dependent on the material of the 

surface being bonded. Metal hardware is hand wipc cleaned, grit blasted with a zirconia or silica media, 

inspected by black light, and then primed with a silane-based primer. Compositc hardware, and the surface 

of the chamberinozzle itself. are hand wipe cleaned and grit blasted with an alumina media. Shims are then 

affixed to the hardware as required, and surfaces of the nozzle and hardware that are not involved in the 

bonding operation are masked. The adhesive used for bonding operations on the Fastrac enginc is HysoIR 

EA 9394, a two part structural paste adhesive. The adhesive is mixed and then applied to both the 

hardware and the nozzle surface. Following adhesive application the hardware is positioned and held in 

place until a sufficient degree of cure is achievcd to allow nozzle movement. 

Two components, the AAR and the exhaust duct support bracket, undergo additional processing to 

install shear bolts following initial bonding. The shear bolts enhance the transfer of loads from the AAR 

and exhaust duct support bracket to the nozzle. The bolts ensure that the loads are transmitted to the entire 

thickness of the nozzle and not just the outer ply of the structural overwrap. Holes are machined through 

the metal hardware and the structural ovenvrap and into the silicaiphcnolic liner. The bolts are then 

installed wet with HysolB EA 9394 adhesive and the adhesive is allowed to cure. 

The TPS consists of sheet cork bonded to the exterior of the ovenvrap with Hysol~B~ EA 9394 

adhesive. The process is performed using standard vacuum bagging techniques. An ablative compound, 

RT-455 from Resin Technology Group LLC. is then applied to cover the exhaust duct support bracket and 

to fill in any gaps in the cork. Following cure, the cork and RT-455 arc coatcd with an acrylic latex paint 

produced by Acrymax Technologies, Inc., SP 130XT-LV. 

Lessons Learned 

Most of the challenges encountered in the evolution of the bonding process related to development 

of tooling and techniques to insure correct positioning of the hardware. Of necessity the initial tooling was 

makeshift and prone to errors and excessivc variability. Over time it has matured into a very stout and 

reliable production system. This system includes a specialized fixture and tooling plates used to hold the 

metal components and the entire nozzle in place during bonding (Figures 9 and IO). Optical alignment 

equipment was used to set up the fixture. This assured proper leveling and parallelism. Axial adjustments 

are made to the components being bonded using two-piece tooling plates mounted to a drive screw system. 

In addition, a plumb bomb was incorporated into the fixture to aid in angular positioning of the hardware. 

To maximize positional accuracy, all measurements are taken relative to the combustion chamber flange 

and each of the bonding operations is performed independently. Lastly, hardware locations are verified 

following bonding using a portable coordinate measuring machine (CMM). 

During process development the bonding plates underwent significant refinement. The bonding 

plates for the belly band were modified to more closely match the taper of the nozzle. This allowed for a 

better mating with the nozzle and sufficient room for the belly band plates to actuate more effectively. In 

addition, the thickness of the exhaust duct support bracket bonding plates was increased to eliminate 

unwanted flexing. The reasons for the flexing were twofold. First, the exhaust duct support bracket is 

mounted at the largest diameter portion ofthe nozzle, so the width of its bonding plates is the smallest of all 

the plates. Second, during bonding the adhesive provides a resistance to placement of the hardware in the 

form ofa hydraulic pressurc. Flexing also occurred with the positioning plates that support each belly band 

half and actuates them toward the surface of the throat. As the plates were extended toward the throat, the 

weight of-the belly band halves caused flexing. Separate actuating supports were installed to allow the 

positioning plates to be supported along their full range of motion. 
Tooling was also the key to sufficient accuracy and precision when bonding the compositeiSMC 

components. The compositciSMC components are bonded to the nozzle in sets of 2-3 pieces each. using 

tooling that bolts to the prcviously used bonding plates or the previously bonded hardware. This tooling 

was developed based on models of the hardware to be attached to the nozzle during final assembly. Figure 

I 1 shows the bonding ol'the \dve bracket support pads to the nozzle. 
Summar\ 

The development ofa low cost nozzle for the 60K Fastrac Engine has been succcssful. The 

success was achieved by using well-understood material technology in a new way. Ablative, bonding and 

TPS technology from RSRM and structural composite technology from multiple projects provided the 

knowledge. With a little innovation and willingness to take some risk these materials were combined into a 

single unit with no joints. The manufacturing was simple, it contained a minimum number of steps and as 

much automation as possible. The only exception being the TPS that used old, hands-on technology due to 

project cost constraints at the decision point. 

A significant amount of testing has been performed to evaluate the nozzle’s capability to 

successfully meet the X-33 flight requirements. Flight requirements are for each nozzle to be used for a 

single, 159-second burn, and to survive intact the reentry and landing loads. To date, a shortened 

development nozzle has survived 4 starts and an accumulated 342 seconds of hot fire and a full-length 

development nozzle has survived 7 starts and an accumulated 282 seconds. In order to evaluate the 

capability of the bonded actuator attach ring, one nozzle actuator attach ring was loads tested and failed at 

180% of the maximum expected load. The nozzle design was modified based on thermal-structural 

analysis and testing continues to verify the nozzle satisfies all performance requirements. Nothing has been 

found that would indicate future problems. The nozzle is believed to have demonstrated that it is a robust, 

low cost design for liquid engine applications and siinilar designs could be incorporated into other systems. 

Acknowledgments 

The success of this prqjcct is due to the many people at all levels who have taken a special pridc in 

creating a robust component. A special thanks goes to the many technicians at Thiokol. Lockheed Martin, 

and ASRI whose craftsmanship and commitment were instrumental in resolving the issues faced during the 

development of the nozzle. 
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Composite, Cryogenic, Conformal, Common 

Aerogel-insulated Tank (CBAT) 

Bulkhead, 

Materials and Processing Methodologies 

J. Keith Roberts and Michael P. Kovach 

Thiokol Propulsion 

SEHO Operations 

P.O. Box 707, MIS 200 

Brigham City, UT 84302 

William M. McMahon and Jeffrey L. Finckenor 

National Aeronautics and Space Administration 

George C. Marshall Space Flight Center 

Marshall Space Flight Center, AL 35812 

ABSTRACT 

The objective of the Composite, Cryogenic, Conformal, Common Bulkhead, Aerogel-insulated Tank 

(CBAT) Program is to evaluate the potential for using various new technologies in next generation 

Reusable Launch Vehicles (RLVs) through design, fabrication, and testing of a subscale system. The 

new technologies include polymer matrix composites (PMCs), conformal propellant storage, common 

bulkhead packaging, and aerogel insulation. The National Aeronautics and Space Administration (NASA) 

and Thiokol Propulsion from Cordant Technologies are working together to develop a design and the 

processing methodologies which will allow integration of these technologies into a single structural 

component assembly. Such integration will significantly decrease subsystem weight and reduce shape, 

volume, and placement restrictions, thereby enhancing overall launch system performance. 

This papedpresentation focuses on the challenges related to materials and processes that were 

encountered and overcome during this program to date. 

INTRODUCTION 

One of the ongoing goals of the National Aeronautics and Space Administration (NASA) is to 

lower the cost of access to space. This objective is achieved through research and development into 

technologies that may be used to improve current and future space transportation systems. These 

technologies may result in improvements in safety, reliability, performance, cost, or operating efficiency. 

The Composite, Cryogenic, Conformal, Common Bulkhead, Aerogel-insulated Tank (CBAT) program has 

the potential to positively influence each of these areas. 

What is CBAT? The name, CBAT or Composite, Cryogenic, Conformal, Common Bulkhead, 

Aerogel-insulated Tank, refers to the enabling technologies andlor the functionality desired in the end 

product. CBAT seeks to demonstrate and assess the potential for system improvements through the 

integration of various technologies. These technologies include polymer matrix composites (PMCs), 

conformal propellant storage, common bulkhead packaging, and aerogel insulation. 

Evaluating the aspects of the system that the name suggests--Composite refers to the PMCs that 

will be used to fabricate the system. PMCs are the materials of choice for most of today's aerospace 

applications. They provide a unique combination of high strength and stiffness with low material density 

relative to metals. In addition, many properties of composite materials are anisotropic (directional). 

Therefore, these materials and their use may be tailored to a specific design. Other advantages of PMCs 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
include their resistance to fracture, corrosion, and wear, ease of fabrication and assembly, ability to be 

fabricated to net shape, and capacity to facilitate component integration. 

Cryogenic refers to the prospective propellants for use with the system. One of these propellants 

is liquid oxygen (LOX). LOX is a very harsh environment and hence presents many challenges to system 

designers. Two of its primary challenges are reactivity and low vaporization temperature. Some 

materials are susceptible to oxidation or combustion at standard atmospheric conditions. As oxygen 

concentration and pressure increases, the frequency and the severity of these reactions tend to increase, 

making a LOX environment very inhospitable to many materials. The other primary challenge, the low 

vaporization temperature of LOX (-297"F/-183"C), results in significant stresses and strains being induced 

simply due to thermal gradients and/or differences in coefficients of thermal expansion (CTEs). The 

materials have therefore been chosen with respect to the LOX environment. However, testing for this 

program will initially be performed using liquid nitrogen (LN2, T,,,(LN2) = -320°F/-196"C) to mitigate cost 

and safety issues. 

Conformal refers to customizing the shape of the propellant storage system to the shape of the 

vehicle in which it will be used. . This customization provides two significant benefits. It allows a designer 

to maximize the amount of propellant storage within a given space in the vehicle. It also facilitates the 

integration of the tank structure into the vehicle structure. Overall, this ability reduces the restrictions 

placed on the vehicle designer. 

Common bulkhead refers to the methodology for placing or packaging the propellant storage 

tanks within the vehicle, in this case, one adjacent to the other with a common interface in between. This 

ability removes additional constraints on tank shape and placement. For previous cryogenic propellant 

systems this arrangement has been very difficult to accomplish. Due to the high thermal conductivity of 

the materials used, and the difference in temperature between the propellants, freezing of one of the 

propellants would invariably become a serious concern. 

Lastly, aerogel-insulated refers to the use of a special class of materials, aerogels, between and 

around various portions of the system. Aerogels are some of the lightest solids ever produced. Highly 

porous and almost wispy in appearance (Figure l), aerogels produced from such materials as silica, 

alumina, or zirconia can have densities as low as just three times that of air (Paerogel - 0.003 g/cm3). 

Another result of their highly porous nature is their low thermal conductivity. Aerogels can insulate almost 

40X better than the best fiberglass insulations. This makes aerogels one of the best insulators available 

today (Figure 2). 

Figure 1: The wispy, fragile appearance of an 

aerogel shown protecting a flower from 

being consumed by a burner. 

Figure 2: Tom Tillotson, a chemist at Lawrence 

Livennore, applies a flame to the top 

I-inch-thick silica aerogel brick. Even 

though a thermocouple placed on the 

aerogel's top surface reports a 

temperature of 2,108"F, his hand is 

totally unaffected by the heat. 

3f a 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
Particulate/granular forms of these materials are also available. These forms trade off some of the 

density and thermal advantages for improvements in strength and ease of use. 

The CBAT program will evaluate the potential for using and integrating these technologies 

through design, fabrication, and testing of a subscale system. This effort is considered critical to enabling 

development of the second generation of NASA RLV. The program is currently nearing the end of the 

design phase and the start of the fabrication phase. 

The design created by NASA’s George C. Marshall Space Flight Center (NASA/MSFC) and its 

industry partners incorporates each of the aforementioned technologies and functionality. This design is 

shown in Figures 3a through 3c. The design is based on a graphite/epoxy PMC. It will be fabricated by a 

combination of hand lay-up and filament winding, using both pre-impregnated (prepreg) fabric and 

tow/yarn. The system is designed for the LOX environment, and with some minor materiallprocessing 

changes, may also be evaluated for use with hydrogen. The system and the tanks within the system 

have noncircular cross-sections. The shape is considered representative of one that would be used in 

conjunction with a lifting body-type RLV. The system also employs a common bulkhead between the two 

propellant tanks. The bulkhead functions in both structural and thermal capacities. The bulkhead utilizes 

graphitelepoxy and honeycomb to provide strength and aerogel-based material to provide insulation. A 

rapid prototype (RP) model of the system design was developed using the stereolithography apparatus 

(SLA) and laminated object manufacture (LOM). This model has been used to verify component form 

and fit. 

This paper focuses on the challenges related to materials and processes that were encountered 

and overcome during this program to date. 

Figure 3a: CBA T propellant tank design. 

Cross-section is D-shaped in the plane 

perpendicular to the anticipated vehicle 

axis. 

Figure 3b: Assembly of the CBA T propellant tanks 

around the bulkhead and insertion into 

the system skirt structure. 

Figure 3c: Final assembly of the CBA T skirt 

sandwich structure. The skirt is 

composed of inner and outer 

graphitelepoxy skins bonded to a 

honeycomb core. 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
MATERIALS AND PROCESSES 

At the beginning of any composite fabrication effort, potential fabrication methods must be 

evaluated. After the fabrication method is determined, the tooling and types of materials must be 

considered. For the CBAT propellant tank, the chosen method of fabrication is a combination of polar 

filament winding and hand lay-up. The tank material will be lM7/977-2 pre-impregnated filament winding 

tow and 5 harness satin (HS) cloth. The tooling will be a removable mandrel made from a sand 

replacement called MacroliteTM. The following sections deal with the evaluation, selection, and 

development of the materials and processes for the fabrication of the CBAT system. 

Filament Winding 

Polar winding was chosen as part of the fabrication of the CBAT propellant tanks to minimize the 

amount of fiber build-up in the dome regions. A 16 by 22-inch portion of the dome region will be cut out 

for the manhole door. Excessive build-up in this region would create mating problems for the door and 

the tank. Polar winding will alleviate this issue because no crossovers will occur in the filament winding 

pattern in the dome. Helical winding would create a greater thickness build-up in the dome region 

because of the crossovers that occur in a helical pattern. Polar winding creates a build-up directly 

adjacent to the polar boss but that area will be removed for door installation. 

Since the CBAT propellant tanks have a flat portion in the common bulkhead region, filament 

winding will be challenging because of the changing contour. The filament winding program that controls 

the machine motion will be generated for a 60 inch diameter cylinder, but the tank shape creates a 

variation in diameter from 60 inches to 36 inches with a flat side. This will obviously lead to tow overlaps 

and potential tow slippage in some areas of the barrel sections of the propellant tanks. The greatest 

potential for tow slippage occurs in the transition from the cylindrical sections to the flat sections of the 

tanks. 

One-fifth scale models were wound using a polar pattern to determine if these issues would be 

insurmountable. Both slippage and overlaps occurred in initial trials. A layer of film adhesive was then 

applied to the mandrel to give a tacky surface for the tow to grab. This was successful in minimizing 

slipping on the small-scale model. A higher resin content; i.e., tackier, version of the lM71977-2 was also 

ordered for the full-scale tanks to further alleviate any problems with slipping. Issues associated with the 

transition regions will also be reduced upon scale-up to the full-sized tank. This effect will be due to the 

reduction in the size of the tow relative to the geometric features of the tank and the winding pattern. For 

example, overlaps will occur, but these should be less prominent on the full-scale tank because they will 

be spread over a larger area. To illustrate the differences between polar and helical patterns, figure 4a 

shows a one-fifth scale model that was wound with a polar pattern, and figure 4b shows a one-fifth scale 

model that was wound with a helical pattern. Notice the crossovers in the dome of the helical wound 

model. 

Figure 4a: Polar wound one-fifth scale model of 

a CBAT Propellant Tank. Polar 

winding minimizes build up in the 

domes due to fewer crossovers. The 

non-cylindrical shape creates fiber 

tow overlaps in the flat regions. 

I 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
Figu rre 4b: Helical wound one-fifth scale model of a 

CBA T Propellant Tank (before cure). 

Helical winding causes more build up in 

the domes regions because of the 

crossovers. 

Hand Lay-up 

Pre-impregnated IM7-977-2EHS cloth will be hand laid, as the design requires, over the three 

regions of the propellant tanks. The hoop region will require 16 plies, the dome regions will require 10 

plies and the door build-ups will require 20 plies. Laying the hoop plies and the door build-up plies should 

be relatively typical. The dome regions will require more attention. 

The issue involved with the cloth lay-up on the domes is the challenge of getting a flat piece of 

cloth to conform to an 18-inch spherical surface. Obviously the fiber pattern in the cloth material will 

distort. NASNMSFC Structures and Design personnel used PATRAN@ Laminate Modeler to simulate 

how much fiber distortion would occur as the cloth was draped over the spherical dome regions. Also, a 

drape test was conducted with 5HS cloth to determine the degree of ply distortion that would occur. 

Figure 5 shows the result of the drape test. The dashed tracer lines follow individual tows within the 5HS 

cloth and show the distortion as the ply is wrapped around the dome. Figure 6 is the result of the 

modeling that was done to simulate the fiber distortion in the cloth. The model shown in Figure 6 

accurately predicted the results of the actual drape test. 

Fig1 yre 5: The results of the 5HS 

cloth drape test on a 36 

inch diameter dome. The 

dashed tracer lines follow 

individual tows within the 

cloth. The solid line 

represents the centerline of 

the dome. 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
Figure 6: PA TRAN@ Laminate 

Modeler software was 

used by the MSFC 

Structures and Design 

Group to predict the 

fiber distortion as the 

cloth draped on the 36 

inch domes. The image 

shown is from 

UnigraphicslFiberSlM. 

Material 

MacroliteTM M357 

MacroliteTM M714 

Tooling 

(1bsJcu.R) 

21 

25 

The major parameters for selection of the mandrels for fabrication of the propellant tanks were 

weight, ease of removal, and dimensional stability. Sand mandrels are typically a first choice because of 

their ease of fabrication, ease of removal, and low cost. The mandrels for the CBAT propellant tanks wilt 

each be 48 cubic feet. A sand mandrel would weigh approximately 4000 pounds. Urethane foam was 

another option that was considered. Foam is lightweight and could be machined to the proper tank 

dimensions. Foam was eliminated as an option for the CBAT propellant tank mandrels because of the 

lack of dimensional stability. Since the foam has a high expansion rate and the CBAT mandrels will not 

be cylindrical, the expansion in the different regions of the tank would be difficult to predict. After 

considering the options, a lightweight ceramic material, MacroliterM, was chosen for the CBAT propellant 

tank mandrels. 

MacroiiteTM M 1430 

MacroliteTM M3050 

Macrolite" M4060 

MacroliteTM is actually a water filtration media that consists of various sizes of ceramic spheres 

(see Figure 7). MacroliteTM is used for tooling by some composite manufacturers including Thiokol 

Propulsion in Brigham City, Utah. The M&P Composites group at Thiokol-Utah researched various 

combinations of the different size and density MacroliteTM particles (Table 1) (Yorgason). These particles 

were mixed with alumina microspheres and a binder, polyvinyl alcohol (PVA). An optimized mix was used 

to fabricate a 97-inch diameter 1 IO-inch long mandrel. The information from this research was used to 

begin the development of a Macrolitem mandrel for the CBAT propellant tanks. 

28 

30 

56 

MacroliteTM M7080 60 

Table 1: Densities for all the Macrolite 

particles and sand. The M4060 

and M7080 particles were 

deleted from the final mix and 

replaced with sand. 

Sand 95 
The cure of the 977-2 epoxy resin used in tank fabrication will take place at 350°F (177°C). 

However, PVA tends to react adversely at such temperatures and produce mandrels with significantly 

lower solubility. For this reason sodium silicate was substituted as the binder in the CBAT program. 

Unfortunately, using sodium silicate as a binder with the MacroliteTM particle mix developed at ThiokolUtah also created relatively insoluble mandrels. After discussions with the sodium silicate vendor, PQ 

Corporation, and many trials, a successful mixture was tested. This mixture included a reduction in the 

percentage of binder used from 10% to 8%, and elimination of the smallest MacroliteTM particles (M4060 

and M7080) and alumina microspheres. These particles were replaced with sand. The difficulties that 

were encountered are thought to have been the result of the high surface area associated with the fine 

MacroliteTM particles. This leads to greater wetting and absorption of the binder by the MacroliteTM. 

These fine particles also pack together better, thus eliminating porosity and preventing the water from 

penetrating the mandrel during washout. The addition of sand allowed the hot water to penetrate through 

the mandrel more readily, and therefore break downldissolve the sodium silicate binder at a faster rate. 

The MacroliteTM mix reduces mandrel weight by 70% when compared to sand. The addition of the sand 

led to a MacroliteTM mix that was 3% heavier than the mix established by Thiokol-Utah. 

Figure 7: A photograph of the various Macrolite T~~f particles alongside sand. Notice the 

different size particles within the sand while the Macrolite T~f particles are 

relafively consistent especially in the smaller sizes. 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
SUMMARY 

The CBAT program will evaluate the potential for building a conformal composite tank system that 

integrates a common bulkhead with aerogel insulation to reduce subsystem weight and volume, thereby 

enhancing the performance of future reusable launch vehicles. Although in the early stages, the CBAT 

fabrication effort has encountered and overcome several obstacles. The issues associated with filament 

winding a non-cylindrical shape, while not proven on a large scale, have been minimized through material 

selection and proper fabrication sequence. The hand laying of cloth onto the dome sections has been 

successfully tested to allow integration into the design models. Lastly, a lightweight mandrel material has 

been tailored to meet the specific requirements of the CBAT program. 

ACKNOWLEDGEMENTS 

This work is being funded under a contract with NASA’s George C. Marshall Space Flight Center 

(NASNMSFC). The authors would like to thank NASNMSFC, and the following individuals who have 

contributed significantly to this effort: 

T.W. Dillard 

D.E. Lawrence 

P.D. Thompson 

G.L. Young 

Thiokol Propulsion - Composite Technology 

Thiokol Propulsion - Composite Technology 

Thiokol Propulsion - Composite Technology 

Thiokol Propulsion - Composite Technology 

REFERENCES 

1. Yorgason, James A., “LIGHTWEIGHT/LOWCOST MANDREL,” Thiokol Propulsion - Science and 

Engineering, TR11449, November 21, 1997. 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
Coating removal technology using starch based 

abrasives, a review of current Aerospace 

application using the Envirostrip dry stripping 

process. 

by Denis Monette and Cameron Drake 

Archer Daniels Midland 

September 2000 

995 Mill Street Montreal, H3ClYS 

Phone: 514-846-8516 
Coating removal technologj using starch based abrasives, a review of current Aerospace applications 

using the Envirostrip dry stripping process. 

Drake Cameron. Monette Denis, Archer Daniels Midland, 995 !Will St. Montreal QC, Canada, 

H3CIl-5. Tel: 514 846 8516 

INTRODUCTION 

Due to stringent environmental regulations enacted in the past 10 years, methylene chloride (MC) 

has been phased out in many industries because it is harmful to the environment and to the workers 

exposed to it. The aerospace industry, historically a large user of MC, researched and adopted many 

environnientally acceptable alternatives to replace methylene chloride based paint strippers. This has 

proved to be a very difficult task as MC chemical strippers have been very effective in removing tough 

polyurethane/’epoxy coating systems typically found on aircraft structures 

A variety of new “environmentally acceptable (EA) chemicals” were developed in the last five 

years to replace MC. These EA chemicals are considered safer because the chemicals are not as volatile, 

having very low evaporation rates. However, there are still some concerns that new EA chemicals may still 

pose unknown health risks to workers, as well as causing potential damage to aircraft structures due to long 

term ingress problems. Because MC strippers evaporate so quickly, problems associated with chemical 

ingress were rare. The potential for the new EA chemicals to damage and.’or corrode sensitive aircraft 

structures is a new problem due to the low evaporation rates (low volatility) of these MC chemical 

substitutes. 

Ten years ago, an alternative non-chemical, paint removal process was introduced to the aerospace 

industry. This process uses a dry abrasive media, EnviroStrip@ wheat starch, projected at low pressures to 

remove virtually every type of organic coating froni most aerospace materials. This media was considered 

more gentle than other dry media used at the time (e.g. plastic media). EnviroStrip@ wheat starch. as the 

trademark implies, is manufactured from wheat starch. a biodegradable renewable resource. giving the 

product inherently high purity and uniformity. 

Extensively tested, approved and used in production applications by Northrop Grumman. 

Raytheon, C‘essna and Boeing, the EnviroStrip@’ process has been embraced for its coating removal 

effectiveness on metals and composite substrates. In 1998, a new sister product, EnviroStrip@ XL was 

commercially launched (ref.4). This newer abrasive product is made from a corn hybrid polymer and 

offers improved water resistance. Today, EnviroStrip@ XL is successfully used by major companies in the 

aerospace industry. 

This paper will describe the methods of manufacturing these abrasive media products, the 

equipment used to apply the process, and the various applications for this technology in the Aerospace 

industry. Examples are selective stripping, metal bond adhesive removal and interior aircraft panel 

refurbishment. The production use of this dry stripping method on the Northrop Grumman B-2 bomber, 

the NASA Space Shuttle and other aircraft types will also be reviewed. 

DISCUSSION - THE ENVIROSTRIPm TECHNOLOGY 

The EnviroStrip. Abrasives 

The starch-based media particles are irregular in shape and have sharp, angular edges (fig. 1-2). 

The media is amorphous in nature and semi-opaque to light. By weight the media has approximately 10-13 

90 moisture content. An interesting aspect of the media is the conditioning effect. After being projected 

several times. the media becomes more productive after each use. Two mechanism are at play: the average 

particle size range of the batch starts to widen to a more productive broader range (Le. 12-100 mesh size ) 

(ref 8) , and the media loses 1-20.0 of moisture which in effect sharpens the media. The principal difference 

between the wheat starch media and the corn polymer media is that the latter can better withstand contact 

nith water. 
The EnviroStrif Manufacturing Process 

EnviroStrip@ wheat starch media and EnviroStrip@ XL corn hybrid polymer are manufactured 

from pure native starches. A primary advantage of using a starch raw material is its purity and uniformity, 

and the absence of foreign particulates that are denser than the final starch abrasive product. The raw 

starch powder is fed to an extruder and heated in the presence of water to form a solid starch mass. Upon 

exiting the extruder, the starch material is formed into strands that are cut into pellets. These hard plasticlike pellets are cooled and tested for hardness. The starch pellets are then ground to various mesh sizes 

(e.g. 12130 mesh). 

The Process Equipment 

When EnviroStrip@ wheat starch was first introduced 10 years ago. it was used in dry media blast 

systems designed for light-abrasives such as plastic media. While EnviroStrip@ media could be adequately 

used in these blast systems, it was found that certain design changes improved overall process efficiency. 

The major blast equipment manufacturers have since implemented important equipment design changes, 

helping to fine tune the EnviroStrip@ coating removal process. Increased pressure pot angles (60+ 

degrees). better media flow control valves, and enhanced dust removal techniques were incorporated into 

the new generation of light-abrasive blast systems. These enhancements have improved EnviroStrip@ 

coating removal rates and reduced media consuniption. 

There continues to be great strides in both North America and Europe in improving dry media 

blast systems. Flat nozzle technology, introduced recently into the light-abrasive coating removal industry, 

has had a significant impact on EnviroStrip@ media performance. Flat nozzles have demonstrated strip rate 

increases of over I0040 when compared to conventional round nozzles. The computational fluid dynamic 

programs used to design the flat nozzle revealed that media can be more uniformly distributed to the 

surface through a flat nozzle. minimizing media overlap and the “hot-spot” typically found in round 

nozzles. 

Closed-cycle (dust-free) dry media blast systems have also evolved to support aerospace coating 

removal requirements. Historically closed-cycle systems used small nozzles designed with a 90-degree 

impingement angle to the working surface. These systems were difficult to use, slow to remove coatings 

and did not provide the operator sufficient viewing of the blast area. Major advances have been achieved 

with the introduction of closed-cycle systems designed for EnviroStrip@ media. The new closed-cycle 

systems utilize the more efficient flat nozzles that are set at an optimal 45-degree angle to the working 

surface. In addition, a viewing window on the applicator head now allows the operator to see the blast 

process in progress. This helps operators to improve strip rates and, when possible, selectively strip 

coatings (Le. remove top coat, leaving primer intact). Most closed-cycle systems are portable and can be 

used for both on and off aircraft paint and adhesive removal applications. 

Benefits of Automation 

The aforementioned improvements in media process equipment and nozzle design for starch 

media have allowed automation to yield further process benefits. High production rates on sensitive aircraft 

parts, providing controllable and repeatable surface finish, can now be accomplished with current 

automated system technology. Past work (ref 9 ) has shown that production strip rates increase by up to 

300’#0 when using semi and fully automated blast systems. Automated production work is presently being 

conducted on aerospace structures at several locations worldwide. For example, the Boeing-ASTA facility 

in Australia has implemented an automated starch media system for both composite coating removal and 

composite surface treatment. The composite surface preparation process is performed on Boeing 

manufactured carbon fiber parts. The system, using a large flat nozzle. has proven its ability to meet and 

exceed production demands without damage to the sensitive composite substrates. 
Automated control of the nozzle movement allows a larger nozzle size and media flow rates to be 

applied. This. in turn, delivers higher strip rates and lowers material costs. Precise control can be assured, 

minimizing surface damage at higher production rates. Automation of the starch-based dry niedia process 

has proven to be an effective production technology in off-aircraft component stripping. 

lClechanica1 Effects on Aerospace Materials 

Most coating removal processes can induce unwanted surface effects on aerospace materials. Dry 

stripping causes two types of mechanical effects, residual stress and surface modifications. Residual 

stresses produced by dry media blasting are compressive in nature and are concentrated at the surface, 

similar to the effects produced by shotpeening. Within limits, compressive stresses at the surface of 

metals can actually be beneficial. Shotpeening studies have shown that compressive stresses can retard the 

onset of fatigue and corrosion in metals. However the potential of a dry stripping media to induce different 

compressive stress intensities( partial coverage) ( ref 6) can negatively affect the fatigue life of thin skin 

aluminuni control surfaces and fuselage sections. With such concerns in mind, the Boeing Commercial 

’4ircraft Division issued service letters (1993, 1995) restricting the use of plastic media on Boeing civil 

aircraft structures. In turn. Boeing allowed EnviroStrip” wheat starch to be used an unlimited number of 

times on aluminum (>0.032-inch thick) as a preferred non-chemical alternative to remove coatings from 

thin aluminum surfaces. 

The standard method used for years to gauge residual stress inducement in a substrate is the Aero 

Almen method. Developed by the IJSAF in the early 1980’s, the method was borrowed from the shotpeening industry. Instead of using steel specimens, the USAF method uses 2024 T-3 aluminum strips 

which are 3 inches long by 0.75 wide inches and 0.032-inch thick. An Almen strip and strip holder are 

shown in fig 3. The higher the arc height or deflection of the Almen strip when blasted with an abrasive 

media, the higher the potential negative effect on the fatigue life and fatigue crack growth rate of that 

particular substrate. Figures 4 and 5 shows two panels 0.032-inch thick. One panel was stripped with 

EnviroStripO wheat starch and had a corresponding i\lmen arc height of 0.003-inch. while the second panel 

was stripped with plastic media (Type V) and had a corresponding arc height of 0.007-inch. Note the 

difference in the mid plane deflection of the panels. The USAF, a longtime pioneer in researching new 

depaint technologies, sets a criteria that arc heights for any mechanical process not exceed 0.006 inch. 

Figure 6 shows typical saturation curves for EnviroStrip@ wheat starch, EnviroStripO XL and plastic media 

blast (Type V Acrylic) processes. Finally, aircraft components are often dry stripped prior to liquid 

penetrant inspections; the results of an AGARD report indicated that using starch media gave better 

inspection results than the more agressive media types (ref 2 ) 

EnviroStrip. Application Overview 

Adhesive Removal 

Removing adhesives and sealants from sensitive substrates has always been a challenging 

operation. Historically, mechanical methods have utilized hand scraping or mechanical sanding. These 

methods are slow and often cause unacceptable damage (fig. 7). EnviroStrip@ abrasives have the ideal 

characteristic of being able to efficiently remove various adhesives without compromising the bond primer 

found under the adhesive layer (fig 8 ) 

Northrop Grumman B-2 

The world’s most sophisticated aircraft have been processed with EnviroStrip@ wheat starch since 

1993 (ref 13 ). After exhaustive evaluation of all alternative methods, the EnviroStrip@ wheat starch was 

the only process found to remove special thick coating systems without affecting the carbon fiber substrate 

found on the B-7. 
Space Shuttle 

The EnviroStrip@ process is,used to strip the thermal protection system (TPS) adhesive from the 

Space Shuttle vehicles. Over 3000 ft- of the Shuttle vehicle's upper wings. side body, and payload bay 

doors were processed. (ref 7 ) 

SlJBSTRATE TYPE 

Fiberglass 250 F Cure 

Fiberglass 350 F Cure 

Selective stripping 

BOEMG MATERIAL SELECTIVE FINISH COMPLETE FINISH 

SPECIFICATION REMOVAL CYCLES REMOVAL CYCLES 

BMS 8-79 Unlimited Two 

BMS 8-1 39 Unliniited Five 

Selective stripping is a coating removal technique where the top-coat is removed and the base 

primer coat is largely left intact. There are several advantages to this technique. Leaving the primer coat 

intact eliminates surface effects on various substrates, which is particularly beneficial for composite 

structures. Another advantage is a reduction in toxic metals found in the starch media waste. This occurs 

because the heavy metals (e+ chromium) are predominantly found in the primer coat, and are thus not 

removed when selective stripping is performed. (ref IO) Airbus Aircraft recommends selectively stripping 

coatings from their aircraft. 

Two 

Five 

I BMS 8-1 68 Unliniited 

BMS 8-2 12 Unlimited 

BMS 8-256 

BMS 8-776 

I ' CFRP (Carbon,'Epoxy) 

250 F Cure 

CFRP (Carbon+'Epoxy) 

350 F Cure 

Aramid (KevlariEpoxy ) BMS 8-2 I 8 Unlimited None 

Wire Mesh Lightning BMS 8-336 Unlimited None 

Strike Protection 

Aluminum Flame-Spray BAC 5056 Unlimited None 

BMS 8-2 I9 

Composite Structures 

The most widely used media for composite stripping. EnviroStrip@, is presently used by several 

repair and overhaul facilities. At these locations, various coating systems are removed from commercial 

airliner composite structures. As an example, the following Boeing materials are approved for stripping 

with EnviroStrip@ wheat starch. 

SUBSTRATES APPROVED FOR WHEAT STARCH MEDIA BLASTING 

Ref: Boeing D6-56993 
Aluminum Structures 

The majority of fuselage skins have a thin layer of pure aluminum, known as Alclad, that covers a 

high strength aluminum alloy. This clad aluminum layer provides corrosion protection for the underlying 

alloy. and therefore it is imperative that any alclad removal is minimal and that the resulting surface 

roughness is ivithin acceptable limits. For example, the general guideline for surface roughness should not 

exceed 125 pinches (%) on 0.032-inch thick clad aluminum skins. 

Today's aging aircraft have been subjected to multiple chemical paint strip cycles and some have 

very little clad left on their skins due to the aggressive scrubbing needed to remove residual paint. 

EnviroStrip@ wheat starch surface roughness data, reported by Beech Aircraft in 1992 (ref 5), is shown in 

the table below. These results are typical and have been validated in numerous test programs worldwide. 

Note that clad thickness is 5% (front and back) of total thickness of skins up to 0.063 inch; above 0.063 

inch, aluminum clad skins are 2.500 front and back. With increasing clad layer thickness, the resulting 

surface profile will become slightly rougher. 

Clad Skin Clad Layer After blasting 

Thickness Thickness Roughness uinches (Ra) 

0.020 inch 0.0010 (540) 40 

0.03 inch 0.0013 (5'0) 70 

0.032 inch 0.0016 (soo) 90 

0.040 inch 0.0020 (so,) 142 

0.080 inch 0.0020 (3.54,) 132 

DISCUSSION - CHEMICAL STRIPPING - SOME HAZARDS STILL REhlAIN 

Methylene chloride, also known as Dichloromethane, is considered a very toxic chemical. It can 

damage the liver. heart and central nervous system (ref 14). Past studies concluded that its use was so 

\vide spread in \.arious industries that most of the general population was exposed to it .The main route of 

exposure is via inhalation. 

ESTIMATED DAILY INTAKE OF DICHLOROMETHANE 
Despite its toxic nature, Dichloroniethane has proven to be very effective in removing aircraft 

coating systems, with its main advantage being speed. When compared to the myriad of new 

environmentally acceptable (EA) strippers, methylene chloride (MC) is still by far the most effective. For 

example, if it takes MC 2-6 minutes to remove a given coating system, the EA chemical alternatives will 

take at least 50 tinies longer (i.e. 2-8 hours). 

There have always been hazards to the airframe when chemical strippers are applied. One of the 

most severe incidents involved a commercial aircraft which lost a 5ft by IO ft section of its rudder during a 

trans Atlantic flight (ref 12). The failure was attributed to residual chemical stripper coming into contact 

with the composite tail rudder. The chemical damaged the resin matrix allowing water to enter the 

composite structure. The resulting failure was a delamination of the composite skin plies from the rudder 

assembly. Other reported examples of chemical damage are cases where the wrong chemical was used or 

improper chemical application was involved. resulting in damage to various parts of the aircraft including a 

forward landing gear. 

Environmentally Acceptable Chemical Strippers 

When using the new EA chemicals one must consider the different types of products available and 

the potential risks involved. There are basically three types of EA chemical strippers: alkaline, acid and 

neutral. A neutral pH (i.e. pH 7 k I ) chemical is preferred, provided it reniains stable. while acid or 

alkaline strippers present different corrosion risks. 

ALKALINE: “Aluminum is a reactive metal, but develops an aluniinuni oxide coating or film that 

protects it from corrosion in many environments. This film is quite stable in neutral and many acid 

solutions but is attacked by alkalies.” (ref I ) 

ACID: High Strength steel such as AIS1 1310 is used on aircraft in very critical applications, they include 

landing gear components, engine parts and critical fasteners and bolts throughout the aircraft. If an acidic 

solution comes in contact with high strength steel, hydrogen embrittlenient can easily occur. Hydrogen 

embrittlenient is caused by the introduction of nascent atomic hydrogen into the steel microstructure. . 

Hydrogen embrittlenient can occur during a plating process or exposure to an acidic agent. The only 

known method to remove the hydrogen is by baking the part/component at 325 - 375 OF for 12-23 hours. If 

and when accidental exposure occurs, there are no known non-destructive methods for determining if 

hydrogen was introduced. The presence of hydrogen in steel promotes a significant loss of ductility and 

strength, which can lead to sudden brittle failures well after hydrogen exposure (refs 3,15) 

NEUTRAL: Neutral solutions are considered by far the safest to use on aircraft structures. However, a 

slight deviation in formulation by manufacturers may cause a neutral stripper to be slightly acidic. For 

example (ref I I), a solution ofpH 5.7 will cause hydrogenembrittlement on AIS1 4340 steel. One should 

also consider that the stability of a given chemical stripper. The pH of a particular solution may change 

with time through evaporation, or when exposed to other chemicals and/or materials. 

One the most important factors in evaluating a potential chemical is exposure or dwell time, 

particularly in the case of ingress into aircraft structures. An argument often used when potential damage is 

observed with new EA chemicals is that standard test results show that it is no worse than methylene 

chloride. However, the question is raised as to what dwell time is appropriate in comparative tests. For 

example. if pure benzyl alcohol is left to evaporate in an open laboratory pan, it will still be there after 12 

months. The same amount of methylene chloride completely evaporates within 7days. 
Thus to assess the potential damage associated with chemical ingress into aircraft structures, the 

fact that EA strippers will reside and act on aircraft materials for a much longer time horizon should be 

taken into account. The risk of ingress occurring is also impacted by the longer application times required 

with the new EA chemicals. The greater potential for ingress through longer contact times suggests that the 

risk of damage may be underestimated. 

Conclusions/ Future Work 

Dry stripping with starch-based media should be considered the safest alternative to methylene 

chloride, now and for the future. The current popularity of EA chemical strippers does not imply that they 

can be used without undue risk. And with the increasing use of advanced composite materials on newer 

aircraft, the concerns regarding chemical stripping effects on aircraft structures uill be even greater. 

New starch-based media types are currently under development at ADM that will eventually offer 

a wider variety of media products with differing characteristics and benefits. 

ADM will continue to work closely with equipment manufacturers and the aerospace community 

to promote and enhance the starch dry stripping process. 

ADM is actively working with environmental agencies and different industries to initiate an 

environmentally responsible media leaseirecycling program supporting customers spent media 

disposal needs. 
FIGURE I NEW MEDIA FIGURE 2 TYPICAL PRODUCTlON MIX 

FIGURE 3 ALMEN STRIP AND HOLDER 

FIG 1 DEFLECTION WITH ENVIROSTRIP FIG.5 DEFLECTION WITH PLASTIC MEDIA 
0,0105 

P # 

t 

0' 

I 

---Envirostrip XL5 

- c)- - Envirostrip 

Type V PMB 

0 10 20 30 40 50 60 70 

Dwell Time (seconds) 

FIGURE 6 SATUR4TION CURVES FOR ENVIROSTRIP, XL AND PLASTIC MEDIA ( TYPE V) 

FIGURE 7 NOTE MECHANICAL 

DAMAGE AT ARROW 

FIGURE 8 ADHESIVE REMOVED WITH 

ENVIROSTRIP, NO DAMAGE 
REMOVAL OF ZIRCONIA THERMAL BARRIER COATINGS AND MCrAlY BOND COATINGS 

FROM TURBINE BLADES: A COMPARISON OF METHODS BASED ON CHEMICAL STRIPPING, 

WATER JET AND SALT BATH, 

A.Scrivani’.’, U. Bardi’. G. Ballerini’. D. Bonacchi’, M. Fantini’. R. Groppetti’, S. lanelli’, G. Rizzi‘ 

I. 

2. 

3. 

4. 

Universita di Firenze, Dipartimento di Chimica. Via Cavour 82, Firenzc. Italy 

Universita di Parma, Dipartimento di Ingegeneria Industriale, Viale delle Scienze. Parma, Italy 

Galvanica Parmense, Via Romagnoli 3, S.Polo di Torrilc, Parma, ltaly 

Turbocoating S.p.A., Via Volta 3, Rubbiano, Panna, Italy 

Abstract 

In the aerospace field as well as in field of stationary gas turbines, thermal spray coatings arc gaining 

considerable importance for the improvement the properties of Nickel-super-alloys materials surface. Thermal 

spray coatings are commonly used as antioxidation materials (mainly MCrAlY alloys) and as thermal barrier 

coatings (mainly Yttria partially stabilised Zirconia) and are applied on Nickel super-alloys (as for instance 

different kinds of Inconel). Coating removal is an important aspect in the production of these devices. Removal 

(or “decoating” or “stripping”) is needed for the production of new components as well as for the reconditioning 

of ”in service” components. The present paper is dedicated to the a comparison of different stripping methods 

and to the characterisation of the blades surface after removal of thermal spray coatings both of Zirconia and of 

MCrAIY. 

The results reported here show that chemical stripping is particularly suitable for MCrAIY coating 

removal and does not affect the substrate. Water jet stripping can successfully be used for Zirconia-MCrAlY 

system removal although care is needed to avoid substrate damage. Salt bath technologies have been found to be 

effective for TBC removal but not for MCrAlY removal. 

Introduction 

Coating technologies are rapidly becoming a fundamental method in improving materials properties. In 

particular, thermal spray technologies are an effective and versatile method used to obtain coatings of different 

thickness with a good cost-quality ratio in the aerospace field as well as the in power generation sector 

(stationary gas turbines). In these areas, the surface proprieties of Nickel-super-alloy materials can be improved 

by means of antioxidation materials, such as MCrAlY (where M means Ni, Co or a combination of both), and 

thermal barrier coating materials, such as Y ttria partially stabilized Zirconia (YPSZ). MCrAlY coating are used 

to improve the resistance of the component to aggressive media at high temperature (900- 1 OOOOC) while low 

thermal conductivity of Zirconia coatings decrease the in-service temperature of thc component [Rickcrby, 

19911. The system MCrAlY + Zirconia is normally called Thcrmal Barrier Coating (TBC), where the MCrAlY 

layer acts as a bonding layer between the Zirconia coating and the substrate and is normally termed “bond coat”. 

MCrAlY coatings are normally manufactured using thermal spray technologies such as Vacuum Plasma Spray, 

Air Plasma Spray, High Velocity Oxygen Fuel (HVOF) depending on the specified porosity and oxides content. 

Zirconia coatings are almost always produced by Air Plasma Spray [Pawlowski, 19951. 

In the aerospace and power generation sectors technologies of coating removal are very important. 

These technologies, called also “decoating” and “stripping”, are used to recycle unsuccessfully coated parts and 

more often for reconditioning usured parts after thcir functional service. Stripping is used to remove darnagcd “in 

service” coatings, then, if necessary, the component can be repaired and finally rc-coated with new fresh 

coatings. 

The main characteristic of the stripping procedure is the guarantee of the complete removal of the 

coating without damaging the substrate. Stripping must not cause corrosion or roughening of the substrate 

surface and it must ensure a minimum dimensional change of its geometrical characteristics. Stripping of 

ceramic and MCrAlY layers remains a delicate problem in industrial production, for which the “perfect” solution 

has not been found yet. The aim of the present work is to discuss and compare three different stripping 

techniques: chemical stripping salt bath stripping and water jet stripping, to remove both MCrAlY and YPSZ. 

Experimental 

Stripping techriologies 

The stripping methodology presented is based on the combination of different techniques. usually in two 

subsequent steps: YPSZ removal and MCrAlY removal. The stripping of Y PSZ presents two principal problems: 
References: 

I. 

7 

-. 

3. 

4. 

5. 

6. 

9 

I. 

8 

9. 

10 

1 I. 

I?. 

13. 

14. 

15. 

Fontana M.G. Corrosion Engineering 31d Edition, McGraw - Hill, ISBN 0-07-021463-8. 1986, 

556 pp. 

Foster T. Oestreich J., Paint removal using wheat starch blast media, Defence Research 

Establishment Pacific FMO Victoria, BC. Canada, 1993. AGARD Report 791 

Jones D.A., Principles and Prevention of Corrosion, Prentice Hall, ISBN 0- 13-359993-0. 1996. 

~334 -346. 

Koutlakis G...LeBlanc P. Monette D., New Developments in starch based abrasive media an 

overview of research and development activities at Archer Daniels Midland, ADM Ogilvie, I998 

DoD/ Industry Aerospace coating conference, Batelle 

Lott R., and Pauli.R., Dry Stripping with wheat starch, Beech Aircraft, 1992. DoD,industry 

Advanced Coating removal conference, Batelle. 

Meguid SA.. Effect of partial-coverage upon the fatigue fracture behavior of peened components, 

Fatigue Fracture Engineering Material Structures, Vol 14 No 15. Fatigue of Engineering materials 

Ltd. 8756-758X. 1991, pp 515-530 

Miller R.E Final Report for the Wheat Starch Media Blast Removal of room temperature 

Vulcanized RTU Silicone rubber adhesive from the Space Shuttle Orbiter Surfaces. Northrop 

Grumman. 1998. 

Monette D, Envirostrip Plus Wheat Starch Dry Stripping Media, Archer Daniel Midland, 

DoD'lndustry Aerospace Coatings Conference. 1999 

Monette D. and Oestreich J., New Developments in Starch media applications and coating 

removal effects on various aerospace materials. CAE Electronics, 1996, DoD 'Industry Aerospace 

Coatings Conference., Batelle 

Monette D., The Environmental advantages of selective stripping, CAE Electronics, 1995, 

Aerospace Hazardous Materials Management Conference, GE Aircraft engines. 

NASA (National Aeronautics and Space Administration) Joint EPA/NASA/USAF Interagency 

Depainting Study. Final Report, George C. Marshall Space Flight Center, Dec 1999 

Pauli R.. Alternative Processes to Methylene Chloride Chemical strippers, A Review of Progress 

to date, Pauli &Griffin Company, 1995 AerospaceiAirline plating and Metal Finishing Forum & 

Exposition, Anierican Electroplaters and Surface Finishers Society. 

Tracy D., and Nakahara S., Depaint Activities at Northrop's B-2 Division, Northrop Aircraft, I994 

DoD Industry Advanced Coating Removal Conference. Batelle 

WHO (World Health Organization). 1984 Methylene Chloride Environmental Health Criteria 32. 

Published under the joint sponsorship of the United Nations Environment Programme, the 

International Labour Organization, and the World Health Organization, Geneva. 55 pp 

Wulpi D.J., Understanding How Components Fail, American Society for Metals, ISBN 0-871 70- 

189-9, 1985. PP261. 
REMOVAL OF ZIRCONIA THERMAL BARRIER COATINGS AYD MCrAlY BOND COATINGS 

FROM TURBINE BLADES: .4 COMPARISON OF METHODS BASED ON CHEMICAL STRIPPING, 

WATER JET AYD S.4LT BATH. 

AScrivani’.’, U. Bardi’, G. Ballerini‘, D. Bonacchi’, M. Fantini?. R. Croppetti’, S. Ianelli’, G. Rizzi‘ 

I. 

2. 

3. 

4. 

Universita di Firenze, Dipai-timento di Chimica, Via Cavour 82, Firenze. Italy 

Universith di Parma, Dipariiniento di lngegeneria Intlustriale. Viale delle Scienze, Parma, Italy 

Galvanica Parniense. Via Roniagnoli 3, S.Polo di Torrile, Parma. Italy 

Turbocoating S.p.A., Via Volta 3, Rubbiano, Parnia, ltaly 

Abstract 

In the aerospace field as well as in field of stationary gas turbines. thermal spray coatings are gaining 

coiisidenble iiiiportance for the improvement the properties of N ickel-super-alloys materials surface. Thermal 

spray coatings are corninonly used as antioxitlation materials (mainly MCrAlY alloys) and as Lherinal barrier 

coatings (mainly Yttria partially stabilised Zirconia) and are applied on Nickel super-alloys (as for instance 

different kinds of Inconel). C‘oating removal is an importanl aspect in the production of these devices. Renioval 

(or “decoating” or “stripping”) is needed for the production of new components as well as for the reconditioning 

of “in sewice“ components. The present paper is dedicated to the a comparison of different stripping rneihods 

and to the cliaracterisat ion of the blades surface after removal of thermal spray coatings both of Zirconia and of 

MCrAIY. 

The results reported here show that chemical stripping is particularly suitable for MCrAlY coating 

removal and does not arfect the substrate. Water jct stripping can successfully bc used for Zirconia-MCrAIY 

system removal although care is needed to avoid substrate daiiiage. Salt bath technologies have been found to be 

effective for TBC removal bur not Ibr MCr,41Y renioval. 

Introduction 

Coating technologies are rapidly beconiing a fundaniental method in improving niaterials properties. In 

particular, thermal spray technologies are an effective and versatile method used to obtain coatings of different 

thickness with a good cost-quality ratio in the aerospace field as well as the in power generation sector 

(stationary gas turbines). In these areas. the surface proprieties of Nickel-super-alloy materials can be improved 

by ineans of antioxidation materials. such as MCrAIY (where M means Ni. Co or a cornbination of both), antl 

lherinal barrier coating materials, such as Yttria partially stahilized Zirconia (YPSZ). MCrAlY coating are us& 

to improve the resistance of the component to aggressive media at high temperature (900- l000OC) while low 

thermal conductivity of Zirconia coatings decrease the in-service temperature of the component [Rickerby. 

19911. The system MCr41Y i- Zirconia is normally called Thernial Barrier Coating (TBC). where the MCrAIY 

layer acts as a bonding layer between the Zirconia coating and the substrate and is normally terinetl “bond coat”. 

MCrAlY coatings are nonnally manufactured using thermal spray technologies such as Vacuum Plasma Spray, 

Air Plasma Spray, High Velocity Oxygen Fuel (HVOF) tlepending on the specified porosity and oxides content. 

Zirconia coatings are almost always produced by Air Plasma Spray [Pawlowski, 19951. 

In the aerospace and power generation sectors technologies of coating removal are very importanl. 

These technologies, called also “decoating” and “stripping”, are used to recycle ~msuccessfully coated parts and 

more often for reconditioning usuretl parts alter their functional service. Stripping is used to reniove damaged “in 

service” coatings, then, if necessary, the component can bs repaired and finally re-coated with new fresh 

coatings. 

The main characteristic of’ the stripping procedure is the guarantee of- the coinplete removal of the 

coating without darnaging the substrate. Stripping must not cause corrosion or roughening of the substrate 

surface and it must ensure a minimum dimensional change of its geometrical characteristics. Stripping of 

ceramic and MCrAlY layers remains a delicate problem in industrial production, for which the “perfect” solution 

has not been found yei. The aim of the present work is to discuss and compare three different stripping 

teclmiques: chemical stripping salt bath strippirig antl water jet stripping, to reniovc both MCrAlY and YPSZ. 

E xperirnen tal 

The stripping methodology presented is based on the combination of different techniques, usually in two 

subsequent steps: YPSZ removal and MCrAlY removal. The stripping of YPSZ presents two principal problems: 
the YPSZ layer usually does not cover uniformly the surface of the sample, lor example oiily sonic parts of gas 

turbine hlades are covered; the layer is usured and its thickness is not the same over the covered sample. 

The stripping technologies analysed in this paper are the following: - chcmical stripping performed by immersion in hydrochloric acid in various conditions of temperature 

and acidic concentration (proprietary method by Turbocoating SpA 1 Galvanica Parmense) 

molten salt stripping (Kastech Electrolytic methods by Kolene Corp.) 

standard high pressure waterhbrasive jet stripping (proprietary methods by CREAS srl J 

- 

- 

The samples used here are parts of gas turbine components that have been coated by thernial spray. Different 

kinds of base materials have been used: Ni based super alloy in form of traditional casting and single crystal: all 

these materials contains dso elements as Co, W and Mo. The coatings were manufactured as follows: 

NiCrAlY alloy coatings of thickness in the range of 300-400 pm were deposited by Vaciiuni Plasma Spray 

and diffused at temperature of about 1 100°C in order to obtain a nietallurgical bonding between the coating 

and the substrate due 10 the migration of atoms at the interface 

8% Yttria Partially stahilizetl Zirconia deposited by Air Plasma Spray after dilTusion heat treatment. The 

Zirconia coating thickness was 500-700 pm. 

Figure I shows an oplical macrograph of the typical niicrostructure of the considered coating. 

Fig. 1 Typical microstructrire olTBC: system 

Annlysis methodologies 

Two types of analysis have been performed in order to investigate the roughnsss and the composition of 

the superficial layer of the stripped materials. The surface composition has been investigated with X-ray 

Photoelcctron Spectroscopy (XPS). The measurements have been carried out using a standard UHV XPS 

spectrometer, conveniiond AI KU and Mg Ka sources and a hemispherical analyser equipped with :I single 

channel electron multiplier. AH Ihe XPS spectra reported in the article are normalized to the value of' the most 

intense transition, in this case the 2p,,? transition of Ni. 

Roughness measurements have been performed hy means of a Three-Dimensional Digital Stylus 

Profilometer (5DSP). and an off-line analysis module, that receives digitised surface data from the acquisition 

module and applies a series of data processing techniques to provide information and evaluate parameters to 

characterise surface properties. The 3D parameters obtainable by this method are based on thee-dimensional 

extensions of 2D parameters defined in the IS0 4387 and DIN 4776 stantlards [Bracnli, 19991. The considered 

amplitude parameters have the following syinbols and meaning: 

S, : Arithmetic mean deviation 

S, : Root mean square deviation 

S, : Ten point heighl 

For metallographic investigation a metallographic microscopy (Zeiss Axiovert 1 OOA) with an image analyser 

based on grey contrast has been used. 
Results and discussion 

ParametedSample 2h inmiersion 4h iminersion 5h iminersion 711 immersion 

s, [PI 1.34 I .32 1.32 1.52 

[P’I 1.13 1.12 1 .O? 1.22 

. S? [WI 13.72 16.35 12.10 1 s.27 

Eflecrs of stripping metho& 

Complete coated turbine blades have been treated by the different stripping procedures considered here. 

After stripping. samples for analysis have been cut from the component and prepared for examination of both the 

surface and the cross section. For the cross section analysis the samples have been infiltrated and mounted with 

epoxidic resin and polished. In addition. the root of the blade produced with the single crystal Ni-Alloy material 

has been submitted to a cycle of 7 hour immersion in hydrochloric acid without any protection. For each hour, 

roughness has been determined by means of a 3-dimensional stylus micro-topography surface analysis system 

and metallographic analysis have been carried out. 

The sample labelled as “SB” has been stripped with molten salt to remove only the YPSZ coating; the 

sample labelled as “WJ” has been strippzd with water jet, to reiiiove both YPSZ and MCrAIY; the sample 

labelled as ”HA” has been stripped with sand blasting and then with hydrochloric acid, to remove both YPSZ antl 

MCrAlY. 

Since chemical stripping has been found to be unable to remove !he ceramic top coat. tests with this 

method have been performed after removal of the Zirconia layer by sand blasting.. In any case, the blasting 

operation before stripping should always performed in order to activate and clean the surfxe from possible 

pollution (grease. oil, etc.) that could stop the attack. Furthermore the acid attack is performed in order to have a 

“self-limiting” reaction by the use of a suitable inhibitor that reacts with the elements of the NiC‘rAIY coating 

forming a passive black layer that tcnd to stop the reaction and that should be rzniovzd by blasting to allow tlid 

progessing of stripping. We found that by using this procedure it is possible to avoid the attack to the substrate 

material. 

Kolme Kastech Electrolytic solution has been trailed on the blades sections coated both with NiCrAlY 

and YPSZ coating. Upon reinoval from the molten salt, the components have been immediately ambient water 

quenched and rinsed to complete the cleaning cycle. 

Literature shows the capability of the water jet technology in cutting, drilling or machining, while 

stripping with pure high-pressure water jet seems to be competitive and able to solve some environmental 

problem that are related to acid use [Mahrouki]. Water jet stripping was found to remove both the NiCrAIY layer 

and the Zirconia. 

In order to understand the el‘fects of acid attack on the substrate surface, a test has been carried out by 

immersing these uncoated surfaces in the acid solution for different numbcrs of hours. Single crystal material has 

been chosen for the test. These surfaces have been analysed by metallurgical microscopy to determine the 

presence of strtictural defects or cracks antl by 31) Stylus Profilometer lo in order to determine the roughness 

(this parameter is very iniportant for the coupling with the turbine rotor). The following table shows that no 

substantial increase in roughness takes place for extended exposures. 

iloric acid - optical image 
I 

Fly 3 lmcodtcd wrl.icc 'ifier 7 h immcrcion in hydrochloric acid opiical image 

The inicrographies (Fig. 2 and 3) show that no structural damage exists has been noted. We conclude 

that acid stripping has no substantial effect on the slructwe of the substrate. 

XPS provides a direct analysis of the surface composition with a depth resolution of a few nanoineters 

and permits therelhre to vericy the coating reinoval without special treatments of the samples. Since c'o is not 

present in the coaling but only in the substrate, its detection by XPS can be considered as the demonsti-ation of 

the complete ciecoating having been achieved. The main results of the XPS analysis are reported in iigures 4 and 

5. Figure 4 sholvs thc spectra of the three samples for the different stripping procedures. For the SB (salt bath) 

sample the superficial layer of this sample presents no traces 01' YPSZ coating. We observe only nickel. in part 

present as oxide, in the outelmost surface, indicating that the electrochemical treatment has leached out all the 

othcr metallic elenients in the bond coating for a depth of several nanomelers. 

The second spectrum is related to the sample HA (acid bath) and the third spectrum is related to the 

watcr jet treated sainplc (wfj. In both cases. XI3 shows the presence of Nickel, Chromium and Cobalt. As 

iiientioned earlier on, the presence of cobalt indicates that both methods have completely renioved the coating. 

WJ 

Ni 

* = Auger Line 

I I I I I I 

1000 900 800 700 600 500 

Binding Energy eV 

Figurz 4: XI'S normalized spectra of the tree stripped simples made with AI Ka transition. The spectra are 

normalized to the most intense line. 

The Auger lines of Nickel hide pnrliolly the photoelectron lines of Cobalt. To be sure of the presence of Cobalt in 

the samples a XPS spectrum niatle with the Ka of Mg hiis been mode. and is shown in figure 5. where the ?-pi,.z 

and the 2~):~ lines of Cobal~ are well shown. 
Ni 

= Auger Line 

I I I , L, 

900 800 700 600 500 

Binding Energy eV 

Figure 5: XPS normalized spectra ofthe HA stripped sample made with Mg Kcr transition. The spectniin is 

normalized to the most intense line. 

Figure 6 shows the sample after trealment by hydrochloric acid. Confirming the XPS results, no coating 

is presznt on the surface. The same consideration holds the water jet stripped sample shown in figure 7. Figure X 

sliows the sample treated by molten salt. Here it is possible to observe how the Zirconia coating has been 

completely removed while there remains the layer of NiCrAIY coating. On its surface it is possible to note a 

layer probably oroxides. Again. this result confilms the XPS data. 

Fig. 6 Sample stripped by hydrochloric acid 
Fig. 7 Sample stripped by water jet 

Fig. 8 Sainplc stripped by molten salt 

Conelusinn 

The rcsults show that chcniical stripping is particularly suitable l'or MC'rAIY coating removal and docs 

not affect the substrate material. Water jet stripping can successfully be used for Zirconia-MCrAIY system 

removal and it seeins 10 be the only one able to Iernc~e both the Zirconia and MCrAlY layers; although care is 

needed to avoid substrate daniage. Molten salt methods turned out to be suitable for the removal of the Zirconia 

coating. but the stripping of the bond coat remains diflicull and further studies will be necessary to determine the 

possibility of removing it. 

Acknowledgenients 

Renato C'ottica of C'REAS srl (Turin, Italy) for their contribute to the development of the stripping procedures. 

The authors are grateful to Mr. (iordon Palmer of Kolene Corp. (Detroit. Michigan, USA) and Mr. 

References 

Rracali P.. Ciroppetti R., Scrivani A,; On a micro-topogi-aphic three- dimensional acquisition and analysis system 

for engineering surface characterisation, Proc. AITEMY9. Brescia, Italy, 1999 

Mabrouki T.. Koissi T., Cornier A,: Numerical sirnulation and experimental study of the interaction between a 

pure high velocity and targets: contribution to inyesrigate he decoating process, Wear 239 [2) (2000) pp. 260- 

273 

Pawlowski, L.; The science and engineering of thermal spray coatings, Wiley & Sons, Chichester. 1095 

Rickerby D.S.; Matthew A,, Advanced surl-xe coatings: a handbook of surface engineering, Hackie & Son Ltd. 

London. I99 I 
-xx I 

Fig. 7 Sample stripped by water jet 

? 

Fig. 8 Sample stripped by molten salt 

Conclusion 

The results show that chemical stripping is particularly suitable for MCrAlY coating removal and does 

not affect the substrate material. Water jet stripping can successfully be used tor Zirconia-MCrAIY system 

removal and it seems to be the only one able to remove both the Zirconia and MCrAlY layers: although care is 

needed to avoid substrate damage. Molten salt methods turned out to be suitable for the removal of the Zirconia 

coating, but the stripping of the bond coat remains difficult and further studies will be necessary to determine the 

possibility of removing it. 

Acknowledgements 

Renato Cottica of CREAS srl (Turin, Italy) for their contribute to the development of the stripping procedures. 

The authors are grateful to Mr. Gordon Palmer of Kolene Corp. (Detroit, Michigan. USA) and Mr. 

References 

Bracali P., Groppetti R.. Scrivani A.: On a micro-topographic three- dimensional acquisition and analysis system 

for engineering surface characterisation. Proc. AITEM99, Brescia, Italy, 199’) 

Mabrouki T.. Raissi T., Cornier A.; Numerical simulation and experimental study of the interaction between a 

pure high velocity and targets: contribution to investigate thc decoating process, Wear 239 (2) (2000) pp. 260- 

273 

Pawlowski, L.; The science and engineering of thermal spray coatings, Wiley & Sons. Chichester, 1995 

Rickerby D.S.; Matthews A., Advanced surfacc coatings: a handbook of surface engineering, Blackie & Son Ltd. 

London. 199 I 
Joint EPA/NASA/USAF Interagency Depainting Study 

Marceia Clark-lngram 

National Aeronautics and Space Administration 

NASA Operational Environment Team 

ED36tMSFC 

George C. Marshall Space Flight Center, AL ,35812 

inarccia.a.clark.ingram(dimsfc.nasa.go~~ 

256-544-6229 

INTRODUCTION 

are drivers for the implementation of environmentally compliant methodologies in the manufacture of aerospace 

hardwarc. In 1995. the Environmental Protection Agency (EPA) promulgated the NESHAP tor the Aerospace 

Manufacture and Rework (.4erospace NESHAP) industry. Affected facilities were to be in compliance by Septcinber 

1998. Several aerospace manufacturing operations are regulated within the Aerospace NESHAP including 

Depainting operations. 

Environmental regulations such as National Emission Standards for Hazardous Air Pollutants (NESHAPs) 

Thc National Aeronautics and Spacc Administration (NASA), EPA, and United States Air Force (USAF) 

combined resources to evaluate the performance of nine (9) alternative depainting processes. The seven alternative 

dcpainting processes wcrc: Chemical stripping (non- methylene chloride), Carbon Dioxide Blasting, Xcnon 

Flashlamp, Carbon Dioxide Laser Stripping, Plastic Media Blasting, Sodium Bicarbonate Wet Stripping, Waterjet 

Blasting and Wheat Starch Blasting. An epoxy primer and polyurethane top coat system was applied to 1024-13 

clad and non-clad aluminum test specimens. 

Approximately 200 test specimens were evaluated in this study. Each coupon was subjected to three (3). 

four (4). or five (5) complete depainting cycles. This paper discusses the conclusions from the study including the 

tcst protocol. test parameters, and achievable strip rates for the alternative depainting processes. Test data includes 

ininicrsion corrosion testing, sandwich corrosion testing and hydrogen embrittlement testing for the non-methylene 

chloride chemical strippers. Additionally, the cumulative effect of the alternative depainting processes on the 

metallurgical integrity of the test substrate is addressed with the results from tensile and fatigue evaluations. 

REGULATORY BACKGROUND 

Chloride is listed as a Hazardous Air Pollutant (HAP) by the EPA. This chemical is also a suspected carcinogen. 

Methylene Chloride was traditionally utilized for chemical stripping of coating systems. Methylene 

The National Emission Standards for Hazardous Air Pollutants for Aerospace Manufacturing and Rework 

Facilities (Aerospace NESHAP) regulates depainting operations. The Aerospace NESHAP limits the amount of 

methylene chloride for coating removal operation in affected facilities. The limit is 16 gallon/craft/year for 

commercial operations and 50 gallonsi'craftlyear for military operations. 

The initial Aerospace NESHAP was promulgated in September 1995 however subsequent versions exist. 

The first substantive compliance date tor existing sources is September 1998. The Occupational Safety and Health 

Administration (OSHA) established stringent Permissible Exposure Limits (PEL) that were effective in April 1997. 

OBJECTIVE OF STUDY 

ISOi'SAE MA4872, Revision # 5 "Paint Stripping of Aircraft - Evaluation of Materials and Processes". 

Additionally, three (3) to five (5) cycles of panel preparation and depainting were performed for each alternative 

dcpainting methodology to determine cumulative metallurgical effects of the alternative processes on the substrate 

The nine (9) alternative depainting processes are: 

The overall objective of the study was to evaluate nine (9) alternative depainting methodologies per 

1 Chemical Stripping (non-methylene chloride) 

1 Carbon Dioxide Blasting (ColdjetT" ) 

3 Carbon Dioxide Blasting (TOMCO?) 
4 

5 Laser Stripping 

6 Plastic Media Blasting 

7 Sodium Bicarbonate Wet Stripping 

8 Water Stripping 

9 Wheat Starch Blasting 

Xenon Lampicarbon Dioxide Blasting ( FlashjetTh') 

SCOPE OF STUDY 

The specimens for evaluation were fabricated from 2024 -T3 clad and non-clad aluminum. The specimen 

thicknesses were 16, 32, 51, and 64 mil. The paint system utilized for the first depainting cycle contained a MIL-P23377F , Type 1, Class 2 primer and a MIL 4-83286B urethane topcoat. The primer remained the same for all 

subsequent depainting cycles. The vendor discontinued the availability of the MIL-C-83286B urethane topcoat after 

the first depainting cycle duc to the high Volatile Organic Content (VOC) ofthe material. The MIL-C-85285B 

topcoat was implemented for subsequent depainting cycles. This material contained a high solids, low VOC 

formulation. 

SPECIMEN PROCESSING & DEPAINTING 

The depainting specimens were processed per the following 9 steps: 

I. 

2. 

3. 

4. 

5. 

6. 

7. 

X. 

9. 

Coating Application of Paint System 

Coating thickness measureinents 

Environmental Aging 

Depainting (Coating Removal) 

Measurements: substrate thickness, surface roughness 

Specimen Cleaning: Water Break Free Surface 

Chromate Conversion (Iridite 14-2) 

Measurements: substrate thickness and weight. surface roughness 

Repeat for next cycle of specimen processing 

SPECIMEN CLEANING 

The cleaning of the test specimens (per Step 6 above) encompassed the following: 

Methyl Ethyl Ketone (MEK) handwipe 

Perchlorocthylenc Vapor Degreasing for IO minutes 

Immersion in Turco 42 15 for 35 minutes 

Hot Water Deionized Rinse for 5 minutes 

Immersion in Turco Smut-Go #I for I1 minutes 

Cold Water Deionized Rinse for 5 minutes 

Water Break Free Test with Deionized Water. 

ENVIRONMENTAL AGING OF SPECIMENS 

The specimens were aged according to ISOiSAE MA4X72. The specimen aging in cycle one required 

approximately 90 days. The installation of liquid nitrogen lines accelerated the aging cycle. The environmental 

aging consumed 35 - 50 days for thc remaining cycles. The specimens were thermally cycled for 800 times. The 

environmental aging cycle is described below. 

Precondition : 12 hours C& 120 "F and 95% RH 

Hold at -65 "F for 1 hour 

Thermally cycle from -65 "F to I60 "F for 400x 

Return chamber to ambient temperature. 

Repeat steps I - 3. 

MATERIAL EVALUATION TESTING 

Material evaluation testing was performed on the test specimens. Sandwich corrosion testing, immersion 

corrosion testing and hydrogen embrittlement testing was performed on the non-methylene chloride chemical 

strippers. Baseline surface roughness measurements, post-cleaning surface roughness measurements. and poststripping surface roughness measurements were taken for each test specimens. Crack Detectability measurements 
were performed on all Plastic Media Blast test specimens and on non-clad test specimens for Sodium Bicarbonate 

Wet Stripping, High-pressure Water Blasting, and Wheat Starch Blasting.. Tcnsile testing was performed on nonclad specimens that were depainted with the Xenon FlashlampKO2 process, and cladinon-clad specimens depainted 

with the Plastic Media Blast process. Fatigue testing was performed on non-clad specimens that were depainted 

with the following processes: Xenon Flashlamp Cor, Plastic Media Blasting, High Pressure Watcr Blasting. and 

Whcat Starch Blasting. 

C‘/icviicaf Strippers 

Methylene Chloride Baseline for Alkaline 

Neutral : Cee Bee K-256 

Alkaline Keutral Candidates 

Methylene Chloride Baseline Acid : 

Cce Bee A-202 

DEPAINTING STRIP RATES & OPERATING PARAMETERS 

alternative depainting methodologies. 

This section of the technical paper discusses the strip rates that were achieved during the evaluation of the 

’4 verrip D,td Timr 

5.0 minutes 

3.5 hours 

5.0 minutes 

I. Chemical Striming 

A total of five (5) depainting cycles were completed with non-methylene chloride chemical strippers. The 

non-nicthylene chloride strippers contained acid and alkaline/neutral formulations. The specimen dimensions were 

I?’ s 12” with a 63 mil thickness. Initially. low strip rates were obtained in the I“ depainting cycle prior to process 

optimization. Fortunately. a site visit to Raytheon in Selma, Alabama provided guidance on chemical stripping 

optimization. 

The following operating conditions were recommended by Raytheon and implemented during the four (4) 

remaining depainting cycles for evaluation of thc non-mcthylcne chloride containing chemical strippers: 

Maintain environmcnt at an RH of 34% and a temperature between 80 and 86 OF 

Apply fine mist of stripper over panel. 

Apply heavier mist 30 minutes later. 

Check at 7 hour intervals. 

When coating is released, brush panel and reapply stripper as before. 

Initially, 40 candidate strippers were evaluated for stripping efficiency. A down-selection process yielded the 

eight (8) chemical strippers listed in Table 1. 

Turco 68 13-E PR-2002 

The aforementioned chemical strippers were highly effective and removed l0Oo/~ of the topcoat and I000/0 

ctfthc printer from the specimens. The average “time to strip“ for all eight (8) non-methylene chemical strippers is 

provided in Tablc 2. Additionally, two (2) methylene chloride containing strippers were used as controls during the 

evaluation. 

Acid Candidates 

3. I hours I 
2. Carbon Dioxide Blasting 

COLDJETT" Model 62-250 and the TOMCO? DI-250. The COLDJETTL' system caused significant deformation on 

16 mil specimens. Surface damage was evident on some of the 64 inil specimens. The TOMCO? system was 

capable of soinc coating removal but the allowable pressurc was ineffective for efficient stripping. The C02 Blast 

systems were removed from thc study after complction ofthe I" depainting cycle. The CO? Blast systems were 

effective for cleaning of specimens versus coating removal. The operating parameters for the COLDJETTh' and thc 

TOMCO? systems are provided below. 

Two Carbon Dioxide (CO?) Blast systems wwc evaluatcd during this study. Thc two systems were the 

COLDJET T'l 

Nozzle: 5 in diameter 

Area Stripped : I2 in - 45.5 in ' 

Angle of Attack : 75" 

Stand-Off Distance: 5 in - 6in (16 mil non-clad) gL I" to 3" ( 64 mil non-clad) 

Media Flow Ratc: 350 Ibihr 

Pressure : I20 -300 psi 

Stripping Passes : 4 maximum 

Effectiveness: IO056 topcoat, 80% primer 

Substrate Dimensions 

(in.) 

TOMCO, System 

Angle of Attack: IO I' 

Stand-Off Distance: 1 in 

Pressure: 150 psi 

0 

Areahipped : 144 in' maximum 

Media Feed Rate : 200 - 400 Ib 

Nozzle : I .5 -in diameter (fan nozzle) 

Stripping Passes: I to 2 

Effectiveness: 4546 topcoat & 10% primer ( 144 in'), 10040 topcoat & 98% primer (36 in') 

Substrate Thickness Strip Rate 

(in.) (in.'/min) 

3. Xenon Flashlamp/ Carbon Dioxide (Flashiet) 

A total of three (3) depainting cycles were completed for the Xenon/ Flashlamp C02 coating removal 

system. The Boeing Company in St. Louis. MO, donated generous time and effort during the evaluation of this 

depainting system. 

The Flashjet system utilizes pulsed light and a C02 particle stream to remove thc coating from the 

substrate. Boeing chose to remove 100Y0 ofthe topcoat and 57-74OA ofthe primer. Many of the Boeing customers 

allow a portion of the primer to remain on the craft after depainting. Typically, six (6) to twenty-two (22) passes 

werc needed to achieve the desired coating removal. 

The study team regarded data from the jrd depainting cycle as representative of the capabilities of the 

Flashjet system. This data is provided in Table 3. 

The following operating parameters were utilized to achieve the aforementioned strip rates: 
Operating Parameters: 

Stand-off Distance: 2 to 3 inches 

Angle of Attack : 2 1 to 29" 

Media Flow Rate: 500 to 1000 lbihr 

input Prcssure to nozzle : 90 to I80 psi CO2 

Input Voltage : 1900 to 2300 Volts 

Repetition Ratc: 3 to 5 flashesisec 

Translational Velocity: 0.75 to I .4 inisec 

Substrate Dimensions Sequence 

(in.) 

12x 13 1 

12x 13 L 

7 

4. Carbon Dioxide Laser Stripping 

The first depainting cycle was performed by International Technical Associates of Santa Clara, California. A 50 

watt demonstration unit was utilized to remove the coating from the specimens. The second depainting cycle was 

performed by Silicon Alps of Santa Clara, California. A 2kW production unit was utilized. C02 lasers were used 

for coating removal during the first and second depainting cycles. General Lasertronics Corporation of Milpitas, 

California. perfomied the 3"' depainting cycle. A Neodium -doped Yttrium Aluminum Gamer laser was utilized 

during the 3"' depainting cycle. Proccssing anomalies at MSFC skewed the strip rates for the 3" depainting cycle. 

A total of three (3) depainting cycles were completed for the cvaluation of the CO? Laser Stripping process. 

Time to Strip Strip Rate 

10 min 6.0 

38 sec 47.4 

(in2/min) 

The strip rates for Laser Stripping are provided in Table 4. The stripping effectiveness is 100"/0 removal fbr 

topcoat and 99% removal for primer. .4n area of 60 in' was stripped during the first depainting cycle and an area of 

30in' was stripped during the second depainting cycle. 

Substrate Thickness Clad/ Non-Clad I Average Strip Rate 

The following operating parameters were utilized: 

Scan Ratc : IS Hz 

Pulse Width : 6 microseconds 

Laser Power: 50 W (Sequence 1 ), 2kW (Sequence 2) 

Maximum Energy: 5 Joulesipulse 

Stripping Fluence: 4.5 Joulesicm 

Footprint Size: 5.Smm x 5.5mm 

Stand-off Distance : I2 inches 

(inches) 

0.0 16 

0.0 16 

0.032 

0.05 I 

0.064 

5. Plastic Media Blast (PMB) 

A total of four (4) depainting cycles were conducted at MSFC for the evaluation of the Plastic Media Blast 

(PMB) process. A manual PMB system was used in the study. Strip rates from this system were not comparable to 

strip rates achieved by industry. Substrate thickness was 16, 32, 5 I and 64 mils. Clad and non-clad specimens were 

evaluated. Specimen dimensions were 12" x 12" and 22" x 22". The strip rates provided in Table 5 are an average 

of all four depainting cycles. One stripping pass removed I00"h of the primer and 8O04 of the topcoat. 

(in2/min) 

Non-clad 22.4 

clad 25.0 

clad 26.7 

Non-clad 26.4 

Yon-clad 22.0 

The following operating parameters were implemented to achieve the strip ratcs provided above: 
0 

0 

0 

Nozzle Diameters: 0.5 inches @ throat, 1 .O inch (5 exit 

Stand-off Distance: 9 inches to I2 inches 

Angle of Attack : 30°, 30” -45” (64mil) 

Mesh size: 20120 (SO%), 16/20 (20‘!b) 

Media Flow Rate: 250 ~ 500 1b:hour 

Pressure: 30 psi - 40 psi 

6. Sodium Bicarbonate Wet Striming 

A total of three (3) depainting cycles were conducted using manual and automated Sodium Bicarbonate 

Wet Stripping systems at the MSFC. The first cycle was performed manually and the remaining two cycles were 

perfonned with an automated system. Aquamiser and Carolina Equipment Company were the two manufacturers of 

the Bicarbonate of Soda System (BOSS) equipment. The substrate thickness of the clad test specimens was 16 mil 

and 32 mil. The substrate thicknesses of the non-clad test specimens were 5 1 mil and 64 mil. The specimen 

dimensions wcre 22” x 22”. 

The I6 mil specimens were removed from the study aftcr the first depainting cycle. The Sikorsky 

Company generously donated 10 clad specimens for the 3“’ depainting cycle. The data in Table 6 represents the 

strip rates that were obtained with the BOSS equipment. The coating removal efficiency for the 2’ld and 3“’ 

depainting cycles was 100% of the topcoat and 90% of the primer. 

The following operating parameters were implemented to achieve the strip rates in Table 6. : 

0 

0 

0 

Pressure : 14,000 psi 

0 

Nozzle : 7” fan nozzle 

Stand-off Distance : 2 inches 

.4ngle of Attack: 90 ” 

Media Feed Rate: 2 to 3 Ib/min 

Media Flow Rate: 3.2 gallons/minute 

Translational Velocity: 9 to 29 idsec 

7. 

technology. The clad specimens were donated by Sikorsky and were 16 and 32 mils in thickness. The substrate 

thickness of the non-clad specimens was 16, 5 I and 64 mils. The dimensions of the clad specimens were 22” x 22” 

and the dimensions of the non-clad specimens were 12” x 12”. 12’ x 13”, and 22” x 22”. Three depainting cycles 

were conducted on the non-clad specimens while one depainting cycle was conducted on the clad specimens. 

High Pressure Water Blast StripoinP 

A total ofthree (3) depainting cycles were conducted at MSFC utilizing the High Pressure Water Blast 

The stripping effectiveness of the High Pressure Water Blast technology removed 1000/6 of the topcoat and 

100°/o of the primer. The aforementioned stripping efficacy was achieved with one to threc stripping passes. The 

strip rates are provided in Table 7. 
Note: Sequence I for clad panels occurred concurrently with sequence 3 for non-clad panels. 

The operating parameters for the High Pressure Water Blast Stripping technology is as follows: 

Nozzle : Hammelmann Rotary Nozzle 

Rotational Velocity: 900 rpm 

Stand-off Distance: 2 inches 

Angle of Attack: 90" 

Water Flow Rate: 7- 1 1.5 galirnin 

Pressure: 20.000 - 30,000 psi 

Translational Velocity: 1.2 - 6 inisec 

Stripping Passes: 1-3 

Overlap: 0.5 - 1.75 in 

8. Wheat Starch Striming 

(30) specimens were stripped with the Wheat Starch technology. Generous time and support was donated by ADM 

Ogilvie and CAE Electronics (Montreal, Canada). Manual and semi-automated systems were utilized. The pure 

wheat starch media is used with this technology. The wheat starch can be recycled a maximum of20 times. This 

technology can be implemented on aluminum. composite and steel materials. The workpiecc is groundcd to prevent 

ignition of media dust. 

A total of three (3) depainting cycles were performed with the EnviroStrip Wheatstarch technology. Thirty 

The specimcns were a thickness of 16. 5 I and 64 mils. The strip rates provided in Table 8 yielded 100% 

removal ofthe topcoat and 99?0 rerno\.al of the pnrner with one pass. 

The following operating parameters provided the strip rates in Table 8: 

Manual Operating Parameters: - 

- Area Stripped : 1 I6 in' 

Nozzle : 0.5 inch double venturi 
- 

- 

- 

- Pressure : 20-30 psi 

Angle of Attack: 30 to 60 " 

Stand - Off Distance : 4 to X inchcs 

Media Flow Rate: 12 to IX Ibhin 

Automated Operating Parameters: 

Area Stripped : 204 in', 2 I6 in' 

- Nozzle: 4 inch flat nozzlc 

- Projection Anglc: 45" 

- Stand-Off Distance: 3 inches 

- Media Flow Rate: 12-18 Ibhnin 

- Pressure: 20-40 psi 

- Translational Velocity: 0.8-3.1 iniscc 

Baseline 

(microinches) Depainting Process 

Chemical Stripping I .6 

XenonIFlashlamp I .9 

CO? Laser 1.3 

Plastic Media Blast 2.5 

Sodium Bicarbonate w Water 1.8 

High Pressure Water 1.9 

Wheat Starch Blasting 1.3 

SURFACE ROUGHNESS 

microinches after 5 (five) depainting cycles. A Ciiddings gL Lewis profilometer and a Hominelwerkc TS00 

profilometer were used to determine the surface roughness of the specimens. Table 9 lists thc cumulative surface 

roughness measurements after the 3"' depainting cycles. 

The ISOiSAE M8472 standard requires that the cumulative surface roughness value not exceed I25 

Sequence 3 , After Cleaning 

(microinches) 

10.5 

15.1 

16.2 

*28.3 

*x.0 

16.8 

CONCLUSlON 

coating removal with the exception ofCO2 Blasting. Many factors should be taken into consideration when 

selecting an alternative depainting methodology. The factors arc as follows: 

The evaluation of the alternative depainting methodologies demonstrated that all processes are viable for 

Capital Costs 

Operating Costs 

Specialized Training 

Facility Space 

Manual vs. Automatic 

Easeofuse 

Strip Rates 

Compatibility with Existing Systems 

Waste Generation 

Substrate Characteristics 

Hardware Characteristics 

Paintiprimer System 

ACKNOWLEDGEMENTS 

MSFC for their commitment to technical excellence and the environment. 

Thanks to the EPA, AF, Technical Advisory Committee, Aerospace Industry partners and the team at 

REFERENCES 

Joint EPAINASAIAF Interagency Study - Final Report, December 1999 
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LOW-COST CERAMIC MATRIX COMPOSITES 

W. Kowbel 

MER Corporation 

7960 South Kolb Rd 

Tucson, AZ 85706 

I kowbel@;;mercorp.com I 520-574-1980 

C. Bruce, K.T. TSOU, and J.C. Withers 

MER Corporation 

Introduction 

Despite their unique properties, ceramic matrix compositematerials have found use in a very limited 

number of applications [ 11. Cunent applications include rocket motor parts, turbojet parts and 

thermal structures for space planes and other space probes. These applications are virtually priceinsensitive and are driven by the performance criteria. Numerous potential applications for 

continuous fiber ceramic matrix composites (CM C) have been identified including advanced heat 

engines, heat recovery equipment, burners and combustors, process equipment, waste incineration 

systems and separation and filtration equipment. However, for composites to sucessfully compete 

with other engmeeringmaterials, their cost must be substantially reduced. These costs are strongly 

influenced by lengthy composite processing technologies. It is expected that at least a 10 fold 

decrease in theCM C composite prices is needed to provide a significant penetration of commercial 

markets. 

The processing methods for the manufacture of CM C composites are limited. The most commn 

methods are: 

i) Chemical vapor infiltration (CVI), 

ii) Silicon melt impregnation and, 

iii) Polymer impregnation and pyrolysis. 

One major drawback of the isothermal CVI technique is that the infltration process has to be 

interrupted a number of times to remove the extanal coating, which would otherwise prevent a 

complete infltration. In summary, CVI offers a great flexibility to control the microstructure and 

resulting properties of CMC composites, but its application to low cost processing of CMC 

composites remains to be proven. 

G.E. [2] andNASA Lewis [3] havedeveloped CMC composite consistingof continuous Sic plus Si 

matrix produced by melt infiltration. These materials exhibit relatively good near net shape 

manufacturing but poor matrix purity (due to residual silicon). The scale-up capabilities of this 

process compared to the established isothermal CVI method have not yet been shown. Thus, direct 

comparison with the CVI process is impossible. Kaiser Ceramic Composites [4] fabricated ceramic 

matrix composite using a polymer impregnation and pyrolysis process. Prototypes of various 
structures such as gas deflection tubes, gas turbine combustors, turbine blades, fairing channels, duct 

sections and various engine parts weremadevia this process. Multiple impregnation and pyrolysis 

cycks arerequired to reduce theopen porosity down to 10%. The manufacturing costs are effected 

by the lenghy procasingand high cost of preeramicpolymers. In addition, low matrix purity and 

crystallinity sigpificantly limits the maximum continuous service temperature and adversely effect 

the through-thethickness thermal conductivity. A direct comparison with the well-established CVI 

technique is not yet available. 

Composite 

Type 

MER 

(C-C) 

ACROSS 

Materials 

Density Open Flexurrll Strain Tensi I e Tensile S hex KIC 

(g/c) Porosity Stmgth To Strength Strain to Strength MPam' ' 

( O/lJ ) MPa (ksi) Failure MPa (ksi) Failure MPa (ksi) 

I .65 8 350(5 1 ) 0.55 280(40) 0.3 12.31.8) 9 

1.75 8 120( 17) 0.2 105(15) 0.2 12.5 8 

(Yo) 

Carbon-carbon (C-C) composites were used as a substrate. Flat C-C pands (1 Om x 1 Ocm x 0.2an) 

were used One-step fabrication process described elsewhere [5] was used to produce the C-C 

composites. C-C composites were fabricated using PAN-based carbon fabric and a thermoset-based 

resins with active fillers. The C-C 

composites were converted into C-Sic and Sic-SIC composites via Chemical Vapor Readion (CVR) 

process. The CVR-Sic matrix was produced via Si0 gas reaction with the carbon matrix as 

described elsavhere [6]. 

A singe heat treatment up to 2500°C was employed. 

Evalu a ti on K3 h a racte ri z a ti on 

SEM was used to examine theuncmted and coated composite cross section. Flewral strength was 

performed using a 4 point bendmg test with a 40:l spmto-depth ratio. Tensile strength was 

obtained using do&ne shaped specimens. SEM was used to evaluate composite cross sections. 

Thermal difhsivity was measured with the laser flash method. 

Results and Discussion 

Low€os t C-C Commsi tes 

Conventional C-C composites suffer from excessive cost ($1000 - $1 0,OOOikg). leng hy processing 

time ( I - 6 months) and transverse matrix cracking. A onestep process (developed by MER [SI 

with a 1 day processingtime) can yield C-C composites exhibiting very good mechanical properties, 

Tabk 1. Very good tensile strength is obtained (280 MPa) combined with a nonkrittle behavior. 

Virtually no transverse cracking is observed, Figure 1. 

Table 1. Summary of Physical and Mechanical Properties of C-C Composites 
Figure 1. Cross-section of low-cost C-C composite. 

CVRSiC Fibers 

Figure 2 shows the single fiber tensile strength valua for single fibers extracted from T-300 1K 

8HS fabric. Good strength retention (about 1.5 GPa) was attained for about 90% CVR-Sic 

converted fibers. A 100% CVR-Sic converted fiber was obtained, but the tensile strength was 

diffcult to assess (increased stiffkess). 

4 

3.5 

3 

4 2.5 

n 

nt 

W 

52 

E 

3; 1.5 L 

1 

0.5 

0 

0 20 40 60 80 100 

Conversion (Oh) 

Figure 2. Single fiber strength versus SIC conversion. 

The tensile strength of these fibers needs to be assessed on the basis of their heat treatment history. 
The 1 .S GPa tensile strength corresponds to a heat treatment in excess of 1700oC. Figw 3 shows 

the corresponding SEM micrographs (95% SIC conversion). Minimum cracking is obselved at this 

conversion level It is worth mentioning that for this heat treatment temperature. Nicalon S type 

fiber would exhibit a similar strength. 

Figure 3. SEM Micrograph of 95% CVR-Sic. 

This new processing scheme for C-C composites offers a potential to revolutionize lowcost 

processing. In principle, the processingis suitable for both fabric and fiber-tow reinforcement. The 

process is polymer-based (very low cost matrix precursors) and involves a sin$e heat treatment. A 

combinationof these factors yields a process capable of producing high quality C-C composites, at 

a cost below $1 OOkg 

CVRSiC Compsites 

Figure 4 shows a SEM micrograph of CVR-SIC matrix following isothermal air oxidation at 800°C. 

The residual carbon coreof the carbon fibers was removed by oxidation. The CVR-SIC conversion 

is primarily confined to the matrix with limited reaction converting the graphite fiber to Sic. The 

CVR-process can be optimized to control the amount of the composite/mtrix conversion. The 

ability of the CVR process to primarily convert the carbon matrix results from markedly different 

conversion rates exhibited between the carbon fiber and matrix The higher porosity of the matrix 

and its activity results in a significantly higher conversion rate 
Figure 4. S EM of CVRC-Sic composite after oxihtion. 

Figure 5 shows the cross section of theC/CVR-SIC composite. No matrix delamination is observed. 

The CVR process has several significant advantages over Si-melt inatration, including 

i) Theability to produce purea-SiC matrix 

ii) Scaling-up capabilities 

iii)Gas phase reaction 

iv) Low cost 

v) Minimum volume change 

Figure 5. Cross section ofa C-Sic composite. 
CC'RS i C/CvR-S i C commsites 

Proper control of the CVRSiC conversion can lead to the formation of CVR-SiC/CVR-SIC 

composites. As the conversion process progesses, the carbon fibers become converted to CVRSIC, Figre 6. The conversion process can be controlled to obtain 100?4 overall conversion (both 

the carbon matrix and fibers are completely converted into CVR-Sic). 

Figure 6. S EM ofCVR SIC-SIC composite after oxidation 

Figure 7 shows across section of the CVR-SiC/CVR-SC corrposites (1000,'" Sic conversion). No 

matrix delaminat Ion is observed 

Figure 7. Cross section of a S iC-Sic composite. 
Interfacial Properties 

Theinterface between the fiber and matrix plays akey role in determining the properties of the 

ceramic matrixcomposite(CMC). Theslidingresistance OT shear strengh at the interface plays an 

important de in governing the rateof load transfer fi-om the fiber to the matrix If the fiber is 

bonded too well to the matrix, the load is carried into the matrix and brittle failure occurs. If the 

interface between the fiber and the matrix is weak, then the crack is deflected along the interface and 

fiber pull-out increases. Ifthe interfaceis tooweak,no load is tlansfemd and the composite 

becomes weak. For convmtional statsof-thsart Sic-Sic composites, intafacial coatmg such as 

graphite and boron nitride have been used. But these interfacial coatmg oxidize easily and cause 

additional problems. 

Figure 8 shows the fracture surface of a CVR-SiC/CVR-Sic composite. Good fiber pull out is 

observed combtned withno apparent damage to the fiber. Thus, theCVRprocess conditions, up to 

100% SIC conversion of the graphite fiber, can be adjusted to produce high quality SiC-Sic 

composites exhibiting good mechanical properties and lowcost. The key finding is that significant 

fiber pullout is observed at the 100% Sic conversion, Figure 8. This result represents a milestone 

in the area of SiC-Sic composite processing. Good fiber pull-out is observed with no interfacial 

coating. Thus. a 100% p-SiUp-Sic composite was produced exhibiting good mechanical properties. 

In addition, no damage is observed on the 100% CVR-SIC fiber, Figure 8, converted in-situ. 

Figure 8. Fracture surface of CVR-S iC/CVR-Sic 

Table I1 shows the properties of CVR-Sic composites as compared to CVI and PIP-based Sic 

composites. 
Table II. Properties of different composites. 

Utilities 

Laba 

B ur&n 

Tot2 Iwihout nrofiD 

The key properties for structural applications of C-Sic and SiC-SiC composites is the proportional 

limit (at least 20 MPa comparable or better than the state-of-the-art composites) and thermal 

conductivity (at least 80 W/mK compared to 10 W/mK for the CVI Sic-Sic composites). The 

enhanced thermal conductivity offers a significant potential in engine-related applications. 

$3.70 

$44.00 

$46.28 

S221.M 

Cost Analvsis 

Table 111 shows the cost analysis of the CVR-SiC/CVR-Sic composites. The cost of $200/kg is 

believed to be achievable at a moderate production rate This cost analysis underscores the great 

market potential of this technology. Stinton [7] performed a composite cost analysis of the CVISic matrix and estimated the composite cost at about $lO,OOO/kg. Thus, this novel CVR process 

has a potmtial for a 50 times reduction in the manufacturing cost of C-SC composites. This 

accomp lishmnt could provide for significant market penetrations. 

Table IIL Cost Analysis 

Raw Mataials 1 SI 18.80 

Supplies $8.80 

Condusions 

Lowcost C-C composites offer potential as a precursor to fabricate C-Sic and Sic-Sic composites 

at greatly reduced cost. The CVR process can be controlled to convert primily the carbon matrix 

leadng to the formation of C-Sic composites. Adjustment of theCVRprocess conditions results in 

goodmechanical properties of C-Sic. In addition, the CVR process can be adjusted to convert both 

the fiber and the matrix 
References 

1. J.W. Finley, “Applications of High Temperature Composites,” NASA CP 4552, (1993). 

2. G.S. Corman, “Properties Melt-Infiltrated SiCSiC Composites,” SAM PE International 

Svmposium, 39( 1997)23oO 

3. A. Schweda, “Properties of P1P-Derived Sic-SIC Composites,” SAM PE International 

Symposium, 39( 1997) I781 

4. M. Sin&, “Effect of Carbon Preform Pore Volume and Infltrants on the Composition of 

Reaction-Formed Silicon Carbide M aterials,” Journal of Materials Synthesis and Processing, 2 

W. Kowbel, V. CheIlappa & J.C. Withers, “Properties of One-Step Composits,” Carbon, 

34( 1996)8 19 

W. Kowbel, et al, “Properties of CVR-Derived SIC-SIC Composites,” Journal of Nuclear 

M at erials 2 1 7( 1995)2 

D. Stinton, “Cost Analysis of CVI Processing” M RS Proceedina, 65( 1999393 

(1994)117-123. 

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Rapid Fabrication of monolithic ceramic parts reinforced with Fibrous Monoliths for aerospace applications 

R. Vaidyanathan, J. Walish, J. L. Lonibardi, M.Fox, M. Rigali and M. Sutaria 

Advanced Ceramics Research, Inc., 3292 E. Hemisphere Loop, Tucson. AZ 85706 

Eniail:~~.~nidvanatlian~~acrtucson.co~~Tel: 520-434-6392 

INTRODUCTION 

High-temperature, structural ceramics are finding increasing applications for use as Components in gas 

turbine engines and rocket motors. A particular advantage of utilizing ceramic components over those fabricated 

from superalloy materials is that the former exhibit significantly greater strength and thermal stability at elevated 

temperatures. This enables the engines to operate at high temperatures and thus achieve greater efficiency. The 

reduced weight afforded by replacement of superalloy with ceramic turbine components has also been shown to 

increase the thrust efficiency of these engines [I]. Furthermore, conventional turbine engines fabricated from 

aerospace alloys require elaborate cooling schemes in order to maintain their integrity when operating at elevated 

temperatures. These cooling systems are unattractive since they add extra weight, cost and complexity to the turbine 

engine assembly. These problems could be eliminated if higher melting temperature materials, such as ceramics, 

were used in the manufacture of its engine components. 

Although the ceramics have many attractive properties, their low fracture toughness limits their use in 

highly loaded structural applications such as turbine and compressor blades. It is well known that monolithic 

ceramics lack the fracture toughness necessary to be considered for aerospace applications. To be used for such 

applications, materials must possess low density, high elastic modulus, a low thermal-expansion coefficient, high 

thermal conductivity, excellent erosion and oxidatiow'corrosion resistance, and flaw-insensitivity. They will in 

many cases also be required to possess the ability to be joined, to survive thermal cycling and multi-axial stress 

states, and for reusable applications the materials must maintain the above attributes after prolonged exposure to 

extremely harsh chemical environments. The final and possibly most important attributes for these materials are the 

need to be of low cost and readily available in large quantities. 

Fracture toughness of such materials could be improved by embedding continuous fibers into a ceramic 

matrix. This engineered material is called a ceramic matrix composite or CMC [2]. However, current state of the art 

methods for the fabrication of CMC materials such as chemical vapor infiltration (CVI) or polymer impregnation 

and pyrolysis (PIP) are expensive and time-consuming. Additionally, these processes cannot be easily adapted to 

rapid prototyping techniques, which would effectively reduce costs and fabrication times. 

Fibrous monoliths (FMs) are a new class of structural ceramics [3-51. They have mechanical properties 

similar to CFCCs, including very high fracture energies, damage tolerance, and graceful failures but can be 

produced at a significantly lower cost. Since they are monolithic ceramics, FMs are manufactured by conventional 

powder processing techniques using inexpensive raw materials. This combination of high performance and low cost 

enables FMs to wider applications of ceramics in energy and defense related applications. FMs are either sintered or 

hot pressed to various fibrous textures. The two phases that make up the macroarchitecture of a FM are a primary 

phase in the form of elongated polycrystalline cells. separated by a thin secondary phase in the form of cell 

boundaries, as shown in Figure 1. Typical volume fractions of the two phases are 80 to 95 9.0 for the primary phase 

(polycrystalline cell), and 5 to 20 90 for the interpenetrating phase (cell boundary). The cell phase is typically a 

structural ceramic, such as ZrC, HfC, Si3N4, or Sic, while the cell boundary phase is typically either a weaklybonded, low-shear-strength material such as graphite or hexagonal BN. 

Advanced Ceramics Research, Inc. ( ACR) and the University of Michigan have produced fibrous 

monolithic ceramics from a variety of materials using a simple process for converting ordinary ceramic powder into 

'green' fiber consisting of the powder and a thermoplastic polymer binder. These fibers can be compacted into the 

'green' state to create the fabric of polycrystalline cells after sintering. The process is widely applicable, allowing 

cell/cell boundary bi-component fiber to be made from any thermodynamically compatible set of materials available 

as sinterable powders. The scale of the microstructure is determined by the green fiber diameter (cell size) and 

coating thickness (cell boundary). More details of the FM process as well as the different FM systems currently 

available niay be seen in references 3-5. 
(e.9. BN, C) (e.9. Si3N4, ZrC) 

Figure 1. Schematic of a typical uniaxial Fibrous Monolith microstructure. 

At present, most commercial monolithic or composite ceramic-fabrication processes do not fabricate net 

shape parts and require extensive finish machining. ACR has developed an efficient, cost effective ceramic 

prototyping process termed Wax Dip Molding (WDM) to address these issues. Figure 2 is a schematic of the 

process, while Figure 3 shows the ACR gelcasting technique schematic. WDM is a new ceramic fabrication 

technique involving CNC-machining a model of the desired component from a block of special water soluble 

polymer blend material developed at ACR followed by castingholidifying molten wax around the machined model. 

The model is then removed from the wax merely by washing with water; leaving a core behind in a wax mold. High 

solids-loaded ceramic slurry is subsequently cast and themially gelled within the mold. The gelled green ceramic 

part is then removed from the mold by melting the wax away. The green part is then subjected to typical binder 

burn out and sintering operations commonly encountered in conventional ceramic processing. 

Figure 2. WDkl process diagram. 

A significant advantage of the WDM process is that it is reasonably simple and can rapidly turn out 

complex shaped ceramic articles in short order compared to other ceramic prototyping and other low volume 

manufacturing techniques. A photograph of a typical turbine part made by this process is shown in Figure 4. Parts 

made using this technique also exhibit mechanical properties that are generally better than conventionally processed 

materials and the technique does not require complex manufacturing equipment or extensive labor. In order to 

further improve the fracture toughness of the components that could be used in aerospace applications, ACR 

investigated the possibility of combining the WDM and FM processes to fabricate gelcast ceramic parts that are 

reinforced with FM fibers. There are several advantages to the development of such a process. 

Net-shape ceramic-composite parts could be fabricated directly from CAD designs. 

These parts would possess higher fracture toughness than monolithic ceramic parts. 

Since both the fibers and the monolithic ceramic matrix are mixed with thermoplastic or thermoset binder 

systems, they would both shrink at approximately the same rate during binder burnout and sintering, thus 

providing a fully dense part. 
I GELCASTING PROCESS 

~ 

Si3N1 

ZrC 

Sic 

Sic 

Figure 3. A schematic of the ACR gel-casting process. 

SiJNJ /BN 

ZrB2/BN 

SiCBN 

Si3N4 /BN 

Figure 4. A sintered silicon nitride microturbine blade fabricated via WDM technique. 

ACR has successfully developed gel-casting formulations of SijNJ, Sic, Sialons, and ZrC so far. Since the 

FM systems and the gel casting system would be thermodynamically compatible, the ceramic composite system 

would be less prone to environmental degradation. Additionally, since the components would be fully dense, the 

fibers and the matrix would be less prone to oxidation and loss of critical propertues. ACR's gel casting-Fibrous 

Monolith system capabilities are shown in Table I. Additional systems are currently in development. This paper 

presents the preliminary results with the Si3N1/BN fibers reinforced with a Si3N4 gel casting slurry. 

Table 1: Possible Composite Systems 

[ Gel Casting System I Fibrous Monolith System I 
EXPERIMENTAL PROCEDURES 

A schematic describing the fabrication process is shown in Figure 5. Green Si3NI/BN FM feedrods were 

fabricated and extruded into a fiber preform using ACR's Extrusion Freeform Fabrication (EFF) equipment. More 

details of the EFF process are given in reference 6. The extrusion of the fibers could be achieved with the help of a 

high-pressure extrusion head that is retrofitted into a commercially available Stratasys rapid prototyping machine or 

a CNC machine. The fabrication of a mold will involve CNC-machining a model of the desired component from a 

block of special water soluble polymer blend material developed at ACR followed by casting/solidifying molten 

wax around the machined model. The model is then removed from the wax merely by washing with water; leaving 

a core behind in a wax mold. It is important to note that this mold will be in two halves, to assist the placement of 

the fibrous monolith preform into the mold. High solids-loaded ceramic slurry is subsequently cast and thermally 

gelled within the mold. The gelled green ceramic part is then removed from the mold by melting the wax away. 

The green part is then subjected to typical binder burn out and sintering operations commonly encountered in 

conventional ceramic processing. 

Figure 5: A schematic of the gel cast fibrous monolith ceramic composite process. 

The major consideration for a successful slurry include reproducible rheology, rapid gelling characteristics, 

facile wetting behavior upon the fibrous monolith surface, and ultimately its ability to be pyrolyzed and sintered to 

produce a high-strength ceramic component. The importance of reproducible slurry rheology should not be 

underestimated since commercially attractive slurries should not exhibit batch to batch variability in their viscosities 

and possess a reasonable shelf life. Silicon nitride slurries were formulated in a non-aqueous vehicle. The silicon 

nitride used in slurries was a bimodal mixture of Ube SN E-10 and E-05 powders. The overall solids content of the 

slurries was 52 volume percent. The slurries exhibited a reproducible rheology and enhanced shelf life as can be 

seen in Figure 6. It can clearly be seen that the slurry has a thixotropic rheology. ACR has successfully developed 

highly loaded ceramic slurries with shelf lives exceeding 3 months. 
0 01 01 1 10 100 

Shear rate (Ils) 

Figure 6: Viscosity plot of silicon nitride slurry formulated in a non-aqueous vehicle and aged for various 

amounts of time. 

For demonstrating the process itself, fibrous monolith filaments were extruded and chopped into two-inch 

lengths. These were subsequently laid-up in alternating 0 and 90 degree orientations. The fibers were laid into a 

mold, The preforms were then infiltrated with the ceramic slurry. Vacuum was applied to remove any entrapped air. 

The samples were subsequently cured. The samples were cut into ?“x2”x0.25” billets and hot pressed. An image of 

the billet after hot pressing is shown in Figure 7. These billets had an average density of 3.25 g/cc, which is 

approximately 9% of the theoretical density. After hot pressing. the billets were cut into mechanical test bars for 

four point bend testing. 

FM - GELCAST COMPOSITE HP Si3N4 - Bn - Sidd 

Figure 7. Hot pressed FM Gelcast composite billet 

Mechanical testing was performed according to ASTM C 1161-90 for flexural strength of ceramics at 

ambient temperatures. An average strength of 460 * 53 MPa. A typical load displacement curve is shown in Figure 

8. An optical micrograph of the fracture surface of a typical sample is shown in Figure 9. The results obtained from 
the niechanical testing show no load transfer to the reinforcing fibrous monolith fibers. Additionally, few fibers were 

found on the fracture surface, as seen in Figure 9. There could be several reasons for these results. 

Insufficient fiber volume fraction. It was estimated that the fiber volume fraction was 10-1500. 

The fibers may not have stayed in place during the casting of the gel casting slurry and could have created a 

sample with fiber volume gradients through the thickness. 

Insufficient control of the interfacial bond strength between the FM fibers and the gel casting matrix. 

Future experiments will emphasize the optimization of the interfacial bond strength, improving the fiber 

volume ratio, as well as maintaining the fiber placement during the casting process. The ultimate goal would be the 

development of a manufacturing process that can create a CMC component directly from its CAD design 

LJU 

200 

150 

c 

1 

1 3 100 

lL 

50 

0 

1Flexural Strength = 534 MPa 

0 0.005 0.01 0.015 0.02 0.025 

Displacement (in) 

Figure 8. Typical room temperature load-displacement curve for a Si3NdlBN Fibrous Monolith reinforced 

Si3N1 gelcasting ceramic matrix composite. 
Figure 9. Optical micrographs of the fracture surfaces of a typical F 

(Both surfaces side by side - 10N; one surface - 15X) 

ACKNOWLEDGMENTS 

The authors appreciate the support and advice of Dr. William Coblenz at DARPA in conceiving and 

executing the experimental idea. 

REFERENCES 

1. 

2. 

3. 

4. 

5. 

Richerson, D.W., “Ceramics for Turbine Engines,” Mechanical Engineering, pp. 80-83, September 1997. 

Effinger, M. R., Genge, G. G., Kiser, J. D., “Ceramic composite turbine disks for rocket engines,” ,4d\mzced 

Materials and Processes, 157 [6], pp. 69-73, (2000). 

D. Kovar, B.H. King, R.W. Trice, and J.W. Halloran, “Fibrous Monolithic Ceramics” J. Am. Cerani. SOC., 80. 

G.E. Hilmas, A. Brady, U. Abdali, G. Zywicki and J.W. Halloran, ”Fibrous Monoliths: Non-Brittle Fracture 

from Powder Processed Ceramics,” hlut. Sci. & Eng. A,. 195, 263-268 1995. 

G.E. Hilmas, A. Brady and J.W. Halloran, ‘Sic and Si3NJ Fibrous Monoliths: Non-Brittle Fracture From 

Powder Processed Ceramics Produced by Coextrusion,“; pp. 609-6 14 in Ceramic Transactions-Vol. 5 1 Ceramic 

Processing Science and Technoloa.. Edited by H. Hausner and G. Messing. American Ceramic Society 

Westerville, OH, 1993. 

6. Vaidyanathan, R., Lombardi, J. L., Walish, J., Kasichainula, S., Calvert, P., and Cooper, K., ”Extrusion 

Freeforni Fabrication of Functional Ceramic Prototypes,” Ceraniic Engineering arid Science Proceedings, 2 1 

[ IO] 247 1-2487, 1997 

[4], pp. 12 1 - 128, (2000). 
Solid Freeform Fabrication of Continuous Fiber Reinforced Composites for Propulsion Applications 

R. Vaidyanathan, M. Fox, J. Walish, M. Rigali and R. Cipriani 

Advanced Ceramics Research, Inc., 3292 E. Hemisphere Dr. 

Tucson, AZ 85706-5013 

Tel: 520-4346392 : emaii:Jr.vaidvanathan(n:acrtucson.con~ I 

J. Gillespie and S. Yarlagadda 

Center for Composite Materials 

University of Delaware, Newark DE 197 19-3 144 

M. Effinger 

NASA Marshall Space Flight Center 

George C. Marshall Space Flight Center 

Huntsville, AI 35812 

INTRODUCTION 

Monolithic ceramics lack the fracture toughness necessary to be considered for propulsion related 

applications. To be used for such applications, materials must possess low density, high elastic modulus, a low 

thermal-expansion coefficient. high thermal conductivity, excellent erosion and oxidationlcorrosion resistance, and 

flaw-insensitivity, They will in many cases also be required to possess the ability to be joined, to survive thermal 

cycling and multi-axial stress states, and for reusable applications the materials must maintain the above attributes 

after prolonged exposure to extremely harsh chemical environments. The final and possibly most important 

attributes for these materials are the need to be of low cost and readily available in large quantities. 

Fracture toughness of such materials could be improved by embedding continuous fibers into a ceramic 

matrix. This engineered material is called a ceramic matrix composite or CMC [ 11. However, current state of the art 

methods for the fabrication of CMC materials such as chemical vapor infiltration (CVI) or polymer impregnation 

and pyrolysis (PIP) are expensive and time-consuming. Additionally, these processes cannot be easily adapted to 

rapid prototyping techniques, which would effectively reduce costs and fabrication times. 

Recently, Advanced Ceramics Research, Inc. (ACR) has developed a low cost, flexible-manufacturing 

processes for ceramic based continuous fiber reinforced composites. This process, called Continuous Composite 

Co-extrusion (C3), incorporates fiber tows into a ceramic matrix to fabricate ceramic-matrix/ceramic fiber 

composites. The cd process is the continuous extrusion of matrix material around a fiber tow. A flow chart 

illustrating the C’ process is shown in figure 1. An interface material such as graphite is introduced between the 

fibers and the matrix to minimize the thermal expansion mismatch between the fibers and the matrix during the final 

consolidation step. The process is simple, robust and is widely applicable to a number of ceramic composite material 

systems such asCOSiC, CE‘ZrC, SiC/SiC etc. 

The process begins by mixing the ceramic and graphite powders individually with thermoplastic binders 

and additives in a high shear mixer. The resulting ceramic powder/thermoplastic blend is pressed into a ”green” rod. 

Next, the graphite powderhhermoplastic blend is pressed into a small diameter “green” rod. A hole of equal 

diameter to the graphite rod is drilled into the center of the rod and the graphiteithermoplastic rod is inserted. This 

green composite feedrod is then re-pressed and a hole is drilled in the center of the ZrCjgraphite composite feedrod 

allowing the carbon fiber tow to pass through the center. Since the matrix and the interface are monolithic powders, 

the cost of the final composite could be lower than CVI and PIP based CMC’s by at least an order of magnitude. 

Recently, an innovative manufacturing technique called Advanced Tow Placement (ATP) has been 

developed Gillespie and co-workers [2] for thermoplastic and thermoset based polymer composite components at 

the University of Delaware Center for Composite Materials (UD-CCM). The ATP process is an enabling 

technology, developed originally for thermoset composites and more recently for in-situ non-autoclave consolidation 

of large-scale thermoplastic composite materials for High Speed Civil Transport (HSCT) applications. In this 

process, consolidation of the thermoplastic composite tows is achieved by the concurrent use of localized heat and 
pressure so that bonding is achieved at the newly formed interface and consolidation is achieved within the material. 

Figure 2 shows the schematic of the automated thermoplastic tow-placement process at UD-CCM. 

Since thermoplastic binders are used in the fabrication of ACR's C3 green CMC filaments, the ATP process 

originally developed for thermoplastic prepreg tows could be adapted to ceramic composites. The knowledge base 

of the ATP process for thermoplastic prepregs can be utilized to lay down ceramic tows reinforced with continuous 

fibers in the desired configuration. This allows the use of a proven technology for low cost, rapid fabrication of large 

complex ceramic parts. This process also allows the possibility to create complicated parts directly from a CAD 

drawing without human intervention. This process is called Ceramic Composite Advanced Tow Placement or 

CCATP process. In this paper, initial results with the CCATP process are presented. 

I Co-extrusion * 

Green cenatic/Cr 6Ulltlaent 

Figure 1. Flow Chart Illustrating the C3 Process. 

Main Incoming Prepreg Tow Heater Nozzle: H, 

\ Preheater Roller: Fi \ Preheater Nozzle: H, 

-Brickface Layup Preconsolidated Material 

Figure 2. Schematic of the ATP process 

EQUIPMENT AND EXPERIMENTAL PROCEDURES 

EQUIPMENT 

The automated tow placement system at the University of Delaware Center for Composite Materials was 

developed for rapid, low cost fabrication of fiber reinforced thermoplastic parts, and is shown in Figure 3. It 

employs the use of two hot-gas nitrogen torches to heat the material and two rollers to provide the pressures required 

for consolidation, as shown in Figure 2. The purpose of the first torch and roller is to preheat the composite surface 
and incoming tow together. The material is thus "tacked" to the surface with this roller. This tacking procedure is 

useful in that the fed material is carefully bonded to the surface and not pulled with the main consolidation roller. 

This tacking approach also aids in improving the efficiency of the cut and refeed mechanism. The second torch 

(main heater) provides supplemental through thickness heating to facilitate consolidation and bonding of the tow and 

substrate under the consolidation roller. These rollers provide the necessary forces to achieve complete intimate 

contact across the tow interface, and as a boundary pressure for preventing any internal void development. 

Figu Itoy. 

The forces applied to both rollers are controlled independently using a series of pneumatic actuators. The 

composite tows can be placed in a regular repeating pattern or with brick-face symmetry. The brick-face geometry 

has the advantage that more homogeneity is achieved throughout the composite structure. All the processing inputs 

are controlled either manually or through a PID control scheme from a LabVIEWTM interface. An ABB IRB 6400 

Robotic Work cell, shown in Figure 3, is used to control the motion of the placement head. This robot is capable of 

carrying a I2Okg payload at automated speeds up to 7m/s and is accurate to 0.Olmm. A computer-controlled 

nitrogen hot gas torch control system (not shown) is used to monitor and control gas flow rate and temperatures 

within both torches. The composite surface temperatures can be adjusted by either increasing the process velocity or 

by independent change of the nozzle heights. This novel temperature control method shows promise as an adaptive 

method for rapid control of surface temperatures and was recently patented by the UD-CCM [US. Patent No. 

5,626,4721. The temperatures are measured and controlled with an AGEMA Thermal Imaging camera with a neural 

network based PID control system. The camera measures the viewable peak temperatures on the laminate surface 

and adjusts the nozzle heights accordingly to compensate for any deviation in set point temperatures. A LabviewTM 

interface is used to input number of layers, ply orientation, surface temperatures, panel geometry, and process 

velocity. This interface can also be used in conjunction with a laser displacement unit to measure warpage during 

processing. 

Test Materials 

The ATP process for thermoplastics lays down prepreg tows, typically 0.125 - 0.2 mm in thickness, with 

the tow width depending on the hardware. The ATP head at UD-CCM can lay down 6.25-mm wide tows, while 

industrial machines, such as Cincinnati Milacron's Gantry System can lay down tows as wide as 150 mm. 
Fiber reinforced ceramic materials for this study were supplied by ACR and were in the form of green 

tows. The reinforcing fiber was carbon and the matrix was zirconium carbide based, in a low temperature 

thermoplastic binder. The tows were thicker than the thermoplastic tows for polymer matrix composites. 

Initial tests with the ceramic tows revealed several iniportant issues: 

The matrix was somewhat brittle and fractured easily under tension. This can pose a problem during tow 

placement as the tow is under tension to achieve good quality. 

Cut and re-feed mechanism on the head did not function consistently. This is due to the difference in 

thermoplastic (for which it was designed) and ceramic tows. Ceramic tows were manually cut to specific 

lengths and manually placed to simulate this. 

Adhesion between the tows and the matrix was not good. While this is not required at the green stage, fractures 

in the matrix result in exposure of bare fibers (in tension), causing inconsistent loading. This may not be an 

issue, as the actual fiber wet-out occurs during the sintering phase and can alleviate it. Further optimization of 

the interface thickness and type that is being carried out. 

The process temperature of the thermoplastic binder was low. Typical thermoplastic tows have process 

temperatures in the 300°C range. Therefore, lower torch temperatures were used. 

Over time, the matrix started adhering to the rollers. This occurred due to the rollers heating up past the melt 

temperature of the thermoplastic binder and resulted in the rollers peeling away the matrix from the tows. 

Solutions to overcome this problem are being devised. 

Minimal force was required for consolidation. 

ATP Process Modification for Ceramic Tow Placement 

Several process modifications were performed to obtain better quality material. These process 

modifications resulted in good material quality as shown in Figure 4 and 5. Note that, the tows were cut and placed 

manually to simulate the cutlrefeed mechanism of the ATP head (Figure 6). Once the tows were placed, the robot 

performs the entire tow placement sequence to heat and consolidate tows. 

Figure 4. Good material quality was obtained 

with modifications to the ATP head 

CMC Laminate Fabrication by Ceramic Tow Placement 

Figure 5. Photograph of ceramic tows placed manually. 

Upper half of the photograph shows tows 

consolidated by the modified ATP head 

Two green laminates were fabricated with the ceramic tows: 

225 mm long x 75 mm wide [O/O] (9” long x 3” wide) 

150 mm long x 75 mm wide [0/90/0] (6” long x 3” wide) 

Figure 6 shows the ATP head in action during fabrication of both laminates. Typical microstructures ae 

shown in figures 7 and 8 respectively. For both cases, the entire robot movement sequence is setup by computer 

programs developed for the ATP thermoplastic tow placement experiments. The torch parameters (temperatures, 

heights, and gas flow rates), consolidation force and head velocity can be controlled on the fly as inputs to the 

computer program. Final panel dimensions and lay-up sequences are also inputs to the program. Once these inputs 

are given to the program, it operates the robot in automatic mode and lays down the tows as specified. Green 

ceramic matrix laminates of any size (within limits of the robotic workcell), fiber orientation and material system 
can be fabricated by this technique. The current effort has not focused on optimizing process parameters. but on 

demonstrating the feasibility of rapid, low cost fabrication of fiber reinforced green ceramic composites. 

Both laminates were successfully fabricated, though the tows were hand-placed due to the inconsistent 

operation of the cut and refeed mechanism. This did not allow for a through study of the overlaps and gaps during 

the automatic placement of tows. In addition, tension is necessary to maintain fiber straightness during consolidation 

and this was not possible at laminate edges due to hand placement of tows. Consequently, movement of tows during 

consolidation was seen. With automatic feed from a spool with tension, cut and refeed can overcome all these issues 

and identify correct level of overlap for consistent quality during consolidation. 

Figure 6. Modified ATP head consolidating 0 ceramic tows for the [O/O] laminate with top 0 layer showing 

I mm 

Figure 7. Typical cross-sections of rapid prototyped Figure 8. Typical cross-section of rapid 

[O] CDZrC panels prototyped 1O/W/O] CflZrC panel 

Other components 

Figure 9 shows a 6-inch diameter cylinder that was fabricated using the ATP equipment. This clearly shows 

the potential and capability of the process to fabricate complicated, full-scale components. This tube contains only 

three wraps of material. 

Scale-up Potential 

Figure 10 shows the scale-up of thermoplastic ATP process developed in a DARPA RAPTECH (Rapid 

Technology) program led by UD-CCM with DuPont, Hercules,’Alliant and Cincinnati Milacron. In this effort, UDCCM demonstrated lab-scale viability and developed optimal process conditions for scale-up. Infrastructure for 

large-scale fabrication using gantryhobotic system exists. 

Mechanical property and microstructural characterization of panels 

Billets were hot pressed. The hot pressed panels were not entirely crack-free which indicated that the 

thermal stresses were not completely eliminated. An estimated fiber volume fraction of 3.5-4O0/b was achieved after 

sintering. Specimens were tested in tension at a displacement rate of 0.2 mm/min using a load cell of 2500 Ibs. at the 

University of Arizona. Representative samples were cut from the billets for testing. All the specimens exhibited 

good composite behavior, clear fiber pullout and in some cases, a stable loading pattern, with the load being taken 
up entirely by the fibers. It appears that the graphite interface thickness was too large for the composite to exhibit a 

high enough strength and good composite behavior at the same time. However, it is believed that these issues related 

to materials processing, though major, can be addressed and corrected. Typical tensile stress-displacement curve is 

shown in Figure 11 and 12, which shows good load transfer and the ability of the fibers to carry the load after the 

initial matrix has cracked. In many cases, the composite did not fail entirely and the fibers continued to carry the 

load. The test had to be discontinued at this point. 

Figure 9. A six inch ZrCICf cylinder fabricated using the ATP equipment 

Figure 10. Automated Tape Placement head and gantry. (Picture courtesy of DuPontKincinnati-Milacron) 
0" 100 

90 - 

80' 

70' 

60' 

50' 

40' 

30' 

I 

& 

8 

4 

4 

4 I 

A 

4 

4 

r 

4 

1 

9 

I 

0 10 20 30 40 50 60 70 80 90 100 

Percent nonnalked displacement (% of total) 

Figure 11. A typical tensile stress-strain curve for the rapid prototyped 0/90/0 panel. 

Loo 

90 

80 

70 

60 

50 

40 

30 

20 

in Y I 

20 40 60 80 

Percent normalized displacement (YO of total) 

100 

Figure 12. Typical stress-strain curve for a rapid prototyped CffZrC composite specimen showing load 

transfer and the ability of the fibers to carry the load. 
CONCLUSIONS 

1. 

2. 

An innovative rapid prototyping technology to freeform fabricate continuous fiber reinforced ceramic matrix 

composites was successfully developed. 

The feasibility of using the ATP process, with some modifications, for rapid fabrication of green ceraniic 

composites has been demonstrated. [0/0] and [0!90!0] laminates were fabricated using the computer-controlled 

ATP head. Critical process parameters were torch parameters, consolidation force and process velocity. Several 

issues that need to be addressed are the automated cut and refeed system, parametric studies, optimization of 

process parameters and binder optimization. 

2D panels were rapidly prototyped using a fiber placement system similar to commercially available fiber 

placement equipment. A 6-inch diameter cylinder was also fabricated. 

An estimated fiber volume fraction of 35-40% was obtained in the composites after sintering. 

The composite exhibited good fiber pull-out and load-transfer from the matrix to the fibers, although further 

optimization of the interfacial properties are required to obtain satisfactory mechanical properties. 

3. 

4. 

5. 

ACKNOWLEDGMENTS 

This manuscript contains work performed as part of the “Rapid prototyping of continuous fiber reinforced 

ceramic composites,” SBIR phase I program funded by NASA Marshall Space Flight Center under contract number 

NASX-00084. 

REFERENCES 

1. 

2. 

Effinger, M. R., Genge, G. G., Kiser, J. D., “Ceramic composite turbine disks for rocket engines,’‘ Advanced 

Materials arid Processes, 157 [6], pp. 69-73, (2000). 

Don, R. C., J. W. Gillespie Jr., and S. H. McKnight, “Bonding Techniques for High-Performance Thermoplastic 

Compositions,” U. S. Patent No. 5643390. issued July I, 1997. 
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SFSSIOII c3 Rapid Pioro~ypulg 

- , 1, .-( . High-Efficiency Monolithic Lightweight Aluminum Cast Structure 

JOHN BOWKETT 

Nu-Cast, Inc. 

29 Grenier Field Road 

Londonderry, NH 03053 USA 

Phone: 603-432- 1600 

Fax: 603-432-0724 

E-mail:lnci@,erolen.com I 

Nu-Cast, Inc., is manufacturing highly efficient, low-cost truss-like platforms/structures 

using the investment casting process developed at Nu-Cast, Inc., and the current rapid prototyping 

capabilities of steriolithography (SLA). This integrated production process allows for direct transfer 

of the computer design into hardware with a minimum of compromising fabrication restrictions. In 

the monolithic 3D-truss approach, control of structural integrity and thermal homogeneity is significantly improved over conventional multipart assemblies because of the elimination of most joint 

problems and their analytical uncertainties. For example, preliminary analysis of a typical 3D-trussbased instrument platform indicates a potential increase in stiffness up to 130X when compared to a 

plate of equal mass and area. Localized high-stress areas can be eliminated easily using this approach; additional material can be added locally during normal detailed design to satisfy the part’s 

system requirement and to allow an efficient structural design to become a reality. Additionally, there 

can be a significant cost reduction for this monolith, compared to multipart assemblies, especially 

where tight tolerances are not system-functional but are only required for individual piece-part 

assembly/interface. The improved component performance achievable at a given weight with reduced resource expenditure will clearly support the NASA mandate to “do more with less.” 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc.nasa.gov 
Preliminary Component Integration Utilizing Rapid Prototyping Techniques 

Ken Cooper, NASA Marshall Space Flight Center 

Pat Salvail, IITRl 

Abstract 

One of the most costly errors 

committed during the development of an 

element to be used in the space industry 

is the lack of communication between 

design and manufacturing engineers. A 

very important tool that should be 

utilized in the development stages by 

both design and manufacturing 

disciplines is rapid prototyping. 

Communication levels are intensified 

with the injection of functional models 

that are generated from a drawing. 

At the Marshall Space Flight 

Center, this discipline is utilized on a 

more frequent basis as a manner by 

which hardware may be tested for design 

and material compatibility. 

Background 

Rapid prototyping in this text 

refers to a collective set of solid 

freeform fabrication technologies, which 

build physical models directly from 

computer aided design (CAD) data. The 

fixtureless processes operate in an 

additive fashion, whereas each model is 

built from the bottom upwards by adding 

thin horizontal layers of material. 

The MSFC maintains a unique 

rapid prototyping laboratory, equipped 

extensively with each domestically 

available rapid prototyping technology; a 

total of seven processes in all. These 

include the following: 

1. Stereolithography, a liquidresin based technology which 

2. 

3. 

4. 

5. 

6. 

7. 

employs an ultraviolet laser to 

selectively cure the epoxy into 

the shape desired. 

Selective Laser Sintering, a 

powder-based process which 

uses a laser to melt cross 

sections of polymer or semimetallic powders into the 

shape desired. 

Laminated Object 

Manufacturing, a solid-based 

process which adheres layers 

of paper, plastic or composite 

and cuts each cross section 

with a laser. 

Fused Deposition Modeling, 

another solid-based process 

which extrudes a semi-molten 

thermoplastic through a 

moving XY orifice to form the 

necessary shape. 

Multi Jet Modeling builds solid 

wax patterns by printing layers 

of hot wax directly through 

standard print jets. 

Three Dimensional Printing 

prints layers of binder into a 

polymer powder matrix. 

Laser Engineered Net Shaping 

deposits a thin bead of metal 

powder into the focal point of a 

high-powered laser, while the 

part is moved in the XY plane 

underneath to form the cross 

sections properly. 

These processes are employed at the 

MSFC for a variety of concurrent 

engineering tasks, including concept 

modeling, assembly verification, fitcheck analysis, flow functionality testing 

and investment casting pattern making. 
Applications at the MSFC 

Shooting Star. Experinten t 

During the initial stages of the 

Shooting Star Experiment, rapidly 

produced absorbers were cast of a 

superalloy to be used in thermal 

experiments, prior to the procurement of 

the rhenium hardware. 

Early designs of the solar thermal 

engine housing and absorber inserts 

were rapid prototyped in an investment 

casting wax in a matter of days, and the 

parts were investment shelled and cast 

on-site within four weeks. 

These hardware castings have 

been, and continue to be, tested 

extensively by thermal elevation and 

cycling in the MSFC Test Stand Area. 

Data from these inexpensive models 

allowed for early analysis of the 

functionality of the engine design, as 

well as saving the project just under 

$300,000 and six to twelve months of 

lead time. (See Figures 1 and 2) 

Simplex Tu]-hoPtinip 

Another application involved the 

Simplex TurboPump, a high pressure 

experimental turbomachinery design. 

The application of rapid prototyping 

prevented a costly mistake in the 

manufacturing of the pump’s complex 

impeller . 

Five of the components were set 

to be machined, at an individual cost of 

$60,000 each. The drawings had already 

been delivered to the machine shop and 

tooling-up had begun when a rapid 

prototyped model was fabricated using 

M SFC ’s s tereoli thography apparatus. 

The resulting plastic model 

verified that the blueprints designated 

the impeller blades the exact reverse of 

what the final part needed to be, and 

hence production was altered to make 

the final correct designs. Approximately 

$300,000 again was saved by a simple 

plastic model which cost about $1,000 to 

prototype. 

Additional savings in time and 

cost were then added throughout the life 

of the Simplex program by the 

application of rapid prototyping and 

investment casting to provide castability 

verification of candidate materials, 

fabrication planning and continuous 

auditing with functional models and 

hardware. (Figure 3) 

Space Shuttle Maiii Engine Fuel Ducts 

During a redesign of the Space 

Shuttle Main Engine, it was determined 

that replacement of existing supply and 

drain fuel lines would reduce weight and 

increase safety and reliability. 

The previously used lines were 

fabricated by welding various shaped 

sections of steel line together in order to 

access all of the required inlet/outlet 

ports of the engine. 

The new design called for 

continous feedlines to be custom-formed 

from tubing to reduce the weight of the 

welds, optimize flow and decrease the 

probability of fuel leakage. 

Unfortunately, the first hot gas 

duct to be fabricated didn’t integrate 

properly after additional hardware was 

attached to the engine during assembly. 

The process to correct the problem was 

costly and time consuming, and it was 

determined that rapid prototyping 

patterns be fabricated for the remaining 

five ducts for fit verification. 
Each duct was approximately 

seven feet in length and six inches in 

diameter, with a complex threedimensional curvature and precisely 

placed junctions. The prototypes were 

fabricated in twelve-inch sections using 

the laminated object manufacturing 

process at MSFC, and it took two to 

three weeks to fabricate the entire set. 

The engine contractor designed each 

section having dissimilar boss-andsocket alignments for proper assembly. 

These prototyped lines were 

shipped to the engine contractor facility, 

where they were assembled and mounted 

to an actual main engine to verify the 

designs prior to manufacturing the 

remainder of the required lines. A 

potential cost saving of approximately 

$35,000 per line was recognized by the 

application of the rapid prototyping 

models, resulting in an overall potential 

savings of about $175,000 and several 

months of lead-time. (Figures 4) 

Meteorite Patch Kits 

One continuous application of 

rapid prototyping at MSFC involves a 

project that applies meteorite patch kits. 

The process requires precise mixing of a 

two-part solution to obtain the adhesive 

properties required for composite 

material bonding. 

A special funnel was designed 

which allows for accurate delivery of 

each component of the adhesive mixture. 

Due to the low number of these funnels 

that are required. approximately two to 

four every year, it is not cost effective to 

have them mass-produced. 

The solution is to directly 

fabricate the funnels using rapid 

prototyping. The materials used are 

compatible and provide adequate 

strength and density to prevent 

permeation or breakage. The funnels are 

even chemically cleaned and reused 

several times prior to disposal.(Figure 5) 

Space Shuttle Main Engine Fuel Seals 

Another shuttle engine 

application of rapid prototyping occurred 

recently when, after a design change, it 

was found that a particular fuel line 

didn’t match up properly with a pump. 

The result was a need for a 

flexible seal, which consisted of a 270- 

degree rotation of an eccentric nature. 

The overall part required was about nine 

inches in diameter. 

The contractor for the pump 

received several solid prototypes of the 

flange from the MSFC rapid prototyping 

lab. These parts were used to make 

molds, which in turn produced the final 

products required to satisfy the needs of 

the engine. 

Summary 

The application of rapid 

prototyping technologies at the MSFC 

continues to yield significant cost and 

timesavings to NASA projects. 

Increased use of these technologies is 

anticipated in order to cater to a 

concurrent engineering environment that 

has been realized due to decreased 

funding allocations and project time 

constraints mandated throughout the 

agency. 

Similar applications and 

successes are seen throughout the private 

manufacturing industry, as well, where 

profit margins and a highly competitive 

market drive companies to deliver 

products quickly and efficiently. 
Figure 1 

Figure 2 
Figure 3 

Figure 4 
Figure 5 
DARREN K. ROGERS and Janusz Plucinski 

Touchstone Research Laboratory, Ltd. 

Triadelphia, WV 26059 USA 

Phone: 304-547-5800 

Fax: 304-547-5764 

E-mail:ldkr@,eold .trl.com 1 

Carbon foams produced by the controlled thermal decomposition of inexpensive coal extracts 

exhibit a combination of structural and thermal properties that make them attractive for aerospace 

applications. Their thermal conductivity can be tailored between 0.5 and 100 W/mK through precursor selection/modification and heat treatment conditions; thus, they can serve in either thermal 

protection or heat transfer systems such as heat exchangers. Because their structure is essentially a 

3D random network of graphite-like members, they also can be considered low-cost, easily fabricated replacements for multi-directional structural carbon fiber preforms. Strengths of over 4000 psi 

in compression are common. Their density can be designed between 0.1 and 0.8 g/cm3, and they can 

be impregnated with a variety of matrices or used, unfilled, in sandwich structures. These foams also 

exhibit intriguing electrochemical properties that offer potential in high-efficiency fuel cell and 

battery applications, mandrels and tooling for composite manufacture, ablative performance, and fire 

resistance. 

General Aviation Technology, supported from Langley Research Center. The potential of foam 

design through precursor selection, cell size and density control, density grading, and heat treatment 

is demonstrated. 

This paper presents the results of research conducted under NASA SBIR Topic 99.04.0 1, 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

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Low Density Monolithic Metal Honeycombs by Thermal Chemical Processing 

PI'S: Joe Cochran, Jim K. J. Lee*, Dave McDowell, Tom Sanders 

GFW's: B. Church, J. Clark, B. Dempsey, 'Le Hayes, K. Hurysz, T. McCoy, 

J. Nadler, R. Oh, W. Seay, B. Shapiro 

Schools of Materials Science and Engineering & Mechanical Engineering 

Georgia Institute of Technoloav 

Fourth Conference on Aerospace Materials, Processes and Environmental Technology 

September 18-20, 2000, Huntsville, Alabama 

A technology developed at Georgia Tech allows fabrication of thin-walled metal articles. Using 

conventional powder processing techniques, precise shapes were formed with non-metal precursors and 

subsequently converted to the metal state by a direct reduction process. The metal articles can be formed 

via powder forming techniques including extrusion, slurry coating of sacrificial cores, slurry casting 

methods (slip, pressure, centrifugal, tape, and gel casting), and dry pressing. By using fine powders in the 

micron and sub-micron range, articles that have small dimensions (Le., micro- to milli-meter) may be 

formed. Practical experience has shown that maximum particle sizes of 1/50 of the feature dimension are 

necessary for producing features with good precision. Through a properly controlled conversion process, 

the articles formed from brittle powder precursors (principally oxides) are chemically converted into a 

metal article with structural integrity and substantially the original shape. A variety of shapes have been 

formed by (1) Honeycomb Extrusion, (2) Spray Coating, (3) Dry Pressing, (4) Slip Casting, and (5) Tape 

Casting. Demonstrated alloys include stainless steel, maraging steel, lnconel 617 and 71 8, Super Invar, 

and copper alloys. Demonstrated strength and specific energy absorption of a maraging honeycomb at 

1.5 gmkc were approximately 400 MPa and 100 Joules/gm respectively. 

Low Density Metal Structures 

There are basically five types of metal foams or cellular metal structures that are either being 

used or under development as promising low density structures. These structure types (Fig.1) are closed 

cell foam (e.g., ALPORAS by Shinko Wire, Ltd.), open cell foam (e.g., reticulated foams by ERG, Inc. and 

INCO, Ltd.), hollow sphere foam (Georgia Tech and Fraunhofer), honeycomb (Hexcel and Georgia Tech), 

and lattice structure (Molecular Geodesic, Inc. and JAMCORP.). The first three types are stochastic in 

nature, the honeycomb and lattice structure are ordered or periodic structures. For each type of 

architectures, a variety of fabrication methods are possible. For further details on these foams, readers 

are referred to Metal Foams: A Desian Guide by M. Ashby et al. [l], in which the production methods and 

properties are described. 

The characteristics of a low density structure can be best described by its dominant geometry, 

relative density (p*/ps), and solid material properties. Defects and anisotropy, which most often are 

present, play a very important role in behavior of the low density structure. Above all, the relative density 

(p*/p,), a ratio of foam density (p*) to solid material density (p,), is the single most important parameter. 

Various mechanical, thermal, and physical properties are a function of p*/p,. The scaling relationship 

takes the form of 

where P is a property, c1 is a constant and n is an exponent. (Note: the superscript means property of 

the foam and the subscript s means property of the solid.). 

P'/PT =Cr(P'lP, 1" (1 1 
Using foam geometry as an example, when P represents the thermal conductivity of a metal 

foam, h, the equation becomes 

for both the open and closed cell type, with a being one. When P represents the electric resistively of a 

metal foam, R, the equation becomes 

for both the open and closed cell type, with a being one. 

A*/A, = (p*/p7)1 hs-I (2) 

(3) R'/R, = (p* lp, )-I M) -1 85 

For compressive strengths of foams, the global scaling relationships are 

a*/a, =(0.1 - 1.O)(p'/p,)l5 (4) 

CT * /CJ , = (0.1 - 1 .O)[ 0.5( p /p , )("" + 0.3( p * /p, )] 

O*/CT, =O.3(p8/p,)" (6) 

CJ'/O, =0.35(p'/p,) (7) 

for open cell type and 

(5) 

for closed cell type, where (r is the compressive strength. Specifically, the most widely accepted strength 

to relative density relationships are 

for the open cell foam, and 

for the closed cell foam. [2] 

the cell axial direction (Le., tested in the out of plane direction) scales linearly with relative density, 

For honeycombs of all cell shapes (square, triangular, or hexagonal), the compressive strength in 

dCJ, = (P'/P,). (8) 

When loaded off axis or tested in plane, cell walls are subjected to bending and transverse strengths are 

lower by a certain amount depending on cell shape and angle of force loading. 

Figure 2 contains plots of strength behavior of open and closed cell structures in comparison to 

honeycomb for stainless steel, titanium, and aluminum alloys according to Eq. (6), (7), and (8). The 

experimental properties of both open and closed cell foams sometimes fall short of the expected value by 

a factor of 2 to 100. [3] The experimental properties of hollow sphere foams fall between the theoretical 

closed cell and open cell foam curves. In general, hollow sphere foam is equal to or slightly better than 

the mechanical properties of closed cell foams. 

Honeycomb vs. Foam 

Current status of foam properties indicates major improvement in processing and alloy 

development are necessary before these foam structures to become competitive with ordered or periodic 

geometries. Based on Fig. 2, honeycomb geometry clearly excels among these low density structures, 

when structural application is the first order of consideration. Conclusive test results are rapidly becoming 

available to substantiate that honeycomb is the geometry-of-choice for better strength and stiffness, as 

compared to its stochastic counterparts. 

Among low density structures, honeycombs are manufactured and used in commercial quantities. 

There are two basic honeycomb manufacturing methods. Traditionally, the aerospace industries use AI, 

Ti and Ni based superalloy honeycombs, along with other non-metal composites, for weight reduction. 

They are made with thin sheet or foil of the alloys, crimped into a corrugated profile and joined to form a 

hexagonal cell. The automotive industry uses ceramic honeycomb made of cordierite as catalyst 

supports for emission control. These structures are fabricated by extruding plastic paste of ceramic 

powders with a binder. After extrusion the product is dried and sintered to strengthen the webs. 

To maximize the value of a low density structure, one needs to adopt the best possible 

geometry, to select a composition that has the suitable bulk properties, and to have it made with a 

process that is most economical. A geometry which is ideal for improved strength in transverse direction 
is the triangular honeycomb shown in Fig. 3. Triangular cell honeycomb can be made by the extrusion 

process as easy as the square cell honeycomb. The same can not be said about the crimped sheet 

process. About cost, honeycomb by powder paste extrusion is also more economical. On the mass 

production scale, such as for the auto industries, finished parts are approximate at -$5.00 per pound for 

the cordierite honeycomb. Therefore, extruded honeycomb should be the best candidate for meeting the 

above criteria. 

Metal Honeycombs Made by Extrusion and Direct Reduction 

An extruded square cell honeycomb, similar in composition to Inconel 617, is shown in Fig. 4. 

This thin-walled honeycomb, at 18% relative density, is made with a two step process. The first step is 

the shape fabrication and the next step is the conversion of non-metallic precursors to the corresponding 

alloy (Fig. 5). Shape fabrication is primarily done by powder paste extrusion at ambient temperatures. 

Other fine powder shape forming processes can also be employed. Conversion is carried out in solid 

state at elevated temperatures very similar to the direct reduction process (DR). Direct reduction is a 

process for the production of metal directly from metal bearing ores or oxides by removing the associated 

oxygen at temperature below the melting point of materials involved. Reducing agent can be a gas (e.g., 

hydrogen or carbon monoxide) or other solids (e.g., carbon). During the reduction process, hydrogen 

reacts with the oxygen and forms water vapor, which is then removed from the system. The open 

structure of the honeycomb provides an efficient path for hydrogen and water vapor transport. 

In addition to honeycombs and hollow spheres, metal parts of a variety of geometries, such as 

rod, ribbon, tape, disk, and hollow ware have been fabricated with this process. They are used as test 

samples for the extraction of bulk material properties. 

Process Capability and Composition Limit 

Since the oxide particle sizes suitable for extrusion are small, on the average at -5 microns, thinwalled (e.g., 50 to 300 microns) honeycomb webs are feasible. A number of transition metal oxides and 

their mixtures for a wide range of engineering alloys have been successfully processed. The list of oxides 

includes Fe, Ni, Co, Cr, N Cu, Mo, W, Mn, Nb, etc. Specific engineering alloys made so far include 

Fel2Cr SS, Cu30Ni, Fel8NilOCo4Mo (maraging steel), Ni22Crl2.5Co9Mo (Inconel) and Fe32Ni5.5Co 

(Super Invar). For most oxide mixtures, complete reduction and 95 YO densification of the walls of the 

honeycomb occurred in a hydrogen atmosphere at less than1350" C. Above 1350" C, melting and 

collapse of the low density structure can occur. For better conversion efficiency, one would like to conduct 

the reduction at high homologous temperatures (TTT,) of the resultant alloy when feasible. 

Like the gaseous reducing agents, carburizing gases can be forced to flow through the 

honeycomb channels easily. Being able to add carbon to the alloy increases the composition flexibility 

greatly. Furthermore, honeycombs are better suited to survive the large shrinkage that occurs during the 

reduction process. Unlike other porous materials with random distribution of materials, the materials in 

honeycombs are uniformly and orderly distributed. The constant web thickness insures an equal coercion 

force to keep the material from separating or cracking, a phenomenon often observed where two 

neighboring unit cells were joined with a substantially smaller cross section. 

A critical issue related to the direct reduction process is the reducibility of the constituents 

involved. Elements such as Ti and AI, whose oxides are stable at these temperatures with pO2 level in 

the range of atm or higher, can not be introduced into the alloy as oxide. When needed, Ti and AI 

must be added by secondary processes such as pack bed cementation, chemical vapor deposition, or in 

the form of other compounds. These methods for introducing Ti and AI are being investigated. 

Reduction of oxides to the metallic state results in a large density increase, translating to a 

shrinkage typically on the order of 30 to 70 % by volume. Shrinkage can be an advantage for producing 

finer geometric features that would otherwise difficult or expensive to fabricate. For example, the cell 

density of a square cell honeycomb with 400 cell per square inch (csi) in the green (oxide) state increased 

to 900 csi after reduction and sintering (Fig. 6). State-of-the-art extrusion technology is capable of 

producing web thickness at around 100 microns, which translates to -70 micron web after reduction. 

Similarly cell size of 500 microns is projected to be feasible with this technology. Bulk density achievable 

controllably with this process can approach 8% of theoretical on the low end. 

3 
Other Process Issues 

The direct reduction process can be coupled with various fine powder fabrication techniques such 

as casting, coating, pressing to make other complex shapes. Direct reduction by hydrogen can also be 

replaced with thermal decomposition when metal carbides and hydrides are used as the precursors. For 

example, Ti hollow sphere foams were made using TiH2 as the raw material which was converted to Ti by 

thermal decomposition in an inert or vacuum environment. 

Another important feature of the honeycombs made by extrusion is the connectivity of the 

honeycomb with the outer surface. It is therefore quite feasible to include an integral skin layer on the 

structure. Hermeticity of the structure can be obtained by capping off the open ends to prevent water 

vapor or other elements from entering the structure. 

The ability to manufacture metal honeycombs from their oxides has cost advantages as well. 

Most oxides of transition elements are colorful and hence have been used as pigments, colorants, or 

inorganic dyes. Fine oxide powder of these oxides is readily available at very low cost. The cost 

differential between a metal oxide powder and its metal counterpart, if and when it is available, is usually 

better than a I-to-10 ratio. 

Metallurgy of Alloys via Direct Reduction 

The mechanical performance of honeycomb structures is directly related to the properties of the 

bulk material according to the Gibson-Ashby model. Therefore it is necessary to study the bulk material 

processed via the same route. Samples in the form of 1.8 mm diameter rods and 10 mm X 0.5 mm 

ribbons were fabricated for bulk property measurements. The important measurements of the bulk 

material are density/porosity, pore size/morphology, grain size/microstructure, yield strength, and 

modulus. Properties of two popular engineering alloys (Maraging 350 for high strength and lnconel 617 

for high temperature applications) were tabulated in Table I. Square cell honeycombs of the same 

compositions at 18% relative density were tested for mechanical properties reported in the next section. 

Other properties in the transient state such as compositional homogeneity, oxide-metal interface and 

presence of intermediate reaction compounds were also studied for better understanding of the 

conversion process. 

On the average, the porosity value derived from density measurement of the maraging steel 

composition was 5-7% and the lnconel 617 composition 7-15%. The higher porosity of the lnconel is 

associated with the high content of the hard-to-reduce Cr203 in the starting composition. First, the high 

vapor pressure of CrO, at high temperatures (e.g., >1200C) can lead to voids resulted from vapor phase 

transport. With a large amount of Cr203, reduction and subsequent sintering would require longer time to 

complete. Longer soaking at peak temperatures should lead to lower porosities [4], assuming no 

abnormal grain growth to occur. 

A sizable gap existed for both compositions in terms of their mechanical properties, comparing 

the direct reduction alloy with the regular alloy. First of all, porosity was believed to play a significant role. 

The low elongation at failure (e.g., 1-2% for the Maraging steel) was a good indication of brittle behavior 

of the alloy. For material to fail by brittle fracture, its strength decays as a function of porosity according 

to the following equation, 

where oP and 0, is the strength with and without pore, P is porosity and n is a constant with a typical value 

of 4 to 6.[5] Figure 7 shows a plot of the equation, showing porosity as a strong strength decay factor. A 

second cause was composition limitation of the process, leading to the absence of either AI or Ti from the 

chemical makeup. In the case of Maraging steel where minor constituent like Ti participates in age 

hardening by forming precipitates of Ni3Ti, the effect on strength when it is missing from the composition 

is obvious (Fig. 8). [6] The magnitude of strength decay was believed to be confounded by the two 

variables described above. 

op /o,, = exp(-nP) (9) 

Compression Testing of Monolithic Metal Honeycombs 

Compression experiments were conducted on honeycombs with 3x3, 5x5 7x7 and 10x10 cell 

arrays at two orientations (in-plane and out-of-plane) under both quasistatic and dynamic conditions. All 

experiments were conducted at room temperature. Quasistatic experiments were performed b 

compressing between planar parallel platens at an engineering strain rate on the order of 10 s . -4 .Y 

4 
Dynamic experiments were performed using a split Hopkinson assembly at engineering strain rates on 

the order of IO3 s”. In all cases, simple measures of nominal stress and strain were employed to reduce 

the data. The nominal stress is defined as current load divided by original cross-sectional area, and the 

nominal strain is defined as the magnitude of the change of length divided by the original length. Use of 

nominal measures is sufficient since the honeycomb is a structural rather than material element. These 

measures are also labeled as normalized load and displacement in plots. 

Honeycomb samples were prepared by extrusion and hydrogen direct reduction as described earlier 

in this paper. A typical 10x10 in-plane array of cells is shown in Fig. 9. For these honeycombs, the cell 

size d is approximately 1.5 mm. The relative density is about 0.18. Several types of defects arise from 

the extrusion process, including corrugation or waviness of cell walls with a period on the order of the cell 

diameter, separation of cell walls, and skew cells. 

Sample preparation included cutting sections of uniform length from extrusions in either the green 

state or after reduction. Green state machining was used to extract specimens of smaller dimension (e.g. 

3x3 or 5x5 cells) to examine constraint and scale effects. Samples were placed between two flat and 

parallel compression platens, either loosely or bonded with epoxy to explore effects of end fixity. Tests 

were performed at room temperature using displacement control. Samples were compressed under 

quasistatic loading until the densification strain was exceeded. 

Mechanical Properties of Extruded Honeycombs 

In Fig. 10, both out-of-plane and in-plane compression behavior of the lnconel 617 honeycomb 

are shown. The first minimum after initial buckling instability in the out-of-plane case is due to classical 

wall wrinkling near the platen that extends across the entire lateral dimension. In the in-plane case, each 

local minima of load owes to a collapse of a row of cells, and hence the marked undulations of load 

versus displacement, a progressive crush band type of behavior. Quasistatic collapse is highly 

inhomogeneous for the relatively ductile Ni-alloy walls, although cell wall fracture is observed in the postbuckling behavior of some of the walls. In contrast, Fig. 11 compares the significantly higher plateau 

stress of a honeycomb made with Fel8Ni Maraging steel composition, aging tempered to result in a 

precipitation hardened structure. This steel has much higher yield strength but lower ductility than the in 

situ Ni walls, producing a remarkable initial normalized buckling load (engineering stress) in the range of 

300400 MPa, and a plateau stress level of about 200 MPa. 

These 

fractures occur in rather random, distributed fashion, likely contributing to the excellent capacity for 

energy absorption. Typical plateau stress values for the out-of-plane case are much higher than AI open 

or closed cell foams. Although the behavior of these honeycombs is highly anisotropic, the energy 

absorption (area under nominal stress-strain curve up to the point of densification strain) is considerably 

higher than these random AI foams, even for in-plane loading conditions. 

Furthermore, the in-plane behavior of the Maraging steel exhibits less variation of the plateau stress 

level. It was found in quasistatic experiments that there is a certain dimension below the results become 

specimen size dependent; this dimension appears to require more than about seven cells to achieve. For 

smaller arrays, the plateau stress decreases, possibly due to a lack of constraint on the propagation of 

crush or localization bands that emanate from isolated defects. Figure 12 compares the energy 

absorption for both in-plane and out-of-plane compression of Maraging steel honeycomb relative to other 

low density metal foams; the out-of-plane energy absorption is orders of magnitude higher than common 

low density metal foams with comparable relative density. Figure 13 compares the dynamic (IO3 s-’) 

compressive response of Ni-alloy honeycombs loaded out-of-plane with the quasistatic behavior. An 

increase of impact energy absorption of approximately 40% is observed, depending on aspect ratio. It 

appears that more uniform compaction is achieved in the dynamic case. 

Cell wall fracture dominates the compressive response of the Maraging steel honeycombs. 

Concluding Remarks 

Low density metal honeycomb is a highly functional geometry in terms of its density adjusted 

property. This technology has the advantage over conventional metal fabrication techniques for making 

monolithic honeycomb. The direct reduction process is proven feasible for making quality alloys with good 

mechanical properties. Specific energy absorption at orders of magnitude higher than common low 

density metal foams is achieved. It is made possible with the combination of honeycomb geometry, high 

strength alloy (maraging steel) composition and powder paste extrusion. Three processing issues are 

5 
identified for further improvement. There are, namely, reduction of processing induced defects, full 

densification of wall material, and addition of essential trace elements. The projected strength is 660 MPa 

for a maraging steel (Maraging 350) at a density of 1.5 gm/cc once improvement agenda Is fully 

implemented. 

480 C for 3-6 hrs 

Acknowledgement 

This work is sponsored by DSO of DARPA (N00014-99-1-1016) and ONR (N0014-99-1-0852) 

and monitored by Dr. L. Christodoulou of DARPA and Dr. S. Fishman of ONR. The assistance by Prof. 

Min Zhou of ME/Georgia Tech in Hopkinson bar testing is appreciated. 

(YO) 

480 C for 5 hrs I Heat Treatment 1 1200 c 1175 C 

References 

1. Ashby, M.F., Evans, A., Fleck, N.A., Gibson, L.J., Hutchinson, J.W. and Wadley, H.N.G., Metal Foams: 

2. Gibson, L., Ashby, M.F., Cellular Solids: Structures and Properties, 2nd Ed. Camnbridge University 

3. Bart-Smith, H., Bastawros, A.F., Mumm, D.R., Evans, A.G., Sypeck, D.J., Wadley, H.N.G., 

A Design Guide, Butterworth-Heinemann, Boston, 2000. 

Press, Cambridge, UK, 1997. 

"Compressive Deformation and Yielding Mechanisms in Cellular AI Alloys Determined Using X-ray 

Tomography and Surface Strain Mapping", in Porous and Cellular Materials for Structural Applications, 

Edited by Schwartz, D.S., Shih, D.S., Evans, A.G., Wadley, H.NG., MRS Symp. Proc. V. 521, 

Warrendale, Pa, 1998. 

and Titanium Hollow Sphere Foams", in Porous and Cellular Materials for Structural Applications, 

Edited by Schwartz, D.S., Shih, D.S., Evans, A.G., Wadley, H.NG., MRS Symp. Proc. V. 521, 

Warrendale, Pa, 1998. 

1976. 

4. Hurysz, K.M., Clark, J.L., Nagel, A.R., Hardwicke, C.U., Lee, K.J., Cochran, J.K., Sanders, T,H., "Steel 

5. Kingery, W.D.. Bowen, H.K., Uhlmann, D.r., lntroductin to Ceramics, 2"d Ed. John Wiley & Sons, Inc. 

Table I. Comparison Between Conventionally Processed And Direct Reduction Alloys 

6 
Fig. 1. Examples of Metallic Low Density Structures: (a) Closed Cell AI Foams-ALPORAS by Shinko 

Wire, (b) Reticulated AI Foams by ERG, Inc., (c) lnconel Hollow Sphere Foam By Georgia Tech, (d) 

Maraging Steel Honeycomb by Georgia Tech, (e) Lattice Block Material by JAMCORP. 

Comparison of Strength of Honeycomb and Foams 

Fig. 2. 

Ti64, and AL as a Function of Material Density 

Comparison of Compressive Strength of Open and Closed Cell Foams to Honeycomb for SS, 
Fig. 3. Triangular Cell Honeycomb for Improved Properties in the Transverse Direction 

1 

Fig. 4. lnconel 617 Honeycomb at 18% Relative Density, Featuring 150 JJ Web 

Thickness and 1500 p Cell to Cell Spacing 
Step One: Shape Fabrication 

Honeycomb Drying Extrusion - 

I 

Step Two: Direct Reduction 

Fin is hed 

Metal Part 

Direct 

Reduction 

Fig. 5. Oxide Powders to Monolithic Metal Honeycomb 
Fig. 6. Fel2Cr Honeycomb at 900 Cells per Square Inch 
0.9 

0.8 

6- 0.5 

0.4 

0.3 

0.2 

0.1 

1 

1 

n=6 

0 0.05 0.1 0.15 0.2 0.25 

P: Volume Fraction Pores 

Fig. 7. Effect of Porosity on Strength 
Fig. 8. Effect of Ti Content on Tensile Strength of Maraging Steels 

Containing 18% Ni, 8 to 12% Co, and 4 to 5% Mo 
Relative Density: p* / p,,= 2t / d-(t / d)’ 

t = web thickness 

d = cell size 

Fig. 9. Representative In-Plane Cross Section of Extruded and Reduced 

Honeycomb 
Ni-alloy Longitudinal Compression 

300 

250 

50 

0 

100 

90 

80 

20 

10 

0 

... ... 

0 01 02 03 04 05 06 07 08 09 0 01 02 03 04 05 06 07 08 

Normlllzbd Diaplwwmont Nonnalizbd Diaplrmmt 

Fig. 10. Out-Of-Plane Compression Of I:? Aspect Ratio 6x6 Cell Ni-Alloy Honeycomb 

Specimen (Left), And (Right) In-Plane Compression Of A 7x7 Square Array Honeycomb 

10x10 cell ~bix, 

Fig. 1 1. Relative Compression Behavior For A Maraging Steel Square Cell 

Honeycomb With An In Situ Wall Yield Strength Of About 1 .I Gpa And Ni-Alloy 

Honeycomb. 
-I "- 

Fig. 12. Comparison Of Energy Absorption Per Unit Mass Versus Plateau Stress For A 

Range Of Low Density Foams For Quasistatic Loading. The Out-Of-Plane Crushing Of 

Maraging Steel Honeycombs Essentially Lies On The Extrapolated Line Representing The Upper 

Bound Solution For Energy Absorption Based On Collapse Of Thin-Walled Tubes (Ashby et al.. 

2000). 
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75 

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25 

t 

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(Dynamic) Represent Specimens With 1 :1 And 1 :2 Aspect Ratios, Respectively 
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Identification of High Performance, Low Environmental Impact Materials and Processes 

Using Systematic Substitution (SyS) 

Patrick M. Dhooge and Jonathan S. Nimitz 

Environmental Technology and Education Center (ETEC) 

4500-B Hawkins St. NE 

Albuquerque, NM 87 109-45 17 

Phone: (505) 345-2707 

http:l/www .etec-nm.com 

-1 ljnimi tz @ etec-nm.com I 

INTRODUCTION 

Process analysis can identify opportunities for efficiency improvement including cost 

reduction, increased safety, improved quality, and decreased environmental impact. A thorough, 

systematic approach to materials and process selection is valuable in any analysis. New 

operations and facilities design offer the best opportunities for proactive cost reduction and 

environmental improvement, but existing operations and facilities can also benefit greatly. 

Materials and processes that have been used for many years may be sources of excessive 

resource use, waste generation, pollution, and cost burden that should be replaced. Operational 

and purchasing personnel may not recognize some materials and processes as problems. Reasons 

for materials or process replacement may include quality and efficiency improvements, excessive 

resource use and waste generation, materials and operational costs, safety (flammability or 

toxicity), pollution prevention, compatibility with new processes or materials, and new or 

anticipated regulations. 

Very often, material and process substitution is performed in a nonsystematic manner. 

While a material or process may be identified as a problem, often the substitution decision is 

made “on the fly.’’ Personnel may rely on vendor recommendations and specify substitute 

materials and processes without a systematic analysis of alternatives. Such decisions may lead to 

sub-optimal performance, increased waste generation, higher life cycle costs, and increased risks. 

The authors cannot stress too greatly the need for a thorough, systematic evaluation of an 

operation’s materials and processes with the goal of decreased cost, waste, and pollution. If 

replacements are to be made, it is logical to identify the best possible replacements 

systematically to minimize life cycle cost, risk, and the need for future replacements or 

modifications. The so-called “rule of ten” applies to this situation. That is, if a change made at 

the design stage costs $ I , that change at prototype stage costs $10, and the change at operational 

stage $100. 

Many factors must be considered in most materials and process substitutions. The 

number of alternatives and their different characteristics can be overwhelming if a methodical 

system of evaluation is not used. Additionally, it is uncommon that one or two personnel will be 

able to understand all the implications of alternatives’ characteristics. There should be 

involvement from team members with good knowledge of the material or process use, materials 

properties, engineering, health and safety, operations management, and waste management. 

Involvement of these personnel also helps ensure acceptance of the new material or process. 
The net result of a systematic evaluation, as described below, is a small set of top-ranking 

alternatives to evaluate in the laboratory and, after further downselection, prototype or pilot 

testing. Candidates should be tested against the current material or process before final selection 

is made, to eliminate alternatives that have unanticipated disadvantages, and to identify the best 

option from those with similar evaluation scores. Again in the evaluation phase, personnel from a 

number of disciplines, including the operations personnel, should be involved to obtain the 

widest possible input on the advantages and disadvantages of the selections. Once sufficient 

testing is completed, the team makes the final choice. 

Properly evaluating substitute materials and processes should be part of a larger process 

for achieving high quality and environmental excellence. Quality and environmental 

management tools include process mapping; life cycle cost analysis; an effective employee 

involvement program; identification of opportunities for improvement; action plan development 

and implementation, including use of evaluation methods such as SyS; quantitation of results, 

management by fact; and a continuous improvement program. Achievement of quality and 

environmental excellence, and associated goals such as energy efficiency are being recognized 

through state and federal programs such as Energy Star, Climate Protection, and New Mexico’s 

Green Zia. Such recognition motivates organizations to additional achievement and is good 

publicity, but more importantly the programs instituted result in improved efficiency and cost 

savings. 

DESCRIPTION 

The authors have developed a systematic substitution (SyS) process applicable to a wide 

variety of materials and processes. SyS incorporates a refinement of a technique reported 

previously (Nimitz a). While SyS is certainly not unique, and the weighted ranking matrix for 

scoring candidates has been used for many years, we have found the overall SyS process highly 

effective in identifying high performance substitutes without being overly complex and costly. 

The logical, methodical SyS process identifies and ranks candidate materials and 

processes for given applications. The process has been used successfully in several projects for a 

variety of applications (Kuchar, et al.; Nimitz b-g, Shell, et al., Toohey, et al.). The steps of the 

SyS process have been given in a previous paper (Nimitz h) but are listed here in somewhat more 

detail and for completeness. 

Determine all requirements, including performance; compatibility; stability; regulations; cost 

sensitivity; safety (toxicity and flammability); and maximum allowable environmental 

impact. Establish the advantages and disadvantages of the current material or process versus 

the requirements. The extremes of the requirements define the limits of acceptable properties 

for a candidate replacement. Team members (e.g., floor personnel, production engineers, 

ES&H, waste management, and operations management) should be included in this process 

for their valuable input and “buy-in” to ensure acceptance of the ultimate results. 

Develop a list of evaluation criteria based on the requirements. In SyS, criteria are often 

grouped under the main headings of physical properties, performance, toxicity, compatibility, 

environmental effects, and cost, all of which may be further subdivided as desired. There are 

obviously some differences between evaluating a process versus a material. For a process, 
the toxicity heading may have grouped under it the toxicities of all the materials involved in 

the process. Performance criteria may include estimated energy efficiency, throughput, 

product quality, ease of use, and any existing test data for similar applications. Physical data 

may include (for process equipment) dimensions and weight, and (for materials) molecular 

weight, density, strength, ductility, wear resistance, vapor pressure, viscosity, heat capacity, 

thermal stability, electrical resistivity, etc. Compatibility and other chemical data for 

materials may include flammability and compatibility with metals, plastics and elastomers, 

and other chemicals. Environmental criteria for materials may include factors such as 

atmospheric lifetime, ozone-depletion potential (ODP), global warming potential (GWP), 

total equivalent warming impact (TEWI), volatile organic compounds (VOCs), regulatory 

status, waste disposal, and air and aquatic toxicity of materials and wastes. Environmental 

criteria for processes may include materials criteria plus waste generation, resource use 

(including utilities), emissions, and potential severity of accidental spills and releases. 

Toxicity criteria for materials may include exposure limits, carcinogenicity, teratogenicity, 

odor, and sensitization. 

(3) Develop an initial list of candidates for consideration. Sources for candidate materials may 

include chemical databases (e.g., Chemical Abstracts Service, Beilstein, Gmelin), relevant 

literature, and vendor information. Sources for candidate processes may include personnel 

knowledge; scientific and technical journals; vendor literature; U.S. and international patents; 

government laboratories and publications; and information on competitors and benchmark 

organizations. If possible, include known competitors’ and benchmark organizations’ current 

materials or processes for comparison. 

(4) Assign relative weights to evaluation criteria on a scale of one to ten points based on which 

are judged more important and more accurately known. Other factors being equal, higher 

uncertainty means lower confidence in data values and assignment of a lower relative weight. 

This step can be one of the most involved parts of the SyS process. The working team must 

reach consensus on the weightings before the evaluation process proceeds, and this 

consensus should be documented. If the weightings are later found not to reflect the true 

requirements for some unanticipated reason, they can be changed by consensus, although 

such changes should be made only when necessary. 

(5) Collect and tabulate properties of reference materials or processes, and the candidate 

replacements. Reference materials or processes include the material or process to be replaced 

and corresponding materials or processes used by competitors or benchmark organizations. 

Estimate unreported properties as needed, and assign realistic uncertainties to the 

estimations. Estimation of unreported properties involves some uncertainty. The actual 

properties could be better or worse than estimated. Using the worst possible value may 

eliminate a good candidate. Using the estimate may overestimate the value of the property. It 

has been our experience that at this stage it is better to keep a marginal candidate than to 

eliminate a good candidate, so the estimate is typically used as is. The uncertainty should be 

listed with the value. 

(6) If reasonably accurate numerical values are available for the data, develop a point scale of 0- 

10 for data values for each criterion, where 0 is least attractive and 10 is most attractive, and 
assign scores for each candidate for each criterion. If numerical values are not appropriate or 

not available, assign subjective descriptions to the value of each criterion for each candidate 

(e.g., very high, high, moderately high, moderate, moderately low, low, or very low), then 

assign numerical values to the subjective descriptions (e.g., very high = 10, high = 8 etc.). 

First-time SyS users should probably use a linear mapping of points to criteria values. 

However, in this step experienced SyS users can add a certain amount of sophistication. The 

mapping of numerical values to the point scale need not be linear. As an example, assume a 

substitute cleaning solvent is being sought. For the substitute cleaning solvent the allowable 

viscosity range is 0.5 to 5.5 centipoise (cP). On a linear scale, a solvent with a viscosity of 2 

CP will get a 7 score and a solvent with a viscosity of 3 CP will get a 5. However, because 

low viscosity is valued for both good penetration 

viscosity of 2 CP should get a proportionately higher score because low viscosity is important 

for two reasons. The scoring function can be a polynomial function, an exponential function, 

some other type of function, or even values chosen manually. In this example, the function 

should result in a value of 0 at 5.5 and a value of 10 at 0.5, and it should have higher values 

than a linear mapping when viscosity is low. What function is used to map point scores 

depends on the relative importance of individual values within the allowable value range. 

This is different from the weightings assigned in Step 4 above. The weightings reflect the 

importance of the criteria against each other. Score mapping curves are used to adjust the 

scores of values within a criterion. Score mapping is an intracriterial process. 

effective draining, the solvent with a 

(7) Sum the products of the criteria weights times the individual scores for each candidate to 

give weighted rankings. Any spreadsheet program can be used for this step. Table 1 shows 

the type of table used for property tabulation and scoring. 

(8) Evaluate several of the highest-ranking candidates in the laboratory and at pilot scale, then 

test the highest-ranked candidate in the facility. 

Table 1. Sample Table for Property Tabulation and Scoring 
RESULTS AND DISCUSSION 

The SyS process has identified good substitute materials and processes in a variety of 

applications. Several examples are discussed below. 

Space Shuttle Heat Transfer Fluid 

Shuttle. However, HCFC-21 is a Class 2 ozone-depleting substance whose production has been 

halted under the Montreal Protocol and HCFC-21 has relatively high toxicity with a Threshold 

Limit Value (TLV) of 10 ppmv in air. Its high toxicity complicates Space Shuttle maintenance 

operations. An environmentally friendly, nonflammable, low toxicity, inexpensive heat transfer 

fluid for potential use in the Space Shuttle and other applications was desired. Ideally, the 

replacement should be a drop in or near-drop in replacement for HCFC-21. 

The hydrochlorofluorocarbon (HCFC)-2 1 is used as a heat transfer fluid in the Space 

Working with NASA and contractor personnel, ETEC identified the requirements for the 

replacement fluid, screened over 100 candidates, downselected to the best ten candidates, and 

finally selected the three best candidates. NASA and contractor personnel eliminated one of the 

three best candidates because, although it was not flammable and would have saved significant 

launch weight, it was combustible at high temperature. The heat transfer rates of the two 

remaining candidates, HFC-245fa and HFE-7 100, were calculated for the Space Shuttle system 

and HFC-245fa was identified as the best candidate. HFC-245fa was estimated to transfer heat 

about 8 % better than HCFC-2 1 under typical Space Shuttle cooling loop conditions. HFC-245fa 

is considerably less toxic than HCFC-2 1. Although exposure limits have not yet been officially 

set, HFC-245fa is expected to have a Permissible Exposure Limit (PEL) of 500 to 1000 ppmv in 

air. HFC-245fa is compatible with all Space Shuttle cooling loop materials, and it would save 

about 8 kg launch weight versus HCFC-2 1. HFC-245fa will also soon be in bulk production by 

Honeywell (formerly AlliedSignal) as a replacement for HCFC blowing agents in the 

manufacture of rigid, closed cell polymer insulating foams, and its cost is expected to be $8 - $10 

per kilogram. 

Following identification of HFC-245fa as the top candidate, ETEC evaluated its heat 

transfer rate versus HCFC-2 1 at bench scale in a circulating heat transfer loop with tubing size, 

linear flow rate, pressurization, and warm and cold side temperatures matched to the Space 

Shuttle cooling loop conditions. Multiple runs were made with HCFC-2 1 and HFC-245fa. 

Relative standard deviations were 1.2% or less, and the results showed a heat transfer rate for 

HFC-245fa that was 12 - 13% greater than HCFC-21’s heat transfer rate. 

Cleaning 

In a project for the U.S. Air Force, ETEC worked with BDM Federal, Inc. to review use 

of a large vapor degreaser used to clean aluminum honeycomb for aircraft wing repair. The 

vapor degreaser used 1,1,1 -trichloroethane (TCA). Because TCA is being phased out under the 

Montreal Protocol as a Category 2 ozone-depleting substance, a new cleaning method was 

desired. The new method had to be environmentally friendly, use a nonflammable, low toxicity 

cleaning agent, leave no corrosive residues, and clean aluminum honeycomb adequately to give a 

surface that would bond strongly with epoxy. A review and evaluation of possible cleaning 

methods (nonaqueous, semi-aqueous, and aqueous) showed the attractiveness of aqueous 

cleaning. Approximately 50 aqueous cleaners were evaluated. Note that in this project there were 
two phases to the evaluation, the evaluation of types of cleaning (i.e., nonaqueous, semi-aqueous, 

and aqueous) then the evaluation of cleaners (50 aqueous cleaners). This project involved 

evaluation of both a process and a material, and such evaluations can often be logically divided 

in this manner. The top three aqueous cleaner candidates were evaluated in the laboratory. 

Laboratory evaluation involved tests of cleaning abilities, adequate penetration of the 

honeycomb, corrosion during cleaning, corrosive residues as revealed by accelerated aging, and 

compatibility with nondestructive crack-detection methods (no residues left in cracks to interfere 

with dye penetrant). An aqueous spray cleaning system was identified as the most attractive 

alternative to vapor degreasing for aluminum aircraft honeycomb. This custom system was 

designed and built, and is now in place at the National Defense Center for Environmental 

Excellence (NDCEE). 

In a project for the U.S. Air Force Research Laboratory, a new group of nonaqueous, 

nonflammable, low atmospheric impact solvents was evaluated for aircraft maintenance critical 

cleaning operations. The solvents were perfluoro-n-propyl iodide ( 1 -C3F,I), peffluoro-n-butyl 

iodide ( 1 -C&J), and perfluoro-n-hexyl iodide ( 1 -C6;13I) and their blends with conventional 

solvents. Evaluation of physical properties, stability, compatibility, toxicity, and cleaning 

abilities identified perfluoro-n-butyl iodide, given the trade name Ikon' Solvent P, as the topranking iodofluorocarbon (IFC) solvent. Perfluoro-n-butyl iodide has physical properties and 

cleaning abilities very similar to CFC- 1 13, and is superior to CFC-I 13 for removing 

perfluorinated greases. Its rat 4-hr LCso of 14,000 ppmv is considerably higher than that of 1,1,2- 

trichloroethane (2,000 ppmv) and approximately the same as 1,1,1 -trichloroethane and 

trichloroethylene ( 18,400 and 12,500 ppmv, respectively). Perfluoro-n-butyl iodide is Amesnegative and is not clastogenic by the human lymphocyte test. Because IFCs photolyze quickly 

in sunlight to simple, natural products, peffluoro-n-butyl iodide has an atmospheric lifetime of 

only about 2 days, giving it essentially zero (~0.0025) ozone-depletion potential (ODP) and an 

extremely low global warming potential (GWP) of less than 2 (relative to COz = 1 ) for a 100 

year horizon. NASA Kennedy Space Center (KSC) sponsored an additional effort to determine 

perfluoro-n-butyl iodide's potential suitability as a cleaner for oxygen systems. The new solvent 

was found to be quite compatible with oxygen and an excellent candidate for oxygen system 

cleaning, particularly as it is even more effective than CFC-113 at removing fluorinated greases. 

The project sponsored by the Air Force Research Laboratory also investigated thirty-six 

conventional flammable solvents to blend with IFCs. The conventional flammable solvents were 

also evaluated using SyS, and were scored on physical properties, flammability, thermal stability, 

estimated fractionation from the IFCs, environmental impact, toxicity, and cost. The result of the 

SyS evaluation was a list of 19 high ranked potential blends. When these potential blends were 

evaluated in the laboratory two nonflammable near-azeotropes were discovered, one of which 

was practical as a solvent blend. The blend has been given the trade name Ikon' Solvent M. 

Ikon" Solvent M's cleaning effectiveness is not quite as good as Ikon' Solvent P for some soils, 

but it is less expensive and will have a higher exposure limit. 
Thrust Vector Control Fluid 

dibromotetrafluoroethane) as a liquid injection thrust vector control (LITVC) fluid. This fluid is 

injected into the exhaust stream, where it decomposes to form a large volume of gas that deflects 

the exhaust stream to steer the missile. Because of the phaseout of production of Halon 2402 as a 

Category 1 ozone-depleting substance under the Montreal Protocol, a replacement had to be 

found. It was most desirable that the replacement use the existing hardware to avoid expensive 

redesign and testing. ETEC worked with GenCorp AeroJet to identify the required properties, 

examine an initial list of over 1000 candidate replacements, model performance, downselect the 

candidates, and choose the most attractive candidate for performance testing. The material 

selected was perfluorohexane, which has excellent stability and compatibility, low toxicity, and 

acceptable performance. Although in some applications perfluorocarbons are released to the 

atmosphere and cause concern about global wanning, in this application they undergo 

combustion and are not released to the atmosphere. 

The Minuteman Stage I1 rocket was designed to use Halon 2402 ( 1,2- 

Refrigerants 

In a project for NASA KSC, SyS was used to identify top-ranking components for new 

high performance, nonflammable, zero ODP, stable, compatible, azeotropic or near-azeotropic 

refrigerant blends to replace ozone-depleting chlorofluorocarbon (CFC) and HCFC refrigerants 

phased out or facing phaseout under the Montreal Protocol. Ozone-depleting refrigerants that 

could be replaced include R-12, R-22, R-500, R-502, and R-123. R-12’s production has already 

been phased out in developed countries, R-22’s phaseout will start in 2003, and R- 123 will 

shortly follow R-22. R-500 is a blend that contains R-12 and R-152a. R-502 is a blend that 

contains R-22 and R- 115. Available substitutes such as R- 134a, R-404A, and R-410A do not 

have as high innate energy efficiency and performance as desired. 

Approximately 100 possible refrigerant components were screened and ranked. 

Fractionation and performance of potential blends were modeled using ETEC’s proprietary 

AZEO and COOLS computer programs and the National Institutes of Standards and Technology 

(N1ST)’s Refprop‘ refrigerant properties database. From the screening a set of attractive 

candidate components were selected. The candidate components were then blended, tested for 

flammability and performance, and developed into Ikon‘ Refrigerants A, B, and C. These 

refrigerants have attractive physical properties, zero ODPs, and low total equivalent warming 

impacts (TEWIs). They appear suitable to replace R-12, R-22, R-500, R-502, R-123, R-134a, R404A, R-407C, and R-4 IOA in residential refrigerators, residential and commercial air 

conditioners, commercial and industrial water chillers, commercial and industrial refrigeration, 

industrial process coolers, and other cooling and refrigeration equipment that has relatively low 

leak rates. From all data known so far, the three refrigerants appear superior in performance and 

environmental properties to any other available alternatives. 

Performance tests on Ikon‘ A and Ikon” B in a 1.75 ton water chiller test bed at ETEC, a 

compressor calorimeter at Oak Ridge National Laboratories, a 20 ton air conditioning unit at 

NASA Kennedy Space Center, and a residential refrigerator have shown that both have 10-15% 

higher energy efficiency and 10- 15% greater volumetric cooling capacity than R-12 and R- 134a. 

Ikon’ A and IkonE B also have a total of over five years run time in several refrigerated transports 

(“reefers”) at Dole Fresh Fruit with no indications of incompatibility. Both Ikonz A and Ikon‘ B 
have been approved under the U.S. Environmental Protection Agency's Significant New 

Alternatives Policy (SNAP) program as ozone-depleting refrigerant replacements in multiple 

applications including residential refrigerators, air conditioning, refrigerated display cases, and 

water chillers. Initial performance tests on Ikon'-" C in ETEC's 1.75 ton water chiller test bed show 

that it has about 9S% of the capacity of R-22, and 4-596 higher energy efficiency than R-404A, R407C, or R-4 10A. Ikon" C has a low evaporator temperature glide and operating pressures almost 

identical to R-22. Ikon" C may be usable as a direct replacement in R-22 equipment with an oil 

change, and can definitely be used as a replacement with a compressor change. A SNAP 

application has been prepared for Ikon" C. 

Firefighting 

effective replacement for Halon 1301 for fire suppression in unoccupied areas. Subsequent 

testing showed excellent performance and environmental properties, and this chemical was 

approved as a halon replacement for use in unoccupied areas under the SNAP program. CFJ is 

being installed in a variety of facilities in Australia and the Far East, and has recently been 

named the preferred choice as a substitute fire suppression agent for the F- 16 fuel tanks. 

In a project for the U.S. Air Force, trifluoromethyl iodide (CF3I) was identified as an 

CONCLUSIONS 

A systematic approach to materials and process substitution is valuable for product 

quality improvement, process efficiency improvement, cost reduction, increased safety, waste 

and resource use reduction, and pollution prevention. The SyS process has proven successful in 

identifying high performance, energy-efficient, low life cycle cost, safe, and environmentally 

friendly replacement materials and processes for both highly specific and more general 

applications. 

ACKNOWLEDGEMENTS 

The funding for the material and process development work described in this paper was 

provided by the U.S. Air Force, the U.S. Air Force Research Laboratory, BDM Federal, Gencorp 

Aerojet, NASA Kennedy Space Center, and the U.S. Environmental Protection Agency. We 

would like to thank Dr. Carl E. Snyder of the U.S. Air Force Research Laboratory, John Carroz 

of the U.S. Air Force, Tony Harriso~i of Gencorp Aerojet, Wayne Kuchar and John Toohey of 

BDM Federal, Dr. Jacqueline Quinn of NASA KSC, and Michael Bender of the U.S. EPA for 

their valuable technical support during the efforts. The Ikon' refrigerants and solvents are 

patented products of the Ikon Corporation. 

REFERENCES 

Kuchar, W., Gordon, B., Bennett, D., and Nimitz, J., "Aqueous Cleaning of Aluminum 

Honeycomb," Fifth International Workshop on Solvent Substitution, Phoenix, AZ, Dec. 6-9, 

1994. 

Nimitz a: Nimitz, J. S., and Shell, V., "How to Find Safe, Effective, Environmentally Sound 

Alternative Chemicals," Proceedings of the 5th Annual New Mexico Air and Waste 

Management Technical Meeting, Albuquerque, NM, October 3 1, 199 1. 
Nimitz b: Nimitz, J. S., and Lankford, L. H., “A New Class of Nonflammable, 

Environmentally Safe Solvents,” Fourth Annual International Workshop on Solvent 

Substitution, Phoenix, AZ, Dec. 7-10, 1993. 

Nimitz c: Nimitz, J. S., High-Performance, Environmentallv Sound Replacements for Halon 

1301, Prepared for McClellan AFB under contract F04699-93-C-0004, December 1993, 

Nimitz d: Nimitz, J. S., “Trifluoromethyl Iodide and its Blends as High-Performance, 

Environmentally Sound Halon 1301 Replacements,” Halon Options Technical Working 

Conference, University of New Mexico, Albuquerque, NM, May, 1994. 

Nimitz e: Nimitz, J. S., Olsen, K., Glass, S. M., Dhooge, P. M., and McCullough, E. T., 

Development of Nonflammable, Environmentally Compliant Fluoroiodocarbon Solvents: 

Phase I1 Final Report, prepared for Wright Laboratories under U.S. Air Force Contract 

Number F33615-95-C-5026, December 1999. 

Nimitz f: Nimitz, J. S., Glass, S. M., McCullough, E. T., and Dhooge, P. M., “Applications 

Tests of Energy Efficient, Environmentally Friendly Refrigerants,” 2 1 St National Industrial 

Energy Technology Conference, May 12 - 13, 1999, Houston, Texas, available through 

Texas A&M University Energy Systems Laboratory, College Station, Texas. 

Nimitz g: Nimitz, J. S, Dhooge, P. M., Waldrop, S. D., McCullough, E. T., and Glass, S. M., 

“High-Performance Environmentally Safe Refrigerants: Phase I1 Final Report,” 

Environmental Technology and Education Center, prepared for NASA Kennedy Space 

Center under contract NAS 10-98028, March, 2000. 

Nimitz h: Nimitz, J. S., Dhooge, P. D., and Glass, S. M., “Successful Environmentally 

Friendly, High Performance Substitute Materials for Manufacturing and Facilities,” 

Proceedings of the SAE Aerospace Manufacturing Technology Conference, June 2-4, 1998, 

Long Beach, California, available through SAE International, Warrendale, PA. 

Shell, V., Harrison, A., and Nimitz, J., “Finding an Environmentally Acceptable 

Replacement for Freon 1 14B2 (Halon 2402) That Meets Minuteman LITVC Performance 

Criteria,” Proceedings of the 1994 NATO Advisory Group for Aerospace Research and 

Development, Norway, August 29, 1994. 

Toohey, J. A., Kuchar, W. E., and Nimitz, J., Final Technical Report: Alternative Process for 

Cleaning Aircraft Honeycomb, prepared for U.S .A.F. Wright Laboratory WL/MTX under 

contract F42600-90-D- 1 140RZ01, BDM/ABQ-95-AQ-0445-TR, August 1995. 

ETEC 93-3 
SELECTION CRITERIA FOR ALTERNATE TECHNOLOGIES, 

AS A METHOD OF HAZARDOUS WASTE MINIMIZATION 

Authored by: Eric Lethe 

Inland Technology Inc. 

401 East 27'h Street 

Tacoma. WA 98431 

(2531 .---, 383-1 177 ~ ~~ ~~ 

inland @inlandtech.com I I 

The need for environmentally compliant processes and materials in the Aerospace Industry grows more 

pressing every day. As the need for these processes grows, so grows the confusion regarding the selection and 

implementation of these new methods and materials. 

In the past, price and traditional procedure were the only criteria by which a material was procured. Speed 

and compliance with OEM specification governed how things were done on the shop floor. With the advent of the 

environmental regulations, processes are being examined all across the globe. In many of the larger Aerospace 

companies, the chief environmental officer has as important a role as the comptroller or CFO. Environmental 

managers are often not chemists or aerospace line mechanics. as typically. the environmental manager is skilled in 

the policies of waste disposal, spill clean up, or remediation. 

The methods whereby a company can minimize the generation of hazardous waste remain less known. 

Often the examination of possible alternate techniques and materials are left for the last minute, or are conducted by 

personnel who are unfamiliar with how to make changes work. This is usually a recipe for failure in the 

implementing of anything new. 

This paper will suggest methods for selection of alternative products and processes in a clear and organized 

manner. Salient points will be: 

1. Process Examination 

3. Material Selection 

3. Steps For Successful Implementation 

4. Possible Impediments 

5. How to Avoid Risky Alternatives 

It will focus on procedures that will assist in the decision making process, and hopefully be of use in the 

choosing of environmentally sound equipment, chemicals, and methodologies. 

In the past, price per gallon and traditional procedure were the only criteria by which a material was 

procured. Speed of delivery and compliance with OEM specification governed how and what was procured. 

Hazardous chemicals were used traditionally because they WORKED. However. with the advent of environmental 

regulations, the Environmental Affairs Director, the shop manager, and the floor personnel are often at odds with the 

Regulations on one side, and the standard operating procedures called out in the technical manuals on the other. 

This condition causes a sense of desperation or hopelessness. which is counter productive to any examination of new 

technology. It is critically important that an organized method of examination be in place before any discussion of 

the testing of alternative materials. Each process. which uses hazardous chemical, needs to be examined to 

determine if that process itself, is necessary. This examination affords the Environmental Officer an intimate 

knowledge of the processes for which that officer will be making recommendations. In that way, the problem of 

changes to standard procedure can be addressed with less resistance. 

When the environmental concerns are being addressed, the engineers who would like to introduce an 

alternative are thwarted by a need for a substitute. which must perform "identically" to the original material. The 

"chemical physics" stand against any legitimate candidate material being identical. 
As a rule, the faster a chemical evaporates the greater the potential for there to be a hazard associated with 

that chemical‘s use. whether the hazard is ozone depletion potential, toxicity, smog formation potential, or 

flammability. In the very greatest of likelihood, the alternative candidate material will be slower in evaporation. 

This is an important concern when selecting candidate materials, since it is quite possible to be in a situation where 

one hazard is substituted for one that is even greater or more expensive to deal with. In the search for successful 

solvent substitutes. it is critically important to select a course of action based upon each process, as opposed to the 

focus of attention being each chemical. 

MEK for example, is a solvent used in so many applications that to say “1 want a replacement for MEK” is 

far too ambiguous to begin a concerted effort to examine candidate replacements. Is the MEK used for surface 

cleaning prior to painting, prior to welding, cleaning of painting equipment, removal of adhesive, or thinning and 

diluting paints or shoe polish’? A metaphor I often use to describe this situation is the consideration of a 

combination lock. Randomly selecting numbers seldom achieves the opening of the lock. A skilled locksmith. 

armed with the knowledge of the make, model, year of manufacture, and other pertinent data will have a far easier 

time opening that lock. 

Using the premise that a substitute will behave differently, and not for 4 of the applications of the original 

material, will facilitate an examination of the processes that use this material. The resulting “needs assessment” will 

evaluate what will work on a process-by-process basis. There are occasions when the application differences are 

subtle, and the substitute materials are not needed to be absolutely specific for each application. The bulk of this 

substitution effort will be on an application specific basis. There is no single answer. I f there were, the hazardous 

solvents would have been phased out years ago. 

What is called for is an organized method for determining the applicability of candidate materials. based on 

a ”needs assessment” of the affected processes. Part of the initial assessment must be a determination of whether a 

material is needed for that application. The alternative may be a change of process that eliminates the need for 

cleaning of the candidate part altogether. 

Steps for Successful Solvent Substitution: 

1. Identifv target solvent: Make a priorities list of those solvents that are a hazardous waste source, or 

health and safety concern. For each of those solvents on your list. proceed through the steps. 

2. Orient workers and supervisors: Let the staff know the importance of this substitution effort. The 

shop personnel will be able to help you. 

3. Identify and describe all processes using target solvent. 

4. Examine all upstream conditions: Identify the source of the contaminants that the solvent is called 

upon to remove. Perhaps a modification to the upstream process will eliminate the need for cleaning. 

or solvent cleaning. 

5. Examine all the downstream reauirements: How clean does that component part need to be once it 

has been cleaned. Does that part need to be cleaned at all? 

6. Identify substitution candidates: Request of current vendors as to the availability of environmentally 

responsible substitutes for the target solvents. Requests should be application specific! Review MSD 

Sheets, if the MSDS does not show contents of the candidate material, contact manufacturer for that 

information. If you receive a “this stuff is safe, and we’re not telling what‘s in it” response, do not use 

this product. As soon as a chemical crosses your threshold, you are responsible for handling, worker 

protection, and proper disposal. This applies to “free” samples as well. 

7. Evaluate the candidate materials: Determine if there are going to be requirements for extraordinary 

worker protection. Will there be extensive training requirements? Will the vendor assume the task of 

training, and will that training be billed to you? Create a testing protocol that will give an accurate 

example of the candidate material performance. Does your OEM specify the candidate materials? 
Does the vendor supply a list of customers with a track record of success using this candidate material 

for the same application? Do any of these references have a history of usage in the cleaning of similar 

substrates. and of similar contaminants? Can the vendor supply an estimate of cost per application or 

time weighted usage? 

S. Conduct off-line tests: While this may seem an obvious course of action; it cannot be stressed 

enough. Often when there is a real push to have an alternative in place, having an ineffective 

alternative. or worse an alternative that is not compatible with the substrate, is simply not an acceptable 

risk. Always select test coupons that represent all of the substrate materials that the cleaner will 

contact, Select contaminant samples that represent a realistic working scenario, i.e. neither too easy to 

remove. nor unrealistically difficult. 

9. Train emplovees: This phase of alternative material substitution is probably the most difficult. The 

difficulty comes from the basic resistance we all feel toward any new process. It is imperative that a 

clearly defined method for application of the substitute material be developed using data gathered from 

the previous steps in the evaluation and testing process. If it is possible to use the expertise of the 

vendor in the training process, so much the better. If this is not possible, I would recommend asking 

the vendor of the candidate material to supply references. If there are other companies that are using 

this product, how did they develop a usage method for that product? How long did this “breaking in” 

program take, and how much impact did the transition have to the manufacturing or maintenance 

process‘? During the training period, make sure there is opportunity to integrate suggestions from the 

line personnel who will be using the product, often this is the best way to develop the most efficient 

methods for use of a new material. 

IO. ImDlement: Utilizing the methods learned in Steps 8 & 9, bring the new cleaner on-line. I would 

suggest using the new material in a limited and controlled area at first. It may be possible to rotate into 

this area of usage, other workers for an opportunity to use the new material first hand. This is also the 

time for the quality assurance engineers to be involved in the first stages of implementation. 

1 1, Evaluate: Establish a time frame for the primary implementation. At the end of this time frame, call 

in representatives of each step of the usage process. 

If all of the user groups report satisfactory results from the preliminary implementation, set a new time 

frame for plant-wide usage. The revised time frame should be long enough to project cost savings as well as effects 

on overall production. 

There is a twelfth step to this process. With all apologies to self-help groups, this is a “Twelve-Step 

Program”. The last step is to review the final results after the plant wide usage trial. If the material seems 

unsatisfactory. or overly costly, the option still exists to go back to Step 7 and begin again. 

The Twelve-Step Program is not a guarantee that all will be smooth and seamless in transition. There will 

be impediments on the way to successful material substitution. Impediments to making a successful transition 

typically fall into two categories: The first should have been eliminated by the testing step included in the program, 

and occurs when the candidate material fails to perform chemically, the contaminant is not removed, or the test 

coupon dissolves. explodes, or otherwise is damaged by the candidate cleaner. The second category of impediment 

is that the personnel are not willing to make the changes in method necessary to accommodate the new material. 

The key to overcoming this unwillingness to look at process changes is communication. It is a normal 

human reaction to resist a new behavior when it is ordered upon the individual without their input. That is why the 

process development phase depends on the communication between the environmental staff, engineering staff and 

representatives of the floor personnel. This reaction to new processes or products is at the root of the failure of 

otherwise acceptable environmentally responsible alternatives. 

How often has the Environmental Director heard the phrase, “We‘ve tried that before. It didn’t worh‘. It i$ 

important to ask the question. “Was the problem that the chemical did not work, or was the problem that the 

personnel would not work with the chemical?’ This stresses the need for an organized method for testing and 
implementing new materials. This problem also refers back to the need for involvement of the line worker. While 

the Environmental Director may have an intimate knowledge of the regulations that are driving the process of 

change on the shop floor, the shop floor personnel are the people who will be using the new material daily, and it is 

they who will determine the success of the project. The shop workers have intimate knowledge of the overall 

processes that help make the company run. so it is imperative that we draw on the knowledge base represented by 

these line workers in a cooperative effort. 

Communication is the key to overcoming the impediments. Malung the substitution effort common 

knowledge should be a win-win situation for the Environmental Engineer. By drawing on all available expertise. the 

project can progress without fear of unknown effects of new materials or equipment. If the above Twelve-Step 

Program is followed, and all affected divisions within the company share the test results, the resistance to 

“surprises” will be eliminated. Uncomfortable as the subject may be, this information sharing process does leave the 

door open to worker-management conflict issues, even when the safety of the worker is the primary motivation of 

the proposed changes. In any organization of some size, there will be some resistant personnel. 

However small that percentage may be, this presents a significant impediment to programs which could 

benefit the company as a whole. Communication is again the key to overcoming this problem. There must be the 

backing of the upper management even before the Twelve-Ster, process begins. In order to assure those engineers 

working on the program that the new processes decided upon will be implemented without exception and in order to 

make that process become part of the standard operating procedure, management must have the courage to say. “we 

welcome input from the line personnel, but this will be an ongoing program of change“. Without management 

courage, and the hacking of the company. there will never be a successful transition into the future. That future 

requires a low or no hazardous waste generating industry. 

What has not been discussed in depth, as yet, is cost. Traditionally, cleaning chemicals have been regarded 

as a commodity, whatever was least expensive per gallon or pound, and still met the specification, was what was 

ordered. When hazardous waste handling, hauling. and storage became an issue, many companies simply budgeted 

for the disposal costs without concern for minimization or elimination of these products. In a large organization, it 

is often one individual. or department that oversees the budget for cleaner procurement. A totally separate 

individual or department oversees the budget for disposal of hazardous waste, often generated by the first group’s 

procured material. While the hazardous material price remains stable incoming, the cost for hazardous waste 

disposal continues to go up. If there is no communication between these entities, there is very little incentive for 

reducing or eliminating the hazardous waste at the source? Additionally, there are concerns when using a hazardous 

material for cleaning that are never reflected in the per-gallon price. Insurance companies are increasingly interested 

in the volume of hazardous materials used on a site. The cost of worker illness or chemical related injury is never 

calculated into the price of an “inexpensive” hazardous cleaner. The potential for contamination of the property, 

soil, or ground water exists wherever a hazardous chemical is used. The costs for such a clean-up will far exceed 

any savings from years of traditional cheap solvent use. With respect to the overall usage, recall my statement about 

evaporation rates. Most hazardous solvents typically evaporate rapidly, which makes them effective at cleaning and 

leaving a prepared surface in a short amount of time. In point of fact, a major portion of this fast evaporating 

solvent is consumed in evaporative loss. In the case of MEK, more than 60%. With acetone the figure is closer to 

80%! The actual cleaning is done with only 20 to 40% of the material. The other percentage of the cost of the 

cleaner is wasted into the air and into the bodies of the personnel using this cleaner when they breathe. 

In the event of a spill or other incident which attracts media attention, a company can expect to lose 

customers if the company is a commercial enterprise. Do you remember the incident with the big French water 

bottler? Five years later they still had not regained market share. Conversely. many companies are advertising the 

new “green” aspects of their business. People will go out of their way to do business with a company who cares 

about the environment and their workers. This can more than compensate for any new expenses in the 

implementation of environmentally responsible materials. 
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2 
Liquid Filtration for Component Reliability and Waste 

Minimization 

BY 

Edward Kanegsberg and Barbara Kanegsberg 

BFK Solutions 

16924 Livorno Dr., Pacific Palisades, CA 90272 

(31 0)-459-3614,1 Ed @ BfksolutionslorlBarbara@ Bfksolutions 1 

Introduction 

Liquid filtration is an important tool for the component manufacturer for increasing the 

performance of the component, to reduce manufacturing costs and to minimize waste streams. The type of 

filter to be used depends on its function and degree of effectiveness required. Using a filter not matched to 

the requirement can, at the least, increase costs and, at the worst, result in component failure. 

The principles of liquid filtration are applicable to both aqueous and non-aqueous solvent cleaning 

but much of the terminology is grounded in aqueous cleaning. 

Performance is the most important driver 

Performance is probably the most important driver in a manufacturing process. If the part doesn't 

function. yield drops, and the costs can become non-competitive. A part will not function properly if it is 

not clean. A part can not be free of contamination if the cleaning solution isn't pure and clean. Filtration 

may be needed to increase the cleanliness of the cleaning agent at the beginning of its use cycle or to 

restore previously used agent by removing soil build up. It is necessary to adequately remove soils. without 

redeposition. and with no substantial residue (spotting) by soils or cleaning agents. 

Pollution Prevention and Cost Reduction 

Minimizing the waste stream goes far beyond "Doing what it takes to comply with environmental 

regulations". Cost is always a driver and very frequently, if waste streams can be reduced. so can costs. 

Waste streams are not only what is left to be disposed of at the end of the whole process; it can be thought 

of as what is, in its present state, unusable at the end of any part of the process. If, by filtration or other 

means, the cleaning or rinsing agent can be restored to a usable state, the life of the cleaning solution can be 

prolonged and the cost of the cleaning chemicals will be reduced. In this age of low Ozone Depleting 

Chemicals (ODCs) and low Volatile Organic Compounds (VOCs). sometimes the alternatives are costly. 

Even at the end of the process, disposal of waste streams can be an extremely large portion of the overall 

cleaning process cost (Kanegsberg and LeBlanc). In some cases, by concentrating waste into easily 

disposed filters, a company may be able to reduce its classification as a waste generator. 

When to filter? 

Filtration requirements are different at each stage of the cleaning cycle. In many cleaning 

processes, the flow of cleaning agents is reversed from that of the parts to be cleaned so it is important to 

realize that beginning, middle, and end of cleaning agent use does not refer to the cleaning flow. The purest 

(input) chemicals are used for the final rinse, and most of the soils that need to be processed as waste 

(output) will enter the cleaning agents in early wash stages. 

Even with high-purity water and other solvents, filtration may be desirable to remove 

contaminates at the point of use. Water for precision cleaning processes must frequently be cleaner than 

clean enough to drink. It may contain contaminants such as particles, dissolved salts, organic material. 

chlorine, or fluorine which, even in small concentrations. can interfere with its ability to clean or will leave 

residues on the part. 
Not only before use or before disposal, but also in the middle of the cycle, especially for precision cleaning 

applications, soil build up and redeposition must be avoided. Filtration can be a critical part of the "keep it 

clean at all times" philosophy. Further, when water or other solvent used at the beginning of the cleaning 

agent cycle is the recycled output from another stage, contaminants must be removed without substantially 

altering the cleaning agent itself. 

The Perfect Filtration System 

Those of us involved in manufacturing precision components have exacting, idealized 

expectations for filtration systems. For example, in an ideal aqueous filtration system, the in-process filter 

would separate particulate, inorganic, and organic contamination from the cleaning agent, leaving the 

cleaning agent pristine and totally unaltered from its original state. The filter would be readily regenerated 

SO that it could last for months. perhaps years. The filtrating system for regenerating rinse water would 

remove particles, separate process oil for recycling. separate and concentrate the cleaning agent surfactant 

package in its original concentration, and provide a source of regenerated 18 megaohm water. 

In the real world, there is no universal filter; and there is no perfect filtration system, just as there 

is no universal cleaning agent or cleaning system. However, we can optimize the filtration system by 

understanding the types of filters, their benefits, and their limitations. 

Choosing the filter 

There are four basic types: bulk, membrane, adsorption, and replacement. Filters are frequently 

used in combination with each different filter dealing with a separate part of the process. 

Bulk granular media filters are called for to remove large particles or heavy contaminant loads. 

Even in critical cleaning applications, some early parts of the process may have large particles and heavy 

loading of contaminants. 

If the particulate size is small and the soil loading is low. membrane microfilters or ultrafilters 

might be needed. Sometimes the material is not particulate. For dissolved materials, a de-ionization or 

reverse osmosis process will be called for. 

For organic molecule removal, adsorptive filtration can frequently be used. 

In any event filter selection should be accomplished from a cooperative effort involving 

equipment and cleaning agent vendors and of course the user. 

Mechanical Filters 

Both bulk and membrane filters are Mechanical filters. They depend on a physical barrier for 

contamination removal. In manufacturing applications, small objects, such as the cleaning agent 

molecules. can pass through the filter but larger objects, the particulate contaminants, can not. Mechanical 

filtration is one of the most common methods used to remove particles from cleaning agents. 

For larger particles, 20 pm in diameter or larger, granular media filters, composed of sand and 

other minerals, can be used. For somewhat smaller particles, Cartridge Filters, made from synthetic and 

natural fibers. and Bag Filters, with felt-like materials, can be employed. Cartridge filters are most often 

used for lower flow rates and higher efficiency applications and bag filters for high flow rate and lower 

efficiency applications (Russo). All of these are flow-through or bulk filters, as the entire fluid stream is 

passed through the filtering media and the particles are trapped inside the bulk of the media. With flowthrough filters. the particles are harder to dislodge because they penetrate more to the center of the filter. It 

is usually more cost effective to dispose of the filter and replace with a new one than to attempt to 

regenerate it. 
Membrane Filters are designed to remove very small particles and organic molecules from a 

liquid stream. The particle entrapment is a surface phenomenon; therefore the capacity is lower than that 

for bulk filters. On the other hand. because particles are retained on the surface, they can generally be 

purged by flushing and recycled. Microfilters remove all particles down to 0.05 to 1 .O pm. Ultrafilters 

remove particles and large molecules down to .005 pni. No industry wide terminology distinguishes 

microfilters from ultrafilters; the terms can overlap (Russo). Contaminants are in general not spherical. If 

the filter pore size lies between the minimum and maximum dimensions of the particle, there can be 

incomplete filtering. It is therefore imperative to monitor the process and confirm, via particle counters, 

resistance measurement. or other methods. that the desired level of punty is being achieved. 

When used for recycling, microfilters and ultrafilters have limitations in that they can alter 

cleaning agent composition. Dirt and oil must be retained while allowing the cleaning agent to pass through 

the membrane (Bahr and Gaydos). With water/surfactant solution, some filters may only minimally affect 

the cleaning agents (Quitmeyer). However, with microfilters of pore size less than 0.2 pm, the filter may 

remove not only the contaminant but also much of the surfactant itself. This is due to properties of the 

chemistry, which cause surfactant molecules to clump into micelles (Peterson ). This limits the lifetime of 

the cleaning agent and the lifetime of the filter. 

Self-emulsifying oils are difficult to treat to prevent redeposition (Brockhurst et al.). These 

lubricants contain surfactants, which form stable emulsions. In general, aqueous cleaners can not break 

these emulsions without being consumed in the process. Microfilters (0.1 - 0.5 pm) can be used to remove 

some or most of the emulsion but generally results in some loss of cleaner constituents. Monitoring and 

adjusting of the tank becomes cumbersome and may not be an economically viable option. Some recent 

work (Ventura and Dahanayake) may lead to development of surfactants that are more amenable to 

microfiltration. 

Other important parameters are the pH and temperature of the solution. Cleaning efficiency is 

better at elevated temperatures and aqueous cleaners are usually high pH (alkaline). Both the component to 

be cleaned and the cleaning equipment, including filters, must withstand these conditions. Of two types of 

membrane filters, inorganickeramic membranes have greater tolerance to both heat and alkalinity than do 

organic polymer membranes (Rajagopalan et al.) although, as will be discussed later, there are newer 

polymer filters in development with improved heat and alkalinity tolerance. 

Filter life can be extended with appropriate flushing techniques. Because membrane filters trap 

the particles on the source side, it is possible to flush the filter by reversing the flow direction (backwash). 

Many membrane filters feature a crossflow, in which most of the fluid travels tangentially to the surface to 

sweep the contaminants away and avoid fouling the filter. Only a small portion (approximately 10%) of the 

fluid passes through the filter as the cleaned permeate. 

When a variety of particle sizes are present, it is wise to consider a tandem arrangement of filters 

starting with granular, bag or cartridge filters to remove the larger particles, then microfilters, and finally 

ultrafilters. Just as several rinses are more effective than one. several filters may be more cost effective than 

one. 

The contaminant does not need to be a particulate to be removed by a filter process. Water is 

different from most other solvents due to its polarity. The high polarity allows a large number of 

substances, particularly ionic salts. to dissolve. Removal of these ionic substances can be challenging. 

Reverse Osmosis (RO) is a mechanical filtration membrane process used to separate a solvent usually 

water, from a solution of dissolved solids. When solvent and solution are on opposite sides of a semipermeable membrane, so called because it allows some molecules to pass through more easily than others, the 

chemical energy of the solution favors the solvent flowing (osmosis) through the membrane to dilute the 

solution. A differential pressure will build up; the height of the fluid column on the solution side can be 

greater than on the solvent side. If pressure is applied to the solution, this typical direction of flow can be 

reversed (reverse osmosis) and purer solvent can be extracted from the solution. 
Since the membrane also is a mechanical filter, it also retains larger molecules, such as organic dyes, 

cleaners, oils, and metal complexes. Therefore, RO membrane systems frequently feature crossflow filtration 

to allow the concentrate stream to sweep away retained molecules and prevent the membrane surface from 

clogging. 

While the membrane removes essentially all non-dissolved particles including microorganisms to 

the limit of the filter pore size, the rejection of dissolved substances is a percentage of the concentration in 

the incoming stream. The weight. shape and amount of ionic charge determine the degree of rejection. 

Higher purity can he attained if more than one RO unit is used in series. Cartridge filters are frequently 

used to remove particulates from the feed solution that would otherwise ciog the units. 

In the past, RO applications were primarily limited to final treatment of combined wastewater 

streams. More recent cleaning applications involve RO units in specific pmess operations (such as cleaning 

agent or rinse water maintenance). allowing return of the concentrate to the process bath and reuse of 

permeate as fresh rinse water. 

Adsorptive Filters 

process in which attractive force fields at the solid surfaces pull contaminants from the liquid phase and 

bind them to the surface. The difference in strength of interaction between a solid surface and different 

contaminant molecules is the basis of adsorption separation. In general, the amount of adsorbate that can be 

attracted by an adsorbent is a function of available surface area and the strength of the force fields at the 

surface. Therefore. increasing the surface area in combination with increasing the attraction force fields 

increases the adsorption capacity. One way to increase the force fields is hy generating small micropores in 

the adsorbent materials (Lordgooei et al.), (see discussion of Activated Carbon Fiber below ). The overlap 

of the force fields from the opposite pore walls strongly enhances the adsorption in the micropores. 

Adsorptive filters use large surface areas to remove contamination. Adsorption is a physical 

Activated Carbon is the most commonly used absorbent and is generally a granular media made 

by heating carbon-containing materials in the absence of air, producing a porous material with a large 

surface area. This large surface area allows the attachment of large organic molecules. Typically, it is used 

as a pretreatment method to remove chlorine and long-chain organic molecules. It is also used to remove 

low levels of oils and greases. 

A relatively new carbon filter, with the micropore structure mentioned above, is Activated carbon 

fiber (ACF) which is made from viscose rayon or polyacrylonitrile fiber through the process of 

carbonization and activation (Zhu). It is chemically stable in high acid or alkali condition, light weight, and 

has good adsorption at low soil concentration. The narrow diameter of the fibrous fonn (normally around 

2Opm) allows much more rapid rates of ad-sorption, desorption and reaction than is possible over larger 

(trim size) granular forms (Jagtoyen et al.). The incorporation of activated carbon fibers (ACF) into 

permeable monoliths provides a connectivity between individual fibers allowing, for the first time, their 

pore structure and other characteristics to be combined with a pathway for electrical and thermal 

conduction (Kimber et al.). One of the most interesting, and to date unexplored. aspects of these systems 

lies in the ability to control the electrical potential of the adsorbent surface. This introduces a parameter by 

which to investigate the hndamental mechanisms of adsorption and catalysis, and raises the prospect of 

being able to develop mcthods to monitor and/or control the physical and chemical changes that take place. 

In particular, the adjustment of surface potential can provide a technique for promoting or inhibiting the 

adsorption of certain compounds or reactants. In adsorption, it offers a means to enhance the removal of 

selected species in order to purify a bulk fluid stream, to recover chemicals, or even to effect the separation 

or fractionation of gas or liquid phase constituents (Univ. of Ky. CAER). 
Replacement Filters 

A replacement filter replaces an undesirable material with a more desirable one. Deionization 

(DI) is the most common replacement filter process and removes dissolved ionized materials from water. 

Technically. DI water is any water from which dissolved ionic salts are removed. There is no specific water 

purity that defines the term "deionized" but it usually refers to a resistivity of greater than 1 megohm-cm 

(pure water has a resistivity of 18 megohm-cm)'. Deionization removes ions, positively charged cations and 

negatively charged anions, by replacement using ion-exchange resins. The net result is that a salt is 

replaced by pure water. A two-bed deionizer consists of a tank with cation resin followed by a second tank 

with anion resin. A mixed-bed deionizer has both cation and anion resins intimately mixed in one tank. 

DI water will remain only as pure as the equipment containing it. It may readily pick up ions from 

the process equipment, especially when heated. Also, as an example of "be careful what you wish for". 

ultra pure water may undesirably alter product surfaces by removal of ions. 

The used resin may be used once and discarded, sent back to a vendor to be regenerated or 

regenerated on-site inside the actual tanks. However. regeneration involves strong acids and caustic 

chemicals and if performed on-site, the user may have to treat the waste produced by the regeneration 

process for pH imbalance and/or heavy metals before disposal. Resin cannot be regenerated ad infiniturn. 

The capacity decrease rate is usually greater for waste applications than for source pre-treatment due to 

higher contamination levels. 

Deionization and reverse osmosis often are found sequentially in the same system. DI is necessary 

as a post-treatment process to RO whenever the user requires a higher water purity than one megohm-cm 

resistivity. Sometimes the only way to make DI economical is to use an RO membrane as pretreatment for 

the deionizer to reduce the ionic percentage and therefore prolong the ion exchange resin in the 

deionization unit. 

The challenge of specialized filtration development 

To those of us involved in critical cleaning, development of advanced filters may be paramount. 

Unfortunately. the materials used in filters are often developed by large petroleum companies. with what 

might be described as an oil-company mentality. That is, they develop a plastic with the idea of selling 

immense quantities, but they may be unaware or unconcerned about high-value. niche markets. 

Serving the niche applications of the future is likely to involve an ability to respond to the subtle 

requirements of each micro-niche market by surveying and perhaps modifying the physical and chemical 

characteristics of the overall product line. Mike Beeks technical director, research and development, at The 

Brulin Corporation, Indianapolis, IN explains that the filter must remove soils and particles, sometimes to 

fractions of a micron. while having minimal impact on the cleaning chemistry. It must be able to withstand 

a wide range of organic and inorganic materials. In the general scheme of the plastics industry, filters are a 

tiny application; but a properly engineered filter could provide an invaluable pivotal solution for the 

components industry (Beeks) 

Let us examine, for example. one class of polymers, polysulfones, which have unrealized potential 

in membrane filter manufacture. Polysulfones are strong, clear, and they have temperature stability and 

chemical resistance which is superior to other plastics. Polysulfone, pol yether sulfone and polyphenyl 

sulfone currently find uses in areas ranging from biomedical/diagnostic products to filters. However, the 

role of polysulfones in improving filtration performance could be greatly increased. 

Roger Jones, president of Franklin Polymers sees the desirability of a paradigm shift. "Polysulfones 

represent a significant, profitable business. Unfortunately, the niche doesn't fit the current business template 

of consolidation and size. Many companies are trying to get bigger, faster - they are trying to be first or 
second. It’s a flawed template. You don‘t have to be first or second to be a success. Let’s take for example 

the use of polyethersulfones for filters. Filters are a polyethersulfone market rather than a polysulfone 

market, because polyethersulfone has better heat and chemical resistance. You have the producer. the 

compounder. then the distributor. From the producers’ viewpoint. filters are a miniscule market, so people 

in those areas may get little support from the polymer producer. If the managers considered the impact of 

smaller niche markets, they could provide more product support. charge more, and make more money. 

This is counter to a bulk chemical mentality.” (Jones) 

There is progress in development of more specific products for filtration. One example is ACF, 

described previously. Developmental work is also proceeding which may lead to improvements in plasticsbased fitters. Dr. Ryan Giedd at Southwest Missouri State University sees applications for secondary 

modification of polysulfones to produce narrow-niche products of high value. He describes his work in ion 

implantation as a tool in expanding applications for polysulfones. “When you ion implant, hydrogen is 

removed from the polymer structure, making it a hard carbon-based material. The implanted segment may 

be only 700 Angstroms. The softer, less resistant material can then be removed. resulting in three 

dimensional nucro-machined structures. The structure is electrically-conducting, providing potentially 

utility for high-value resistors.” 

Dr. Giedd notes that this is a secondary process on the finished polymer. He sees applications for 

such modified polymers where there are requirements for a material that is thin. hard, strong, and with a 

high surface area. such as in high value small geometry resisters and microstrain gauges, and bolometers 

(specialized heat measuring sensors used to detect infrared radiation) (Giedd). 

Conclusion 

Filtration, like the rest of the critical cleaning industry, is an evolving science. Cleanliness 

demands keep increasing, especially in electronics and biomedical applications, and cost and environmental 

pressures favor recycling of cleaning chemicals and extending the useful lifetime of filters. Developments 

me continually being made to advance the utility of filters of all types, and such developments are likely to 

continue due to perfomiance and environmental drivers. There is no one-size-fits-all solution and users, 

cleaning agent and cleaning equipment suppliers must continue to work closely with each other to achieve 

affordable, effective processes. 

References 

I. M. Bahr and S. Gaydos, “Effects of Microfiltration on Aqueous Degreasing Solutions”, CleanTech ‘98 

Proceedings, pp. 32 1-330. 

2. M. Beeks, Technical Director, The Brulin Corporation, personal communication. 

3. R. Brockhurst, M. Beeks. and D. Keller, ” Aqueous Cleaning Essentials”, in “Handbook For Critical 

Cleaning”, Barbara Kanegsberg, ed. , CRC Press (in press),. 

4. R. Giedd, Department Head. Material Science, Southwest Missouri State University, personal 

communication. 

5. Jagtoyen et al, 1994, Materials Res. SOC. Symp. Proceedings,344, 77-81; as referenced by the Univ. of 

Kentucky Center for Applied Energy research (CAER), at littp:~:’~~\\.n:.inrsi!c.iiI\~.ed~~il-r~~ai:~~r.i.se_.~rc!!,!ltm 

6. R. Jones. President, Franklin Polymers, personal communication. 

7. B. Kanegsberg and C. LeBlanc, “The Cost of Process Conversion”, CIeanTech ‘99 Proceedings, pp. 12- 

29. 1999. 
8. Kimber et al, 1996. Gas. Sep. Purif., 10 (2), 13 1 136: as referenced by the Univ. of Kentucky Center tor 

Applied Energy research (CAER), at h~tp:~/~~~~\\~.ri~~~~~.~i~~.~~lii~i~~~~~t~~

9. M. Lordgooei, K. R. Carmichael, M. J. Rood and S. Larson, “Development of an Activated Carbon Fiber 

Cloth AdsorptioniRegeneration System to Recover and Reuse Toxic Volatilc Organic Compounds”, Illinois 

Waste Management Research Center (WMRC), report RR-08 I available tiom WMRC through 

1ihrai.i. @nmrc.iiiuc..edii 

10. J. Quitmeyer, “Aqueous Cleaning Filtration Study”, CleanTech ‘98 Proceedings. pp 20-15. 

I I. D. Peterson, “Limits of Microfiltration”, Plating and Surface Finishing, May 1995, p83-86. 

12. N. Rajagopalan, T. Lindsey, and J. Sparks, “Recycling Aqueous Cleaning Solutions”, Products 

Finishing. Vol63, No. 10, July 1999. 

13. J. Russo. “Selecting the Best Waste Water Treatment for Aqueous Operations”, in “Handbook For 

Critical Cleaning”, Barbara Kanegsberg, ed. . CRC Press (in press). 

15. M. Ventura and M. Dahanayake, “Filterable Surfactant Class Resolves Separation Anxiety”, Precision 

Cleaning Magazine, July 1998. 

16. H. Zhu, Shanghai No. I Carbon Fiber Co., Ltd., personal communication 

About the authors 

Ed Kanegsberg, Ph.D., is a physicist with BFK Solutions and a member of the technical staff at Litton 

Guidance and Control (Woodland Hills. CA). He has over 30 years of experience in precision instrument 

development and productionization. He addresses production yield issues through both process 

improvement and component modification. 

Barbara Kanegsberg, President of BFK Solutions, works with components and parts manufacturers to 

resolve cleaning. contamination control, and environmental issues. Barbara is a recipient of the U.S. EPA 

Stratospheric Ozone Protection Award for her achievements in implementing effective. environmentallypreferred processes. She is also a member of the Editorial Advisory Board of Precision Cleaning 

Magazine. 
Chemical Aging of Environmentally Friendly Cleaners' 

L.L. Biegert, K.B. Evans, B.D. Olsen, B.L. Weber 

Cordant Technology: Thiokol Propulsion 

P.O. Box 707 

Brigham City, Utah 84302-0707 

(435) -- 863 3958 I Biegellig Thiokol.com 1 

ABSTRACT 

Use of cleaners in the manufacturing area demands bottles that will hold a sufficient amount of. 

material and allow for easy and controlled dispensing by the operator without contamination or material 

leaching from the bottle. The manufacturing storage conditions are also a factor that may affect cleaner 

chemical integrity and its potential to leave a residue on the part. 

A variety of squeeze bottles stored in mild (72 OF, 10% R.H., dark) and harsh (105 "F, 50Y~ 

R.H., fluorescent lighting) conditions were evaluated to determine the effect of environment and bottle 

exposure on ODC cleaners chemical composition. Low Density Polyethylene (LDPE) bottles were found 

to be quite permeable to all the cleaners evaluated in this study indicating this bottle type should not be 

used in the manufacturing area. Fluorinated Polyethylene (FLPE) bottles showed little cleaner loss and 

change in cleaner chemical composition over time suggesting these bottles would be acceptable for use. 

Chemical analysis indicates limonene containing cleaners show increased non-volatile residue 

(NVR) content with storage under harsh conditions. Some cleaners use BHT (butylated hydroxytoluene) as 

stabilizer and to protect against limonene oxidation. Under harsh conditions. BHT was quickly depleted 

resulting in higher NVR levels. 

INTRODUCTION 

The vendors of environmentally friendly cleaners have established shelf life times for each of the 

cleaners based on containment within the manufacturer's sealed container. In the manufacturing area. these 

cleaners will be removed from the vendor container and placed in dispensers that will make hand wipe 

operations convenient. To ensure the exposure to the dispensing unit (squeeze bottles) and the 

manufacturing environmental conditions (temperature, humidity, light, and time) do not impose any 

adverse chemical aging on the cleaners, an aging study was initiated. 

Many of the cleaners currently being evaluated for hand wipe operations in the manufacturing area 

contain the terpene hydrocarbon, limonene. It is well known that limonene readily oxidizes upon 

environmental exposure forming less volatile compounds. Conditions in this study were selected to not 

only mimic manufacturing conditions but also be of a sufficient harsh environment to produce oxidized 

limonene compounds. 

5~ 2000 Thiokol Propulsion, a Division of Cordant Technologies 

' This work was performed under contract NAS8-3K100 as part of NASA's ODC Cleaner TCA 

Replacement Program. 

i 
PLAN 

CLEAN cs RS.BOT NDI 1 N 

Six cleaners were selected from the candidates that are currently considered as acceptable 

alternative cleaners to TCA for hand wipe cleaning RSRM production components. These cleaners art: 

listed in Table I along with a chemical description. Most ofthe cleaners contain the hydrocarbon limonene 

that has two sites of unsaturation. BHT (butylated hydroxytoluene) is found in three of the cleaners 

containing limonene and is used as a stabilizer. DPGME (dipropylene glycol methylether) is reported in 

two of the cleaners. lTB2P (I-t-butoxy-2-propanol) is also found in two cleaners and like DPGME would 

expect to be hydrophilic. Eventhough hydrocarbons are found in both PFD and BA4 cleaners the types of 

hydrocarbons are different for these two cleaners. 

Tablel: Cleaners and Their Composition 

Four bottles were evaluated in this study. LDPE (low density polyethylene) and FLPE 

(Fluorinated High Density Polyethylene) bottles were evaluated. The FLPE bottles are currently used to 

contain TCA in the manufacturing area. Silgan bottles (manufactured by Silgan Plastic Corporation) were 

also evaluated. These bottles are composed of a HDPE (high density polyethylene) outer layer and a Nylon 

inner layer. Glass bottles were used as a baseline. Glass Qorpak bottles (Fisher Catalogy #03-320- 1 1 J) 

were fitted with Teflon closures and spouts so the cleaner would be exposed to the atmosphere to simulate 

exposure that cleaners in the squeeze bottles would see. 

The storage conditions were selected to not only represent typical and worse case conditions found 

in the manufacturing areas but also in the worse case condition be of a sufficiently harsh environment to 

induce high levels of non-volatile residue (NVR). The mild (typical normal manufacturing area) 

environment was selected as 72 k 5"F, less than 10 YO R.H. and samples stored in the dark. For harsh 

conditions the bottles were stored at 105 f 5"F, 50 YO R.H. and under constant exposure to fluorescent 

lighting. 

WEMICA L ANALYSIS 

Several methods of chemical analysis were conducted to monitor the effect that aging has on the 

chemical properties of the cleaners. The methods used in this study include non-volatile residue, and 

moisture. 

The NVR testing conducted on cleaners containing limonene is not an absolute evaluation of the 

non-volatile residues that will be seen on a production part. Instead the NVR results should only be used 

to evaluate the purity of the material. Non-volatile residue is an empirical measurement detined by the 

evaporation conditions. NVR, as determined by this method, is defined as any material that does not 

evaporate after four hours in a forced draft oven at 105°C. 
The water present in the cleaners was determined by a Karl Fischer titration method using 

pyridine-free reagents. The method measures water content by quantitatively titrating the water with a 

base-iodine-sulfur dioxide complex. Water consumption is determined by amperometric endpoint detection 

using a dual platinum wire electrode. 

DISCUSSION 

To ensure the NVR testing method would produce results that would be consistent throughout the 

study. a correlation between NVR and test conditions was made. A newly manufactured lot of PCG was 

compared with cleaner that had been stored in the manufacturing area for 6 months. Seven to ten 

milliliters were placed in a 75-ml aluminum dish and allowed to evaporate under temperatures ranging 

from ambient (20°C) to 130°C. 

Figure 1 shows the effect of test temperature on NVR level. For the aged PCG. the ambient dried 

samples had a higher NVR percentage most likely due to low molecular weight oxidized limonene 

products. These low molecular weight compounds are present when the evaporation temperature is near 

ambient while at higher temperatures they evaporate. The NVR content for the aged PCG appears to 

stabilize between 100 and I 10°C. 

The time that the samples were dried was also investigated during the development of the NVR 

test method. Figure 2 shows the NVR levels of the newly manufactured PCG and 6 months aged PCG 

ranging from a dry time of IO minutes to 6 hours at 105°C. The fresh PCG NVR levels become stable 

after 2 hours while the aged PCG continues to lose weight. The weight loss over time is most likely due 

to a continued loss of semi-volatile oxidized compounds. From this preliminary testing, the NVR test 

method was selected as evaporation of a 10 milliliter sample of cleaner at 105°C for four hours in a forced 

draft oven. 

The NVR content of the cleaners stored under harsh conditions in glass bottles over time readily 

correlated with limonene content and BHT depletion. Both cleaners that contain limonene and no 

stabilizer (PCG and PRP) show initial higher levels of NVR compared to the other cleaners. Those 

cleaners that contain limonene and stabilizer show increased NVR levels as soon as the stabilizer is 

depleted. Stabilizer depletion for PFD was 3 weeks, for PRP four weeks and for PL4 the stabilizer was 

depleted by 9 weeks. The time to stabilizer depletion was dependent on both the stabilizer amount and 

limonene percentage in the cleaner. 

The NVR content of the cleaners in glass bottles under mild is shown in Figure 4. As expected, 

only those cleaners with limonene and without stabilizer show any increase in NVR content. The NVR 

content for cleaners stored under mild conditions is lower than when stored under the harsh environment. 

A comparison of bottle NVR content is shown for PCG under harsh conditions in Figure 5. The 

LDPE bottles appear to be more permeable. Under the harsh conditions, water not only diffuses into the 

bottle. cleaner also diffuses out. The NVR difference between glass and FLPE bottles may be attributed to 

the glass bottle larger spout opening or also the transparency of the glass. 

The moisture content of the cleaners in glass bottles stored under harsh conditions IS shown in 

Figure 6. The cleaners with the higher moisture content (BAI. BA4 and PL4) all contain chemical 

components that are hydrophilic in nahire (DPGME and ITB2P). Over time and 50% relative humidity, 

these cleaners continue to pick up moisture. 

Figure 7 shows the cleaner moisture content stored under mild conditions (less than 10% relative 

humidity) in glass bottles. Those cleaners with hydrophilic components have higher levels of initial 

moisture and will gain more moisture over time with exposure to the atmosphere. 

Like the NVR levels, moisture in cleaners stored in LDPE bottles is higher compared to the other 

containers evaluated in this study. Figure 8 shows the moisture content of PL4 stored in the various 

bottles under harsh conditions. The glass bottles also have higher moisture content compared to the FLPE 

bottles and may be explained by the larger spout in the glass bottle allowing for an increased exposure to 

the atmospheric moisture. 
SUMMARY/CONCLUSIONS 

The NVR content as measured by evaporation of ten milliliters at 105°C for 2 hours in a 

convection air oven is a method that can be used to monitor the purity of a cleaner and is not an absolute 

evaluation of non-volatile residues that will be seen on a production part. The NVR content is dependent 

not only on the amount of limonene present in the cleaner but also on the presence of a stabilizer (BHT). 

The storage of cleaners in high humidity. high temperature and fluorescent lighting also contributes to the 

oxidation of limonene. 

Cleaners that contain moisture sensitive compounds ( 1 TB2P and DPGME) initially have higher 

levels of water. The moisture content continues to increase as samples are stored under high humidity 

conditions. If stored in a mild environment there is little change in moisture content over 4 months. 

A cleaner's susceptibility to moisture and NVR formation is also dependent on the type of storage 

bottle. The permeability of LDPE bottles to moisture prohibits their use in a manufacturing environment. 

FLPE bottles are less susceptible to moisture and thus are a good candidate. 

Test Temperahlre Effect on NVR 

'm PCG 

\+ 7-h. FCG 

Figure 1: Percent NVR as a Function of 

Evaporation Temperature. 

PCG Percenl NVR over Time a1 105deg C 

Figure 2: Percent NVR as a Function of Time 

at 105 OF. 

NVR from Glass 8Onle5 

IHanh Condilmi 

Figure 3: Percent NVR as a Function of Time 

under Harsh Conditions 

3 

Lt 

0 

NVR horn Glass Boles 

iYiid Cmdilioni 

1co No%*- 

Figure 4: Percent NVR as a Function of Time 

under Mild Conditions. 
Moistuie d PL4 I 

Figure 5: Percent NVR in PCG as a Function 

of Bottle Type Figure 8: Percent Moisture in PL4 as a 

Function of Bottle Type. 

09 

oe 

ill 

06 

Mostwe ban Glass Boules 

Figure 6: Percent Moisture under Harsh 

Conditions 

Figure 7: Percent Moisture under Mild 

Conditions 

3 
NAtional Materials Information System 

Jeff Guthrie 

AMPTIAC 

201 Mill St 

Rome, NY 13440 

Phone #: (3 15) 339-7058 

: (3 15) 339-7107 

jguth rie@ii tri.org I 

Web: http://arnptiac.iitri.ord 

Abstract 

The following paper describes the NAtional Materials lnformation System (NAMIS) developed by the 

Advanced Materials and Processes Technology Information Analysis Center (AMPTIAC). 

NAMlS preserves the DoD materials and process knowledge base making it readily available to the 

materials community. Inside NAMIS, users will find several database modules of interest space and launch 

vehicles communities. Two searchable bibliographic database containing all past High Temple Workshop 

and the Cocoa Beach Conference proceedings have individual paper citations linked viewable electronic 

documents. The third database module, NASP, contains a virtual library of all the NASP (National 

Aerospace Plane) final reports from the materials and structures augmentation program. 

Although it never came to fruition, many breakthroughs in high temperature materials and processes owe 

their success to the NASP program. Since NASP was never fielded, these breakthroughs in materials never 

fully transitioned and eventually the technical heritage and expertise dissipated. Both government and 

industry personnel moved away from high temperature materials problems and often their personal libraries 

were lost. 

Today, many proposed new systems present similar technical challenges and require this same expertise. 

For example, NASA’s X33, X34, Reusable Launch Vehicle (RLV), Hyper X, and Future X will need 

advanced Thermal Protection Systems (TPS), hot structures, and huge liquid hydrogen (LH) and liquid 

oxygen (LOX) tanks. In the military, Military Space Plane (MSP) will require these same technologies. 

Additionally, multiple new missile concepts such as the Common Aero Vehicle (CAV), the Hypersonic 

Technology program (HyTech), and High Speed Strike program (HST), demand innovative hot structure 

and TPS. 

AMPTIAC will demonstrate the features of these web-based databases found at the following URL: 

httn: SWAM JS.i itri.orq 
Introduction 

Continuing advancements in high temperature materials require a sound database of material properties and 

an understanding of past technology development. The Advanced Materials and Processing Technology 

Information Analysis Center (AMPTIAC) operated by IIT Research Institute (IITRI), function as the 

caretaker of materials information for DOD. As part of its caretaker role, AMPTIAC populates and 

maintains high temperature materials databases with evolving technology. These databases, in-turn, helps 

fulfill an AMPTIAC'S role of disseminating DoD materials data. 

A bout AMPTlAC 

AMPTIAC, is the culmination of 13 other materials information analysis centers dating back to 1955 at 

Battelle Memorial Institute and 1960 at Purdue University. The AMPTIAC library contains nearly 2 10,000 

technical reports and books addressing a broad spectrum of engineering materials. This library is 

continuously updated in an attempt to collect the latest technology advancements in material applications, 

properties and processing techniques. As part of its mission for DOD, AMPTIAC is applying this resource 

to construct an integrated material and process database - labeled the NAtional Materials Information 

System (NAMIS). 

Making this database possible requires a firsion of materials and software expertise to achieve the desired 

functionality and aesthetics. Additionally, rigorous data evaluation ensures pedigreed data through strict 

criteria mapped out by both the American Society for Testing and Materials (ASTM) and the National 

Institute of Standards and Technology (NIST). Evaluated data is critical since the exploding availability of 

technical data from handbooks, electronic databases, on-line libraries and the World Wide Web, require the 

user to examine the quality of data. The performance of manufactured products depends on the reliability 

of the materials data used to design and plan the manufacture of the product. 

Legacy Materials Data 

Future high performance hypersonic vehicles will require many advanced materials. Fortunately, there is 

an abundance of data from past programs and conferences available for use. Unfortunately, this data is 

scattered throughout a sea of documents. Furthermore, the past bow waves in funding for hypersonic 

activities have ensured that very few people have remained active in this technical arena. Consequently, 

our heritage and core competency has diminished. To make matters worse, as organizations and people 

moved, whole libraries were discarded. AMPTIAC is actively collecting this data and depositing it in 

easily manipulated databases to ensure the survival of our technical legacy. 

Today, hypersonic applications are re-asserting themselves and high temperature materials are once again a 

lead interest item. These new systems present similar technical challenges and require this same expertise. 

For example, NASA's X33. X34, Reusable Launch Vehicle (RLV), Hyper X, and Future X will need 

advanced Thermal Protection Systems (TPS), hot structures, and huge liquid hydrogen (LH) and liquid 

oxygen (LOX) tanks. In the military, Military Space Plane (MSP) will require these same technologies. 

Additionally, multiple new missile concepts such as the Common Aero Vehicle (CAV), the Hypersonic 

Technology program ( HyTech), and High Speed Strike program (HST), demand innovative hot structure 

and TPS. 

NAMIS 

Without electronic materials databases, engineers resort to looking up data by hand using databooks and 

property sheets. Finding data via this method is both inefficient and time consuming -much like finding a 

needle in a haystack. Most importantly. the lost opportunity. which results from excess data retrieval time, 

often prevents the designer from being able to fully perform their duties. Electronic materials databases 

allow efficient access to the materials properties and characteristics by organizing large quantities of data - 

often searchable through automated procedures. Databases also preserve corporate expertise making past 

work available at an engineer's fingertips and allow for swift updates to the knowledge base. 
NAMIS Architecture 

NAMIS is an ongoing effort to develop and field an information system to be used by design engineers 

involved with selecting materials for component designs. In addition, NAMIS facilitates materials 

engineers who are trying to disseminate data. The information contained in this system will include 

numerical material properties, life cycle information, and graphical information such as images of material 

microstructures, and phase diagrams. Additionally, NAMIS will house electronic documents from which 

the numerical data were extracted. The electronic documents are derived from AMPTIAC library holdings 

as well as selected reports and documents from various sources including specific conferences and 

workshops. 

NAMIS is a web-based information system, which will include many different types of materials classes. 

Web-based systems don't require the stringent hardware requirements that software resident on a personal 

computer does. For example, a disclaimer usually accompanies commercial software listing minimum 

microprocessor, RAM, and disk space needed for installation. Moreover, web-based systems work well 

across many platforms be it a Macintosh, Pentium 111. or even a 386 because all machines will use a 

standard browser to interface with the database resident on a server. Additionally, the browser (either 

Netscape or Internet Explorer) can be downloaded on the Internet for free. 

To cover the breadth of materials classes, AMPTIAC is building this database in a modular fashion with 

each module functioning either as a stand-alone database or an integral piece of the larger database. 

NAMIS functions as the umbrella that binds the individual modules together. The database will contain 

materials descriptors, test techniques, evaluation criteria, electronic supporting documents, and all the 

accompanying property data. 

Upon entering NAMIS, you will note that NAMIS is funded by components of the Army, Navy, Air Force. 

DoD, and NASA. You will also see that NAMIS is composed of three main sectors of information: 

Conference/Workshop Proceedings, Numerical Material Property Databases, and Virtual Libraries. A 

couple other items are immediately apparent. First, NAMIS provides current and topical information about 

what is going on through out the modules via pop-up menus. Second, NAMIS provides information about 

how to use the site, how to contact AMPTIAC, and provides a site search option. See Figure 1 for a 

depiction of the overarching NAMIS features. 

Figure 1 : Main Navigation Screen. 
Security 

Given the sensitive nature of the data, NAMIS must first ensure that adequate security measures are 

employed to preclude unauthorized users from gaining access to the system and tampering with the data. 

AMPTIAC is focusing on sensitive hard to get materials and process data for NAMIS. Currently, most of 

the data is either Export Controlled, ITAR restricted, or For-Official-Use-Only. AMPTIAC will ensure 

adequate security measures are employed to preclude unauthorized users from gaining access to the system 

and tampering with the data. AMPTIAC uses authentication, encryption, firewalls, and other technologies 

in a system that incorporates features specified in the emerging Public Key Infrastructure (PKI). 

PKI is a comprehensive system that provides public-key encryption and digital signature services. 

The purpose of a PKI is to manage electronic keys and to maintain a trustworthy networking 

networking environment. PKI will be the standard for all DoD sensitive information placed on the web. 

Additionally, the DoD plans to fully adopt and implement PKI by FY02. 

The elements of PKI include encryption, which provides confidentiality and access control while digital 

signatures provides for authentication, data integrity, and non-repudiation. These elements are combined to 

effectively 'sign and seal' any electronic communication, and the signing is done in a way that the user who 

signed the data cannot later successfully deny signing that data. 

Currently, NAMIS is encrypted, access controlled through user names and passwords, and resides behind 

the IlTRI firewall. NAMIS users can apply for access to the sensitive areas of NAMIS through a link on 

the main navigation screen (Figure 1) to a subscription page. Once in the subscription area. users will be 

asked to supply a DD form 2345, a letter from their company security office stating that they are an 

employee and a U.S. citizen. and a subscription form. 

When PKI is fully adopted by the DoD, all NAMIS users will have a registered identity stored in a digital 

format known as a public-key certificate. The certificate will specify the validity period (or lifetime). 

These certificates are inherently secure and can conveniently be distributed in a completely public manner. 

To reduce cost and ensure a secure environment, AMPTIAC will select a qualified third party to issue 

certificates to users and act as the certificate authority. 

Con ferencesflbrkshops 

The Conferencei'Workshop Proceedings represent a unique opportunity to capture the evolution of whole 

technical Communities and define the current state-of-the-art with-in those technical communities. 

Cocoa Beach 

The Annual Conference on Ceramic. Metal, and Carbon Composites, Materials and Structures (commonly 

referred to as the Cocoa Beach Conference) has a wealth of high temperature composites data. The Cocoa 

Beach Conference is organized by representatives from the U.S. Navy, U.S. Army, U.S. Air Force, the 

Defense Advanced Research Projects Agency (DARPA), the Department of Commerceinational Institute 

for Standards and Technology (DoC/NIST), the National Space Aeronautics and Space Administration 

(NASA). and the Department of Energy (DOE). AMPTIAC is responsible for publishing the proceedings. 

The 1998 proceedings are currently available as an information system with a virtual library. Also, this 

database is available as a standalone product on CD. In the near future, AMPTIAC will expand the web 

site to include he 19Y6, 1997, 1999. and 2000 proceedings. AMPTIAC's plans to ultimately convert all the 

past meeting's paper presentations to electronic documents. 

The Cocoa Beach module of NAMIS is really a dynamic virtual library. Since it grows every year, a 

software virtual librarian helps organize the data. Navigating within the Cocoa Beach module is 

straightforward. Each paper has a bibliographic citation linked to a PDF file of the paper or briefing. The 

fields in the bibliographic database consist of Title, Author, Abstract. and Keywords. See Figure 2 for a 

depiction of the module. 
Figure 2: Main Screen Cocoa Beach Module 

The search engine searches any or all of these fields. Moreover the user has the option of viewing and 

printing the bibliographic results either for a single citation or for all of them via the reports section. The 

following figure shows the results of a bibliographic search. 
Users can also scroll through the search results to view either the briefing presented or the paper if one was 

submitted. If the user decides to view a presentation by clicking the View Briefing link, the database 

brings-up Adobe Acrobat within the browser. The first item visible is a proviso concerning the export 

control restrictions on the document. Subsequent pages of the presentation are all marked top and bottom 

with "Document is Subject to Export Control" to ensure that when printed the document restrictions are 

clear. Within the Acrobat frame, users can search using the find feature characterized by the binocular 

icon. Optical character recognition was performed upon all the documents that reside within NAMIS to 

enable the Acrobat text string search. 

One final search strategy the Cocoa Beach module features, employs the "View Table of Contents" icon to 

link to an index of the conference by year. Once inside the index, papers are viewable by further clicking 

the "View" icon to the right of the index. 

High TemDle 

High Temple Workshops are a series of workshops covering the areas of design, development, and 

application of high temperature reinforced polymeric composites. Structural applications of interest 

typically see time-temperature relations measured from hours at 500"F-700°F to seconds at 1,400'F. A 

Tri-Senrice/NASA steering group initiated the High Temple Workshops. Workshops were held from 1982 

to the present. Over the years, hardcopy proceedings were generated for each workshop. 

The High Temple Workshop information system serves a dual purpose. First, this module helps to 

administer the conference. Second, High Temple has a dynamic virtual library component much like 

Cocoa Beach. Figure 4 illustrates the layout of High Temple. 

Figure 4: High Temple Navigation Screen 

Functionally, the site is split into several sections for administrative purposes and a section for the virtual 

library. A secure forum section for year round information dissemination and technical interchange is 

a\ailable. Note. the key next to this section denotes that this section is protected and encrypted. 
The “Inside High Temple’’ section is open to everyone and serves to help advertise the workshops. This 

section contains background information about the workshops, a pictorial history of the workshops, and 

information on how to contact the key steering group members. 

The “Upcoming Workshop” section of course describes information about the next workshop including a 

calendar, an agenda, hotel directions with a link to the hotel web site, and an online registration tool. (Note 

this section is also open.) The registration tool asks users to complete a form, which generates an email to 

the workshop administrator. The data from the form populates a database of attendee information that the 

workshop administrator could then access for later mailings. 

The “@The Workshop” section contains the virtual library; as such, it is all export controlled and restricted 

to only properly registered users. Much like Cocoa Beach, users can sift through the papers by year and by 

paper title via the “Workshop Listing” and “Papers” links. However, thanks in large part to the High 

Temple Index Committee of 1996, the virtual library searches using key words in addition to title and 

author. AMPTIAC generated detailed keywords for papers from 1996 to 2000 and converted the I996 

paper index to an electronic format for searching. Keywords represent the most powerful search 

mechanism. Using keywords allows the user to quickly search large amounts of data by cutting it into 

successively finer and finer pieces. NAMIS has eight major keyword categories, which are comprised of 

material type, property, process, application, testing technique, funding organization, and analytical tools. 

The search tool permits the user to use any conceivable combination of the keywords. The search results 

represent only those papers which have all the keywords selected for searching. The following figure 

shows that searching for the glass transition temperature of AFR700B yields 24 papers. 

Hiah Ternah 

M Uh*. 

Figure 5: Keyword Search Tool 

The papers listed are each linked to the pdf image of that paper. Once again, users can use Acrobat to 

search for text. In this case, searching for Tg will display the property. A final benefit to using key words 

involves the ability to identify missing data. If a search yields no results then it is fairly certain that no 

work has been done in the past given that the High Temple Workshops encompass nearly all the work 

performed on high temperature polymers. For example, to date, the glass transition temperature hasn’t 

been measured on resin transfer molded LARC-13. This feature not only helps the community reduce 

duplication of effort but it also helps the community work in a synergistic manner on new problems. 
I i’rtual Libraries 

Virtual libraries differ from conferences and workshops in that they are static -no new materials are added 

on a year-to-year basis. Virtual libraries also do not perform an administrative function for the conference. 

NAMIS virtual library modules are intended to capture legacy DoD generated data. 

UP 

The materials development under NASP was extensive with between 100 to 200 million spent on the 

Materials and Structures Augmentation Program and accompanying laboratory programs. This 

development was spread over a wide variety of materials classes including Titanium Aluminides, Ceramic 

Matrix Composites, and Carbon-Carbon Composites. This valuable data was never collected and focused 

in a fashion that made it available to the whole high temperature community. 

Currently, the NASP module functions like the Cocoa Beach module. Each paper has a bibliographic 

citation linked to a PDF file of the paper or briefing. The fields in the bibliographic database consist of 

Title, Author, Abstract. Keywords, and a NASP Joint Program Office report number. The same reporting 

and viewing option in the Cocoa Beach module are available to NASP. The NASP library contains 638 

bibliographic citations and 468 electronic reports. (170 reports are classified - as such they are not included 

but they have pointers to the controlling authority.) This represents well over 80,000 pages of dedicated 

materials and structures information. 

Within a month of the time of this paper, the NASP virtual library will feature a keyword tool like the one 

found in the High Temple Module. 

IHPTET 

The Integrated High Performance Turbine Engine Technology (IHPTET) program is an ongoing National 

program focused upon doubling the US military’s 1988-propulsion capability. A consortium of high level 

Government and propulsion industry managers, known as the IHPTET Steering Committee, provides 

oversight and guidance for the IHPTET Program. The Army. Navy, Air Force, NASA, DARPA, and six 

major US turbine engine manufacturers are involved in the IHPTET Program. 

Materials development is a very important piece to IHPTET success. Like NASP many materials 

breakthroughs owe their success to the IHPTET program. At the time of this paper, AMPTIAC is nearing 

completion of an IHPTET module to NAMIS. When completed, the IHPTET virtual library will function 

like the NASP module with over 70 digitized materials related IHPTET reports in its library. 

Numerical Darabases 

AMPTIAC wants to provide designers with a reliable source of data to assist in making materials selection, 

risk reduction, and life extension decisions. As such, AMPTIAC is developing numerical databases that 

will eventually feed design packages. Presently, the numerical databases contain property data and 

metadata M hich describes processing history, test type and conditions, physical form, composition and 

source data. A complete description of all metadata supplies the pedigree that should always accompany 

property data. In order to make materials selection easier, the numeric databases will utilize software tools 

that allow a variety of display methods including transparent unit conversion, display of multiple plots, 

scalable plot axis and both linear and logarithmic axes. 

Infrared Window and Domes 

AMPTIAC is developing an infrared window and dome materials numerical database complete with 

descriptions of processing history, test type and conditions, physical form, composition and source of data. 

A complete description of all the metadata is important to prevent misuse of data and to interpret the 

fidelity of the data. AMPTIAC actively participates in the ASTM E49 committee for materials databases to 

make sure NAMIS accurately captures a materials pedigree. This database will have a host of optical, 

dielectric, thermophysical, mechanical, rain erosion, and laser damage properties. See Table 1 for a 

complete list of properties contained in this module. 
Table 1 : MATERIAL PROPERTIES 

I OPTICAL MECHANICAL 

Transmission Compressive Strength 

Absorption Flexural Strength 

Reflectance Elastic Compliance 

Refractive Index Hardness 

Laser Damage Threshold Shear Strength 

Scattering Fracture Toughness 

Dielectric Constant Young's Modulus 

Poisson Ratio 

THERMOPHYSICAL RAIN EROSION 

Emissivity Velocity Damage Threshold 

Heat Of Fusion Damage Site Density 

Thermal Conductivity Degraded Transmittance 

Thermo-Optic Coefficient Failure Time 

Thermal Expansion Coefficient Scatter 

Melting Point 

Thermal Diffusivity I 

The database module contains over 1800 data sets compiled from over 300 reports extracted from six 

major window materials. These six materials are germanium, zinc sulfide, zinc selenide, having long 

wave IR applications and sapphire, spinel and yttria, finding applications in the midwave IR band. 

Moreover the database will utilize software tools that allow a variety of display methods including 

transparent unit conversion, display of multiple plots. scaleable plot axis, and both linear and logarithmic 

axis. 

The InfraRed Window and Dome Database (IRDB) is intended to aid designers for materials selection. A 

designer must typically select a window/dome material by identifying bounds on material properties that 

cannot be exceed if reliable performance is to be achieved. An initial consideration is the passband and 

flexural strength, which quickly eliminates materials. Next, relative advantages and disadvantages may be 

applied to narrow the selection. The selection is further narrowed as other requirements are identified. 

Structural metals 

The final NAMIIS numeric module in development will cover the three most common structural metals and 

their alloys (Aluminum, Steel, and Titanium). It will act in a similar fashion to IRDB; however, it will 

contain different property sets. To date, the database module contains over 1000 data sets compiled from 

over 150 reports. The same software tools present in the IRDB will be used for Structural metals. 

Summary 

Through NAMIS, AMPTIAC is trying to save the DoD materials and process knowledge base making it 

readily available to the materials community. This will reduce duplication of effort and help transition the 

technology. Additionally, NAMIS will cut the time and cost of materials selection by giving designers a 

source for reliable and pedigreed materials data. 

AMPTIAC is boldly entering uncharted waters with a web-based database, which has the proper security 

precautions to handle export-controlled data. Lastly, unrestricted portions of NAMIS are viewable at the 

foilowing URL: httD: *:namis.iitri.org,' 
Acknowledgements 

1 would like to thank Beth Kinman and the other members of the High Temple index committee listed 

below for providing the kernel for our keyword index. 

Ray Adsit 

Glenn Anderson 

Michael Brunner 

Mike Holl 

Lew Lineberger 

Wanda Sigur 

Brian Wilson 

Bob Acree 

I would also like to thank Ron Kuhbander, Jim Folk and Daniel McCray for supplying early High Temple 

Workshop proceedings and Brett Bolan (AFRLMLS), John Russell (AFRLMLB) and Jim Sutter (NASAGlenn) for sponsoring the High Temple Module. 

I would like to thank Michael Stropki (AFRL/MLO) who sponsored the NASP module and Jack Rike 

(DTIC-0) who provided electronic copies of the reports to AMPTIAC. 

I would like to thank Mark Opeka (NSWC Code 68 1 ) for sponsoring and providing materials for the Cocoa 

Beach Module. 

Finally, 1 would like to thank our core sponsor and program manager Mr. Ron E. Hale at the Defense 

Technical Information Center and his technical representative Dr. Lewis E. Sloter I1 at the Office of the 

Director Defense Research and Engineering (Weapons Systems). 

I would also like to thank Dr. Sloter's associate technical representatives as follows: 

Ceramics, Ceramic Composites 

Organic Structures Materials & 

Organic Matrix Composites 

Metals, Metal Matrix Composites 

Electronics. Optical, 8: Photonics 

Environmental Protection & 

Special Function Materials 

Dr. S. Carlos Sanday 

Naval Research Laboratory 

Mr. Roger Griswold 

Air Force Research Laboratory 

Dr. Joe Wells 

Army Research Laboratory 

Mr. Robert L. Denison 

Air Force Research Laboratory 

Dr. James Murday 

Naval Research Laboratory 
Durability Characterization of Advancec Polymeric Composites at Cryogenic Temperatures 

THOMAS S. GATES 

Mechanics and Durability Branch/Mail Stop 188E 

Langley Research Center 

Hampton, VA 2368 I USA 

Phone: 757-864-3400 

Fax: 757-864-7729 

E-mail: T.S.Gates@larc.nasa.Irov I 

The next generation of reusable launch vehicles will require technology development in 

several key areas. Of these key areas, the development of polymeric composite cryogenic fuel tanks 

promises to present one of the most difficult technical challenges. It is envisioned that a polymer 

matrix composite (PMC) tank would be a large shell structure capable of containing cryogenic fuels 

and carrying a range of structural loads. The criteria that will be imposed on such a design include 

reduced weight, conformal geometry, and impermeability. It is this last criterion, impermeability, that 

will provide the focus of this paper. 

design lifetime. To address this criterion, one of the first steps is to conduct a complete durability 

assessment of the PMC materials. At Langley Research Center, a durability assessment of promising 

new polyimide-based PMCs is underway. This durability program has focused on designing a set of 

critical laboratory experiments that will determine fundamental material properties under combined 

thermal-mechanical loading at cryogenic temperatures. The test program provides measurements of 

lamina and laminate properties, including strength, stiffness, and fracture toughness. The 

performance of the PMC materials is monitored as a function of exposure conditions and aging time. 

Residual properties after exposure are measured at cryogenic temperatures and provide quantitative 

values of residual strength and stiffness. Primary degradation mechanisms and the associated 

damage modes are measured with both destructive and nondestructive techniques. In addition to 

mechanical properties, a range of physical properties, such as weight, glass transition, and crack 

density, are measured and correlated with the test conditions. This paper will report on the progress 

of this research program and present critical results and illustrative examples of current findings. 

The essence of the impermeability criterion is that the tank remains leak free throughout its 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

htfp://ampef. rnsfcnasa. gov 
DEVELOPMENT OF METAL MATRIX COMPOSITES FOR NASA’s 

ADVANCED PROPULSION SYSTEMS 

Jonathan Lee and Sandy Elam 

National Aeronautics and Space Administration (NASA) 

Marshall Space Flight Center (MSFC) 

Mail Code ED33 

Huntsvillc. AL 32812 I Jonathan.Lee(tr msfc.nasa.gov 1 

ABSTRACT 

The state-of-the-art development of several Metal Matrix Composites (MMC) for NASA’s 

advanced propulsion systems will be presented. The goal is to provide an overview of NASA-Marshall 

Space Flight Center’s on-going activities in MMC components for advanced liquid rocket engines such as 

the X-33 vehicle‘s Aerospike engine and X-34‘s Fastrac engine. The focus will be on lightweight, low cost 

and environmental compatibility with oxygen and hydrogen of key MMC materials, within each of 

NASA’s new propulsion application, that will provide a high payoff for NASA’s Reusable Launch 

Vehicles and space access vehicles. In order to fabricate structures from MMC, effective joining methods 

must be developed to join MMC to the same or to different monolithic alloys. Therefore. a qualitative 

assessment of MMC’s welding and joining techniques will be outlined. 

INTRODUCTION 

In this paper. the state-of-the-art development of Metal Matrix Composites (MMC) for NASA‘s 

advanced propulsion systems will be presented. The focusing theme will be on lightweight, affordable and 

environmental compatibility with oxygen and hydrogen of key MMC materials that will provide a high 

payoff for NASA‘s rcusablc launch vehicle systems and space access vehicles. Historically, MMC has 

been used for NASA’s flight hardware such as boron fibcrs reinforced aluminum struts for the Space 

Shuttle’s mid-fuselage in 1982. and graphite fibcrs reinforced aluminum antenna for the Hubble Space 

Telescope in 1990 (ref. I ). However, these types of MMC wcre costly to produce and were not developed 

specifically for propulsion systems. 

In recent years, Marshall Space Flight Center (MSFC) has been focusing on the development of 

low cost and lightweight components using net shape casting for advanced propulsion systems. which 

commonly have high density copper alloys and superalloys. In order to improve the engine thrust-toweight ratio for advanced launch vehicles, lighter materials with new fabricating methods must be 

developed using concurrent engineering method (ref. 2). MMC are often valued for their “tailor-ability” 

property, which dictates a specific MMC formation for a specific application. For this reason, complexity 

and cost for the development of an MMC property database can often be more than for a conventional alloy 

database, which favors a “commodity” approach. In the commodity approach, the conventional practice is 

based on one single alloy formulation to bc used for many structural applications. For MMC, material 

spccialists and engine’s designers must work closely during the early phases of the program to develop a 

specific MMC property database for a specific application. As part of the planning stage, the Technology 

Readiness Level (TRL) for material, joining processes and the cost affordability factor havc become 

important development issues for MSFC’s material sclcction strategy. 
MATERIAL AND PROCESS SELECTIONS 

Material Selections 

Technology assessment has shown that Discontinuously Reinforced Aluminum (DRA) MMC can 

become viable candidate materials for propulsion applications in cryogenic and near ambient temperatures. 

Evidently, the development cost for DRA is affordable and the TRL is relatively high such that production 

of complex DRA components have been applied for the auto industry with high dimensional tolerance and 

minimal machining requirements (ref. 3,4, 5). Figure I shows the comparison for the specific stiffness 

(modulus/density) of DRA, which is better than most conventional superalloys being used in propulsion 

hardware, DRA also acquire its toughness and ductility from the aluminum and will bchavc more like 

conventional aluminum alloys due to its isotropic properties (ref. 6. 7). On the other hand, isotropic 

property also means that DRA would tend to have lower specific strength value (strength/’density) as 

compared with Continuously Reinforced Aluminum (CRA) with fibers such as silicon carbide, aluminum 

oxide, etc. Therefore, the selection strategy is to substitute DRA for stiffness-driven applications and CRA 

for strength-driven and unidirectional loading applications at cryogenic and near ambient temperatures. 

Similarly, copper MMC can become viable candidate materials for oxygen-rich environment at 

relatively high temperatures and pressures. However, coppcr MMC have not been extensively used for 

commercial applications as compared with aluminum MMC. Technology assessment of nickel and copper 

MMC programs, funded by the DoD and NASA in recent years, indicated that these high temperature 

MMC are not as “mature” as aluminum MMC (ref. 8, 9). However, the current development for 

Discontinuously Reinforced Copper (DRC) appears to be morc viable technology than Continuously 

Reinforced Copper (CRC) for certain types of stiffness-drivcn applications in oxygcn-rich environment. 

-200 

3 

sl50 

W 

h 

U 

v) 

.L 

5 

m 

1 

v) 

v) 

&OD 

4 

3;. Steel 

Fiber AI MMC [ /(Transverse direction) 

AI-L .i 2 1 

lNCO718 INCO718 t (cast) (wrought) 34 7 

(cast) MCO 625 

(cast) 

Fiber AI 

(longitudinal 

95 

310° 6f O qoo l$OO -50 

S trength/densi ty (ksi/l b/in3) 

MMC 

direction) 

1qoo 

Figure I. Plot of specific stiffness versus specific strength for AI MMC. 
Process Selections 

Similar to material selection, the strategy for process selection is bascd on low cost and capability 

for nct shape fabrication with minimal machining and wclding requirements. In order to evaluate these 

fabricating processes as a function of component applications, forms (shapes) and materials, a ranking 

matrix is developed for the fabricating processes, which can be classified into 7 classes as shown in Figure 

2. Each of these techniques consists of unique features that are grouped in terms of applications, product 

forms and materials. For example, diffusion bonding is a choice method for continuous fibers MMC. 

which is applicable for unidirectional loading applications such landing gear, struts, beam, etc. 

Historically. diffusion bonding has been used for NASA's flight hardware such as MMC struts for thc 

Space Shuttle's mid-fuselage and antenna for the Hubble Space Telescope. However, these types of MMC 

were costly to produce and not directly applicable for making complex near net shapes such as turbopump 

housings. In summary, pressure infiltration and gravity casting were selected as primary level processes 

because they are the most versatile for producing complex net shape components with relatively low 

processing cost. Secondary processing level would be selected as spray deposition and centrifugal casting 

for fabricating of simple net shape components. Finally, powder metallurgy and laser 3D deposition 

processes are selected as a third level for wrought products for airframe applications with near isotropic 

properties. In some instanccs, powder metallurgy can be used to produce simple net shaped components. 

Currcntly. Laser 3D deposition is an emerging technology with limited data for MMC assessment. 

A Relative Cost 

High q- LOW 

MMC's Fabricating Methods 

~1 Ultra-high strength 

Wear resistance moo 

Thick plates & blocks e 0 

0.00 

0 

a. 0 

'L 9 Thin plates & sheets c) Large cylindrical shells 

'0 

0 Tubes. rods & beams 

'Simplenear net shapes 

Comolex near net shaDes a 

*?Continuous fibers & taues 0 I I I 

2 Chopped & short fibers 

Particulate & whiskers 

Hybrid systems 

Figure 3. Qualitative assessment for MMC fabricating methods. 
ENVIRONMENTAL COMPATIBILITY 

The material compatibility with oxygen and hydrogen environment has always been an important 

issue for rocket propulsion systems (ref: IO). Preliminary assessment has shown that aluminum alloys and 

aluminum MMC are considered to be compatible with oxygen environment only at low pressure (<I500 

psi) and cryogenic temperature. Therefore, aluminum MMC can be used for ducts, flanges and turbopuinp 

housings that operate at cryogenic temperature and low pressure. From near ambient temperature up to 

about 900 F, copper-based MMC are compatible with high pressure oxygen-rich environment. The 

development of copper alloys reinforced with aluminum-oxide particulate and/or fibers, have shown to be 

compatible with oxygen environment. On-going efforts are under way at MSFC to characterize the 

material compatibility issues in an oxygen-rich environment for aluminum and copper based MMC. 

Currently, titanium based MMC are not recommended for oxygen environment even at cryogenic 

temperature. For hydrogen environment, aluminum and copper-based MMC are shown to be coinpatible in 

a wide range of operating temperatures and pressures. However, some titanium MMC are compatible with 

hydrogen only at cryogenic temperatures. In contrast with polymer matrix composites, the hydrogen 

permeation is not an issue for most metals and MMC. This is an important compatibility factor for MMC 

in the design consideration of ducts, flanges and pressure vessels for hydrogen containment applications. 

COMPONENT SELECTION FOR DEMONSTRATION 

Flanges for Fuel Line 

There is a significant amount of mass associated with the usage of superalloy’s ducts and flanges 

for the fuel feed lines of the X-33’s Aerospike engine. The ducts are identified as strength-driven 

components. which will be made from lightweight nanophase aluminum or aluminum-lithium alloys in the 

future. The flanges are stiffness-driven components, which are ideal targets for weight reduction using 

particulate reinforced aluminum MMC such as boron carbide (B,C), silicon carbide (Sic) or aluminum 

oxide ( AI2O3). With SIC reinforced aluminum MMC, a 55% mass reduction over conventional IN 625 can 

be expected for each of the flanges. Significant total weight reduction can be expected since there are 

approximately 36 flanges for the combined oxygen and hydrogen side for the feed lines of the Aerospike 

engine. The potential technical issue is to develop appropriate techniques for joining the aluminum-lithium, 

aluminuin alloys or nanophase aluminum ducts to AI MMC flanges. Figure 3 shows several prototype 

aluminum MMC flanges that were produced by Metal Matrix Cast Composites (MMCC) Inc. using 

advanced pressure infiltrated casting. 

Figure 3. AI MMC prototype flanges for X-33’s fuel line ducts. 
X-33 Engine’s Thrustcell 

The X33’s aerospikc engine consists of several thrust cells which can comprise as much as 25% of 

tlie cngine weight. The interior wall of the thrust cell chamber is exposed to high temperature combustion 

products and must be cooled by using liquid hydrogen. Currently, the structural jacket and manifolding of 

the thrust cell chamber is made of stainless steel (SS) 347, which can potentially be replaced with a lighter 

material by using aluminum MMC. Up to 50% mass reduction over conventional SS 347 can be expected 

for each of the thrust cell chambers using MMC. To demonstrate the level of maturity for aluminum MMC 

technology, several MMC chambers have been produced using gravity casting and plasma spray deposition 

process. In addition to MMC, a new copper alloy (Cu-8Cr-4Nb), that has higher strength than the 

traditional copper alloy of NARloy-% for chamber liners. is also being investigated in this program. 

Currently, several thrust chamber design concepts are being worked to resolve the potential technical issue 

of bonding or brazing the liquid hydrogen cooled Cu-Cr-Nb liner to the surrounding MMC jacket. For 

instancc, Figurc 4 shows an MMC chamber, made from an AIiSiC MMC jacket, which is cast around a 

copper liner in a “one-step” brazing-casting process under gravity casting by MSE Technology 

Applications, Inc. 

Figure -1. AI MMC prototype “lightweight” thrust chamber for thrust cell applications. 

X-34’s TurboDumr, Housing 

Preliminary analysis has shown that up to 40% mass reduction over conventional cast INCO 7 18 

superalloy can be expected for tlie X-34’s Fastrac engine turbopump housing. Thc candidate material 

under consideration is a hybrid aluminum MMC system that consists of a mixture of aluminum oxide 

(A1?O3) continuous fibers and A1203 particulate. For this reason, the key material challenge is to develop a 

capability to manufacture hybrid MMC, with selectively reinforced fibers for high strength in proper high 

stress locations, using pressure infiltrated casting. This AI MMC technology is targeted for new hydrogen 

or hydrocarbon turbopumps and is also applicable to low-pressure oxygen turbopump at cryogenic 

temperature. If successti~l, many rocket systems such as the Venture Star, Long Life Bantam engine 

variations and rocket based combined cycle systems will benefit by the weight reduction achieved from this 

AI MMC for the X-34’s turbopump housing demonstration program. Figurc 5 shows a half-scale X-34’s 

turbopump housing which was produced by MMCC, Inc. using advanced pressure infiltration casting of 

aluminum alloy reinforced with 5096 by volume of aluminum oxide particulatc. 
Figure 5. Half-scale AI MMC turbopump housing for X-34’s Fastrac Engine 

AI MMC ducts 

Preliminary analysis of cryogenic feedlines and ducts has indicated that up to 309.0 weight redution 

can be achieved by using MMC reinforced with continuous alumina fibers. This is based primarily on the 

hoop strength of such a brazed aluminum composite relative to the strength of an Inconel feedline as used 

on the X-34 vehicle technology demonstrator. Under NASA sponsorship, this novel MMC matcrial tape 

concept has been developed by Touchstone Research Laboratory (TRL). for making lightweight MMC 

ducts from prepreg unidirectional tape produced by 3M. This unique MMC prepreg unidirectional tape 

form can be laid-up as plies with the plies oriented to meet the component performance requirements in an 

analogous manner to polymer matrix composites. These plics can then be consolidated using TRL’s 

patented brazing process. Theoretically, TRL’s solution incorporates a very thin MMC tape with an 

automated brazing technique that combines the ability to produce propellant feedlines with inherent low 

cost of polymer manufacturing technique but it could achieve a better interlaminar strength than polymer 

composites. This technology demonstration of brazed continuous aluminum MMC tape for propellant 

feedlines and ducts could have direct application to cryogenic tanks and airframe structure as well. Figure 

6 shows a small section of a cryogenic duct that is produced by using a continuous in-situ brazing process 

for a ?-ply hoop wound cylindrical section with a diameter of 5 inches. 

Figure 6. A small section ofa cryogenic duct produced by brazing MMC tape. 
QLALITATIVE ASSESSMENT FOR JOINING TECHNOLOGIES 

In order to fabricate structures from MMC, effective joining methods must be developed to join 

MMC to thc same or to different monolithic alloys. Since MMC utilize a variety ofnon-metallic 

reinforcements. they will naturally impose limitations for joining using conventional methods from 

monolithic metals. As a general rule, the adaptability of any joining techniques for MMC will depend on 

the combination of the following factors: ( 1) the volume percent amount and types ofreinforcements, (2) 

metal matrix melting point, and (3) the thermal energy management from the selected joining process. 

Discontinuously reinforced MMC are easier to join than continuously reinforced using fi bcrs, which are 

prone to matrix-fiber de-bonding, de-lamination, non-uniform fiber packing density and migration of fiber 

bundles into the weld regions. The prolonged contact time between a molten metal matrix and a 

reinforcement can lead to undesirable chemical reactions, which are accelerated as the molten metal 

temperature increases. Although high thermal energy is required for most conventional joining processes, 

excessive thermal energy input is undesirable. For this reason, the higher the metal matrix melting 

temperature the less likely for most of the fusion techniques to be applicable for MMC. A qualitative 

assessment ofthe adaptability of 17 monolithic joining techniques to MMC is summarized in Figure 7 (ref. 

I 1 ), It is important to realize that MMC joining is not a mature technology and many important joining 

technical details are still lacking. Consequently, the adaptability for a specific joining method is a specific 

matcrial and process factor which must be determined experimentally (ref. 12. 13). 

Joint Applications 

Fnction stir welding 

Ultrasonic welding 

Diffiision bonding 

mCapacitor discharge 

Soldering 

4 Adhesive bonding 

Cast-insert joining 01% 

I z 

0 

0 

0 

0 

- 

/ 

a 

00 

00 

00 

00 

00 

00 

00 

IO 0 

00 

00 

00 

00 

00 

BO 

go 

BO 

me 

/ 

Joint Perromance Rating: 0 High Medium Low 

Figure 7. Qualitative assessment rating for MMC joining methods. 
CONCLUSIONS 

Technology readiness level for materials. joining processes and the cost affordability havc bccome 

important issues tor NASA in developing MMC for advanced propulsion systems. Discontinuously 

reinforced aluminum (DRA) are viable candidate materials for propulsion applications and they can be 

substituted for component with stiffness-driven applications at cryogenic and near ambient temperatures. 

Similarly, copper MMC are viable candidate materials for in oxygen-rich environment at relatively high 

temperature and pressure. A qualitative assessinent for joining methods has shown that thc use of solid 

state and low temperature processes are oftcn more adaptable for joining of MMC than thc use of high 

temperature fusion processes. 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

IO. 

11. 

12. 

13. 

REFERENCES 

Reinhart, J. J.: “Engineered Materials Handbook. Volume 1 : Composites,” ASM International, Metal 

Park. OH, p. 856, 1987. 

Watennan, N. A.; Ashby, M. F.: “The Materials Selector,” 2”“ edition, Chapman-Hill, NY. 1947. 

Rohatgi, P.: “Cast Aluminum Matrix Composites for Automotive Applications.” Journal of Metals, pp. 

10-15. April 1491. 

Mangin, G. E.; Isaacs, J. A,: “MMC for Automotive Engine Applications.” J. Metals, p. 49. Feb. 1946. 

Hammond, D.E.: “Castable Composites Target New Applications.” Modern Casting, p. 27. 91 1990. 

Lee, J. A.: “High Strength Aluminum Casting Alloy for High Temperature Applications,” MSFC, 

NASA/TM-1998-209004, December 1998. 

Lee. J. A.: “Low cost AI-Si Casting Alloy as In-situ Composites for High Temp. Applications,” 24Ih 

Conf. Composites, Structural. & Mat., Jan. 23,2000, Cape Canavcral. FL 

Lee, J. A.: Mykkanen, D.: “Metal and Polymer Matrix Composites,” Noyes Data Publisher, Park 

Ridge, New Jersey, 1987. 

Lee. J. A.: “Tungsten Fiber Reinforced Superalloy Metal Composites,” 23“’ Conf. on Composites, 

Structures & Materials, Jan. 23-28, 1999, Cocoa Beach , FL 

Lee, J. A.: “A Theory for Hydrogen Embrittlcment of Metals and Alloys,” In: Hydrogen Effects in 

Materials, A. W. Thompson (eds.), TMS publication, 1995. 

Lee, J. A.: “Qualitative Assessment for MMC Joining Methods,” Mil-Hdbk- 17-4, V4. Sept 2 1, 1999. 

Lee, J. A.; Carter, R. and Ding, J.: “Friction Stir Welding for Aluminum Metal Matrix Composites,” 

MSFC, NASAiTM- 1999-209876, December 1999. 

Lee, J. A.; Kashalika, U.: “Casting of Weldable GraphiteiMagnesium MMC with Built-in Metal 

Inserts,” NASA Conf. 3249, VI, p. 371, Dec. 7, 1993, Anaheim, CA. 
INORGANIC-ORGANIC' HYBRID POLYMERS FOR HIGH TEMPERATURE AEROSPACE APPLICATIONS 

Teddy M. Keller 

Advanced Materials Section, Code 6127 

Chemistry Division 

Naval Research Laboratory 

Washington, DC 20375-5320 

Tel: 202-767-3095 

E- Mail 4 kc.tl~~~!,~~tc_r.~.!:.!ld.la..-l 1 

Introduction 

Our current interest in inorganic-organic linear hybrid polymers as precursors to high temperature 

thermosets and ceramics has led us to investigate the synthesis of novcl materials containing silicon, carborane, and 

acetylenic segments. Several poly(carborane-siloxane- acetylene)^ 1 ( 1 ) and 2 (2) and poly(si1oxane-acetylene)s 3 (3) 

are being evaluated as high temperature matrix materials for composites and as precursor materials to ceramics for 

applications under extreme environmental conditions. 

'I'hc major advantage of our approach is that the desirable features of inorganics and organics such as high 

thermal and oxidative stability and processability are incorporated into the same polymeric chain. The siloxane units 

provide thermal stability and chain flexibility to polymeric materials. Siloxane-acetylenic polymers have also been 

made but lack the thermal and oxidative stability that the carborane units possess. The chemistry involved in 

synthesizing poly( siloxane) and poly( carborane-siloxane) has been modified to accommodate the inclusion of an 

acetylenic unit in the backbone. The novel linear polymers have the advantage of being extremely easy to process 

and convert into thennosets or ceramics since they are either liquids at room temperature or low melting solids and 

are soluble in most organic solvents. They are designed as thennoset polymeric precursors. The cross-linking density 

of the thcrmosets is easily controlled as a function of the quantity of reactants uscd in the synthesis. The acetylenic 

functionality provides many attractive advantages rclativc to other cross-linking centcrs. The acetylene group 

remains inactive during processing at lower temperatures and reacts either thermally or photochcinically to form 

conjugated polymeric cross-links without the evolution of volatiles. 

This paper is concerned with the processability and thermo-oxidative properties of 1, 2 and the blending of 

1 and 3 in an attempt to arrive at similar thermoset and ceramic compositions as found for copolymer 2 upon 

thermal treatment. Thermal analysis studies were performed on thermosets and ceramics obtained from 1, 2 and 

various blends from 1 and 3a. 

Results and Discussion 

The synthesis of inorganic-organic linear hybrid polymers 1, 2 and 3 have been reported previously (1-3). Several 

molar mixtures (50/50. 25/75 and 10190) of 1 and 3a were prepared for cure and thermal analysis studies. 

Homogenous mixtures were obtained by dissolving the linear polymers 1 and 3a in THF. After thorough mixing, the 

solvent was reinoved by distillation at reduced pressure. The resulting mixtures as prepared were viscous 

coinpositions. However, gummy, semicrystalline compositions formed aftcr several days. Upon heating to IO0 "C. 

the mixtures existed as viscous liquids. 

DSC Studies. The theniial cure behaviors of the linear polymers 1 and 3 were examined using DSC analysis (sec 

Figure I ). Large exotherms peaking at 350 and 289 "C were observed for 1 and 3, respectively. Copolymers 2 have 

large exotherms peaking between 289 and 350 'IC. The exact position depends on the amount of 1 and 3 units 

present in the copolymer. For example, copolymer 2c shows a similar DSC thermogram with a strong exotherm at 

approximately 300 "C (4). These peaks were atttibutcd to the acetylene crosslinking reaction. A small broad 

exotherm was also apparent from about 150-235 "C due to the presence of a small amount of primary terminated 

acetylenic units. DSC analyses of blends of 1 and 3a show a homogeneous reaction initially to a thermoset. The 

DSC scans to 400 "C of the blends exhibit only one cure exotherm for each of' the compositions studied (see Figures 

2). For example, mole percent mixtures (10i90, 25/75 and 50iS0) of 1 and 3a display exotherms (polymerization 

rcaction) peaking at 396. 39X and 32X "C, respectively. It is apparent from the observed cure temperature for the 
blends that 3a being more reactive initially forms radicals that are not selective in the chain propagation reaction 

with the acetylenic units of both land 3a (5). Samples that have been heat treated to 400 "C do not exhibit 

characteristic exotlierniic transitions. 

Thermal and Oxidative Stability. The thermal and oxidative stability of 1, 2 and 3a was determined by heating at 

10 "C/min to 1000 "C by simultaneous TGAiDTA analysis. Pyrolysis of 1 to 1000 "C under a flow of nitrogcn 

resulted in a ceramic yield of 85%. Further heat treatment of the ceramic at 1000 "C for I:! hours resulted in no 

additional weight loss. When the ceramic material was cooled back to 50 "C and rescanned to 1000 "C in air, the 

sample gained weight (-2Y.O) attributed to surface oxidation. Further TGA aging studies of thc ceramic in air 

revealed that additional weight loss did not occur and that the sample actually increased in weight as observed 

previously. When heated in air to 1000 "C, the chars from 2a-c lose no mass. The char from 2d displayed only a 7'9; 

weight loss under the same conditions. No weight loss was observed on heating the char from 3c at 700°C and 

900°C for 16 hr and for 7 hr, respectively. Thus, this study demonstrated that the char from 2c, containing only onetenth the amount of carborane found in 1, exhibited the same outstanding thermo-oxidative stability. Thermal 

treatment of 3a to 1000 "C under inert conditions rcsulted in a char yield of 74'k The char retained the original 

shape without cracking. When heated to 1000 "C in an oxidizing environment, the char remained stable to -600 "C, 

before a gradual weight loss was observed resulting in an overall weight loss of 15% at 1000 "C. Moreover, an 

oxidative aging study on a charred sample showed a 2Xo/4 wcight loss after I5 hours at SO0 "C. 

73 73 

C=C-C=C-6-0-6-B HloC-Y-O-$, I I 

93 93 93 83 83 83 

X 

n 2a-d 

a, xJy = 50150 

b, xty = 25/75 

d, xty = 5/95 

c, xly = 10190 

3a, n=l 

3b, n=2 
- m 2- 

L 

: iL lc, 

0 

P)- 

I 

0- 

-1 - 

0 100 200 300 400 

TEMPERATURE ('C) 

Figure 1. DSC thermograms of 1 and 3a 

I I I 'I 

I 1 I I I I 

Temperature$) 

0 100 200 300 400 

Figure 2. DSC thermograms of various mixtures of 

(A) 10/90, (B) 25/75, and (C) 50150 

113a : 
The thermal and oxidative stability of various mixtures of 1 and 3a was determined to 1000 "C and 

I500 "C. When heated to 1000°C and 1500 "C under inert conditions. the various mixtures containing 1 and 3a 

afforded char yields of 79-80 and 77-7846, respectively. During the heat treatment, similar exothennic transitions 

(DTA) as found during the DSC scans were observed. Moreover, above 1000 "C, an exothermic transition is 

observed which is attributed to the formation ofcrystalline ceramic components such as Sic and BJC. Upon cooling, 

the carbon/ceramic masses were reheated to 1 500 "C in air. The oxidative stability of the charred mass was found to 

be a function of the amount of 1 present and the initial heat treatment. Charred samples obtained from heat treatment 

to IO00"C and 1500 "C of 10190, 25/75 and 50150 molar weight percent of I to 3a showed charred residues of 98, 

98, 99% and 90, 97, 98% respectively, when reheated in air. 

Oxidative Aging Studies. The stabilizing effect of the carborane unit on the thermo-oxidative properties of the 

cured polymeric compositions is apparent from oxidative aging studies at elevated temperatures. The aging studies 

were performed by TGA analyses on small samples of the thennosets. Conversion to the thermosets of the 

carborane-siloxane-acetylene linear polymers 1 and 2a and siloxane-acetylene polymer 3a were achieved by tliennal 

treatment at various temperatures in an inert atmosphere. Aging of the thermosets from I and 2a was performed by 

heating the individual sample in sequence for 4 hr at 300, 350. 400, 450 and 510 "C in air. The thermoset from 3a 

commenced to lose weight during the 350 "C heat treatment in air and was only aged to 450 'IC. All of the samples 

gained weight during the oxidative exposure up to 350 "C. Extreme heat treatment of the carborane-containing 

thermosets at 400-510 "C showed an enhancement in oxidative stability relative to a similar sample from 3a (see 

Figure 3). The thermosets from 1 and the 50/50 copolymer 2a exhibited outstanding oxidative performance during 

the entire heat exposure. When 3 was cured and aged under identical environmental conditions, the sample gained 

almost 5.5 % weight during the heat exposure at 300 "C. Further heat treatment at 350 "C resulted in a small weight 

loss (1.6 96). When aged at 400 and 450 "C, an acceleration in the degradation process was observed. The heat 

treatment between 350 and 450 "C resulted in a weight loss of about 28 (YO. These results show the importance of 

boron at enhancing the oxidative stability of a polyincric niaterial through the formation of a passive protective layer 

that protects the interior against oxidation. 

110 

- 100 E 

E 

w .- 

5 90 

80 

Thermoset2 

2hermoset3 

600 

500 

o^ 

E 

400 (L 

3 

c. 

300 $ 

E" 

200 

100 

0 

0 200 400 600 800 1000 1200 1400 

Time (min) 

Figure 3. Oxidative Aging Studies on Thermosets from 1, 2, and 3a 
isothermal studies were performed on the thermosets derived from various blending compositions of 1 and 

3a. The compositions were cured by heating at 200, 250, 350 and 450 "C for 4 hr at each temperature under a 

nitrogen atmosphere. Aging of the thermoset was studied by heating the sample in air for 5 hr in sequence at 250, 

300. 350 and 400 "C followed by 15 hr at 450 "C. Copolymer 2c and the 10i90 composition showed similar thennooxidative stability upon conversion into a thermoset. The stabilizing effect of the carborane unit was apparent. All of 

the saniples gained weight during the oxidative exposure up to 350 "C. Moreover. less oxidation occurred on the 

surface as the amount of 1 increased. More extreme heat treatment at 400 and 450 "C' showed an enhancement in 

oxidative stability with greater amounts of carborane (see Figure 4). The 50150 mixture exhibited outstanding 

oxidative performance during the entire heat exposure. When 3a was cured and aged under identical conditions, the 

sample gained almost 7% during the heat exposures from 200 to 300 "C. While at 350 and 400 "C, the sample had 

lost about 14% weight. Upon exposure at 450 "C for 5 hours, the sample lost another 25% weight. These results 

show that boron enhanced the long-term oxidative stability of the polymeric materials. 

Long-term oxidative studies were also performed on the chars obtained from blending compositions of 1 

and 3a. A ceramic composition prepared from the 10/90 mixture was initially processed to 1000 "C under a nitrogen 

atmosphere. Upon cooling, the char was aged in sequence at 400, 500, 600 and 700 "C in a flow of air for 5 hours at 

each temperature (see Figure 5). While at 500 "C, the char gained about 0.3% weight. During the entire heat 

treatment. the ceramic sample lost less than 1% weight. This weight loss occurred between 500 and 600 "C. At 700 

"C, no weight changes were observed. Similar results had been observed previously for the copolymer 2c (6). A 

charred sample that had been processed from 3a in an identical manner as the blended mixture showed a 28% 

weight loss after 15 hours in air at 500 "C. The outer surface of the sample was coated with a white flaky residue 

attributed to silicon oxide. The outer surface of the chars formed from the blended mixtures upon exposure to air at 

elevated temperatures remained black. This observation indicates that a different outer oxidized surface forms with 

structural integrity when boron is present. 

oi1/3a: (A) 10190, (Bl 25/75, and (C) 501'50 
A-...lll-l"ll " 

I00 102F==--1

600 

- 

- 

92 - 

90 * ' I I I I I 1 

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9 

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Figure 5. Oxidative aging study on char from 10190 molar amount of 113a 

Conclusions 

Extreme aging conditions show the importance of silicon and boron in the protection of carbon-based 

systems against oxidation. Thermoset and ceramic coinpositions formed from 1, 2 and mixtures of 1 and 3a show 

outstanding oxidative stability up to 5 IO "C. The precursor linear compounds contain acetylenic units for thermal 

conversion to network polymers. The resistance to oxidation of the thennosets and ceramics in 2 and mixtures of 1 

and 3a was a function of the amount of 1 present in the polymeric mixtures. The studies show that carbon can be 

protected from oxidation at various temperatures by proper incorporation of silicon and boron units into a carbon 

precursor material. The observations indicate that a protective outer layer forms, when boron is present, and 

insulates the interior against further oxidation. The ceramic coinpositions obtained from 2 itself and mixture of 1 and 

3a show similar oxidative stabilities. Further studies are underway to evaluate and exploit the polymeric 

thermosetting and ceramic compositions as matrix materials for high temperature composites. 

Acknowledgment is made to thc Office of Naval Research for financial support of this work. 

Reference 

I. 

A. 7 

3. 

4. 

5. 

6. 

Henderson, L. J.; Keller, T. M. MacwnzoIoctr1r.s 1994, 27, 1660 

Son, D. Y.; Keller, T. M. J. Polym.Sci.: Purr A: Poljmz. Cllrni. 1995, 33, 2969 

Son, D. Y.: Keller, T. M. Macromolecules 1995,2N, 399 

Son, D. Y.: Kcller, T. M., Fire aud Po/iwier.r If; Gordon L. Nelson; ACS Symposium Series 599. American 

Chemical Society. 1995 edition, Chapter 19, p. 180 

Sastri, S. B.: Keller, T. M.: Jones, K. M.: Armistead, J. P. Mcrcroniolccules, 1993, 26(23),6171 

Keller, T. M.; Son, D. Y., Polynzeric Mureria1.v Encyclopedia: Joseph C. Salamone; CRC Press: New York 

1996; Vol. 5(H-L), p. 3262 
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3,d;y Session 04 - Evahiatiori of Cleaning and Bonding Materiais and Rocesses /?,3 5 

A Mass Spectrometer-Based Tool for In-Process Analysis of RSRM Components 

MICHAEL MELTZER 

Lawrence Livermore National Laboratory/L-627 

7000 East Avenue 

Livermore, CA 94550-9234 USA 

Phone: 925-424-6923 

Fax: 925-422-4038 

E-mail1 meltzer l@,llnl.Pov I 

Carolyn Koester 

Lawrence Livermore National Laboratory/L-542 

7000 East Avenue 

Livermore, CA 94550-9234 USA 

Phone: 925-422-6888 

Fax: 925-423-7998 

E-mail: boesterl @llnl.gov I 

Neil Sagers 

Thiokol Propulsion 

231 N. Burns 

Ogden, UT 84404 USA 

Phone: 435-863-61 16 

Fax: 43 5 - 8 63 - 5 509 

Work to date is reported for a project testing the capabilities of a mass spectrometer-based system for analyzing in-situ organic compounds on a variety of substrates. The system, which was built 

at Lawrence Livermore National Laboratory, is termed a Contamination Analysis Unit (CAU) and 

employs vacuum and thermal desorption of surface residues, followed by ionization and analysis 

with a Leybold Inficon Transpector mass spectrometer. The CAU was employed in this study to 

examine soils, cleaner residues, and substrates on Space Shuttle Reusable Solid Rocket Motor 

(RSRM) components. Project work was supported by Thiokol Propulsion. Major project objectives 

include: 

1. Determine if the CAU can detect solvent that has soaked into NBR insulation material 

2. Test the capabilities of the CAU for analyzing non-flat surfaces on the inside and outside 

surfaces of the RSRM and nozzle throat housing 

3. Determine if solvent extraction and gas chromatography approaches are able to enhance the 

surface analysis data available through use of the mass spectrometer-based CAU 

4. Determine the CAU’s detection limit for various RSRM soils and cleaners 

5. Determine if contact of either VitonR or silicon O-rings with critical substrates will result in 

any visual evidence of the contact, when observed under black light. 

6. Demonstrate CAU viability during routine RSRM manufacturing operations. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:/lampet. msfc. nasa.gov 
Effects and Detection of Silicone and HD2 Grease Contaminants 

.I. W. Blanks 

Thiokol Propulsion 

SEHO Operations 

P.O. Box 707, MIS 200 

Brigham City. Utah 84302 

ABSTRACT 

The bond integrity of RSRM bond systems can influence the overall system safety. The minimum level of 

different contaminants. especially silicone oils, present before various bond systems are weakened was evaluated. 

Application of an infrared spectrometer was used to detect and quantify sets of contaminants on selected composites 

and metal substrates. Techniques for applying the contaminants are discussed. Changes occurring with time at the 

contaminanti’substrate interface were monitored. Use was made of these techniques to prepare bond specimens for 

determining the lowest level of common contaminants that are detrimental to selected bond systems. 

INTRODUCTION 

Concern first and foremost for the safety of human life, and also the high cost of flight system hardware 

and payloads, has supported efforts to make the RSRM a dependable component in the Space Shuttle system. 

Although no major system failure has occurred because of contamination scenarios. specific bond failures do occur 

in laboratory prepared specimens from time to time. A search of eight years of computer archived reports on 

laboratory bond failure anomalies revealed the following information. 

1992 ~ Apparent failure mode shift at bonding interfaces of flexible boot assembly (phenolic/’CL-220/NBR). 

Analysis results: Failure influence by thin portion of NBR. Failure mode was determined cohesive in phenolic 

material. No contaminants such as silicone or hydrocarbons detected. 

1992 - sandblasted aluminum plateisilica filled EPDM rubber bond failure. 

Analysis results: No contaminants detected known to degrade these adhesive bonds. 

1992 - Adhesive failure of paint chips at Chemlok to metal case bond. 

Analysis results: No detected silicone or hydrocarbon contaminant. 

1994 - Monel wire mesh unbond in polysulfide peel tabs. 

Analysis results: exposed wire mesh exhibited traces of hydrocarbon, which may have acted as mold release. 

1994 - Failed tensile adhesion buttons, EA91 3/primer/metal interface. 

Analysis results: Examined to verify presence of primer. Primer not detected. Examination revealed thin layer of 

EA91 3 on metal surface therefore cohesive failure. 

1995 ~ RTVI’RTV unbond where voids were backfilled. 

Analysis results: CONOCO HD-2 grease present on surface of cured RTV. 

1995 ~ Adhesive failure of cork to zinc rich primer. 

Analysis results - Primer solvents detected. Perhaps not enough primer drying time. 

Copyright 2000 Thiokol Propulsion, a division of Cordant Technologies, Inc., All rights reserved. 

Approved for public release; distribution is unlimited. 
1996 - Weak bond strength within Chemlok 236. 

Analysis results: No obvious chemical reason revealed for the failure. 

1996 ~ Liner to liner separation. TL-H755/TL-H770 

Analysis results: Adhesive mixes noted as not being mixed uniformly evidenced by pockets of uncured adhesive in 

bulk of material. No contaminants detected. 

I998 - Bond study - 0.5 nigift- silicone can weaken EA-9 13iD6AC steel bond system to an unacceptable level. 

Processing errors, such as insufficient drying time or abnormal component thickness caused several of the 

above anomalies. Contaminants are only seldom detected. The most common surface sampling technique consists 

of chloroform wipe followed by infrared analysis of extracted material. Common contaminants requested for 

detection include various tape adhesive residues, silicone, hydrocarbon oils and greases, HD-2 grease. dirt. vacuum 

putty, and poorly mixed materials. Improvements in instrumentation now allow direct spectra collection on the 

suspect surfice and much lower detection limits, especially on grit blasted metal surfaces. 

The standard surface preparation for all bonded metal surfaces includes solvent cleaning and grit blasting 

stcps. Examination of these surfaces before bonding shows only microscopic traces of grit blast media. Composite 

surfaces are solvent cleaned before bonding. 

Although the initial intent of this paper was to report results from a broad bond study to correlate silicone 

contaminant levels on numerous RSRM bond interfaces. that program was delayed while various other 

contamination issues were resolved. Therefore, this paper now entails discussion and results of several 

contamination issues. 

Composites 

After years of evaluating various analytical tools to detect and quantify contaminants on metal surfaces, an 

infrared spectrometer, model SOC400, was selected as the primary choice. Other tools examined included near 

infrared spectrometers. Flash UV Imaging system, OSEE. and black light. The Flask UV Imaging system is 

applicable to fluorescing contaminants. Since contaminants occasionally appear on composite surfaces, experiments 

were performed to determine the best tool for this type problem. Composites evaluated included surfaces of silica 

glass phenolic (SGP), carbon cloth phenolic (CCP), fiberglass phenolic (FGP), and graphite epoxy (GE). A set of 

D6AC steel coupons was contaminated at the same level. 

Standards 

Calibration standards were prepared using an ultrasonic sprayer made by Sono-Tek Corporation. A 

solution of HD-2 grease dissolved in methyl chloroform was sprayed onto 2x3 inch composite coupons. The 

quantity of applied contaminant was determined by simultaneously spraying a tared foil specimen, weighing the foil 

after drying and assuming the concentration ofcontaminant on the coupon and foil were identical. The target levels 

were I. 5, IO, and 20 mgisqft. The measured levels are displayed in Table I. 

r 

Spectra were collected on the SOC400 Fourier transform infrared spectrophotometer, 50 scans, 4 cm-' 

resolution. 3000 to 650 cm-' spectral width. at a non-contact head distance of 0.04-0.06 inches. The 2x3 inch 

coupons were examined at 9 equally spaced locations to obtain an average contaminant value. A background or 

reference spectrum was taken on clean grit blasted D6AC steel. Spectra were initially taken on specimens of each 

clean composite. Significant variation was detected in the spectra at different locations depending on the relative 

ratios of binder to filler in the field of vision. The spectral energy reflected from the composites containing carbon 

and graphite was quite low compared to the energy from the other type composites containing no carbon 

polymorphs. The model for HD3 grease on the D6AC steel is presented in Figure 1 showing a linear relationship 
between HD2 grease and absorption at two selected wavelengths. The infrared peak at 2922 cm ' is due to the 

hydrocarbon in HD2 grease, while the peak at 1409 cm-' is from a carbonate constituent. Past calibration models for 

HD2 grease on steel and aluminum have chosen the 1409 cni-' peak for most accurate quantification. However when 

one looks for this peak in the spectra of the HD2 grease contaminated composites, no peak is detected. Either the 

carbonate reacts with some component on the composite surface or it is hiding in holes on the surface. Figure 2 

displays the models for the composites using the peak at 2922 cm-'. Even this peak is not observed in the spectra of 

some of the composites. The constituents of the composites exhibit major infrared peaks. To actually detect and 

measure the HD2 grease peak requires subtracting the average clean composite spectrum from each HD2 

contaminated same type composite spectrum. Ideally this subtraction removes all the composite peaks leaving only 

HD2 absorption. 

Application of the Flash UV Fluorescence Imaging system to the composite standards with HD2 grease 

produced the models displayed in Figure 3. The fluorescence data shows a valid correlation ofHD2 fluorescence 

with concentration down to about 5 mgkqft for all four types ofcomposites. As with the infrared data the 

composites containing carbon absorb much of the energy, from either the flash UV andlor the fluorescence. 

Contec Wipes Issue 

A recent issue at KSC involved the observation that certain batches of Contec wipe cloths exhibited 

abnormal fluorescence under black light. Some fluoresced only at the seamed edge, others fluoresced everywhere. 

while some showed spots and streaks. Because the Flash UV source is high intensity, examination of the wipes 

with the Flash UV Imaging system indicates all the wipes fluoresce to some degree. lnitial investigation found the 

yarn used to serge the cloth edge contained silicone. Immediate silicone panic lead to numerous tests. Was silicone 

transferred to wiped surfaces? 

Grit blasted steel panels were wiped with Contec wipes using a standard wipe procedure. First with wipe 

wet with the Reveille solvent followed by a dry wipe. Two lots of wipes were tested. Diffuse retlectance spectra 

were collected by SOC400 FTIR. 

A wipe from the first lot fluoresced under black light only at the serged edge. A panel wiped with the first 

lot was examined at nine locations. A typical spectrum is displayed in Figure 4. Similar spectra were observed at 

each location indicating uniform transfer of cloth components. The spectra exhibited major cellulose peaks, an ester 

peak from the serge yarn, and a doublet peak near 1250 cm-'. No conclusive indication of silicone could be made 

from the reflective spectra. 

The panel surface was extracted with chloroform. the extract dried and diluted to a specific volume, and a 

spectrum collected on this solution in a I mm sealed cell. Using a previously prepared calibration curve the silicone 

present on the panel was calculated to be -0.1 milligrams per square foot. 

Another panel was wiped with Contec wipes that fluoresced all over. The reflectance specm were similar to 

those from panel one. The panel was extracted with chloroform, dried, diluted to specific volume, and a spectrum 

collected in a Imm cell. This initial extraction found 0.7 mg/sqft silicone on the panel. A second and third 

extraction found 0.08 and 0.01 6 mg/'sqft silicone respectfully. A fourth extraction found no detectable silicone. 

There was little change in reflectance spectral features. shown in the bottom spectrum of Figure 4. of residue on the 

panel before and after each chloroform extraction. The Flash UV image of panel two indicated high fluorescence 

before and after each chloroform extraction. This observation indicates the fluorescing components are not soluble in 

chloroform. Microscopic examination of the residue on the panel revealed fibrous material. 
Experiment s to extract tlu-Donen t 

Samples of Contec wipes that fluoresce were extracted with various solvents attempting to remove the 

fluorescing components. Comparison of solvent effectiveness indicated water>ethyl alcohol>acetone>chloroform. 

Examination of material removed indicated discrete fluorescing particles. This observation supports the conclusion 

that the solvents are only dislodging particles of the brightening agent but not really dissolving them. 

Silane Adhesive Promoter 

Enhancement of epoxy bonds to steel was achieved years ago by use of silane bond promoters. 

Theoretically the silane forms a covalent chemical bond with oxides or hydroxide on the steel surface and ties into 

the crosslinking structure of the epoxy. The silane is applied in solution, which helps the penetration of the silane 

into the pores of the steel. Bond data supports the conclusion that silanes can overcome the bond inhibiting 

presence of trace amounts of many contaminants. Experiments are in progress to better understand the action and 

chemistry of the silane adhesive promoter. 

How much time at ambient conditions after applying the silane is required before bonds are formed 

between the silane and steel? The SOC400 can readily detect and quantify silane on grit blasted steel surfaces. 

Calibration was obtained by applying silane over a range of concentrations on steel coupons, collecting spectra at 

numerous locations on each coupon using the SOC400. washing the silane ti-om the coupons with chloroform, 

diluting to specific volume, and analyzing for silane by classical infrared in a sealed I mni cell. Calibration of 

silane in the lmm cell was accomplished using solution of known silane content, Figure 5. A model was prepared 

correlating silane absorbance versus concentration using diffiise reflectance spectra collected on the SOC400 FTIR. 

also Figure S. 

Silane in the 10-50 mg/sqft range was allowed to remain on four grit blasted steel coupons for three days, 

washed from the surfaces multiple times with chloroform and the dried surfaces examined by SOC400. Silane still 

remained on the surface at 1.7 to I .5 mg/sqft. The standard procedure is to apply silane for 1 to 3 hours before 

applying epoxy. An experiment in which silane was washed off after 3 hours found no silane detected on the dried 

surface. So how long is really best? The application for 1 to 3 hours seems to enhance the bond. More experiments 

are planned to answer this question. How much silane should be applied'! A range of silane was applied to a set of 

tapered double cantilever beams, the amount of silane measured by SOC400 and bond samples prepared. The bond 

data was similar for each silane concentration except the very lowest level; however. the silane remained on the 

beams two days before bond sample preparation due to analysis time and bond scheduling. More experiments need 

to be performed to quantify rates of silaneisteel bonding. 

Cleaning of Silicone from Grit Blasted Steel 

One of the problems holding up the test plan originally intended for this paper is the ability to remove 

silicone from tested bond specimens so they can be recycled to prepare more specimens. When silicone is applied to 

grit blasted steel it seems, over a period of contact time, to either diffuse deep into the pores of the steel or to bond 

to the surface such that washing with solvent does not remove all of it. If steel panels contaminated with even a 

small amount of silicone are grit blasted. the grit blasting apparatus will become silicone contaminated. Numerous 

solvents and cleaners were evaluated to find one effective in removing the silicone. 

DS I04 Cleane r 

A recent candidate includes DS 104. a brew of saturated hydrocarbons and acetates manufacture by 

Dynamold Solvent. Inc. Three steel plates were contaminated with greater than 100 milligrams per square foot of 

Dow 200 silicone oil and aged for one week. The plates were soaked for 15 minutes in the DS 104 solvent, flushed 
with this solvent, then washed with hot water. After drying 24 hours the plates were examined for silicone with the 

SOC400. Silicone was detected at approximately 0.4 to 0.6 mgisqft. Re-examination after placing in storage for 

several weeks found the silicone observable on the surface had increased to 0.7 to 0.9 mgisqft. Steel coupons 

contaminated with silicone oil and previously cleaned with DS 104 solvent were subjected to ultrasonic cleaning 

using the same type solvent, DS104. Examination using the SOC400 FTIR revealed two coupons still exhibit 

traces of silicone, 0.3 mgkqft. A third contaminated coupon and control coupon did not show silicone but had rust 

or stains on the surface. 

Wasatch clmine solution 

Another candidate cleaner consists of a solution of 2-methylethanol. mineral spirits. and sodium 

hydroxide. The alkaline nature of this solution will, supposedly, break down the silicone structure. Grit blasted 

steel 2x3 inch coupons (3) were coated with silicone, greater than 100 mgisqft, aged one week, soaked in the 

candidate cleaner for 15 minutes. flushed with the solution. washed with hot water, and dried. Examination by 

SOC400 found silicone on each coupon at about 1 nighqft. Examination after a week of storage found essentially 

the same silicone level. 

A successful solvent to remove all the silicone has at present not been found. Other candidates are under 

evaluation. 

SUMMARY AND CONCLUSIONS 

ComDosites 

Composites containing carbon polymorphs, carbon and graphite absorb essentially all the infrared energy 

and preclude valid models. The contaminant HD2 grease can be detected by infrared spectroscopy on composites not 

containing carbon and quantified down to approximately 5 mgisqft. The data manipulation, spectral subtraction, 

etc., to perform this task is tedious. Flash UV Fluorescence Imaging can quantify HD? grease on composites even 

those containing carbon to approximately 5 mg/sqft. 

Contec WiDq 

The silicone content of the Contec wipes that fluoresce all over is an order of magnitude higher than in 

those that fluoresce only at their serged edge. The major portion of residue transferred from wiping cloths to the 

steel grit blasted surface, whether fluorescing or non-fluorescing Contec, are similar. The composition is mostly the 

bulk cellulose cloth along with binder or sizing. During standard panel wipe procedure some of the bulk cellulose 

cloth and serge yam (polyester in Contec) are transferred with traces of silicone. The total silicone transferred in the 

worst case is less than I milligram per square foot. The ma,jor transfer mechanism is the very abrasive nature of the 

grit blasted surface and solubility of silicone in Reveille solvent. Reveille solvent dissolves the silicone from the 

serge yam. Reveille solvent does not dissolve the cloth yam, binders. sizing, or the fluorescing component present 

in the wipes. The fluorescing component on the Contec wipes is an inorganic fluorescing brightening agent. 

Silane Adhesi ve Promoter 

Silane adhesive promoters enhance the bond of epoxy to steel. Many questions remain unanswered as to 

what the chemistry is, how much to use for optimum results, and how long to wait before applying the epoxy for 

optimum bond formation. 

CleaninP of Silicone from Grit Blasted Steel 

Obviously silicone is difficult to remove from grit blasted steel after a few days of contact. The mechanism 

by which the silicone is retained on the surface is not really defined. 
Target, mg/sqft 

1 

Level Determined Gravimetrically, mghqft 

SGP CCP FGP GE D6AC 

1.18 1.18 1.18 1.18 1.18 

25 

20 

5 l5 

P 

i 

u 

z 10 

5 

0 

5 

10 

20 

I 

5.3 5.3 5.3 5.3 5.3 

9.9 9.9 9.9 9.9 9.9 

21.6 21.6 21.6 21.6 21.6 

1;1 ./i 

0 005 0 

inear (A 2922 can-1) 

Figure I. Calibration models for HD2 grease on grit blasted steel at two different wavelengths exhibiting linear 

correlation of absorbance \. ersus concentration. 
Figure 2. Calibration models for HD2 grease on four types of composites. Composites containing carbon 

polymorphs, carbon and graphite absorb essentially all the infrared energy and preclude valid models. 
Flash UV Models for HD2 Grease on Composites 

120 

100 

80 

f 

E 

i 

60 3 

c 

40 

20 

0 

SGP 

- - Linear (SGP) 

rn = -Linear (FGP) 

- 4ineariGE) 

10 15 

HD2 Grease Conc., mgJsqfl 

20 25 

Figure 3. Flash UV Fluorescence Imaging calibration models for HD2 grease on four types of composites exhibit 

good correlation. Composites containing carbon polymorphs, carbon and graphite absorb much of the fluorescent 

energy but still exhibit linear correlation of fluorescence versus concentration. 
Figure 4. SOC 400 infrared spectrum (Top) of steel panel after wiping with Contec wipe considered dirty with 

tluorescence over entire surface. Bottom spectruin is on the saint: panel after being extracted four times with 

chlorofoml. 

Figure 5. Calibration model, left, for silane adhesive pronioter in chloroform using Nicolet FTIR and 1 mm sealed 

cell showing very linear correlation. Calibration model. right, for silane adhesive promoter on grit blasted steel 

using SOC400 diffuse reflectance spectra. 
Physical Evaluation of Cleaning Performance - We Are Only Fooling Ourselves 

EARL PRATZ / 

Lockheed Martin Michoud Space Systems +/-, 

P.O. Box 29304, M/S 4710 

Michoud Assembly Facility 

New Orleans, LA 701 89 USA 

Phone: 504-257- 176 1 

Fax: 504-257-4438 

E-mail] Earl.H.Pratz@,maf.nasa.gov I 

Surface cleaning processes are normally evaluated using visual physical properties, such as 

streaking, staining, and water-break-fi-ee conditions. There is the assumption that these physical 

methods will evaluate all surfaces all the time for all operations. We have found that these physical 

methods are lacking in sensitivity and selectivity with regard to surface residues and subsequent 

process performance. We will report several conditions where evaluations using visual physical 

properties are lacking. We will identify possible alternative methods and future needs for surface 

evaluations. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:/lampet.msfc.nasa.gov 
Low Environmental Impact, High Performance Foam Blowing Agents Based on 

Iodofluorocarbons 

Patrick M. Dhooge, Suzanne M. Glass, and Jonathan S. Nimitz 

Environmental Technology and Education Center (ETEC) 

4500-B Hawkins St. NE 

Albuquerque, NM 87 109-45 17 

Phone: (505) 345-2707 

http://www .etec-n- I jnimitzQetec-nm.coni 

INTRODUCTION 

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), including CFC- 1 1, 

CFC- 12, HCFC- 14 1 b, and HCFC- 142b, have been used as high performance polymer foam 

blowing agents because of their physical properties, stability, relatively high molecular weight, 

and low toxicity. However, these blowing agents deplete stratospheric ozone, and have been or 

will soon be phased out of production in developed countries under the provisions of the 

Montreal Protocol and its amendments. CFC-I 1 and CFC-12 have already been phased out of 

production and replaced with HCFC- 14 1 b and HCFC- 142b. Although HCFC- 14 1 b has been 

widely used as an interim blowing agent, its production is scheduled to cease in 2003. HCFC142b production is scheduled to cease in 2010. 

In general, the blowing agent in insulating foam provides from 50% to 80% of the foam's 

insulating value. Substitute blowing agents such as hydrocarbons and CO? have low insulating 

value and diffuse out of the foam much more quickly than the CFCs and HCFCs, further 

reducing the insulating value of the foam as it ages. Hydrocarbon blowing agents introduce 

complications in manufacturing processes because they are flammable and they produce more 

flammable foam. Hydrofluorocarbon (HFC) blowing agents such as HFC-245fa, planned as the 

next standard blowing agents, have significantly higher vapor thermal conductivities than HCFC141 b or CFC-I 1. In addition, HFCs have moderate global warming potentials (GWPs). 

In the aerospace sector, where weight and volume are highly valued, there is a strong 

need for a rigid closed-cell polymer foam blowing agent that is non-ozone-depleting, 

nonflammable, relatively nontoxic, thermally stable, compatible with polymer materials, 

reasonably priced, and will produce foams with superior insulating value and superior insulation 

aging characteristics. The same is true in applications such as refrigerator and freezer insulation, 

where insulation value in a fixed size appliance is highly valued. A third high value application 

is refrigerated transport units, where weight and volume are also highly valued due to fuel use 

per weight. 

Iodofluorocarbons (IFCs) were identified by Jon Nimitz and Lance Lankford as 

potentially attractive nonflammable foam blowing agents that would address the need for high 

performance, low atmospheric impact foam blowing agents. IFCs have attractive physical 

properties (similar to CFCs), high molecular weights, and because they undergo photolysis 

within two days when released into the atmosphere they never reach the stratosphere and thus 

have negligible ozone-depletion potential (ODP) (Solomon a and Solomon b). Their short 

atmospheric lifetimes also give them very low GWPs. The high molecular weights are expected 
to make these compounds outstanding insulating gases and to reduce permeation, thus improving 

retention of insulating performance on aging. Theory and previous experimental results with 

other foam blowing agents indicate that, if properly formulated, foams blown with an IFC such 

as CFlI should have 15-20% better insulating ability than foams blown with HCFC- 141b and 

HCFC- I42b. In addition, because CF3I has a significantly greater molecular weight than HCFC141b or HCFC-I42b, it will diffuse out of the foam more slowly, giving foams blown with CFjI 

better aging characteristics. Because of their superior insulating ability, polymer foams blown 

with IFC-based agents should allow lighter weight and lower volume insulation, significantly 

improving performance in a variety of applications. 

ETEC's initial investigation of IFCs as foam blowing agents was sponsored by the U.S. 

Department of Energy's Energy-Related Inventions Program (ERIP). IFCs considered in this 

investigation included CF,I, 1 -C3F,I and 2- C3F7I. Blends of CF3I with hydrofluorocarbons 

(HFCs) and with carbon dioxide were also investigated. 

RESULTS AND DISCUSSION 

Predicted Performance 

The high molecular weights of IFCs made it appear highly probable that they would 

provide substantially better insulation than CFC- 1 1 or any of the currently available alternatives 

(CARERS, Center for Emissions Control, Chemical Marketing Reporter, DuPont, EPA, Jeffs, 

Kirk-Othmer a and b, Recktenwald, Smits, and Ullman). Reasoning for this statement follows 

immediately below. 

Heat transfer in foams is by conductive, convective, and radiative processes. For most 

insulating foam, by far the greatest contribution is from conductive heat transfer. With small cell 

size, convective processes are limited and radiative transfer at typical temperature differentials is 

small. The thermal conductivity of the foam cell gas is the major contributor to the thermal 

conductivity of the foam. 

The relative insulating value of a gas is inversely proportional to its thermal conductivity. 

The measured vapor thermal conductivity of CFJ at 10°C and 1 .O atmosphere is 6.7mW/m-K. 

CF3I has low thermal conductivity and low diffusion rate principally because of its high 

molecular weight and good infrared absorption. In general, the diffusion rate and thermal 

conductivity of gases varies with the inverse of the square root of their molecular weights. If heat 

transfer occurs entirely by conduction, the ratio of thermal conductivity for CFJ relative to 

HCFC- 142b is given by Equation [I]. 

6.7/12 = 0.558 [11 

Insulating foam can be considered to have two heat flow paths: one for the polymer 

matrix and one for the gas. If the polymer matrix does not change, that portion of the heat flow 

will not change. However, if the gas is changed, its contribution to the heat flow changes. 

Depending on the density and nature of the foam, anywhere from 50% to 80% of the insulating 

ability of rigid, closed cell polymer foam is due to the thermal conductivity of the gas in its cells 

(Glicksman). CF3I vapor is a better insulator than HCFC- 142b vapor by about 44%. The 

estimated improvements from CFJ versus CFC, HCFC, HFC, hydrocarbon, carbon dioxide, and 
blowing agents are shown in Table 1, assuming a conservative value of 50% of the insulating 

value of the foam is attributable to the blowing agent. 

HCFC- 142b 

HFC-245fa 

HFC-356mffm 

cyclopentane 

Table 1. Predicted Improvements in Insulating Abilities and Diffusion Rate for CFJ Versus Other 

Foam Blowing Agents 

insulating ability and diffusion rate, % insulating ability of foam, %a 

27 13 

27 13 

31 15 

12 

44 22 

52 26 

54 27 

36 18 

CO- 56 28 

The results in Table 1 show that replacement of HCFCs and alternative agents with CFJ 

is estimated to lead to an improvement in the insulating ability and diffusion rate of the gas of 

25% to 56%, and a conservatively estimated increase in the insulating ability of the rigid, closedcell polymer insulating foams of 12% to 28%. If the contribution of the blowing agent to the total 

foam thermal conductivity is more than 5070, the predicted insulating improvements in the right 

hand column of Table 1 will be greater. Thus, calculations show that CF3I should increase the 

insulating performance of rigid polymer foams by 10% to 30% over CFCs and other common 

blowing agents. The increased insulating value of rigid polymer foams prepared with this 

blowing agent and its blends will give it very low Total Equivalent Warming Impact (TEWI). 

Stability and Compatibility of CFJ 

Although iodinated organic compounds are in general more reactive, more toxic, and less 

stable chemically than other halogenated organic compounds, the presence of fluorine atoms 

bonded to the iodinated carbon atom provides substantial additional stability and greatly 

decreased toxicity. The presence of strongly bonded, highly electron-withdrawing fluorine 

atoms on the iodinated carbon atom greatly inhibits both common mechanisms of reaction for 

iodocarbons. Steric hindrance (physical blocking by the fluorine atoms) prevents back-side 

attack by nucleophiles (SN~ or substitution, nucleophilic, bimolecular mechanism) and the 

increased C-I bond strength inhibits unimolecular bond-breaking (SN 1 or substitution, 

nucleophilic, unimolecular mechanism). For toxicity and stability considerations, IFCs 

containing a terminal iododifluoro group (-CFzI) are preferred over other molecular 

arrangements. By having three fluorine atoms on the same carbon atom as the iodine the C-I 

bond in CF3I is further strengthened and reactions are greatly inhibited. 
Published studies on thermal decomposition of CF3I indicate that the compound is quite 

thermally stable (Nimitz a). In one study it is reported that CF3I is stable in contact with metals 

up to 443 K (170°C or 340°F). Recent work indicates that it is stable when heated to 355 K 

(82°C or 180°F) for at least 60 days (Dierdorf). 

In testing by Dr. N. Dean Smith at EPA’s Risk Management Laboratory and by 

Spauschus and Associates, CFJ blends have been shown to have good thermal stability and good 

compatibility with common materials of construction (Smith and Spauschus). In testing by Dr. 

Smith’s group, a blend containing CFJ was sealed in evacuated vials containing Vespel‘, BunaN” silicone rubber, Teflon’” Viton‘, stainless steel, aluminum, brass, or bronze, in the presence 

and absence of POE oil, and aged for two weeks at 448 K (175°C). Only Bum-N‘ was found to 

be unacceptable, having 1 1 % swelling and becoming approximately 23% harder. The blend 

showed no significant degradation (10.05%) by itself or in the presence of any of the materials. 

From decomposition rate studies performed by Spauschus and Associates, it has been shown that 

CFJ would undergo less than 0.1 % decomposition in twenty years under typical ambient 

temperature conditions. 

Flammability 

CFJ is an outstanding fire extinguishant, comparable in effectiveness to Halon 1301. 

CF3I has been shown to prevent combustion of hydrocarbon fuels when present at about 3% 

concentration by volume in air (Nimitz b). Thus, it will not contribute to the flammability of 

foams. In a fire environment, the cells in most foams rupture long before the polymer starts to 

burn. This rupture is caused by softening of the polymer and thermally induced pressure. The gas 

in the cell is released and carried away. Polyurethane polymer matrixes are often highly 

flammable (although flame retardants can be added to decrease this flammability); 

polyisocyanurates are more flame-resistant. Although CF3I is not expected to make otherwise 

flammable foams nonflammable. the blowing agent will not contribute to foam flammability. 

Atmospheric Lifetime, ODP, and GWP of CF3I 

CF3I has negligible ODP because it undergoes photolysis within about two days when 

exposed to solar ultraviolet radiation in the atmosphere, and thus never reaches the stratosphere 

(Ikon). This short atmospheric lifetime also gives CF31 very low GWP. Dr. Don Wuebbles of the 

Department of Atmospheric Sciences at the University of Illinois (Urbana-Champaign), one of 

the world’s foremost experts on ODP and GWP, has concluded that the ODPs of IFCs such as 

CF3I are less than or equal to 0.0025, “much less than is of concern within the U.S. and 

international guidelines.” The GWP of CF31 is also extremely small, less than 2 relative to COZ 

for a 100 year time horizon. Dr. Wuebbles concluded that “these results imply essentially a 

negligible effect on future climate” from IFCs (Wuebbles, et al.). 

Blends 

Blends of conventional agents with IFCs can provide the advantages of lower cost and 

customized performance. Very little solubility data have been reported in the literature on IFCs. 

Because of their chemical structures, however, they were expected to have similar solubility 

characteristics to CFCs. In other projects, we have found that IFCs can be blended with a wide 

variety of common chemicals from the classes of hydrocarbons and HFCs. 
In published work on the solvent cleaning agent abilities of IFCs, the IFCs tested (C&I 

and C813I) were found to be miscible in all proportions with all other common solvents tested, 

including isopropyl alcohol, ethanol, ethyl acetate, acetone, methyl ethyl ketone, hexanes, 

toluene, naphtha, and limonene (Nimitz c). In general, addition of 30% to 50% of the IFC by 

volume was found to render blends nonflammable when an open flame was touched to the 

surface. These results encouraged us that CFd would be miscible with other foam blowing 

agents and could serve to inert flammable agents. 

Azeotropic blends are particularly attractive because they do not change composition on 

evaporation. Thus, an azeotropic or near-azeotropic foam blowing agent would not tend to lose 

the more volatile component if exposed to air. In the work reported here, we used two 

nonflammable near-azeotropic blends containing CF3I to produce polyurethane foams. These 

blends were Ikon* A and Ikon@ B, which we had previously developed as refrigerants. Ikon@ A 

is a blend of CF3I and HFC- 152a, while Ikon@ B contains these two components plus HFC- 134a. 

Toxicity of CF31 

There has been a significant amount of misunderstanding regarding the characteristics of 

CF-J. The main concerns regarding this compound have been its toxicity, stability, and 

compatibility . 

Recent results of CFJ toxicity studies at Wright-Patterson Air Force Base show that CF3I 

has very low acute toxicity (Jepson). Mice exposed continuously to 6% CF3I for 3 days showed 

no lethalities. The lethal concentration by inhalation for 50% of a mouse population in 15 

minutes (mouse 15-minute LCso) has been measured at 27.4%. These are reassuringly high 

values, indicating very low acute toxicity. Additional older toxicity information on CFzI has been 

reviewed (Nimitz a and Skaggs). Dodd and Vinegar have recently presented a review of CFzI 

toxicity in comparison to common firefighting agents (Dodd). Their conclusion was that CFJs 

toxicity data profile fits within the range of toxicity data profiles of currently used fire 

extinguishants, to which personnel are exposed routinely. 

The one major toxicological disadvantage of CFJ is its relatively low threshold cardiac 

sensitization level. Many gaseous hydrocarbons and halocarbons sensitize animal hearts to 

adrenalin. The possibility of death from heart fibrillation after exposure to a halocarbon was first 

realized in the 1960s. A standard test was developed at that time to measure the relative cardiac 

sensitization of compounds. The test uses Beagle dogs that are injected with enough 

ephinephrine (adrenalin) to be barely under the amount that would cause that dogs' heart to go 

into fibrillation (this dosage is determined for each individual dog in the test group). After 

injection, the dogs are exposed to concentrations of the test compound in air. The minimum 

amount of the compound found to induce heart irregularities is the LOAEL, or Lowest 

Observable Affect (sic) Exposure Limit. The NOAEL, or No Observable Affect (sic) Exposure 

Limit, is the maximum concentration the dog can be exposed to with no affect. This test is quite 

rigorous, since the dogs are already just below the point of fibrillation due to the very high 

ephinephrine level, and the test was not originally intended to established exposure limits. It has 

been estimated that the ephinephrine levels used in this test may be 100 times or more higher 

than would be seen in a very frightened test subject (Vinegar). It is worthwhile to note that no 

cardiac problems have been seen in normally stressed animals and humans exposed to high 

concentrations of CF,I, as evidenced by the high concentrations tolerated by rats in the acute 
inhalation toxicity tests. The cardiac sensitization test’s relevance is being questioned, but it 

remains the standard at this time. CF3I’s cardiac sensitization NOAEL is 0.2% by volume, or 

2,000 ppmv in air (Kenny, et al.). With appropriate precautions, personnel will never be exposed 

to a CFJ concentration this high. 

After a review of all available toxicity data on CF3I by toxicologists at Environ and Dr. 

Reva Rubenstein of the U.S. EPA Significant New Alternatives Policy (SNAP) program office, a 

recommended 8-hour time-weighted average exposure level for CFJ was established at 150 ppm 

(Ikon). This value is higher than the value for many common industrial chemicals, including R1 23, and the solvents methylene chloride, trichloroethylene, and perchloroethylene, indicating 

that CFJ is in general safer than these materials. The recommended short-term exposure limit 

(STEL) for CF3I is 2000 ppm. 

Synthesis, Price, and Availability of CF3I 

CFjI is in pilot scale production and is a commercial product, sold in relatively small 

amounts as a total flooding fire suppression agent for normally unoccupied areas. Current 

production is capable of supplying 50,000 kg/yr of CFJ. The price has decreased significantly 

over the last six years, but is still much higher than it will eventually be in bulk production. The 

current best price for CF3I is about $50kg. Tosoh (F-Tech), a Japanese company, has announced 

a new continuous process that should be able to produce CF3I from catalytic gas-phase iodination 

of trifluoromethane at an estimated cost of $29/kg assuming the current high iodine price of 

about $22/kg. If iodine price drops back to near its historic level of about $1 Ikg and economics 

of scale decrease overhead and trifluoromethane costs, the estimated cost of CF7I produced by 

the Tosoh process should be about $12/kg. 

The available data indicate that iodine supply for producing CF3I and other IFCs as 

replacements for CFCs, HCFCs, and halons will not be a problem. Present world production of 

iodine is approximately 15 million kg per year. Currently, iodine prices are near a modern all 

time high due to China’s decision several years ago to iodize their table salt. This decision 

caught iodine producers by surprise and raised iodine prices. New iodine production facilities are 

being built. Iodine price should return closer to its historic level of about $1 Ikg. Proven 

worldwide reserves of iodine recoverable at less than $15/kg are about 6.4 billion kg (Bureau of 

Mines). If the need for iodine increases, it is almost certain that more reserves will be proven. In 

addition, the oceans contain an estimated 34 billion kg of iodine, part of which can be recovered 

directly during extraction of chlorine, bromine, or magnesium from seawater, or indirectly by 

collecting and processing kelp. Seaweeds of the Laminaria family accumulate up to 0.45% 

iodine on a dry weight basis; before 1959 seaweed was a major source of iodine. At least one 

company in China is now producing iodine extracted from seaweed at a quoted price of 

$23.50/kg. The price of iodine recovered from seaweed should decrease as production volume 

increases. Cultivation and harvesting of seaweed for iodine and food products such as alginates 

can create an alternative source of income for coastal peoples, reducing economic pressure to 

over-fish and providing marine habitat. 

Test Foam Results 

Polyurethane and polystyrene foams were prepared with CF31 and blends containing 

CF3I. The foam formulations were not optimized for the CF3I blowing agents, and the 
polyurethane foams in particular had large voids indicating insufficient solubility of the CF3Ibased blowing agents in the polymer formulation components. The limited solubility also made 

the foams denser that desired. The data that could be acquired from the foam samples was 

therefore limited, but what results were obtained were encouraging. 

Property R-12 Blowing Agent 

Table 2 gives a comparison of thermal conductivity of polyurethane foam samples as 

prepared and after 30 day aging by ASTM C-5 18. Although the R- 12 blowing agent formed a 

foam with better cell structure (no voids), and thus better insulating value, the foam blown with 

CFJ is losing almost no insulating value on aging, and has significantly better dimensional 

stability. The slower loss of insulating value for the foam blown with CF3I would be expected 

from its lower diffusion rate and thus slower loss from the foam cells. A11 foams blown with 

CF3I in these studies had the excellent aging properties shown here. 

CFJI Blowing Agent 

Table 2. Properties of Polyurethane Test Foams Blown with R-12 and CFd 

Approximate blowing agent 

concentration by weight % 

Densitv. ocf 

20 20 

2.97 2.79 

Dim. Stability, % change 

@ 158 oF/97% RH 

Lenpth 3.01 2.17 

Width 

Thickness 

2.73 1.90 

-1.13 -0.95 

Trial production runs of extruded polystyrene (XPS) foam blown with CF3I/COz mixtures 

were prepared at Owens-Corning. The trial foams were compared to the same polystyrene 

formulation blown with HCFC-142b. Table 3 shows selected results from these foams. The same 

problem was encountered with this polymer formulation as with the polyurethane formulation in 

that it was not optimized for the CF31 blowing agent, which is reflected by the significantly 

greater densities for the foams blown with the CFJ blends. The foams blown with CFJ blends 

are more fire-resistant as demonstrated by their higher oxygen index numbers, and their 

strengths, when adjusted for density, were the same as for the HCFC-blown foams. 

K-factor, mW/m-K 

As received 

+ 30 davs 

Normalized for density, the thermal conductivities of the XPS foams blown with the 

different agents were all identical within experimental error. Thermal conductivity was linearly 

dependent on foam density to 99.5% confidence level. These results imply that there was no 

effect from the blowing agent gas, which is counter to the known thermal conductivity of CF3I 

and previous theory and experiment with other foam blowing agents. The reasoning for why the 

XPS foams blown with CF3I should have had lower thermal conductivity is as follows. The 

relative density of insulating foam reflects the fraction volume occupied by the polymer. For 

example, bulk polystyrene has a density of about 1050 kg/m'. The polystyrene in foams prepared 

for this project had densities of about 30 to 40 kg/m'. The fraction of polymer is therefore about 

23.2 41.0 

26.1 41 .O 
0.03 to 0.04. Taking a midrange value of 0.035 multiplied by the thermal conductivity of 

polystyrene (150 mW/m-K) times the efficiency gives the contribution to thermal conductivity of 

Property Foam blown with Foam blown with 11 

wt% CFJ and 1 wt% 

coz 

Cell diameter, mm 0.25 0.3 I 

k-factor normalized 

to HCFC- l42b foam 28.8 29.7 

density, mW/m-K 

Compressive 

Strength, kPa 

HCFC-142b 

Density , kg/m3 29 37.7 

276 not measured 

Oxygen Index, % 24 35 

the polymer. 

0.035 x 150 x 0.67 = 3.5 mW/m-K 

Foam blown with 5 

wt% CF3I and 4 wt% 

coz 

42 

0.19 

28.8 

638 

31 

[41 

Compared to the measured thermal conductivities of the foams, this contribution is about 

12% of the total thermal conductivity. Some contribution to thermal conductivity is due to 

radiative transfer, and it is estimated that about 60% of the thermal conductivity of these foams is 

expected to be determined by the thermal conductivity of the cell gas. Thus, there should have 

been a measurable decrease in thermal conductivity of the foam blown with 11 wt% CF3V1 wt% 

CO,, when corrected for density. 

CONCLUSIONS 

CFJ and its blends appear to be excellent replacements for the CFC and HCFC insulating 

foam blowing agents. However, at least two major developmental tasks remain to be 

accomplished. 

First, formulations for preparing polyurethane and polystyrene insulating foams need to 

be optimized for use with CF3I blends. This will require solubility studies to identify polymerforming components that dissolve significant amounts of CF3I. 

Second, foams need to be prepared with candidate optimized formulations and foam 

properties including density, cell size, strength, thermal conductivity, and aging characteristics 

thoroughly determined. Optimized formulations will be identified for application. 

ACKNOWLEDGEMENTS 

The funding for the work described in this paper was provided by the U.S. Department of 

Energy’s Energy-Related Inventions Program. We would like to thank David Crouch of DOE, 

our Invention Coordinator, for his valuable technical support during the effort. ETEC would also 

like to thank Owens Corning, and particularly Ms. Barbara Fabian, for her support in preparing 

the test runs of foams and the properties testing provided. 
REFERENCES 

Bureau of Mines, Mineral Commodity Summaries 1993, U.S. Department of the Interior, 

Washington, DC, 1993, pp. 86-87. 

CARERS (Conservation and Renewable Energy Inquiry and Referral Service), “Foam 

Insulation,” Merrifield, VA, 1994. 

Center for Emissions Control, Flexible Polyurethane Foam Manufacture: An Assessment of 

Emission Control Options, October 1991, 1225 19th St. NW, Suite 300, Washington, DC, 

Chemical Marketing Reporter, “New Urethane Foams,” Nov. 19, 1990, p. 7. 

Dierdorf, D., New Mexico Engineering Research Institute, Albuquerque, NM, personal 

communication to Dr. Jon Nimitz, ETEC, Albuquerque, NM. 

Dodd, D. E. and Vinegar, A., “Toxicity Data Comparison of CF3I with Currently Used FireExtinguishing Agents and Refrigerants of Interest to the Military,” Proceedings of the Halon 

Options Technical Working Conference, Albuquerque, New Mexico, April, 1999, available from 

New Mexico Engineering Research Institute, The University of New Mexico, Albuquerque, New 

Mexico. 

Du Pont de Nemours, E. I., and Company, ”Properties of Rigid Urethane Foams,” Publication 

BA13, 1984. 

Environmental Protection Agency, Handbook for Reducing and Eliminating 

Chlorofluorocarbons in Flexible Polyurethane Foams, Report 2 1 A-4002, April 199 1. 

Glicksman, L. R., “Heat Transfer in Foams,” in Low Density Cellular Plastics: Physical Basis of 

Behavior (Chapter 5), Edited by Hilyard, N. C. and Cunningham, A., Chapman and Hall, 

London, 1994. 

Ikon Corporation, “Significant New Alternatives Policy (SNAP) Program Submission to the U.S. 

Environmental Protection Agency on Ikon B Refrigerant,” April 1998. 

Jeffs, M. “Phasing out CFCs in Polyurethane Rigid Foams - Technology Transfer” IC1 

Polyurethanes, Luxembourg, Belgium, 1993. 

Jepson, G., Wright-Patterson AFB, OH, personal communication to Dr. Jon Nimitz, ETEC, 

Albuquerque, NM, 1994. 

Kenny, T. J., Shepherd, C. K., and Hardy, C. J., “Iodotrifluoromethane and 

Iodoheptafluoropropane Assessment of Cardiac Sensitization Potential in Dogs,” report AL/OETR- 1995-003 1 published by Occupational and Environmental Health Directorate, Toxicology 

Division, Wright-Patterson AFB, OH, 1995. 

Kirk-Othmer Encyclopedia of Chemical Technology. The, “Insulation, Thermal,” Vol. 13, 

Wiley, 199 1, pp. 59 1-605. 

Kirk-Othmer Encyclopedia of Chemical Technology, The, ”Foamed Plastics,” Vol. 1 I, pp. 82- 

123, Wiley, 1991. 

Nimitz a: Nimitz, J. S., “High-Performance, Environmentally Sound Replacements for Halon 

1301,”Prepared by ETEC for McClellan AFB under contract FO4699-93-C-0004, December 

1993. 

Nimitz b: Nimitz, J. S., Glass, S. M., and Dhooge, P. M., “Gas Phase Combustion Suppression of 

Various Fuels by CFJ,” Proceedings of the 1999 Halon Options Technical Working Conference, 

Albuquerque, New Mexico, April 27-29, 1999, The University of New Mexico, New Mexico 

Engineering Research Institute, Albuquerque, NM, USA. 

20036-24 1 I. 
Nimitz c: Nimitz, J. S., Development of Nonflammable, Environmentally Compliant 

Fluoroiodocarbon Solvents: Phase I Final Report, Prepared for U.S.A.F. Wright Laboratories 

under contract F33615-94-C-5003, ETEC 95- 1, January 1995. 

Recktenwald, G. W., and Andrews, W. R., “Rigid Urethane Foams” in Bruins, P. F., ed., 

Polyurethane Technology, Interscience, New York, 1969, pp. 67-93. 

Skaggs, S. R., Dierdorf, D. S., and Tapscott, R. E., “Update on Iodides as Fire Extinguishing 

Agents,” Proceedings of the I993 CFC and Halon Alternatives Conference, Washington, DC, 

October 20-22, 1993, pp. 800-809. 

Smith, N. D., “Materials Compatibility with Ikon-B: Final Report,” prepared for the 

Environmental Technology and Education Center by the National Risk Management Laboratory, 

U. S. EPA, Research Triangle Park, NC, September 1997. 

Smits. G. F. and Thoen, J. A. “Mathematical Modeling Techniques to Predict Important Aspects 

of k-Factor Aging of CFC- 1 1 Free Rigid Insulation,” Journal of Cellular Plastics, Vol. 29, Jan 

Spauschus and Associates, “Results of CF3I Stability and Compatibility Tests,” confidential 

report prepared for Ikon Corporation. 

Ullman’s Encyclopedia of Industrial Chemistry, ”Foamed Plastics,” Vol. A 1 1, Verlag, 1984, pp. 

Vinegar, A. and Jepson, G. W., “Epinephrine Challenge for Cardiac Sensitization Testing vs. 

Endogenous Epinephrine: A Perspective,” Proceedings of the Halon Options Technical Working 

Conference, Albuquerque, New Mexico, April, 1999, available from New Mexico Engineering 

Research Institute, The University of New Mexico, Albuquerque, New Mexico. 

Wuebbles, D. J., Li, Z., and Patten, K. O., “Estimated Ozone Depletion Potentials and Global 

Warming Potentials for l-C3FTI, 1 -C&I, and 1-C6F13I1’’ 1996 report included as an appendix in 

EPA Significant New Alternatives Policy (SNAP) Program submission for Ikon €3 refrigerant, 

1998. 

1993, p. 57. 

435-463. 
Update: HFC 245fa Blown Foam Development with External Tank Spray Foams 

SIMON DAVIS 

Lockheed Martin Manned Space Systems 

Marshall Space Flight Center/Bldg. 4739 

Huntsville, AL 358 12 USA 

Phone: 256-544-6482 

n.Davis@msfc.nasa.gov 

The MSFC Thermal Protection Systems (TPS) Materials Research Laboratory is currently 

investigating environmentally friendly blowing agents for use in the insulations of the Space 

Shuttle's External Tank. The original TPS foam materials of the External Tank were blown with 

chlorofluorocarbon 1 1, which is now regulated because of its high Ozone Depletion Potential (ODP). 

Hydrochlorofluorocarbons (HCFCs), with an ODP that is one tenth that of CFCs, have been widely 

adopted as an interim blowing agent in urethane insulations. In FY96, Lockheed Martin completed 

the production qualification and validation of HCFC 141 b blown insulations. Because of the expected limited commercial lifetime of HCFC 141 b, research efforts are underway to identify and 

develop alternatives with zero ODP. HFC 24Sfa ( 1.1,1,3,3 pentaflouropropane) has been chosen by 

the manufacturer as a third-generation blowing agent to be marketed commercially. Preliminary 

work evaluating this third-generation candidate has demonstrated promising material mechanical 

property data. Favorable results from small-scale spray activities have justified evaluations using 

production foam processing spray parameters. With the scale-up of the spray equipment, however, 

additional processing issues have been identified. This paper will present data collected to date 

regarding the use of this blowing agent in External Tank spray foams. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfc. nasa. gov 
High-Performance, Low Environmental Impact Refrigerants 

Edward T. McCullough, Patrick M. Dhooge, Suzanne M. Glass, and Jonathan S. Nimitz 

Environmental Technology and Education Center (ETEC) 

4500-B Hawkins St. NE 

Albuquerque, NM 87 109-45 17 

Phone: (505) 345-2707 

www.etec-nm.com I pdhoogeOetec-nm.com 1 

INTRODUCTION 

Refrigerants used in process and facilities systems in the U.S. include R-12, R-22, R-123, 

R- 1 34a, R-404A, R-4 1 OA, R-500, and R-502. All but R- 134a, R-404A, and R-4 1 OA contain 

ozone-depleting substances that will be phased out under the Montreal Protocol. Some of the 

substitutes do not perform as well as the refrigerants they are replacing, require new equipment, 

and have relatively high global warming potentials (GWPs). New refrigerants are needed that 

addresses environmental, safety, and performance issues simultaneously. 

In efforts sponsored by Ikon Corporation, NASA Kennedy Space Center (KSC), and the 

U.S. Environmental Protection Agency (EPA), ETEC has developed and tested a new class of 

refrigerants, the Ikon refrigerants, based on iodofluorocarbons (IFCs). These refrigerants are 

nonflammable, have essentially zero ozone-depletion potential (ODP), low GWP, high 

performance (energy efficiency and capacity), and can be dropped into much existing equipment. 

Current Refrigerants 

Although its production is now banned in the U.S. and other developed countries, R- 12 is 

still used extensively. It was estimated by the American Refrigeration Institute (ARI) that at the 

end of 1999 approximately 50% of the R-12 equipment in the U.S. had not yet been converted to 

newer equipment or the R- 12 replaced. R-500 is a blend of R-12 and R-152a. 

R- 134a, an HFC, will not be phased out under the Montreal Protocol. R-134a has replaced 

R-12 in many applications. As a low cost refrigerant it is cost effective for some applications, but it 

requires new or modified equipment. Carrier manufactures R- 134a water chillers, and U.S. 

producers of residential refrigerators and automobile air conditioners now use R- 134a. However, 

the performance of R- 134a cooling systems tends to degrade at high ambient temperatures because 

of R- 134a's relatively rapid decrease in cooling capacity at higher temperatures. International 

concern about greenhouse gases may limit R- I34a applications in the future. 

R- 123 use in water chillers is increasing despite the fact that it is an HCFC and subject to 

phaseout as a Category 2 ozone-depleting substance under the Montreal Protocol. Trane is 

converting many existing R- 12 systems to R- 123, and manufacturing new R- 123 systems. The 

attraction of R- 123 is its inherent energy efficiency. R- 123 water chillers are the most energyefficient on the market. However, R- 123 is relatively toxic, with a permissible exposure limit of 

only 50 ppmv in air, which means that air monitors must be installed around R- 123 equipment 

and liability risk is increased. It also means that R- I23 has only limited application and cannot be 

used in smaller commercial and residential systems. 
R-22 has been used extensively in systems where rapid cooling is needed, including 

almost all window air conditioners, central air conditioners, and ice-making machines. R-22 is 

also used in many water chilling and process cooling systems. R-502, a blend of R-22 and R-I15 

with slightly higher capacity than R-22, has been used in many supermarket refrigerated display 

case systems. It has been difficult to find good replacements for R-22 and R-502 because of their 

high capacity combined with reasonably good energy efficiency. Many new R-22 systems are 

still being installed. However, because of continuing concerns over ozone depletion, R-22 

phaseout has been accelerated and may be accelerated again. Phaseout of R-22 in the U.S. will 

begin with a 35% reduction in production starting in 2003, and then a 65% reduction in 

production starting in 2006. The price of R-22 is likely to increase significantly when its 

phaseout begins, similar to R-12 when it was phased out of production. 

R-404A, R-407C, and R-41 OA, replacements for R-22, are inherently less energy efficient 

than R-22 according to the National Institutes of Standards and Technology (N1ST)’s Refprop@ 

refrigerant properties program. R-404A and R-4 10A have higher operating pressures than R-22 

and require new equipment. R-407C has a high temperature glide in the evaporator and is not 

suitable to replace R-22 in many applications. Like R- 134a, these refrigerants are not miscible with 

mineral oil and require polyol ester (POE) oil or some other synthetic lubricant in the compressor. 

It is important to note that new refrigeration and cooling equipment is considerably more 

energy efficient than older equipment because of improvements in design and in the efficiencies 

of motors and compressors, not because new refrigerants are more energy-efficient (with the 

notable exception of R-123). In addition, in some applications additional energy efficiency gains 

have been obtained in new systems using ice making, liquid refrigerant pressurization, 

groundwater heat exchange, and other engineering advances. While these engineering advances 

are all of significant value, they do not reflect the inherent energy efficiency of the refrigerant, 

which is determined by its thermodynamic properties. A more energy-efficient refrigerant will 

add to the gains achieved through engineering changes. 

It has been stated that replacing an old refrigerated cooling unit with a new unit is a “nobrainer” because the improvement in energy efficiency will repay the cost of the new unit in 

three years or less. This is not true for many units, however, and not every facility has the 

investment capital, desire, or time to replace entire units and systems. An alternative solution that 

can be much more cost-effective is to use more energy-efficient refrigerants in these units and 

perhaps install new, more energy-efficient compressors. 

Ikon@ A 

trifluoroiodomethane (CF3I), was the first of the new refrigerants developed, and was originally 

developed as a near-drop-in replacement for R-12. Ikon‘ A is fully miscible with mineral oil and 

so can be used directly in R-12 and R-500 systems. It can also replace R-134a. Ikon@ A’s 

evaporator temperature glide in air conditioning and refrigeration applications is about 0.10 - 

0.15 K, which makes it highly suitable for critically flooded evaporators. Ikon’ A also has a very 

low global warming potential (GWP) of about 30 versus CO2 = 1 for a 100 year horizon. EPA 

has tested Ikon” A in automotive air conditioners with good results (Jetter). Dole Fresh Fruit ran 

Ikon“ A (previously called Ikon@’- 12), a near-azeotropic blend of R- 152a and 
Ikon‘-” A in an R- 12 refrigerated transport (a “reefer”) for two years with no indications of 

incompatibility or refrigerant decomposition. Although Ikon“ A has superior cooling capacity 

and energy efficiency versus R- 12 and R- 134a, it was soon realized that automobile 

manufacturers were too heavily committed to R- 134a. In addition, the added energy efficiency of 

Ikon”’ A would be reflected in at most a few tenths of a mile per gallon average fuel efficiency 

increase, which most motorists would not notice or value. Finally, the relatively high average 

leak rates for automotive air conditioning systems make an inexpensive refrigerant such as R134a more desirable for these systems. 

Further applications analysis indicated that Ikon‘ A might have a good application as an 

energy-efficient refrigerant in residential refrigerators and freezers, as these devices have high 

energy use per weight of refrigerant and very low leak rates. In a subsequent effort sponsored by 

EPA, ETEC measured Ikon‘ A’s performance versus R- 134a in an instrumented R- 134a 

domestic refrigerator and had Ikon@ A’s thermodynamic properties measured. Ikon‘ A has been 

approved for a variety of cooling applications under the U.S. Environmental Protection Agency’s 

Significant New Alternatives Policy (SNAP) program. 

Ikon@ B 

refrigerants in their facility equipment to minimize operational and life cycle costs. Ikon$ B, the 

second of the IFC-based refrigerants, was developed in the initial effort with assistance from N. 

Dean Smith at EPA’s Risk Management Laboratory. Ikon‘ B is a near-azeotropic blend 

containing R-152a, R-l34a, and CF3I. IkonE B is also highly suitable for systems with critically 

flooded evaporators, with an evaporator temperature glide of about 0.15 - 0.2 K in air 

conditioning and refrigeration applications. It has slightly better performance and lower cost than 

Ikon‘F A at the expense of a somewhat higher GWP and the need for POE compressor lubricating 

oil. Ikon@ B is suitable for replacing R-12, R-134a, and R-500 in a variety of applications 

including water chillers, process coolers, air conditioners, refrigerators, and freezers. Performance 

tests of Ikon“ B versus R-12 and R-134a were conducted in ETEC’s instrumented I .75 ton water 

chiller test bed and in an instrumented 20 ton air conditioner at NASA KSC. In addition, Ikon’? 

B’s performance has been measured versus R-22 in the Vapor Compression Test Loop (a type of 

compressor calorimeter) at Oak Ridge National Laboratories, its performance was measured 

versus R-134a in an instrumented R-134a domestic refrigerator at ETEC, and it has been used in a 

Dole Foods R- 134a reefer for over two years. Ikon‘ B’s thermodynamic properties have been 

measured. IkonL‘ B has been approved for a variety of cooling applications under the U.S. 

Environmental Protection Agency’s Significant New Alternatives Policy (SNAP) program. 

NASA KSC’s interest in the IFC-based refrigerants is for replacement of ozone-depleting 

Ikon@ C 

the effort for NASA KSC, ETEC developed Ikon‘ C as an energy-efficient R-22 and R-502 

replacement. Ikon“ C is a proprietary, near-azeotropic blend containing CF3I. Ikon‘ C’s 

operating pressures are almost an exact match for R-22. Ikon” C’s performance has been 

measured versus R-22 in ETEC’s instrumented 1.75 ton water chiller test bed. Ikon@ C is 

significantly less expensive than IkonQ B. Ikoncc C’s thermodynamic properties have been 

measured, and a SNAP application has been prepared. 

NASA KSC was also interested in a zero ODP, energy-efficient replacement for R-22. In 
RESULTS AND DISCUSSION 

Toxicity of CF31 

CF31. The main concerns regarding this compound have been its toxicity, stability, and 

compatibility. 

There has been a significant amount of misunderstanding regarding the characteristics of 

Recent results of CF3I toxicity studies at Wright-Patterson Air Force Base show that CF3I 

has very low acute toxicity (Jepson). Mice exposed continuously to 6% CF3I for 3 days showed 

no lethalities. The lethal concentration by inhalation for 50% of a mouse population in 15 

minutes (mouse 15-minute LCso) has been measured at 27.4%. These are reassuringly high 

values, indicating very low acute toxicity. Additional older toxicity information on CF3I has been 

reviewed (Nimitz; Skaggs, et a).). Dodd and Vinegar have recently presented a review of CF3I 

toxicity in comparison to common firefighting agents (Dodd and Vinegar). Their conclusion was 

that CF3I’s toxicity data profile fits within the range of toxicity data profiles of currently used 

fire extinguishants, to which personnel are exposed routinely. 

The one major toxicological disadvantage of CF3I is its relatively low threshold cardiac 

sensitization level. Many gaseous hydrocarbons and halocarbons sensitize animal hearts to 

adrenalin. The possibility of death from heart fibrillation after exposure to a halocarbon was first 

realized in the 1960s. A standard test was developed at that time to measure the relative cardiac 

sensitization of compounds. The test uses Beagle dogs that are injected with enough 

ephinephrine (adrenalin) to be barely under the amount that would cause that dogs’ heart to go 

into fibrillation (this dosage is determined for each individual dog in the test group). After 

injection, the dogs are exposed to concentrations of the test compound in air. The minimum 

amount of the compound found to induce heart irregularities is the LOAEL, or Lowest 

Observable Affect Exposure Limit. The NOAEL, or No Observable Affect Exposure Limit, is 

the maximum concentration the dog can be exposed to with no affect. This test is quite rigorous, 

since the dogs are already just below the point of fibrillation due to the very high ephinephrine 

level, and the test was not originally intended to established exposure limits. It has been 

estimated that the ephinephrine levels used in this test may be 100 times or more higher than 

would be seen in a very frightened test subject (Vinegar and Jepson). It is worthwhile to note that 

no cardiac problems have been seen in normally stressed animals and humans exposed to high 

concentrations of CF31, as evidenced by the high concentrations tolerated by rats in the acute 

inhalation toxicity tests. The cardiac sensitization test’s relevance is being questioned, but it 

remains the standard at this time. CFJS cardiac sensitization NOAEL is 0.2% by volume, or 

2000 ppmv in air. With appropriate precautions, operations personnel will never be exposed to a 

CF3I concentration this high. 

After a review of all available toxicity data on CFJ by toxicologists at Environ and Dr. 

Reva Rubenstein of the U.S. EPA Significant New Alternatives Policy (SNAP) program office, a 

recommended 8-hour time-weighted average exposure level for CF3I was established at 150 ppm 

(Ikon). This value is higher than the value for many common industrial chemicals, including R123, and the solvents methylene chloride, trichloroethylene, and perchloroethylene, indicating 

that CF3I is in general safer than these materials. The recommended short-term exposure limit 

(STEL) for CF3I is 2000 ppm. 
Stability and Compatibility of CF31 

stable chemically than other halogenated organic compounds, the presence of fluorine atoms 

bonded to the iodinated carbon atom provides substantial additional stability and greatly 

decreased toxicity. The presence of strongly bonded, highly electron-withdrawing fluorine 

atoms on the iodinated carbon atom greatly inhibits both common mechanisms of reaction for 

iodocarbons. Steric hindrance (physical blocking by the fluorine atoms) prevents back-side 

attack by nucleophiles (SN~ or substitution, nucleophilic, bimolecular mechanism) and the 

increased C-I bond strength inhibits unimolecular bond-breaking (SN 1 or substitution, 

nucleophilic, unimolecular mechanism). For toxicity and stability considerations, IFCs 

containing a terminal iododifluoro group (-CFzI) are preferred over other molecular 

arrangements. By having three fluorine atoms on the same carbon atom as the iodine the C-I 

bond in CFJ is further strengthened and reactions are greatly inhibited. 

Although iodinated organic compounds are irz general more reactive, more toxic, and less 

Published studies on themial decomposition of CF3I indicate that the compound is quite 

thermally stable (Nimitz). In one study it is reported that CF3I is stable in contact with metals up 

to 443 K ( 170°C or 340°F). Recent work indicates that it is stable when heated to 355 K (82°C or 

180°F) for at least 60 days (Dierdorf). An additional indication of stability is that many IFCs can 

be purchased from vendors and stored without unusual precautions such as refrigeration. 

In testing by Dr. N. Dean Smith at EPA’s Risk Management Laboratory and by 

Spauschus and Associates, CF3I blends have been shown to have good thermal stability and good 

compatibility with common materials of construction (Smith; Spauschus). In testing by Dr. 

Smith’s group, a refrigerant blend containing CF3I was sealed in evacuated vials containing 

itself, Vespel‘, Buna-N@’, silicone rubber, Teflon“, Won@, stainless steel, aluminum, brass, and 

bronze, in the presence and absence of POE oil, and aged for two weeks at 448 K ( 175°C). Only 

Buna-N“ was found to be unacceptable, having 1 1 % swelling and becoming approximately 23% 

harder. The refrigerant showed no significant degradation (10.05%) by itself or in the presence 

of any of the materials. The kinetics testing by Spauschus and Associates gave a decomposition 

rate for CFJ about 5 times greater than that of R- 12. However, R-12 is extremely stable. Under 

typicaI air-cooled refrigerated cooling system operating conditions, it is estimated that the 

decomposition rate of CF3I would be about 1 % in twenty years. A refrigerant blend containing 

CF3I has been used for over two years in a Dole Fresh Fruit refrigerated transport with no 

detectable decomposition. 

Atmospheric Lifetime, ODP, and GWP of CF31 

CF3I has negligible ODP because it undergoes photolysis within about two days when 

exposed to solar ultraviolet radiation in the atmosphere, and thus never reaches the stratosphere 

(Ikon). This short atmospheric lifetime also gives CF3I very low GWP. Dr. Don Wuebbles of 

the Department of Atmospheric Sciences at the University of Illinois (Urbana-Champaign), one 

of the world’s foremost experts on ODP and GWP, has concluded that the ODPs of IFCs such as 

CFJ are less than or equal to 0.0025, “much less than is of concern within the U.S. and 

international guidelines.” The GWP of CFJ is also extremely small, about 6 relative to COz for a 

100 year time horizon. Dr. Wuebbles concluded that “these results imply essentially a negligible 

effect on future climate” from IFCs. 
Synthesis, Price, and Availability of CF3I 

amounts as a total flooding fire suppression agent for normally unoccupied areas. Current 

production is capable of supplying 100,000 to 150,000 kg/yr of Ikonc“ refrigerants. CF~I’S price 

has decreased significantly over the last six years, but is still much higher than it will eventually 

be in bulk production. The current best price for CF3I is about $50/kg. Tosoh (F-Tech), a 

Japanese company, has announced a new continuous process that should be able to produce CFJ 

from catalytic gas-phase iodination of trifluoromethane at an estimated cost of $29/kg assuming 

the current high iodine price of about $22/kg. If iodine price drops back to near its historic level 

of about $1 l/kg and economics of scale decrease overhead and trifluoromethane costs, the 

estimated cost of CF3I produced by the Tosoh process should be about $1 2kg. 

CFJ is in pilot scale production and is a commercial product, sold in relatively small 

The available data indicate that iodine supply for producing CF3I and other IFCs as 

replacements for CFCs, HCFCs, and halons will not be a problem. Present world production of 

iodine is approximately 15 million kg per year. Currently, iodine prices are near a modern all 

time high due to China’s decision several years ago to iodize their table salt. This decision 

caught iodine producers by surprise and raised iodine prices. New iodine production facilities are 

being built. Iodine price should return closer to its historic level of about $I l/kg. Proven 

worldwide reserves of iodine recoverable at less than !$15/kg are about 6.4 billion kg (Bureau of 

Mines). If the need for iodine increases, it is almost certain that more reserves will be proven. In 

addition, the oceans contain an estimated 34 billion kg of iodine, part of which can be recovered 

directly during extraction of chlorine, bromine, or magnesium from seawater, or indirectly by 

collecting and processing kelp. Seaweeds of the Laminaria family accumulate up to 0.45% 

iodine on a dry weight basis; before 1959 seaweed was a major source of iodine. At least one 

company in China is now producing iodine extracted from seaweed at a quoted price of 

$23.50/kg. The price of iodine recovered from seaweed should decrease as production volume 

increases. Cultivation and harvesting of seaweed for iodine and food products such as alginates 

can create an alternative source of income for coastal peoples, reducing economic pressure to 

over-fish and providing marine habitat. 

Performance Tests and Demonstrations 

Ikon’ B vs. R- 12 and R- 134a in ETEC’s Instrumented Chiller Test Bed 

At ETEC, Ikon‘ B performance was measured versus R- 12 and R- 134a in an 

instrumented 1.75 ton (20,000 Btu/hr) air-cooled water chiller with a semi-hermetic 

reciprocating compressor. A 565 L water reservoir equipped with heaters was used as a heat 

load and thermal mass for the water chiller. Water was continuously circulated from the reservoir 

through the water chiller evaporator heat exchanger and back to the reservoir. The chiller was 

operated to keep the water reservoir at a constant temperature of about 290 K as measured by 

triplicate temperature sensors. The reservoir heaters’ amperages and voltages were measured to 

determine heat input. Refrigerant loading was adjusted to give a flooded evaporator. Multiple 

runs were conducted with each refrigerant to confirm consistency of the results and obtain a 

standard deviation. In runs with R- 134a, an R- 134a expansion device was used. R- 12 and Ikon@ 

B runs used an R-12 expansion device. Ikon‘ B gave approximately 2% higher COP and 16% 

greater volumetric cooling capacity than R- 12, and about 17% higher COP and 2% greater 

volumetric cooling capacity than R-134a in this piece of equipment. 
Ikon? B vs R- 12 in a 20 ton Air Conditioner at NASA KSC 

Ikon'" B was used to replace R- 12 in a 20 &on (240,000 Btuhr) air conditioning unit at 

NASA KSC. This unit, a backup for the unit used to provide pre-launch cooling of the Space 

Shuttle cabin, is diesel-powered with a semi-hermetic reciprocating compressor. The unit was 

instrumented and multiple runs were conducted with its standard R-12 charge and mineral oil 

lubricant to measure baseline performance. The unit was then charged with Ikon" B and POE 

lubricant. No other changes or adjustments were made. In multiple runs with Ikon' B, diesel fuel 

use was 8 - 10% less, and Ikon' B had approximately 15% greater cooling capacity versus R-12. 

Figure 1 shows why Ikon' B had greater cooling capacity. Pressure and temperature data, 

combined with the compressor displacement and thermodynamic properties for R- 12 and Ikon" 

B, allow calculation of the mass flow of each refrigerant. &on@ B's cooling capacity per pound 

is almost exactly equal to that of R- 12, but the mass flow of Ikon@ B is about 15% greater than 

R- 12's mass flow, giving Ikon" B about 15% greater volumetric cooling capacity than R- 12. 

Note that the effect increases as ambient temperature, and thus the unit's operating temperature, 

increases. In this unit, a significant fraction of Ikon' B's extra cooling capacity resulted in 

operating energy savings because although the compressor operates continuously, it is equipped 

with compressor cylinder unloader solenoids that reduce the work load on the compressor when 

capacity is in excess of that needed. The full 15% was not realized because the diesel engine also 

provides power to drive the unit's fans, and because of mechanical inefficiencies. 

75 

I A 

m Ikon B m 

80 85 90 95 

Ambient Temperature (degrees F) 

Figure 1. Refrigerant Flow Rate versus Ambient Temperature for 20 Ton AC Unit 
Ikon" B vs. R-22 in the Vapor Compression Test LOOP at ORNL 

the Vapor Compression Test Loop (VCTL) at ORNL. The VCTL is a sophisticated type of 

compressor calorimeter where the speed of the compressor can be varied to equalize cooling 

capacity. The efficiency of the compressor and compressor motor at different speeds are known 

and test results can be corrected accordingly. The conditions used were a 250 K evaporator and a 

305 K condenser. The corrected results showed that the Energy Efficiency Ratio (EER) for IkonE 

B is 20-25% higher than that of R-22 under these conditions. The capacity of Ikon" B tested 40- 

50% less than that of R-22 in this system under these operating conditions. Because R-22 is a 

refrigerant with much greater capacity but somewhat lower energy efficiency than R- 12 or RI34a. these data are in agreement with the other performance data. 

The performance of Ikon@ B versus R-22 was tested under the direction of Van Baxter in 

Ikon" A and Ikon' B vs R- I2 and R- 134a in Refrigerated TransDorts at Dole Fresh Fruit 

At Dole Fresh Fruit Ikon@ A and Ikon' B have been run in refrigerated transport units. 

Ikon@ A was run for over two years in an R-12 system. For the first six months of operation, the 

compressor oil was tested periodically for total acid number, viscosity, and content of a variety 

of metals, to determine whether any significant breakdown of the refrigerant or oil, or any 

significant corrosion, was occurring. No decomposition products were seen. Tests of the oil after 

six months showed identical results to the zero time results. No operational problems or damage 

to the compressor were seen. The test was terminated to put the units back into shipping service 

with their standard refrigerants. Ikon' B has been run in two R- 134a refrigerated transport units 

at Dole Fresh Fruit with no indication of incompatibility. 

Ikon' A and Ikon' B vs R- I34a in a Rcsidential Refrigerator 

Ikon'' A and Ikon@ B were tested versus R- 13421 in a new R- 134a residential refrigerator. 

Tests were conducted in a walk-in environmental chamber capable of maintaining the exacting 

temperature conditions specified in energy use and performance tests of residential refrigerators 

and similar equipment. Initial tests were based on the ANSVASHRAE Standard 117-1992 and 

ANSI/AHAM HRF- 1 - 1988 test methods for refrigerators. Both Ikon' A and Ikon' B showed 

about 13% greater volumetric cooling capacity than R-134a during pulldown. Energy use during 

pulldown was about 13% lower for Ikon" A and 10% lower for Ikon@ B versus R-134a. 

Residential refrigerators have cooling capacity far in excess of that used in low temperature 

maintenance (i.e., steady state operation), so the extra energy efficiency of Ikon@ A and Ikon' B 

could not be exploited in this unit during temperature maintenance because considerably more 

refrigerant is cycled than is used in cooling. 

Therefore, the Embraco EMI60HER compressor in the test refrigerator was replaced with 

the next size down, an Embraco EMISOHER. The EMISOHER has about 15% less cooling 

capacity rating (and thus about 15% less volumetric displacement) than the EMI60HER, and has 

no higher EER than the EMI60HER. Refrigerant charges were always adjusted to give a justflooded evaporator in the refrigerator. The DOE energy efficiency test at 305 K (90°F) ambient 

and the ANWAHAM pulldown test at 3 16 K (I 10°F) ambient were performed on both the 

baseline refrigerator configuration and the modified refrigerator. The baseline DOE energy 

efficiency result we obtained was 693 KWy, identical within experimental error and 

manufacturing variations to the refrigerator's official energy use rating of 69 1 KWy. The 
pulldown time using Ikon B and the EMISOHER was 6% faster than R- 134a and the EMI60HER 

(the baseline refrigerator configuration). Energy use in the DOE energy efficiency test with Ikon' 

B and the EMISOHER was 9% less than with R-134a and the EMI60HER. These results indicate 

that Ikon' B is a significant improvement over R- 134a in residential refrigerators and other 

applications. Ikon'" B is still pulling down 6% faster with a 15% smaller volumetric displacement 

compressor, indicating that its cooling capacity is about 20% greater than R- 134a under these 

conditions. If the compressor can be sized to take advantage of all of Ikon'" B's capacity, an 

energy efficiency increase of over 10% should be obtained. The estimated cost per refrigerator of 

using Ikonf3 B instead of R-134a in new refrigerators is about $6, with estimated cost savings of 

$4.15 per year at 10% efficiency increase. The estimated payback time is just over 17 months. 

Ikon" C vs. R-22 in ETEC's Instrumented Chiller Test Bed 

ETEC's instrumented water chiller (described above) was outfitted with an appropriately 

sized R-22 compressor and expansion valve. The water chiller's performance was then measured 

with R-22 and Ikon' C. Ikon' C had about 94% of the cooling capacity and 98% of the COP of 

R-22. In comparison, the COPS of R-404A and R-407C under these operating conditions, 

according to the National Institute of Standards and Technology (N1ST)'s Refprop'" program, are 

93 - 94% of R-22's. The temperature difference across the evaporator with Ikon' C was 1.1 K 

(2°F) greater than R-22, much less glide than that of R-407C. Ikon' C's operating pressures of 

68 psia on the low side and 244 psia on the high side were an excellent match to R-22's 70 psia 

and 249 psia. We believe that, with a change to POE oil, IkonE C can be a direct replacement for 

R-22 in most equipment. A change to POE oil may require a change of compressor if the existing 

R-22 compressor is not rated for POE oil, but this can be an opportunity to install one of the new, 

highly energy-efficient compressors in the system to obtain energy savings. One impressive 

aspect of Ikon' C was that the compressor outlet temperature with Ikon@' C was only 341 K 

versus 362 K for R-22. The lower compressor outlet temperature means the compressor is 

running cooler with Ikon? C, which should significantly extend compressor life. 

CONCLUSIONS 

Ikon'' A and B refrigerants have significantly greater performance than R- 12 and R- 134a. 

Their relative improvement over R-I 2 and R-I 34a increases with increasing operating 

temperatures, giving additional energy savings when most needed. It is estimated that in many 

applications their increased energy efficiency will pay back their extra cost within 1 - 3 years. 

Ikon'' A can be used to directly replace R-12 in R-12 equipment. Ikon' B can be used to 

replace R- 12 in R- 12 equipment with a change of compressor lubricating oil. For R- 12 water 

chiller retrofits with Ikon' B, a new, energy-efficient compressor can be installed and the 

evaporator and condenser thoroughly de-scaled to obtain perhaps 30% or more reduction in 

energy use. Replacing R- 134a in R- 13421 equipment with Ikon@ B should give 10- 15% reduction 

in energy use and about 15-20% additional cooling capacity in the equipment. 

Ikon' C can be a direct replacement for R-22 in R-22 equipment if the compressor can 

tolerate POE oil. In older R-22 equipment, it may be desirable to replace the compressor with a 

new, more energy-efficient one rated for use with POE oil if a change to Ikon" C is made. The 

lower compressor operating temperature with IkonF C should extend compressor life vs R-22. 
ACKNOWLEDGEMENTS 

Funding for the work described in this paper was provided by NASA Kennedy Space 

Center and the U.S. Environmental Protection Agency. We would like to thank Dr. Jacqueline 

Quinn of NASA KSC and Michael Bender of the U.S. EPA for their valuable technical support 

during the efforts. The Ikon‘ refrigerants and solvents are patented products of the Ikon 

Corporation. 

REFERENCES 

Bureau of Mines, Mineral Commodity Summaries 1993, U.S. Department of the Interior, 

Washington, DC, 1993, pp. 86-87. 

Dierdorf, Douglas, New Mexico Engineering Research Institute, Albuquerque, NM, personal 

communication to Dr. Jon Nimitz, ETEC. 

Dodd, D. E. and Vinegar, A., “Toxicity Data Comparison of CF3I with Currently Used FireExtinguishing Agents and Refrigerants of Interest to the Military,” Proceedings of the Halon 

Options Technical Working Conference, Albuquerque, New Mexico, April, 1999, available from 

New Mexico Engineering Research Institute, The University of New Mexico, Albuquerque, New 

Mexico. 

Ikon Corporation, “Significant New Alternatives Policy (SNAP) Program Submission to the U.S. 

Environmental Protection Agency on Ikon B Refrigerant,” April 1998. 

Jepson, Major (rank) Gary, Wright-Patterson AFB, OH, personal communication to Dr. Jon 

Nimitz, ETEC, Albuquerque, NM, 1994. 

Jetter, J. J., et al., “Evaluation of Ikon“’- 12 Refrigerant for Motor Vehicle Air Conditioning,” 

available in the Proceedings of the SAE International Congress and Exposition, February, 1997, 

published by SAE International, Warrendale, PA. 

Nimitz, J. S., High-Performance, - Environmentally Sound Replacements for Halon 1301, Prepared 

for McClellan AFB under contract FO4699-93-C-0004, December 1993, ETEC 93-3. 

Skaggs, S. R., Dierdorf, D. S., and Tapscott, R. E., “Update on Iodides as Fire Extinguishing 

Agents,” Proceedings of the 1993 CFC and Halon Alternatives Conference, Washington, DC, 

October 20-22, 1993, pp. 800-809. 

Vinegar, A. and Jepson, G. W., “Epinephrine Challenge for Cardiac Sensitization Testing vs. 

Endogenous Epinephrine: A Perspective,” Proceedings of the Halon Options Technical Working 

Conference, Albuquerque, New Mexico, April, 1999, available from New Mexico Engineering 

Research Institute, The University of New Mexico, Albuquerque, New Mexico. 

Smith, N. D., “Materials Compatibility with Ikon-B: Final Report,” prepared for the Environmental 

Technology and Education Center, September 8, 1997, by the National Risk Management 

Laboratory, U. S. EPA, Research Triangle Park, NC. 

Spauschus and Associates, “Results of CF3I Stability and Compatibility Tests,” confidential 

report prepared for Ikon Corporation. 
VOC Compliant Wax Removal Process 

Alan Brown, David Grimmett, Margarite Sylvia 

The Boeing Company 

Rocketdyne Propulsion & Power 

6633 Canoga Ave. 

Canoga Park, California 

Bulk wax 

removal 

Abstract 

Wax is often used as a maskant during plating operations to protect against unwanted deposits on hardware 

details. Historically, perchloroethylene was used to remove this wax at the completion of the plating operation. In 

1994. perchloroethylene was eliminated from this process at Rocketdyne, and was replaced by a high temperature oil 

and a cleaning process based on a semi-aqueous cleaner. This semi-aqueous cleaner has a volatile organic content of 

768 g/l and environmental management of this material has limited the location of the operation. It was therefore 

desirable to identify a replacement cleaner, which is not subject to these limitations and enable the process to be 

located in closer proximity to the other manufacturing areas processing the hardware. This would result in the 

eliniination of transportation of the hardware, the schedule impact of moving it. and the risk associated with 

additional handling. A cleaner was identified which satisfied these requirements and Taguchi methodology was used 

to optimize the process using this material. 

Hot oil hare1 56 Alkaline Acetic Hot DI 

-+ dewaxing -b flush -+ clean -b acid flush -b water 

Turco 6802 Vitroklene rinse 

Background 

MCC channels to serve as a maskant for plating operations or to mask off pats prior to machining operations. After 

the wax has served its purpose as a maskant, it must be removed to allow subsequent processing and to open the 

channels for cooling during engine operation. Up until the early 1990's wax removal was accomplished through use 

of perchloroethylene. In 1992- 1993, a hot oil process was developed to eliminate the use ofperchloroethylene and 

is outlined below in Figure I. 

Rigidax' is a high melting point wax which is melted and poured into a variety of components including 

Figure 1. Current Dewax process. 

The initial step of the process consists of bulk melting of most of the wax in an oven. The subsequent 

cleaning steps include immersiodflushing in a hot oil (Turco 6803)' tank. immersiodflushing in an Axarel56.' tank, 

imrnersiodflushing in a alkaline cleaner such as Vitro-klene', flushing with acetic acid and a final rinsing in a tank of 

hot DI water. 

The above process has been successfully used, but the volatile organic content (VOC) of the Axare156 is 

76s grams per liter. In order to meet more stringent emission requirements which would allow the process to be 

relocated. a VOC limit of less than 50 grams per liter must be met. Enabling the process to be relocated minimizes 

handling and eliminates shipping, significantly reducing cycle time. For this reason, laboratory and full scale process 

tests were performed to define and demonstrate a process to remove Rigidax wax from MCC liners and other 

hardware. In addition to eliminating the Axarel56, it was desirable to meet certain other goals as defined below: 

Dewaxed parts shall meet a final surface cleanliness less than 1 mg/ft' of residual hydrocarbons. 

The process should be repeatable, robust, and not operator dependent. 

The process can be used for all items requiring dewaxing. 

Argueso. M., & Co.. Inc., Mamaroneck, NY. 

Elf Atochem North America, lnc., Philadelphia. PA. 

I 

' Petroferm, Inc.. Fernandina Beach, FL. 
Process Evaluation - Laboratory Scale 

agents were reviewed and subjected to rinsability and embrittlement tests. These tests measure the ability of a 

cleaner to rinse freely from a surface and measure whether a cleaner may cause sulfur embrittlement. Based on 

successful results from these tests, the cleaners were used in several different types of processes for removing wax 

from slotted coupons. The goal was to reduce cycle time by finding a more effective cleaner, eliminating an 

immersion step or otherwise optimizing the process. The processes tested included: 

Potential cleaning agents were identified through a vendor survey and previous experience. These cleaning 

Bulk Dewax / 1 Cleaner / Steam clean 

Bulk Dewax / Turco 6802 (hot oil) / I cleaner 

Bulk Dewax / Turco 6802 (hot oil) / 1 cleaner / Vitro-klene 

Bulk Dewax / Turco 6802 (hot oil) / Steam Rinse / 1 cleaner 

The laboratory scale tests were performed with slotted coupons to simulate slotted MCC liners. Most of the 

dewaxing tests were performed using 3 x 5 inch copper coupons 0.5 inch thick containing 15 slots typical of liner 

geometry. (See Figure 2) 

tI 

I J 

1 1 

t 7 

I 1 , I 

I 

1 

I 10 

II: 

2.5 k 

0.1 inch 

t 

I I 

Figure 2. Test coupon used in most small scale testing. 

The bulk dewaxing step in this process initially melts off most of the wax, permitting fluid to flow in the 

channels, and was maintained. After the bulk dewax step was simulated, the slotted coupons were suspended with 

the slots aligned vertically in the test fluid that was contained in a glass beaker. The test fluids were preheated to the 

desired temperature on a hot plate stirrer prior to immersion of the coupon. Stimng was accomplished with a Teflon 

coated magnetic stimng bar. Coupons were generally weighed to 0.1 mg before waxing, after waxing, after all 

dewaxing steps were complete, and after residual hydrocarbon analysis. A DI water rinse was used after each 

immersion cleaning. As a result of these tests, Turco 6849' was selected as the most promising cleaner. 

Residual hydrocarbon analysis was performed by first suspending the cleaned coupon vertically in a beaker 

and then rinsing the coupon slots with cyclohexane. After evaporation of the cyclohexane, FTIR analysis was used 

to quantify the amount of residual hydrocarbons. Only the coupon slots were rinsed and analyzed for hydrocarbons. 

The flat sides and back of the coupon were not subjected to hydrocarbon analysis. The amount of residual 

hydrocarbons detected was used as the basis for determining how well the coupons were cleaned. 

Use of steam cleaning and use of a single cleaner following the Turco 6802 did not yield acceptable levels 

of cleanliness. Use of Turco 6802 followed by a steam rinse followed by Vitro-klene did result in acceptable 

cleanliness levels. However. since one goal is to have a process that is not operator dependent, the use of steam 

cleaning, which is operator dependent, was only considered as a secondary process choice. 
X-ray Photoelectron Spectroscopy was used to analyze the surface of two small slotted copper coupons that 

had been dewaxed with the Turco 6801 / Turco 6849 / Vitro-klene sequence. The purpose was to determine the 

nature of the residual material on the surface of a cleaned coupon. Both coupons had Rigidax wax placed in the 

small slots. One coupon was only heated in the oven and not subjected to any further cleaning. This coupon only 

had a coating of residual wax. The other coupon underwent the full cleaning sequence. The coupon that only had a 

layer of wax on it contained only carbon and oxygen species. The coupon that was subjected to the cleaning 

sequence contained a residue greater than lOOA in thickness which contained carbon, oxygen, and nitrogen. This 

indicates that the residue is at least partially composed of some of the cleaning agents. This demonstrates the need 

for thorough rinsing. 

In addition to the flat coupons. testing was performed using slotted cylinders. These cylinders represent a 

scaled up and somewhat more realistic test piece than the rectangular coupons. The cylinders. shown below in 

Figure 3, were approximately 3 inches in diameter. 5 inches long and contained 64 slots of typical geometry. The 

total internal area of the 64 slots was calculated to be about 1.87 ft'. This number was used in calculations of surface 

cleanliness. The total surface area of the cylinders including the slots, area between slots, and the two circular ends 

was about 2.14 ft'. 

i X 

3/S - 16 thre'ad machined into 

center of face to fit thread of 

eye-bolt supplied 

Figure 3: Sketch of slotted cylinder. 

Dewaxing of these cylinders was performed in a manner sinlilar to that used for the rectangular coupons, 

but with somewhat larger containers for the cleaning solutions. The cleaning sequence and results for tests with the 

slotted cylinders are shown in Table I. As before, all coupons were placed in an oven for bulk wax melting. Rinsing 

steps were performed after all the cleaning sequences listed. An initial test of the new dewaxing sequence (#I ), 

where all the cleaning steps were performed in the lab. gave a final cleanliness result of I .2 mg/ft', higher than that 

observed with flat coupons or with the scrap liner. 
# 1 Cleaning sequence 

1 I Turco 6802, 230F. 3 hours (in lab) 

2 

3 

4 

5 

20% Turco 6849, 175F. -3 hours (in lab) 

8 oz/gal Vitro-klene + 2% Turco 4215, 18SF. 2 hours (in lab) 

Turco 6802,23OF, 3 hours (in lab) 

20% Turco 6849, 145F, 2 hours (in tank P-6, Auburn. WA) 

8 oz/gal Vitro-klene + -3% Turco 4215. 185F. 2 hours (in lab) 

Turco 6802.230F. 3 hours (in lab) 

20% Turco 6849. 145F. I hours (in tank P-6. Auburn. WA) 

8 odgal Vitro-klene + -3% Turco 4215, 18SF, 2 hours (in lab) 

Turco 6802, 230F, 3 hours (in lab) 

20% Turco 6849, 145F, 1 hours (in tank P-6, Auburn, WA) 

8 oz/gal Vitro-klene + 2% Turco 4215, 185F. 2 hours (in lab) 

50% Acetic acid, ambient temperature, 2 hours 

Turco 6802, 230F, 2 hours (in dewax area at SSFL) 

20% Turco 6849, I SOF, 2 hours (in lab -) 

8 oz/gal Vitro-klene + 2% Turco 4215, 185F, 2 hours (in dewax area) 

I 1.6 

0.70 

- 

0.53 

0.68. 0.97 

In the next three tests with the slotted cylinders (#2-4). the cleaning step with Turco 6849 was performed in 

a large process tank. The other cleaning steps were performed in the lab. The cylinder treated for only 1 hour in the 

Turco 6849 was significantly cleaner than the cylinder treated for 2 hours. At this point, it was suspected that the 

agitation of the solution in the lab, which consisted of suspending the slotted cylinder in a beaker stirred with a 

magnetic stirring bar, may not have been vigorous enough to get sufficient cleaning. For the last test with the slotted 

cylinders (#5), two slotted cylinders were used. To achieve better stirring, the hot oil and Vitro-klene steps were 

camed out in actual process tanks at SSFL. Also, in the Turco 6849 cleaning step, a more powerful mechanical 

stirrer was used. Both of these cylinders were cleaned to levels below I mg/ft’. The stronger agitation in all the 

cleaning steps had a significant beneficial effect on final surface cleanliness. Analysis of these cylinders was 

performed by soaking them in cyclohexane followed by FTIR analysis of the evaporated residue. 

immersion Vitroklene 

175F 185F 

Figure 4. New Dewax Process. 

The Bulk Dewax / Turco 6802 (hot oil) / Turco 6849 / Vitro-klene process shown in Figure 4 was selected 

as the new process. Turco 6849 also has a high loading capacity. Tanks of Turco 6849 at Boeing facilities in 

Auburn, WA can typically be used up to contaminant loadings of 7%. The cleanliness level achieved on a lab scale 

with this process was 0.5 k 0.2 mg/ft’ based on six replicate tests. The base line process was also performed on a lab 

scale for comparison purposes and achieved a final cleanliness of 0.2 k 0.2 mg/ft’ based on four replicate samples. 

Thus, the new dewax process was demonstrated to remove wax to a final surface cleanliness of < Img/ft’. The 

remainder of the work focused on materials corrosion tests. optimization of process parameters on a small scale, and 

demonstration of the process on a full scale part. 

In addition to cleanliness tests, corrosion tests were performed to ensure compatibility of the new cleaner 

with materials of construction. This resulted in Turco 6849 being tested with 12 different materials associated with a 

typical MCC. These included copper, Narloy-Z, Hastelloy W, Alloy 625, Alloy 718, 321 CRES, 337 CRES. 21-6-9, 

Incoloy 903, A286 and electrodeposited Nickel. The test solution was at 2O-wt% in water, the highest concentration 

recommended for use. Corrosion tests were performed at both 175F and 145F. Following preliminary abrasive 

cleaning with Scotch-Brite and DI water, the specimens were dried and weighed. They were then immersed for -30 

minutes in the heated solution while it was stirred. The samples were removed from the solution and allowed to cool 
for 24 hours to ambient temperature, rinsed. dried, weighed and evaluated. None of the materials were affected by 

contact with Turco 6849 at 145 F. There were some affects observed at 175F. but they were less than a 0.01% 

weight change and the intent is to operate at the lower temperature. 

Control factor 

Turco 6849 temperature 

Vitro-klene temperature 

Oil immersion time 

Turco 6849 immersion time 

Vitro-klene immersion time 

Turco 6849 concentration 

Vitro-klene concentration 

Process Optimization with Taguchi Matrix Tests 

cleaning time, and rinsing characteristics. In an effort to optimize these process variables, a Taguchi type test matrix 

was developed. Taguchi methods can be used to optimize several process variables with a minimum of testing. The 

goal of this type of testing is to minimize both the residual hydrocarbons present on the cleaned parts and to achieve 

consistent results from test to test. The following control factors (process variables) and levels were selected for 

analysis in an LS type matrix. 

Process variables for this process with three cleaning steps include cleaner temperature. concentration, 

Level 1 Level 2 

150F I75F 

185F 170F 

3 hours 2 hours 

2 hours 1 hour 

2 hours 1 hour 

20% 10% 

16 oz/gal 8 oz/gal 

Residual HCs 0. I 2 mg/ft’ 

S/N 1 18.5 

The temperature of the Turco 6802 oil was not selected as a factor to be studied in the Taguchi analysis. 

Since the hot oil dissolves wax, it is expected that the higher the temperature of the oil, the better the wax dissolution 

(wax removal). The oil is now operated at 230 k 20 F which is the highest temperature allowed due to safety 

concerns. For this reason, the temperature of the oil was not included in the Taguchi analysis. 

1.5 mg/ftz 

-3.9 

In the testing, three replicate coupons were used for each trial. The average of the results (mg/ft’) residual 

hydrocarbons) on each set of coupons and the average of the signal to noise ratio for each three replicate tests were 

used in further calculations. The signal to noise ratio S/N was calculated as - IO log( [(resultl)’ + (result2)’ + 

(result3)’]/3]. A higher S/N indicates more reproducibility in the results. Coupons for all tests were initially waxed 

with Rigidax wax. 

Prior to the full Taguchi matrix tests. a set of three coupons were cleaned with the assumed best set of levels 

for each of the control factors. Also another set of three coupons was cleaned under the assumed worst set of control 

factors. Results are listed Table 3. The large difference between the best and worst conditions indicates that the 

control factor IeveIs chosen are capable of showing some effect of process variables with Taguchi matrix testing. 

Control factor 

Turco 6849 temperature 

Vitro-ldene temperature 

Oil immersion time 

Turco 6849 immersion time 

Vitro-klene immersion time 

Turco 6849 concentration 

Vi tro-klene concentration 

Initially assumed “Best” Initially assumed 1 Conditions 1 “Worst” Conditions 

150F 

185F 

3 hours 

2 hours 

2 hours 

20% 

16 odgal 

175F 

I70F 

2 hours 

1 hour 

1 hour 

1 O%* 

8 odgal 
Control factor Level 1 Level 2 

L8 orthogonal 

array 

Trial A B C D E F G 

Average I Level 1 Level 2 

Residual wax, mg 

Panel 1 Panel2 Panel3 

A Turco 6849 temperature 1 50F 175F 

B Vitro-klene temperature 185F 170F 

C Oil immersion time 3 hours 2 hours 

D Turco 6849 immersion time 2 hours 1 hour 

E Vitro-klene immersion time 2 hours I hour 

F Turco 6849 concentration 20% 10% 

G Vitro-klene concentration 16 oz/gal 8 oz/gal 

0.12 0.12 0.12 

0.71 0.65 0.36 

1.54 1.18 3.13 

0.06 0.36 1.24 

2.78 3.43 2.07 

0.06 0.06 0.06 

1.95 0.89 0.36 

1.30 1.36 1.95 

0.7 1 1.36 

0.88 1.19 

0.82 1.25 

1.39 0.68 

0.83 1.24 

1.24 0.83 

0.45 1.62 

0.12 

0.57 

1.61 

0.55 

2.76 

0.06 

1.07 

1.54 

Table 4: Results of Taguchi matrix testing. 

0.02 0.02 0.03, 

0.12 0.11 0.06 

0.26 0.2 0.36 

0.01 0.06 0.31 

0.47 0.58 0.35 

0.01 0.01 0.0 1 

0.33 0.15 0.06 

0.22 0.23 0.33 

SfN 

Level 1 Level 2 

5.30 2.42 

9.66 - 1.94 

4.30 3.42 

0.79 6.93 

8.69 -0.97 

2.04 5.68 

10.91 -3. I9 

wuaf wax, 

mLflS% 

Panel1 Panel2 Panel3 Avg S/N 

18.54 

4.54 

-4.42 

2.53 

-8.99 

24.56 

-1.97 

-3.90 

Table 5: L8 orthogonal array used and raw data. 

Results of the Taguchi matrix testing are indicated in Figures 5 and 6. From Figure 5. the conditions that 

Turco 6802 oil; 3 hours immersion time. 

Turco 6849; 10% concentration, 150F. 1 hour immersion. 

favor the least amount of residual hydrocarbons (cleanest surface) are: 

Vitro-klene; 16 oz/gal concentration, 185F. 2 hour immersion. 

The conditions that favor the cleanest surface are also the conditions that yield the highest (best) S/N. This 

last result is normal in a “least is best” type of Taguchi analysis. For the Turco 6802 and the Vitro-Nene solutions, 

all results are as expected; a higher concentration, higher temperature and longer immersion time are beneficial. The 

effect of a higher Vitro-klene concentration is especially evident. For the Turco 6849. results are the opposite of 

what was first expected. For Turco 6849, a lower temperature and shorter immersion time were better. A lower 

concentration was also beneficial. but the effect of concentration was somewhat less than other factors. 

One final confirmation test was performed using all the optimized conditions listed above. Results from the 

three coupons tested under the optimized conditions were 0.06,0.06, and 0.06 mg/fi’. This gives a S/N of 25. These 

results are better than what was originally obtained with the initially assumed “best” conditions. It can also be seen 

from the raw data that for trial #6 all the optimum conditions were used except that the Turco 6849 was operated at 

175F and the Turco 6802 was operated for only 2 hours. This set of conditions also gave the same results as the 

optimum conditions. From this testing, the effects of process parameters were determined with optimized conditions 

as listed above. Using the predictive equations, the effect of any combination of the levels tested can be predicted. 

This may be valuable for an initial estimate of any trade off between cost, cycle time and process quality. 
-1 2.0 

# > 

* "#lO.O 

+ 8.0 

(v * 6.0 + 

N 

N 5 4.0 Y 

g 2.0 - 

z 0.0 

3j 

II 

-2.0 

-4.0 

Figure 5: Results of Taguchi matrix testing. 

Average values of residual hydrocarbons. 

1.8 

1.6 

gl .O 

- 

~0.8 

q0.6 

0, 

ao.4 

0.2 

0.0 

Figure 6: S/N results for Taguchi matrix testing. 
Full Scale Process Demonstration 

throat MCC liner. This liner, shown in Figure 5 below, was 14 inches OD at the widest point, 29 inches tall and 

contained open channels. Each channel has an internal surface area of about 0.064 ft'. 

Denionstration of the immersion process on a full-scale test article was performed with a scrap SSME large 

Figure 7. Scrap SSME large throat MCC liner. 

All operations except immersion in the Turco 6849 were performed at Rocketdyne. Tank P-6 at Boeing 

facilities in Auburn Washington contains Turco 6849 at a concentration of about 18% and was used for the 

immersion step. This tank is commonly used for cleaning aluminum, titanium, stainless steels and Inconel alloys. 

The tank is fitted with two turbulators for agitation and is typically operated at 140F to 150F. The liner was placed 

in a basket which was lowered into the Turco 6849 tank. After cleaning, rinsing, and drying, the liner was wrapped 

in Aclar sheet prior to shipment. The following sequence of process steps were performed: 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

Channels filled with Rigidax Wax (Canoga) 

Liner heated in oven for bulk wax removal (Canoga) 

Immersion in Turco 6802 oil at 7ROF for 2 hours (SSFL dewax area) 

Rinse and GN2 dry (SSFL dewax area) 

Immersion in 18% Turco 6849 at 145F for 2 hours (Auburn, WA) 

Part soaked briefly in 140F rinse water (tank P4A in Auburn, WA) 

Part soaked briefly in 103F rinse water (tank P4B in Auburn. WA) 

Liner placed in hot air drier (tank P-7 in Auburn, WA) 

Immersion in Vitro-klene tank, Soz/gal, 185F. 2 hours (SSFL dewax area) 

10. Rinse and GN2 dry (SSFL dewax area) 

After all the cleaning steps were complete, the residual hydrocarbon content in the slots was measured. 

Each of ten adjacent slots was rinsed with cyclohexane. The cyclohexane was collected. combined for a total of 

about 300 ml and evaporated. FTIR analysis was used to quantify the amount of residual hydrocarbons. Duplicate 

analyses were performed on five different sections of the liner which resulted in an overall average of 0.33 0.28 

mg/ft' ,with the highest value being 0.70, all at a final cleanliness level less than lmg/ft'. 

Conclusions 

Conclusions from the study on Dewax development include: 

A robust process has been demonstrated on small slotted coupons and on a scrap SSME MCC liner that is 

capable of wax removal to less than 1 mg/ft' 

The new cleaner passes embrittlement, rinsability, and corrosion tests and has a VOC content < 50 grams per 

liter. 

Process optimization through Taguchi matrix analysis has allowed process parameter selection to reproducibly 

yield coupons cleaned to the levels of analytical capability (< 0.1 mg/ft') 

Acknowledgments 

this effort by conducting these laboratory experiments in their usual excellent manner. 

The authors would like to thank Dr. Carl Schack and Mr. Larry Hill (Boeing Canoga Park) for supporting 
Highly Effective, Low Toxicity, Low Environmental Impact Total Flooding Fire 

Suppressants 

Suzanne M. Glass, Patrick M. Dhooge, and Jonathan S. Nimitz 

Environmental Technology and Education Center (ETEC) 

4500-B Hawkins St. NE 

Albuquerque, NM 87 109-45 17 

Phone: (505) 345-2707 

httd/www.etec-nm.coni 

pdhooge@etec-nm.com - I [ ininiitzQetec-nm.coni 1 

INTRODUCTION 

Halon 1301 (CFIBr) has been used for decades as the primary fire suppression agent for 

areas where powder agents cannot be used because of concerns for sensitive equipment. Halon 

1301 is an excellent extinguishing agent, effective at about 3% in air and quite non-toxic. It has 

an effective exposure limit much greater than its extinguishing concentration, so it can be used in 

normally occupied areas. 

The ability of a chemical to destroy stratospheric ozone is its ozone-depletion potential 

(ODP). ODP is the amount of ozone destroyed per pound of a chemical, relative to the standard 

CFC- 1 1 with an ODP = 1 .O. Because halons have been implicated in stratospheric ozone 

depletion, their production was stopped at the end of 1995 under the provisions of the Montreal 

Protocol plus later amendments (Environmental policy and law; Grey; International Lawyer; 

Zurer). In the U.S., the Clean Air Act Amendments of 1990, Presidential directives, and DoD 

Directive 6050.9 implemented this phaseout (United States a; United States b). These regulations 

and penalties have provided strong incentives for U.S. businesses to decrease CFC use. The 

Omnibus Budget Reconciliation Act of 1989 mandates high Federal taxes on CFCs and halons, 

designed to price them out of the market. The taxes also capture for the government the windfall 

profits that would otherwise go to producers as scarcity drives up prices. 

Several replacements have been developed for Halon 1301. One is carbon dioxide, which 

has been used as a firefighting agent for many years. However, a high concentration of carbon 

dioxide is necessary to inert fuels. The effective concentration for inerting with carbon dioxide is 

approximately 29%, which is above the concentration lethal to humans. HFC-227ea is being 

used extensively to replace Halon 130 1 systems in normally occupied areas and some normally 

unoccupied areas. However, since the effective concentration of HFC-227ea is about three to 

four times that of Halon 1301 the extinguishing systems have to be larger and new extinguishing 

systems have to be installed. HFC- 125 is also being sold as an extinguishing agent (Nimitz). It 

has problems similar to HFC-227ea, with a greater concentration needed for effectiveness and 

the need to use a larger system. This is a particularly onerous penalty in aircraft and spacecraft, 

where weight and space are extremely important, and substitution is often impossible in existing 

aircraft due to space limitations. 

Several research groups have conducted extensive and productive studies on the inerting 

concentrations and combustion chemistry of halons and candidate halon replacements. These 

groups have included, among others, researchers at NIST, NMERI, and the Naval Research 

Laboratory (Brabson, et al.; Clay, et al.; Fleming, et al.; Grosshandler, et al. a; Grosshandler, et 
al. b; Hamins; Heinonen; Maranghides, et al.; Moore, et al.; Paige; et al.). Intensive 

investigations have been conducted to find a general replacement for Halon 1301, thus far to no 

avail. Some very effective agents such as Fe(C0)s and other organometallics, PBr3, and 

phosphonitriles have been discovered, but they are either unstable, highly toxic, produce highly 

toxic byproducts in flames, or would be expensive to manufacture. 

ETEC has performed studies on a number of alternative fire suppression agents, 

including iodofluorocarbons (IFCs), and in particular CF3I. Iodofluorocarbons (IFCs) have been 

shown to have excellent physical properties, zero ozone-depletion potential (ODP), extremely 

low global warming potential (GWP), good thermal stability, and relatively low toxicity. 

Previous work by the proposed PI determined that CFJ could provide an effective, long-term 

Halon 1301 replacement. CF3I is almost exactly as effective as Halon 1301. Subsequently, CFJI 

has been approved under the U.S. EPA’s Significant New Alternatives Policy (SNAP) for use as 

a Halon 1301 replacement in unoccupied areas. CFJ has also recently been recommended as a 

Halon 130 1 replacement for inerting the fuel tanks in the F- 16 (Vitali). 

The one major disadvantage of CFJI is its relatively low threshold cardiac sensitization 

level. Many gaseous hydrocarbons and halocarbons sensitize animal hearts to adrenalin. The 

possibility of death from heart fibrillation after exposure to a halocarbon was first realized in the 

1960s. A standard test was developed at that time to determine the relative cardiac sensitization 

of compounds. The test uses Beagle dogs that are injected with enough ephinephrine (adrenalin) 

to be barely under the amount that would cause that dogs’ heart to go into fibrillation (this 

dosage is determined for each individual dog in the test group). After injection, the dogs are 

exposed to concentrations of the test compound in air. The minimum amount of the compound 

found to induce heart irregularities is the LOAEL, or Lowest Observable Affect Exposure Limit. 

The NOAEL, or No Observable Affect Exposure Limit, is the maximum concentration the dog 

can be exposed to with no affect. This test is quite rigorous, since the dogs are already just below 

the point of fibrillation due to the very high ephinephrine level. It has been estimated that the 

levels used in these tests may be 100 times or more higher than would be seen in a highly 

frightened test subject (Vinegar). This test’s relevance is being questioned, but it remains the 

standard at this time. CF~I’S NOAEL of 0.2% is well below its effective concentration for total 

flooding applications, and therefore it is not approved for use in normally occupied areas. 

As part of its effort to develop low atmospheric impact, high capacity, energy-efficient 

refrigerant blends for NASA Kennedy Space Center, ETEC investigated several gaseous 

combustion suppression agents. The rationale for this was to inert flammable compounds that are 

otherwise excellent refrigerants. Examples of such compounds are R- 152a, R- 16 I, and propane. 

If a gaseous combustion suppressant could inert the flammability of a good refrigerant 

compound at a low enough concentration that the good refrigerant properties of the flammable 

compound could be retained, the result would be a desirable new refrigerant blend. There is 

precedent for this approach in refrigerant blends such as R-500, a blend of R-152a and R-12 

where R- 152a’s flammability is suppressed by R- 12. 

In the course of our studies, some interesting results were obtained, including some 

unexpected results involving the flammability suppression effectiveness of CF3I and 

identification of a new suppression agent that appears to be considerably more effective than 
Halon 1301 or CF3I. The new agent has promise of having acceptably low toxicity to be used as 

a total flooding fire suppression agent in normally occupied areas. 

In addition, development work for the U.S. Air Force Research Laboratory on new IFCbased solvents produced data on their flammability suppression effectiveness and flammability. 

The results of these studies included here because they are also of potential interest for fire 

suppression applications. 

RESULTS AND DISCUSSION 

Flammability Suppression of Solvents by Selected IFCs 

The definition of flammability for liquid compounds is a flash point less than or equal to 

333.5 K (60.5"C or 141°F). A combustible liquid is defined as having a flash point between 

333.5 K and 366 K (93°C or 200°F) (United States c). A liquid with a flash point above 366 K is 

often described as nonflammable or noncombustible, but we prefer to use the term fire-resistant. 

Any material that can oxidize can be made to combust under severe enough conditions (for 

example, in high pressure oxygen). 

The studies done to support alternative solvent development concentrated on nearazeotropic blends of IFCs with flammable solvents. Near-azeotropic blends were identified by 

computer modeling to narrow the range of candidate blends followed by distillations of mixtures 

to identify near-azeotropic, Le., constant-boiling, compositions. In distillation studies, nine (9) 

near-azeotropic blends of IFCs with flammable solvents were identified. These blends were 

tested for flammability using Setaflash' open and closed cup (ASTM D 4206-89 and ASTM D 

3828-93), wick (ASTM D 4207-91), aerosol spray (ASTM D 3065-72), and vapor phase (ASTM 

Method E-68 1 ) tests. 

Three of the nine near-azeotropic blends proved to be nonflammable. It was found that, in 

general, 40 - 60% by volume of the IFC was needed in the blend to render it nonflammable. 

Some of the variation appeared to be dependent on the chemical nature of the flammable 

compound. For instance, hydrocarbons such as pentane and cyclohexane required 55 - 60% by 

volume IFC for inertion, while alcohols such as ethanol and isobutanol required 40 - 45% by 

volume IFC. 

The Vapor-Phase Flammability of Selected IFCs 

Vapor-phase flammability tests produced some interesting results. The ASTM E-68 1 

testing reported in this section was conducted based on the older version of this test (5 L test 

flask). ASTM E-68 1 is a very severe test of flammability in air that is normally used for gases 

such as gaseous fuels and refrigerants. This is not a standard test for solvent flammability. In this 

test, the compound (or mixture of compounds) at the desired test concentration in air containing 

50% relative humidity is introduced into a 5 L spherical flask maintained at 373 K, allowed to 

equilibrate, and sparked repeatedly with a 15 KV, 30 mA spark between two platinum 

electrodes. Desired concentrations are prepared by pressure measurements. The compound or 

mixture of compounds is flammable if a resulting flame exceeds the extent of a 45" cone marked 

on the flask. It is not one of the standard tests used for solvents, and is not mandated for solvent 

flammability testing. All of the near-azeotropic blends were found to be flammable by this test, 

but this test also gives flammability limits in air for the normally nonflammable solvents 1, I, 1- 
t Compound Lower Flammability Limit Upper Flammability Limit 

(mole % in air) 

CFC-113 none none 

TCA 6.5 15.5 

(mole % in air) 

TCE I 8 I 10.5 

perchloroethylene 

CFzI 

none none 

none none 

1 -CBF~I 

1 -CZoI 

Flammability Suppression Effectiveness of CFJ on Selected Fuels 

Results of some of the studies we had conducted indicated that there might be an effect 

from fuel type on the combustion suppression effectiveness of IFCs. Of particular interest to us 

in our refrigerant development studies was CFRI. 

13.5 34.5 

8.2 33.1 

In order to determine some of the effects of the fuel type on the inerting concentration of 

CF31, a set of simple fuels and a gas phase test apparatus was used. A gas flammability apparatus 

based on ASTM E-68 1 was used to obtain homogeneous inertion concentrations not dependent 

on flow rates, position of suppressant injection, or mixing efficiency. The test apparatus used in 

this testing was the updated apparatus specified in the recently revised E-68 1 test procedure. The 

revised version of the test uses a 12 L spherical glass flask maintained at 6OoC. 

Fuels consisting of a single chemical with small molecules were used to keep complex 

combustion intermediates to a minimum and to determine whether any trends with chemical 

structure were apparent. The fuels were propane, cyclopropane, isobutane, dimethyl ether, and 

fluoroethane. The flammability results, over a range of concentrations, were used to prepare 

flammability diagrams and determine the ratios of CFJ to fuel vapor required for inertion. 

Figure 1 shows an example of an inertion diagram for one of the fuels tested with CF3I. 

The data were examined in two ways. In the standard approach, the concentration of CFBI needed 
to inert any concentration of air in the fuel was determined by drawing a tangent line to the 

flammable region perpendicular to the CF3I axis. We also determined the ratios of CF3I to fuel 

needed to give nonflammable compositions in air. To achieve this a tangent line was drawn from 

the origin through the lower borderline of the flammable region. The slope of this line gave the 

minimum ratio of CF3I to the flammable component necessary to inert the blend at any 

concentration in air. We refer to this line as the dilution line because it represents all possible 

dilutions of the borderline nonflammable composition in air. Both of these tangent lines are 

shown in Figure 1. 

+ Flammable Nonflammable 

10.0% 7- I 

8.0% 

2.0% 

0.0% I 0.0% 2.0% 4.0% 6.0% 8.0% 10.0% 

Yo CF31 

Figure 1. Inertion Diagram for Propane and CFJI Flammability by ASTM E-681 

Table 2 shows the percentages of CF3I needed to inert the five fuels tested and the ratios 

of CF3I to fuel needed for inertion. All percentages are given by moles. The absolute percents of 

CF3I needed to inert the fuel have a relatively high uncertainty (*0.5%) because we were 

primarily interested in the ratios of extinguishant to fuel. 

Table 2. Mole Percentages and Ratios of CFJI Needed to Inert Selected Fuels in ASTM E-681 

Flammable Gas 
The results obtained are consistent with known previous data for combustion suppression 

effectiveness of CF3I. Previous work has shown that CF3I and Halon 130 1 have very similar 

inerting concentrations for propane in the explosion sphere, 6-7 mole percent absolute or 54-58 

mole percent in fuel blends (Moore, et al.; Heinonen). Although the apparatus used in the 

previous studies was somewhat different from ours, the results for propane are in good 

agreement. The results for isobutane are in excellent agreement with the results of an EPA study 

which found the flammability borderline to be at a ratio of 62 mole percent CF3I to 38 mole 

percent isobutane (Baskin, et al.). 

Fuel 

ethane (for comparison) 

propane 

isobutane 

cyclopropane 

fluoroethane (R- 16 1 ) 

dimethyl ether 

The unanticipated finding was that CF3I was extremely ineffective at inerting dimethyl 

ether and cyclopropane, requiring over 40 mole percent absolute or over 95 mole percent in the 

fuel blend. To attempt to understand the somewhat surprising ineffectiveness of CF31 in inerting 

dimethyl ether and cyclopropane, we considered the fuels' chemical structures and heats of 

combustion. Table 3 lists heats of combustion for the fuels. No differences are apparent that 

explain the results obtained. Chemically, the differences between these fuels and the 

hydrocarbons or hydrofluorocarbons are that one of the fuels contains an oxygen atom and the 

other has a highly strained ring, both of which may significantly affect chemical reactivity. 

Clearly, these fuels are either increasing the rate of flame radical propagation or heat generated, 

or decreasing inhibitory species. It is also possible that exothermic chemical reactions are 

occurring between CF3T and dimethyl ether or cyclopropane. However, our data set is very 

limited and studies with additional fuels would be needed to determine what is occurring. In any 

event, the results obtained here should not affect the large majority of proposed uses of CF3I as a 

total flooding fire suppressant, since fuels of concern rarely contain ethers or cyclopropanes. 

-AH,", kcallmole -AH," per carbon atom, kdmole 

373 186 

5 30 177 

685 171 

500 167 

348 I74 

308 154 

Table 3. Heats of Combustion of Selected Fuels 

Flammability Suppression Effectiveness of ETEC Agent A 

In the course of our investigations into combustion suppressant agents for flammable 

refrigerants, several other known combustion suppressant agents and several experimental 

combustion suppressant agents were tested. One agent proved to be particularly effective in 

inerting gaseous fuels. The new agent, given the temporary name ETEC Agent A, is in general a 

better combustion suppressant than CF31, HFC-125, or HFC-227ea, and, from the toxicity data 

that is known, has promise to be acceptable for use in normally occupied areas. ETEC Agent A 

is proprietary at this time, but the results of combustion suppression testing with it can be shown. 

Figures 2 through 4 show some combustion suppression results for ETEC Agent A 

compared to CFJ and HFC-227ea. As shown in the previous section, CF3I was found to be very 

ineffective in suppressing the combustion of cyclopropane and dimethyl ether. HFC-227ea is 
somewhat effective on these fuels, but still requires a large amount to inert. ETEC Agent A is 

significantly better than both CFRI and HFC-227ea on these fuels that are very difficult to inert. 

CF3I is very effective in inerting isobutane and other hydrocarbons. HFC-227ea is considerably 

less effective than CF3I with respect to hydrocarbons, the source of HFC-227ea's needed extra 

volume and weight compared to Halon 1301. ETEC Agent A is almost as effective as CFJ and 

Halon 1301 on isobutane, a typical hydrocarbon fuel. 

HDimethyl Ether 

mCF3I 

OHFC-227ea 

OAgent A 

Figure 2. Flammability Suppression of Dimethyl Ether by CF31, HFC-227ea, and ETEC Agent A 

(note: CFJI totally ineffective, 100% needed to inert) 

0% 10% 209 30% 40% 50% 60% 70% 80% 90% I(M% 

Percent Cyclopropane 

Ei Cyclopropane 

W CF31 

0 HFC-227ea 

0 Agent A 

Figure 3. Flammability Suppression of Cyclopropane by CFJI, HFC-227ea, and ETEC Agent A 

(note: CFJI totally ineffective, 100% needed to inert) 
HIsobutane 

WCF3I 

OHFC-237ea 

Fuel Absolute Mole % 

CFJ to Inert 

dimethyl ether 57 

cvclotxotmne 44 

0% 10% 2070 30% 40% 50% 604 70% 80% 90% 100% 

Percent lsobutane 

Absolute Mole % 

HFC-227ea to Inert 

Absolute Mole % ETEC 

Agent A to Inert 

11 7.1 

12 8.3 

Figure 4. Flammability Suppression of Isobutane by CFJI, HFC-227ea, and ETEC Agent A 

Table 4 gives absolute mole percentages needed to inert the three fuels shown in Figures 

2 through 4. 

I isobutane 5.2 11.5 6.5 

CONCLUSIONS 

A new combustion suppression agent, ETEC Agent A, has been identified that has 

promise of being an effect Halon 1301 replacement in total flooding fire suppression applications 

for normally occupied areas. The new agent appears to be particularly effective on fuels whose 

flammability is difficult to suppress. More extensive flammability suppression studies need to be 

done, and the toxicity of the new agent needs to be established in detail. A retrofitable Halon 

1301 replacement that could be used in the same size and weight systems would save millions of 

dollars in fire suppression system replacement costs, and would be particularly valuable on 

aircraft. 

ACKNOWLEDGEMENTS 

We are grateful for support of the work described here by NASA Kennedy Space Center 

and the U.S. Air Force Research Laboratory. We would like to thank Dr. Jacqueline Quinn of 

NASA Kennedy Space Center and Dr. Edward Snyder of the U.S. Air Force Research 

Laboratory for their valuable technical support during the efforts. 
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! 
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Zurer, P., ”Ozone Treaty Tightened, CFC Substitutes Controlled,” Chemical & Eirgiizeeriizg 

News, December 7, 1992, p. 5. (Montreal Protocol 1992 Copenhagen amendments) 
Promoted Combustion of Metals in a High-pressure, Flowing Oxygen Environment 

Miguel J. Maes 

NASA Johnson Space Center 

White Sands Test Facility 

Las Cruces, New Mexico 

(505) 524-5677 

L.;, /.. f 

Joel M. Stoltzfus 

NASA Johnson Space Center 

White Sands Test Facility 

Las Cruces, New Mexico 

(505) 524-573 1 

I ibtoipt Lt u-ec r\ 1 

A BSTR4 CT 

Traditional promoted combustion testing has used 0. I25 in. dia samples that are ignited in a pressurized. 

oxygen-enriched environment. Many years of testing this sample size have yielded useful data regarding threshold 

pressure. or the minimum oxygen pressure required to support self-sustained combustion. However. when a 

material is tcstcd in a flowing system. the threshold pressure changes. White Sands Test Facility has developed a 

test system to burn samples in flowing gaseous oxygen. Current sample contigurations are 0.5 in. dia rods and 

1.25 in. dia pipes aith pressures ranging up to 2000 psi and gas velocities reaching 200 ft!s. This paper describes 

the test apparatus, modifications made as the result of a fire, and a description ofthe tests currently being performed. 

INTRODC’CTION 

In oxygen systems. metals selection is very important to ensure compatible materials are used for the 

system’s operating conditions. Much data have been collected regarding material flammability versus pressure [I]. 

Typically. materials bum better as pressure increases. These data provide a good basis for choosing materials based 

on their flammability. However. these data are based on a material’s flammability in a static oxygen environment. 

When the oxygen is flowing, material flammability can be enhanced or reduced depending on the flow velocity. 

The NASA White Sands Test Facility (WSTF) has developed a test system that can perform promoted combustion 

tests in flowing oxygen conditions whilc controlling pressure and velocity past the test sample. This paper describes 

the test apparatus, modifications made as the result of a fire, and a description of the tests currently being performed. 

B.3 CKGROL‘ND 

For years it has been known that materials bum much better at higher oxygen concentrations. As the 

demand of increased operating pressure in oxygen systems became more acute, particularly in the aerospace 

industry but also in industrial applications, the incidence of oxygen system fires increased because the normally 

inflammable metals were flammable at the higher operating pressures. This prompted the area of study known as 

promoted combustion. The purpose of the present study was to characterize the fire propagation properties of 

carious metals and alloys [I]. Benz. Shaw. and Homa have outlined two major considerations that must be 

addressed when determining the fire hazards of metals or alloys. ‘‘First it must be determined whether the material 

will ignite. which requires knowledge ofthc minimum energy rate and temperature for ignition. Second, it must be 

determined whether the material will support combustion after the stimulus of the ignition source has terminated’ 

[I]. Previous promoted combustion testing typically occurred with 0.125 in. rod configurations that were supported 

at either the top or bottom of the sample and ignited at the opposite end. The ignition source consisted of a 

magnesium cylindrical sleeve, or promoter, that was press-fit onto the sample. The promoter was wrapped with 

nickel-chrome or similar-type wire and ignited electrically. This “kindling chain” was effective for consistently 

igniting the samples, which could be tested over a wide range of pressures, depending on the chamber design. All 
chamber designs shared a coininon feature in that they wcrc capable of producing only static conditions of oxygen 

before the test and had no way to flow the oxygen at controlled velocities. 

Importance of Understanding Velocity 

The importance of fluid velocity affecting material flammability is particularly evident when building a 

campfire, for which the kindling chain of the leaves, twigs, and dead grass catches fire first and in turn ignites sticks. 

which ignitc split logs, and so on. Suppose that the kindling wasn't burning as much as one would like. The usual 

rcsponse is to blow onto the embers. The normally unexcited embers now become more energetic due to the 

dynamics of the situation. The driving mechanism creating this apparent increase in flammability is the flow 

velocity. If the velocity is too high, the flames can be blown out. However, gas velocities below this range can 

increase the potential for fire. Flowing gas produces a forced convection effect that increases the availability of 

oxygen for consumption at the burning interface. The flowing oxygen also decreases the concentration of 

inflammable combustion products around the burning interface simply by blowing them away. 

Test System Description 

The test system is modeled after the static pressure promoted combustion apparatus. It consists of a 

cylindrical chamber that can be pressurized to 45OOpsi (Figure 1 ). The chamber body is made from 304 stainless 

steel. and the interior is lined with copper to protect it from the burning metal samples. Near the inlet. there is a 

flow-straightening device made from K500 Monel'. and directly below it is a copper sample holder. Welded on 

either side ofthe chamber are vent ports lined with coppcr, which protects them from molten debris. 

Thc system is designed so that it is very difficult for debris to make it outside the chamber. A copper slag 

filter separates the burning sample from the vent outlets. A series of 0.125 in. dia holes has been drilled through the 

side of the filter at a 15 degree downward angle to minimi7c slag escape. This filters out any debris larger than 

0.125 in. dia. Although debris smaller than this can fit through the holes. the particles must changc their direction to 

travel up the 15 degree incline. Specifically sized orifices can be placed on these vents to control the mass flow rate 

of oxygen out of the chamber. Below the slag filter is a copper catch cup whose mass is sufficient to conduct the 

heat from the molten slag away without damage to the cup or chamber body. Two copper terminals that extend 

down from the top exterior of the chamber ignite the samples. Each terminal is attached to a Kemlon'R2 electrical 

feedthrough. The terminals have adapters that can be mated with banana-plug type connectors. The pyrofuse wire 

used to ignite the promoters is attached to the banana plugs. A sapphire crystal view window is mountcd onto the 

chamber wall, with copper crush washers providing the sealing surfaces. The window is housed in a Monel 

viewport boss flange. A borescope connected to a video camera is mounted to this viewport flange to view and 

record the burning sample. The chamber is located downstream of a heat exchanger capable of heating the oxygen 

to 1000 OF. The system supplying the oxygen is capable of producing 6000 psi at a mass flow rate of 8 Ib,,/s. 

Three pressure transducers and one thermocouple record the test data. One transducer is tapped into the 

chamber wall opposite the view window to record the chanibcr pressure. which is also thc test article pressure. The 

other two transducers and thermocouple are located in a four-way block that is connected directly upstream of the 

chamber inlet. One of these transducers is used as a report-back channel to a pressure control valve, which is 

computer controlled and regulates itself to achieve the desired pressure. 

Test Configuration 

Test samples are held vertically and supported at the top from the copper sample holder with setscrews. 

Oxygen flows into the chamber from top to bottom, and the test samples are ignited at the bottom. Therefore, this 

testing cvaluates material flammability in a counterflow environment. 

Currently WSTF is testing two different sample configurations. One configuration is flow in a pipe. Pipes 

ranging up to 1.25 in. dia schedule XX can be tested at pressures up to 1500 psi, with velocities of 50 ftis, 100 ft/s, 

and 200 ft/s. The samples are 5.5 in. long. and the oxygen flows inside the pipe. Depending on the pipe thickness. 

the promoter is counterbored and either sunk into the wall thickness or attached to the exterior of the pipe. 

MonelN is a registered trademark of lnco Alloys International. Inc I 

' Kemlon" is a registered trademark of Kemlon Products. 
Oxygen Inlet 

Kenilon” Electrical 

Monel’ Flow Straightener 

Brass Rod \ 

Figure I 

First Test Apparatus. Front View (left) and Side View (right) 

The other configuration is a 0.5 in. dia rod. A 1.378 in. ID mock pipe called the velocity tube, consisting of 

a copper upper section and a quartz lower section, is clamped into the sample holder. The quartz tube slides into a 

countersunk region in the copper tube, and the two are connected by a worm clamp that compresses petals on the 

copper tube against the exterior ofthe quartz tube. Quartz is used because of its extremely low coefficient of 

thermal expansion, which keeps it from cracking or breaking if it comes into contact with molten metal; the molten 

metal simply quenches onto the quartz. The 0.5 in. rod is screwed onto a brass sample holder, and the test article 

assembly is then screwed into the bottom ofthe Monel flow straightener. Similar to the pipes, the rods have been 

tested at pressures ranging up to 1500 psi at velocities of 50 ftis, 100 fUs, and 200 ftis. Flowing oxygen passes over 

the sample but within the velocity tube. By knowing the cross-sectional flow areas and the inass flow rate, gas 

vclocity can be calculated. 

RESULTS 

The original intent of this paper was to present combustion data for 0.5 in. dia aluminum, carbon steel, and 

304 stainless rod samples. However, during testing of a 1.25 in. dia schedule XX pipe sample at a 500 psi, 200 ft/s 

flow velocity, an event occurred that resulted in destruction the test chamber. Therefore, no test data were collected. 
The remainder of this paper will discuss thc results ofthe firc and modifications that have been pcrformcd to rebuild 

a better chamber. 

After test sample ignition, a largcr fire began on thc right side of the chamber. Most of thc right vent port 

(Figure 2, front view) was consumed during the fire. The chamber fire was extinguished by shutting off the oxygen 

flow. A 3 in. dia hole remained where the vent hub was welded to the chamber, and 75 to 90 percent of thc clamp 

and right exterior hub were consumed in the fire. Internally, the thinnest sections of the copper qucnch filter and 

most of the chamber sleeve were melted or eroded away on the right side. This was the first test conducted on 

schedule XX pipes in this chamber at this flow velocity. Schedule XX pipes had been tested in this chamber at 

higher pressures and slower velocities of up to 1500 psi and 50 ftis. After investigation of this incident. it was 

determined that a dimensioning tolerance exposed a 0.04 in. annular ring of chamber wall around each copper vent 

sleeve. The vent sleeves and the Monel viewport boss flange protruded through the copper chamber slecve as a 

means of eliminating exposure of molten metal to the chamber wall. This of course was dependent on machining 

tolerances being tight cnough to seal around the protruding pieces. Recall that the chamber was inadc of 304 

stainless steel. for which data show the lower flammability threshold to be around 500 psi. It is believcd the 200 ftis 

flow was more efficient at distributing molten slag into crevices leading to the chamber wall. The conditions 

between the copper liner and the chamber wall produced a condition favorable to combustion ot'a nominal 4.5 in. 

dia stainless steel pipe with a wall thickness of 0.674 in. 

Figure 2 

Bumthrough of First Test Apparatus, Right Vent Port 
Test .4pparatus Modifications 

The test apparatus has since been modified and rebuilt (Figure 3), which docs not show the entire assembly 

as in Figure I. Instead, it shows the major modifications which includes enlarging the inner diameter of the chamber 

to increase the thickness ofthc copper liner. This increased thickness allows for a sufficient counterbore to be 

drilled to acconiniodate the vent sleeves. Thc sleeves no longer protrude into the flow; instead, they extend just to 

the inner diameter ofthe chamber sleeve. The sleeves now have a recessed lip that exactly fits the counterbore 

depth. Also. the vent sleeves have been madc thicker to provide more protection to the vent walls. Another 

modification was to eliminate the protruding edge of the viewport flange. The overall length of flange was 

shortened. and one end was "fishniouthed" to the exact radius ofthe outer diameter of the inner sleeve. When 

bolted down. the edge ofthis fishmouth cuts into the chamber sleeve, thereby producing a sealing surface. To 

protect the resulting cavity. another modification was made to the chamber sleeve. The top 4 in. of the sleeve now 

has a counterbore to fit large quartz sleeves. The inner dianieter of these quartz sleeves matches the inner diameter 

ofthe lower portion ofthe chamber sleeve. Once again, quartz is used bccausc the molten metal quenches onto the 

quartz sleeve without any damage to the chamber. In addition to the modifications made, another component was 

added to further fireproof this new chamber. A quench ring that is press-fit into the inner diameter of the chamber 

sleeve directly above the quench filter has been added. This quench ring is simply a thick ring of copper to act as a 

heat sink to protcct the upper lip of the quench filter. 

Figure 3 

Second Test Apparatus after Improvements. Front View (left) and Side View (right) 
Thc remaining 1.25 in. dia samples have been tested at the same flow velocities that destroyed the first 

chamber. Thc modifications performed have proved to be effective in eliminating the problems that existed in the 

first tcst chamber. Tests that have been performed to date include 0.5 in. dia rods and 1.25 in. dia pipes at 500 psi. 

1000 psi, and 1500 psi with vclocities 50 ft/s. 100 ft/s, and 200 ft/s. Flammabilitics are increased with flow velocity, 

but there exists a point at which the velocity is too great for a material to sustain combustion. WSTF now has the 

capability to test metals flammability in flowing conditions. A new realm of data can and should be obtained for 

materials in flowing oxygen. Perhaps there are conditions that materials exhibit increased flammability with 

pressures lower than current threshold data shows when the oxygen is flowing. To a systems engineer, this type of 

data would be very useful to improve the design of oxygen systems. 

REFERENCES 

[I] Benz, F. J., Shaw. R. C., Homa, J. M. “Burn Propagation Rates of Metals and Alloys in Gaseous Oxygen.” 

Flnmnirrhili!,~ atid Sen.siti\igi cf,k4otc~riul.s it1 O.~~,.gc.ri-Enric.hed Atriio.sphri.r~.s: Second l’oliinie, ASTM STP 9 10, M. 

A. Benning, Ed., American Socicty for Tcsting and Materials, Philadelphia. PA, 1986. pp. 135-1 52. 
-> 

'r 564 /o; ,1 &L , 

PROBLEM SOLVING APPLICATIONS OF CHEMICAL FINGERPRINTING 

MICHAEL 0. KILLPACK, DENNIS J. FIFE, CHAD R. SAUNDERS, CHARLES R. WHITWORTH, 

AND WILLIAM H. MCCLENNEN, Thiokol Propulsion, Analytical Laboratories, P.O. Box 707 M/S 245, 

Brigham City UT 84302-0707 

Good manufacturing processes are dependent on the ability to foresee, reduce, or quickly resolve problems 

critical to the quality and consistency of the end product. Thiokol has initiated a chemical fingerprinting 

program in conjunction with NASA, designed to identi5 and mitigate such manufacturing problems 

through a better understanding of the base materials. A historical database with real-time access maintained 

by a core of material specialists is an essential problem-solving tool. This "fingerprinting process" will bc 

discussed in tcniis of identification of critical materials and analysis tcchniques, development of a 

comprehensive database, coordination and concerns of vendors, and actual cxaniplcs where fingerprinting 

has been used to reduce and rcsolvc problems. 
PROBLEM SOLVING APPLICATIONS OF CHEMICAL FINGERPRINTING 

MICHAEL 0. KILLPACK, DENNIS J. FIFE, CHAD R. SAUNDERS, CHARLES R. WHITWORTH. 

AND WILLIAM H. MCCLENNEN, Thiokol Propulsion. Analytical Laboratories, P.O. Box 707 ME 245, Brigham 

City UT 84302-0707 

Good manufacturing processes are dependent on the ability to foresee, reduce. or quickly resolve problems. 

Thiokol has initiated a chemical fingerprinting program in conjunction with NASA, designed to identify and 

mitigate such manufacturing problems through a better understanding of the base matcrials as provided by the 

vendor as well as their interaction with other materials used in the manufacturing proccss. The major objectives of 

the fingerprinting program is to develop a comprehensive data base on critical materials. reduce the probability of 

unexpected or unrecognized changes, enhance the ability to detect and resolve material compatibility and 

environmental issues as well as understand how a material agcs/degrades. 

The fingerprinting process starts with the identification of critical materials and assigning of a materials 

specialist from the analytical labs. Along with the materials specialist, a team of personnel from manufacturing. 

design engineering, and quality meet and outline a plan for fingerprinting actions. One of the first actions is to 

review the literature and past studies performed on the material. The team then obtains several samples of the 

matcrial and submits them for chemical analysis. This involves method development as well as verification of 

techniques previously used. Examples of analytical techniques include FTIR, NMR. HPLC, GPC, ICP, IC, TGA, 

DSC, GCMS, as well as a variety of other methods including mechanical properties. 

Throughout the fingerprinting process a relationship with the material vendor is cultivated. An initial 

contact is made at the start of the fingerprinting process to inform them of the goals and purpose of fingerprinting 

the material. In many cases they have been apprehensive about the degree to which their product is analyzed. 

Often, proprietary agreements are required before they will participate. To facilitate good relations as wcll as to see 

the manufacturing process, the material specialist will visit the manufacturing facility. He normally presents thc 

initial fingerprinting data and discusses the availability as well as the security of our database. Another goal of the 

visit is to inform the vendor of the plans for acceptance testing and discuss their ability to run appropriate tests prior 

to shipping. In addition, discussion of sub-vendors and acceptance criteria of raw materials can be reviewed to 

insure that even subtle changes in the end product will be detected and reported to Thiokol Propulsion. 

The next major hurdle is to organize the data and information gained during the fingerprinting process in a 

user friendly, ready access database. This has been accomplished using several off-the-shelf computer programs 

linked together with a custom PowerBuilder application. It coordinates the fingerprinting information and serves as 

the systems main viewer. There are six interactive pages on the main viewer that include Exccutivc Vicu. Method 

Information, Component Information, Method QC, View Comparison, and Lab Notebook. 

The Executive View Page is the most widely used and gives access to most of the information obtained 

during the fingerprinting process. As can be seen in Figure I. the Executive View page is broken down into several 

different areas. A pull down tab allows you to select the material you wish to look at and once selected a description 

of the material shows up in the second box. The third box lists thc material components and as seen in Figure 2, a 

double click on a component brings up the structure and a few characteristics of the compound. The reference data 

ofthe material and its component parts can be viewed by clicking on the appropriate reference button. Galactic's 

GRAMSI32 software package is used to handle the raw analytical data and is used to show pre-built workbooks 

containing data from the material itself as well as data of its component parts (see Figure 3). Double clicking on the 

appropriate document title in the Reference Material block will access the fingerprinting final report as wcll as other 

previous studies. Where proprietary information is contained on the Executive Viewer page, only those who have 

been given access rights can open the component structures, GRAM932 workbooks. or reference data. 
Figure 1. Executive Viewer 

Figure 2. Component Structure 
Film - ~OMMUABDAlAVlNGERPRlNllNG~D~F~EF_DA-LlMONE SPC 

D-LIMONENE-4LDRICH 97%-4TR snm 9 36 PM R*S = 4 

u 

c4 

n a

g 

2 

n 

- !dr\ J \ 

0 

3500 3330 2500 ZWO 1500 loo0 

Wavenumber (em-I) 

Figure 3. Grams Workbook of PF Degreasor 

The method infonnation page lists the analytical methods developed during the fingerprinting process and 

references written procedures that can be used to duplicate the analysis if future problems should occur. It also 

highlights those procedures that have been selected for acceptance testing in the process control lab. The component 

information page allows our technical personnel to view data on specific tests (see Figure 4). Pull down tabs enable 

the selection of the lab that performed the analysis, the test method of interest as well as the analyte when morc than 

one is available per test method. Analytical data is represented graphically and gives the average as well as the two 

and three standard deviation boundaries. Referencing “Display Values” will bring up the list of numerical values 

used to generate the graph along with sample details such as lot number, etc. The Method QC page enables trend 

analysis of quality control parameters. 
Figure 4. Component Information Page 

The View Comparison page accesscs tivc categories of sample analysis including aging studies. acceptable 

and unacccptablc material as well as developmental data. Grams/'32 workbooks enable users to manipulate and 

overlay data with reference material for direct comparisons. An example of overlaid FTIR data is shown in Figure 

5. 

Figure 5. View Comparison Page 

At Thiokol Propulsion, the fingerprinting database with real-time access has become a valuable problemsolving tool. In the first two years ofthe program we have completed or are currently fingerprinting 37 separate 
critical materials. As the database has expanded it has hccn increasingly useful to resolve manufacturing and 

material down-selection issues. Examples include aging of stockpiled materials, shelf-life discrepancics. 

manufacturing changes, down-selection of ncu materials, and incompatibility issues. 

An excellent example of how fingerprinting has bccn used to resolve issues is the uork done to correct 

solubility problems and extend the in-use life of Bruliii 1990 GD. Since 1997, Brulin 1990 GD has bccn used as a 

concentrate for our Spray-In-Air degreasing facility. Thc concentrate was selected as one of the first materials to be 

fingerprinted. During acceptance testing of the fourth production lot of Brulin 1990 GD, problems of increased 

turbidity and a low pH were identified. This resulted in thc rejection of400 gallons of Brulin 1990 GD. A white 

precipitate, identified as insoluble silicates, was found in the solution. This accounted for the increased turbidity and 

the result was a loss of corrosion inhibitor. It was also noted that the solution had a pH much lower than the 

specification. Based on literature studies it was found the solubility of silicates is directly related to the pH of the 

solution (sce Figure 6). As is noted, the Brulin 1990 GD will form a precipitate when the pH falls close to I I. The 

vendor had verified the pH was between I I .8 and 12.2 prior to shipping but our testing showed the pH to be well 

below I I. 

To resolve the problem, the vendor was contacted and the problem was defined. Initial studies indicated 

that the solutions pH gradually changed over time when exposed to the atmosphere (see Figure 7). To show it was 

caused by the formation and subsequent reaction with carbonic acid, the solution was sainpled to correlate with the 

pH measurement over time. The samples were tested for carbonate by sampling for CO. under acidic conditions and 

as shown therc was a direct correlation between CO? concentration and pH. 

Insoluble Domain 

Monomeric Solutions 

5 6 7 8 9 IO 11 12 13 

PH 

Figure 6. Silicate Solubility 
11.4 - 

11.3 - 

11.2 - 

Q 11.1 - 

11.0 - 

10.9 - 

10.8 - 

10.7 - 

I 

a - Carbon Dioxide 

, 

Figure 7. pH of Brulin 1990 GD with Exposure to Air 

A team ofmaterial specialists was then sent to the manufacturer to present our findings and work out 

methods to stabilize the product. Production was obsened at two different facilities followed by open discussions to 

develop methods that would improve the as received product. Several refinements were made to include the use of 

additional caustic to give the solution a final pH of I 1.5 and the introduction of techniques to insure mix kettle 

cleanliness. Based on these recommendations and implementation of changes to the manufacturing process, we 

have since received five 3000 gallon lots that have met acceptance criteria and no insoluble material has been 

observed. 

Based on the lessons learned from this experience we were able to resolve additional production issues 

related to the use of Brulin 1990 GD. Over a period of eight days at operating temperatures the pH of the solution 

would decrease to levels where the silicates would again begin to precipitate. This created an obvious burden on 

production to replace the 2200 gallons of cleaning solution after such a short period oftime. The material specialists 

resolved this problem by developing a KOH add-back method that maintains the pH at levels that give a reliable 

cleaning solution. This has extended the useful bath life to YO days. 

The chemical fingerprinting program has becn a success story at Thiokol Propulsion. The information 

gained has drastically improved our knowledge ofthc chemistry and baseline profiles of the materials in use. 

Acceptance testing has been updated to use modern and efficient methods and enable better lot-to-lot monitoring. 

When issues do arise. material specialists with technical ownership have a variety of analytical methods in place for 

evaluation and assessment. Resolution is done in minimal time and with increased accuracy. The relationships 

developed with vendors has improved data sharing as wvll as increased the understanding of the acceptance 

requirements in placc for each material. Where possible, testing is transferred directly to the vendor. 
RESOURCES AVAILABLE FOR HAZARDS ANALYSIS OF AEROSPACE FLUIDS' 

Stephen S. Woods 

Honeywell Technology Solutions Inc. 

P.O. Box 20 

Las Cruces, NM 88004 

(505) 524-5607 

[ swoods@wstf.nasa.gov I 

Walter F. Stewart 

L & M Technologies 

Las Cruces, NM 

David L. Baker 

Harold D. Beeson 

NASA Johnson Space Center White Sands Test Facility 

Las Cruces, NM 

INTRODUCTION 

In recent years, the legislative and executive branches of the federal government have pushed to 

make government more efficient and responsive to the needs of the marketplace. One of these 

initiatives, Public Law 104-1 13, also known as the National Technology Transfer and Advancement Act of 

1995 (NTTAA), is designed to accelerate technology transfer to industry and promote governmentindustry partnership. Summarized, NTTAA states that ". . . all Federal agencies and departments shall use 

technical standards that are developed or adopted by voluntary consensus standards bodies, using such 

technical standards as a means to carry out policy objectives or activities determined by the agencies and 

departments."' Government agencies must now determine if their in-house requirement-setting activities 

are sufficiently unique that no public interest is served by having them adopted by a voluntary consensus 

organization (VCO), or if not, to use or develop voluntary consensus standards. The Office of 

Management and Budget (OMB) is chartered by the law to monitor federal agency progress and report 

the results to Congress. 

In response to NTTAA, agency-wide oxygen' and hydrogen3 safety standards sponsored by the 

NASA Headquarters (HQ) Office of Safety and Mission Assurance (OSMA) were obvious choices for 

early adoption by VCOs. In 1996, HQ sought assistance from the Johnson Space Center (JSC) White 

Sands Test Facility (WSTF), the technical lead for development of these safety standards, to evaluate 

their adoption by VCOs. At that time, WSTF-developed propellant hazards manuals were likewise 

identified for possible VCO adoption. Subsequently, WSTF was asked to represent NASA for 

development of an international IS0 safety standard for hydrogen use. Concurrent with these WSTF 

standards activities are related efforts to develop and publish propellant hazards analysis protocols and 

safety courses for the industrial, propellant use of oxygen, hydrogen, and hypergols. 

This paper reports on these efforts and describes WSTF's overall voluntary consensus standards 

program to coordinate the interchange of NASA's propellant hazards and safety information with industry. 

WSTF VOLUNTARY CONSENSUS STANDARDS DEVELOPMENT 

AND TECHNOLOGY TRANSFER PROGRAM 

WSTF has been involved with testing of hazardous fluids, components, and materials for over 

30 years and with the development of hazards manuals during the last 15 years. With this new emphasis 

in direction prompted by NTTAA, the relationship among research and development, hazards analysis 

* Approved for public release; distribution is unlimited. 
protocols, safety course development, voluntary consensus standards activities, and industry 

communications has become apparent. 

A New Environment for CooDeration 

The rapid pace of transfer of government activities to the aerospace industry, along with the 

increasing incidence of aerospace corporate mergers, have the potential for disrupting coordination and 

flow of vital propellant safety and hazards information among personnel involved in design, operations, 

and safety. Within this milieu exist the risks associated with employees’ potential exposure to hazardous 

chemicals in governmental and industrial work environments. The latter has led to detailed regulations 

that specify a highly trained work force, the use of hazards review methodologies, hazards 

communications with employees and the surrounding community, and adequate emergency 

preparedness. How can the effects of these potentially opposed forces be countered? 

One response is for government and industry to cooperate within the framework provided by a VCO, 

which acts as a clearing house for critical information, helps identify top expertise, and offers training. 

The democratic structure of VCOs enables them to develop voluntary consensus standards that meet the 

needs of both government and industry. 

By design, NTTAA has prompted a new, more cooperative environment between government and 

industry that accelerates technology transfer to industry and promotes government-industry partnership. 

But technology transfer from government to industry involves more than simply relaying scientific data 

and technology development. It also involves sharing hazards review and training expertise and making 

the information and techniques used by government laboratories more accessible to industry and the 

public. Technology transfer activities also drive government efforts to be more attuned to industry needs. 

An Enaine for Focused Technoloaical Advancement 

One of WSTF’s primary goals is to support NASA’s propellant safety efforts, which involve testing, 

research and development, and hazards analysis of cryogenic and hypergolic propellants. These 

activities are organized to support queries from industry and the public, to provide training to those who 

need it, and to collaborate with VCOs to develop voluntary consensus standards. Important insights into 

the role hazards analyses can play in the overall direction and planning of safety research have become 

apparent. WSTF is recognized throughout NASA and by the aerospace community for its formalized 

approach to oxygen hazards analysis and has designed protocols for application to hydrogen, hydrazine 

fuels, and nitrogen tetroxide. 

WSTF Hazards Analvsis Protocol 

The protocol works by examining in detail all components exposed to a particular propellant, 

analyzing likely failure modes, determining the consequence(s) of a particular failure to the system, and 

qualitatively assessing the risk for the system owners. The general hazards analysis procedure is 

depicted in Figure 1. Protocols for oxygen and hydrogen have been established, and protocols for 

hypergols are near completion. The protocols address primarily combustion hazards. 

Preliminary activities are to adequately define the application and the scope of the investigation. 

Once defined, an analysis team with expertise in mechanical design, materials, ignition and combustion, 

safety, and component testing as it pertains to the propellant is assembled. Before convening for the 

analysis, detailed information on the components and the system in question is compiled as a skeleton 

report draft that the team fleshes out during the analysis. Thorough preparation at this point cannot be 

overemphasized, for it directly influences the productivity of the analysis. 

The team begins by reviewing the hazards analysis protocol objectives and methodology. An 

overview of system design and operation is then established through review of system and component 

drawings, materials lists, and a failure modes and effects analysis. Operating and worst-case conditions 

are then identified. Component design and function are examined to see if grouping them by failure type, 
failure effect, or subsystem can streamline the analysis. The analysis proceeds for each component or 

subsystem in a given operational mode by identifying the nature of the failure, type of combustible mixture 

formed, potential ignition mechanisms, and whether a flash, fire, or explosion can occur. Also considered 

are design features and administrative controls that may be used. Occurrence probabilities are assessed 

for each of these categories. The scenario posed by a given failure and its potential to result in 

combustion are evaluated to see what secondary effects may result. Assessing the overall risk to the 

actual system or to its intended purpose completes the analysis at this level. The results are documented 

in a summary chart for each component. When necessary, supporting rationale is noted. An example 

summary chart from the hydrogen hazards analysis procedures is shown in Figure 2. 

Analysis scores are determined by team consensus and are tallied through a qualitative rating 

scheme that relies heavily on existing databases. Where data are insufficient to define the hazards, then 

a recommendation for testing is made. Quantitative analysis, personal experience, and intuition are also 

a vital part of the decision-making process. 

The rating scheme, used in the assessment of the probability of failure, formation of combustible 

mixtures, potential for ignition, and the resulting consequences, is based on a qualitative probability rating 

of 0 through 4, with the following identification: 

0 Almost impossible (0), 

0 Remotely possible (I), 

0 Possible (2), 

0 Probable (3), or 

0 Highly probable (4). 

The secondary effects category is assigned an “R when additional analysis is required; otherwise “N” for 

“No further analysis required” is noted. To describe the overall risk arising from component failure, the 

reaction effects category is scored as: 

0 Negligible (A), 

0 Marginal (B), 

0 Critical (C), or 

0 Catastrophic (D). 

The results tabulated in each step are read as independent assessments of probability rather than as 

interrelated. Analysis places failure of an individual component not only in the context of its function in 

the subsystem or system but also its functional environment. When necessary, the interaction among 

components may be evaluated in a matrix fashion. Analysis may also be driven by fault-level 

requirements. The final risk assessment given for reaction effects is not read as a result derived by 

“multiplying” the probabilities assessed in Steps 2 through 5 of Figure 2. Rather, it is an assessment of 

the overall effect on personnel, the system, or its mission caused by the particular failure mode of the 

component under consideration, regardless of the probability. 

The analysis proceeds through all the components. Recommendations are recorded as they become 

apparent from the analysis. During team deliberations the analysis, supporting rationale, and 

recommendations are recorded into the skeleton draft report by a team member acting as “secretary,” 

with the objective of having a draft report when the team is finished. After review of this draft report, a 

final report is prepared for the system owners. Where needed, the report provides recommendations for 

testing, component redesign, materials replacement, and the identification of procedural controls. The 

risks identified in the hazards analysis are then available for appropriate upper management review 

teams. 
The Hazards Analysis Protocol as the Encline for Technoloav Transfer 

Successful technology transfer requires placing critical information where it is needed. While this 

sounds obvious, the challenge is in identifying what information is critical and then knowing how to get it 

to those who need it. 

In its traditional role, the hazards analysis protocol is used by project- and program-oriented groups 

as a means of identifying and remediating potential component and system inadequacies. But 

sometimes during the course of an analysis, a need arises for data that do not exist. For example, in the 

assessment of propellant hazards, this may involve the need for combustion or materials data that are not 

currently available but can be gained through testing. But if the team determines that testing is too 

difficult or expensive, the analysis might prompt a system redesign, the acceptance of greater risk, or a 

new method for assessing the hazards. 

Unfortunately, the information obtained from the hazards analysis and how to apply it is often 

perceived as so specialized that little is done other than basic documentation of the analysis. End-users 

perceive that only those involved could promote further use of the data, which may or may not be true. 

Given this, how can hazards analysis protocols figure both in the promotion of technology transfer and 

technology development? 

The hazards analysis process is by nature dynamic and points out what is known and what is not. 

The results of this process can be used to identify new research, problem areas, operational issues, or 

training requirements and should be considered prime information for technology transfer. When this 

knowledge is acted upon, perhaps by obtaining new data through testing, the results are state-of-the-art 

information. Typically the information is efficiently obtained because it results from the already-funded 

process of the hazards analysis. In a proactive environment, hazards analysis information can be used to 

propose new research to cover the deficits of data uncovered by the process. This information can 

prompt a refinement of hazards analysis techniques, which can then point toward improvements of the 

protocols. Another benefit is that the information is developed by industry expertise and can be applied 

directly to industry development as specific solutions and recommendations. Finally, publishing the 

information in the open literature makes it accessible to a wide audience that may be able to take 

advantage of it without “reinventing the wheel” and incurring the cost of unnecessary testing. 

There are implications for use of this information beyond immediate aerospace applications. Such 

information is not only important in the technical development of a system; it can also be critical in the 

acceptance of the technology. For example, systems developed by the commercial sector that will be 

used by the public must be perceived as safe before investors can obtain the insurance to cover venture 

capital. One area of current development in which this is true is the application of hydrogen fuel cells to 

everyday applications. Also, it is acknowledged that the use and protection of proprietary information will 

always be a sensitive issue. 

How might hazards analysis information be gathered and distributed? There are “lessons learned” 

databases and compilations of data on accident investigations currently available, but they appear to be 

static compilations that are periodically updated. It is hoped that the information gathered through 

hazards analyses would be the focus of an established group. WSTF currently serves that function, but 

given the current emphasis on VCOs, the activity could be managed by a VCO as well, with appropriate 

input from industry and government. The VCO’s objective would be to compile and analyze the findings 

of recently completed hazards analyses, then help distribute the results. 

Consensus as a Means of Communication 

Easily leveled criticisms of standards efforts conducted within government agencies are that the 

results are inadequate, one-sided, and inaccessible. The NTTAA has forced government to reevaluate its 

standards efforts. But for NASA, an agency that has always been proactive with regard to public 

outreach and technology transfer, NTTAA provides the basis for even greater interaction with industry 

and the public. 
Aside from the primary goal of managing standards through a VCO, other positive attributes should 

arise from pursuit of the law. These include improved communication within government agencies and 

between industrial entities as well as interagencyhnterindustry connections. This has the potential to 

bring different interests together and lead to the establishment of a common ground in which research 

and development can take root. But it is likely that VCOs will continue to be a focal point for general 

information related to voluntary consensus standards, such as identifying where particular expertise can 

be found. 

NASA’s interest in participation with VCOs in the safety arena includes transfer of hazards manuals 

and the development of voluntary consensus standards. In theory, hazards information is better 

distributed by VCOs, with the cost being covered by the program interests that need the information 

rather than subsidized by the government. One goal is to promote the creation of general safety 

standards for propellant use that can be applied in government-industry contract negotiations. 

For agencies that are not proactive in response to NTTAA, it will be interesting to see how the law will 

work in the future. The OM6 requires federal agencies to report on the status of their efforts to meet the 

law. Already the mobile home construction industry has brought a legal challenge4 against legislation 

pending in Congress, the American Homeownership and Opportunity Act, H.R. 1776, citing conflicts with 

NTTAA. Here industry is claiming that preexisting law directs them through VCOs to keep standards for 

manufactured homes up-to-date and the new law is not needed. 

Interrelationship Amonu Hazards Analvsis, Consensus Communications, and Research 

The hazards analysis process is depicted at the center of the technology transfer process shown in 

Figure 3. The information gained by hazards analyses can serve as input to VCOs, for research, and for 

training. Conversely, VCO committees, research groups, and trainers can have influence on hazards 

analysis protocols. For this scheme to function effectively, some group in industry or government must 

have a vested interest in tracking, documenting, and communicating key information obtained from the 

use of hazards analysis protocols. At present WSTF is funded to do this work. A logical extension of who 

performs this sort of work would include the VCOs themselves. 

SPECIFIC ACHIEVEMENTS 

WSTF’s parallel efforts to promote safety research and safety standards development are a vital part 

of its mission. The next section outlines the specific achievements by these efforts. 

Propellant Oxvqen 

Research into propellant oxygen hazards has been ongoing at WSTF since the mid-1970s and is its 

most mature expression of the interrelationship among research, hazards analysis, and VCO 

participation. Technical communications and technology transfer with industry are achieved through a 

long-standing participation with ASTM Committee G4 on Compatibility and Sensitivity of Materials in 

Oxygen Enriched Atmospheres and the National Fire Protection Association’s committees on Health 

Standards and Hyperbaric Standards. The oxygen hazards analysis protocol has been in use for over a 

decade. WSTF researchers have developed an oxygen safety training course, “Fire Hazards in Oxygen 

 system^,"^ that is offered through ASTM. At the request of the NASA HQ/OSMA, WSTF developed a 

safety standard for oxygen and subse uently collaborated with ASTM to publish it as Manual 36, “Safe 

Use of Oxygen and Oxygen Systems.’ WSTF’s progress in the oxygen arena serves as a model for its 

development of hydrogen and hypergol propellant programs. The following documents and courses are 

available for oxygen safety assessment: 

0 

0 

0 

0 

0 

NASA Safety Standard 1740.1 5, “Safety Standard for Oxygen and Oxygen Systems” 

ASTM MNL36, “Safe Use of Oxygen and Oxygen Systems” 

NASA Technical Memorandum 104823,7 Guide for Oxygen Hazards Analyses on 

Components and Systems” 

ASTM G63, “Guide for Evaluating Nonmetallic Materials for Oxygen”’ 

ASTM G88, “Guide for Designing Systems for Oxygen Servi~e”~ 
0 

0 

ASTM G94, “Guide for Evaluating Metals for Oxygen Service”” 

NFPA 53, “Recommended Practice in Oxygen-Enriched Atmospheres”” 

ASTM Technical and Professional Training Course, “Fire Hazards in Oxygen Systems” 

(several versions exist that are tailored to particular audiences, such as design engineers, 

technicians, and the scuba community) 

ASTM Technical and Professional Training Course, “Oxygen Systems: Operation and 

Maintenance” 

0 

Propellant Hvdroaen 

Progress in the hydrogen safety arena includes development of the NASA Safety Standard for 

Hydrogen and Hydrogen Systems and collaboration with the American Institute of Aeronautics and 

Astronautics (AIAA) toward the formation of an aerospace hydrogen safety committee. This hydrogen 

safety committee will oversee the development of a consensus guide based on the NASA hydrogen 

safety standard and ultimately the development of a national standard. NASA has been invited to help 

represent U.S. interests in the international hydrogen safety community. In parallel with the AlAA effort, 

WSTF supports IS0 Technical Committee 197, Working Group 7 on general hydrogen safety. Following 

the model of oxygen activities, a hydrogen hazards analysis protocol and a hydrogen safety training 

course have been developed. The hydrogen safety training course is available through the NASA Safety 

Training Center. The hydrogen hazards analysis protocol is available from WSTF. The following 

documents and courses are available for hydrogen safety assessment: 

0 

0 

0 

0 

NASA Safety Standard 1740.1 6, “Safety Standard for Hydrogen and Hydrogen Systems” 

TP-WSTF-937,12 “Guide for Hydrogen Hazards Analysis on Components and Systems” 

RD-WSTF-0001 ,13 “Ignition and Thermal Hazards of Selected Aerospace Fluids” 

NASA Safety Training Center, Course 037, “Hydrogen Safety” 

HvDeraolic Fuels and Oxidizers 

Progress in the hypergol safety arena parallels WSTF’s oxygen and hydrogen efforts in that several 

manuals covering the hazards of hypergolic propellants have been developed. This is just the kind of 

information that could better serve the aerospace community if it was managed by a VCO. In 

collaboration with AIM, WSTF has promoted the formation of the recently initiated AlAA Liquid Propellant 

Committee on Standards to serve as a forum for discussion of hypergolic and related propellant safety 

issues. This committee has an agenda to oversee the development of voluntary consensus standards 

covering hydrazine, monomethylhydrazine, dinitrogen tetroxide, and other aerospace fluids of interest. 

WSTF hypergolic hazards manuals have been transferred to AlAA for distribution as AlAA Special 

Projects. The agreement stipulates that needed updates of hypergolic hazards information will be 

published through AlAA Special Projects or Guides. In addition to the AIM committee work, JSC has 

funded development of a hazards analysis protocol for hypergolic propellants. Also, NASA HQlOSMA 

has funded WSTF for development of a hypergol safety training course. Both these efforts are in 

progress and the results will be available in fiscal year 2001. The following documents and courses are 

available for hypergolic safety assessment: 

0 

0 

0 

0 

0 

0 

0 

e 

RD-WSTF-0001, “Ignition and Thermal Hazards of Selected Aerospace Fluids” 

RD-WSTF-0002,14 “Fire, Explosion, Compatibility, and Safety Hazards of Hydrazine” 

RD-WSTF-0003,’5 “Fire, Explosion, Compatibility, and Safety Hazards of 

Monomethyl hydrazine” 

RD-WSTF-001 7,16 ”Fire, Explosion, Compatibility, and Safety Hazards of Nitrogen Tetroxide” 

AlAA SP-084-1999,17 ”Fire, Explosion, Compatibility, and Safety Hazards of Hypergols - Hydrazine” 

AlAA SP-O85-1999,’* “Fire, Explosion, Compatibility, and Safety Hazards of Hypergols - Monometh ylhydrazine” 

TP-WSTF-953,” “Guide for Hydrazine Hazards Analysis on Components and Systems” 

TP-WSTF-959,” “Guide for Nitrogen Tetroxide Hazards Analysis on Components and 

Systems” 
0 NASA Safety Training Center, Course 040, “Hypergolic Propellant Safety” 

SUMMARY AND CONCLUSIONS 

The goal of the paper has been to inform aerospace researchers and engineers of new resources 

and an improved way of approaching and communicating propellant safety concerns and to raise 

awareness regarding NTTAA. The nexus of propellant activities for oxygen, hydrogen, and hypergol 

safety underway at WSTF can aid researchers with locating critical information, expertise, testing 

services, and training. The authors encourage those who have a stake in making this kind of information 

available to their own organization to participate in VCO activities, such as the ASTM Committee G4 and 

the AlAA Liquid Propellant Committee on Standards. For hydrogen, readers are encouraged to contact 

AIAA and/or the WSTF propellant hazards program for further information. 

Another goal of this paper is to recommend that the aerospace community reevaluate how the results 

of hazards analyses are conveyed beyond an immediate project or program. It is important that a 

mechanism exist to organize and convey this information. Specific recommendations for oxygen, 

hydrogen, and hypergol safety are: 

0 

0 

0 

Examine how your own organization treats the results of hazards analyses after specific 

project or program needs have been satisfied. 

Consult the WSTF propellant hazards programs, which have a strong history as contact 

points for coordinating and organizing hazards information. 

Seek participation in an appropriate VCO to organize and disseminate hazards analysis 

results. 

The NTTAA has pointed the way for a reconsideration in the way government and industry interact. 

For the maximum benefit to accrue in the propellant safety arena, industry and government 

representatives must participate through the technical committees of the VCOs chartered to manage this 

information. 

REFERENCES 

1. Public Law 104-1 13 ( 104‘h Congress). National Technology Transfer and Advancement Act of 7995. 

15 USC 3701. Washington, D.C. Signed by the President, March 7, 1996. 

2. NASA Office of Safety and Mission Assurance. Safety Standard for Oxygen and Oxygen Systems 

(Guidelines for Oxygen System Design, Materials Selection, Operation, Storage, and 

Transportation). NSS 1740.1 5, Office of Safety and Mission Assurance, Washington, D.C., 

January 1996. 

3. NASA Office of Safety and Mission Assurance. Safety Standard for Hydrogen and Hydrogen 

Systems (Guidelines for Hydrogen System Design, Materials Selection, Operations, Storage, and 

Transportation). NSS 1740.1 6, Office of Safety and Mission Assurance, Washington, D.C., 

February 1997. 

4. ASME. ASME Letter to the Honorable Constance A. Morella Regarding the Proposed Manufactured 

Housing Improvement Act. American Society of Mechanical Engineers, New York, NY, Feb. 11, 

2000. htt~://w.asme.or~/~r~c/OO-O2.html. 

5. “Fire Hazards in Oxygen Systems,” Technical & Professional Training Course, American Society for 

Testing and Materials, West Conshohocken, PA, latest version. 

6. Beeson, H. D., W. F. Stewart, and S. S. Woods, Eds., “Safe Use of Oxygen and Oxygen Systems: 

Guidelines for Oxygen System Design, Materials Selection, Operations, Storage, and 

Transportation,” ASTM MNL36, American Society for Testing and Materials, West 

Conshohocken, PA, January 2000. 
7. Stoltzfus, J. M., J. Dees, and R. F. Poe. Guide for Oxygen Hazards Analyses on Components and 

Systems. NASA Technical Memorandum 104823, Johnson Space Center, Houston, TX, October 

1996. 

8. ASTM G 63. Standard Guide for Evaluating Nonmetallic Materials for Oxygen Service. Annual Book 

of ASTM Standards, American Society for Testing Materials, Philadelphia, PA (1992, or latest 

revision). 

9. ASTM G 88. Standard Guide for Designing Systems for Oxygen Service. Annual Book of ASTM 

Standards, American Society for Testing Materials, Philadelphia, PA (1990, or latest revision). 

IO. ASTM G 94. Standard Guide for Evaluating Metals for Oxygen Service. Annual Book of ASTM 

Standards, American Society for Testing Materials, Philadelphia, PA (1992, or latest revision). 

11. NFPA 53. Recommended Practice on Materials, Equipment, and Systems Used in Oxygen-Enriched 

Atmospheres. National Fire Protection Association, Quincy, MA (1 999, or latest revision). 

12. Woods, S. S., G. Packard, and H. D. Beeson. Guide for Hydrogen Hazards Analysis on Components 

and Systems. TP-WSTF-937, NASA Johnson Space Center White Sands Test Facility, Las 

Cruces, NM, August 19,1998. 

13. Benz, F. J., C. V. Bishop, and M. D. Pedley. Ignition and Thermal Hazards of Selected Aerospace 

Fluids. RD-WSTF-0001, NASA Johnson Space Center White Sands Test Facility, Las Cruces, 

NM, October 14, 1988. 

14 Pedley, M. D., D. L. Baker, H. D. Beeson, R. C. Wedlich, F. J. Benz, R. L. Bunker, and N. B. Martin. 

Fire, Explosion, Compatibility, and Safety Hazards of Hydrazine. RD-WSTF-0002, NASA 

Johnson Space Center White Sands Test Facility, Las Cruces, NM, February 20, 1990. 

15. Woods, S. S., D. B. Wilson, R. L. Bunker, D. L. Baker, and N. B. Martin. Fire, Explosion, 

Compatibility, and Safety Hazards of Monomethylhydrazine. RD-WSTF-0003, NASA Johnson 

Space Center White Sands Test Facility, Las Cruces, NM, May 5,1993. 

16. Davis, D. D., D. L. Baker, L. A. Dee, B. Greene, C. H. Hart, and S. S. Woods. Fire, Explosion, 

Compatibility, and Safety Hazards of Nitrogen Tetroxide. RD-WSTF-0017, NASA Johnson Space 

Center White Sands Test Facility, Las Cruces, NM, November 15, 1999. 

17. AlAA SP-084-1999. Fire, Explosion, Compatibility, and Safety Hazards of 

Hypergols - Hydrazine. American Institute of Aeronautics and Astronautics, Reston, VA, 1999. 

18. AlAA SP-085-1999. Fire, Explosion, Compatibility, and Safety Hazards of Hypergols - 

Monomethylhydrazine. American Institute of Aeronautics and Astronautics, Reston, VA, 1999. 

19. Rathgeber, K. A., L. J. Bamford, and D. L. Baker. Guide for Hydrazine Hazards Analysis on 

Components and Systems. TP-WSTF-953, NASA Johnson Space Center White Sands Test 

Facility, Las Cruces, NM, May 4, 2000. 

20. Rathgeber, K. A., L. J. Bamford, and 0. L. Baker. Guide for Nitrogen Tetroxide Hazards Analysis on 

Components and Systems. TP-WSTF-959, NASA Johnson Space Center White Sands Test 

Facility, Las Cruces, NM, publication in process. 
I Define Application I 

Define Scope of Analysis 

Assemble Hazards Analysis Team 

I 

Compile ComponentEystem Information 

1 Identify Operating & Worst-case Conditions 1 

I Evaluate Potential Failure Causes I 

T Determine Probability of Failure 

I Noncatastrophic Catastrophic I I 

Determine Probability of Exposure 

I Personnel Materials Environment I 

I Determine Secondarv ExDosure Effects I 

[ Determine Probability of Flammable Mixture 1 

Determine Probability of Ignition 1 

From these Sources 

I J ~ ~ ~~~ ~~ ~ ~ ~ ~ ~ ~ ~~ ~ ~ 

Electrical Mechanical Thermal Material 

Determine Probability of these 1 

L Consequences 

I Flash Fire Explosion I 

L Assess Reaction Effects 

I Equipment MissionlObjective Personnel 

Figure 1. Procedure for General Hazards Analysis 
Chemical Fingerprinting of Materials Developed Due to Environmental Issues 

Doris A. Smith. Lockheed Martin Space Systems. P.O. Box 29304, New Orleans, LA 70189. (504) 257-0228 

I doris.smithk$maf.nasa.gov I 

Abstract 

Instrumental chemical analysis methods are developed and used to chemically fingerprint new and 

modified External Tank materials made necessary by changing environmental requirements. Chemical 

fingerprinting can detect and diagnose variations in material composition. To chemically characterize each material. 

fingerprint methods are selected from an extensive toolbox based on the material’s chemistry and the ability of the 

specific methods to detect the material‘s critical ingredients. Fingerprint methods have been developed for a variety 

of materials including Thermal Protection System foams. adhesives. primers, and composites. 

Introduction 

Some of the materials used in the Space Shuttle External Tank have been or will be replaced or modified 

due to environmental restrictions impacting the availabilit).. of raw materials. For example. External Tank Thermal 

Protection System (TPS) urethane foams originally containing CFC- 1 1 blowing agent have been replaced with 

foams containing HCFC-141b blowing agent. Materials such as the TPS foams are critical to the performance of 

External Tanh and. therefore. must be adequately tested to ensure that materials variations are detected before the 

material is used. Material variations can be due to a number of occurrences such as formulation changes. ingredient 

substitutions, material degradation, contamination. and mislabeling. A material can be simple such as a solvent, or 

complex such as a urethane foam that contains multiple ingredients (blowing agent, polyols. flame retardants, 

catalysts. surfactant) that in turn contain multiple ingredients. 

Traditional tests used to characterize materials can be grouped into several categories. Traditional wet 

chemical tests are based on titrimetric or gravimetric procedures and include tests such the hydroxyl number test for 

reactive poI>ol and the amine equivalent test for reactive isocyanate groups in urethane foam formulations. Physical 

property tests include viscosiD . specific gravity. color. haze. and particle size measurements. Mechanical property 

tests include compressive strength, tensile strength. and hardness measurements. Although the traditional tests are 

extremely valuable and may indicate the presence of material variations. traditional tests alone cannot identify the 

exact nature and origin of the variation. Instrumental chemical analysis or chemical fingerprinting can both detect 

and diagnostically identifi variations in chemical composition. 

Chemical Fingerprinting Techniques 

Chemical fingerprinting techniques most frequently used to characterize materials used on the External 

Tanli program are identified in Table 1. These techniques are used to qualitatively (What’s there?) or quantitatively 

(How much is there?) characterize materials. 

Spectroscopic techniques are based on the interaction between light (electromagnetic radiation) and matter 

and are used to obtain information about elemental or molecular composition. Elements or compounds within a 

sample absorb or emit light of specific energy and intensity. The energy of the emitted or absorbed light (measured 

as a frequency or wavelength) is used to identifj. the elements or compounds present. The intensity of the emitted or 

absorbed light is related to the amount or concentration of the detected component. Spectroscopic techniques most 

commonly used are of two types: techniques that are used to identify elements present (examples: atomic emission. 

atomic absorption. and x-ray fluorescence spectroscopy) and techniques that are used to identifi molecular 

compounds present (examples: infrared and Raman spectroscopy. mass spectrometry). 

In a chromatographic procedure, the sample is dissolved or dispersed in a mobile phase. then passed 

through a column containing a stationary phase. Components within the sample are separated from one another 

based on the relative affinity of the components for the stationary phase. The mobile phase is either a gas (gas 

chromatography) or a liquid (high performance liquid chromatography. ion chromatography. gel permeation 

chromatography). Ln gas chromatography separated components are most often detected as changes in thermal 

conductivity or flame ionization current, whereas in liquid chromatography the separated components are usually 

detected as changes in ultraviolet absorption, refractive index. or conductivity. 
Atomic Absorption 

Spectroscopy 

lnductively Coupled Plasma 

Atomic Emission Spectroscop! 

(ICP/AES) 

X-ray Fluorescence 

Spectroscopy 

(XW 

Infrared Spectroscopy 

(IR or FTIR) 

Raman Spectroscopy !----- 

High Performance Liquid 

Chromatography (HPLC) 

Ion Chromatography (IC) 

Gel Permeation 

Chromatography (GPC) 

ApplicationsiAdvantages 

Elemental quantitative analysis 

Rapid analysis of single element 

High sensitkit!. for some elements 

Inexpensive 

Simultaneous multi-element analysis 

Large linear response range 

Better than AA for refractory mat's 

All elements of atomic number 2 11 

Minimal sample preparation 

Applicable to solids and liquids 

Inexpensive 

Molecular identification 

Functional group identification 

Applicable to solids, liquids. gases 

Minimal sample preparation 

Extensive reference spectra libraries 

Inexpensive 

Molecular identification 

Functional group identification 

Applicable to solids, liquids 

Applicable to aqueous solutions 

Minimal sample preparation 

Identification of organic compounds 

Widely applicable to volatiles 

Extensive reference suectra libraries 

Separation of multi-componenl 

mixtures of volatile compounds for 

quantitative analysis or for 

identification by tandem techniques 

Selectivity general or specific 

Inexnensive 

Separation of multi-componeni 

mixtures of soluble compounds for 

quantitative analysis or for 

identification bv tandem techniaues 

Separation of complex mixtures of 

ionic species for quantitative analysis 

Applicable to organic and inorganic 

More sensitive than wet methods 

Separation of complex mixtures 

based on molecular size 

Determination of molecular weight 

Limitations/Disadvantages 

Not applicable to most nonmetal elements 

Small linear response range 

High matrix interference 

Solution usually required 

Sample preparation time consuming 

Special accessory required for solids 

Limited sensitivity to nonmetals 

Solution usually required 

Sample preparation time consuming 

Special accessory required for solids 

Expensive 

Not applicable to elements of atomic 

number < 11 without modifications 

Minor components masked by major 

Molecule must undergo dipole momenl 

change during vibration 

Not applicable to highl), colored samples 

and samples that fluorescence 

Limited reference spectra libraries 

Molecule must undergo polarizabilit? 

change during vibration 

Espensijte 

Special sample introduction required for 

non-volatile samples 

Expensive 

Not applicable to non-volatile compounds 

Ivithout derivatization 

Not applicable to thermally unstable 

materials 

Method development time-consuming 

Sample must be soluble in suitable solvent 

Large volume of waste solvent 

Moderatelv exuensive 

Method development time-consuming 

Moderately expensive 

Sample must be soluble in suitable solvent 

Large volume of waste solvent 

GPC columns expensive 
Applications of Chemical Fingerprintin9 to Simple and Comdex Materials 

The chemical fingerprint techniques listed in Table 1 are not all used for each material. Instead, a 

combination of techniques is selected based on the material's chemical composition and its physical properties. One 

or two techniques may be sufficient to adequately identify and monitor the composition of a relatively simple 

material, while a combination of several techniques may be required for more complex materials. 

An example of a simple material is the solvent HCFC-225, which is a mixture of two isomers. HCFC73ca and HCFC-225cb. Gas chromatography readily separates the two isomers from one another and from low 

concentration impurities. This technique is used to measure the percent purity of the HCFC-225 and to measure the 

ratio of the two isomers. Gas chromatography is also used to measure the percent purity of HCFC-225G. which is 

composed predominantly of the HCFC-225cb isomer. 

Urethane foams comprising the External Tank Thermal Protection System (TPS) are examples of complex 

materials that cannot be totally characterized by a single fingerprint technique. Several TPS foam materials 

containing CFC-11 as blowing agent were modified or replaced by materials containing HCFC-14lb. These 

materials are received as two liquid components. One of the components contains methylene diphenylene 

diisocyanate (MDI) and its oligomers and is frequently referred to as Component A. The other component. 

frequently called Component B. may be a complex mixture of polymeric alcohol (polyols), flame retarding 

ingredients. blowing agents. catalysts. and surfactants. Ingredients may be in the formulation at widely different 

concentrations ranging from less than one percent to up to nearly seventy percent by weight. More than one of each 

gpe of ingredient may be present. and ingredients themselves mal be multi-component. In addition, the ingredients 

are very different from one another chemically and therefore require the use of different fingerprinting techniques. 

To completely characterize the material. a combination of techniques capable of detecting each Ley ingredient in the 

formulated material must be identified 

The combination of fingerprinting techniques that may be required to characterize a complex urethane 

formulation is presented in Table 2. The goal of the fingerprinting program is to identify and develop a group of 

techniques that adequately and efficiently characterizes the material. Often, a single procedure can target several 

ingredients. For example, an inductively coupled plasma atomic emission spectroscopic (ICP/AES) procedure can 

be used to measure concentrations of elements such as phosphorus present in flame retardants, silicon present in 

silicone surfactants. and metals such as tin, lead, or potassium present in catalysts. On the other hand, an ingredient 

that is both present at a low concentration and inherently difficult to detect due to its chemistry may necessitate the 

development of a procedure that targets that ingredient alone. Examples include a low concentration amine catalyst 

that requires a gas chromatographic procedure with a specialized nitrogen-phosphorus detector (NPD) or low 

concentration bromine-containing flame retarding compound that requires a special high performance liquid 

chromatographic (HPLC) procedure. 
SupDlier Partnershiu 

Partnership with our suppliers is a key component in our fingerprinting program. Important steps in 

developing fingerprint methods for a given material are identifying the formulation ingredients and understanding 

each ingredient's role in the formulation. In some cases. ingredients are identified in the Material Safety Data Sheet 

or in other easily obtained documents. When the material is a simple mixture of relatively simple ingredients. 

fingerprint analysis may readily identi@ ingredients. However, in most cases. especially when materials are 

composed of complex mixtures of complex ingredients, the supplier's cooperation is needed. For the most part. our 

suppliers have been willing to identi@ the ingredients in their materials. to disclose ingredient concentrations. and to 

provide samples of ingredients. By 

fingerprinting a material's ingredients. the peaks in the material's cllromatograms and spectra can be assigned to 

individual ingredients, and changes in the material's fingerprint can be readily attributed to specific ingredients. 

When material problems arise, fingerprinting data can be relayed back to the supplier in order to expedite resolution 

of the problem. Supplier partnership is based on the understanding that formulation information will be used only 

to better understand the material's chemistry and to develop methods to ensure material consistency, and that 

proprietary information will not be disclosed without the supplier's agreement. 

This cooperation has greatly expedited fingerprint method development. 

Fingemrint Databases 

Fingerprinting of a material yields data that is compiled into a quantitative database for that material. 

Fingerprint databases provide a baseline reference that are used to detect and identifq lot-to-lot variations in 

composition that may be due to formulation changes, material degradation. or contamination. When a sufficient 

number of lots have been fingerprinted. the database is used to select fingerprint methods for implementation as 

receiving/acceptance tests and to establish receivingiacceptance ranges. Fingerprint methods and databases are also 

used to support material failure investigations. new material development, alternate material qualification. new 

supplier qualification. new manufacturing location qualification, and material shelf-life investigations. 

Fingerprint databases provide a reservoir of data that can be used to generate control charts. Through the 

use of control charts. shifts or trends in material parameters can be detected early, before the material fails to meet 

specification. 

Acknowledgements 

Tammy Bourgeois, Mary Capezza, Emile Evans. Debbie Pierce. Laurie Rando. and Lance Spiers have made major 

contributions to the chemical fingerprinting program. Mary Capezza's support with this presentation is greatly 

appreciated. 
L'se ofGC:MS and hlicrotome Techniques as Methods to Evaluate ODC Free Cleaner Diffusion and 

Evaporation in lnsulation and Phenolic Case Material ' 

L.L. Biegert 

Cordant Technology: Thiokol Propulsion 

P.O. Box 707 

Brigham City, Utah 84302-0707 

(4-451 -- Xh? 195R 

Biegell@Thiokol.com 

5 

ABSTRACT 

Because of the 1990 Clean Air Act Amendment (CAAA) many chlorinated solvents used in the 

aerospace industry are being phased out. Replacement of the ODC (ozone-depleting chemicals) with less 

volatile, non-ozone depleting cleaners has been extensively studied over the past seven years at Thiokol 

Propulsion. a Division of Cordant Technologies, Inc. 

The down selection of ODC replacement cleaners has been based on several factors including the 

diffusiom evaporation of the cleaners in selected substrates. Methodologies were developed to evaluate the 

cleaner content in substrates. Methods of cutting thin slices of material (microtoming) were combined 

with GC'MS (gas chromatography/ mass spectroscopy) analysis. 

Substrates evaluated in this study include potential solid rocket motor materials: ASNBR 

(asbestos-filled nitrile butadiene rubber) and CFEPDM (carbon-filled ethylene propylene dimonomer) 

insulation and glass (GCP). carbon (CCP) and silica (SCP) cloth phenolic substrates with fibers either 

parallel (0") or perpendicular (90") to the surface. Residue profiles indicate both cleaner and substrate 

composition atfect the diffusion and subsequent evaporation of the cleaner from the substrate surface. 

INTRODUCTION 

Federal air regulations under the 1990 Clean Air Act Amendment (CAAA) has presented a big 

challenge and cost impact to the aerospace industry by phasing out the use of Class I and 11 ozonedepleting chemicals and substances. TCA ( 1, I, I -trichloroethane), a chlorinated solvent used at Thiokol 

Propulsion a division of Cordant Technology, is targeted by this clean air amendment. Alternate cleaners 

must be qualified before depletion of the TCA stockpile and/or before the TCA "essential use" waiver 

ex pi res. 

Over the past seven years ODC replacement cleaners have been evaluated for safety, solubility. 

compatibility. cleaning efficiency, effects on subsequent bond strength and substrate integrity. 

Development of discriminating methods to screen cleaners has been an important feature in the selection 

process to replace TCA. The combined use of GCiMS analysis and microtome cutting has been developed 

to obtain cleaner residue profiles in substrates that will be hand cleaned with the new cleaner. This 

infbrmation can be further combined with mechanical properties (tensile and shear information) to 

determine the detrimental effect of the cleaner on Substrate properties or subsequent bonding. 

K' 1000 Thiokol Propulsion. a Division of Cordant Technologies, Inc. 

' This work was performed under contract NAS8-38100 as part of NASA's ODC Cleaner TCA 

Replacement Program. 
EXPERIMENTAL 

Cleaner 

Trichloroethane 

Bioact PCG 

PF Degreaser 

Six types of cloth phenolic coupons (I-inch by 2-inches) were used in this study. They include 

glass cloth phenolic (GCP), silica cloth phenolic (SCP) and carbon cloth phenolic (CCP). Fibers in these 

coupons were wound either perpendicular (90”) or parallel (0”) to the cleaner exposed surface. Two types of 

motor insulation coupons were also evaluated and include the ASNBR (asbestos-filled nitrile butadiene 

rubber) and the CFEPDM (carbon-filled ethylene propylene dimonorner) rubbers. 

Abbreviation Chemical Description 

TCA 1,l ,I -trichloroethane 

PCG Limonene (> 980//0) 

PFD Limonene (8%). BHT (inhibitor), 

Hydrocarbons (92%) 

Coupons (one- by two- inch) of either cloth phenolic or cured insulation were secondarily bonded 

onto a stage that was clamped into the microtome apparatus. For the insulation. a manual microtome 

instrument was used to cut slices from the surface at approximately 0.4-mm. The hardness of the cloth 

phenolic prevented manual microtoming and the samples were cut automatically using an instrument that 

cuts slices approximately 0. I -mm thick from the surface. 

Three cleaners were evaluated in this study. The baseline solvent. I ,I ,I-trichloroethane (TCA) 

was included to compare with the new cleaners under evaluation. Bioact PCG has been extensively 

evaluated in several of the work areas and represents a cleaner that contains limonene. Many of the other 

cleaners evaluated at Thiokol also contain limonene and thus the diffusion and evaporation of. this 

component from motor substrates is important. The cleaner PFD was also included since this material not 

only contained limonene but also a mixture of hydrocarbons. Table I lists the cleaners evaluated in this 

study and their components. 

Rymple cloth was saturated with the appropriate cleaner and the coupon hand wiped with the wet 

cloth. After several passes of the wet cloth on the surface, a dry rymple cloth was used to remove any 

excess cleaner. The coupons were allowed to dry at ambient conditions for a selected number of minutes 

(1.5, 30,45 and 60) prior to removing three slices from the surface. 

Slices of cloth phenolic or cured insulation were placed in glass bottles with rubber septum for 

GCI’MS headspace analysis. Each sample was heated to 1 10°C for approximately twenty minutes then a 

250-pI aliquot of headspace gas was removed for cleaner residue analysis. 

DISCUSSION 

St t ’ 

The diffusionievaporation profiles of the three cleaners in cured ASNBR insulation are shown in 

Figure 1. The TCA residue cleaner profile shows the chlorinated solvent is readily absorbed into the 

ASNBR rubber substrate. Even after 60 minutes dry time the levels of TCA remain relatively high at the 

substrate surface. High values of TCA are also observed at 0.5 mm into the sample. Over time the surface 

levels of TCA remain the same and the levels at 0.5 mm decrease. Two processes are contributing to this 

cleaner profile: evaporation from the surface and diffusion from the bulk substrate. 

The PCG cleaner profile in ASNBR insulation shows a significant loss in substrate cleaner levels 

from 15 minutes to 30 minutes. Relatively little change in cleaner surface levels is observed between 30 

and 60 minutes. The PFD hydrocarbon levels in ASNBR cleaner show this component of the cleaner does 

not penetrate very deep into the substrate and does not evaporate readily from the surface. Nitrile butadiene 

rubber is specifically formulated to resist oil and hydrocarbons and the cleaner profiles that were generated 

in this study support this chemical feature. 
Cleaner profiles in CFEPDM are shown in Figure 2. Similar levels ol' TCA are found in 

CFEPDM in comparison with ASNBR insulation. A significant loss in cleaner surface levels is noted 

between 15 and 30 minutes. Once again the cleaner is observed at fairly significant levels at 0.6 mm into 

the bulk substrate. 

The PCG profile in CFEPDM is significantly different than that observed for ASNBR insulation. 

In CFEPDM, limonene is readily absorbed into the rubber. Limonene levels are almost as high 0.6 mm in 

the substrate as they are on the surface. There is a significant decrease in limonene between IS and 30 

minutes of ambient drying. however, there is little change in cleaner levels up to 60 minutes. 

The PFD cleaner profiles in CFEPDM are also significantly different in comparison with ASNBR 

Very insulation profiles. Like PCG, the hydrocarbons in PFD are readily absorbed into the CFEPDM. 

high lebels of cleaner are observed at 0.6 mm even after a 60 minutes ambient temperature dry. 

Cloth Pwic Substrate2 

The cleaner evapordtioddiffusion profiles in carbon cloth phenolic (CCP) coupons are shown in 

Figure 3. Very little cleaner (TCA or PCG) is observed on the surface with no sequential decrease in 

cleaner residue observed over a 60 minute dry. Variability due to hand wiping appears to be geater than 

the evaporation of the cleaner. 

PFD has the highest surface residue of the three cleaners evaluated in this study with little 

penetration into the bulk substrate and a decrease in surface residue observed over time. The !%degree 

wound fiber coupons were selected for evaluation since the fibers are perpendicular to the surface and if 

cleaner is wicked by the fiber a deeper cleaner diffbsion into the bulk would be observed. 

The cleaner profiles with glass fiber phenolic (GCP) coupons are shown in Figure 4. Like the 

carbon tiber profiles very little cleaner is observed on the surface of the substrate with almost no 

penetration into the bulk substrate. Trends between the cleaners indicate TCA is absorbed less into the 

bulk compared to PCG and with PFD demonstrating a deeper penetration. 

The silica cloth (SCP) coupons demonstrate a higher absorption of cleaner (PCG and PFD) into 

the bulk compared to the other types of fiber-filled coupons (carbon and glass). Figure 5 shows the cleaner 

profiles in the SCP substrate with fibers perpendicular to the substrate. Higher levels of limonene (PCG) 

are actually observed deeper into the substrate compared to the surface. Eventhough the SCP substrate 

demonstrates the highest levels of cleaner, the cloth phenolic substrates demonstrate significantly reduced 

levels of cleaner on the surface and into the bulk compared to the insulation substrates. 

The effect of fiber direction is readily observed with the SCP coupons and the PCG cleaner. 

Figure 6 shows the difference in depth of hydrocarbon penetration for the fibers perpendicular to the surface 

(90-degree) compared to the fibers parallel to the surface (0-degree). 

SUMMARYKONCLUSIONS 

The diffusion of cleaner into rubber is dependent on the type of compounds found in the cleaner 

and the type of rubber. NBR insulation is normally known for its resistance to petroleum-based fluids. 

and thus, the dramatic difference in PFD (hydrocarbon-based cleaner) diffusion into CFEPDM compared to 

ASNBR is not surprising. The limonene-based cleaner PCG is also more similar in structure to the 

CFEPDM compared to ASNBR and deeper penetration into CFEPDM is observed. 

The diffusion of TCA into both rubber substrates shows similar absorption. Evaporation of TCA 

takes place at the surface of the substrates however because of the depth of penetration, there is a reservoir 

of TCA in the substrate bulk that even afier 60 minutes of drying allows a significant level of TCA to 

remain on the rubber surface. 
As would be expected cleaner diffusion into the cloth phenolic coupons occurs less readily than 

diffusion into the more porous insulations. The type of fiber also influences the penetration of cleaner as 

noted by the SCP coupons absorbing more limonene- (PCG) and hydrocarbon- based (PFD) cleaner 

compared to the glass and carbon cloth coupons. The depth of penetration IS not only dependent on the 

type of fiber in the phenolic but also on the fiber orientation. Fiber that is perpendicular to the surface can 

wick the cleaner deeper into the substrate compared to fibers that are wound parallel to the surface. 

3 
Cured ASNBR Substrate 

TCA Pmflle 

I 01 02 03 04 os 06 07 08 09 io 

Distahs frm Substrate Su6- (mm) 

Cured ASNBR Substrate 

PCG Pioflle 

3 

9 

z 'j ao 01 02 03 04 05 06 07 08 09 io 

- Dlstanca han SukWale Swf- (mmi 

3~ac 

20000 

lww 

Cured ASNBR Substrate 

PFD Profile 

0 

00 01 02 03 04 05 06 07 08 09 10 

Dirtamshorn Subsbate Surlxa (mmi 

Figure I : Cleaner Profiles in ASNBR Insulation 
Cured CFEPDM Substrate 

TCA Profile 

00 02 0.1 06 08 10 12 

astame horn Subsmta Swke (mmi 

3000C 

2000[ 

1000c 

Cured CFEPDM Substrate 

PCG Profile 

0 

00 02 03 06 08 10 12 

Distance horn Substrats Surtaca (mm) 

140000 

120000 

100000 - 

80000 - 

60000 - 40000 1 

00 02 04 06 08 10 12 

Distance ham Subsbale Surtacs (mm) 

Figure 2: Cleaner Profiles in CFEPDM Insulation 

h 
Wdegree CCP Substrate 

iTCA Cleaner1 

Wdegree CCP Substrate 

(PCG Cleaner, 

1wo - 

900. 

eam7w - 

600 - 

m400 - 

Wdegree CCP Substrate 

loo0 - 

mm700 ~ 

600 

500 - 

4w3w2w - 

1w - 

0. 

010 012 014 016 018 020 022 024 026 028 030 

cNstaw3fran S"rfaC'3,mml 

Figure 3: Cleaner Profiles in CCP Substrate 
90degree GCP Substrate 

(TCAClsaner) 

lMO r 

900 

m700 

600- 

500- 

400 

300 

200 

. 

- 

- 

- 

. 

010 012 014 016 018 OM 022 024 026 028 030 

Lhslane horn ourtace (mm) 

Wdegree GCP Substrate 

IPCG Cleaner) 

Io00 - 

900. & Ism” 

Boo - 

700 - 

600 - 

5w - 

4w - ?€lo 

200 . 1w ~ 

0- 

I I.. ... I.l.*.I.I...,.I. 

010 012 014 016 018 020 022 024 026 028 030 

Distance hm surface (mm) 

1m 

9w 

em 

700 

MI0 

500 

400 

300 

200 

1W 

0 

Wdegree GCP Substrate 

(PFD We-r) 

Figure 4: Cleaner Profiles in GCP Substrate 

X 
Wdegree SCP Substrate 

iTCA Lleansrl 

loo0 - 

900 . em700 - 

600 

500 - 

400 - 

300 - 

200 . 

I00 - 

0- 

- 

----.l"-,-,*IriU.- 

. *.---.._ -

010 012 014 016 018 OM 0?2 024 026 028 030 

D~slana hun purtacc (-1 

1000 

900 

BOO 

700 

600 

500 

400 

300 

200 

Wdegree SCP Substrate 

(PCG Cleaner) 

90degree SCP Substrate 

(PFD Cleaner) 

O(0 012 014 016 018 020 022 024 026 028 030 

DrSlanra Iran wr(&s (rml 

~ 

Figure 5: Cleaner Profiles in SCP Substrate 
SCP Substrate 

(PCG Cleaner) 

010 Ol? 014 016 018 020 022 024 026 028 03U 

Glsta-trm su!iaC$ (rnrn) 

Figure 6: Cloth Fiber Direction Influence on Absorption 
/-I . J I' scss,oll E3 Noif Mctnis f/occsSc', // 

Electron Beam-Cure Polymer Matrix Composites: Processing and Properties 

GEORGE WRENN and Barbara Frame /-I 1 

Oak Ridge National Laboratory 

One Bethel Valley Road 

P.O. Box 2009 

Oak Ridge, TN 3783 1 USA 

Fax: 423-574-8257 

Phone: 423-24 1-252 I (Wrenn), 423-576- 1892 

I- J "/ 

(Frame) 

Brian Jensen 

Langley Research Center/Mail Stop 226 

Hampton, VA 2368 1-2 199 USA 

Phone: 757-864-427 1 

Fax: 757-864-83 12 

E-mail1 B.J.JensenC.illarc.nasa.gov 1 

Alan Nettles 

Marshall Space Flight CenterED34 

Huntsville, AL 3.5812 USA 

Phone: 256-544-6 109 

Fax: 2 56-544-72 5 5 

E-mail1 Alan.Nettles@,msfc.nasa.~ov~ 

Researchers from NASA and Oak Ridge National Laboratory are evaluating a series of 

electron beam curable composites for application in reusable launch vehicle airframe and propulsion 

systems. Objectives are to develop electron beam curable composites that are useful at cryogenic to 

elevated temperatures (-2 17 "C to 200 "C), validate key mechanical properties of these composites, 

and demonstrate cost-saving fabrication methods at the subcomponent level. Electron beam curing 

of polymer matrix composites is an enabling capability for production of aerospace structures in a 

non-autoclave process. Payoffs of this technology will be fabrication of composite structures at room 

temperature, reduced tooling cost and cure time, and improvements in component durability. 

This presentation covers the results of material property evaluations for electron beam-cured 

composites made with either unidirectional tape or woven fabric architectures. Resin systems have 

been evaluated for performance in ambient, cryogenic, and elevated temperature conditions. Results 

for electron beam composites and similar composites cured in conventional processes are reviewed 

for comparison. Fabrication demonstrations were also performed for electron beam-cured composite 

airframe and propulsion piping subcomponents. These parts have been built to validate manufacturing methods with electron beam composite materials, to evaluate electron beam curing processing 

parameters. and to demonstrate lightweight, low-cost tooling options. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

htfp://ampet.msfc.nasa.gov 
MANUFACTURE OF POROUS CERAMIC MATERIALS BY COMBUSTION SYNTHESIS 

H.C. Yi. L.A. Whelati, and J.Y. Guigne 

Guigne International Ltd. 685 St. Thomas Line. Paradise, NF. Canada AIL 1C1 

ABSTRACT 

Porous ceramic materials are suitable for a wide variety of applications. By creating a porous ceramic, the 

properties of both porous materials and ceramic materials can be combined and utilised. The ideal applications for 

porous ceramic materials would include use in corrosive environments, thermal insulation, catalyst support. highlyefficient engine filters, pre-forms for composite materials, and implants into which body tissue could easily attach 

and grow. 

Experiments have been camed out to produce a series of porous ceramic materials using the combustion 

synthesis technique. These porous materials have such ceramic matrices as A1203. MgO, AI2O3-Mg0 and TiCAl2O3. Studies were done to investigate and characterize the ignition and combustion characteristics of these 

systems as well as to control the porosity and pore distribution of the final products. The combustion wave velocity 

ranged from 1-5 mm/s and the combustion temperatures ranged from I 500-2O0O0C, depending on the chemistries. 

All materials exhibited a large degree of linear expansion (100-200%) during the combustion reactions. 

Typical apparent porosity (open and interconnected pores) for the materials was >70% and the overall porosity was 

>80%. Successful attempts were made to control the apparent and overall porosity of the products. This was done 

through the addition of a diluent and b), physically confining the samples. As a result. the porosity can be made to 

vary controllably over a large range (4243% apparent porosity). 

A technique has also been developed to increase the quality of the high porosity samples by improving the 

pore size and distribution. As a result. both the strength and modulus of these samples were increased substantially. 

1.0 INTRODUCTION 

The unique characteristics of porous ceramic materials such as high hardness and resistance to heat and 

chemical attack make them suitable for a wide variety of applications. These materials can operate at high 

temperatures and do not degrade significantly due to oxygen. however, they are brittle. The brittleness is associated 

with voids. cracks, and impurities in the material. Several important properties of porous ceramic media include 

their lightweight. thermal insulation. filtration ability, and absorbency. 

Combustion Synthesis or Self-propagating High Temperature Synthesis (SHS) is a novel technique and a 

proven effective method of producing various advanced. porous. high-temperature ceramic and composite materials 

11-31. It involves the reaction of solid state powders initiated by an external energy source and combines the 

principles of chemical reaction engineering and materials science. Once a sample is ignited, the highly exothermic 

reaction would ignite the next adjacent reactant layer by itself thereby generating a self-sustaining combustion wave 

propagating through the material. 

The SHS method has many advantages over traditional synthesis techniques. It saves enera! since no hightemperature furnace is required, it allows for faster production since the typical combustion velocity is from a few 

millimetres to a few centimetres per second, it produces a relatively high purity of the final product since high 

combustion temperature vaporises most impurities, it requires simple equipment. and it allows simplicity of the 

whole process. Owing to these advantages, it is likely that materials produced by SHS have a lower overall cost 

compared to the conventional melting-casting route. 

A SHS reaction is defined by three main parameters. They are: I) an ignition temperature at which the 

reaction becomes appreciable and self-sustaining, 2) a combustion temperature (maximum temperature achieved), 
‘and 3) a combustion wave velocity which is the overall combustion rate. However. other parameters such as green 

densit). particle size. and the reaction environment may have a profound influence on the combustion reaction. 

2.0 METHODOLOGY 

2.1 Materials 

Combustion experiments were carried out using various reaction systems to produce a wide range of porous 

ceramic materials having a matrix of A1203. MgO, or a combination of the two (A1203-MgO). The systems are 

represented by the following reactions: 

2 B203 + 6 Mg + C=BjC + 6 MgO (2.1) 

J Bz03 + 6 A1 + 2C + 3 Mg = 2 B,C + 3 Alz03 + 3 MgO (2.2) 

2 B203 + J A1 + C = B,C + 2 A1203 (2.3) 

2 B?03 + TiH2 + 4 A1 + 2C = TiC + B,C + 2A1203 + HZ(g) (2.4) 

2 B203 + 4 A1 + C + s CaO = B4C + 2A1203 + x CaO (2.5) 

The reactions are designed such that at least one substance boils at a temperature lower than the combustion 

temperature of the reaction to assist pore formation. The evaporation of that substance at the combustion front 

releases gases, thus help generating pores in the product. Some physical data for the reactant powders are shown in 

Table 1. The gasifqing substance in equation (3.1) is Mg. in (2.2) is Mg and B203, in (2.3) is B103. in (2.4) is B,03 

and H2. 

Table 1: Data for Reactant Powders 

2.2 Experimental Methods 

Calculated masses of reactant powders were mixed to produce the desired composition. according to the 

reactions shown in (2.1)-(2.5). The powders were thoroughly mixed by ball milling using ceramic balls. To form 

the 0.5-inch diameter pellet to be used for experimentation, a known mass of this mixed powder was measured out 

on a balance and then pressed using a tool steel die and a hydraulic press to 60 f 3% theoretical. Lower density 

pellets (-30-35%) were also fabricated using a technique developed in our laboratory. 

Once the sample was prepared. it was placed in a fume hood and ignited in air using an oxygen-propane torch. 

The reaction of the sample was recorded using a high-resolution colour video camera and VCR system to allow 

determination of the velocity of the wave propagation and the analysis of its behaviour. To determine the 

temperature profiles. samples were ignited inside a chamber in an inert atmosphere by applying high power through 
a tungsten ignition coil. Temperature profiles were measured using Tjpe C thermocouples and a data acquisition 

system. 
3.0 RESULTS AND DISCUSSION 

Reaction 

3.1 Combustion Characteristics and Porosity 

Wave Velocity I Tad 1 Porosity(%) 

mm/sec 

A typical temperature profile during the combustion synthesis process is shown in Figure 1 for a pellet with 

60% density from Reaction (2.3). The maximum temperature, Le., the combustion temperature for this particular 

sample was 1900°C and the wave velocity was 1.7 mm/s. Combustion wave velocities for other reactions are also 

shown in Table 2. along with the adiabatic temperatures of these reactions. 

Apparent 

Figure 1: A Typical Temperature Profile 

Overall Ratio 

1800 

0 

(2.1) 1.7 

(2.2) 3.7 

(2.3) 1.5 

(2.4) 1.3 

$ 1500 

% 1200 

3 

2470 73 82 89% 

2054 71.3 82.5 86% 

2054 71.5 84.3 85% 

2040 77.0 84.5 91% 

ti E 900 

E 600 

300 

0 

....................................... 

....................................... 

....................................... 

.................................... 

........................ 

......... 

0 100 200 300 400 500 600 700 800 900 1000 

Time, sec. 

For reactions (2.1) and (2.3). the pellets were easily ignited and the combustion wave velocities were 

around 1.5 to 1.7 mds. The combustion waves were unstable due to two factors. Firstly, the high thermal 

conductivity lead to a large heat loss by conduction and. secondly. the large expansion during combustion decreased 

the continuity of the material and made it difficult to react the next adjacent layer. Reaction (2.1) was particularly 

violent and unstable and the wave propagated in a helical pattern. These factors were responsible for the low 
velocity of these samples and several did not complete the combustion process. Reaction (2.2) is a combination of 

reactions (2.1) and (2.3) and produces a ceramic composite with matrices of A1203 and MgO. This reaction had a 

higher wave velocity because of the high exothermiciQ. Reactions (2.4) was also easily ignited and produced a 

relatively high wave velocity. Reacted samples contained higher apparent porosities due to the generation of 

hydrogen gas at the combustion front. All samples showed large expansion. some as much as 300%. and the 

porosity tended to be non-uniform as will be shown later. 

i ................................................... -, 

..................................................... 

$ 

3.2 Porosity Control 

The materials produced by the above reactions were very porous and because of that, they were also very 

fragile. In some circumstances, lower porosity might be desired. Two techniques were used to control the porosity 

of these materials: I) by adding a diluent to the combustion reaction and 2) by physical confinements to limit 

expansions. 

3.2.1 Effect of the Diluent 

One method of controlling the product porosity was to reduce the exothermicity of the chemical reactions 

by addition of one or more diluents. For instance, by adding an oxide. such as CaO. to the reaction to act as a 

chemical diluent as shoNn in Reaction (2.5). This diluent decreased the combustion temperature and. therefore, 

decreased the amount of expansion of the sample. Both the apparent and overall porositj, decreased drastically as 

the amount of diluent increased, as shown in Figure 2. 

Figure 2: Effect of Diluent on Porosity 

90 

80 

70 

60 

60 

b 40 

30 

20 

ae 

- g 

0 

10 

0 

3.2.2 Physical Confinements 

Confining the samples inside a cylinder made of stainless steel also controlled porosity of the materials. A 

rod was inserted into the end of the cylinder through a hole and could be fixed at a desired location. depending on 

the length (and thus porosity) desired for the samples. A sample could be completely confined and not permitted to 

expand at all or a specified distance could be left for the sample to expand. thus creating different porosio. 

Table 3 shows the average apparent and overall porosity and also some measured velocities for some 

confined samples. As clearly shown in the table. the apparent and overall porosity (as well as the velocity) increases 

with decreasing confinement. The highest porosity occurs in the samples that were permitted to undergo fiee 
expansion. The velocity increases with decreasing confinement due to the fact that less heat is being conducted 

away from the sample. 

Confinement Condition Apparent Porosity: P(%) 

Free expansion 75.8 

30 mm 72.6 

25 mm 68.5 

20 mm 62.9 

(Total length once reacted) 

Completelj confined 56.5 

Table 3: Average Porosity and Velocity Results for Confined Samples (Density=60%) 

Overall Porosity: Average Velociq 

Po (%) (ds) 

82.3 

79.5 9.1 1 

75.4 

70.5 5.85 

65.2 4.53 

Although the degree of porosity could be controlled. there seemed to be a porosity gradient in those 

materials. During combustion, a sample that was not completely confined would expand in length until it reached 

the rod. A higher density (and thus lower porosity) would be created at the end that was pressing against the rod 

therefore creating an uneven pore distribution throughout the sample. To produce samples without porosity 

gradient, lowdensity cylindrical samples were prepared before placing it in the confinement cylinder. The sample 

was made to a specified length, depending on the desired porosity and, consequently. the samples also contained 

various densities. This method did not require the sample to expand during combustion and. since the powder was 

loose and evenly distributed before combustion. the product also contained a uniform pore distribution. Figure 3 

shows the average apparent and overall porosity and also some measured velocities for the samples of different 

densities. As can be seen from the figure, the apparent and overall porosib. increases with decreasing densitj. 

Figure 3: Effect of Confinement on Porosity 
90 

80 

70 

60 

E 50 

E 

e 40 

30 

20 

10 

0 

POverall 

n 

u7 

64 

Options 

3.3 Improvement of Pore Structure 

When sample produced from igniting relatively high-density pellet (-60%) of the reaction (2.3) with free 

expansion. they often contain macro-pores in the order of lmm in size. A typical photomicrograph of such a sample 

is shown in Figure 4. Such samples had very low strength and were somewbat fragile. Figure 5 shows a typical 

stress-strain curve for such a sample during a compression test. The strength of the sample was 298 psi. To increase 

the strength of these materials, green pellet with about 35% density was prepared and ignited. Figure 6 shows a 

photomicrograph of the same reaction. Apparently, the surface of the sample is much smoother and no macropores 

existed. The compression test of such a sample is show in Figure 7. The strength of the sample was 74Opsi. much 

higher than the sample produced from a green pellet with 60% theoretical density. The average mechanical 

properties from samples produced by the two approaches are shown in Table 4. 
Figure 4: An optical photograph showing macropores on surface for a sample reacted from a pellet with a 

green density of 60% by Reaction (2.3). 

300 

2M) 

50 

0 

-50 

5 10 15 20 .,.,.. __ ........................................ ..n_-..-.__l" ......... I ".."llll.. ........ .. ...~ . < 

Strain (inlin), % 

Figure 5: A Typical Stress-Strain Curve During Compression for a sample reacted from a pellet with a green 

density of 60% by Reaction (2.3). 
Figure 6: An optical photograph showing no macropores formation on surface for a sample reacted from a 

pellet with a green density of 35% by Reaction (2.3). 

800 

700 

600 

500 

400 

300 

200 

100 

0 

-1 00 

, 8 , I i 

2 4 6 8 IO 12 1) 

Strain (idin), X 
Figure 7: A Typical Stress-Strain Curve During Compression for a sample reacted from a pellet with a green 

density of 35% by Reaction (2.3). 

Samples Produced From Strength. MPa 

60% Pellets 1.05 

35% Pellets 5.47 

Modulus. MPa 

2.06 

4.43 

4.0 CONCLUSIONS 

Highly porous ceramics have been produced by the combustion synthesis technique. Large expansion is 

the characteristic of most systems, therefore creating large porosity. However. porosity of the products could be 

controlled. This was achieved by adding a diluent and physically confining the samples. 

Highly porous samples produced from relatively high green density pellets exhibit poor mechanical 

properties due to macropores formation in the samples. An improved fabrication technique has been employed to 

produce higher quality. uniform distributed pores. As a result, both the compression strength and Young's modulus 

increased substantially. 
REFERENCES 

1. Munir. Z.A. and Anselmi-Tamburini, U., 1989, “Self-propagating exothermic reactions: the synthesis of high 

temperature materials by combustion”, Mater. Sci. Rep.. 3, 227-365. 

2. Yi, H.C. and Moore, J.J., 1990. ”Review: Self-propagating high temperature (Combustion) synthesis (SHS) of 

powder-compacted materials”. J Mnter. Sci. 25, 1 159-1 168. 

3. Moore. J.J., and Feng, H.J.. A-og. In Mater. SCI., 39, 243-316 (1995). 
The Composites Affordability Initiative 

JOHN MISTRETTA 

Materials & Manufacturing Directorate 

Air Force Research Laboratory 

2977 P Street, Room 12 1 

Wright-Patterson Air Force Base, OH 45433-7739 USA 

Phone: 937-904-4597 

: john.mistretta@wpafb.af.mil 

The Composites Affordability Initiative (CAI) is a multi-service and aerospace industry 

collaborative effort. This long-range initiative has the goal of developing the technologies and tools 

necessary to reduce the acquisition cost of composite structures by an order of magnitude. The 

current phase of CAI includes Joint Strike Fighter-related transition programs at Boeing and 

Lockheed Martin, plus a cooperative pervasive technology program. This is the second phase of a 

four-phase effort. 

To provide sufficient depth, all relevant areas including design, fabrication, assembly, 

analysis, quality, and cost models, must be advanced. In the past year, several large producibility 

articles have been developed to focus the fabrication and assembly technology development process 

under the pervasive technology program. In addition, cost, analysis, and quality tools have been 

developed and enhanced. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://arnpet. msfc. nasa. gov 
Title: 

Co-Auth'2rs : 

Company : 

Advanced Ceramic Matrix Composites for 

Aerospace Applications 

Bill Patterson, Bob Klacka, John Garnier, Paul Gray, 

Honeywell Advanced Composites Inc., Newark, Delaware USA 

Abstract: 

Advanced ceramic matrix composites (CMCs) are an er,abling 

technology for hypersonic trans-aerospace, missile and turbine er.gine 

applications demanding high performance utility. Honeywell Advanced 

Composites has developed a palette of CMCs in limited conmercial 

production and in various stages of evaluation for aerospace related 

programs. CMCs include carbon fiber reinforced siiicor, carbide (C/SiC) 

and Enhanced silicon carbide fiber reinforced silicon carbide (ESiCf/SiC). Hardware fabrication cap. use chemical vapor infiltration 

(CVI), silicon melt infiltration (MI) and chemical conversion 

processing techniques. C/SiC is a 1eadir.g thermal heatshield 

protection material for several heat shield structural desigcs 

(RLV/SOV/SMV) and has demonstrated excellent low erosion hypersonic 

leading edge performance. Because of materials attributes of low 

density, high strength and very high temperature capability, C/SiC has 

been in development for linear Aero-spike engine applications including 

ramp and pump. SiCf/SiC MI CMC is qualified as the orily 2200 F, 20 

Ksi, long duration materials for NASA high-speed civil transport 

advanced turbine engines. Commercial accornplishrnents also include more 

than 10,000 hours of field time in stationary power turbine engines 

(DOE-CFCC). Open literature C/SiC, E-SiC/SiC and SiC/SiC MI CMC 

thermal, mechanical data will be presented including customer approved 

hardware and test results. The following are selected viewgraphs from 

the presentation, which contains more detailed information. 

Material challenges for Aerospace 

WI ate r i a I C ft a I1 e II g es fts r A e r oS p a ce 

t Weight is always a premium coiiiniodity 

Utilizing CMCs will lighten ei-istitig rii~ral .q~srem.s 

* Kext-generation perforinanct: goals impose very 

high teinperalures on existing metal components 

CWizing CA4C.c icYll great(\. estcvid per-fi)r.mnric.r capahilitics 

* Cooling, in any fonn, greatly increases weight 

CMCs car1 he ri117 liotter-, r-c~dwing cwolilig 

* Strength of metals drops off rapidly with temperature 

CMCk r-~tai17 or i17c.r-easr str-rtigth up 10 as high as 3000F 
Palette of C/SiC and SiC/SiC ceramic matrix composite materials 

*. SIC- kibcrs: fir-Nicalon. Type S. Tyranno. 72.11. Type SI\. Sylmniic 

* Anti-asidants are added for thc "cnhnnced" versions: E-SiC:SiC and IJ-c'/SiC 

Honeywell ACI: 

C hl C nranufacturing/I)rocessin~ Options 
Demonstrated 3,Iaterials Applications 

('\'I SIC SIC 

CVI L-SIC SIC 

WI SIC SIC" 

Re-cnlr?; hcat shicltk, 

Turbo-puiiip ruturs stators 

Thrusters. fins 

Thrusters, [siding cdgc 

ccrmponcnts, canes 

C'umbuslion chanibcrs 

antl \atics 

Turbine enginc exhaust 

slructurcs. coinbustion 

chainbers. It.ncling edge>. 

flcut shields, mirrors 

tiirbine cng. combustors, 

blades and \mes. 

[m 

Loic ~'cccsstor~iitcs 

in lugli acrothcmial licating 

\;cry high wcngtli and 

lo\\ rccessiori propcrties. 

LOW rcceshion Tiitch 

in rochet cuhaust. 

Thermal shoch rehistant 

antl high strciigtii. ION pcrni. 

Dcmonstrstcd sires\ rirptiir~~ 

pcrfirinance tu 22001- IS hsi 

3verview C/SiC thermo-mechanical properties. 

C/SiC Material Properties Overview 

F'roncrtv 21) C'iSiC' Novoltex'SiC MI CPSic' 

(c'vr) ({'VI) (141) 

RT Tensile. ksi 76 7- IO 5 '1 

2700 F Tcnsiic, Lsi 77 9-12 60 

RT ('ompression. hsi 75 ! -> S h 

Cross-Ply Tcnsilc, psi I900 n.cl. 2200 

-7 

Iosipescu Shear, ksi n.d. 15 

Interlaminor Shcar.Ksi 3.7 n.d 

16.5 

4.1 

Thcr.Cciiid. Bt u, HrFtF 3.8 7.1 6. I 

* CiSiC properties depend highly on fiber type, weave and processing. 

* CiSiC attributes are high tcrnperature strength, low areal weight and 

reccssion resistancc over carbon-carbon 

, I 
Other Properties of MI C/SiC 

Jmlm 

Density 

Porosity 

Thermal 

Expansion 

Thermal 

Conductivity 

Permeability 

(-1 50 psi) 

Value 

2.1-2.2 grn/cc 

2 - 4 volume % 

2.0-3.6 pprn 

per deg C 

6 - 7 BTUlhr 

ft2-Deg F/fi 

0.080 Ib/ 

Ft2-min 

Comments 

Almost theoretical density. 

Isolated, closed porosity in tows. 

Linear increase from 200-1200 C 

Value almost “2 x” above CVI C/SiC 

Value is “far lower” than all CVI Sic. 

(measured on surfaceground MI ClSiC 

disks with no “seal coat”) 

Summarize of MI C /Sic thermo-mechanical properties. 

Summary and Conclusions 

* A lower cost process for producing ClSiC materials having properties 

“similar” to an all-CVI Sic matrix has been developed. 

The higher density MI matrix increased the thermal conductivity 

and matrix dominated substrate properties over a CVI Sic matrix. 

* The MI process for producing ClSiC can reduce manufacturing 

times from 30-50 percent. 

* The MI processed developed may be useful for rendering 

complex fiber preforms “ impermeable”. 
Overview SiC/SiC thermo-mechanical properties. 

SiC/SiC Material Properties Surnmar-y 

m 

RT Tensile. ksi 37 52 

2200 I: Tensile. ksi 3s 4x 

RT Compression, ksi 81 85 

Cross-Ply Tensile. psi I200 1400 

losipescu Shear, ksi l1.d. IS 

hite~laininar Shear.Ksi 5.5 5.0 

Thcr. Con d. Btu, I-i I' 1.3 t 2-4 9.0 

(('VI) (MI) 

(a) Utilizes Ill-Uicalon Fibers, enhanced kersiort 

(b) Litilizes Sylramic Fibers 

* SiCiSiC properties depend highly on fiber type. weave and processing 

* SiCiSiC attributes arc high tempcraturc strength for extended times 

over C'SiC Both CVI SiCiSiC and MI SiCiSiC materials provide 

optical quality surface for mirrors 

E-SiC/SiC: and Mclt Infiitratcd SiCXiC CblC," Materials 

* E-SiC/SiC attributes 

NASA HSCT Engine Propulsion Material Qualificd 

Performance Utility capablc: 2200 1; cxtcndcd life ('2000 hours) 

Static strcss up to 20 Ksr 

Low Cycle Fatigue runout: 10(+6) cyclcs cg' IOKsi. 2200 F) 

Melt Infiltrated SiC/SiC attributes - Field demonstration up to 15.000 hours in stationary power testing (2200 F) 

Joining by Melt Infiltration 

Materials in development undcr AF IHPTET 2400 F for cxtcndcd life (>2000 hours) 

Static stress up to 20 Ksi. LCF in progress at 2400 F. 

Applications 

- Advanccd turbinc cnginc hot section componcnts 

Turbine cnginc afterburner flaps and seals 

Hypersonic applications with mission cyclcs > 100, T < 2500 F 

Mirror panclsisuppoort for optical concentrators and high cncrgy beam deflection 

... 
'Typical uses and applications for C/SiC and SiC/SiC CMCs 

' Summary 

C/SiC and SiC/SiC materials are enabling for many high 

perfonnance advanced space and missile applications 

Demonstrated successes on prototype and limited production basis in: 

Turbopuinp blades and vanes 

Structural thermal protection systems 

Thrustcrs 

Combustor liiicrs 
Aluminum Investment Cast Spacecraft and Aerospace Structures /.’ ,’ ,/ 

JOHN BOWKETT 

Nu-Cast, Inc. 

29 Grenier Field Road 

Londondeny, NH 03053 USA 

Phone: 603-432- 1600 

Fax: 603-432-0724 

E-mail: nci@,grolen.com 

The mandate for “better, faster, cheaper” has had a profound effect on aerospace projects. 

Project personnel, budgets, and development time have been compressed. Coupled with this mandate 

has been the threat to cancel projects that exceed their budgets. Projects perceived to be grandiose or 

padding their cost estimates are eliminated or not even considered for selection, regardless of their 

technical or scientific merit. There is no single solution for this situation. To work effectively in this 

environment requires an end-to-end approach that reduces project engineering, analysis, drafting. 

checking, manufacturing, testing, and integration. This approach, above all, must include the desire 

to depart from standard aerospace engineering practices. 

Engineers at Goddard Space Flight Center addressed this changing environment with investment casting technology. Previously, casting had been used for electronic enclosures and some 

secondary structures; it required production rates of 100 units before being considered. Expanding 

the technology to primary load path spacecraft structures had been perceived to be costly and of 

marginal benefit. NASA engineers designed and successfully flew a low-risk investment cast spacecraft and then progressed to a larger, complex monolithic spacecraft for Pegasus-class expendable 

launch vehicles and primary load path payload structures for the Space Shuttle. 

this technology. The presentation will showcase advanced applications with aluminum investment 

casting, the evolutionary approach taken, cost savings realized, technical and political complications 

encountered, lessons learned, and future work. 

Significant and surprising cost savings have been realized end to end on projects employing 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc. nasa.gov 
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DYNAMC OXIDATION OF A PLASMA-SPRAYED 

Cu-Cr COATING 

I(. T. Chiang 

The Boeing Company 

Rocketdyne Propulsion & Power 

6633 Canoga Avenue, Canoga Park, CA 91309-7922 

1 kuann-tsan.k.chiann(i$boeiw.com 1 (818) 586-1211 

Abstract 

The dynamic oxidation of a plasma-sprayed Cu-30 vol.% Cr coating was investigated in an electric archeated wind tunnel. The wind tunnel generated high velocity, fully dissociated air containing atomic oxygen. The 

metal surface temperature was maintained at 650°C for up to 5 hours (h). The high velocity atomic oxygen enhanced 

oxidative evaporation of Cr metal resulted in rapid metal weight loss. The high temperature atomic oxygen caused 

rapid oxide formation on Cu. The scale cracked and spalled severely during cooling to room temperature. The 

plasma-sprayed Cu-Cr coating provided good oxidation protection for the copper alloy substrate under a dynamic 

environment. The oxidation mechanism involved four steps. First. oxidative evaporation of elemental Cr resulted in a 

Cu-enriched surface with increased nucleation sites. Second. rapid whisker formation resulted in a mushroom-like 

Cu-oxide scale morphology. Scale formation involved a combination of surface diffusion. short circuit diffusion, 

lattice diffusion and evaporation. Third, inward migration of oxygen atom formed mixed oxides of CuO and CuCr02. 

Fourth. formation of a continuous Crz03 layer beneath the external Cu, Cr mixed oxides. The scale morphology and 

oxidation mechanisms will be compared with those of static laboratory furnace oxidation. 

Introduction 

Copper-based alloys and composites are candidate materials for high heat flux structural applications in 

hypersonic vehicles because of their combined properties of high-thermal conductivitj, and high-temperature strength 

(Refs. 1 and 2). A major limitation to using copper-based materials is their rapid oxidation at elevated temperatures. 

Protective coatings that shield these materials from oxidation must be employed to enable their use at temperatures 

up to 650°C. 

One approach to a protective coating for copper-based alloys uses chromia scales. like those formed on 

M-Cr alloys (where M is Fe, Ni, or Co). which impart oxidation resistance when formed on the alloy. One practical 

requirement of such coatings is that the chromium concentration at the surface must be high enough to form a 

continuous Cr203 scale, which must be stable in the service environment. Reference 3 showed that Cu-30 vol.% Cr 

coatings produced by vacuum plasma spray (VPS) form a protective scale on Cu-Nb alloy in static air at high 

temperatures. However. Ref. 4 showed that oxidative vaporization of Crz03 in oxygen is enhanced by about 10 at 

550°C by the presence of 2.5% atomic oxygen. Therefore, a concern is that the plasma-sprayed Cu-30 vol.% Cr 

coating will not protect copper-based alloys employed in hypersonic vehicle applications where atomic oxygen may 

be present. 

The objective of this study was to examine the performance of plasma-sprayed Cu-30 vol.% Cr coating 

under dynamic oxidation conditions containing atomic oxygen. The paper presents results from dynamic oxidation 

tests of Cu-15 vol.% Nb substrate with a VPS Cu-30 vol.% Cr coating. The tests were conducted at 650°C in an 

electric arc-heated wind tunnel. Data for weight change during static and dynamic oxidation and metallurgical 

analysis results are presented for coated and uncoated specimens. 

09001 48 da: 
Experimental 

Specimens were 2.5-cm-diameter discs cut from a 0.76-mm-thick Cu-15 vol.% Nb sheet. The specimens 

were coated on all surfaces with Cu-30 vol.% Cr coating. Details of the coating deposition process were described 

elsewhere (Ref. 3). 

Coated specimens were tested under dynamic oxidation conditions (Mach 4.2. 1.5 torr pressure. and 2.9 

MJAg enthalpy) at 650°C for times to 5 h in the Hypersonic Materials Environmental Test System (HYMETS) at the 

NASA Langlej Research Center (Ref. 5). The HYMETS is a 100-kW constrictor-arc-heated wind tunnel that uses 

air plus nitrogen and oxygen in ratios equivalent to air to produce the test environment. Specimens under test are 

held on a pneumatic strut so that gas flow is normal to the surface. The temperature of a specimen is monitored 

during exposure by a thermocouple attached to its back surface or by a radiation pyrometer focused on its fiont 

surface. The test conditions attainable in the HYMETS are not equivalent to the environment associated with high 

heat flus structural applications of hypersonic vehicles. However. the environment does contain high-speed flowing 

gas with atomic and molecular oxygen, which is of critical concern to using copper-based materials in hypersonic 

vehicle applications. 

Tests consisted of exposure of specimens for half-hour periods at 650°C for an accumulated exposure of up 

to 5 h. The specimen temperature was maintained at 650°C by adjusting the power input to the HYMETS. 

Specimens were periodically removed from the test facility for weighing and examination. 

The morphology and chemical composition of the surface of the coated specimens were characterized, 

before and after oxidation exposure. by scanning electron microscopy (SEM) with energy dispersive x-ray analysis 

(EDXA). and x-ray diffraction (XRD). Selected specimens were cross-sectioned and examined bj SEM with EDXA. 

Results and Discussion 

The weight change histor) of Cu-30 vol.% Cr coated Cu-15 vol.% Nb specimens under dynamic oxidation 

conditions at 650°C in the HYMETS facility is shown in Figure 1. Data are included for coated specimens and 

0 1 2 3 4 I 6 

Time, hours 

Figure 1. Oxidation weight change history of Cu- 15 vol.% Nb with 

Cu-30 vol.% Cr coating under dynamic conditions at 650°C 

0900148 doc 
uncoated Cu-Nb specimens oxidized under static and dynamic oxidation conditions. The test data for a pure 

chromium specimen under dynamic oxidation condition are also included because chromium is a major constituent 

of the Cu-Cr coating. The chromium samples experienced a slight increase in weight with exposure to static 

oxidation in air at 650°C but showed a severe weight loss under dynamic oxidation conditions. XRD data show Cr 

and Crz03 as the only phases present on the surface after exposure to either static or dynamic oxidation. These results 

confirm that the conditions present in HYMETS are sufficient to accelerate the oxidative evaporation of chromium 

or Cr20,, as described by Fryburg et al. (Ref. 4). The plasma-sprayed Cu-30 vol.% Cr coating provided good 

oxidation protection to the Cu-Nb substrate during exposure to dynamic oxidation condition. The overall weight 

change over the 5-h test was less than 2 mgkm'. The specimen showed a rapid weight increase during the initial 1 h 

of dynamic oxidation exposure. followed by a slow rate of weight decrease. Uncoated Cu-Nb alloy specimens 

experienced a severe loss of weight with oxidation exposure under both static and dynamic oxidation conditions. 

Under both conditions, the uncoated specimens form heavy oxide layers. which are not protective. Upon cool-down. 

the oxides on the surface spa11 from the specimen exposing bare alloy. 

Scanning electron micrographs of the specimen surface of as-coated. as well as after static and dynamic 

oxidation exposures, are compared in Figure 2. The as-coated surface exhibits a ?.plat" structure typical of the VPS 

process (Figure 2a). Semi-quantitative EDXA showed that the coating composition was Cu-26 wt.% Cr, which was 

within 1% of the nominal composition. After static oxidation in air at 650°C, the coating surface formed fine-grained 

crystalline oxides (Figure 2b). EDX analysis showed the surface contained elements of Cu, Cr, and oxygen 

indicating the formation of Cu-oxide and chromium oxide. The oxide morphologies of the coating under dynamic 

conditions were distinct from those of static oxidation. Figure 2c shows the coating surface morphology after 3 h of 

Figure 2. Scanning electron micrographs of plasma-sprayed Cu-30 vol.% Cr coating surfaces. 

(a). as-coated. (b) after static oxidation in air for 22 h, (c) after dynamic oxidation for 3 h. 

09001 48.d~ 
dynamic oxidation. The surface is covered by porous. spherical oxide deposits, which are typical of oxides formed 

by Ni and Cr containing alloys under dynamic oxidation conditions (Ref. 6). The porous mushroom-like structure 

was formed because of rapid evaporation of chromium element through interaction of chromium with atomic oxygen. 

and rapid formation of whiskers of copper-oxides through surface diffusion. lattice diffusion, and evaporation. The 

EDXA of the coating surface showed strong peaks of Cu and oxygen indicating that the outer surface layer was 

covered predominantly by Cu-oxides. 

Exposure 

Condition* 

As coated 

1 h at 650°C 

5 h at 650°C 

The XRD data in Table 1 demonstrate variance in the phase composition of the surface region of the Cu-30 

vol.% Cr coating with oxidation exposure time at 450°C. The coating in the as-coated condition consists of only 

face-centered-cubic (fcc) Cu and body-centered-cubic (bcc) Cr with no evidence of compound or solution. When 

exposed to static or dynamic Oxidation conditions. the coating oxidizes to form mixed oxides of Cu and Cr. The 

surface of coated specimens tested under dynamic oxidation conditions at 650°C consists of Cu. Cr. CuO. Crz03. and 

C'uCrO:. The primary oxide phase identified for coated specimens after exposure to dynamic oxidation condition is 

CuO with lesser phases of Cr20r, and CuCrO?. The ratio of metallic Cu and Cr is greater for the exposed specimens 

than for the as-coated specimen. The amount of Cr oxides detected by XRD in the surface region decreases with time 

of exposure to dynamic oxidation at 650°C. 

cu Cr CUO CrzO3 CuCrOz 

- - - vs S 

W W S m W 

W W S vw vw 

Table 1. XRD Results for Cu-30 vol.% Cr Coating 

* Specimens exposed to dynamic oxidation in arc jet (HYMETS facility at NASA Langley Research Center) 

XRD Signals : vs - very strong; s - strong; m - medium; w- weak; vw - very weak 

Cross-section views of Cu-Cr coated Cu-Nb substrate. in the as-deposition condition and after 3 h of 

dynamic oxidation, are shown in Figures 3 (a) and (b). The coating consists of heterogeneous of Cu and Cr phases. 

After dynamic oxidation. a multilayered-oxide structure was formed. The oxides consist of an approximately 15-pmthick. mushroom-like external oxide layer. The EDX analysis [Figure 3 (c)] shows that the oxide contained only 

elements of Cu and oxygen indicating the oxide was CuO. Underneath the porous Cu-oxide, a region of solid CuO 

approximately 20 pm thick was observed. Underneath the external oxides, a mixed Cu-Cr oxide layer was clearly 

seen. The thickness of the mixed oxide layer was not uniform ranging fiom 1 to 25 p. Beneath the mixed oxide 

layer and near the unreacted coating/oxide interface, a layer enriched in Cr and oxygen was observed [Figure 3 (d)]. 

indicating formation of Cr203 scale. 

The results presented here with the results from Refs. 3 and 4 suggest the following mechanism of 

protection by the Cu-30 vol.% Cr coating. When the plasma-sprayed Cu-Cr coated Cu-Nb specimen is exposed to a 

dynamic oxidation condition. the oxidation mechanism involved four steps. First, oxidative evaporation of elemental 

Cr resulted in a Cu-enriched surface with increased nucleation sites. Second, rapid evaporation and whisker 

formation resulted in a mushroom-like Cu-oxide scale morphology. Scale formation involved a combination of 

surface diffusion, short circuit diffusion, lattice diffusion, and evaporation. Third, inward migration of oxygen atom 

formed a mixed oxide of CuO and CuCrO?. Fourth, beneath the external Cu, Cr mixed oxides. the oxygen partial 

pressure was reduced. Because the Cr particles in the plasma-sprayed Cu-Cr coating were finely dispersed (Ref. 3). 

the flux of Cr was sufficient to form a continuous Cr203 scale under the external Cu-oxides and Cu, Cr mixed oxides. 

As the Crz03 scale developed, it acts as a barrier for ouhmrd diffusion of Cu ions and inward penetration of oxygen 

0900148 doc 
CULU 

-0 i Ka 

uKu 

0 Ka 

1 CuLa 

2.00 4.00 6.00 8.00 

(c) 

CuKa 

2.00 4.00 6.00 8.00 

9148-2 (d) 

Figure 3. Scanning electron micrographs of Cu-Cr coated Cu-Nb alloys. (a) as-coated, (b) after 3-h 

dynamic exposure, (c) EDX of external oxides. and (d) EDX of oxideicoating interface. 

ions. The Cr203 was shielded from atomic oxygen attack by the external Cu-oxides. and mixed Cu. Cr oxides. With 

the coating. the Cu-Nb substrate was protected against the degradation caused by atomic oxygen-containing hot gas. 

Summary and Conclusion 

Cu-Nb specimens coated with plasma-sprayed Cu-30 vol.% Cr coating were tested under dynamic oxidation 

conditions at 650°C for up to 5 h. Uncoated specimens were tested for comparison. The coating protects the alloy 

under dynamic oxidation conditions. with specimens gaining less than 2 mg/cm’ over a 5-h exposure period. 

Uncoated specimens tested under static and dynamic conditions experienced severe weight loss because of spalling 

of the oxides formed at the surface. 

The examination of coated specimens using SEM. EDXA, and XRD showed that Cu and Cr exist in the ascoated specimen as a heterogeneous mixture. When oxidized, the coating is transformed to a mixed oxide containing 

the phases CuO, CuCrO?, and Cr203. A proposed mechanism for protecting the alloy is that a continuous layer of 

Cr203 forms underneath the external Cu-oxides and CuCrO?. The CrlOi acts as a barrier for outward difhsion of Cu 

ions and inward penetration of oxygen ions. while the external CuO. Cu-Cr mixed oxides shield the Cr203 fiom the 

hostile atomic oxygen environment. 

0900148 doc 
Acknowledgements 

This work was supported by US Air Force Contract No. F33657-91-C-2012. Contributions from R. K. 

Clark and T. A. Wallace of NASA Langley Research Center in directing the dynamic oxidation tests and analyses are 

gratefully acknowledged. 

References 

1. Tenney. D. R.: Kisagor. W. B.; Dixon. S. C., Materials and Structures for Hypersonic Vehicles. in The 1988 

ICAS Proceedings, American Institute of Aeronautics and Astronautics, Inc. Washington. DC. vol. 1, 1988, pp. 

398-4 15. 

2. Ronald, T. M. F.. NASP Launches New Materials. Advanced Materials and Processes. vol. 144. September 

1993. pp. 24-27. 

3. Chiang. K. T.. Krotz. 1'. D., Yuen. J. L., Blanching Resistant Cu-Cr Coating by Vacuum Plasma Spray. Sirrjince 

nnd Coatings Technologr. vol. 76-77, 1995, pp. 14-19. 

4. Frjburg. Ci. C.. Kohl. F. J.. and Steams. C. A,. Enhanced Oxidation Vaporization of Cr203 and Chromium by 

Chjgen Atoms. J Electrochemical Socieh Solid-State Science and Technologr, vol. 121. no. 7. July 1974. pp. 

957-959. 

5. Schaefer. J. W.. Tong. H.. Clark. K. J.. Suchsland. K. E., and Neuner. G. J.. Analytic and Experimental 

Evaluation of Flowing Air Test Conditions for Selected Metallics in a Shuttle TPS Applications. NASA CR2531. 1975. 

6. Tennej. D. R.. Young. C. T.. and Herring, 13. W.. Oxidation Behavior of TD-NiCr in a Dynamic Oxidation 

High Temperature Environment. Mefnllwrgicml Trnnsacfions. vol. 5, May 1974. pp. 100 1-1 023. 

0900148 doc 












0 

I 0 

i T 0 

s 

8 

I 

I 



















Elimination of Carbon Tetrachloride 

for Quantitative Hydrocarbon Analysis 

Vonnie M. Douglas 

The Boeing Company 

Rocketdyne Propulsion & Power 

6633 Canoga Avenue 

Canoga Park, CA 9 1309-7922 

ABSTRACT 

The elimination of ozone depleting substances, such as carbon tetrachloride, has resulted in the use of new 

analytical techniques for cleanliness verification and contamination sampling. The last remaining application at 

Boeing Rocketdyne which required a replacement technique was the quantitative analysis of hydrocarbons by 

infrared spectrometry. This technique, which previously utilized carbon tetrachloride, was successfidly modified 

using the SOC-400, a compact portable FTIR manufactured by Surface Optics Corporation’. This instrument can 

quantitatively measure and identi9 hydrocarbons from solvent flushing of hardware as well as directly analyze the 

surface of metallic components without the use of ozone depleting chemicals. Several sampling accessories were 

evaluated to perform hydrocarbon analysis for various applications. 

BACKGROUND 

Prior to 1996 carbon tetrachloride was used in the laboratory for extractions and for standard preparation, 

sample dilutions and as a pick up solvent for Fourier transform infrared (FTIR) techniques. It was also utilized as a 

flush solvent for hardware cleanliness verification procedures, including non-volatile residue (NVR), handwipe 

applications and particle count determinations. Cyclohexane gravimetric NVR and Total Organic Carbon (TOC) 

analysis replaced many of the cleanliness verification techniques which utilized carbon tetrachloride. Cyclohexane 

and Soxhlet extractions utilizing CO? were used as alternatives to many laboratory applications. 

Cleanliness verification of smaller sized hardware and wipelswab analysis still utilized carbon tetrachloride 

for hydrocarbon determination. Certain hardware was incompatible with the TOC technique due to the electrical 

connectors and other parts did not contain a large enough surface area to be used with gravimetric methods. Wipes 

and swabs were extracted with cyclohexane, but still required quantitative techniques that could attain the low 

detection limit provided by FTIR methods. During these analyses, an aliquot of the final flush solvent was collected 

and evaporated to dryness. The remaining residue was taken up in a known quantity of carbon tetrachloride and was 

subsequently analyzed on an infrared spectrometer. A technique was required to achieve the required detection limit 

of 1.0 mgift’ without the use of ozone depleting chemicals. 

An analytical procedure was investigated which involved evaporating cyclohexane directly onto a sampling 

device followed by subsequent analysis of the residue using a FTIR spectrometer. This would eliminate the need for 

carbon tetrachloride as a pick-up solvent. New programs, new cleaning facilities and the goal to reduce cycle time 

also led to the investigation of surface analysis techniques for cleanliness verification. The same instrument 

evaluated for quantitative hydrocarbon analysis was also evaluated as a surface analysis tool for several 

applications, including wax removal and cleanliness verification of specific hardware. 

INTRODUCTION 

Historically, quantitative analysis using FTIR techniques involved the following steps. 

1 ) 

2) 

3) 

4) 

5) 

Cyclohexane was obtained from hardware by flushing or from wipe extractions. 

The solvent was evaporated to residue. 

Remaining residue was picked up in carbon tetrachloride. 

The carbon tetrachloride solution was transferred into a quartz cell. 

Hydrocarbon analysis by FTIR was performed on the carbon tetrachloride solution. 
The proposed FTlR method utilized a portable spectrometer, Model SOC-400, manufactured by Surface 

Optics Corporation. The unit contains an integrating spherical adapter, referred to as a V-sphere. designed 

specifically for this application. The V-sphere is a hemispherical gold plated container, which attaches directly to a 

niatching hemispherical part on the main unit. When the two hemispheres are attached by threaded closures a 

complete sphere is formed. The infrared beam enters through a small hole from the detector side of the sphere and is 

reflected off of the sampling hemisphere. which contains the sample residue. The beam is reflected many times 

within the sphere. which amplifies the signal and increases sensitivity before reaching the detector. The instrument 

measures data collected over the entire hemispherical area for any set of incident or reflected angles. 

The portability of the unit is an added feature, but was not deemed as important as the sampling devices 

available for analysis. The advantage of the V-sphere accessory is that the solvent can be directly evaporated into 

the sample holder. The sampling device has a capacity of 5 ml, which allows easy transfer of the solvent. This 

minimizes sample loss and decreases analysis time when compared to other methods. 

The SOC-400 also has the capability of detecting organic contaminants directly on metallic surfaces using 

specular, diffuse and grazing angle measurement heads. The IR beam from the unit illuminates the sample outside 

the instrument. The incident beam from the FTIR is reflected into specular and diffuse beams which are then focused 

onto the detector, collected and analyzed. The beam of infrared light penetrates a thin layer of a contaminant on the 

inspected surface and part of the beam is absorbed by the molecules of the contaminant. The amount of absorbed 

energy changes with illuminating energy and each polyatomic molecule produces its own characteristic infrared 

spectrum. Therefore this technique has the ability to identify as well as quantify a given contaminant. A feasibility 

study was conducted on the capability of this technique using the three measurement heads on various surface 

finishes. 

V-SPHERE TESTING 

Qualification testing was performed utilizing the SOC-400 with the gold plated integrating spherical 

sampling accessory (V-sphere). This technique involved evaporating solvent onto the V-sphere and analyzing the 

remaining residue with an SOC-400 FTIR spectrometer. Mineral oil standards were prepared in cyclohexane and 

evaporated directly onto the sampler. A calibration curve was obtained from 0.0 1 mg to 0.5 mg. See Figure 1. An 

infrared absorption spectrum was obtained between 3000 cm-1 and 2800 cm-l wavenumbers. Sixty four (64) scans 

at 8 cm- 1 resolution were obtained. 

Figure 1. 

SOC1-400 V-Sphere Calibration 

.7 

.6 

.5 

C 9 

; .4 

n 

4 

Hydrocathon Sfsncloros 

<!.SO my 

0.25 Rg 

.3 

.2 

.I 

0 

3200 31 50 31 00 3050 3000 2950 2900 

Wavenumber (cm-1) 

2850 2800 
Initial calibration results indicated that two sets of calibration data were required to cover the needed range 

of 0.0 1 to 1.0 mg. This was demonstrated by high recoveries (200 percent) in the lower concentration range. See 

Table 1. Each set of calibration data consisted of 5 points, the lower ranging from 0.01 to 0.25 mg and the higher 

from 0.05 to 1.0 mg. With the two sets of calibration data, the lower concentration recoveries decreased to an 

acceptable range. See Table 2. 

Average 

Std. dev. 

A know volume and concentration of contaminant in cyclohexane was placed in the V-sphere and allowed 

to evaporate. After the solvent was evaporated to residue the V-sphere surface was analyzed. The contaminants and 

contaminant mixture are described in Tables 3 and 4. See Table 5 for results. 

0.010 I 100 0.020 I 100 0.049 I 98 0.100 I 100 0.239 I 96 0.487 I 97 0.938 I 94 

0.011 I 110 0.019 I 95 0.051 1 102 0.100 I 100 0.249 I 100 0.511 I 102 0.912 I 91 

117 98 100 102 96 101 100 

10.3 4.2 1.5 2.1 1.7 2.8 6.2 

Hydrocarbon standards were concentrated in a small area of the spherical V-sphere surface and compared to 

hydrocarbons spread evenly over the entire surface. The goal was to determine if the recovery would vary with the 

thickness of the residue remaining in the V-sphere. Mineral oil standards in cyclohexane were evaporated into the 

V-sphere such that 0.1 mg residue would remain in the V-sphere, while the volume. and thus the area covered by 

contaminant, varied from 0.1 to 5.0 ml. The results indicate thickness of the residue does not significantly effect 

recoveries. See Table 6 for results. 

Table 1. 

Mineral Oil Recovery 

Obtained using One Set of Calibration Data 

I Recovery IAmount Appliedl Recovery I 

Table 2. 

Repeatability Test Results Using Two 

Sets of Calibration Data 

I Mineral Oil I 
Table 3. 

Contaminant Description 

Contaminant 

Mineral Oil 

Mil-H-83282 Hydraulic Fluid 

Spinnestic 22 Oil 

Paraffin Wax 

Rinidnr 

Description 

Light paraffin oil 

Synthetic hydrocarbon fluid containing triphenyl phosphate 

Petroleum lubricating oil 

Low melting wax 

Hioh meltino wax 

Contaminant 

Rapid Tap 

Mil-H-83282 ydraulic Fluid 

LSlO 

Bio-Pen P6F4 

Turco 4215 Additive 

percentby 

WgM Manufactwer Description 

43.7 Relton Lubricant, mntaining mineral oil. paraffin and soybean oil 

3.9 BFayoilCo. Synthetic hydrccartjun fluid containing biphenyl phosphate 

3.7 ITW Fluid Products Gmp Fatty alcohol based lubricant 

3.5 Ardox Inc. Fluorescent, water-sduble dye penetrant 

5.2 Elf AIochem, Turco Products ether and nonnyiphenoxypdy (ethyleneoxy) ethanol 

bionic detergent, containing diethylene glycol mobutyl 

Spinnestic Oil 

Parrafin Wax 

0.50 0.40 80 

0.5 0.42 84 

0.25 0.23 92 

0.035 0.03 86 
Table 6. 

Effect of Residue Thickness 

So Ive n t Amount 

Volume Contaminant Detected 

(ml) (mg) (mg) 

0.1 0.10 0.1 05 

Recovery 

Percent 

101 

90 

SURFACE ANALYSIS APLICATIONS 

The SOC-400 was used in a feasibility study to detect organic contaminants directly on metallic surfaces. 

Three types of measurement heads were utilized on various surface finishes. This technique, if proven effective, 

could provide a rapid method of verifying surface cleanliness on precision cleaned hardware. The goal was to 

determine the feasibility of using SOC-400 surface analysis techniques for cleanliness verification. 

A test plan was developed, but prior to implementation, the following tasks were required: 

Identify test coupon substrates which would be consistent with production hardware surfaces 

Determine method of contaminant application 

1. 

2. Fabricate test coupons 

3. 

Coupons were fabricated from 0.016” thick 718 Alloy. The coupons were 4.8” x 3.0 ‘‘ (0.1 sq. ft). Four surface 

finishes representative of production hardware were obtained as follows in Table 7. 

Table 7. 

CouDon DescriDtion 

Surface Treatment 

I Untreated material 

I 2 IGlass bead, grit blasted 

3 fHeat treated in air. then arit blasted 

L 4 IHeat treated in vacuum Dark color, smooth surface I 

Initially contaminants were applied to the coupons using a cleaned syringe. A known volume of a known 

concentration was applied to a one sq. cm surface area. However it was observed visually and analytically the 

technique was not providing a uniform layer of contaminant. Since the FTIR only analyzes a 2 mm surface area, 

large variations in the results were observed when analyzing different locations within the contaminated area. A 

more precise technique of applying contaminant was required. 

An air brush sprayer was then utilized to apply the contaminant. The contaminant was diluted in 

cyclohexane and sprayed onto a coupon. The amount applied was determined by weight difference. This technique 

resulted in a much more uniform coupon and was also being used by other industries for similar applications. A 

limited amount of variation was still observed on the coupons. This was overcome by taking more samples on each 

coupon. Initially only 3-5 areas on each coupon were analyzed. It was determined that by averaging 10 spots on each 

coupon, more reliable results could be obtained. 
SURFACE ANALYSIS TEST RESULTS 

A calibration curve was run using mineral oil in cyclohexane with the diffuse reflectance head on coupon 

Set 2 (grit blasted, no heat treat). See Figure 2. The calibration curve was used for quantitative comparison of the 

various surfaces. See Table 8 and Figures 3-6. The recoveries appear much higher on the more reflective surfaces 

due to high background noise. Average percent recoveries for 5 to 10 mg/sq. ft coupons on the various surface types 

were 720.90.55 and 2 10 percent on coupon Sets 1.2.3 and 4 respectively. This indicates good recovery on the 

coupons used for the calibration curve, low recoveries on the most difise surface and high recoveries on the most 

reflective surfaces. The difference in recoveries indicate that the SOC-400 is more sensitive to certain surface 

finishes and implies that surface finish plays a large role in the detection capabilities of the instrument. 

Mineral Oil Calibration Curve 

on Grit Blasted Inconel Coupon5 

40 ~,..~ ..._._._.__.I.__...I._..._..___I_I ____I-I_. . . . . 

01 1 

0 20 40 6C 

Amount Applied (mg/.q.ft) 

Figure 2. Calibration Curve for Coupon Set 2 

MIn~raI MI RecomIy 

on GM Blasted Incowl CoUpQn (W 2) 

I my.q R. Wd 

, . .. ... , ,.,.. .,.,.. .., . ,11 ~ II l__l-llll. ............,_I ~. .- I ..... I .............I ,..... ".lll 

L I.- Figure 4. Mineral Oil Recovery on Coupon Set 2 

'. 
Hlneral Oil Recovmy 

on Heai Tnsled. GM Blasted Inconel (Set 3) 8 md q FI 4ppld 

Figure 5. Mineral Oil Recovery on Coupon Set 3 

Mineral Oil Recovery 

on Heat Trnaied Inconel Coupons (Set 4) 

13 -ma A+ 

10 1.. ... . . . . .... . ... . . . . . . . ....I ..... ...I I ....l._.ll l.l..l ,... I. . .. .. . ...... . .. ... ....... __ . . . ,. ... ......."."........I ~ ..... . 

-.d 

Figure 6. Mineral Oil Recovery on Coupon Set 4 

BTIR Accessories 

purpose of the grazing angle is to enhance the detection capability of the instrument on more specular substrates. 

This is done by simply changing the angle of the incident beam coming from the IR source. An added benefit with 

the grazing angle accessory is that a larger spot size is analyzed. An elliptical area approximately with major and 

minor axes of 1 and 0.25 inches is analyzed as opposed to the 2 sq. mm area using the difise or reflectance head 

accessories. 

A grazing angle measurement head has just recently become available from the SOC-400 manufacturer. The 

Coupons were analyzed using grazing angle, difise head and reflectance head accessories. The difhse 

head gave the highest peak intensities. The specular head had a comparatively lower intensity and a higher noise 

level. The grazing angle had lower intensity, but also lower noise. The fact that the noise level was lower with the 

grazing angle proved to be an added benefit for lowering detection limits. 
Coupon/Surface 

Treatment 

1 

Untreated material 

Averagc 

2 

Grit blasted material 

Average 

3 

Heat treated in air, 

then grit blasted 

Average 

4 

Heat treated 

in vacuum 

Average 

Table 8. 

Diffuse Measurement Surface Ana 

Amount 

Applied 

[mg/sq. ft.) 

6 

4 

6 

7 

Amount 

Detected 

(mglsq. ft.) 

19.1 

20.2 

20.6 

9.9 

14.4 

18.4 

26.5 

20.1 

21.5 

20.9 

19 

5.1 

4.1 

3.1 

5.5 

3.8 

2.5 

4.0 

2.1 

2.8 

4.7 

3.8 

4.6 

2.7 

4.5 

3.5 

3.7 

2.9 

3.4 

3.9 

2.9 

3.9 

2.8 

13.5 

21.7 

13.3 

17.2 

20.0 

7.04 

11.1 

9.3 

11.9 

14.6 

14 

Percent 

Recovety 

31 8 

337 

343 

1 64 

240 

307 

442 

335 

358 

348 

31 9 

128 

103 

78 

138 

95 

63 

1 00 

53 

70 

118 

94 

115 

45 

75 

58 

62 

48 

57 

65 

48 

65 

47 

193 

31 0 

190 

246 

286 

101 

159 

133 

170 

209 

199 

sis Results 

Amount 

Applied 

[mg/sq. ft.) 

8 

9 

8 

13 

Amount 

Detected 

Jmg/sq. ft.) 

30.7 

24.9 

33.8 

35.3 

33.0 

32.0 

26.6 

23.2 

25.6 

31 .O 

30 

7.3 

5.4 

7.9 

8.1 

9.2 

7.8 

5.6 

4.9 

10.9 

8.2 

7.5 

4.4 

7.7 

7.5 

4.8 

4.1 

5.2 

4.7 

6.9 

3.9 

5.7 

5.5 

25 

22 

34 

22 

22 

15 

26 

9 

11 

18 

20 

~~~~ 

Percent 

Recovery 

34 1 

277 

376 

392 

367 

356 

296 

258 

284 

344 

329 

81 

60 

88 

90 

102 

87 

62 

54 

121 

91 

83.7 

55 

96 

94 

60 

51 

65 

59 

86 

49 

71 

68.6 

189 

171 

262 

168 

168 

116 

197 

70 

85 

137 

156 
A set of twelve coupons contaminated with 0.5 to 2.0 mg/ft’ of mineral oil was analyzed by grazing angle, 

diffuse and specular FTIR . The diffuse and specular measurements could only detect contaminants at the highest 

concentration, 2 mgift’. The grazing angle was much more sensitive and could detect hydrocarbons at 0.5 mg/ft’ on 

all but one surface. The grazing angle could not detect hydrocarbons on the most diffuse surface, coupon Set 3-heat 

treated in air, then grit blasted material. 

Other manufacturers have developed FTIR units with a grazing angle accessory in conjunction with fiber 

optics. Remspec * makes a unit which contains a detector connected at the end of the fibers which is in direct contact 

with the surface being analyzed. This increases the sensitivity without losing signal through the fibers. One 

disadvantage to that unit is the grazing angle accessory is approximately 5 x 6 inches and is rather bulky to be used 

on many hardware configurations. The advantage is this unit can analyze a spot size approximately 6 sq. in.. which 

can reduce the problems associated with analyzing inhomogeneous contamination. 

WAX REMOVAL APPLICATION 

The SOC-400 was evaluated for surface cleanliness verification of the SSME Main Combustion Chamber 

(MCC ) after wax removal operations. The MCC contains many slotted channels which were considered the most 

likely areas to trap contamination. Slotted channel coupons and an actual (scrap) SSME MCC liner were utilized to 

evaluate the portable FTIR for detection of residual hydrocarbons. Tests were performed using 3 x 5 inch copper 

coupons 0.5 inch thick containing 15 slots each of width 0.065 inch and depth 0.45 inch. See Figure 7. 

The SOC 400 was modified by placing a raised slot 0.040 inches wide in the plastic faceplate. This slot 

aligned the instrument to be able to analyze hydrocarbons in the slotted channels. This arrangement was used for the 

rectangular coupons and for the scrap MCC. About half the channels in each slotted coupon was contaminated with 

wax by rinsing channels with a solution of yellow Rigidax in cyclohexane. The SOC-400 was easily able to 

distinguish between the contaminated and uncontaminated slots. 

Efforts to produce a calibration curve for wax in the slotted coupons have thus far been unsuccesshl, 

primarily to the difficulty of applying a uniform coating of hydrocarbons on the inner surface of a slot. Both soaking 

and spraying of a cyclohexane solution of Rigidax yellow wax into the slots were tried with limited success. 

Analyzing a clean MCC was also performed. The SOC-400 was placed on an adjustable tripod as shown in 

Figure 8. Data collection took about 30 seconds per location and those results were compared to conventional 

cyclohexane rinsing of the slots. Conventional cyclohexane rinsing of the slots followed by FTIR analysis indicated 

the level of cleanliness was less than 1 .O mg/ft’ within the slots. Qualitatively, use of the SOC-400 FTIR detected 

the presence of small amounts of hydrocarbons within the slots as well as other contaminants, possibly cleaning 

agents. This was confrmed by X-ray Photoelectron Spectroscopy (XPS) analysis of the coupons. More work is 

needed to confirm that a quantitative assessment of cleanliness within a slotted channel can be reliably made. 

CONCLUSIONS 

The V-sphere technique was shown to be an acceptable method for the hydrocarbon analysis and the 

process has been implemented successfully at Rocketdyne. Because the new method utilized similar analytical 

techniques as the previously used method (both used FTIR techniques), the implementation and qualification was 

much easier than that of an entirely new analytical technique. 

‘More work is required to determine if surface analysis is a viable technique at Rocketdyne. Preliminary 

results indicate that the required detection limit can be achieved using a grazing angle accessory, but sensitivity is 

dependent on surface finish. A determination of how many areas must be analyzed to confirm cleanliness of an entire 

part will also be required and will most likely be part specific. Because the surface finish vanes from part to part, it 

is doubthl this technique will be widely used for cleanliness verification. However, it may be a usefil tool for select 

hardware applications and contamination analysis. The SOC 400 FTIR is being used successfully at other Boeing 

locations for various surface analysis techniques. 

’ Remspec Corporation, Charleston, MA. See http://www.remspec.com 
+I I 

View fLom top 

-I 1 , t II I ,111, 

I4 

lI1~iO111 urh 

Cross section 

Figure 7. Slotted Coupon 

Figure 8. Surface Analysis of SSME MCC 

ACKNOWLEDGEMENTS 

techniques and also expresses gratitude to Sarah Kipp for performing laboratory analysis in support of this project. 

Special thanks to Martin Szczesniak at Surface Optics and Paul Shelly from Boeing Seattle for performing additional 

analyses and providing technical support. 

The author would like to recognize Larry Hill for his contributions in the development of the infrared 
,- ,’ 

i 

ELLIPSOMETRIC VERIFICATION AND EVALUATION OF CLEAN SURFACES 

Wayne Thompson 

The University of Alabama in Huntsville 

Center for Automation and Robotics 

NASA Surface Contamination Analysis Technology Team 

UAH, R.I. Room M-62A 

Huntsville. Alabama 35899 

Thornps~~~~.t.m,iii.uail.fdu 

256-890-628 1 

Introduction 

As precision cleaning techniques become more critical to the Aerospace Industry, good methods of 

verifying and evaluating those techniques become more important. Precision cleaning can often mean contamination 

thickness on the order of molecular diameters. Therefore, inspection instrumentation must be extremely precise. 

Ellipsometers provide the measurement capability necessary to determine the contamination of ”clean” surfaces to 

within a few molecular diameters. 

This paper is an introduction to how ellipsometry plays a vital role in the verification and evaluation of 

“clean” surfaces for NASA’s Surface Contamination Analysis Technology (SCAT) Team. 

Clean Surfaces 

To those in the field of non-contact measurement, a “clean” surface implies that no other molecules can be 

present on a surface other than the surface’s material itself, or that material’s native oxide. Of course this also means 

that very few surfaces are actually “clean”. Ellipsometry is one of the main tools used by NASA’s Surface 

Contamination Analysis Technology Team verify that a surface is indeed clean or not. 

The Ellipsometer 

The ellipsometer is a non-contact measurement instrument that measures electromagnetic properties of 

light to derive optical constants for materials or to derive the thickness of thin films, or in this case, contamination 

layers. The physical aspects of the ellipsometer’s measurements are shown in figure 1. 

1YonnaltoUm?rurhce 
The EP and Es light polarization vectors correspond conceptually to the E and B fields of a propagating 

electromagnetic wave. The Ep and Es wave components are always perpendicular to one another and have varying 

lengths or amplitudes. At any instantaneous moment the ratio of their amplitudes geometrically describes the form 

of an ellipse. hence the temi "ellipsometer". Most light is elliptically polarized. In circularly polarized light (a 

special case of elliptically polarized light), the EP and Es wave components have equal amplitudes. 

The ellipsometer uses the detection of these EP and Es wave component amplitudes through the equation: 

where Psi (w) and Delta (A) are the amplitude ratio and phase shifi, respectively, of the P and S components of the 

light wave. rp and rs. the amplitudes of the reflected wave components, are the actual quantities measured by the 

ellipsometer. From the Psi and Delta data, the index of refraction, the coefficient of extinction, and/or the thickness 

of a thin film can be derived. 

The ellipsometer used by NASA's SCAT team is a J.A. Woollam VASE system as shown below in figure 

2. 

Figure 2 

VASE stands for Variable Angle Spectroscopic Ellipsometer. By varying the incident angle and the 

wavelength of light, the system is able to generate very precise measurements. The J.A. Woollam company states 

that the tolerance (or noise level. as it is often referred to) is k 5 Angstroms (f 5 x lO-''m). However, in house 

variance measurements on a typical silicon wafer show even better performance of less than Ifr 3 Angstroms. Three 

Angstroms is actually less than the molecular diameter of an H20 molecule. This allows for the detection of 

monolayer contaminants like H2O. 
Verification of Clean Surfaces 

Many of NASA’s scientific endeavors depend upon the absolute highest quality of fabrication for its space 

flight optics. This entails detailed clean assembly procedures within stringent clean rooms. One of the ways that 

NASA verifies the cleanliness of its procedures is via a “witness mirror”. This type of verification is achieved by 

placing a standard electronics industry silicon wafer, the “mirror”, in close proximity to the fabrication to be 

“witnessed”. Periodically these witness mirrors will be sent to NASA’s Surface Contamination Laboratory for 

verification 

Examples of this are the witness mirrors that were used in NASA’s XRCF project (X-ray Calibration 

Facility). The witness mirrors are base-lined on the SCAT team’s J.A. Woollam VASE ellipsometer before it is 

placed within the XRCF chamber. At pre-determined intervals those mirrors come back for comparison with their 

baselines. If there is little change in the Psi and Delta data, then it may be concluded that the mirror is clean 

implying that the assembly area is free from airborne contaminants that could deposit on critical optics. However, if 

there is substantial difference between the baseline data and the verification data, then the critical space flight optics 

could be in danger of contamination and measures must be taken to ensure a clean environment for the hardware 

assembly. 

The following data shows particular cases when a monolayer of contamination was indicated on XRCF 

witness mirrors. Baseline data is shown below (figures 3 and 4). 

Generated and Experimental 

0.81 I 1 I I 

600 700 800 900 loo0 

Figure 3 WaAength (nm) 

Generated and Experimental 

Figure 4 Wajelength (nm) 
The next plots show Psi and Delta data for the same wafer after a time in the XRCF chamber. Also on the 

plot is a fitted model for the baseline data that shows how the data sets differ, indicating the possibility of 

contamination (figures 5 and 6). 

2.7 

2.4 

i 2.1: 

k 1.8- 

$ 1.5- 

1.2- 

0.9 

-0 

C 

I I I 

- Modei Fit - FgE75” 

- 

- /’ 

4 - 

‘. - 

I I I 

Generated and Experimental 

140 

120 

100 

8 

280 

F 

c 

4 

.- 

40 

20 

0 

600 700 800 900 

Figure 6 WdWh (m) 

By adding an additional layer of SiOl to the baseline model and fitting the layer’s thickness and optical 

constants, an estimation of the possible contamination layer’s thickness is achieved (table I ). 

2 sa 5.8678 A 

1 sic2 41.507 A 

OSi Im 

Table 1 

The following plots show how this solution now fits the data that indicates a contaminant on the wafer 

(figures 7 and 8). 
Generated and Experimental 

2.7 I I I 

2.4 - Modd,fit " - SWpE 75" 

v) 2.1- 

2 

? 1.8- 

a, - 

U '\ 

c 

- 

1.5-\ - 

1.2- - 

0.9 I 1 I 

\\. , 

, '\ 

Generated and Experimental 

Another example of this (using just the Psi data) shows another indication of a possible layer of 

contamination on an XRCF witness mirror (figure 9). 

Generated and Experimental 

Once again the figure shows a few degrees discrepancy with the baseline data, indicating the possibility of 

contamination. Adding a contamination layer to the baseline model and fitting it gives an indication of a possible 

contamination layer (figure IO). 
2.7- 

2.4 

$ 

E! 2.1- 

T- 

- 

I2 si02 7.mA I 

Model Rt ‘ - - __ 

EWE 75” - 

- 

I1 sa 20.719A I 

I o si ’ml 

Table 2 

So here again we have indication of a very thin layer of contamination on the witness mirror (table 2). 

This type of cleanliness verification is very valuable to NASA’s optical fabrication efforts. And, with the 

VASE ellipsometer, it is easy. 

Evaluation of Cleaned Surfaces 

Another service that ellipsometry has provided in the realm of precision cleaning, is an assessment of 

cleaning methods. Considering the instrument’s precision, it may be one of the best methods available for this type 

of assessment. 

The general procedure for a precision cleaning assessment is to baseline a set of sample surfaces (in this 

case, standard silicon wafers), then clean them normally with the cleaning methods of interest, and then use the 

ellipsometer to solve for any residue thickness. The residue thickness results from modeling the cleaned samples 

will allow for a comparison between methods, and the method that leaves the least amount of residue can be chosen 

for a particular application. 

NASA’s SCAT team performed a cleaned surface evaluation on several common laboratory solvents 

including some standard laboratory wipes and gloves. The solvents used for the study were acetone, ethanol, 

isopropanol, methyl-chloroform, and 1 - 1-2 trichloroethane. 

All of the 2-inch standard silicon wafers were base-lined from a new, pristine state and then contaminated 

according to four types of contamination: solvent flush, solvent soak, solvent wipe, and solvent rinsed glove print. 

Once contaminated and stored in a new, sealed container, the samples were transferred to the ellipsometer for 

scanning. After scanning, the “cleaned” sample data was modeled and residue thickness was derived. A set of three 

wafers was averaged for each sample set. 

The solvent flush contamination consisted of using three wafers per solvent and placing them on vacuum 

wands at roughly a 45” incline to allow for solvent run-off. Each wafer was then flushed with approximately 20-ml 

of solvent and allowed to dry before scanning. The following chart shows the results of the flush test after averaging 

(figure I I ). 
Solvent Flush Residues 

Angstroms 

acetone chloroform ethanol isopropanol 1.12 

Figure 1 1 

It is clear from the chart that ethanol leaves the greatest residue in this flush-type cleaning operation. 

A similar test was used to investigate the residuals left by a soaking-type operation where the wafers were 

left horizontal on the vacuum wands and the solvents were allowed to evaporate after covering the wafers with 

solvent. The following chart illustrates these results after averaging (figure 12). 

Solvent Soak Results 

Angstroms 

acetone chloroform ethanol isopropanol 1.1,2 

Figure 12 

Here again, ethanol leaves the most residue. This is likely due to its hydroscopic nature. It is important to 

notice the scale of residual thickness here: Angstroms. The residues left are very thin. Residues indicating a 

contamination thickness of less than 3 Angstroms are more likely to actually be a change of surface quality rather 

than a contamination layer. However, this can still be helpful in choosing precision cleaning techniques by 

indicating which solvent or procedure has the least effect on the surface. 
Quite frequently a laboratory or manufacturing cleaning issue needs to involve the use of a wipe. The 

SCAT team’s study extended the investigation of the solvents to include five of the wipes that were easily found 

around the laboratory. The wafers were once again mounted on the vacuum wands horizontally and then wiped with 

a solvent impregnated wipe. The following chart shows the results of the solvents as averaged over the five wipes 

(figure 13). 

The averages of the ellipsometric results show that, from this data, for wipe-cleaning operations in general, 

acetone may be the best bet. 

Average of Wlpes for each Solvent 

Figure 13 

Angstltrc 

Acetone Chloroform Ethanol Isopropanol 1.1.2 

The same procedure was performed for a solvent-use-with-gloves scenario. Wherein, the gloves 

were rinsed with solvent for approximately 10 seconds and then a side-to-side print was applied to each wafer. 

Again. three wafers were averaged to obtain a single result. The following chart shows the results of the solvents 

\vhen averaged over the gloves (figure 14). 

From the glove results it can be seen that, if a cleaning operation is necessary where gloves are in sustained 

Average of Gloves for each Solvent Figure 14 

Acetone Chloroform Ethanol Isopropanol 1.1.2 
contact with solvents, then this data indicates that acetone may be the best choice again. 

Conclusion 

Currently in use at NASA’s Marshall Space Flight Center, Space Environmental Effects Group - Surface 

Contamination Analysis Technology Team, Variable Angle Spectroscopic Ellipsometry offers one of the better 

ways to verify and evaluate surface cleanliness. It is one of the few methods that can resolve monolayer 

contaminants with a non-contact measurement. 
- 

K./ 3 / 

Improved Detection Technique for Solvent Rinse Cleanliness Verification 

Steven D. Hornung 

Honeywell Technology Solutions Inc. 

NASA Johnson Space Center 

White Sands Test Facility 

Las Cruces, New Mexico 

Harold D. Beeson 

NASA Johnson Space Center 

White Sands Test Facility 

Las Cruces, New Mexico 

The NASA White Sands Tcst Facility (WSTF) has an ongoing effort to reduce or eliminate usage of 

cleaning solvents such as CFC-I 13 and its replacements. These solvents are used in the final clean and cleanliness 

verification processes for flight and ground support hardwarc, especially for oxygen systems where organic 

contaminants can pose an ignition hazard. For the final cleanliness verification in the standard process. the 

cquivalent of one square foot of surface area of parts is rinsed with the solvent, and the final 100 mL of the rinse is 

captured. The amount of nonvolatile residue (NVR) in the solvent is deterniincd by weight after the evaporation of 

thc solvcnt. An improved process of sampling this rinse, developed at WSTF, requires evaporation of less than 

7 mL ofthc solvent to make the cleanliness verification. Small amounts ofthe solvent are evaporated in a clean 

stainless steel cup, and the cleanliness of the stainless steel cup is measured using a commercially available surface 

quality monitor. 

The effectiveness of this new cleanliness verification technique was compared to the accepted NVR 

sampling procedures. Testing with known contaminants in solution, such as hydraulic fluid, fluorinated lubricants, 

and cutting and lubricating oils, was performed to establish a correlation between amount in solution and the process 

response. This report presents the approach and results and discusses the issues in establishing the surface quality 

monitor-based cleanliness verification. 

5.4 CKGR 0 L 'ND 

Cleaning operations at WSTF encompass support for materials, components, propulsion test systems, and a 

sizeable shuttle depot activity. As part of these operations, components and piece parts are cleaned for a variety of 

sewices including oxygen, hydrogen, hydrazines. and nitrogen tetroxide. Most of these parts are constructed of 

stainless steel and are resistant to corrosion in aqueous media. For prccision cleaned parts, the standard cleaning 

process consists of two major elements: an aqueous precleaning process and a solvent-based final cleaning and 

cleanliness verification. Cleanliness levels are specified by a number that has an associated number of particles at 

this maximum size in micrometers followed by a letter to specify the maximum residue allowed on I ft' of surface 

ma. The letters A. B. C, and D refer to I, 2, 3, and 4 mg of residue, respectively. Cleanliness levels to 50A are 

required for high-pressure oxygen service. Following the aqueous precleaning. the parts are dried, visually 

inspected. and if passed, arc transferred to the Class IO0 clean room. The accepted process for solvent-based final 

cleaning and NVR determination using HFE 7 I00 is shown in Figure 1. The components to be cleaned are rinsed 

aith HFE 7 100 in the vapor degreaser followed immediately by a sampling rinse of approximately 100 mL/ft' of 

component surface area. This rinse is then filtered for a particulate count and then submitted for NVR 

determination. The components are then blown dry with nitrogen. packaged, and labeled for use. 
Figure 2 shows the steps in obtaining the NVR from the solvent rinse. First the solvent is transferrcd to a 

boiling flask, and the volume of the solvent is reduced to I0 to 15 mL by distillation. The solvent trapped in the 

distillation by a condenser is recycled. The remaining 10 to I5 mL IS transferred to a tared weighing pan and placed 

in a 100 "C oven for 30 min to complete the drying. The weighing pan is allowed to cool in a desiccator before 

weighing again to determine the NVR. For HFE 7 100, the process takes approximately 40 inin. It should also be 

noted that some of the more volatile contaminants could be volatilized, especially during the 30 inin drying in the 

oven. Light hydrocarbons can show 40 percent NVR recovery or less from spiked solvent samples. 

An iinprovcd cleanliness verification process that replaces the current NVR procedure makes use of a 

cominercially available surface quality monitor. This monitor measures the photocurrent produced froin a sample 

when it is exposed to ultraviolet light. The photocurrent magnitude depends on surface characteristics. A clean 

metal surface will give a high photocurrent while an organic compound will give a much lower photocurrent or 

photoelectron yield. For example, a clean stainless steel surface will give up to IO times the photocurrent of an 

organic compound. And because photoelectrons can escape froin only the top few atomic layers, this measurement 

technique is very sensitive to thin layers of organic contaminants on metals. A photograph of the surface quality 

monitor (SQM) is shown in Figure 3. 

A PPROA CI I 

The testing used to certify the SQM cleanliness verification process was divided into two phases: proof-ofconcept testing and process validation. In the proof-of-concept phase, the feasibility of the technique was evaluated, 

and variables such as aliquot size, evaporation temperature, and distance from the probe were investigated to 

determine the optimum setting for a production test. Several different contaminants were also tested with 

concentrations ranging from 0.5 to 2 mg per 100 niL of solvent to dcterrnine the sensitivity and detection limit of the 

technique. These 100 mL solutions are analogous to the 100 mL solvent verification rinse, and it is assumed that ai! 

contaminant on a surface would be taken into solution by the solvent rinse. These solutions were mixed well upon 

preparation and were assumed to be a true solution rather than an emulsion. No homogenization of the solution was 

made before sampling with the SQM. 

HFE 7 100 Final 

Clean Rinse 

I 

Filter for 

Particle Count HFE 7 100 Rinse 

Nitrogen Blow 

I 

Package and 

Label 

Evaporate for I NVR 

Figure 1 

Solvent Final Cleaning and Verification Process 
to IO to I5 IIlL 

Remo\ e trom 

O\en and Cool 

U eigh tor Y\'R 

Figure 2 

NVR Process for Cleanliness Verification 

Figure 3 

SQM 200 Surface Quality Monitor 

Process validation uas performed to determine the reliability of the process on a production scale and the 

frequency of false pass or false failure as compared with the standard HFE 7100 NVR. Sampling was performed on 
actual cleanliness verification rinses from WSTF cleaning processes. In this parallel sampling, 2.3 inL of the 100 

tnL for the standard HFE 7100 NVR was removed for testing with the SQM-based technique, and the remainder was 

evaporated by the standard NVR technique. In addition, 40 samplcs of HFE 7100, spiked with selected 

contaminants at concentrations ranging from 0.25 to 2.0 mg/I 00 mL, were submitted for parallel sampling. Results 

from the SQM-based cleanliness verification were compared with the results from the standard NVR method. 

Proof-of-Concept Testing 

Proof-of-concept testing wab performed to determine the response of the technique to varying levels of 

contaminants dissolved in HFE 7100. Test solutions were prepared by dissolving 2 mg of Krytox 240 AC or Duo 

Seal oil contaminant in 100 mL of HFE 7100. At least IO tests were performed for each Contaminant and 

concentration. First, the photocurrent was measured from a clean cup; a reading of at least 400 was required before 

the test could proceed. Using the same cup, a 0.3 mL aliquot of the contaminated solvent was placed in the cup. 

The cup was then heated to 40 "C on a hot plate until the solvent evaporated, approximatcly 1 niin. After the cup 

was allowed to cool for 3 to 5 s. another measurement was taken. This process was repeated for a total of 5 doses of 

the contaminated HFE 7100. An illustrated procedure is shoun in Appendix A. 

Process Validation 

Process validation was performed in parallel with the standard HFE 7 100 NVR technique, The parallel 

sampling included 74 work orders sampled over a period oftwo months. When solvent rinses were submitted for 

the NVR determination, four doses of 0.5 mL were reinovcd for sampling by the SQM method. The remainder of 

the solvent was processed by the standard NVR method. 

In order to obtain a statistically significant number of samplings that produce an NVR in thc measurable 

range, it was nccessary to submit solvent samples spiked yith contaminants. This was accomplished by spiking the 

submitted NVR with 5 mL of solvent containing 0.5 mg of a five-component contaminant mix consisting of equal 

amounts of Krytox, Sebacate, DC 190 silicone oil, hydraulic fluid, and Tap Magic. These were processed in the 

same way as the other NVR samples. 

EQUIPMENT AND RE.4GENTS 

reagents were used in this study 

Photoemission Technology. lnc., Model SQM 200 with 0.25-in. aperture 

Stainless steel sample cup, 1.9 cni diameter (0.75 in.) with 0.6 cm (0.25 in.) indentation 

3M Brand HFE 7 100 

Contaminants: Tap Magic, DC 190 silicone oil, Duo Seal pump oil, hydraulic fluid, Aniflo lubricating oil, 

Krytox 240 AC, and di-2-ethylhexyl sebacate calibration fluid. 

XESC'L TS AND DISCUSSION 

Proof-of-Concept Testing 

When HFE 7100 containing Krytox 240 AC at a concentration of 2 mg in 100 tnL is used in this process, 

the plot shown in Figure 4 results. This is a Tukey box plot in which the box represents the range of the 25Ih to 75Ih 

percentiles ofthe data and the 10Ih and 90th percentiles as error bars. The mean is shown as a horizontal line in the 

box. The photocurrent values reported are the direct readout from the instrument and are dependent on the gain 

settings in the instrument. This plot of photocurrent as a function of solvent dosage shows a large initial drop 

followed by sequentially smaller drops in the photocurrent for a leveling off effect. This is attributed to the 

coverage of the clean metal surface by the contaminant, which has a lower photoelectron yield than the clean metal. 
As additional doses of contaminant are added. the photocurrent drops from the high values for clean stainless steel 

and approaches the photocurrent for a thick film of the contaminant. Table I gives the measured photocurrent for 

very thick film ofthe containinants applied to the stainless steel cups. These contaminants have much lower 

photoelectron yields than does clean stainless steel. making it advantageous for the detection of small amounts of 

these contaminants. Also, the photoelectron yields of the contaminants arc all of the same order of magnitude. 

niaking thc technique relatively inscnsitivc to contaminant makeup. Regardless of the contaminant. the photocurrent 

will follow. the same relationship. Figures 5 and 6 show a similar photocurrent versus dose curve for DuoSeal oil 

and DC 190 silicone oil. 

For comparison, results of a set oftests using clean HFE 7100 are shown in Figure 7. This figure shows 

that the photocurrent drops with each sequential addition of HFE 7100. The means of the distributions show a 

nearly linear drop in photocurrent with successive solvent doses. This drop is still readily differentiated froin those 

for HFE 7100 containing a contaminant. The mechanism ofthe photocurrent reduction by the clean solvent is 

unknown and will require further study. 

Using Krytox and Duo Scal oils. operational parameters were optimized to produce the maximum change 

in signal bctwcen thc clean cup and thc initial dose. The volume and shape ofthe stainless stccl cup was adjusted to 

hold 0.5 mL with a 0.25 in. central depression to concentrate the solution at the center of the cup as the solvent 

evaporates. A 0.35 in. aperture was chosen to match the central deprcssion in the stainless steel cup whcrc the 

contaminant should be concentrated upon solvent evaporation. The working distance is the closest distance that can 

be achieved given the variation in the height from one cup to the next. A hot plate temperature of 40 "C gave 

acceptahlc drying times. minimal Contaminant loss. and is a safe temperature in case of accidental contact by the 

operator. 

*0° 

loo 

0' 

i 

I 

I I I 1 I 1 

0 1 2 3 4 5 6 

Dose Number 

Figure 4 

Photocurrent as a Function of Dose with HFE 7 100 Containing 2 tng Krytox" in 100 mL 
Table 1 

Measured Photocurrent for Thick Films 

Material Photocurrent 

WSTF Cleaned Stainless Steel 304 > 500 

Duo Seal ' 80 

Ainflo" Oil I 0s 

DC 190' Silicone 011 40 

Hydraulic Fluid 100 

Houghto DrawK 40 

Tap Magic ' 100 

Krytox ' 240 AC 60 

NOTE: lnstruinent gain set at I, probe gain set at 7 

Process Validation 

The process validation results are shown in the box plot in Figure 8. It shows the same behavior as in the 

Figure 7 results from the proof-of-concept testing. Much of the range (spread, distribution) in the data is due to thc 

variability in photocurrent in the set of clean coupons. For each cup tcsted. a ratio was obtained by dividing the 

photocurrent froiii a clean cup by the photocurrent from the same cup after each dose. This resulted in a tighter 

distribution of data for the first three doses. The resulting plot is shown in Figure 9. All 74 samples passed the 

standard NVR cleanliness verification with a residue of less than 0.2 ing. 

The results as photocurrent and photocurrent ratio for spiked samples are shown in Figures 10 and 1 1. 

Comparing Figures 9 and I I. it is possible to distinguish between clean and spiked solvent u,ith no overlap in the 

distributions by the second dose of solvent. Based on the need for no more than three doses of solvent to detect 

contaminants. the improved cleanliness verification process is shown in Figure 12. 

800 

700 

600 

c. 500 E 

5 

CI 400 0 

0 

f 

i 

300 

200 

100 

0 

0 1 2 3 4 5 6 

Dose Number 

Figure 5 

Photocurrent as a Function of Dose with HFE 7 IO0 Containing 2 mg Duo Seal'K in IO0 mL 
800 

0 

- 500 - C 

E 

400 - 3 

3 

22 0 c 

a 300 - 

200 

100 

0 

0 1 2 3 4 5 

Dose Number 

Figure 6 

Photocurrent as a Function of Dose for HFE 7 IO0 

Containing 1 mg DC 190" Silicone Oil in 100 mL 

aoo 

700 

500 - 

E L 

3 400 - 0 

0 

c 

300 - 

2oo 1 

B 0 

0 

B e 

loo 0 1 

0 1 2 3 4 5 6 

Dose Number 

6 

Figure 7 

Photocurrent as a Function of Dose with Clean HFE 7100 
800 

700 

600 

E 500 

2 400 

0 

0 

E 300 

E? L 

c 

200 

100 

0 

L 

0 

0 

0 0 

0 

6 Y 0 

0 

T 

0 

P 

0 1 2 3 4 5 6 

Dose 

Figure 8 

Photocurrent as a Function of Dose for Parallel Sampled Work Orders 

14 

12 

10 

4 

2 

0 

0 0 

0 

0 1 2 3 4 5 6 

Solvent Dose 

Figure 9 

Photocurrcnt Ratio as a Function of Dose Number for Parallel Sampled Work Orders 
12 - 

10 - 

h - 

1 8- 

0 

- 0 

Y 

.- 

6- c 

2 

4- 

2- 

0 

0 

0 

0 

*AP E 

of I 1 I I 1 

0 1 2 3 4 5 6 

Dose Number 

Figure 10 

Photocurrent as a Function of Dose Number for HFE 7100 Samples Spiked with 

0.5 mg Five-Component Mix 

800 

700 

600 

500 

E $ 400 

300 

Y 

0 

c 

200 

100 

0 

Figure I1 

Photocurrent Ratio as a Function of Dose Number for HFE 7100 Samples Spiked 

with 0.5 mg Five-Component Mix 
Obtain Measurement 

[:caporate to I>rynes\ 

C ool dnd Obtain Cool and Obtain Cool and Obtdin 

M edwrenient Measurement M eawemen I 

Figure 12 

SQM Cleanliness Verification Process 

In operation. the SQM is connected to a computer for data logging and computation. First a baseline 

photocurrent measurement is taken from a clcan cup. The signal is averaged for 10 s. From the 100 mL rinsc 

acquired for the NVR, a 0.5 niL aliquot is placed in the cup. The cup is then heated to 40 "C until the solvent 

evaporates, approximately I min. After the cup is allowed to cool. another incasurcriient is taken. Using the same 

cup, a second sample of the HFE 7 100 rinse is then processed in the same way. An optional third evaporation and 

measurement of the solvent can be taken if further confirmation is required. 

Setting the Pass-Fail Threshold 

A set of response curves for three doses of clean HFE 7 100 and HFE 7 I00 contaniinatcd with 0.25, 0.5. 

I .O. 1.5. and 2.0 mg of thc five-component mix was generated from the average of 10 replicate samplings at each 

concentration. These response curves are shown in Figure 13 where the average photocurrent and linear regressions 

are plotted for the first three doses. Figure 14 is a plot of the photocurrent ratio as a function of dose number from 

the same data set. These curves can be used to set a pass-fail threshold for a particular cleanlincss requirement. The 

data may also be used to construct a calibration curve for each dose from which the contaminant amount can be 

determined for a given photocurrent or photocurrcnt ratio. 

SUMMARY 

A method for cleanliness verification has been developed using the SQM 200. 

A numbcr of contaminant responses were measured and the reponses were very ncarly equal. 

By sampling the rinse solvent two or more times, the confidence in the measurement is increased. 

Because of the small aniount of solvent used. retests are possible. 

CONCLUSIONS 

The SQM and NVR methods are equivalent in measuring surface cleanliness 

The SQM offers significant savings in the time required to process the NVR. 

In handling and evaporating less solvent, significant solvent savings can be realized. 
REFERENCES 

NASA. C'oiitrinriritrtioii C'oritrd Rei~irir.en~rrif.r MLiiiirol. J HB 5322, Revision C. NASA Johnson Space Center, 

Houston. TX (Fcbruary 1994 or latest revision). 

500 - 

c 

400 - 

5 

3 

- 0 

2 300 - 

E 

< 

p. 

e, 

31) 

?2 200 - 

100 - 

600 

0 Clean HFE 7100 

v 

0 

+ 

A 

0 25 mg per 100 mL 

0 5 mg per 100 mL 

1 0 mg per 100 mL 

1 5mg per 100 mL 

2 0 mg per 100 mL 

- Linear Regression 

OJ 

1 2 3 

Dosc Numbcr 

Figure 13 

Akerage Photocurrent versus Dose Numbcr for Clean and Spiked HFE 7100 

10 , 

0 Clean HFE 7100 

Q 

+ 

A 

0 25 mg per 100 mL 

0 5 mg per 100 mL 

1 0 mg per 100 mL 

1 5 mg per 100 mL 

2 0 mg per 100 mL 

- Linear Regression 

0' 1 1 

1 2 3 

Dose Number 

Figure 14 

Photocurrent Ratio versus Dose Number for Clean and Spiked HFE 7100 
Criteria for NVR Solvent Replacement 

Dianne J. Coleman, Kenneth T. Luey and Joseph C. Uht 

Space Materials Laboratory 

and 

Graham S. Arnold 

OfEce of Research and Technology Applications 

The Aerospace Corporation 

El Segundo, CA 90009 

Abstract 

Molecular film contamination is detected and monitored using a gravimetric laboratory process described 

in ASTM standard methods. These processes currently specify the use of methylene chloride, an organic solvent 

targeted for reduction by the Environmental Protection Agency. In this paper, we describe a request for a change in 

the solvent specified. We briefly review the criteria for the suggested replacement, ethyl acetate. The solubility 

criteria assembled for the replacement of methylene chloride are then used to evaluate the replacement of methlyene 

chloride-based paint removers. 

1.0 Introduction 

The most typical and important contaminants affecting space hardware are microscopic particles and 

molecular films. Contamination by particles is removed using precision vacuuming or wiping with benign solvents. 

The cleanliness of critical surfaces can be verified by the microscopic inspection of tape lifts or witness plates. The 

quantitative detection of molecular films, however, involves a gravimetric laboratory process. For the measurement 

and diagnosis of spacecraft processing facilities, the procedure uses the exposure of witness plates and subsequent 

rinsing with solvents[ I]. To measure nonvolatile residue (NVR) directly on surfaces, the process involves wiping 

with solvent -soaked cloths[ 31. 

In ASTM E1335-95. a stainless steel witness plate is exposed to a facility environment for an extended 

time. In a laboratory, the plate is then rinsed with solvent. The solvent is filtered and deposited in a beaker of 

known tare. The solvent is then evaporated away, leaving the non-volatile residue or NVR. Initially, the solvent 

used for rinsing the NVR from the witness plates or from the wiping clothes was a mixture of ethyl alcohol and 1,1,1 

trichloroethane. 1,1,1 trichloroethane has since been categorized a Class I Ozone Depleting Cheniical (ODC). As 

currently written, ASTM E123595 specifies the use of methylene chloride (dichloromethane) as the rinsing solvent. 

Methylene chloride is targeted for reduction by the US Air Force under Section 313 of the federal Emergency 

Planning and Community Right-To-Know Act (EPCRA). EPCRA 3 13 requires facilities to report releases of 650 

toxic chemicals to the air, water and land, as well as the quantities recycled, treated, burned or otherwise disposed 

of. ASTM E1235-95 itself notes: 

Methylerw chloride is toxic and is being phased out for many applications. Replacement solvents are iitider 

study arid will be substituted when available. Use iiietlivlene chloride only in an exhaitsting work station. 

This paper is composed of three parts. 

I. We document and describe an official request for a change of solvents in the ASTM El 235-95 standard 

process in Section 2.0. 

11. We review the rationale for the choice of the replacement solvent, ethyl acetate, in Section 3.0. 

111. We discuss the extension of the methylene chloride replacement criteria to the operation of paint removal 

in Section 4.0. 
2.0 ASTM E1235-95 Request for Change 

ASTM E1235-95 was due for reconsideration in the year 2000 by the Subcommittee E21.05 on 

Contamination. Subcommittee E21.05 is part of the ASTM Committee E-21 on Space Simulation and Application 

of Space Technology. The process for consideration is outlined below: 

1. ASTM subcommittee recehves request, proposal and supporting data. 

This request was made in November 1999. The supporting data and reports are summarized in the 

following section. 

Proposal and data are discussed by the cornmittec members. 

For ASTM E 1235-95, the committee members were in general agreement that the standard solvent was in 

need of change. Basic agreement was obtained in this meeting of the 21.05 subcommittee. 

Deiielop n proposal,for a rewritten standard. 

The proposed rewriting of the standard was developed and submitted to the E21.05 subcommittee chairman 

2. 

3. 

on 28 April 2OOO. The proposed rewrite is presented below. 

TABLE 1. Proposed rewrite of ASTM E1235-95 with respect to the usage of methylene chloride and its replacement 

by ethyl ace1 e. 

LINE 

NUMBER 

4.’ 

7.6 

NOTE 5 

Footnote 17 

10.2 

10.4.1 

11.2.1 

CURRENT TEXT READS 

The plate is rinsed with a high purity 

methylene chloride solvent. 

NVR Solvent consisting of HPLC (highpunty liquid chrornato&aphy) grade 

methylene chloride (dichloromethane). 

The solvent shall be certified to contain <I 

ppm (<I me) NVR using the procedure 

in Section 10. 

Methylene chloride is toxic’ and is being 

phased out for many applications. 

Replacement solvents are under study and 

will be substituted when available. Use 

methylene chloride only in the exhausting 

work station (6.3). 

Material Safety Data Sheet No. 310, 

Genium Publishing Corp., 145 Catalyn St., 

Schenectady, N.Y. 12303. 

The NVR of each bottle shall be 

determined upon opening in accordance 

with 103. 

Methylene chloride can be toxic. Handle 

Nith caution and observe appropriate 

orecautions. 

Methylene chloride can be toxic. Handle 

with caution and observe appropriate 

precautions. 

PROPOSED REVISION 

The plate is rinsed with high punty ethyl 

acetate solvent. 

NVR Solvent consisting of HPLC (high-purity 

liquid chromatography) grade ethyl acetate. The 

solvent shall be certified to contain <I ppm (<I 

mg/L) NVR using the procedure in Section 10. 

Note: Burdick & Jackson cat. No. 100, B&J 

Brand Ethyl Acetate has been found to be 

satisfactory 

Ethyl acetate” is an organic solvent, and as 

such, presents some degree of physical and 

health hazard. Use of ethyl acetate should be 

according to the recommendations provided in 

the Material Safety Data Sheet 

Material Safety Data Sheet No. 437, Genium 

Publishing Corp., 145 Catalyn St., Schenectady, 

N.Y. 12303. 

Typo: The NVR of each bottle shall be 

determined upon opening in accordance with 

10.7. 

Handle ethyl acetate with caution and observe 

appropriate precautions . 

Handle ethyl acetate with caution and observe 

appropriate precautions. 

Note the typo in the current standard in Section 10.2, erroneously refemng to Section 10.3. 
4. This proposal will be reformatted ns rieeded by the E21.05 subcommittee chairman. 

The proposal is currently at this point in the process. 

5. A ,firin1 vote $till cmichrde the process. 

We note here as well that ASTM E1560M-95 “Standard Test Method for Gravimetric Deternunation of 

Nonvolatile Residue from Cleanroom Wipers” specifies an NVR solvent consisting of three parts 1, I, 1 

trichloroethane and one part ethanol, by volume. As noted earlier, 1,1,1 trichloroethane has been denoted a Class 1 

OK. The NVR solvent designated in E1560 will also have to be modified at a future time. 

3.0 Replacement Rationale 

In this section we briefly review the rationale for the replacement of methylene chloride. 

In work performed by Arnold and Uht[3], potential solvent replacements were evaluated using a literature 

review of solvent properties together with a laboratory testing approach. The goal of the effort was not to find the 

best solvent for removing a particular NVR, but rather to maintain a connection with heritage results. A suitable 

“drop in” replacement therefore would have properties closely matched to methylene chloride and the NVR mixture 

of 1,1,1 trichloroethane and ethanol. In addition, certain other properties would also play a key role in the 

evaluation. The vapor pressure would play a key role since the solvent needs to remain on the surface long enough 

to perform an effective wiping test. However, one would not want a solvent with too low a vapor pressure such that 

the evaporation step in the NVR tests would take an unreasonably long time. The results of most NVR tests are 

desired in 24 - 48 hours. The replacement solvent would need to be readily available from more than one source. 

Ideally, it would be available routinely having a low level of impurities. It would have suitable safety, toxicity and 

flammability properties and, of course, would be environmentally acceptable. All of these properties were evaluated 

to develop a “score” for a large number of replacement candidates. 

In this paper, we focus on the solvent properties. Solvent properties are described successfully beginning 

with the cohesive energy density, c, given by 

c = -UN 

where U is the molar cohesive energy and V is the molar volume and where the units of c are the same as pressure. 

The Hildebrand parameter is given by 

6 has units of (MPa)”’. According to Barton [4], two materials with similar values of 6 gain energy on mutual 

dispersion to permit mixing. On the other hand, a material with a high value of 6 requires higher energy for 

dispersal than can be obtained from a material with smaller 6 and immiscibility results. These statements are similar 

to the rule-of-thumb often stated that “like dissolves like.” 

Solvent properties are now successfully described using multi-component parameters such as the threecomponent Hansen parameters shown in Equation 3. 

where 6, describes dispersion forces, S, describes the polar forces and &, corresponds to hydrogen bonding. The 

total Hansen parameter, S, is equivalent to the Hildebrand parameter. 

The replacement of methylene chloride or 1,1,1 trichloroethane begins by identifymg those solvents with a similar 

6,. The results of that study are shown in Figure 1. Note in Figure 1 that several solvents have very large 6, values, 

among them the solvents Freon 113 and methanol. However, the key is to identify those solvents that have the 

greatest similarity to methylene chloride and 1,l. 1 trichloroethane, whose values of 6, are between 18.5 and 20.5. 
The suitable candidates are methyl isobutyl ketone, n-butyl acetate, methyl acetate, ethyl acetate, and 

tetrahydrofuran. 

k v R sot.enl blend 

-T-- - ~- --- 

11 1 trichloroethane 

methylene chloride 

2 propanol 

2 pyrrolidone 

N methyl 2 pyrrolidone 

aceta Ide h y d e 

acetone 

acetonitrile 

ace top h en on e 

cyc Io he I: an e 

diethyl ether 

d im e th y Is u If0 x id e 

ethanol 

ethyl acetate 

ethyl lactate 

ethylene glycol 

Freon 113 

heptane 

methanol 

methylacetate 

rnethylethyl ketone 

methyl isobutyl ketone 

n butyl acetate 

hexane 

tetra hydro lu ra n 

to Iu e ne 

0 s io 15 20 25 30 35 

Total Hansen Parameter, 6, 

Figure 1. Solvent rankings based on total Hansen solubility parameter, 8,. The desired replacement solvent for 

methylene chloride (dichloromethane) lies between 18 anid 30.5 as indicated by heavy black lines. 

For a three-component "vector" quantity such as the total Hansen parameter, the vector difference between, say, 

methylene chloride and any other solvent, designated by i. can be defined. 

where the vector difference d is made up of the individual differences between the dispersive, polar and hydrogen 

bonding characteristics of methylene chloride and any other solvent. Though several solvents might have a total 

Hansen parameter near that of methylene chloride, ethyl acetate has the smallest vector difference. That is, ethyl 

acetate has the smallest difference between each of the forces: dispersive, polar and hydrogen bonding. 

As stated previously, the vapor pressure plays a practical role in the selection of a replacement solvent. A 

solvent with a high vapor pressure reduces the residence time on the tested surface in a wiping test. A solvent with a 

low vapor pressure would extend the duration of the evaporation step in either of the NVR tests. Therefore, one 

seeks a solvent of moderate vapor pressure. Arnold and Uht indicated that diethyl ether would be as high a vapor 

pressure solvent as one would want to handle and ranks one step above methylene chloride. Isopropyl alcohol (2- 

propanol) was suggested as the lowest vapor pressure solvent. Ethyl acetate is near the low end of the vapor 

pressure scale, but higher than that of '-propanol. 
Three figures of merit were examined concerning the flammability and toxicity hazards: the threshold limit 

value (TLV); the inhalation hazard ratio (IHR); and the "Flash Point." The TLV represents the hazardous exposure 

level to the material given in ppm. The IHR is the ratio of the saturated vapor concentration at 25°C to the TLV. 

So-called open cup (OC) and closed cup (CC) flash point measurements give the temperature at which a solvent can 

be ignited by a hot wire. OC measurements address the possibility of ignition in an open environment as would 

occur in a spill, while CC tests address the ignition in closed container. Since all potential replacements were both 

volatile and flammable, the flash point data were not given significant weight in the scoring. 

Table 2. Flammability and toxicity assessment for various NVR solvent replacement candidates from Reference 3. 

Solvent Flash Point TLV, ppm Inhalation Ratio Comments 

1,1,1 None 350 45 1 Class 1 ODC 

trichloroethane 

2-propanol 12 400 140 

2-pyrrolidone 110 No TLV Data 

Acetone -19 750 386 

Aetonitrile 6 40 2888 

Cyclohexane -18 300 396 

Diethyl ether -45 400 1806 

Dimeth ysulfoxide 88 Skin Penetrant, no TLV 

Ethanol 12 1000 74 

Ethyl acetate -4 400 288 

Ethyl lactate 49 No TLV data 

Freon 1 13 48 1000 434 Class 1 ODC 

Heptane -4 400 141 

Hexane -22 50 3816 

Methanol I1 796 

Methyl acetate -16 200 1375 

Methyl ethyl -6 200 630 EPA 17* 

ketone 

Methylene None 50 11184 Carcinogen, EPA 17" 

chloride 

n-methyl-2- 86 No TLV data 

pyrrolidone 

Tetrahydrofuran -14 200 I086 Explosive hazard in distillation 

Toluene 4 50 703 EPA 17* 

Pollutant Strategic Implementation Plan. 

Ethylene glycol 111 50 3 

n-butyl acetate 22 150 112 

*"EPA 17" refers to the voluntary reduced emissions of I7 chemicals as part of the EPA's Hazardous Air 

Most of the candidate solvents are seen to have a higher TLV and lower IHR than methylene chloride, 

warranting the toxic warnings concerning methylene chloride in the ASTM E1235-95. The exceptions are 

acetonitrile, with a TLV of 40 ppm versus 50 ppm for methylene chloride. 

A series of experimental results was conducted to evaluate the effectiveness of ethyl acetate compared to 

methylene chloride for use as an NVR solvent. The first test involved stainless steel witness plates exposed for one 

month in a machine shop environment. They were then bagged together for about three months. The results of 

subsequent ASTM E1235 testing are shown in Table 3. The agreement is very good. 

Table 3. ASTM E1235 test results using methylene chloride and ethyl acetate solvents. 

Methylene Chloride Ethyl Acetate 

Sample Mass (g) 0.00093 0.00147 

Blank (g) 0.00029 0.00072 

NVR Mass (g) 0.00064 0.00075 
A series of tests were performed in which known amounts of contaminants were deposited on stainless 

steel witness plates having one square foot area. The witness plates were then rinsed with solvents to recover the 

deposited contaminant. The percent contaminant recovered, k, is given by: 

R, = (m, -mh)/mr x 100 (5) 

Where m, is the contaminant mass recovered, mh is mass of the solvent blank and m, is the known mass of the 

deposited contaminant. The results for one of the contaminants, tetraphenyl dimethyl disiloxane, a typical 

represntative of silicones, are shown in Figure 2. Ethyl acetate and methylene chloride are equally effective in 

removing this contaminant. Methyl acetate is not recommended due to its high vapor pressure and toxicity. 

P 

f 

8 

K 

110 

100 

90 

ao 

70 

60 

50 

40 

30 

20 

10 

0 

ethyl acetate methyl acetate methylene chloride 

Figure 7. Percent recovery of deposited tetraphenyl dimethyl disiloxane from witness plates using three different 

solvents. 

4.0 Application to Paint Removal 

Methylene chloride is used extensively as a paint remover and the search for replacements is vigorous. 

Paint removal is performed frequently in the aircraft and aerospace industries and a signficant amount of methylene 

chloride is used for this purpose. As part of the effort to remove hazardous air polluting (HAP) chemicals from DoD 

processes, an examination was made of solubility parameters as a means of identifying replacements for methylene 

chloride-based paint removers or strippers. 

Paint removal and NVR solvent replacements have similarities and differences. A suitable NVR solvent 

replacement did not consider specific chemical interactions between solvent and NVR. It was not desired that the 

solvent replacement remove more NVR than the 1,1,1-trichloroethane/ethanol blend. Rather, the intent was to find a 

replacement most like the blend. Solubility parameters were therefore an ideal focus, since only the vector 

differences of the solvents were compared. 

The paint removal process can be more complicated than an NVR test. The choice of a paint remover 

requires the optimization of many steps. It is generally understood that paint stripper solutions must remain on 

painted surfaces for a long time. In most aircraft paint removal applications the soak time can be 6 - 12 hours. Paint 

removal solutions containing methylene chloride use a gel or other type of “sealant” to enhance the methlyene 

chloride residence time on the surface, since methylene chloride has a relatively high vapor pressure. For many 
methylene chloride-based paint removers, more than one application is recommended. The methylene chloride must 

diffuse through multiple layers of paint before reaching the primer and then will cause separation and swelling of the 

paint from the primer. The solvent must then affect the bond between metal and primer. The solvent must also not 

damage the underlying metal. References to the actual dissolving of paint by methlyene chloride are difficult to find 

in the aircraft paint industry but are sometimes referred to in the art restoration area. 

Median I 15.1 

Table 4 presents a full listing of the dispersive, polar, hydrogen bonding and total Hansen solubility 

parameters for the solvents considered as the replacement in the NVR test[4]. The far right column also gives the 

molecular dipole moment in Debye measured in the gas phase[5]. Dipole moments measured in the liquid phase are 

also shown and are indicated in parentheses. Dipole moments measured in the liquid phase are described in [5] as 

less reliable. 

10.4 1 9.6 30 I I .7 

Table 4 shows that methylene chloride does not lie in an extreme range of the parameters. Its values for the 

three Hansen parameters are very near both the average and median values for the solvents listed. Similarly, its 

dipole moment is less than the average and median values. It is therefore not strikingly obvious why methylene 

chloride should be in wide use as a paint remover based on solubility. 

By once again using the rule-of-thumb that "like dissolves like," we performed an analysis of solubility 

parameters and their vector differences for a number of polymeric coatings and solvents. A collection of solubility 

data for several polymeric coatings was obtained from the literature[6] and is shown in Table 5. This particular 

collection of polymer coatings was assembled by Burke and includes a radius of interaction, R. R is a measure of 

how similar a solvent must be in order to dissolve the polymer and is determined empirically. 
Table 5. Hansen solubility param Y 

PolwnerK’oating 

Burke. 

Like Eq. (4), Burke defines a vector solubility “distance” between solvent and polymer, D5.p.given by: 

Where a,, and a,, are the three Hansen parameters (i=d, dispersive; p, polar; and h, hydrogen) for the solvent and 

polymer, respectively. D5.pdiffers from Eq. (4) by the leading factor of 4 for the dispersive term. It is included to 

create a spherical “solubility volume.” The results of the comparison are shown in Table 6. The designation “Yes” 

indicates that the vector difference DS-P is less than R, and the solvent and polymer are therefore closely enough 

alike that the solvent will dissolve the polymer. These polymer coatings are not necessarily paints, although some 

paints might contain certain percentages of these polymers in their formulations. 

Table 6. Solubility of polymer coatings compiled by Burke[4] in solvents compiled by Arnold and Uht[3]. 

Solvent Methhylene Tetra- Cyclo- 2-pyrroPolvmer/Coating 

Cellulose acetate 

Chlorinated pol jpropylene 

Epoxy 

Isoprene elastomer 

Cellulose nitrate 

Polyamide, thermoplastic 

Poly( isobutylene) 

Poly( ethylmethacrylat e) 

Poly( methyl methacrylate) 

Polystyrene 

Poly(viny1 acetate) 

Poly (vinyl butyral) 

Poly (vinyl chloride) 

Saturated polyester 

Number Dissolved 
Table 6. Continued 

Solvent Ethyl Diethyl N-methyl- Ethylene 

Polvmer/Coating 

Cellulose acetate 

Chlorinated polypropylene 

EPOXY 

Isoprene elastomer 

Cellulose nitrate 

Polyamide, thermoplastic 

Poly(isobuty1ene) 

Poly( ethylmethacrylate) 

Poly(methy1 methacrylate) 

Polystyrene 

Poly(viny1 acetate) 

Poly (vinyl butyral) 

Poly (vinyl chloride) 

Saturated polyester 

Number Dissolved 

Within this group of coatings, we see that methylene chloride does appear to be only a moderate dissolver 

of polymer coatings. Other solvents that dissolve more than five polymers in the group, including toluene, MEK, Nmethyl-2-pyrrolidone, 2-pyrrolidone and acetone, are frequently mentioned as cosolvents with methylene chloride in 

commercial paint removers. On the other hand, tetrahydrofuran and methanol are also frequently mentioned as 

cosolvents with methylene chloride but are not indicated by this analysis. The success of ethyl acetate as a dissolver 

of a wide range of polymers is both surprising and disturbing, as ethyl acetate is now being used to measure NVR on 

some painted surfaces. So far, there have been no reports of painted surfaces being damaged by the NVR test. 

Laboratory testing of this and other solvents on painted surfaces would be valuable and is planned. 

This study addresses the solubility aspects of paint removal. However, it is generally believed that 

solubility plays a minor role in the large-scale paint removal tkom aircraft surfaces. It is thought that the diffusion of 

molecules through many paint coats and the subsequent interaction with the substrate-polymer bond is more 

significant. The chemical interaction with this bond is not well quantified and is, so far, a subject that is studied 

experimentally. More specialized, lower-volume paint removal applications, such as art restoration, are more 

concerned with the ability of solvents to actually dissolve polymers. There is also no rate information contained in 

the above analysis. Thus, it could prove that ethyl acetate did indeed dissolve painted surfaces during an NVR test, 

but at such a slow rate that it would not have been noticed, nor would appreciable amounts of dissolved polymer be 

found in the non-volatile residue. 

5.0 Summary and Conclusions 

As part of DoD campaigns to reduce the use of hazardous polluting materials, an effort has been made to 

identify and reduce the use of methylene chloride, among other materials. In previous work, a literature study of 

solubility parameters was used to determine a substitute for methylene chloride used as a solvent in ASTM and DoD 

tests for nonvolatile residue. Ethyl acetate was identified as the best replacement based primarily on the solubility 

parameter analysis. The results of toxicity and flammability analyses and a modest laboratory test program also 

contributed to this choice of a replacement solvent. 

This year, a formal request was made to the ASTM E2 I .05 subcommittee to change the specified solvent 

from methylene chloride to ethyl acetate in ASTM E1235-95 “Standard Test Method for Gravimetric Determination 

of Non-Volatile Residue in Environmentally Controlled Areas for Spacecraft.” A proposed rewriting of ASTM 

El 235-95 has been submitted and is now being formatted in preparation for a final vote. 

The solvent solubility data were used to evaluate the replacement of methylene chloride in the paint 

removal application. It was found that a much more detailed understanding of the paint removal mechanism is 

needed than for the NVR test process, and on the basis of solubility, methylene chloride itself is not identified as a 

good solvent of polymers. Rather, it is thought that methylene chloride has small molar volume and therefore 

diffuses well through many coats of paint. Several known additives to methylene chloride in commercial paint 
removers are identified by their solubility parameters. These include toluene, MEK, tetrahydrofuran, N-methyl-2- 

pyrrolidone, 2-pyrrolidone and acetone. Methanol, however, which is probably the most common cosolvent with 

methylene chloride in paint removers, is not identified on the basis of solubility parameters. The results of this 

analysis show that, in addition to a more mechanistic understanding of paint removal, a supplementary laboratory 

testing program is essential to finding replacements. 

Acknowledgments 

The authors gratefully acknowledge valuable technical discussions with Dr. Gidget K. Ternet. 

Funding for this work was provided by Air Force Materiel Command (AFMC) through a Pollution Prevention 

project initiative. The work was done under Air Force contract No. FO4701-93-C-0094. The authors would like to 

acknowledge Mr. Dan Pilson, Project Manager, SMC/AXFV and Dr. Valerie Lang, Office of the Corporate 

Engineer, The Aerospace Corporation, for their support and administration of this effort. 

References 

1. Standard Test Method for Gravimetric Detennination of Non-Volatile Residue in Environmentally Coiltrolled 

Areas for- Spacecrqfi, ASTM E 1235-95, Vol. 15.03 Space Simulation; Aerospace and Aircraft: High Modulus 

Fibers and Composites 

2. E. N. Borson, E. J. Watts and G. A. To, “Standard Method for Measurement of Nonvolatile Residue on 

Surfaces”, SD-TR-89-63 or TR-0089 (4530-02)-1, The Aerospace Corporation, El Segundo, CA, 10 August 

1989. The evaluation of NVR from the cloths is discussed in, Staridard Test Methodfor Gravimetric 

Dctcmiiiiation of Notivolatile Rcsidue.from Cleanrooin Wipers, ASTM E 1560M. 

3. G. S. Arnold and J. C. Uht, “Nonvolatile Residue Solvent Replacement,“ TR-95(5448)-1, The Aerospace 

Corporation, 01 March 1995 

4. A. F. M. Barton, CRC Handbook of Solubility Parameters and Other Cohesion Parameters, CRC Press, Boca 

Raton, FL, 1983. 

5. CRC Handbook of Chemistry and Physics, SOLh Edition, R. C. Weast, ed, CRC Press, Boca Raton, FL, 1999. 

6. J. Burke, “Solubility Parameters: Theory and Application,” AIC Book and Paper Group, (3), 1984, pp. 13-56. 
Critical Surface Cleaning and Verification Alternatives 

MATERIAL 

HCFC 2256 

Freon 11 3 

HCFC 225 

BY 

Donald M. Melton 

Lockbeed Martin. Michoud Operations 

13800 Old Gentilly Rd 

New Orleans. La. 701 29 

503-257- 1782 

LOT TESTS RESULTS 

5970421 1 0120 PASSED 

NJA 0120 PASSED 

3114 0120 PASSED 

Abstract 

As a result of federal and state requirements. historical critical cleaning and verification solvents 

such as Freon 113. Freon TMC, and Trichloroethylene (TCE) are either highly regulated or no longer 

available. Interim replacements such as HCFC 225 have been qualified. however toxicity and fkture phaseout regulations necessitate long term solutions. 

The scope of this project was to qualify a safe and environmentally compliant LOX surface 

verification alternative to Freon 113. TCE and HCFC 225. The main effort was focused on initiating the 

evaluation and qualification of HCFC 2256 as an alternate LOX verification solvent. The project was 

scoped in FY 99/00 to perform LOX compatibility. cleaning efficiency and qualification on flight 

hardware. 

Introduction 

HCFC 2256. is a cleaning solvent that is an environmentally compatible alternative for 

HCFC 225 in the areas of metal cleaning. vapor degreasing. and flushing. The major difference between 

HCFC 225 and HCFC 2256 is that HCFC 2256 is a single component (3.3-Dichloropentafluoropropane). 

while HCFC 225 is a two component system (3.3-Dichloropentafluoropropane and 1,3- 

Dichloropentafluoropropane). By removing the 1.3 isomer HCFC 2256 is less toxic than the HCFC 225 

product. The respective Threshold Limit Values (TLV) are 250 ppm versus 25 ppm. 

Body 

A) LOX Compatibility Evaluation of HCFC 2256 

The technical approach was to evaluate HCFC 2256 for LOX mechanical impact sensitivity testing 

with liquid oxygen by the procedure outlined in NHB 8060/NASA STD-600 I Test 13 Part # 1. 

Duplicate lots of Freon 113, HCFC 2256, and HCFC 225 were tested per NHl38060.1B/NASA-STD-6001, 

test 13A, at Marshall Space Flight Center (MSFC) for LOX compatibility. All solvents submitted passed 

LOX compatibility tests, as shown in Table 1. 

Table 1 LOX Compatibility Test Results 
B) HCFC 2256 Cleaning Efficiency 

The technical approach to evaluate HCFC 22% cleaning efficiency was by applying E.T. 

contaminants to 2219 .4l test panels. Gravimetric analysis was performed in order to determine the percent 

removal cleaning efficiency for each of the respective contaminants. 

The evaluation of the HCFC 225G consisted of preparing AI-2219 test panels for three (3) of the 

most common E.T. contaminants (5-414 Tape Residue, Safe Tap and CRC 2-26). The respective test panels 

were weighed before and after the contamination process with each of the respective E. T. contaminants. 

HCFC 225G was flushed onto the contaminated surface with a controlled stream of 500 nL of solvent from 

a pressurized vessel that emulated the current process. The test panels were flushed from top to bottom to 

insure contact with the entire contaminated surface. Afier flushing. each test panel was placed in a 

desiccator for 24 hours and then weighed to a constant weight. A percent (YO) cleaning efficiency was 

calculated for each solvent and its respective test panels as shown in Table 2 through 4. Based upon the 

overall percent removal cleaning efficiency of the three major E.T. contaminants. HCFC 225G cleaning 

solvent was recommended for additional qualification testing on flight hardware. 

Table 2 

HCFC 2256 Cleaning Efficiency of Safe-Tap Drilling Lubricant 

Average 106.09 
PANEL #: 

C1 

INITIAL WT. CONT. Panel wt. Cont. CLEANED AMT. REMOVEL' yo CL. EFF 

WT. 

138.974 138.997 0.023 138.975 0.022 95.65 

c2 

c3 

c4 

c5 

AVERAGE 101.16 

138.753 138.775 0.022 138.753 0.022 IOO.00 

138.818 138.830 0.012 138.817 0.013 108.33 

139.1 10 139.140 0.030 139.11 0.030 100.00 

139.520 139.548 0.028 139.52 0.028 100.00 

Table 4 

HCFC 225G Cleaning Efficiency of 5-414 Tape Residue 

C6 

c7 

C8 

C9 

c10 

HCFC 225G performed better than Freon 113 (PCA) as a cleaning solvent replacement for HCFC 

225. HCFC 225 is the current implemented replacement for Freon 113 (PCA). Percent (%) cleaning 

efficiency comparative results are listed in Table 5. Therefore a qualification plan was established to 

compare Freon 113 (PCA) and HCFC 225 to HCFC 2256 as baselines for all replacement solvent. 

138.587 138.602 0.0 15 138.586 0.0 16 106.67 

139.653 139.672 0.019 139.653 0.019 100.00 

139.285 139.304 0.019 139.286 0.01 8 94.74 

138.406 138.423 0.01 7 138.406 0.017 100.00 

139.773 139.805 0.03 2 139.771 0.034 106.25 
Table 5 

Percent (%) Cleaning Efficiency Comparative Results 

Contaminant Solvent Average YO Efficiency 

CRC 2-26 Oil Freon I13 98.4 

HCFC 225 91.8 

HCFC 2256 101.0 

Safe Tap Freon 1 13 64.7 

HCFC 225 96.6 

HCFC 22% 106.0 

5-414 Freon 113 61.3 

HCFC 225 3 1.5 

HCFC 2256 75.2 

C) Perform Qualification of HCFC 2256 as an Alternative Cleaning Solvent for HCFC 225 

The technical approach to support qualification was to evaluate replacement solvent cleaning ability 

on the following flight and non-flight items: 

20 A LOX feedline (80971028425-010) 

LH Clean Kit (80924061028M900) 

Tube Assembly (80923021036-050) 

Mask Tool (non-flight), T3 I K2026 

The plan consisted of cleaning flight hardware per Marshall Space Flight Center specification 

MSFC-SPEC-164B or C and process instruction (PI) 5008. Four (4) representatives of flight hardware were 

selected to evaluate using HCFC 225G per NASA's operational directive (99/OD/057 I). 

The flight hardware cleaning evaluation consisted of flushing metallic flight hardware with HCFC 

2256 by the clean-room operators. upon completion an NVR sample was taken and analyzed. After each 

cleaning and NVR verification with HCFC 2256, an NVR verification sample (500 mL) of the hardware 

was immediately taken using HCFC 225 and analyzed to insure that the removal of the organic production 

contamination had been accomplished with HCFC 2256. Two (2) tube assemblies were evaluated in FY 00. 

The results are shown in Table 6. 

Table 6 

Flight Hardware Qualification Results 

Flight Hardware Solvent MG/FT2 

Tube Assembly HCFC 2256 1.5 

HCFC 225 0.7 

Tube Assembly HCFC 2256 1.6 

HCFC 225 0.7 

The results in Table 6 indicate HCFC 2256 removed the contamination to an acceptable level of 

1 mg/ft2. The outstanding flight hardware qualification items will be evaluated in FY 00. In summary 

HCFC 225G is an excellent cleaning and verification solvent for common External Tank contaminates. 
EFFECTS OF CRYOGENIC TREATMENT ON THE RESIDUAL STRESS 

AND MECHANICAL PROPERTIES OF AN AEROSPACE ALUMINUM ALLOY 

Po Chen 

IIT Research Institute 

Building 46 12, Marshall Space Flight Center 

George C. Marshall Space Fli ht Center AL 35812 

(256) 544-4 17 1 -1 

Tina Malone 

National Aeronautics and Space Administration 

Building 46 12, Marshall Space Flight Center 

George C. Marshall Space Flight Center, AL 358 12 

(256) 544-9593 @na.malone@msfc.nasa.gov] 

Robert Bond 

IIT Research Institute 

Building 46 12, Marshall Space Flight Center 

George C. Marshall Space Fli ht Center AL 358 12 

(256) 544-8277 +, (rbondmiitn orrr) 

Pablo Torres 

National Aeronautics and Space Administration 

Building 4612, Marshall Space Flight Center 

George C. Marshall Smce Flight Center. AL 358 12 

(256) 544-26 16~ablo.d.torres(msfc.nasa.gov) I 

ABSTRACT 

Investigators at Marshall Space Flight Center (MSFC) are studying the potential benefits of cryogenic 

treatment for aerospace Aluminum (AI) alloys. This paper reports the effects of cryogenic treatment on residual 

stress, tensile strength, hardness, fatigue life, and stress corrosion cracking (SCC) resistance. 

INTRODUCTION 

AI alloys have long been of interest to the aerospace community, due to their modest specific strength, ease 

of manufacture, and low cost. Fusion welding is a common method ofjoining these alloys. However, such 

techniques can generate defects and high residual stresses. Defects are detected with standard nondestructive 

evaluation (NDE) techniques. However, residual stresses may generate cracks following proof testing, adding 

significant costs and schedule delays as repair, inspection, and proof cycles must be repeated. 

Methods are continually being sought to improve the weldability of AI alloys for aerospace applications. 

At MSFC, attempts are being made to determine how cryogenic treatment affects residual stress, tensile strength, 

hardness, high cycle fatigue (HCF), and SCC resistance. Reports published in the United States and Europe suggest 

that cryogenic treatment may have the potential to relieve residual stress without sacrificing tensile strength. 

Treating tool steels at a low temperature near -320 OF (-196 "C) may result in improved mechanical properties, wear 

resistance, dimensional stability, and tool life.'.' Recent claims have also been made that cryogenic treatment can 

improve the material properties of copper, high-temperature alloys, carbides, plastics, and composite material^.^-^ 
TECHNICAL APPROACH 

Cryogenic treatment was applied to an AI alloy that had already been heat treated or welded, as follows: 

Slowly cool without thermal shock to approximately -300 "F (-184 "C). 

Hold at approximately -300 OF (- 184 "C) for 24 hours. 

Reheat slowly without thermal shock to ambient temperature. 

Test temperatures were reduced from ambient to -300 "F (-I 84 "C) using liquid nitrogen (LN?) to 

significantly slow atomic and molecular activity in the material. Slow temperature changes cause thermal 

compression and expansion to occur equally from the core to the surface, releasing residual stresses and 

homogeneously stabilizing the alloy. This process may take 48 hours or longer to keep the entire mass in 

equilibrium throughout temperature cycling. 

EXPERIMENTAL PROCEDURES 

This study used rolled plates with a thickness of 1.85 inch (4.7 cm). The material was solutionized and 

stretched 3'/0 at ambient temperature. Variable Polarity Plasma Arc (VPPA) welding was conducted with the weld 

bead perpendicular to the rolling direction. As-welded and cryogenically treated weld specimens were then 

prepared to allow comparison of test results. Residual stress was measured before and after cryogenic treatment. 

The Bragg law states: 

nh = 2dsin 0 

where n is an angle denoting the order of diffraction, h is the x-ray wavelength, d is the lattice spacing of crystal 

planes, and 0 is the diffraction angle. These measurements allow the residual stress state to be evaluated. Here, the 

X-ray diffraction method was used to calculate the d spacing by measuring the shift of reflected angle 8. 

Tensile tests were performed at ambient temperature using round specimens. SCC specimens were tested 

in the short transverse (ST) orientation at 5Oo/O and 75% of yield strength. Three specimens were tested for each 

condition in a 3.590 NaCl alternate immersion solution per ASTM G44. Unstressed specimens were removed for 

tensile testing after exposures of various durations. 
RESULTS & DISCUSSION 

Residual Stress Analysis 

As-welded specimens contained significant amounts of residual stress near the fusion line in the heat 

affected zone (HAZ). Cryogenically treated specimens showed residual stress reductions of up to 12 ksi in the 

HAZ. Figure 1 shows no significant changes in the weld bead, fusion line, or parent metal. 

rc 

a 

Figure I. Longitudinal residual stress distribution across a VPPA welded panel 

Figure 2 indicates that residual stress was reduced by up to 9 ksi when cryogenic treatment was conducted 

prior to artificial aging for the rolled plate. 

e d 

Figure 2. Residual stress profiles for rolled plate with a thickness of 1.85 inch (4.7 cm), 

with and without cryogenic treatment 
Tensile and Hardness Tests 

r Specimen Sbas Level FOUure 

Condition (VOYS) Rahlo 

50 13 

75 23 

AS-N elded 

Average hardness increased for parent metal that was artificially aged and then subjected to cryogenic 

treatment. No significant differences were seen in tensile strength for as-welded and cryogenically treated 

specimens. 

Highest Residual Days to 

Stress in HA2 FniflUe 

65 

3. 6 

23.9 ksi 

High Cycle Fatigue (HCF) Tests 

HCF testing was performed at ambient temperature for as-welded and cryogenically treated specimens. 

Figure 3 indicates that no noticeable improvements were seen in cryogenically treated specimens. 

Figure 3. HCF strength 

Stress Corrosion Cracking (SCC) Tests 

Table 3 shows significant improvements in SCC lives for cryogenically treated specimens. 

Cryogenically treated 12.2 ksi 
CONCLUSIONS 

The following results were observed for this particular AI alloy after cryogenic treatment: 

I. 

2. 

3. 

4. 

Residual stress was reduced by up to 12 ksi in the HAZ of weld specimens and by up to 9 ksi in parent metal. 

Significant improvements in SCC performance were seen for weld specimens. 

Minor increases in tensile strength and hardness were noted for parent metal. 

No significant changes were found in tensile properties for weld specimens or in fatigue properties 

for parent metal. 

REFERENCES 

1. 

2. 

3. 

Collins, D.N. “Cryogenic Treatment of Tool Steels.” ildvanced Materials & Processes, 154: 6 (December 

Kamody, D.J. “Using Deep Cryogenic to Advantage,” Advanced Materials & Processes. 154:4 (October 1998): 

Gary, J. “A Review of Deep Cryogenic Treatment of Steel.” Spring 1999. Department of Mechanical 

Engineering, University of Texas at Austin. <http://ccwf.cc.utexas.edu/-jwgary/cryo/title.html>. Accessed 

April 1999. 

Gillin, J.P. “Cryogenically Treated Electrical Contacts.” US Patent No. 5442929, 1995. 

Brunson, R.W. “300 Below, Inc.” Home page. <www.300below.com>. Accessed April 1999. 

1998): 13-27. 

2 15-21 8. 

4. 

5. 
Toughness of Ultra High Strength AF1410 Type Steels 

4 12-268-3593; 

Lwmg@andrew.cmu.edu 

I. Introduction: 

This paper focuses on low to medium carbon secondary hardening steels in which the secondary hardening 

response is enhanced by cobalt additions. These steels are associated with both high strength and remarkably high 

toughnesses at these strength levels. The first steels of this type were the steels HP9-4-20 and HY180. The steel 

HY I80 has been the basis for further development of steels in this class. such as AF1410 and AerMet 100. 

Factors which influence the toughnesses of these steels when the fracture mode is ductile or micro-void 

coalescence are discussed. Ductile fracture is emphasized because high upper shelf toughness can significantly 

improve toughness at test temperatures in the transition region where the toughness increases with increasing test 

temperature. When fracture is ductile the toughness is influenced by both the fine-scale microstructure and the 

inclusion particles distributed through the fine-scale microstructure. While these steels have fracture resistant finescale microstructures, inclusions can degrade the inherent toughness of the fine-scale microstructures. One can 

minimize the detrimental effects of inclusions on toughness by minimizing the inclusion volume fraction. by altering 

inclusion type to achieve the largest possible inclusion spacing when the inclusions are not resistant to void 

nucleation or by altering inclusion type to make the inclusions resistant to void nucleation. 

To getter sulfur as inclusions which are resistant to void nucleation one can use small titanium additions to 

form particles of titanium carbosulfide (TizCS). These particles are much more resistant to void nucleation than are 

particles of other sulfide types such as MnS, CrS or La2O2S. This resistance of particles of TICS to void nucleation 

leads to large improvements in toughness in HYI80, a steel with a carbon content of 0.10 wt.92. In the last section of 

this paper the results of recent studies of the effects of gettering sulfur as TICS on toughness as a function of carbon 

content at a constant inclusion volume fraction are reported. 

3. Development of ultra high strength secondary hardening steels of high toughness: 

Developed by Speich and coworkers[ 181, HY 180 has a nominal composition of 0.10 wt.% C, 10 wt.74 Ni. 8 

wt.% Co, 2 wt.% Cr and 1 wt.% Mo. The Charpy impact energy, yield strength and ultimate tensile strength of a heat 

of HY 180 steel are plotted as a function of tempering temperature for a five hour temper in Figure 1. The yield 

strength increases with increasing tempering temperature to a maximum of about 1250 MPa, reached after tempering 

at 510°C. Tempering at temperatures greater than 510°C for five hours results in a decrease in the yield strength. 

The Charpy impact energy decreases with increasing tempering temperature when tempered above 300°C and has a 

nunimum on tempering at about 425°C. As the tempering temperature is increased above 425°C. the Charpy impact 

energy increases with increasing tempering temperature. After tempering at 425°C the only intra-lath carbides 

observed were cementite; the cementite particles had a lath shape and a length of about 200 nm. After tempering at 

5 10°C for five hours Speich et ai.[ 18lobserved intra-lath precipitation of needles of M2C, but no intra-lath cementite. 

The needles of M2C were about IO nm in length. Speich et al. concluded that when the steel is tempered at 510°C the 

fine alloy carbides contribute substantially to the strength of the alloy and that maximum toughness is obtained only 

when all of the coarse intra-lath cementite particles have been replaced by the fine particles of M?C. 

Speich et ai.[ 181 found that cobalt additions enhanced the secondary hardening response and they attributed 

this to the following effects of cobalt. First, they noted that cobalt additions delayed recovery to higher tempering 

temperatures and suggested that the resulting higher dislocation densities would provide a greater number of 

nucleation sites for M2C precipitation which should lead to smaller and more closely spaced particles of MC and 

hence to higher strength. Further, they pointed out that cobalt additions can lead to a finer M2C dispersion by 

increasing the activity of carbon. leading to a greater M?C nucleation rate and ultimately a higher strength. Speich et 

al. [ 181 also investigated the effects of varying amounts of chromium and molybdenum on toughness and strength as 

a function of tempering temperature and time and noted that higher chromium results in more rapid coarsening of the 

alloy carbides and shifts the secondary hardening peak to lower tempering temperatures. Increasing the molybdenum 

has the opposite effect. They concluded on the basis of strength and toughness that, at a carbon level of about 0.12 

wt.76. the optimum amounts of chromium and molybdenum were 2 and 1 wt.9%, respectively. 
- 1326. 

3 

(s' 

_c 

g izm e 

e 

G I I3XJ 

8 303 

i; cx3 

lmpermg Temperature PCi 

Figure 1. Charpy impact energy, yield strength and ultimate strength as a function of tempering temperature for a 

heat of HY 180 steel.[4] 

AF1410 was developed by General Dynamic[l3] using the principles outlined by Speich et a1.[18] and has 

the composition 0.16 wt.% C, 14 wt.% Co, 10 wt.% Ni, 2 wt.% Cr and 1 wt.% Mo. This steel, like HY180. is 

normally tempered for five hours at 510°C and achieves a yield strength of about 1500 MPa after this tempering 

treatment. The higher strength of AF1410 is attributed to the higher carbon and cobalt levels. The steel AF1410M 

has a nominal composition identical to that of AF1410 except for the carbon content, which is increased to 0.20 

wt.%. When AF1410M is tempered for five hours at 510°C it has a yield strength of 1575 MPa. The Charpy impact 

energy and yield strength of a heat of AF1410 are plotted as a function of tempering temperature in Figure 2a. In 

AF1410 the maximum yield strength is obtained after aging at 475°C. not after aging at 510°C as observed for 

HY 180. As observed for HY 180 steel the Charpy impact energy of AF1410 has a minimum after aging at 425°C and 

increases with increasing tempering temperature for aging temperatures above 425°C. This minimum in toughness 

coincides with the minimum in the retained austenite in the microstructure. as shown in Figure 2b. 

Figure 2. a) Charpy impact energy and yield strength and b) Volume percent retained austenite as a function of aging 

temperature for -1410 steel.[8] 

Subsequent to the development of AF1410 and AF1410M. Carpenter Technology developed an even higher 

strength version of this alloy type[l5]. The nominal composition of this alloy, called AerMet 100, is 0.24 wt.% C, 

13.4 wt.% Co, 11.5 wt.% Ni, 3 wt.% Cr and 1.2 wt.% Mo. The yield strength and Charpy impact energy of oil 

quenched AerMet 100 are plotted as a function of tempering temperature in Figure 3. As for AF1410, the maximum 

in the yield strength is obtained after tempering at 475°C. The Charpy impact energy also has a minimum on 

tempering at about 425°C. However, the decrease in strength associated with increasing the tempering temperature 

from 475°C to 510°C is much greater for AerMet 100 than for AF1410. 
Figure.3. Charpy impact energy and yield strength as a function of tempering temperature for oil quenched 

AerMet 100 steel.[l6] 

The primary objective in the development of new alloys of this class has been to increase strength while 

achieving the highest possible toughness. The primary approach taken to increasing the strength of these steels has 

been to increase the carbon content which changes the fine-scale microstructure in a number of ways. First, if all of 

the carbon is precipitated as MK then one would expect. if coherency strains remain constant, that the strengthening 

due to M2C precipitation would increase as the square root of the carbon content, which is consistent with the results 

obtained by Speich et al.[ 181 on the effect of carbon content on yield strength in alloys of the HY 180 composition. 

Second. increasing the carbon content increases the amounts of inter-lath cementite and intra-lath cementite in the 

microstructure after tempering at 51OoC.[ 101 While no intra-lath cementite is observed after tempering of HY 180 at 

S10"C. there is cementite present in AF1410 steel and the amount of cementite increases as the carbon content is 

further increased. with a particularly large increase when the carbon content is increased from 0.20 to 0.25 wt. 5%. 

In addition. increasing carbon should increase the volume fraction of carbides inherited from the austenitizing 

temperature, the amount of retained austenite and the extent of twinning of the martensite. 

3. Microstructure and toughness: 

When a measure of toughness or ductility is plotted as a function of test temperature for a given 

microstructure the following behavior is normally observed. At low test temperatures the toughness is low and 

remains relatively constant as the test temperature is increased; this region is often referred to as the lower shelf. For 

sufficiently high test temperatures the toughness is high but remains constant as the test temperature is varied: this 

region is often referred to as the upper shelf. Between these two ranges of test temperature there is a region where 

the toughness increases relatively quickly with increasing test temperature. At test temperatures above this transition 

region the fracture mode is normally ductile. For test temperatures below this transition region the fracture mode is 

normally intergranular or a form of cleavage. In the transition region both ductile fracture and brittle fracture modes 

are observed with the amount of ductile fracture increasing with test temperature. 

Ductile fracture is the growth and coalescence of voids typically nucleated at second phase particles. In a 

given material several particle types can be present. Normally, there are particle types at which voids are nucleated 

first, either by particle fracture or by separation of the particle-matrix interface. These particles are referred to as 

primary particles. Voids nucleated at primary particles either grow to impingement or coalesce by a void sheet 

mechanism. Void sheet coalescence [SI of the voids nucleated at the primary particles requires fracture of the 

ligaments between these voids, often by the coalescence of voids nucleated at secondary particles, which are 

particles more resistant to void nucleation than the primary particles and at which voids are nucleated much later in 

the fracture process. 
In steels the primary particles are the inclusions which, in many steels, are sulfide and oxide particles. The 

inclusions are embedded within a fine-scale microstructure. The secondary particles, considered to be part of the 

fine-scale microstructure, include the fine carbides, nitrides and carbonitrides inherited from the austenitizing 

temperature and particles precipitated on tempering. Secondary particles directly influence fracture if they nucleate 

voids. Secondary particles inherited from the austenitizing temperature can indirectly influence toughness by pinning 

austenite grain boundaries during austenitizing and thus influence austenite grain size. Secondary particles 

precipitated on tempering can influence the flow behavior of the material. 

When fracture is ductile the toughness of steel is determined by both the fine-scale microstructure and the 

inclusions. The fracture toughness of ultra high strength steels can be improved by both developing fracture resistant 

fine-scale microstructures and by minimizing the detrimental effects of inclusion particles on toughness. For a fixed 

inclusion type the toughness can be increased by decreasing the inclusion volume fraction.[l21 However, at a fixed 

inclusion volume fraction the inclusion type can significantly influence toughness because inclusion type can 

influence inclusion spacing[ 3,6] and the void nucleation resistance of the inclusion particles. [9,14] The fine-scale 

microstructure can influence toughness by influencing matrix strength which can influence the strain at which voids 

nucleate, the rate of growth of voids nucleated at primary particles and also by influencing coalescence. 

For il fixed fine-scale microstructure the inclusion distribution can influence toughness in the transition 

region because in the transition region the fracture mode is mixed. One would expect the inclusion distributions to 

influence the toughness in the transition region because of their effect on the energy absorbed during ductile fracture. 

Thus one would expect increasing the upper shelf toughness to lead to increases in toughness throughout the 

transition region. 

4. Effects of inclusion distributions on the upper shelf toughness: 

One objective of prior work has been to determine for a given fine-scale microstructure and constant 

inclusion volume fraction how to minimize the detrimental effects of inclusions on upper shelf fracture toughness. 

The plane strain fracture toughness is Kc and is related to 6~, the crack tip opening displacement at ffacture. and JI,, 

the critical value of the J integral at fracture, through the equatio9s & = JI~ / 20,) and JI~ = (Kc)- / E' where E' 

equals Young's modulus, E, for plane stress and E' equals E/( 1 -v-) for plane strain and o,) is the flow stress of the 

material and v is Poisson's ratio.[2.1 11 

The Rice and Johnson[ 171 model predicts that 6c will scale with the inclusion spacing when the inclusion 

volume fraction is held constant. Results with HY180 and AF1410 indicate that increasing the inclusion spacing 

does lead to improved toughness. In this work small inclusion spacings have been achieved by gettering sulfur as 

small particles of CrS or MnS and large inclusion spacings have been achieved by small additions of lanthanum to 

getter the sulfur as large particles of La20S. Xo, the inclusion spacing, is the average nearest-neighbor distance in 

the volume and has been calculated from X, = 0.89Rof "' [I], where is the average inclusion radius and f is the 

inclusion volume fraction. 

The effect of inclusion spacing on the toughness of HY180 steel can be seen by comparing heats A792 and 

GO32 in Tables I through 3. In A792 the sulfur has been gettered as small, closely spaced particles of MnS and in 

heat GO32 the sulfur has been gettered as large. widely spaced particles of La2O.S. The fracture toughness of heat 

A792 is 233 MPadm while that of heat GO32 is 336 MPadm. This increase in toughness is ascribed to the increase 

in inclusion spacing as other microstructural features such as carbides inherited from the austenitizing temperature 

and grain size have not be altered by the chemistry differences required to vary sulfide type. The effect of inclusion 

spacing on the toughness of AF1410 steel can be seen by comparing heats GO31 and CY2 in Tables 4 through 6. In 

GO31 the sulfur has been gettered as small. closely spaced particles of MnS and in heat CY2 the sulfur has been 

gettered as large, widely spaced particles of La?O2S. The fracture toughness of heat GO31 is 158MPadm while the 

toughness of heat CY2 is 199 MPadm. CY2 has considerably higher toughness than heat GO31 even though the 

inclusion volume fraction in heat CY2 is three times greater than that in GO3 1. 

The effect of gettering sulfur as particles resistant to void nucleation on the toughness of HY 180 can be 

assessed by comparing the results for heats GO27 and GO28 which contain no manganese or lanthanum but 0.01 and 

0.02 wt. % titanium, respectively, and in which the sulfur is gettered as Ti2CS to the results for A792 in which the 

sulfur is gettered as MnS and GO32 in which the sulfur is gettered as La202S. The fracture toughnesses of GO27 and 

GO28 were 480 MPadm and 550 MPadm, respectively, and those of the A792 and GO32 were 233 MPadm and 336 

MPadm, respectively. As shown in Figure 4 voids are nucleated at much higher strains when the sulfur is gettered as 

Ti2CS than when voids are nucleated at particles of MnS or La?02S. It is believed the higher toughnesses of the 

titanium modified heats are due to the particles of TiCS being more resistant to void nucleation than particles of 

MnS or Laz02S. However, the titanium additions required to alter sulfide type also influence the carbides inherited 

from the austenitizing temperature and reduce austenite grain size; these changes in fine-scale microstructure could 

play some role in improving toughness. 
Table 1. Chemistries of HY 180 Heats* 

N2**: 02:k* Heat C Ni co Cr Mo Si Mn S P Ti La 

A792 .IO 9.86 7.96 1.98 1.02 .O1 .31 .002 .004 .004 <.002 3 6 

GO32 .I? 9.88 8.07 1.99 1.0 .01 .01 .001 .003 .003 .005 3 8 

GO28 .I 1 9.88 8.07 1.99 1.00 .01 .01 .001 .003 .021 <.002 1 4 

GO27 .I 1 9.90 8.02 1.99 1.01 .01 .01 .001 .003 .012 <.002 1 12 .. " in wt~l : +* in wt. ppni 

Heat Sulfide Type f Ro(Clm) Xo(pn) 

A792 MnS 0.0002 I 0.16 2.4 

GO3 2 La20rS 0.00015 0.44 7.5 

GO28 Ti2CS 0.00019 0.10 1 .S 

GO27 Ti,CS 0.00011 0.10 1.9 

f = volume fraction; 

Table 2. Inclusion Characteristics of HY180 Heats 

= average radius; Xo = spacing 

Table 3. Mechanical Properties of HY 180 Heats 

cv 

'IC (J) 

9s 174 

Heat YS UTS Fracture n JIC 

(MPa) ( MPa) Strain (MPa-m) (MPa m) (pm) 

11\79? 1708 1343 1.39 0.043 0.25 233 

GO32 1236 1379 1.54 0.048 0.52 336 199 213 

GO28 I240 1369 1.58 0.044 1.06 480 406 267 

GO27 1260 1392 1.65 0.046 1.35 550 509 290 

K17 

Table 4. Compositions of AF1410 Heats * ** 0 x* Heat C Ni co Cr Mo Si Mn S P Ti La N2 2 

GO31 0.17 9.88 13.90 2.06 1.10 .01 .28 .001 .002 .004 - 3 1 

CY2 0.16 10.10 14.04 2.10 1.00 .03 .03 .004 .004 .002 .006 3 9 

G618 0.16 9.98 14.10 2.01 1.01 .01 <.01 .001 .003 .013 - 27 

wt%, ** wt pprn 

Table 5. Inclusion Characteristics of AF1410 Heats 

Heat Sulfide type f Ro (Pm) Xo(pm) 

G03 I MnS 0.00014 0.1 1 1.90 

CY2 La?OS 0.00042 0.64 7.60 

G618 TICS O.ooOo67 0.069 1.15 

f = volume fraction: & = average radius; Xo = spacing 

Table 6. Mechanical Properties of AF1410 Heats 

Heat YS UTS Fracture n JIC 'IC KIC CV 

(MPa) (MPa) Strain (MPa-m) (p) (MPadm) (J) 

GO31 (MnS) 1505 1661 1.22 0.048 0.123 39 158 70 

CY2 (La202S) 1489 1666 1.24 0.058 0.209 66 199 88 

G618 (TICS) 1472 I672 1.43 0.55 175 347 205 

Titanium additions would appear to have a similar effect on the toughness of the higher strength steel 

AF1410. The fracture toughness of heat G618 in which the sulfur is gettered as TizCS is 347MPadm while the 

fracture toughness of the heat GO31 in which the sulfur is ettered as MnS is 158 MPadm and the toughness of heat 

is much lower than the inclusion volume fractions of heats GO31 or CY?. Thus, the results obtained using G618 do 

not conclusively show that gettering sulfur as Ti2CS can lead to improved fracture toughness in AF1410. For this 

reason the effects of titanium additions on the inclusion void nucleation behavior and toughness in AF1410 type 

steels have been explored as a function of carbon content at sulfur levels similar to those obtained in conunercial 

practice and our previous heats of HY 180 steel. The results of this study will be covered in section six. 

CY2 in which the sulfur is gettered as La202S is 199 MPa f m. However, the inclusion volume fraction of heat G618 
0 25 650 075 1 OQ 1 25 

Plastic Strain 

180 

160 

140 

120 

loo 

80 

60 

40 

30 -- 

0 

Figure 4. The void + inclusion volume fraction normalized by the inclusion volume fraction plotted as a function of 

strain for heats of HY 180 steel in which the sulfur is gettered BS MnS (A792), La202S (GO32) and TiKS (G028). 

Voids have nucleated when this ratio is greater than one.[7] 

- .CY2 

- A811 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

-- 

,"":"""":"":"":'":""~'''~ 

5. Effects of inclusion distributions on toughness in the transition region: 

Charpy impact energies are given as a function of test temperature in Figure 5 for heats CY2 and 81 1 of 

AF1410. In heat CY2 the sulfur is gettered as La202S particles and the inclusion volume fraction was 0.00043. In 

heat 81 1 the sulfur was gettered as TICS and the inclusion volume fraction was 0.00012. The chemistry, inclusion 

characteristics and mechanical properties of heat CY2 are summarized in Tables 4, 5 and 6, respectively; those of 

heat 81 1 are summarized in Tables 7, 8 and 9, respectively. Heat 81 1 which has the higher upper shelf toughness has 

higher toughness throughout the transition region. Since heat 81 1 has a lower inclusion volume fraction than heat 

CY2 the higher toughness of heat 81 1 in the transition and upper shelf ranges cannot be attributed entirely to the 

differences in sulfide type. However, the data does demonstrate that raising the upper shelf toughness can result in 

higher toughnesses throughout the transition region. 

A 

A 

A 

. 

A . 

. 

-250 -200 -150 -100 -50 0 50 100 150 

Figure 5. Charpy impact energy versus test temperature for heats CY2 and 81 1 of AF1410. 
6. Effects of carbon content on the toughness of AF141O type steels: 

In section 5 it was noted that gettering sulfur as Ti2CS might be effective in raising the toughness of 

AFIJIO. but the heat of AF1410 initially used, heat G618, had an exceptionally low inclusion volume fraction; thus 

it was difficult to deternline the extent to which gettering sulfur as TiXS improved the toughness of AF1410. 

Consequently. "control" heats were prepared at three carbon levels (0.16, 0.20 and 0.25 wt. %) in which the sulfur 

was gettered as TizCS and as CrS but which contain sulfur in amounts similar to those observed in the HY 180 heats, 

0.0010 wt.%.The sulfur was gettered as TiCS in heats 811, 812 and 813 and. as shown in Table 7, these heats had 

sulfur, nitrogen and oxygen levels very similar those in the HY 180 heats. A second series of alloys was prepared 

with no titanium, manganese or lanthanum additions and the sulfur in these heats was gettered as CrS. The 

chemistries of these three heats. 91.92 and 93. are given in Table 7. 

The only sulfur-rich particles found in heats 8 1 1. 8 I2 and 8 13 were Ti2CS. The TbCS particles were found 

to have a large size range, with particle diameters varying from 0.05 pm to 3.8 pm. The inclusion characteristics for 

heats 8 1 1, 8 11 and 81 3 are given in Table 8. The volume fraction of inclusions in the three heats are very similar. 

However, differences emerge when the cumulative volume fractions of these heats are plotted as in Figure 6. 

Particles greater than 0.5 pm in dimension make the largest contribution to the volume fraction of heat 813. while 

heat 81 1 has the finest particle distribution. Heats 812 falls between heats 81 1 and 81 3. These results suggest that 

the proportion of large particles of TiXS increases with increasing carbon content. 

In heats 9 I, 92 and 93 all of the sulfur is gettered as CrS. The chromium sulfides are spherical in crosssection and have a much smaller size range than the TiKS particles, with particle diameters varying from 0.05 to 

approximately 0.30 pm. The inclusion characteristics for the heats 91, 92 and 93 are summarized in Table 8. 

Inclusion volume fractions for these heats are similar but smaller than those of heats 8 1 1, 8 12 and 8 13. 

Table 7. Compositions of AFl4lO Control Heats * 

Ti La &*: 02** Heat C Ni co Cr Mo Si Mn S P 

81 1 0.16 10.20 13.93 2.01 1.00 0.01 0.01 .0010 0.001 0.02 - 15 

812 0.20 10.15 13.95 2.02 1.01 0.01 0.01 .0008 0.001 0.02 - 26 

813 0.25 10.14 13.94 2.01 1.01 0.01 0.01 .0010 0.001 0.02 - 14 

91 0.16 9.98 13.99 1.99 1.03 0.01 0.01 .0012 0.001 <0.01 - 16 

92 0.20 10.00 13.99 2.00 1.04 0.01 0.01 .0011 0.001 <0.01 - 16 

* wtq. ** wt ppm 

93 0.24 9.96 14.00 2.01 1.02 0.01 0.01 .0013 0.001 <O.Ol - 2 5 

Table 8. Inclusion Characteristics of AF1410 Control Heats 

Heat Sulfide type f Ro Wm) Xo(pm) 

81 I TizCS o.oO0 120 0.079 I .42 

811 TICS O.ooOo9 1 0.075 I .49 

813 TiCS 0.000106 0.072 1.36 

91 CrS O.oooO65 0.070 I .55 

92 CrS O.ooOo78 0.075 1.55 

93 CrS O.ooOo88 0.072 1.44 

f = volume fraction; R, = average radius: Xo = spacing 

Table 9. Mechanical Properties of AFIJ10 Control Heats 

CV 

(J) 

Heat YS UTS Fracture JIC &IC 

81 1 (Ti,CS) 1530 1610 1.4 0.251 80 235 176 

812 (Ti,CS) 1590 1730 1.3 0.156 47 177 103 

813 (Ti,CS) 1690 1830 1.1 0.089 25 135 68 

91 (CrS) 1490 I650 1.3 0.137 44 I68 107 

92 (CrS) 1610 1770 I .2 0.084 25 I32 68 

93 (CrS) 1730 1880 1.1 0.046 13 95 43 

KIC 

( MPa) (MPa) Strain (MPa-m) (pm) ( MPaV m ) 
500- 

E 

GO37 . Ti,CS 

GO28 CrS 

MnS 

. 

300 

100 

0 

1200 1300 1400 1500 1600 1700 1800 

Yield Strength I MPa 

Figure 7. The fracture toughness plotted as a function of yield strength for HY180 and AF1410 at carbon levels of 

0.16,0.20 and 0.35 wt.% when the sulfur is gettered as MnS, CrS and TiCS. 

The higher toughnesses of the heats in which the sulfur is gettered as TizCS are associated with the particles 

of TICS being more resistant to void nucleation than particles of MnS or CrS. Void generation curves for the 0.16 

wt. % carbon heats in which the sulfur is gettered as CrS (heat 9 1 ) and in which sulfur is gettered as TiCS (heat 8 1 I ) 

are compared in Figure 8. While voids are generated at very low strains at the inclusions in the CrS heat, void 

generation does not become apparent until a strain of about one for the TizCS heat. There are microstructural 

differences between these two heats other than sulfide type which could influence toughness. The prior austenite 

grain size and martensite packet size are larger in heat 9 1 than in heat 8 I 1 and it is possible that the toughness of heat 

91 could be improved by a refinement of prior austenite grain size because the inclusions in heat 91 are small and 

closely spaced. It has been shown in 0.07 wt.% carbon / 9 wt.% nickel steels that increasing austenite grain size is 
detriniental to toughness when the inclusion spacing is small, as when the sulfur is gettered as MnS or CrS. but has 

very little effect on toughness when the inclusion spacing is large, as it is when the sulfur is gettered as Laz0.S.[7] 

i 

-! 0.0 02 0.4 0.6 6.8 1 .o 1 rC 

E'tm$ic Strain 

Figure 8. The void + inclusion volume fraction normalized by the inclusion volume fraction plotted as a function of 

strain for heats of AF1410 in which the sulfur is gettered as CrS (91) and TbCS (81 1). Voids have nucleated when 

this ratio is greater than one. 

A number of factors could contribute to the toughness decreasing more rapidly with increasing yield 

strength when the sulfur is gettered as Ti,CS than when the sulfur is gettered as MnS or CrS. First, inclusion void 

nucleation resistance does not change as the carbon level is increased from 0.16 to 0.25 wt. 96 when the sulfur is 

gettered as CrS; void generation curves for heats 91 and 93 are the same. However, the strains at whch voids are 

generated at inclusions decreases with increasing carbon content when the sulfur is gettered as Ti,CS. Void 

generation studies camed out at elevated temperatures for 8 13 and at low temperatures for heat 8 I 1 suggest that the 

decreasing void generation resistance with increasing carbon level is due, not to an increase in strength, but rather to 

the effect of carbon on the size distribution of TizCS particles with void generation occumng at lower strains as the 

number of larger particles of Ti,CS increases. Thus the effect of carbon content on TizCS size appears to be one 

reason that the toughness decreases more rapidly with increasing strength when the sulfur is gettered as TizCS than as 

CrS. 

However. that the toughness decreases more rapidly with increasing strength when the sulfur is gettered as 

Ti,CS than as CrS cannot be attributed entirely to the effect of carbon on TICS size. A number of factors suggest 

that fine-scale microstructural changes play a large role in this decrease in toughness as the carbon level is increased 

from 0.16 to 0.25 wt.%. To eliminate particles of TizCS specimens were first solution treated at 1390°C. a 

temperature sufficient to dissolve all of the titanium carbosulfides, then water quenched and then given the standard 

heat treatment. The effects of this heat treatment on Charpy impact energy are summarized in Table 9. 

Table 9. The Effects of High Temperature Solutionizing on Charpy Impact Energies 

Heat Charpy Impact Energy (J) 

Standard 139O"C/lhr +Water Quench + 

Heat Treatment Standard Heat Treatment 

81 1 176 240 

812 I03 143 

813 68 80 

The increases in Charpy energy for heats 81 1, 812 and 813 were 64 J, 40 J and 12 J, respectively. The 

microstructures of the materials which were first solutionized at 1390°C differed from those receiving just the 

standard heat treatment in that no large titanium carbosulfides were present, no undissolved carbides inherited from 

the austenitizing temperature could be detected and the austenite grain sizes were quite large, indicating that the 

standard heat treatment were insufficient to refine the austenite grain size established by first solutionizing at 
1390°C. Both removing the large titanium carbosulfides and the carbides inherited from the austenitizing 

temperature should lead to improved toughness as observed. However, the degree to which removing these particles 

improves toughness diminishes as the carbon content increases. In fact, at the carbon level of 0.25 wt. 5% this heat 

treatment results in an increase in the Charpy impact energy of only 12 J. These results suggest that fine-scale 

microstructure dominates the fracture behavior at the higher carbon level and that fine-scale microstructural changes 

due to increasing carbon content play a substantial role in determining the decrease in toughness as the carbon level 

is increased. 

Fine-scale microstructural features which could change with increasing carbon content and which might 

influence toughness include retained austenite content, the amount and nature of the carbides inherited from the 

austenitizing temperature, the amount of inter-lath and intra-lath cementite and the amount of twinning. No 

austenite could be detected in heats 8 1 I, 812, 813, 91. 92 and 93. While the number density of carbides inherited 

from the austenitizing temperature does increase with increasing carbon content, eliminating such carbides through 

the heat treatment beginning with the solutionizing at 1390°C does not have a significant effect on toughness at the 

0.25 wt. % carbon level. Measurements of the amounts of inter-lath and intra-lath cementite in steels of the AF1410 

type indicate that the amount of cementite does increase with increasing carbon content. However, no cementite was 

found on extractions taken from fracture surfaces. This result is certainly contrary to our expectations. While it is 

possible that the cementite particles in these materials influence fracture indirectly, they to do not appear to nucleate 

voids. While our results suggest that fine-scale microstructure becomes increasingly dominant in determining 

fracture behavior as the carbon level is increased the aspects of the fine-scale microstructure which are active have 

not been identified. 

7. Acknowledgments: 

authors also appreciate the preparation of materials by Carpenter Technology and by Teledyne-Allvac. 

The support of the National Science Foundation under DMR-97 I260 is gratefully acknowledged. The 

8. References: 

1. Ashby, M F and Ebeling, R, Trans. AIME. 235 (1966), 1396-1404. 

2. Begley, J A and Landes, J D, in Fracture Toughness, ASTM STP 514, American Society for Testing and 

Materials, Philadelphia, PA, (1974). 201. 

3. Birkle, A J, Wei, R P and Pellissier, G E, Trans. ASM, 59, (1966), 981-990. 

4. Bray, J W Maloney, J L, Raghavan, K S. Garrison, W M, Met. Trans., 22A, (1991). 2277-2285. 

5. Cox, T B and Low, J R, Met. Trans., 5A, (1974). 1457-1470. 

6. Garrison, W M. Met. Trans., 17A, (1986), 669-678. 

7. Garrison. W M, Wojcieszynski, A L and Iorio, L E. in Recent Advances in Fracture (eds. Mahidhara, R K, 

Geltmacher, A B, Matic, P, Sadananda, K j. Orlando, Florida. Feb 10-13, TMS, (1997). 361-372. 

8. Handerhan, K J, Garrison W M and Moody, N R, Met. Trans., 20A, (1989). 105-123. 

9. Hippsley, C A and Druce S G, Acta Metall.. 31. (1983), 1861-1872. 

IO. Iorio, L E. Maloney, J L and Garrison, W M, in 40th Mechanical Working and Steel Processing Conference, 

Pittsburgh. Oct. 25-28, Iron & Steel Society, (1998), 901-919. 

11. Knott, J F, in Fundamentals of Fracture Mechanics, Buttenvorths, London, ( 1973). 

12. Knott. J F. Metal Science, 14, (1980), 327-336. 

13. Little, C D and Machmeier. P M, Development of a Weldable High Strength Steel. Report AWL-TR-75-148, 

(1975) 

14. Maloney, J L and Garrison, W M, Scripta Met., 23. (1990), 2097-2100. 

15. Novotny, P M and Dahl, J M, in 32nd Mechanical Working and Steel Processing Conference. Cincinnati, Ohio, 

Oct. 21-24, 1990, Iron & Steel Society, (1991), 275-281. 

16. Novotny. P M, in Gilbert R. Speich Symposium (eds. Krauss, G and Repas, P E.), Montreal, Canada, Oct. 25- 

28, Iron & Steel Society, (1992), 215-236. 

17. Rice, J R and Johnson, M A, in Inelastic Behavior of Solids, (eds. Kanninen, M F. Adler. W G. Rosenfield, A R 

and Jaffee, R I) McGraw-Hill, New York, (1970). 641-672. 

18. Speich, G R. Dabkowski, D S and Porter, L F. Met. Trans., 4, ( 1973), 303-3 15. 
- SEGREGATION BEHAVIOR OF SULFUR AND OTHER IMPURITIES , 

ONTO THE FREE SURFACES OF ED-NI DEPOSITS 7 

Binayak Panda 

IIT Research Institute 

Building 4628, Marshall Space Flight Center 

George C. Marshall Space Fli ht Center, AL 358 12 

(256) 544-6349 

and 

Gregory Jerman 

National Aeronautics and Space Administration 

Building 46 12. Marshall Space Flight Center 

George C. Marshall Space Flight Center, AL 35812 

ABSTRACT 

(36) 544-5346 5 

Most researchers attribute grain boundary embrittlement in electro-deposited Nickel (ED-Ni) to the 

presence of small quantities of Sulfur as an impurity. It occurs in a highly mobile form that segregates to the grain 

boundaries. Evaluation of Sulhr segregation requires that a sample be fractured through the grain boundaries. 

However, this action may not always be possible. ED-Ni is inherently tough at ambient temperature, especially if a 

low level of Sulfur was intentionally maintained. 

A new method was developed to study Sulfur and other migrant species to the grain boundaries, which also 

nligrate to free surfaces. A test specimen is heated by a quartz lamp within the sample preparation chamber, 

allowing the mobile species to migrate to polished free surfaces. There the mobile species are analyzed using X-ray 

photoelectron spectroscopy (XPS) also known as Electron Spectroscopy for Chemical Analysis (ESCA). 

INTRODUCTION 

ED-Ni is one of the structural materials used in the main combustion chamber (MCC) of the Space Shuttle 

Main Engine (SSME). During manufacture, a Nickel sulfamate bath is used to obtain a deposit of high-purity 

Nickel. Table 1 shows impurity levels commonly seen in the composition of ED-Ni, given in parts per million 

(ppm).' 

Table 1 - Impurity levels in ED-Ni 

(PPm)' 

Carbon I Copper 1 Iron I Manganese I Silicon I Cobalt I Hydrogen 1 Oxygen I Nitrogen I Sulfur 

50 I <loo I <loo I <5 I <10 I 1000 I 8 I 20 I 6 I 10 

Functional characteristics can be seriously impaired by some impurities, even at very low levels, especially 

in material exposed to elevated temperatures during annealing or welding. High-temperature exposure promotes 

diffusion of some impurities to grain boundaries, which may result in grain boundary embrittlement characterized by 

loss of ductility at high temperature. Most researchers'" associate such degraded mechanical properties with Suhr 

segregation, while others attribute them to Carbon reacting with Oxygen to form Carbon Monoxide at grain 

boundaries.' Both groups consider Sulfur (in the absence of Oxygen) to be the most important cause of grain 

boundary embrittlement. 
Sulfur has very low solubility in Nickel, with strong segregation tendencies toward grain boundaries. Even 

at the small ppm level, Sulfur present in a bulk composition can segregate up to several atomic percentages at the 

grain b~undaries.~ Sulfur is gettered by other elements such as manganese, magnesium, and calcium, which prevent 

its migration to the grain boundaries. 

Measurement of grain boundary Sulfur is an important means of predicting embrittlement. All previous 

work has made such measurements using Auger electron spectroscopic analy~is,'.~ requiring exposure of the grain 

boundaries. This action is usually accomplished by introducing large quantities of Sulfur that induce the sample to 

break easily within the Auger sample preparation chamber. 

EXPERIMENTAL PROCEDURE 

This paper describes a new method to measure the amount of diffusing species onto a free surface. This 

phenomenon is considered to be directly related to the amount of diffusing species present on the grain boundaries. 

XPS was used to identify and quantitatively measure segregating species on a polished surface. This technique 

allowed the analysts to use a large diameter monochromatic X-ray beam (800 micrometers) for better sensitivity. 

They were also able to use X-rays as the excitation source in order to prevent heating effects and evaluate polished 

samples instead of fractured samples. 

Both mounted and unmounted samples were analyzed using an SSX-100 ESCA instrument. Mounted and 

polished ED-Ni samples were introduced into the sample preparation chamber and allowed to outgas. The samples 

were then introduced into the main analytical chamber. Selected areas of each polished surface were then cleaned 

using an argon ion sputter gun. After cleaning, the samples were removed from the analytical chamber, 

reintroduced into the sample preparation chamber, and heated by a quartz lamp for 2 hours. See Figure 1 for heating 

and cooling curves. After about 4 hours, the cooled samples were reintroduced into the analytical chamber where 

the cleaned regions were analyzed for possible migration of species. 

RESULTS 

The limits of elemental sensitivity for XPS are generally in the same range as that of Auger. An element 

must be present as at least a fraction of a percent in order to be detected. Elements detected on the clean surface are 

assumed to be species segregating from inside the material. Several runs were made to confirm this phenomenon, as 

well as to eliminate spurious deposits from the vacuum atmosphere. Therefore two groups of results were obtained. 

The first was to ascertain the origin of various species found on the sample surface, the second to provide 

quantitative determination of these species. 

To establish this method's effectiveness, analysis was conducted on a sample taken from an MCC (SM 

6014). It was mounted in Bakelite and then polished for microstructural and elemental analysis. Combustion 

analysis was used to determine that it contained 3 ppm bulk Sulfur. This low amount permitted the XPS method of 

detection to be effective if Sulfur segregation occurs to the free surface of the sample. 

A quartz lamp was used to heat the mounted and polished sample in the XPS sample preparation chamber 

for 2 hours to remove volatile matter. After cooling, the sample was introduced into the main analytical chamber for 

analysis. Regional scans were taken between the 150 and 350 eV binding energy range at two locations for an 

iteration of 10 times each. These scans included positions for Carbon and Sulfur peaks. Table 2 indicates that these 

locations produced nearly identical scans showing both Carbon and Sulfur on the sample surface. Then the second 

location was sputtered with argon ions for 2 minutes to remove adsorbed contaminants. After sputtering, the Sulfur 

peak was eliminated and the Carbon peak reduced. The sample was removed to the sample preparation chamber 

again, heated with a quartz lamp for 1 hour and then reintroduced into the analytical chamber. Analysts noted a 

small Sulfur peak and a significant Carbon peak, although not as large as the one seen after heating for 2 hours. 

Both peaks were removed by 2 minutes of sputter with the argon gun. 
Tem pera ture 

(Fahrenheit) 

300 

250 

200 

150 

100 

50 

0 

0 100 200 300 400 

Time (minutes] 

Figure 1 - Sample heating/cooling cycle 

Due to sample outgassing, the pressure was elevated to 2 x torr inside the analytical chamber. An 

attempt was made to determine whether the appearance of Carbon and Sulfur lines was due to adsorption of gaseous 

species from the chamber atmosphere. The sample surface was cleaned by sputter with the argon gun. left inside the 

analytical chamber for 4 hours, and then scanned for Carbon and Sulfur. No evidence of Sulfur was seen, although 

the Carbon peak had grown somewhat. It was inferred that, for the Bakelite-mounted samples, surface Carbon 

content could increase either from the atmosphere or through diffusion from inside the sample. In another attempt, 

the sample was cleaned and then placed in the preparation chamber. It was heated for 2 hours while shielded from 

direct radiation from the quartz lamp. No Sulfur was observed. Analysts noted the presence of a Carbon peak as 

large as the one produced by direct heating. 

Analysis was conducted on Bakelite-mounted material, as well as on silver paste applied to the mounted 

samples to improve conductivity during electron microprobe evaluations. Each was analyzed twice. Both showed 

broader Carbon peaks, but no Sulfur. Upon cleaning, reheating, and analysis. Sulfur was again detected on the same 

sample. 

Table 2 - Peak Areas for Carbon and Sulfur 

(Preliminary Studies) 
After Sulfur was observed migrating to the clean surface, overall scans were performed between 0 and 

1100 eV to determine whether other species were migrating. During Run #24. regional scans were performed 

between 150 and 350 eV. They showed evidence of Bromine, which was identified from the position of three peaks 

( 182, 189, and 256 eV) and their relative heights. During Run #25, an overall scan was performed from 0 to 550 eV, 

as shown in part in Figure 2. Bromine and Cadmium species were seen with Carbon, Oxygen, Nitrogen, and Sulfur. 

?! 

P 

w 

.. 

Figure 2 - Scan which shows several elements segregating to surface of Sample 6014 

In Table 3, surface analysis is shown in atomic percentages. Carbon and Oxygen covered most of the 

Nickel surface. A sputtered surface shows about 75% Nickel, 10% Nitrogen, 10% Oxygen, and 5% Carbon. These 

percentages are approximate. Their accuracy depends upon degree of surface cleanliness, peak-to-background ratio 

of the peak being evaluated, and the test instrument’s inherent machine characteristics. Here, the standard deviation 

should be around 0.8% for strong lines such as Nickel (IO iterations) and close to 1.8% for Carbon and other light 

elements (1 1 iterations), 

Table 3 - Quantitative Surface Analysis for Sample 6014 

(Atomic Percentages) 

Nickel I Oxygen I Cadmium I Nitrogen 1 Carbon I Sulhr I Bromme 

17.93 10.52 I 0.17 I 4.24 I 59.68 4.71 I 2.75 
Systemic analysis was then conducted on several samples from actual MCC liners, using the methodology 

discussed above. Analysis was conducted on a sample taken from an MCC liner (SM 602 l), which contained more 

bulk Sulfur than was seen in Sample 6014. Sample 602 I was longitudinally sectioned, polished, and then removed 

from the mount to eliminate any elemental interference of species emanating from mounting materials. Combustion 

analysis indicated that it contained 6 to 7 pprn of bulk Sulfur, while the microprobe analysis indicated that it 

contained 3.5-ppni Sulfur. Combustion analysis gives data for the bulk material, whereas the microprobe gives data 

for a region of only a few micrometers on the surface. 

Nickel Osygen Cadmium 

26.90 10.04 0.23 

28.79 9.80 0.20 

Table 3 shows that the sample showed Sulfur, Bromine, and Cadmium. as well as small amounts of 

Chlorine on the surface. Despite higher levels of Sulfur in combustion analysis seen between the two samples, the 

migrating quantity was less than that seen in the 3 ppm material. Several readings were taken on the same sample, 

in order to find out whether segregation might be dependent upon location, previous exposure, or polishing. The 

sample was also repolished and reexamined. Run #36 showed about 1 lhO/b Sulfur on the surface. Afterwards, a 

depth profiling evaluation indicated that Sulfur was present on the surface to a depth of around 0.7 im. Thus nearly 

two monolayers of Sulfur were present 011 the sample surface. 

Nitrogen Carbon Sulfur Bromine Chlorme 

58.03 2.67 2.09 

1.71 54.28 I .84 3.35 

Table 4 - Surface Analysis Results for Sample 6021 

(Atomic Percentages) 

Nickel Oxygen 

26.98 9.33 

25.88 8.93 

Table 5 shows results for a sample taken from the aft area of an MCC liner (S/N 6005) analyzed at two 

locations. Both microprobe and combustion analysis showed very small amounts of Sulfur (-1.2 ppm). 

Cadmium Nitrogen Carbon Sulfiu Bromine Chlonne 

Trace Trace 58.36 2.96 2.38 

Trace 58 89 3.66 2.65 

Another high-Sulfur sample taken from an MCC liner (SM 6018) was analyzed at two locations. Sample 

60 18 contained around 5 to 6 ppm of bulk Sulfur. as confirmed by both combustion and microprobe analyses. Table 

6 reports XPS analysis results indicating the presence of traces of Cadmium and Nitrogen on the surface, in addition 

to Sulfur. 

Table 6 - Surface Analysis Results for Sample 6018 

(Atomic Percentages) 
Analysis was also conducted on a sample taken from an MCC liner (S/N 6016). It contained an 

intermediate amount of Sulfur, with a bulk analysis of approximately 4 ppm. Table 7 shows negligible amounts of 

Cadmium, with Tin seen as one of the species seen migrating onto the surface. 

Nickel Oxygen Cadmium Nitrogen Carbon Sulfur 

23.96 I0.U Trace 3.04 57.80 2.78 

22.28 10.13 Trace 3.89 57.63 3.39 

Bromine Chlorine Tin 

1.68 0.2s 

22.3 0.43 

DISCUSSIONS 

MCC Liner 

Serial Number 

Impurities are common in Nickel sulfamate baths. The common impurities in Nickel deposits are Oxygen, 

Carbon, Sulfur, and Chlorine.’ These impurities occur in amounts that vary largely depending upon the operating 

parameters. Metallic impurities generally Originate as contamination and additives. Such impurities are generally 

present in very small concentrations. Their presence and origins are generally not apparent unless the species are 

specifically sought out. Earlier publications6 discussed possible sources of these species. Here, the XPS used a 

residual gas analyzer in the sample preparation chamber to identify species present in the vacuum chamber. During 

heating, the sample preparation chamber contained Oxygen, Nitrogen, moisture, Carbon dioxide, and Hydrogen 

gases. No additional species were found after heating for 2 hours using gold samples, unlike results for the ED-Ni 

material. 

Sulfur by Combustion Analysis Average Sulfur on Surface 

(ppm) (Atomic Percent) 

Several studies have found Sulfur in Nickel, which is known to segregate to grain boundaries, as well as to 

free surfaces. That phenomenon occurred here after heating to 275 OF. Segregation effects will be faster for hightemperature exposure. The amount migrating to grain boundaries will depend upon how much free Sulfur remains 

after compounding with other elements (e.g., calcium and/or manganese) that may be present in ED-Ni. Several 

readings for Sample 602 1 showed scatter in surface Sulfur compositions. However, average analyses at different 

locations for different liners correspond well with the findings of total Sulfur by combustion and microprobe 

analysis. Table 8 compares average results for surface analysis and combustion analysis. 

6005 

6018 

6016 

While the origin of Cadmium and Bromine is unclear, they may be present in very small quantities in EDNi. However, additional study is needed as to their segregation propensity, in addition to that of Sulfur. 

Investigation is also required to determine whether synergistic effects exist among such segregating species. 

1.2 2.25 

5.5 3.3 1 

4.0 3.08 

Table 8 - Comparison of Average Results for Sulfur 

During Surface Analysis and Combustion Analysis 

CONCLUSIONS: 

1. A viable experimental method using XPS has been shown to conduct a quantitative assessment of migrating 

species in ED-Ni. 

2. This method can be used to evaluate small amounts of segregating species as they accumulate on the free 

surface. 

3. Elements other than Sulfur (such as Cadmium, Tin, and Bromine) were also seen segregating onto the free 

surface. 
ACKNOWLEDGEMENTS 

The authors would like to express appreciation to the SSME Program Office for providing finds for this 

research. Thanks are also due to Mr. Ste\.en J. Gentz for valuable comments, Mr. Steve Hudson for helpful 

discussions, and Mrs. Susan Hessler for technical editing support. 

REFERENCES 

I. 

7 -. 

3. 

4. 

5. 

6. 

Dini, J.W.; Johnson, H.R.; and West, L.A., “On High Temperature Ductility Properties of Electro-Deposited 

Sulfamate Nickel,” Plating and Sirrfacr. Finish, February 1978, p. 36-40. 

Kraai, D.A. and Floreen, S.A., “Hot Ductility of Nickel,” Transactions Metallurgical Societv OfAIME. vol. 230, 

1964, p. 833. 

Walsh, J.M. and Anderson, N.P., “Application of Auger Electron Spectroscopy to the Study of Embrittlement 

in Nickel.” ASTM STP 596, 1976. p. 58 - 67. 

Harris, S.J. and Braddick, D.M., “The Elevated Temperature Tensile Properties of Electro-Deposited Nickel,” 

Transactions iMF, vol. 5 1, 1973, p. 165. 

Safranek, W.H., ed., “The Properties of Electro-Deposited Metals and Alloys,” Handbook, AESF, 1986, p. 26 1. 

Harris, L.A., ”Some Observations of Surface Segregation by Auger Electron Emission,” Joiirnal of Applied 

Phjsics. Vol. 39, February 1968, p.1428 - 1431. 
STATISTICAL ANALYSIS OF STRENGTH DATA 

FOR AN AEROSPACE ALUMINUM ALLOY 

Lynn Neergaard 

IIT Research Institute 

215 Wynn Drive NW, Suite 101 

Huntsville, AL 35805-1926 .. . (256) 382-4773 

and 

Tina Malone 

National Aeronautics and Space Administration 

Building 46 12, Marshall Space Flight Center 

George C. Marshall SDace Flipht Center, AL 358 12 

(256) 544-2593 

ABSTRACT 

Aerospace vehicles are produced in limited quantities that do not always allow development of MILHDBK-5 A-basis design allowables.' One method of examining production and composition variations is to 

perform 1 OOo/b lot acceptance testing for aerospace Aluminum (Al) alloys. This paper discusses statistical trends 

seen in strength data for one AI alloy. A four-step approach reduced the data to residuals, visualized residuals as a 

function of time, grouped data with quantified scatter, and conducted analysis of variance (ANOVA). 

BACKGROUND 

A test article was fabricated to demonstrate full-scale performance of a production-sized alloy ingot, as 

well as to qualify rolling, annealing, and weld approaches. Each panel was subjected to 100% lot acceptance testing 

to verify specification compliance. The test directions were: 

0 

Longitudinal (L) or parallel to the rolling direction 

Long transverse (LT) or perpendicular to the rolling direction in the plane of the plate 

Short transverse (ST) or perpendicular to the rolling direction in the plane of the plate 

45" from the rolling direction in the plane of the plate 

This lot acceptance testing involved multiple tiers of testing and evaluation. Each lot was sampled by 

machining test coupons in the L, LT. and 45" directions. The coupons were then subjected to tensile tests to 

determine ultimate tensile strength (UTS), yield strength (YS), and elongation. Thicker plates were also tested in 

the ST direction. Failed lots were retested twice to confirm the validity of the original test. If possible, failed lots 

were recovered by solution heat treatment. Failure stresses in this plate material followed a severely truncated 

distribution. Plates with nominal values were easily found, but plates with marginal values were rare. 

The first step in quality control is to verify whether the current distribution is acceptable. If not, the process 

used to fabricate the parts is improved to produce material with a tighter distribution of critical properties. Here, the 

distribution appears acceptable and sufficient sampling has been performed to verify the process produces few plates 

with unacceptable properties. The second step is to introduce continual monitoring to ensure the parts remain 

defined by the acceptable distribution. This step is more difficult to implement because the distribution has a sharp 

drop-off after lot acceptance testing. 
Process control techniques normally require the presence of some distance between the upper control limit 

(UCL) and the upper specification limit (USL). The UCL is often the mean plus three sigma, which is a probability 

1 :740 of having an out-of-bounds signal generated by an in-control process. If the process begins to drift. samples 

begin to produce values above the UCL. This development is a signal that the process must be brought under 

control again before an out-of-specification part is produced. However, the UCL is close to the mean in this alloy, 

due to the sharp drop-off ofthe distribution. If the USL is placed near the UCL. only a small probability exists that 

the USL would be exceeded if the current distribution continued. As a result, process malfunctions would probably 

not be caught before unacceptable parts had been produced. 

The alloy specifications included requirements for both strength and toughness. These properties cannot be 

independently controlled. Process operations intended to increase toughness inadvertently decrease strength, while 

increases in strength are generally accompanied by decreases in toughness. What might appear to be two singlesided distributions of bulk strength and toughness is actually a single double-sided distribution of the plate's 

thermomechanical history. The anisotropy of most rolled AI plate results in different properties for different 

directions. Each plate thickness contains a range of microstructures distributed throughout the plate. Intentional 

process variations include different amounts of cold work and heat treatment used for various parts of the tank. 

Gradual process changes may also lead to property or variability changes. 

A statistical analysis was performed on lot acceptance data for an AI alloy intended for use in an aerospace 

vehicle. A-basis design allowables were calculated based on MIL-HDBK-5 procedures. Some property 

distributions were Normal, others Weibull. A lack of process-stable data limits the usefulness of this analysis. 

This paper discusses data taken early in an aerospace project to provide approaches to analyzing lot 

acceptance data for gradual changes in properties. The data constitute 400 lots and 3,300 specimens. 

ANALYSIS 

In Figure 1. UTS and YS are plotted for all samples to demonstrate the correlation of strength with 

processing. OM-temper data fall in the lower left-hand corner, T-3 temper data in the middle, and T-8 temper data 

in the upper right-hand comer. X-Y plots usually show the dependence of one variable (y) on another (x), with YS 

or UTS plotted as a function of intentional process variations. However, these processes are difficult to express as a 

single dimension. Instead of showing cause (x) and effect (y), this plot represents two effects (YS and UTS) of the 

same cause (processing). 

Figure 1. UTS versus YS 
Figure 1 demonstrates the effect of intentional differences in processing. As expected, materials with high 

YS also have high UTS. Deviations from a simple thin line are due to random rather than systematic variation. A 

direct comparison would normalize values for systematic changes in process and geometry by plotting differences 

between UTS and YS and averages for each sample type. Such comparisons might be set up for different values of 

heat treatment, thickness, orientation, etc. The residual is the difference between the expected value based upon all 

input variables and the actual value for a given point.' Intentional variations are extracted to leave the effect of 

unintentional process variations intact. 

Figures 2 through 6 show results of the four-step method used for this study. Figure 2 shows analysis 

results for the first step (reducing the data to residuals) and compares residuals for UTS and YS. This plot would 

look different had all the data fallen at either extreme. One extreme distribution might have been plotted as a thin 

straight line. with all variation due to unintentional process variation. Another might have appeared as a circle 

around the origin, with all variation due to such random effects as inherent material variability or measurement 

error. The correlation coefficient is used to quantify the degree of variation and randomness. Here, the correlation 

coefficient squared of the data group is 80%. This result indicates that 80% of the property variation is due to 

variations in process and IO0/& is caused by random effects. 

Figure 2. UTS versus YS residuals 
Figure 3 shows analysis results for the second step (visualizing residuals as a function of time) with UTS 

residuals plotted by test date. Time is used as a proxy for process improvements based on the assumption that the 

processes continuously changed. Such process improvements might include a new heat treat control philosophy, 

composition retargeting, rolling practices, etc. The data do not show any obvious drift toward progressively higher 

UTS or a narrowing of the data envelope, which would indicate better process control. Residuals are considered a 

good metric for process control, with large values indicating significant process variations. 

~.. ... " . ....,.... 2.. .... . . .. . . ... ..... .. . .. - l.".^___l 

5- 

-7 . 

Year 

Figure 3. UTS residuals versus time 
Figure 4 shows analysis results for the second and third steps (grouping data and quantifying scatter). 

Twelve data groups may develop when residuals are divided into subgroups to facilitate measurements of data 

scatter and mean. These boundaries reflect natural divisions between testing efforts and keep the size of each group 

within one order of magnitude of the other groups. Unlike the UTS data, the elongation data show a gradual 

narrowing of the data envelope. 

,. .. . .. . . . . . .. ., ._i .tj . . . . . .. . . . .,.*. . . I 

Figure 4. Elongation residuals versus time 

Figures 5 through 6 show other analysis results for the third step. Here, Figure 5 shows the size of the 

groups generated. All data groups fall between 60 and 600 points, except for the two groups at the ends. 

1 

* 

+ 

Figure 5. Number of points versus time 
Figure 6 includes lines that represent averages for each group. These data do not indicate a trend with time. 

The error bars indicate plus and minus one variance (i.e., one standard deviation squared) while short horizontal 

lines show maxima and minima for data groups. Neither variance nor range shows any systematic narrowing with 

time, although they show significant differences from group to group. High variance occurs together for YS and 

UTS, primarily due to process variations. 

- 1 -6 

- 

Year 1 Year 2 Year 3 Year 4 

vest 1 Ymr 3 

(b) UTS 

Figure 6. Summary of Variance for Three Properties 
-5 - 

I Year 2 

-1 0 ____- ___ _____ 

Year 1 Year 2 Year 3 Year 4 

7 16 I 72 * IS I2 

I 6 I 92 

(c) Elongation 

l Year 3 

Figure 6. Summary of Variance for Three Properties (continued) 

7 I 12 I 5 I 40 I 98 

I1 59 5 40 140 

Process variations are considered the primary source of property variability. No clear patterns emerge 

when raw residuals are examined as a function of time or when discrete groups of data are analyzed separately. 

Data variation is quantified as a function of input variables when ANOVA3 is used to track process control for sets 

of acceptance data. However, this technique presents an inherent problem. A well-designed ANOVA experiment 

should have the same number of data points for each combination of input variables. If the data points are not 

evenly distributed, the input variables are considered to be convoluted. For example, Table 2 shows convolution 

when a number of data points are compared as a function of heat treatment and time. 

Year 4 

Table 2 - Number of Samples Tested 

(Heat Treatment versus Time) 

I 15 

Note: Two tempers were applied to the material. the first after it was rolled and the second after it was slightly stretched. 

“OM” is a temper desibmation which means that the material was not heat treated during this step. 
Several blanks appear in the matrix. However, many spaces can be eliminated by culling the data. Table 3 

shows a new matrix that should produce better ANOVA results, although the refined data are still convoluted. 

Vanable I NumberofLeLels I UTS ("01 

Table 3 - Refined Data 

(Heat Treatments versus Time) 

YS Po) Elongation ("0) 

Note Two tempers were applied to the material. the first after it was rolled and the second after it was slightly stretched 

"OM" is a temper designation which means that the material was not heat treated dunng this step. 

Tune 

Direction 

Heat Treatment 

Error 

Gage 

Table 4 shows ANOVA results for the refined data, which involve four different gage thicknesses. Two 

thin gages were heat treated under one set of conditions while two thick gages were heat treated under another set of 

conditions. Such differences indicate that the data will be convoluted for plate thickness and heat treat variables. 

This situation was addressed by combining the thinnest gages into one group for a given set of heat treatments. 

IO 3 3 5 

- 2 - 2 

J 17 19 32 

5 78 76 61 

0 0 0 

7 7 

These results are not as precise as they would be for well-conditioned data resulting from a designed 

experiment. However. the ANOVA suggests that anisotropy and heat treatment control over 90% of the data 

variability studied. Small but significant contributions also come from gage thickness and time. Together, these 

four variables account for most of the variability seen in this particular A1 alloy. 

CONCLUSIONS 

1. This study considered a large set of lot acceptance data for an aerospace AI alloy. However, the final ANOVA 

results are not entirely accurate because the original data inputs were convoluted. 

Over 90% of the data variability can be attributed to the effects of anisotropy and heat treatment. 

Process variation did not systematically increase or decrease during this period of time. 

3. 

3. 
REFERENCES 

1. U.S. Department of Defense, Information Handling Services. Militarj? Handbook 5H: Metallic Materials and 

ElemetztsUfor- Aerospace i’ehicle Structirres. Document MIL-HDBK-5H (December 1, 1998): 9- 18 - 9-64. 

2. Montgomery, Douglas C. Desigtt and Atia!isis ofExperinients. (NY: John Wiley & Sons, 1991): 465. 

3. Miller, Irwin; Freund. John E.; and Johnson, Richard A. Probabilip and Statistics for Engineers. (Englewood 

Cliffs, NJ: Prentice Hall, 1990): 376 -413. 
Electrostatic Levitation Processing of Bulk Metallic Glass Forming Liquids (2 

C. C. HAYS, J. Schroers, U. Geyer, W. L. Johnson 

Division of Engineering & Applied Science, 138-78 

California Institute of Technology 

Pasadena, CA 9 1 125 USA 

E-mail{chavsCa).hvDerfine.caltech.edu I 

Bulk metallic glass forming alloys are a novel group of multicomponent metallic alloys that 

exhibit exceptionally high resistance to crystallization in the undercooled liquid state. Compared 

with the rapidly quenched metallic glasses studied prior to 1990, these alloys can be vitrified at 

cooling rates < 10 Wsec. With critical cooling rates this low, standard processing methods can be 

employed. This point, together with their high mechanical strengths, shows that bulk metallic glasses 

are a promising material system for application as an engineering material. Considerable success has 

recently been achieved in toughening bulk metallic glasses using in situ formed ductile phase dendrites in a bulk metallic glass matrix [ I]. Processing of these composites involves interfacial reactions and atomic transport in the molten state; thus, knowledge of atomic diffusion constants is 

critical in this work, as it directly impacts the evolution of the microstructure during processing. 

Electrostatic levitation (ESL) processing provides an excellent means for examining the 

thermophysical properties of an undercooled liquid metal system. The advantages of this method are 

ideal for the study of liquid state properties of bulk metallic glass forming liquids. In this talk, we 

will discuss results obtained from recent ESL experiments conducted at the Marshall Space Flight 

Center ESL facility. We will review some of the experimental details required to use the ESL method 

as a platform for the determination of difhsion coefficients in the high temperature liquid and 

undercooled liquid regimes of a bulk metallic glass forming liquid, the latter topic being the experimental goal of our proposed NASA flight experiment. The determination of atomic diflusion constants is critical to understanding the processing and control of the dendritic structures in the in situ 

formed composites. Recently, we used the ESL to examine the bulk metallic glass forming ability in 

the Zr-Nb-Cu-Ni-A1 alloy system. We have identified a composition that exhibits a substantially 

improved glass forming ability in comparison to neighboring compositions: 

Zr58.5Nb2.8Cu 15.6Ni 123Al10.3. This alloy is easily vitrified by standard techniques, e.g., arc 

melting and melting on a water-cooled silver boat apparatus. When examined in the ESL, the alloy is 

vitrified by purely radiative cooling. This is the first non-Be containing alloy to be vitrified on free 

cooling in the ESL. This places the critical cooling rate for this composition <7 Wsec. The TTT 

diagram for this alloy has been determined and exhibits a single c-shaped branch and a nose time 

centered at -20 seconds. Microstructural properties of the ESL processed materials were examined 

by x-ray diffraction, electron- and optical-microscopy, and thermal analysis methods. These results 

are used to interpret the complex evolution of glass forming properties observed in this alloy system 

[2]. As an excellent example of technology transfer, we will discuss use of this new bulk metallic 

glass as a solar wind collector in the NASA sponsored Genesis Mission, scheduled for launch in 

February 200 1 (Prof. Don Burnett, California Institute of Technology, Principal Investigator). 

11). C'. C'. Hays. c'. P. Kini. and \+, I.. Johnson. Phys. Kc\. Lctt. 84, 2901 (2000). 

[21, C'. <', Hap. J. Schrocrs. U. Gqcr, and W. L. Johnsoii (tu bc submittcd to Appl. Phys. Lctt.). 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfcmsa. gov 
"Residual Stress Prediction in Machined 

Abstract 

The increasing drive for productivity improvements and 

consistent part dimensionality in aerospace structures has lead 

to the advent of machined monolithic parts. High speed 

machining technology employed affords the manufacture of 

thin-walled parts from single billets of material, resulting in 

the removal of approximately 8590 of the initial workpiece 

material. With thin-walled monolithic parts come the 

increased propensity for workpiece distortion and few 

arresting mechanisms for crack propagation, largely due to 

potentially unfavorable residual stress states. These imposed 

states of stress can be a result of the machining conditions 

used (e.g., feeds, speeds and cutter geometry). A general 

method is presented to model the residual stress state induced 

by metal cutting operations which takes into account 

workpiece thermo-mechanical properties, cutter geometry and 

process parameters. In this paper the model is specifically 

applied to A17050. Results indicate the magnitude and sign of 

the state of stress is shown to have no intuitive correlation to 

machining process parameters such as speed and chip load. 

Similar results are shown for stress-induced bending moments, 

a potential strong contributor to part distortion. In addition, 

the machining-affected layer is shown to be on the order of 

lmm, easily on the same length scale as the wall thickness of 

aerospace structures. 

i-3 /,Jr 

Workpiece Surfaces'' 

Marusich, T. D. 

Third Wave Systems, Inc 

the tool. This method precludes the resolution of the cutting 

edge radius and accurate resolution of the secondary shear 

zone due to severe mesh distortion. To alleviate element 

distortions, others used adaptive remeshing techniques to 

resolve the cutting edge radius Gehkon andchenot, 1993; and 

Marusich and Ortiz, 1995; Marusich, 2000). Eulerian 

approaches, tracking volumes rather than materialparticles, 

did not have the burden of rezoning distorted meshes 

( Strenkowski and Athavale. 1997). However, steady state freesurface tracking algorithms were necessary and relied on 

assumptions such as uniform chip thickness, precluding the 

modeling of milling processes or segmented chilformation . 

In this paper, a Lagrangian finite element-based machining 

model is applied to orthogonal cutting of A17050. Techniques 

such as adaptive remeshing, explicit dynamics and tightly 

couple transient thermal analysis are integrated to model the 

complex interactions of a cutting tool and workpiece. 

Introduction 

In order to improve metal cutting processes, i.e. lower part 

cost, it is necessary to model metal cutting processes at a 

system level @hmann el. al., 1997). A necessary requirement 

of such is the ability to model interactions at the tool chip 

interface and thus, predict cutter performance. Many 

approaches such as empirical, mechanistic, analytical and 

numerical have been proposed. Some level of testing for 

model development, either material, machining, or bothis 

required for all. However, the ability to model cutting tool 

performance with a minimum amount of testing is of great 

value, reducing costly process and tooling iterations. In this 

paper, a validated finite element-based machining model is 

presented and employed to determine the effects of cutting 

process parameters such as speed and chip load on the induced 

state of residual stress. 

Figure 1 Schematic of orthogonal cutting conditions 

Typical approaches for numerical modeling of metal cutting 

are Lagrangian and Eulerian techniques. Lagrangian 

techniques, the tracking of discrete material points, has been 

applied to metal cutting for over a decade Gtrenkowski and 

Carroll, 1985; Komvopoulos and Erpenbeck, I99 1 ; Sehkon 

and Chenot, 1993; Obikawa and Usui, 1996; and Obikawa et. 

al.. 1997.). Techniques typically used a predetermined line of 

separation at the tool tip, propagating a fictitious crack ahead Figure 2 Initial tool indentation 

1 
I 

interaction, and transient thermal analysis. For example, in the 

vicinity of the cutting edge radius the workpiece material is 

allowed to flow around the edge radius. The initial mesh, Fig. 

5, becomes distorted after a certain length of cut, Fig. 6, and is 

remeshed in this vicinity to form a regular mesh again, Fig. 7. 

For a comprehensive discussion on the numerical techniques 

the reader is referred to Marusich and Ortiz ( 1995) and to 

Marusich (2000) for validation examples. 

Figure 3 Chip formation 

[ -- 

Figure 5. Initial mesh magnified 

in the cutting tool edge vicinity. 

Figure 4 Fully developed continuous chip 

Machining Simulation System 

Simulations were performed with Third Wave Systems 

AdvantEdge machining simulation software, which integrates 

advanced finite element numerics and material modeling 

appropriate for machining. The orthogonal cutting system is 

described in Fig. I where the observer is in the frame of 

reference of the cutting tool with the workpiece moving with 

velocity v. The cutting tool is parameterized by rake and 

clearance angles, and a cutting edge radius, but can also 

accommodate general chip breaker geometries. In the plane 

strain case the depth of cut into the plane is considered to be 

large in comparison to the feed. The cutting tool initially 

indents the workpiecz Fig. 2, the chip begins to form Fig. 3, 

and finally curls over hitting the workpiece ahead of the cut, 

Fig. 4. 

Figure 6 Deformed mesh. 

Modeling Approach 

AdvangEdge. Third Wave Systems (2000, is an explicit 

dynamic, thermo-mechanically coupled finite element model 

specialized for metal cutting. Features necessary to model 

metal cutting accurately include adaptive remeshing 

capabilities for resolution of multiple length scales such as 

cutting edge radius, secondary shear zone and chip load; 

multiple body deformable contact for tool-workpiece 

2 
Figure 7. Updated mesh. 

HwJ%e 

Chip 

Load 

Case per 

Tooth 

(mrn) 

1 0.2 

Due to the transient thermal and dynamic behavior of the 

model it is necessary to thermo-mechanically relax the 

workpiece after the cutting process to accurately model the 

state of residual stress. The milling operation modeled is 

idealized by a single cutting tooth in a plane strain, orthogonal 

cutting, mode with a constant chip load, typically set to be the 

maximum in the cut. 

Cutting 

Speed ToolGeometry 

(mlmin) 

275 12" rake 

Material Modeling 

In order to model chip formation, constitutive modeling for 

metal cutting requires determination of material properties at 

high strain rates, large strains, and short heating times and is 

quintessential for prediction of segmented chips due to shearlocalization (Sandstrom and Hodowany 1998; Childs, 1998 ). 

Specific details of the constitutive model used are outlined in 

Marusich and Ortiz (1 995). The model contains deformation 

hardening thermal softening and rate sensitivity tightly 

coupled with a transient heat conduction analysis appropriate 

for fmite deformations. 

2 

3 

4 

Results 

Residual stress predictions were made for several cutting 

conditions, varying speed, chip load and radial rake angle, 

Table 1. The normalized residual stress is plotted as a 

function of depth from the workpiece surface, Fig. 8. While 

no clear trend with process parameters is evident, two distinct 

residual stress signatures appear. Singling out three cutting 

conditions and comparing with the baseline conditions the two 

distinct stress signatures are apparent, Fig 9. A resulting 

bending moment per unit length can be computed from the 

stresses and plotted as a function of speed and chip load for 

the four cases, Fig. IO. Finally, the normalized moment is 

plotted as a function of tangential cutting force for all the 

cutting conditions, Fig. 1 1. 

0.4 138 12" rake 

0.4 275 12" rake 

0.2 275 25" rake 

5 

6 

7 

550 12" rake, 50mm dia. 

550 12" rake, 50mm dia. 

0.2 

0.4 

0.2 138 12" rake 

8 

9 

0.3 275 12" rake 

0.3 138 12" rake I I I 

10 I 0.1 1 275 I 12" rake 

x 

X 

I 

f 1 

2 

Figure 8 Residual stress profiles into workpiece 

surface for 10 different cutting conditions 

3 
Figure 9. Select cutting conditions tested with substantially 

different residual stress signatures 

Figure 10. Normalized bending moment as a function of 

cutting speed and chip load for select cutting conditions. 

i i 

Figure 11. Normalized bending moment as a function of 

tangential cutting force for 10 different cutting conditions. 

Discussion 

The residual stress profiles for the entire test matrix are plotted 

as a function of depth into the workpiece, Fig. 8. The profiles 

typically decay to zero around 0.5mm beneath the workpiece 

surface, varying from positive to negative in order to satisfy 

equilibrium. Since thin walled aerospace parts can be on the 

order of a couple of millimeters in thickness, the machinedaffected zone can be significant. When looking for correlation 

with process parameters, residual stress profiles were analyzed 

over a range of chip loads, cutting speeds and a pair of rake 

angles and exhibited no clear trends. Stress profiles in this 

parameter space appear to be most influenced by the chip load 

rather than speed or rake angle. The bending moments 

computed for these cases show a change in sign, i.e. an 

opposite tendency for bending. when the chip load is increased 

from 0. lmm to 0.3mm per tooth, Fig. 10. However, when the 

entire test matrix is plotted against tangential cutting force 

there appears to be either no trend or a bifurcation point, Fig 

11. 

Conclusion 

A general method is presented to model the residual stress 

state induced by metal cutting operations which takes into 

account workpiece thermo-mechanical properties. cutter 

geometry and process parameters. In this paper the model is 

specifically applied to A17050. Results indicate the magnitude 

and sign of the state of stress is shown to have no intuitive 

correlation to machining process parameters such as speed and 

chip load. Similar results are shown for stress-induced 

bending moments, a potential strong contributor to part 

distortion. In addition, the machining-affected layer is shown 

to be on the order of Imm, easily on the same length scale as 

the wall thickness of aerospace structures. 

4 
References 

Childs, T. H. C., “Material Property Needs inModelling Metal 

Machining,” CIRP Workshop on Modeling Metal Cutting , 

( 1998). 

Flom, D. G., “High-speed Machining,” inBruggeman and 

Weiss (eds.) 

Innovations in Materials Processing, Plenum Press, ( 1983) 

4 17439. 

Kobayashi, S.,Herzog, R. P., Eggleston, D. M. andThomsen, 

E. G., “A Critical Comparsion of Metal-Cutting Theories with 

New Experimental Data”, Trans. ASME J. Eng. Ind. (1960), 

333-347. 

Marusich, T. D. and Ortiz, M., “Modeling and Simulation of 

High-speed Machining”, 

Int. J. Num. Metk Eng38 ( 1995), 3675-94. 

Marusich, T. D.. “Effects of Friction and Cutting Speed on 

Cutting Force”, Submitted to ASME 

Journal of Manufacturing Science and Engineering (2000). 

Sandstrom, D. R. and Hodowany, J. N., “Modeling the 

Physics of Metal Cutting in High-speed Machining,” 

Machining Science and Technology2 (1 998), 343-353. 

Stevenson, R. and Stephenson, D. A., “The Mechanical 

Behavior of Zinc During Machining,” Journal of Engineering 

Materials and TechnologyJ77 ( 1995). 172-178. 

Strenkowski, J. S. and Athavale, S. M., “A Partially 

Constrained Eulerian Orthogonal Cutting Model for Chip 

Control Tools,” Journal of Manufacturing Science, 11 9 

( 1997), 68 1-688. 

Third Wave Systems, Inc. 2000 YdvantEdge v3.3 Machining 

Simulation Software”, Minneapolis, MN 

Obikawa, T. and Usui, E., “Computational Machining of 

Titanium Alloy-Finite Element Modeling and a Few Results,” 

Journal of Manufacturing Science and Engineering, 118 

( 1996). 

Obikawa, T., Sasahara, H., Shirakashi, T. and Usui, E. 

“‘Application of Computational Machining Method to 

Discontinuous Chip Formation,” Journal of Manufacturing 

Science and EngineeringJ 19 (1997), 667-674. 

Contact 

Troy D. Marusich 

Trovmbt1iirdwaves~s.com 

7301 Ohms Lane Suite 580 

Minneapolis, MN 55439 

www . thirdwavesys. coin 

5 
- 

EASILY PROCESSABLE HIGH TEMPERATURE AND FLAME RESISTANT 

PHTHALONlTRlLE COMPOSITES FOR AEROSPACE APPLlCATlONS 

Teddy M. Keller 

Ad\ anced Materials Section, Code 6 I27 

Chemistry Division 

Tel: 202-767-3095 

&'N a 

F-M~~I] I\c!lc: I ,wcc<rit I i~i\ \ nii; I 

Harry N. Jones 

Materials Characterization Section. Code 6325 

Materials Science and Technology Division 

Tel: 202-767-1278 

E-Mail{ iones@anvil.nrl.navv.mil I 

Naval Research Laboratory 

Washington. DC 20375-5320 

INTRODUCTION 

The aerospace industry is utilizing structural composites in airframes and skins to reduce weight and to 

improve fuel efficiency (1). With an increase in future composite usage. materials with low flammability and high 

strength will be needed to maintain airframe loads in the next generation, reusable, and expendable aeronautical and 

space vehicle systems. Polymer-based materials are currently being used in non-structural and semi-structural 

applications in cabin interiors. The materials are fairly flammable and/or generate copious amounts ofsmoke in a fire 

scenario and do not meet the FAA goal ofgenerating survivable aircraft cabin conditions for 15 minutes in post-crash 

fuel fire. Fiber-reinforced composites utilizing high temperature polymers are more resistant to ignition but can suffer 

from poor processing characteristics and mechanical properties. Increased usage of polymers and composites by the 

aerospace industry will demand materials with better tire performance, structural integrity, and ease of processability. 

Phthalonitrile-based composites under development at the NRL show excellent flame resistant properties and 

thermo-oxidative stability (2) approaching 375 "C. The phthalonitrile cure reaction is not accompanied by evolution of 

volatile by-products. Therefore. void-free components can be made easily from this resin system. The advantages and 

versatility ofthe phthalonitrile polymer may be realized in terms of ease of processing and superior properties. The 

phthalonitrile monomer can be cured into a thermoset resin using a wide variety ofcuring additives (2-5). Additionally, 

a prepolymer (B-staged resin) or prepolymerization composition may be prepared and stored for later usage with an 

indefinite shelflife under ambient conditions. The polymerization rate is also easily controllableas a function of curing 

additive and processing temperature for thick section composite fabrication. With regard to the thermal properties. the 

fully cured resins do not show a glass transitiontemperature up to 450°C and exhibit good mechanicalproperty retention 

at elevated temperatures. The current state-of-the-art high temperature resin based on PMR polyimide, designated as 

PMR- IS, shows promise up to 3 I6 "C but is accompanied by processing problems such as volatiles from residual 

solvent and a short processing or reaction time (6,7). The short reaction time translates to inadequate resin flow for 

fabricating thick and complicated composite structures. In light of these drawbacks with existing resin systems, 

phthalonitrile matrices show promise and may help further the usage of polymeric composites in applications that need 

high temperature and flame resistant capabilities. 

Phthalonitril e Monomer 

Phthalonitrile monomer, [4,4'-Bis (3,4-dicyanophenoxy)biphenyl], has been commercialized by Eikos. Inc. 

and is being used as a matrix resin for composite formulations. Composite panels have been processed by conventional 

prepreg consolidation and by resin infusion and filament winding methods using carbon tape (R), carbon fabric (9) and 

glass fabric ( IO) as reinforcements. Since the initial resin melt viscosity is low ( 100-200 cp) and can be controlled by 
the proper selection of curing additive and curing temperature. the phthalonitrile composites are amenable to processing 

by more cost effective methods such as resin transfer molding and resin infusion molding. Mechanical properties and 

thermal and oxidative stability of phthalonitrile-based composites are superior to that of many state-of-the-art high 

temperature composites. With regard to fire performance, phthalonitrile composites excel over other polymeric 

composites. The phthalonitrile composites are the only materials that meet the Navy's stringent requirements of MILSTD-203 1 ( 1 1) for use of polymeric composites aboard Navy submarines. The specification contains test methods and 

requirements for flammability characteristics such as flame spread index, specific optical density, heat release, time to 

ignition, oxygen-temperature index, combustion gas generation, etc. A large fraction of our current efforts at NRL are 

targeted toward the optimization of curing parameters, property determination, and working with industry and other 

research organizations to further develop these new composite niaterials for marine and aerospace applications. 

PROCESS ABILITY 

Most of our composite efforts have involved using aromatic diamines with ether linkages connecting the 

terminal aromatic amine moieties as curing additives. The amount of aromatic amine that can be used to form a 

prepolymer is limited due to the reactivity of the amine toward the phthalonitrile monomer. A prepolymer is defined 

as a low molecular weight B-staged polymeric composition. which is formed from reaction of the amine with the melt 

of the monomer. Upon cooling. the B-staged prepolymer is a frangible solid, which can be pulverized into a powder. 

In contrast to prepolymers from other resin systems. the phthalonitrile prepolymer can be stored indefinitely at room 

temperature. In the fabrication of thick composite components from either a prepreg, by resin infusion molding, or by 

resin transfer molding (RTM), processing difficulties may arise if the polymerization proceeds too rapidly. This is not 

a problem in the phthalonitrile systems due to the low cure exotherm. 

An improved, more cost effktive processingmethod. which involves a prepolymerizationcomposition formed 

from mixing various amounts of phthalonitrile monomer and aromatic amine curing additive at room temperature, is 

under development at the NRL. Upon melting. the polymerization rate dependson the composition of the mixture and 

melt temperature. These phthalonitrileicuring additive prepolymerization compositions are especially usefd for 

fabrication of'composite cmponents by resin transfer molding (RTM), filament winding, injection molding, or prepreg 

formulation from the melt in the absence of sbivent. The composition is completely stable under ambient conditions 

before melting occurs. Any amine curing additive that is stable and shows non-volatility at the processing or 

polymerization temperatures can be used to polymerize phthalonitrile monomers. The prepolymerization composition 

is heated until complete melting occurs, which depends on the melting point of the phthalonitrilemononier. In the melt 

stage, the curing additive reacts with the phthalonitrile monomer. The viscosity of the resulting B-staged prepolymer 

at a given temperature and time depends on the amount and reactivity of curing additive in the composition. The 

composition can be used upon melting (B-stage) in the fabrication of composite components. 

mi x Phthalonitrile Monomer + Curing Additive Preppolymerization Composition 

Rheometric studies on phthalonitrile prepolymers with the same molar concentrations of 1,3-bis (3- 

aminophenoxy)benzene ( APB) and bis[4-( 4-aminophenoxyphenyl) phenyl] sulfone (BAPS) as curing agents were 

conducted to monitor the viscosity changes accompanying the cure reaction. Figure 1 shows the melt viscosity as a 

function of reaction time at 260 "C. The initial melt viscosity is low and range between 50-300 cp. From the plots, it 

is evident that the melt viscosity of prepolymers containing APB increase at a faster rate than the BAPS-containing 

compositions. Differential scanning calorimetry (DSC) analyses show that both curing additives react readily with the 

monomer between 250-260°C. The difference in the reactivity of APB and BAPS toward the phthalonitrile monomer 

is attributed to the differences in the basicity of the two amines. The basicity of the BAPS is lower due to the presence 

of the electron withdrawing sulfone group when compared to APB that has an electron donating phenoxy group. Based 

on this study, cure of the phthalonitrile monomer with BAPS may be advantageous to slow down the polymerization 

and thus broaden the processing window. Previous cure studies with APB (8) have indicated that the melt viscosity is 

very sensitiveto small changes in the diamine concentrationused to make the prepolymer. The preferredamount of APB 

for composite component fabrication is 1.5-2.3 weight percent. When larger amounts are used, the viscosity of the 

prepolymer advances too rapidly to consolidate a quality composite panel or component. Given the lower reactivity and 

a higher molecular mass of BAPS, the amine concentration range for prepolymer formulations can be broadened to 2-4 

weight percent. 
COMPOSITE FABRICATION 

so - 

40 - 

Phthalonitrile composite panels have been fabricated by consolidation ofprepreg (undirectional carbon, woven 

glass and carbon) and by resin infusion molding (woven glass and carbon) techniques for testing in a research size 

llnited McGill Corporation autoclave at the National 

Figure 1. Viscosity vs.Time Plots for Phthalonitrile 

Cure with Two Different Amines at 260'C 

~ 88 p-BAPS I 

. 

. 

. 

. 

. 88 

. Q: 

I 10 I b 

0 

0 10 20 30 40 

Time (min.) 

Institute of Standard and Technology (NIST). The resin infusion process is similar to the prepregging process in that 

the resin flows over the surface of dry fibers. Resin infusion may be viewed as similar to the cure and consolidation 

process since the viscosity of the resin changes with time and temperature due to the cure process. In this process, the 

melt viscosity. which controls the resin flow, is of paramount importance. Resin infusion simplifies the composite 

manufacturing process where impregnationand consolidation arecombined in a single step. In this process, unlike with 

prepregs, each ply is made up of dry fibers and the matrix resin is placed at the top or bottom. A mold is formed from 

sealant tape and bagging materials and the matrix resin may be in the form of a film, powder, pellet or viscous liquid. 

This processing technique is particularly attractive for resins that can realize very low viscosity values. Regardless of 

the technique used to fabricate the phthalonitrilepanels, consolidationis accomplished by heating for 1 h at 250 "C and 

3h at 325 "C under 200 psi pressure (1.3 MPa). The panels were postcured up to 375 "C to improve the physical 

properties. An alternate curecycle involves heating for 1 hat 250 "C, for 2h at 325 "C, and for 1-4 h at 375 "C under 

100 psi pressure ( 1.3 MPa). Heating and cooling rates are at 4 "C/min and high vacuum is applied at the start of the 

cycle. After a dwell at 250 "C for 0-60 min., pressure is applied, which is completed within 1/2h, followed by the 

cessation of vacuum. 

The glass transition temperature (T,) of the panels is estimated from the modulus vs. temperature plots 

obtained by dynamic mechanical analysis (DMA). A carbon reinforced panel that had been fabricatedfrom a prepreg and 

cured for 1 h at 250 "C and 3h at 325 "C exhibited a glass transition temperature in excess of 350 "C and maintained 

75% of the initial modulus at 400 "C. With an additional postcure for 2h at 350 "C, the T, is shifted to temperatures 

above 400 "C. Specimens that are postcured at 375 "C for 2,4 and 6h do not exhibit a T, in the measurement range 

(1450 "C) and appear to retain about 73,75 and 8396, respectively, of their storage modulus at 450 "C. With an even 

longer postcure cycle of 8h each at 350 and 375 "C, approximately90% of the room temperaturemodulus is maintained 

at 450 "C. 
Values Measured for A Panel 

Property 

Q Tension 

Modulus, GPa (*%) 

Strength, MPa (&) 

Strain. % (i%j 

90 Tension 

Strength, MPa (*%) 

Modulus. GPa (*%) 

Strain, Yo (5%) 

0 Flexure 

Strength. MPa (*YO) 

Modulus. GPa (*%j 

Strain, "4 (&(Yo) 

90 Fle xure 

Strength, MPa (PY) 

Modulus, GPa (*%I 

Strain. YO (*%) 

Short Beam Shear 

Strength, MPa (*%) ~ ~~~~ ~ 

MECHANICAL PROPERTIES 

Made from Different Batch of Prepreg) 

Phthalonitrile/lM7 PMR-I5/'lM7 

2000 [2400)' (1) 2500 (7) 

183 [I621 (2) 146 (3) 

1 .h (4) 

41 (IO) 29 (7) 

10 (8) 9 (3) 

0.4 (12) 0.5 (30) 

1 .O [I .36]* (7) 

2350 (2) I530 (5) 

1.3 (18) 1.3 (6) 

174 (2) 122 (4) 

80 ( 1.3) 

11 (9) 

0.6 (4) 

85 (2) 105 (2) 

Composite mechanical properties, in general, are governed by many factors including processing parameters 

(time, temperature and pressure). type of fibers and fiber orientation. prepreg quality, post-curing environment (e.g.. air 

or nitrogen), specimen size and configuration, and composite composition (fiber, resin and void content). Data on the 

mechanical properties of carbon-basedphthalonitrile (8) and PMR- 15 composites ( 12) are summized in Table I. These 

results reveal that some of the mechanical properties of phthalonitrile-based composites are superior while others are 

comparable to PMR- 15. For instance, the flexural strength of the phthalonitrile composite is substantially higher than 

that for the PMR- I5 analog (2350 MPa vs. I530 MPa). Similarly, the transverse tensile strength of the phthalonitrile 

composite is 4 1 MPa, which is higher than the corresponding PMR- 15 composite value by about 40%. Although the 

measured longitudinal tensile strength for the phthalonitrilesystem is low (2010 MPa), panels fabricated from a different 

batch of prepreg and processed by a differentmethod yield a strength value (2400 MPa) comparable to that of the PMR15 composite (2500 MPa). This improvement suggests that there is additional room for property improvement with 

optimization of the prepregging and consolidation processes. The measured tensile and flexural modulii of the 

phthalonitrile composite are also superior to those of the PMR- 15 composite. However, the short beam shear strength 

of the phthalonitrile composite is slightly lower than that of the PMR- 15 system. This test is particularly sensitive to 

relative sample and fixture dimensions and specimen surface preparation. 

WATER ABSORPTION AND FLAMMABILITY CHARACTERIZATION 

To be considered for advanced aerospace(aircraft and space vehicle) applications, a polymeric compositeshould 

have low water absorption and outstanding flame resistant properties. Phthalonitrile based glass and carbon reinforced 

composites exhibit water uptake level <I% after immersion in water for over 30 months. Tables 2 and 3 present heat 

release and ignitable data ofphthalonitrile/glass and phthalonitrileicarboncomposites. Pertinent data for other state-ofthe-art polymeric composites and the Navy specification MIL-STD-203 1 are also presented in these tables for 

comparison. Heat release is defined as the heat generated in a fire due to various chemical reactions occumng within a 

given weight or volume of the material. This characteristic provides a relative fire hazard assessmentin that the material 

with low heat release rate per unit weight or volume will do less damage to the surroundings than the one with a high 
heat release rate. It has been suggested that the heat release rate of a material measured in a small scale test under 

simulated radiant exposure conditions is the single most important parameter in characterizing the hazardous nature of 

a material in a fire ( 13). The peak heat release (PHR) and time to ignition (T,&), which serve as a measure of resistance 

ofa material to participate in fire, are very impressive for carbon and glass reinforced phthalonitrile composites. 

G1:'Epoxy 535 

GliBismaleimide 503 

Glli'Phenolic NI 

GliPolyimide NI 

For usage oforganic polymeric composites,inside of a submarine, Navy specificatim MIL-STD-203 I requires 

a maximum peak $eat release (PHR) of 150 kW/m- and a minimum time to ignition (Tlg) of 60 sec. at a radiant heat 

flux of 100 kWini-. When compared with other high temperature, high performance composites, cone calorimetric 

studies have shown that a phthalonitrile carbon composite (8) is the only polymeric material that satisfies the Navy's 

flame retardant specifica,tion (PHR and Tip) for using lightweight, polymeric composites for submarine applications 

(Table 3). At 100 kW/m- irradiance heat treatment, phthalonitrile carbon composites meet the requirement and exhibit 

PHR and T,, values of 1 18 and 75. respectively. This is an important finding given the fact that high performance 

composites that meet the Navy's flammability specification have not been available. Preliminary cone calorimetric data 

has also been obtained on a phthalonitrile glass composite panel (9) containing a fiber volume fraction of54. The PHR 

and T,, values are 106 and 59. respectively (Table 2). This study will be repeated on a panel containing a higher volume 

fraction of fiber. 

105 60 40 39 178 217 232 

141 60 38 128 176 245 ,785 

214 57 25 N1 47 97 133 

175 75 55 NI 40 78 85 

Composite 

CarbodPhthalonitrile 

CarbonlPMR- 15 

Carbon/BMI 

CarbonPEEK 

The superior flame resistance of the phthalonitrile/carbon composite also meets the FAA requirement (no 

tlammability at 35 kW/m' irradiance) for composite usage in an aircraft cabin. The flammability parametersderived from 

micro-scale calorimetric measurements (14)are the char yield at 650"C, the peak rate of heat release, and the total heat 

release at 900°C. The peak heat releaserate is originally measured in Wig but is subsequently normalized by dividing 

with the heating rate to obtain the heat release with units of Jig-K. The total heat release in KJig is obtained from a 

numerical integration of the heat release rate curve and the char yield from the residual mass after the test. The char yield 

and total heat release of the phthalonitrile polymer are 87% and 2.1 kJ/g, respectively. The char yield and the total heat 

release values for the phthalonitrile polymers are far superior to those of other polymers such as polyimide (kapton), 

polybenzimidazole (PBI ), phenolic triazine (PT-30). etc ( 15). 

Time to Ignition (see.) Peak Heat Release (kU'/m2) 

75 118 

55 85 

LL 37270 

42 85 

Table 3. Flammability Results for Carbon Fiber-Reinforced Composites I 
CarbodEpox y 

Carbom'Phenolic 

While the maximum temperature limit at which polymer matrix composites are normally considered for use 

is around 3 16-375 "C (600-700 OF), there are many applications such as missile structures, where the temperatures 

encountered are much higher but exist for only a few minutes. An example of this situation is found in some 

components of medium range tactical missiles, which may experience maximum surface temperaturesfrom aerodynamic 

heating of from 399-538 "c (750- 1000 OF) for a period oftime approaching70 sec (1 6). High temperaturetensile testing 

was performed on 8 ply unidirectionalIM7 carbon reinforcedphthalonitrilecomposite specimensup to 593 "C ( 1 100°F) 

at a heating rate of 28 "C/min. The phthalonitrile composite did not start to lose its tensile strength until temperatures 

of 538 "C (1000 OF) were approached. The sample exhibited a 6-7% weight loss at this temperature, which translated 

into about 0.004 gm/cm2 of a real weight loss resulting in a resin loss penetration depth into the composite surface of 

0.08 mm. If we assumed the loss of resin on the surface is equivalent to the loss of load carrying of the fibers within 

the penetration depth, a 13-14% knock downin tensile strength can be calculated. The average loss in tensile strength 

observed at 538°C ( 1 000°F) was 20% when comparedto the room temperature averagewhich is in reasonableagreement. 

A significant change was observed at 593 "C (1 100 OF) where resin loss was rapidly occurring. It would appear based 

on these observations that the primary strength loss mechanism for carbon reinforced phthalonitrile composites is resin 

loss at the surface. Accompanying the surface loss of resin there are other changes occurring in the phthalonitrile resin 

structure at these high temperatures, which may have an additional effect on composite strength. This involves a 

carbonization of the material but this effect has not been investigated in detail. 

Figure 2. Phthalonitrile Composite Variation of 

Failure Load with Temperature 

0 200 400 600 800 1,000 1,200 

TEMPERATURE (F) 1 I , I I 

-17.8 82.2 182.2 282.2 382.2 482.2 582.2 

TEMPERATURE (C) 

28 232 

25 96 
CONCLUSIONS 

The use of polymeric composite materials for airframe and spacecraft cabin applications offers benefits in a 

variety of areas such as improvements in weight, maintenance, corrosion control, and lower thermal conductivity. High 

performance composites that fit the Navy's flammability requirements of MIL-STD-203 1 for application in hull. 

machinery and structural applications inside naval submarines have not been available. The superior performance of 

phthalonitrile-based composites on exposure to a flame should enhance their importance for consideration by the 

aerospace industry in the design of a totally fire resistant cabin for future spacecraft. 

The phthalonitrile polymer offers many advantages as flame resistant and high temperature matrix materials 

for composite applications. The mixed prepolymerization composition and B-staged prepolymer are completely stable 

under ambient conditions and below the melt temperature. These compositions are especially useful in the fabrication 

of fiber reinforcedcomposites by RTM, filament winding, resin infusion molding, resin injection molding, and prepreg 

formulation from the melt in the absence of solvent. A user can readily make changes in the phthalonitrile/curing 

additive prepolymerization composition to meet the processing needs. No reaction occurs between the monomer and 

curing additive until melting commences. Conventional resins such as epoxies and polyimides must be stored under 

freezer conditionsand used in a short time frameupon addition ofcuring additive. Thephthalonitrile resin can be easily 

processed into void-free composite components. The data reveal that the phthalonitrile composites exhibit mechanical 

properties that are either superior or comparable to the state-of-the-art high temperature PMR- 15 composites. Panels 

post-cured at 375 "C do not exhibit a glass transition temperature up to 450 "C and retain about 90% of their initial 

modulus. Based on the excellent physical properties and ease of processability, phthalonitrile composites are finding 

uses in both marine and aerospace applications. 

ACKNOWLEDGEMENT 

The authors Lvish to thank the Office of Naval Research for financial support of this work. 

REFERENCES 

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Keller, T. M. and Price, T. R., J. Macrornol. Sci.-Clieni., A18(6), 931 (1982). 

Keller. T. M. and Criftith, J. R., .4CS Svmp. Ser.:Rcmh.y,for ..ierospace, 132. 25 (1980). 

Keller, T. M.. ilCS Po/\m Prep., 33(1), 422 (1992). 

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Critchley, J. P. and Wright, W. W.. RevieH:y on High Temperature Materials, 4, 107 (1979). 

Pater, R. H., NASA Technical hlcwrorandimi 53050 ( 1982). 

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Sastri. S. B.. Armistead. J. P., and Keller, T. M.. Polyni. Conip.. 18 (1). 4X (1997). 

Sastri. S. B.. Armistead, J. P., Keller. T. M. and Sorathia. U., SAMPE $\nip. Ser-.. 42. 1032 (1996). 

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h.lachiner?* and Stnictural Applicatiotis inside Naval Submarines ( 199 1 ). 

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Babrauskas, V. and Peacock. R. D.. Fire Sqfi.~, .Journal, 18,255 (1992). 

Micro-scale calorimetric experiments were performed by R. E. Lyon and R. N. Walters at the Fire Research 

Section, Federal Aviation Administration, Atlantic City, New Jersey. 

Lyon, R. E.. Thrust Arc, Projcct Update, 7th Meeting ?/' the Ititi~ragiwc~~~ Rbrkiiig Group on Fire and 

h!atc~rials (IWGFM- 71, ( 1996). 

DiGiovanni, P. R.. and Paterson, D.. "High Temperature, Short Term Tensile Strength of C6000iPMR- 15 

Cotnposites", Ifiglr Ttwipiwature Poljnier Matrix Composites, Noyes Data Corporation, New Jersey. 1987, 

pp. 254-366. 
Real Time Video Recording of Extremely High Temperature Processes 

Thad Hoffman 

Control Vision Incorporated 

PO BOX 5 1505 

Idaho Falls, ID 83405 

Phone: 208 S23.5 506 

Email1 vision@controlvisioninc.com 1 

Introduction 

or with standard video and photographic cameras. Details such as the behaviors of the solid or molten material, 

surface contaminants or cracks are obscured by the incandescence coming from the surface itself. Additionally, 

when attempting to view processes with relatively small areas of overwhelming brightness, such as laser welding, the 

image is additionally degraded by the extreme brightness variation across the image area, making it impossible to 

achieve proper exposure throughout the scene. 

Surface details of materials at extremely high temperatures are quite difficult to monitor with the human eye 

The key to obtaining an image that is properly exposed and shows surface detail lies in using reflected 

illumination. Reflected illumination provides the basis for almost all of our natural viewing capabilities relying on 

either natural or artificial lighting to see almost everything in our daily lives. A good example of the principle of 

reflected illumination can be found in the difference of appearance when viewing the Sun versus the moon. Viewing 

the sun directly, even with heavy attenuating filters, tells us nothing about the surface since the sun radiates intensely 

across the visible spectrum. The moon, however, does not radiate in the visible spectrum. Our image of the moon is 

created by reflected light from the sun. Using the sun’s illumination, we are able to see a tremendous amount of 

surface detail such as craters, valleys and peaks. 

Recent electro-optical innovations in charged coupled device (CCD) chip technology and various efficient 

light sources have provided the basis for implementation of real-time videographic techniques for viewing and 

recording surface conditions of high temperature processes. This paper describes a basic system design and the 

implementation of these techniques to a variety of high temperature industrial processes. 

Hivh Temperature Video System Description 

CCD video camera head, an external light source, a controller unit, a video monitor and a video recorder. Figure 1 

shows a block diagram of such a system. 

A video system used for viewing the surface of high-temperature processes, includes a custom designed 

Smbe Unit 

Cameratiead 

Figure 1 
Strobe Unit 

The video system is able to overcomes brightness associated with high energy industrial processes with use 

of an intense pulse of light. A xenon flashlamp strobe unit is typically used, but pulsed laser illumination is also an 

option for very demanding applications. The broadbanded output energy of the of the typical strobe unit is about 20 

millijoules per flash. The strobe output is intense enough to overpower the brightness typically associated with high 

temperature, high energy processes. Use of a pulsed light source such as a strobe also provides an additional benefit 

when dealing with motion. The 5 microsecond pulse is sufficient to eliminate any motion-induced blur within the 

image. 

Strobe energy can be delivered to an area of interest in several ways. For close-up applications such as 

laser welding, the most common delivery method is through the use of a fiberoptic bundle. Typical bundle diameters 

are under 0.75" and the bundle can be configured in a variety of lengths depending upon installation requirements. 

The fiber strands are encased within flexible stainless steel sheathing for strength and protection. A transparent 

protective window is usually secured to the output end of the bundle for protection from welding spatter, etc. For 

applications that may require larger stand-off distances, projection optics can be mounted onto the strobe unit. These 

optics produce a well-collimated beam and uniform illumination spot from distances of up to 60 feet away. 

Camera Head 

Pixel resolution is 480 by 640 providing 256 levels of gray scale output. The camera head is approximately the size 

of a pack of cigarettes and weighs only a few ounces. The head is teathered to the controller unit by means of a 20- 

foot multiconductor cable and can be situated remotely from the controller unit at even greater distances, if 

necessary. A variety of optical components specifically designed for typical operating conditions are available for 

use with the camera head. A standard C-mount lens attachment also allows for integration with standard video 

camera optics ranging from video microscopes to ordinary wide-angle and zoom lenses. 

The custom-designed video camera head incorporates CCD technology into a small, lightweight package. 

Controller Unit 

The controller unit fires the strobe unit synchronously with the video framing cycle of the camera head. 

The video image is then created predominately by means of reflected strobe illumination, which overwhelms the 

brightness of the scene and produces very highly contrasted video imagery of the high temperature surface. 

Additionally, the controller unit controls various other system functions, such as video framing rate and camera 

sensitivity. The standard RS- 170A video output signal is compatible with all video recording and display systems. 

The system is typically used with a video recorder and microphone to monitor the audio signature of a particular 

sequence and to allow the operator to describe specific operating conditions of the process under investigation. In 

more advanced applications, the camera provides video to a desktop PC configured for digital video image 

processing. 

Example Applications 

Pulsed Yar Laser Welding 

characterized by peak power levels in the multikilowatt range, usually delivered through a fiberoptic 

cable for relatively small-scale, precision welding 

applications. Figure 2 shows a typical pulsed Yag 

welding operation. Note the bright plume emanating 

from the weld. Unfortunately this plume causes severe 

saturation and blooming in the video image when a 

standard video camera is used for close-up viewing. 

Pulsed Yag laser welding can typically be 

Figure 2 
Figures 3 and 4, however, show very clear images of the welding process. No evidence of the plume is seen. 

Figure 3 Figure 4 

Through the use of an external trigger function, it is possible to view the laser welding pulse at various 

stages of development. A timing pulse from the laser power supply is used to trigger the video camera system. In 

these examples, the laser pulse energy is about 10 Joules, with a 2.5 ms pulse duration and 4 Kw peak power. The 

welding pool diameter is approximately 2 mm across and the transverse field of view is about 9 mm. Figure 3 shows 

the weld at 1.64 ms of shutter trigger delay, so as to capture a picture during the laser pulse. (Trigger delay is the 

time between receipt of the leading edge of a pulse from the Yag laser welder power supply and triggering of the 

camera system.) Note the incandescence of the pool of molten metal. Figure 4, however, was taken at 3.2 ms trigger 

delay, following the laser pulse. Note the ejection of molten metal and a drop in incandescence of the molten metal 

that indicates a drop in the temperature the pool. 

C02 Laser Heat Treatment 

using a CW CO2 laser beam with a rectangular cross-section. 

The heated material appears as light gray against the darker, 

un-heated surface. The purge gas nozzle is seen in the upper 

right hand corner of the video frame. The goal is to heat the 

surface almost to the point of melting, but the dark splotches 

on the light gray surface indicate the presence of some molten 

areas, thus indicating a need to decrease the laser beam power 

or increase the travel speed of the beam across the surface. 

Figure 5 shows heat treatment of a metal surface 

Pulsed Gas Metal Arc Welding (GMAW) 

video of a pulsed gas metal arc welding process. Figure 7 shows video obtained using the high temperature video 

camera system. In this case, intense laser illumination is used to illuminate the welding wire and molten pool. The 

behavior of the wire and droplets is observed during the weld. An external timing reference can be obtained through 

a small sensor that, when placed around the work lead, senses changes in weld current. Using this timing reference it 

is possible to selectively view the transfer of droplets from the wire to the molten pool at specific delay times from 

the weld pulse. 

Figure 5 

Figure 6 shows an example of typical camcorder 

Figure 6 
Iron Making 

shows a video frame taken from an ordinary video camcorder. We see a natural gas flame coming from a trough 

filled with molten iron which has been tapped from a blast furnace. The surface temperature of the iron is over 1,500 

degrees centigrade. Figure 9 is taken with the high temperature video system. In this image the flame and 

incandescence in the scene are overcome by strobe illumination in order to observe the surface of the molten iron. 

The molten iron appears as pool of mercury at room temperature. Small amounts of slag can be observed on the 

surface. The reflective nature of the slag is different from molten iron in that the slag is diffuse while the molten iron 

is specular, tending to reflect strobe energy away from the camera. 

The high temperature video technique has been used in steel making operations. As an example, Figure 8 

Figure 8 Figure 9 

Continuous Casting 

continuous caster machine. Figure 10 is a camcorder shot of the cast product as it exits the casting mold. The 

surface temperature is very near molten steel temperatures. Figure 11 shows the high temperature video camera 

image of the same surface. Use of reflected strobe illumination makes the surface appear as if it was at room 

temperature. Surface features such as the crack seen on the right third of the video frame are readily apparent. In 

this case, the strobe illuminator was placed at 90 degrees to the viewing direction and obliquely to the surface of the 

cast product. This approach to illuminating accentuates surface details, such as the crack, by creating shadows. 

Another example of high temperature video camera use can be found with viewing the output of a 

Figure 10 Figure 11 
Twin Wire Arc Spray 

With twin wire arc spray an electrical arc is generated between the two consumable wire electrodes exiting 

the orifice of a spray gun. Pressurized air is used to accelerate the molten droplets against a substrate. 

shows a camcorder shot of a typical twin wire arc spray process. In contrast, figure 13 shows the close-up details of 

the twin wire arc spray process using the high temperature video camera system. As with pulsed gas metal arc 

welding, a small, pulsed laser is used to illuminate the process, creating detailed video of wire atomization without 

arc light overwhelming the image. 

Figure 12 

Figure 12 Figure 13 

Conclusion 

Highly contrasted video observation of details on high temperature, incandescent surfaces requires viewing 

the surface by means of reflected illumination rather than relying upon the visible radiation coming from the surface 

itself. Recent innovations in the field of electro-optics make such a video system practical and affordable. 
I' 

. r-L 

/ 

VAPOR GROWN CARBON FIBEWPHENOLIC MATRIX COMPOSITES FOR 

ROCKET NOZZLES AND HEAT SHIELDS 

R.D. Patton", C.C. Pittman, Jr. '. L. Wang' , J.R. Hilld, A. Day' 

"Mech. Eng. Dept., PO Box ME, Mississippi State University. Mississippi State, MS 39762 

hChemistry Dept., PO Box 9573. Mississippi State University. Mississippi State, MS 39762 

'Chem. Eng. Dept., PO Box C H, Mississippi State University, Mississippi State, MS 39762 

3536 Idaho Rd., Charleston AFB, SC 29404 

Thiokol Propulsion, PO Box 9033. Huntsville, AL 358 12 

ph: (662) 325-73 I1 fax: (662) 325-7223 email:- .I corr. author) 

d 

ABSTRACT 

The ablation. mechanical and thermal properties of vapor grown carbon fiber (VGCF) (Pyrogaf IllT" 

Applied Sciences. Inc.)/phenolic resin (SC- 1008, Borden Chemical, Inc.) composites were evaluated to determine 

the potential of using this material in solid rocket motor nozzles. Composite specimens with varying VGCF 

loading (30%-50% wt.) including one sample with ex-r;ayon carbon fiber plies were prepared and exposed to a 

plasma torch for 20 sec. with a heat flux of 16.5 MWim- at approximately 1650°C. Low erosion rates and little 

char formation were observed, confirming that these materials were promising for rocket motor nozzle materials. 

When fiber loadings increased, mechanical properties and ablative properties improved. The VGCF composites 

had low thermal conductivities (approximately 0.56 Wim-OC) indicating they were good insulating materials. If a 

h9;, fiber loading in VGCF composite can be achieved. then ablative properties are projected to be comparable to 

or better than the composite material currently used on the Space Shuttle Reusable Solid Rocket Motor (RSRM). 

Keywords: A. Carbon fiber; B. Ablation; Thermal properties; Mechanical properties 

INTRODUTION 

The ablation. mechanical and thermal properties of some recently prepared vapor grown carbon fiber 

(VGCF) (Pyrograf HITM Applied Sciences, Inc.)/phenolic resin (SC- 1008, Borden Chemical, Inc.) composites are 

reported herein. The purpose was to begin evaluation of this material for use in solid rocket motor nozzles and 

related applications. 

Applied Science. Inc. (ASI) manufactures the only commercially available supply of vapor grown carbon 

fibers. (VGCF). The Pyrograf HITM vapor grown carbon fibers from AS1 have a diameter range of between 100 - 

300 nm and of lengths varying between 10 and 100 ym[l-4] The aspect ratio. l/d (Iengthldiameter). for VGCF 

ranges between 100 and 1000[ I]. Unlike most fibers used for composite reinforcement, VGCFs come in a fluffy 

mass where the fibers are curved and intertwined[l-41. Figure 1 shows a Scanning Electron Microscope (SEM) 

view ofa sample of Pyrograf IIIm VGCF. 

Figure 1 Scanning Electron Microscope View of Pyrograf IllTM VGCF 

Vapor grown carbon fibers are produced by introducing an aerosol spray of a metal salt (usually Fe") into 

a chamber of hydrocarbon gas (Le.. methane or natural gas) heated to 1000 - 1200 "C [2-41. Figure 2 depicts the 

production of VGCF [2]. 
Figure 2 Three-Dimensional Growth of Fibers in a Reaction Chamber [2] 

The activation of-the iron particle catalyst causes the initial graphitic carbon filaments to form [1-41. The 

carbon filaments may lengthen for several minutes until the catalyst deactivates [S,6]. Since the iron particle 

becomes the nucleation site for the fiber tip, the initial carbon fiber diameter is directly proportional to the iron 

particle diameter, i.e., 10 nm [2,S.7]. The filaments then lengthen and thicken further by chemical vapor 

deposition of carbon onto the graphitic substrate [SI. The thickening process forms concentric, cylindrical sheaths 

around the initial filament [2,5]. These cylindrical sheaths develop a cross-sectional tree-ring morphology [5.6]. 

The final filament structure has a graphitized core covered with layers of pyrolytic carbon of lower graphitization 

[6.7]. This tree-ring morphology is illustrated in Figure 3 [SI. 

Figure 3 Transverse Section of a Vapor Grown Carbon Fiber Showing Tree Ring Morphology [5] 

Vapor grown carbon fibers have two main advantages, cost and availability. VGCF can be very 

inexpensive due to their size and by the use of natural gas as the source of hydrocarbon gas [3,4]. Fiber diameter 

is a cost driver for VGCF [4]. The smaller fibers like Pyrograf IllTbf require less time in the reaction chamber, thus 

reducing cost [3,4]. Pyrograf l,TMwhich has a fiber diameter between 1 - 100 pm (i.e., 10 to 300 times the size of 

Pyrograf lIITb'). is much more expensive. 

Disadvantages of Pyrograf HITM VGCFs include obtaining a non-standardized product, lack of a detailed 

knowledge of their material properties, and packing problems. Since Pyrograf Illm' fibers are so small, the 

individual fiber material properties can not be readily measured [3,4,7]. although Patton and Pittman have recently 

reported lower limits for their flexural moduli and flexural strengths [3,X]. Mechanical properties have been 

measured for much smaller carbon nanotubes by atomic force spectroscopy [9]. However, these techniques can not 

be used on Pyrograf IllTM fiber, because they are too large. Pyrograf IllTb1 material properties are assumed to be 

similar to Pyrograf ITM material properties. since their preparation differs only in the growth time used. However, 
the ratio of pyrolytic carbon outer region to the tubular graphite inner core is different for these two classes of 

fibers. Table I lists the inaterial properties for Pyrograf ITM fibers. 

Table 1, Properties of Pyrograf IT" Fibersn 

Property Value Units 

Fiber Diameter 1 - 100 Clm 

Tensile Strengthh 2.7 Gpa 

Tensile Modulush 400 GPa 

Ultimate Strain 1.5 %" 

Density 1 .x gicm' 

Coefficient of Thermal Expansion -1.0 ppm/"C 

"Source: Ap lied Sciences. Inc. 

"Pyrograf Ill r: h! ranges: tensile strength 1.7-3.38 GPa. tensile modulus 88-166 GPa [8] 

Mechanical properties control many applications of composites, and much VGCF composite research has 

focused on determining these properties [lo]. Chellappa et. al. [ll] Shui and Chung, [ 121 as well as Ciminelli 

et. al. [I] obtained poor mechanical properties when testing VGCF composites. Chellappa et. al. [ 1 13 attributed 

poor mechanical results in the VGCF composites they prepared to (I) poor fibedmatrix adhesion. (2) poor fiber 

dispersion. (31 the presence of voids, and (4) using a weak thermoplastic elastomer matrix having a 0.1 MPa 

ultimate strength. Shui and Chung [ 121 as well as Ciminelli et. al. [I] attributed the poor mechanical properties 

to insufficient bonding between the VGCF and the matrix. It is also likely that they achieved poor fiber wetting 

and poor fiber dispersion 

The first strength improvements in VGCF composites were observed at Mississippi State University by 

Patton, Pittman. and Wang. [3,4,8]. The main variable contributing to these strength improvements was the use 

ot'pre-cure high shear mixing techniques. This aided in resin infusion, which is one of the two most important 

problems associated with making VGCF composites. Composites with high fiber volume fractions did not have 

any strength improvements. These composites had poor mechanical properties due to their high porosity resulting 

from fiber packing problems. Packing is the second significant problem. Random three-dimensional packing of 

the VGCF. which have a high aspect ratio, leads to a low theoretical packing fiaction. Hence, void free 

composites require high resin volume fractions. 

The thermal properties of VGCF composites have not been as widely studied. Shui and Chung [12] 

showed the thermal conductivity of VGCFipolyether sulfone composites increased with fiber loading. Our group 

showed the thermal conductivity of VGCF composites with acrylonitrile-butadiene-styrene (ABS) and epoxy 

matrices increased with an increase in the fiber loading [8]. However. these increases were small. VGCF 

composites are not thermal conductors. 

VGCF composites are being considered as a new material for the rocket nozzle of the space shuttle 

reusable solid rocket motor (RSRM). Currently NASA uses MX-4926, which is composed of two different 

reinforcements: woven ex-rayon carbon fiber from Avtex Fibers, Inc., and carbon black filler. The matrix is a 

phenolic matrix. SC- IO08 Borden Chemical, Inc [ 131. The high-temperature and high-velocity exhaust produces a 

pressure of 6.89 MPa and a temperature of 1650 "C in the RSRM's rocket nozzle during firing [ 14,151. Not only 

does the rocket nozzle material have to be a good insulator, but it also must have superb ablative properties 

[14,15]. 

MANUFACTURING VAPOR GROWN CARBON FIBEWPHENOLIC COMPOSITES 

VGCF/phenolic resin composite specimens were prepared by high shear mixing followed by thermal 

curing. Table 2 lists the 19 composite specimens made, mixing method used, their composition (wt.), density, 

void content. and fiber volume fraction. and the tests performed on each specimen. The VGCFiphenolic 
composite specimens were tested for ablation. mechanical, and thermal properties. The cure cycles for all samples 

were held constant. Four types of samples were made for material testing. The compositions, expressed as 

wt./wt., were 30170 VGCFiPhenolic, 40/60 VGCF/Phenolic. 40160 VGCFiPhenolic (where ball milled asreceived VGCF was used) and 4515150 VGCFlex-Rayon woven cloth1Phenolic. Two types of fiber were received 

from ASI: as-received and compacted fiber. The compacted fiber was from a different batch than the as-received 

fiber, and it had been subjected to post-production compaction processing. VGCF composites made from 

compacted fiber had significantly higher flexure strengths than comparable samples made from as-received fiber. 

Compacted fiber was not used in any ablation test specimens. Due to supply problems, the compacted fiber was 

employed in the 45/5/50 VGCF/ex-rayon/phenolic samples. which were used in mechanical and thermal tests. 

These properties may differ somewhat from the baseline properties established with as-received fiber. All 

specimens used in ablation testing were made from as-received VGCF, so they are directly comparable. 

Table 2, VGCF/Phenolic Composite Sample Properties 

Sample Fiber Fiber Sample Sample Void Fiber Test Mixing 

Number wt. Type Weight Density (YO) Volume Type' Typeb 

(Yo) (g) (dcc) (Yo) 

1 30 As-received 16.25 1.416 1.5 20.23 M CG 

2 30 As-received 17.2 1 1.399 2.73 19.99 M CG 

3 30 As-received 17.87 1.396 2.95 19.94 T CG 

4 30 As-received nia nia da nla A HS 

5 40 As-received 18.45 .46 1 3.02 27.83 M CG 

6 40 As-received 18.58 .453 3.59 27.68 M CG 

7 40 As-received 18.29 ,462 2.95 27.85 T CG 

8 40 As-received n/a nla w'a nla A HS 

9 40 Ball milled 14.99 ,484 1.42 28.27 M HS 

10 40 Ball milled 15.21 .48S I .35 28.29 M HS 

28.21 T HS 

A HS 

11 40 Ball milled 14.92 1.48 1 1.63 

12 40 Ball milled n/a n1a nia tva 

13 4513' Compacted 25.53 1.477 6.04 3 1.714.3' - CG 

14 451'5' Compacted 26.20 1.426 9.81 30.61'4.2' M CG 

15 4515' Compacted 26.62 1.426 9.81 30.614.2' T CG 

16 4515' As-recei ved nia n/a nia n/a A HS 

17 40 Compacted 22.15 1.49 1 0.95 28.40 M CG 

18* 0 nia 20.17 1.312 3.5 0 T nia 

19 40 As-received nia nla nia w'a 3DT HS 

a M=mechanical testing. T=thermal conductivity, A=ablation, 3DT=3D thermal conductivity 

HS=high shear sequence using Brabender and two roll mill after coffee grinder, CG=coffee 

ground only 

Ex-Rayon Carbon Fiber 

Pure Phenolic Sample 

Ablation test specimens (specimens 4,8,12.16) were prepared as 79.4x54x35.6 mm blocks. They were 

cut into six specimens, which were 25.4~25.4~35.6 mm in size. Specimens 1-3, 5-7, 17 and 18 were 

69.9~41.3~2.5 mm in size. Specimens 9-1 1 were 69.9~41.3~2.5 mm specimens and had been cut from one larger 

block. Similarly, specimens 13-15 were also 69.9~41.3~2.5 mm and cut from a larger block. Specimen 19 was 

the same size as the ablation specimens 4, 8, 12 and 16. Thermal conductivity specimens were cut from three 

different faces of specimen I9 in order to test for the anisotropy of thermal conductivity in these specimens. 

The thermal conductivity specimens 3, 7, 1 1, 15 and 18 were cut into two identical 3 I .8x3 1.8x2.5 mm 

pieces for use in the guarded hot plate thermal conductivity test. Mechanical test specimens 1, 2. 5. 6. 9. IO. 13. 

14 and 17, each of which are 69.9x41.3x2.5 mm in size. were cut into five specimens of*40xIOx2.5 mm for the 3- 

point bending test. 
1) Volume reduction 

Ball milling was used to reduce the volume (increase the volume fraction) of the as-received VGCF. The 

ball mill consists of a cylindrical container with internal side brackets fastened to its walls. which continually 

lifted and dropped the balls onto the fiber. Three different ball diameters are used; 3.1 8 mm, 6.35 mm. and 12.7 

mm; and approximately 300 balls are placed inside the ball mill. The fibers were ground in a high-speed blender 

before ball milling. A small amount of water was used during the grinding to aid the volume reduction. 

Significant volume reduction occurs after approximately 30 seconds of grinding. Then the fibers were dried at 

I2 I "C for 4 to 6 hours. Dry fibers were necessary for ball milling because excess water in the fiber cushions the 

impact during ball milling. The VGCF was ball milled for 16 hours. The results of this two step grinding 

process on VGCF are shown in Table 3. The volume reduction factors ranged between 2.94 - I 1.5. The average 

total reduction factor was 5.34 for these samples. 

Table 3, Volume Reduction of VGCF by Grinding and Ball Milling 

Sample Weight Original Volume After Volume After Total Factor 

Number (g) Volume Grinding Ball Milling Reduction 

I 20. IO 687.5 500.0 233.8 2.94 

7 40.67 1437.5 887.5 300.0 4.79 

3 42.3 I 1500.0 875.0 3 12.5 4.80 

4 40.67 1500.0 1020.0 250.0 6.00 

5 40.8 I 1480.0 812.5 375.0 3.95 

6 40.80 1450.0 687.5 437.5 3.3 1 

7 40. I3 1500.0 625.0 250.0 6.00 

x 40.24 1500.0 1000.0 312.0 4.80 

9 40.24 1437.5 875.0 125.0 11 .50 

(mu (mu (mu 

Average 38.44 1388.1 809.2 288.4 5.34 

2) Mixing 

VGCFiphenolic resin composites were prepared by a multi-step mixing process followed by a vacuum 

treatment to remove the isopropyl alcohol solvent from the phenolic resin. First, the fiber and resin were hand 

mixed for approximately one min. Then, the fiber!'resin mixture was placed into a high speed coffee grinder and 

ground for 2 min. A further two step high shear mixing sequence was used when preparing the ablation test 

specimens 4, 8, 12 and 16 and mechanical test specimens 9-1 I. In the first step, the fiberiresin mixture was put 

into a Brabender high shear mixer at 100 rpm for 30 min. This was followed by 2-roll milling at 50" C at speeds 

between 50-80 rpm for 30 min. Other composite samples, used for mechanical and thermal conductivity tests. 

(samples 1-3. 5-7. 13-15 and 17) were not large enough for the high shear mixing in the available sized 

equipment. Once mixing was complete. the isopropyl alcohol was removed, iri \~aciro, at 70 mm Hg for 48 h. 

3) Composite Curing 

Samples were cured by heating under pressure in a mold. The mold was placed into the hot press and 

heated to 80°C at 5.1 MPa for 30 min. Then the temperature and pressure were increased to 104°C with 15.3 

MPa for 90 min. Finally the temperature was again increased to 138°C while the pressure is held steady at 15.3 

MPa for another 30 min. This allowed the water of curing to diffuse out without distorting the composite or 

causing voids. 

TESTING PROCEDURES AND RESULTS 

Densitt 

Density measurements were made so that the percent voids and fiber volume fractions could be 

calculated. The void percent indirectly indicates the quality of the resin infusion. Composite density and weight 

measurements were made with the Electronic Densimeter Pyknometer Model # ED-120T. AFD Ltd. Density 

measurements were performed on the composite samples used for mechanical and thermal conductivity 
measurements. The ablation test samples were too large tor the densimeter's reservoir. Table 2 lists the VGCF 

composite samples, their fiber weight fractions. densities, percent voids, mixing regime and which tests were 

performed. 

The void percent was less than 3% for most of the samples (Table 2) indicating relatively good resin 

infusion; however, the void contents in samples 13. 14, and 15 are much higher than 3%. This is probably due to 

delamination cracking between the ex-rayon carbon fiber layers. which occurred when specimens 13-1 5 were cut. 

Mechanical TestinP 

The flexural strengths and flexural moduli were obtained from 3-point bending tests, and conducted in 

accordance with ASTM standard D 790M-93 using a Zwick Materials Testing Model #I435 (f 1% accuracy). A 

total of ten 3-point bending tests were performed for each composite type. The span was 30 mm, the width was 10 

mm, and the thickness was 2.5 mm. Calculated values of the flexural strength and flexural modulus have an 

accuracy of f 55;. The 3-point bending tests were performed on specimens I, 2, 5, 6, 9. 10, 14 and 17. The 

results are shown in Table 4. 

Table 4, VGCF/Phenolic Composite Flexural Strength and Flexural Modulus 

Composite Sample # Yo w f Flex. Strength Flex. Modulus 

(Yo) (MP4 (CPa) 

1 30 25.6 k 1.3 1.07 * 0.05 

7 30 25.lf 1.3 0.92f 0.05 

5 40 26.1 f 1.3 1.1 If 0.06 

6 40 32.4 _+ 1.6 1.20 f 0.06 

9 4Od 33.2 1.7 2.76 * 0.14 

IO 40" 35.2f 1.8 2.21 f 0.1 1 

14 4515h 50.7 f 2.5 2.26 f 0.1 1 

17 40h 54.0 f 2.7 2.69 k 0.14 

Ball Milled Fiber and Extra High Shear Mixing 

Compacted Fiber 

The flexural strengths and moduli were low for these samples. Significant modulus increases occur for 

the ball milled and high shear mixed samples 9 and IO, which had lower void volumes. The two specimens made 

with compacted fiber, sample 14 and sample 17, had higher flexural moduli and strengths. Sample 14 suffered 

some delamination cracking when being cut, which probably reduced its strength and modulus. 

Thermal Conductivits Testing 

The thermal conductivities were measured according to the ASTM C 177-85 standard test method for 

steady-state heat flux measurements and thermal transmission properties using a guarded-hot-plate apparatus [ 151. 

Testing temperatures ranged between 22.2 "C and 93.3 "C. This temperature range IS much lower than conditions 

inside the space shuttle solid rocket motor nozzle. A specimen size was 3 13x3 1.Xx2.5 mm was used. 

Table 5 displays the measured thermal conductivities. All of the composite samples exhibited similar 

thermal conductivities (54 to .62 W/m--"C). These values were only about twice that of the cured phenolic resin 

without fiber (.2X W/m-"C). 
Table 5, VGCF/Phenolic Composite Thermal Conductivities 

Composite Sample # Fiber wt. (YO) Thermal Conductivity (Wlm-"C) 

18 0 0.28 k 0.07 

3 30 0.57 f 0.02 

7 40 0.54 f 0.01 

11 402 0.62 f 0.01 

I 15 451Sh 0.57 t 0.03 

'' Ball Milled Fiber and Extra High Shear Mixing 

Compacted Fiber 

The thermal conductivities in three dimensions were obtained on a 40160 VGCFiphenolic ablation test 

composite sample (sample 19, Table 2). Specimens were cut out of the top, side and front of the ablation test 

specimen. The results are shown in Table 6. They indicate that the material is roughly isotropic. differing by less 

than f 9. I"0 from the average in all 3 directions. 

Table 6, Three-Dimensional Thermal Conductivity Testing 

40/60 VGCF/Phenolic Specimen Thermal Conductivity Percent Difference 

Orientation (W/m-"C) (%) 

Side I 0.8275 f 0.0407 6.25 

Side 2 0.7080 f 0.0276 9.09 

TOP 0.7788 f 0.0374 

Ablation Testing 

Thiokol, Inc performed all ablation testing at the NASA Marshall Space Flight Center. A Plasma Torch 

Test Bed was used for ablation testing. This test simulates the firing conditions of the Reusable Solid Rocket 

Motor (RSRM), with the exception of the 6.89 MPa pressure produced inside the RSRM rocket nozzle. The 

plasma torch has B standoff distance of 25.4 mm and uses an argoninitrogen mixture. A heat flux of 16.47 

MW/m' is produced at a plasma temperature of 1649 "C. The ablation test has a 20-second bum time. Before 

each test began. the sample was preloaded with a 444.82 N force, called the starting load. At the end of the bum. 

the final load was measured. The final load was greater than the starting load due to restrained thermal expansion. 

Six tests were completed for each composition and the results were averaged (Table 7). 

Table 7, NASAlMSFC Plasma Torch Ablation Test Results" 

Composite Sample Erosion Rate % Weight Load Change 

pm/sec Change N - 

(mils/sec) (W (Ib) 

30/70 VGCF/PH 1.372 f 0.203 7.7 f 0.14 668.7 f 82.3 

(0.0543 f 0.0076) ( 150.3 t 18.5) 

40160 VGCFiPH 1.245 f 0.203 8.6 f 0.19 77 1 .O f 76.6 

(0.0487 f 0.0076) ( 173.3 f 17.2) 

30160 VGCFI'PHh 1.689 k 0.157 9.37 5 0.30 614.6 k 107.6 

(0.0665 f0.0062) (138.2 f 24.2) 

(0.0503 f 0.009) ( 142.8 f 12.0) 

45/5 50 VGCF,Ex-RayonIPH 1.278 t 0.229 8.76 5 0.21 635.3 f 53.3 

M X-492 6 0.787 f 0.080 10.4 5 0.21 1952.8 f 281.2 

(0.03 1 f 0.0034) (439.0 k 63.2) 

It Plasma torch test temperature 1649°C and heat flux 16.5 MWIm'. 

hBall Milled Fiber 

Ablation behavior was characterized by three parameters in the plasma torch test: erosion rates, specimen 

percent weight change, and the increase in load. NASA's standard nozzle material, MX-4926, was tested along 

with the VGCF composites. Thc MX-4926 composite is composed of woven ex-rayon carbon fiber. carbon black 
filler and a phenolic matrix. The MX-4926 has a larger total carbon loading, with 65% of the composite weight 

constituting either carbon fiber or filler. 

As compared to the MX-4926 baseline, the VGCF composites experienced: I) higher (58-1 14%) erosion 

rates, 2) lower weight losses (10-26%), and 3) lower load changes (60568.5%). Thus, the VGCF specimens had 

less char and heat penetration than MX-4926. Therefore, more weight was being lost at or near the surface of the 

specimen versus weight loss from subsurface thermal decomposition. The load did not change much with 

increasing VGCF content (30%-50% wt.). Furthermore, the load changes for the VGCF composites are 

significantly lower than that of the MX-4926 composite. Load change is an indirect measure of heat penetration 

and char depth. Increases in load change indicate an increase in heat penetration and char depth. The VGCF 

composites appear to be far better insulators than the MX-4926. The higher erosion rates of the VGCF samples 

probably reflect their lower carbon content. The VGCF samples had a significantly lower carbon loading (30- 

50%) than the MX-4926 composite (65%). 

Oualitative Observations of Ablation 

Sekeral interesting observations were made of the ablative action of these specimens. 

1) 

2) 

There was no bright spot where the torch impinged on the specimen. The heat appeared to be spread 

uniformly across the surface, indicating good in-plane thermal conductivity. 

The ablation proceeded with a flaking action. Very thin, small flakes of heated material would peel off from 

the specimen. This flaking action was uniform across the specimen for the higher carbon loading specimens 

(>30% wt.). 

Because the load change was low during these ablation tests, the heat penetration, and hence out-of-plane thermal 

conductivity, was low. Thus. in ablative conditions, the specimens appeared to have higher in-plane than out-ofplane thermal conductivity. This apparently contradicts the results for room temperature thermal conductivity. 

which were nearly isotropic. A possible mechanism to explain this would be the formation of VGCFicarbon 

matrix (with high thermal conductivity) flakes on the surface. followed by flaking. This is speculative: much 

further work needs to be done in this area. 

CONCLUSIONS 

VGCFiphenolic composites, prepared with extensive high shear mixing. should be made with higher 

carbon loadings (50%-65% wt.) and subjected to the plasma torch tests. They have exhibited good erosion 

resistance at low carbon loadings while exhibiting less weight loss and load change than the material currently 

used on the RSRM. 

The plasma torch testing indicates that this class of composites is a good candidate for future 

development for rocket nozzles and heat shielding materials. This is particularly true since both the VGCF 

manufacturing and processing technology is in its infancy. The carbon loadings used in VGCF composites so far 

have been much lower than that used in the MX-4926 composite. Much further work needs to be done at higher 

carbon loadings. 

The mechanical properties of the VGCF composites need improvement, Lower void volumes, better 

surface treatments for tibedmatrix adhesion and mixed VGCF/carbon fiber weavesicarbon filler combinations 

should be investigated. VGCFiphenolic composites are virtually unstudied and should be the target of future 

efforts. 

The VGCF/phenolic composites have a low thermal conductivity, and that they have roughly equal 

conductivity in all directions. This might imply that the fiber alignment is 3-D random, or if a higher order 

alignment exists in microregions, such microregions are randomly oriented within the macroscopic sample. 

ACKNOWLEDGEMENTS 

We acknowledge NASAiMarshall Space Flight Center, contract number NAS8-9709 1. task order number 

H-30 1 90D. and the Air Force Office of Scientific Research, Grant number F49620-99- 1-0 19 1. for support of this 

research. 
REFERENCES CITED 

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[31 

[41 

[51 

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Ciminelli DL. Keams KM. Ragland WR. Vapor Grown Carbon Fiber (VGCF) Composites 41" 

liiternutioiiul SAMPE St~niposiiini, March 24-28, 1996: 496-SO I. 

Dresselhaus MS. Gruplii~ Fihcw wid Filaments, New York: Springers-Verlag, 1988. 

Patton, RD. Pittman Jr. CU. Wang L. Vapor Grown Carbon Fiber Composites with Epoxy and PPS 

Matrices. Proceedings of the 29"' International SAMPE Technical Conference Series. 29, Oct. 28-Nov. 1 , 

1997. pp 77-87. 

Pittman Jr. CU. Wang L. Patton RD. Vapor Grown Carbon Fiber Composites with Epoxy and PPS 

Matrices. Extended Abstracts of the Xrd Biennial Conference on Carbon. 11, July 18-23, 1997. pp 298- 

299. 

Tibbetts GG. Beetz Jr. CP. Mechanical Properties of Vapour-Grown Carbon Fibers. J Physics D, 

1987;20:292. 

Madronero, A. Ariza E. Verdu Brandl MW. C. Barda C. Some Microstructual Aspects of Vapor-Grown 

Carbon-Fibers to Disclose Their Failure Mechanisms. J Material Science 1996;3 1(23):6 189-6193. 

Tibbetts GG. Doll GL. Gorkiewicz DW. Moleski JJ. Perry TA. Dasch CJ. Balogh MJ. PhysicalProperties of vapor-Grown Carbon Fibers. Carbon 1993;31(7): 1037-1047. 

Patton RD. Pittman Jr. CU. Wang L. Hill JR. Vapor Grown Carbon Fiber Composites with Epoxy and 

PPS Matrices. Composites: A 1999;30: 1081-1091. 

Chemical Eng News 1997; 75(39):23 

Vanhattum FWJ. Serp PH. Figueriredo JL. Bemardo CA. The Effects of Morphology on the Properties 

of Vapour-Grown Carbon-Fiber. Carbon 1997:35(6):860-863. 

Chellappa V. Chiu ZW. Jang BZ. Electrical Behavior of Carbon Whisker Reinforced Elastomer Matrix 

Composites. Proceedings of the 26'" SAMPE Technical Conference, 26. Oct 17-20, 1994, pp I 12- 1 18. 

Shui, X. Chung DDL. Conducting Polymer-Matrix Composites Containing Carbon Filaments of 

Submicron Diameter. 38'" International SAMPE Symposium. May IO- 13. 1993, pp 1869- 1875. 

SC 1008. Durite Phenolic Resin, Borden Chemical. Inc., Louisville, KY 

ASTM D 790-92 Standard Test Method for Flexural Properties of Unreinforced and Reinforced Plastics 

and Electrical Insulating Materials. 1994 Annual Book of ASTM Standards, Vol. 8.01 Plastics, pp 176- 

184. 

ASTM C 177-85 Standard Test Method for Steady-State Heat Flux Measurements and Thermal 

Transmission Properties by Means of the Guarded-Hot-Plate Apparatus. 1994 Annual Book of ASTM 

Standards. Vol. 4.06 Thermal Insulation; Environmental Acoustics, pp 20-29. 
Ambient Air Monitoring of Respirable Particulate Matter (PlQo) And Total 

Suspended Particulate (TSP) From the RD180 Rocket Engine Tests at the 

NASA Marshall Space Flight Center 

John Hughes & Kathy Lehr I John.Hughes(ii,ssc.nasa.pov 1 

Lockheed Martin Stennis Operations 

Test and Engineering Directorate 

GB Tech Sciences Laboratory 

SSC, MS 39529-6000 

Introduction 

The Sciences Laboratory operated by GB Tech was tasked by the Environmental Office at the NASA 

Marshall Space Flight Center (MSFC) to assess the impact of air particulate matter as a result of RD 180 engine 

testing. The method used for monitoring ambient air included measuring particles smaller than or equal to 10 

micron (PMlo), particles with diameters smaller than or equal to 2.5 microns (PM2.5) and Total Suspended Particles 

(TSP) that have a diameter size of 25 to 50 microns. This particulate matter represents small “dust like” particles of 

soot which are sufficiently small to disperse essentially like a permanent gas. Due to their small particle size, these 

particulates can be inhaled. The airborne concentrations are regulated and set by the EPA to prevent adverse effects 

associated with the inhalation of high levels of particulates. 

Dedicated samplers were used to collect the correct particle size from the ambient air. The samplers also 

maintained a controlled flow rate to determine the volume of air sampled. Particles were collected on micro quartz 

or glass fiber filters that were equilibrated and weighed (tare) and after (gross) sampling to determine the weight (net 

mass) gain of the sample. The concentration of the particles captured from the air was then computed as the net 

mass collected by the volume of air sampled. This method provides a measurement of the mass concentration of 

airborne particulate matter for the determination of compliance with National Ambient Air Quality Standards. 

Facility Description 

The facility comprises about 1841 acres and is located within the confines of the 3878 1 acre Redstone Arsenal. A 

general location map is provided in Figure 1. 

Marshall Space Flight Center (MSFC) is located in Huntsville, Alabama. (Madison County). 

I Figure 1 - MSFC Vicinity Map I 
Determination of Sampling Locations 

Predicted surface meteorological conditions at the time of testing were the determining factors in the 

selection of the general sampling locations wind direction and speed being the prime considerations. Other siting 

criteria included vertical placement, spacing from obstructions and roadways, availability of adequate electricity and 

security of equipment and monitoring personnel. 

Vertical Placement 

The optimal placement of the sampler inlet for PMio and TSP monitoring should be at the breathing level. 

The sampler air intake was located between 2 and 7 meters above ground level. The lower limit is based on a 

compromise between ease of servicing the sampler and the desire to avoid re-entrainment from dusty surfaces. The 

upper limit represents the desire to have measurements which are most representative of population exposures. The 

distance between the PM 10 inlet and the TSP was at least 2 meters to preclude airflow interference. 

Space from Obstructions and Roadways 

The samplers were located a minimum of 20 meters from trees and the nearest traffic lanes. An effort was 

made to locate all samplers away from obstacles such as buildings, so that the distance between obstacles and the 

samplers was at least twice the height that the obstacle protrudes above the sampler. This could not be 

accomplished at the on-site station (F- I Test Stand). The samplers did have an unrestricted airflow of a minimum of 

170 degrees around the sampler. 

Ground Preparation 

Each off-site location was selected using the siting location criteria provided above. It was not possible to 

locate all stations on a paved area to reduce the impact of fugitive dusts on the sample. The background samplers 

located at the F-1 Test Stand were placed on a paved area. The samplers at two stations on Redstone Arsenal Test 

Area # 1 : Redstone ## 1 Laser Tracker Trailer and Redstone #6 North Dodd Road were placed on concrete slabs. All 

other samplers were placed on the ground. 

The logistics associated with setting up the air sampling equipment are difficult and time consuming 

making it necessary to structure a decision as to the placement of the air samplers on the day prior to the test. 

Weather forecast information (Attachment 1 ) obtained from the Meteorology Branch of the Redstone Technical 

Test Center was used in that decision- making process. Using a look- up table referencing “Distance from Test 

Stand to Maximum Projected Pollutant Concentration for Various Stability Classes and Wind Speeds” (Modeling 

for RD-180 Test Firings at MSFC - Carolyn Kennedy, September 1998) as a guide, possible sites for sampler 

placement were determined using a top0 map of the area. 

October Test (002)- On Site Location 

Stand 4670 (SI -C). The on-site station consisted of one (1 ) PM 10 Volumetric Flow Controlled (VFC) High Volume 

The on-site monitoring station was located in the West Test Area at the F- 1 Test Stand, northeast of Test 
sampler and one (I ) TSP Volumetric Flow Controlled (VFC) High Volume sampler. 

established to obtain background PM 10 and TSP data. 

This monitoring station was 

9 

FIGURE 2 

i 

October Test (002) - Off-site Locations 

Based an the information gathered from the aforementioned sources, which forecasted winds from a 

northeasterly direction, the sites selected fell within the Redstone Technical Test Center, south of the SI-C Test 

Stand. Permission to locate equipment on the test range was received from the Test Center Director, Wes Widner. 

The Director provided the team with an escort familiar with the facility who was able to help identify on the map 

the pre-selected sampling locations. Six sets of air samplers were transported into the test area and one set each 

placed at six different locations. Each off-site station consisted of one ( I ) PM 10 (VFC) High Volume sampler and 

one ( 1 ) TSP (VFC) High Volume sampler. The off-site stations are depicted in Figure 2. 

Although the firing was scheduled for 4:40 pm, it seemed likely that the firing would not actually take 

place until later. The stability class for nightfall dramatically changes the distance from the test stand for which 

sampling equipment should be placed. Sampler sets numbers four, five and six were placed to incorporate this 

possibility of a later firing into the sampling plan, and in fact, the firing did not actually take place until 7:55 pm. 

The test duration was 2.7 seconds of a scheduled 56- second test. 

As established in Table 1, which shows wind speed and direction for the immediate hours following the firing, 

winds were predominately from the north- northeast and ranged from 0 to 1 knot. 
Based on the least and the greatest angle of wind direction, an approximate plume path is demonstrated in the 

illustration below. This indicates sampler sets numbers three and five were in position to intercept the plume. 

November Test (003) 

Forecasted weather information for the November 14Ih test indicated winds from the northwest. 

(Attachment 1). The Redstone Test Director had allowed the air sampling team to leave all the equipment in place 

since the October firing. With the prediction of winds from the northwest, the decision was made to leave all 

samplers in situ. The test was delayed and firing did not occur until 6:27 pm. The November test duration was 56 

seconds. 
2200 

2300 

2400 

As seen in Table 2, winds for a 4- hour period after the test were from the north-northeast or north-northwest at 3 to 

4 knots. 

10 NNE 4 4.55 

358 NNW 3 3.40 

350 NNW 4 4.50 

The approximate plume path for this test, as seen in the Diagram 2 below, indicates that sampler sets 

numbers three and four were in position to intercept. 
l7FW FROM SIC STANDSOlrlll 

TO REDSTOVE TEST RANCEAPPRO.MMATE 

AIR SAMPLER PLWEMEhT 

Wind Dir Wind Dir 

December Test (004)- The afternoon before the December 16th test, the air sampling team niet with 

Redstone meteorologists, Jim Young and Billy Longgrear in an effort to determine sampling strategy for the 

upcoming test. Another cold front was scheduled to move through the area possibly around the time of testing and 

northerly winds would prevail. Ahead of the front, wind directions and speeds were variable making it difficult to 

determine an appropriate placement for the equipment. In the expectation of northerly winds with the passage of the 

front, the existing sampling positions were maintained. Testing was delayed until 5:49 pm and lasted for 64 

seconds. Table 3 indicates that at the time of firing and for considerable time thereafter, the winds were swinging 

from south- southwest to west- northwest at 1 to 7 knots. The anticipated flow from the north did not in fact occur 

until around 0900 hrs, December I7lh. 

Wind Spd Wind Spd 

* Engine Ignition 

The approximate plume path seen illustrated below in Diagram 3, indicates that none of the samplers were 

in position to intercept the plume at the time of firing. 
1 Diagram3 I 

Principle of Operation 

Suspended particles in the air were sampled at 1.13 cubic meters per minute & 109h) through the 

circumferential inlet of the size selective inlet. The particles were then accelerated through 9 circular impactor 

nozzles. Because of their larger momentum, particles greater than the 10 micron cut-point impacted onto the 

greased impaction surface (shim). 
Analytical Procedures 

Analytical procedures were based on inertial separation occurring within the sampler unit and gravimetric 

analysis of the filter medium in the laboratory. The analysis of the filter consisted of determining the mass 

concentration of the filter by weighing the filter after sampling and moisture equilibration. The analytical balance 

utilized had a minimum sensitivity of 0.1 mg. The net mass gain was then divided by the total volume of air 

sampled, corrected to EPA reference conditions of 25OC (298 K) and 760 mm Hg. The total volume of air sampled 

was determined from the measured volumetric flow rate and the sampling time. 

S/N & 

LOCATION 

P1215fr3 

P1207 #6 

Data Handling and Retention 

Calibration records on all equipment were also maintained. Analytical results were compiled in a database. 

All log sheets, recorder charts and logbooks associated with the ambient air stations were maintained. 

PM-2.5 PM-2.5 PM-2.5 

CONCENTRATION pg CONCENTRATION CONCENTRATION 

1 std m3 fig I std m3 1 std m3 

1 O/ 14/98 1 1/04/98 1211 6/98 

8.785 7.454 3.761 

1 1.205 6.144 NC 

Analytical Results 

TABLE 4- PM-10 Particulate Data Summary 

NC = Not Calculated Due to Equipment Malfunction 

TABLE 5 - 2.5 Particulate Data Summary 
TABLE 6 - TSP Particulate Data Summary 

.- 

I std m3 ~g std m3 1-18 I std mi 

TSP TSP TSP I SM & I CONCENTRATION up I CONCENTRATION I CONCENTRATION 1 

P1185#1 

PI 187 #2 

P1193 #3 

P1197 #4 

P1192 #5 

Pl184#6 

P1194#7 

23.2 16 22.052 16.785 

22.250 18.732 16.001 

2 1.579 18.272 16.253 

25.985 20.334 50.759 

22.672 18.963 15.444 

26.636 19.35 1 NC 

27.797 17.69 I 15.361 

60 

50 

40 

30 

20 

10 

0 

PI 216-T1197 CONCENTRATIONS 

10/14/98 11/04/98 12/16/98 

mPM10 

lmw I 

1 2 3 

Hellfire Pit #4 
Conclusions 

Although the approximate plume path indications were excellent for the October test (002). the firing itself 

was only 7.4 seconds in duration. The particulate data for this test indicates that heavier concentrations were 

collected than for the tests 003 and 004. It is probable that the hazy “smog-like” conditions during this period 

depreciated the general air quality of the area and is responsible for the elevated background levels. Results from a 

diminished plume are not expected to be as representative as results from a full duration test. 

Environmental sampling conditions for the December test were such that it is unlikely that any particulates 

generated from the test firing were captured. The December data charts show lower concentrations of collected 

particulates with the exception of the spike seen at the #4 monitoring station. Shortly after the air samplers were 

prepared and set for the last engine test, Stennis personnel were asked to evacuate the RSA test range due to 

ordinance testing at the Hellfire Pit. Stennis personnel observed the Army’s testing activity near the monitoring 

station, #3 “Hellfire Pit”. Conceivably. detonating explosives near this monitoring station was responsible for the 

increased particulate loadings. 

With respect to cooperative sampling conditions and a full duration firing, the November test was probably 

the most representative of the sampling events. Taking into consideration the existing general weather conditions 

for the duration of each test period and the related particulate collection data, it appears that the air sampling events 

reflect the background particulate levels of the area. Consequently, RD-180 testing had little or no effect on ambient 

air quality. 
Gas Emission Measurements from the RD 180 Rocket 

Engine Tests at the NASA Marshall Space Flight Center 

H. Richard Ross 

Rick.Ross@,ssc.nasa.gov 

Lockheed Martin Stennis Operations 

Test and Engineering Directorate 

GB Tech Sciences Laboratory 

SSC, MS 39529-6000 

Introduction 

The Science Laboratory operated by GB Tech was tasked by the Environmental Office at the NASA Marshall 

Space Flight Center (MSFC) to collect rocket plume samples and to measure gaseous components and airborne 

particulates from the hot test firings of the Atlas 111 / RD 180 test article at the MSFC. This data will be used to 

validate plume prediction codes and to assess environmental air quality issues. 

This project was funded and administered through the NASA Environmental Office at the John C Stennis 

Space Center under Stennis Work Request MDS8800100. 

Bar kgrou nd 

NASA’s Marshall Space Flight Center in Huntsville, Ala., was under a Space Act agreement with Lockheed 

Martin Astronautics of Denver to provide a series of test firings of the Atlas 111 propulsion system configured 

with a Russian designed RD-180 engine. The RD-I 80 is being evaluated for use in the evolved Atlas that will 

replace the current MA-5 engine class. 

Plume samples were collected and analyzed for hot test firings 3 and 4 from the SIC test stand area on 

November 4 and December 16, 1998. Fourier Transform Infrared (FTIR) spectroscopy was used to measure 

carbon dioxide (CO,), nitrogen oxides (N&- ), and sulfur dioxide (SO, ). A dual beam non-dispersive infrared 

(NDIR) process was used to provide concentrations of carbon monoxide (CO). Total hydrocarbon content 

(THC) was measured using a flame ionization method. All gas components were measured in the ppm range. 

The EPA has set National Ambient Air Quality Standards (NAAQS’s) for criteria pollutants that identify 

ambient concentrations necessary to protect human health and welfare from any known or anticipated adverse 

effects of a pollutant. Four criteria air pollutants relevant to the releases associated with RD I80 engine testing 

have NAAQS’s. The pollutants include CO, N02, S02, and suspended particulate matter less than 10 microns 

in size (PMIO) which are airborne particles that are so small in size that they can remain airborne and disperse 

as a gas. Airborne particles were also collected and analyzed and is discussed in Part I1 of this report. 

The state of Alabama and the city of Huntsville have adopted the National Ambient Air Quality Standards 

(NAAQS’s) for criteria pollutants. 

Engine Description 

Pratt & Whitney at West Palm Beach has joined with NPO Energomash of Russia to market and to develop the 

license technology for the RD-180 engine. The engines are powered with liquid oxygen / kerosene propellants 

that feature a LOX lead start and a staged combustion cycle that provide 860,400 Ibs. of thrust at sea level. 
The RD 180 is a total propulsion unit that has the following features: 

High-pressure turbopump assembly that exhibits a two stage fuel pump and a 

single stage oxygen pump 

Oxidizer rich preburner and an oxidizer start and shutdown modes, 

0 2 thrust chambers with a chamber pressure of 3,734 psia 

0 50 - 100 9.0 continuous throttling 

Total system dry weight I 1,675 Ibs 

Self contained hydraulic system powered by kerosene from the fuel pump 

Facility Location & Description 

MSFC is located on approximately 1,841acres and is surrounded by a large federally owned area consisting of 

the US. Army’s, Redstone Arensal (RSA) and the Wheeler Wildlife Refuge. This area is a physical barrier 

between engine testing and the general public. Huntsville, Alabama borders on the east, north, and west; 

Madison on the west-northwest: and Decatur on the west-southwest. 

Development of space propulsion systems has been the primary mission of the MSFC since its establishment in 

1960. The U.S. Army has been developing and testing rocket engines at RSA soon after World War 11. 

RD 180 engine testing occurred at the Alternate Test Facility (AETF). The AETF is located in the southwest 

portion of MSFC and orientated to the west-southwest. This location places the AETF within the boundary of 

the Wheeler National Wildlife Refuge and is approximately IOOOft (305m) from the Wheeler Lake wetlands. 

The AETF was constructed in 1964 for the static testing of the Saturn V engines. This facility has also been 

known as the Propulsion and Structural Test Facility, S-1C Stand, Saturn Test Stand, and Technology Test 

Bed. The stand was modified in 1974 to perform shuttle external tank structural tests and again in 1986 to 

accommodate Space Shuttle Main Engine (SSME) testing. 

Sample Location and Collection 

At some location downstream of the nozzle exit, the exhaust temperature will be quenched or reduced below 

the temperature necessary for sustained combustion. Discussions with Dr. T Wang at NASA/ MSFC indicated 

the exhaust emission levels would achieve stability at a distance of approximately of 300 feet from the nozzle 

exit plane. The temperature at the sampling assembly was monitored during both engine tests and is discussed 

in the Test & Environmental Conditions section. 

A 20-foot sampling assembly was used to elevate the sampling cylinders. The sampling assembly was 

constructed from a 6 inch I beam steel column with a 5-foot horizitional platform welded to the top end. The 

platform was used for securing the sampling cylinders and thermocouples. 

Samples were collected in stainless steel GI cylinders with an internal volume of 2100 cu. inches. The 

Samplers were evacuated to less than 20 microns of Hg and were carried to the site approximately 8 hours 

before the test firing. The cylinders, thermocouples and electromagnetic valve cables were connected to test 

equipment and were fastened to the sampling assembly at ground level. After a final check was performed on 

all sampling hardware, a crane was used to lift and place the sampling assembly next to a 20-ton concrete 

block. 
The concrete block was used to the secure the sampling assembly. Chains were placed around the lower 

section of the I beam column and were fastened around the anchor block. Thermocouple cables and the 

electromagnetic valve control wires were fastened down the I beam column. Data loggers were connected to 

the output of the thermocouple cables to record plume temperatures. Each data logger was placed in a double 

wall plastic bag and was secured to the back of the I beam column 2 feet below the top of the concrete block. 

Sampling Assembly 

Installation 

Sampling Assembly 

Installed and 

Secured for Engine 

Exhaust Collection 
Sample Location Diagram 

Samdine Features 

- The plume control and sampling cylinders were elevated 20 feet at a distance of 250 feet west 

(downfield) from the flame bucket’s exit or 300 feet aft of the nozzle exit plane. 

- The plume sampling assembly (sample collection lines and the gas cylinders) was located 4 to 6 feet 

north from the center horizontal axis of the flame bucket. 

* The atmospheric control sample was not placed in the plume envelope and was located approximately 

100 feet north from the east boundary plane (front side) of the test stand at an approximate height of IO 

feet. This control was used to determine if any background contaminants were present during engine 

testing (e.g. exhaust from diesel engines that pump water to the AETF deluge system). 

* A 90 degree, !A’* x 3” stainless steel sample line was connected to the inlet port on each sampling 

cylinder through a two position electromagnetic valve. The atmospheric entrance of the sampling lines 

was pointed toward the flame bucket and was directed downward 90 degrees to minimize water 

intrusion. All sampling components are constructed from 304 stainless steel, except for the aluminum 

components of the electromagnetic valve. 

* The plume samples and atmospheric control sample were collected over a test period starting at T+3 

seconds. Sample collection was terminated at T+56 seconds. The plume control was collected 
over a period of T minus 2 minutes through T minus 1 minute. Time events of the sample collection 

were controlled by actuating the electromagnetic valves on the sampling cylinders via the firing 

sequence program at the Test Control Center (TCC). When the valve is open the sample flows into the 

evacuated cylinder under its own atmospheric pressure. 

- 3 Way, 2 Position, Electromagnetic Valves, Model - MV543 were used for collecting all samples. 

Operating Volts, 24VDC @ 1.33 Amps. When no voltage is applied to the sampling valve, the 

sampling configuration is closed. The closed configuration or "off' condition is the default setting for 

the sampling valves. Prior to T minus 2 minutes, all valves were in the default or closed configuration. 

- The plume deflector on the AETF (SI-C) test stand has a J shaped configuration. The flame bucket 

boundary exit faces west-southwest and has a 15 degree-inclination. 

Test & Environmental Conditions 

Air temperature measurements were performed at the sampling assembly to assure that the exhaust gas 

temperature was quenched or reduced below the temperature necessary for sustaining combustion. At this 

point no further production of combustion products will occur. A temperature rise was noted for each test, 

but is within the normal living range. Approximately 50% of temperature increase is attributed to the 

activation of the water deluge system. This condition has been observed on previous tests when water was 

flowing at the maximum rate to the flame bucket. but was suddenly shut off or reduced due to unplanned test 

delays. 

Water for the deluge is pumped to the test stands from above ground storage tanks at approximately 6 minutes 

before testing. NASA reported the water deluge system delivered 200,000 gallons of water per minute. The 

water exits the sides of the flame bucket through several hundred openings. Each opening has a diameter of 

5/32" at a pressure of 160 psig. This configuration generates an enormous spray volume that blankets the 

flame bucket and surrounding area, including the sampling assembly. 

To assure valid temperature measurements, two independent measurement systems were used. Each system 

consists of an Omega Model OM160 Data Logger, Model MOD-03/31 Signal Conditioner with a 

thermocouple probe, temperature range -4OC to 1 IO C ! -40F to 230 F. The thermocouple probes were 

fastened at the top of the sampling assembly adjacent to the inlet port of the sampling cylinders. A distance of 

3 feet separated each thermocouple. The temperature recording session started 8 hours before the test and 

ended approximately 18 hours later. The recorded measurements were down loaded to a PC and are reported 

for each test firing. Temperature measurements for both systems agreed within 10%. 

Test Firing 3 

Prior to the engine test, the air temperature at the plume sampling cylinders was approximately 8 degrees C . 

The maximum temperature recorded was approximately 27 degrees Co. 

0 

The firing occurred on November 4, 1998 at approximately 6:27PM. There was a heavy cloud ceiling at the 

time of the firing and it had been cloudy most of the day. Winds were out of the north - northwest at 5 mph. 

Test Firing 4 

Prior to the engine test, the air temperature at the sampling assembly was approximately I2 degrees e. The 

maximum plume temperature recorded during the firing was approximately 30 degrees Co. 

The firing occurred on December 16, 1998 at 5:47PM. The weather was clear with sunny skies for most of 

the day. Between 5:OO PM and 6:OO PM wind direction was variable (southwest to west southwest) due to 

an approaching weather front. Maximum wind speed was 10 mph. 
Max. Air Temperature at the Sampling Assembly 

]=Test 3 OTest 4 I 

15 

10 

5 

n ".....*........ 

0 0 0 0 0 0 0 c- r cv c3 c? 9 I 

0 Pre Test 

Time Scale (Minutes) 

Test Post Test - 

Engine Test Profile 

The LOX!fuel mixture for both tests was 2.72. Maximum throttle run of 90% occurred on test 3 and lasted 

26.55 seconds. The maximum throttle level for test 4 was 85%: this level was maintained for 12 seconds. 

Sample Pressure Measurements 

A Ruska Series 6200 Digital pressure gage (NASA ECN 036448) was used to measure the absolute pressure 

(psia) for all sampling cylinders. The Standards and Calibration laboratory at the NASA Stennis Space Center 

calibrated the gage. The gage is temperature compensated and has an accuracy of M.06 O/O full scale (50psia). 

To collect the field samples, the sampling cylinders were evacuated in the laboratory to less than 20 microns of 

Hg and were carried to the sampling site. The vacuum level in the samplers was the only process used to draw 

in the ambient air samples. After all samples were collected, the samplers were removed from the sampling 

assembly and returned to the laboratory. Initial pressure measurements (P,) were performed 48 to 72 hours 

later. This settling period allowed the samples to adjust to the laboratory environment and to achieve thermal 

equilibrium. Afterwards, research grade nitrogen (99.99995O;O purity / B6939) was added to the sample 

cylinders and final pressure readings (Pf) were performed to determine the volumetric expansion (dilution). 

The addition of nitrogen provided a positive pressure to the samplers and diluted any elevated moisture levels 

that could potentially interfere with the analysis results. The final results for each analyzed component are 

based on the raw data analysis corrected for the volumetric addition of nitrogen 

Total Hydrocarbon Analysis 

A Rosemount 400A Hydrocarbon analyzer was used to measure the concentration of hydrocarbons expressed 

as methane. The analyzer is designed for monitoring atmospheric air for low, level hydrocarbon contaminants 

and determining the hydrocarbon concentration of exhaust emissions from internal combustion engines. 

PrinciDle of Oneration 

The analyzer utilizes the flame ionization method of detection. The sensor is housed in a burner where a 

regulated flow of sample gas passes through a flame sustained by regulated flows of a fuel gas and air. Within 
the flame, the hydrocarbon components of the sample stream undergo an ionization that produces electrons and 

positive ions. Polarized electrodes inside the burner collect these ions, causing current to flow through an 

electronic measuring circuit. The ionization current is proportional to the amount of carbon atoms that enter the 

burner, and is therefore a measure of the concentration of total hydrocarbons in the sample. 

To ensure stable drift free operation, an internal temperature controller was used to maintain the analyzer 

interior at a constant 48 degrees C. This feature minimizes temperature dependent variations in electronic 

current measuring circuitry and adsorption / desorption equilibrium of background hydrocarbons within the 

internal flow system. 

The analyzer is equipped with a mixed fuel mixture (4040 hydrogen / 6090 helium) to minimize any error 

introduced by oxygen synergism and for improving the equality of response to the various species of 

hydrocarbons. 

Calibration 

Calibration consists of setting two points, a zero point and a span (upscale) point. 

A 4.9 ppm hydrocarbon gas standard (B6680 i AP) in nitrogen was used to span the analyzer. The calibration 

gas accuracy (i 290) was certified by a specialty gas supplier and is NIST traceable. The total hydrocarbon 

(THC) value is expressed as methane. Hydrocarbon free air (B77841 UC, THC <0.1 ppm) was used to adjust 

the background sensitivity (bias) of the analyzer. Thus with a hydrocarbon free gas flowing, the applied zero 

suppression compensates for the background current in the detector. 

Oualitv Control 

Zero and upscale calibration/verification checks were conducted both before (n=2) and after (n=4) each sample 

set in order to quantify calibration drift and measurement system bias. During these checks, the calibration 

gases were analyzed in the same manner as the plume samples. The maximum calibration drift of the span gas 

measurements was 2.0490. The zero bias remained unchanged. 

Long term instrument precision error based on measuring a NIST traceable gas standard over a 3-month period 

with over 20 sampling points (n=20) is less than 2 sigma or 3 YO of the actual reported value of the standard. 

Analvsis 

The analysis results are listed in tables 1, 2 and 3. 

Carbon Monoxide 

Determination of carbon monoxide in the samples uas performed using a Rosemount 880A Dual Beam 

Nondispersive Infrared Photometer. 

Princiole of Ooeration 

The photometer uses a selective filter to pass infrared radiation within a narrow range that matches the 

vibrational energy of the CO molecule. This configuration reduces stray radiation and allows only CO 

to be measured. While the absorption frequency depends on the molecular frequency, the absorption intensity 

is based on the amount of CO present. (See Principle of Operation in the “Other Targeted Emissions Section” 

for further discussion on the interaction of IR radiation with matter). 

Calibration 

Calibration consists of setting two points, a zero point and a span (upscale) point. 
An 84.7 ppm CO gas standard (B6294) in nitrogen was used to span the analyzer. The supplier’s reported 

accuracy for the NIST traceable standard is 2%. CO free nitrogen was used to adjust the background sensitivity 

(bias) of the analyzer. Thus with a CO free gas flowing. the applied zero suppression compensates for the 

background bias in the measurement system. 

Analvsis 

The analysis results are listed in tables I, 2 and 3. 

Oualitv Control 

Multipoint calibration error checks were conducted before and after sample testing by introducing 4 different 

calibration gases directly into the analyzer and recording responses. The maximum error was less than 3%. 

Otber Targeted Emissions 

Other targeted gasses were analyzed using a Bio Rad FTS-40 Fourier Transform Infrared Spectrometer using a 

multiple reflection gas cell with an optical path of 7.2 meters. Gasses measured were carbon dioxide, (CO,), 

nitrogen dioxide (NO?) and sulfur dioxide (SO, ). 

Princiuie of Oueration 

IR spectroscopy relies on the fact that all molecules except those with a homogeneous diatomic molecular 

structure (e.g. O,, N2. H2 ... etc.) and inert gasses (AI, He, Ne ... etc.) will react and absorb infrared radiation in a 

characteristic manner. The absorption causes changes in the molecular rotation and vibration. The pattern of 

absorption is determined by the physical properties of the molecule such as the number and type of atoms, the 

bond angles and bond strengths. This means that each component spectrum differs from all others and may be 

considered the molecular signature. By measuring and recording absorption strength as a function of 

wavelength over the infrared spectral region. the molecules present in the sample can be identified and 

quantified. 

In IR spectroscopy as applied here, two energy spectra have to be recorded, the spectrum of the measurement 

system without a sample (Io or background) and the spectrum of the gas cell containing the sample (l ). For the 

quantitative analyses the absorbance spectrum A, (1’1 

is calculated with a,(v)absorptivity of component i at wavenumber t-; b sample path length; ci concentration 

(partial pressure) of component i ; v wavenumber in cm- . 

I 

Equation I is known as Beer’s law. Beer’s law strictly holds only for isolated molecules, interacting with the 

radiation. This requirement is best met with gases at low partial pressures diluted in an nonabsorbing (inert) 

buffer (e.g. ppm concentrations of components in air mixed with nitrogen, as was done in this analysis. 

Absorptivity is measured by preparing or using calibration standards of components at known concentrations 

and measuring the spectra against a reference (background) gas that does not contain the components of 

interest. These calibration spectra are then used in the sampling analysis: (1 ) The compounds are detected by 

matching sample absorbance bands with the bands in the calibration - standard spectra and (2) concentrations 

are measured by comparing sample band intensities with the calibration intensity levels. 

Data Collection 

FTlR data collection was set for 4000-650 wavenunibers (cml), 16 co-added scans, Icm-’ resolution and a gain 

of 1.5 for the deuterated triglycine sulfate (DTGS) detector. Data was collected and stored as single beam 

spectra. 
Samding 

Samples and standard gasses were measured in a Model 6 IR absorption cell manufactured by Infrared 

Analysis Inc. The cell has an internal volume of 530 cc and is equipped with two stainless steel valves with a 

flow-through tube to allow monitoring of flowing samples. The IR beam is reflected within the gas cell by the 

three spherical mirrors, which gives multiple passing in increments of 4 passes. The 7.2-meter optical path was 

obtained by 48 passes with a base path of 0.15meters.The cell was set in the FTIR sample compartment; the 

compartment was sealed from the atmosphere by using a magnetized rubber gasket. 

Samples and calibration gasses were continuously drawn through the inlet of the gas cell and vented to the 

atmosphere. The sampling flow rate was - 500cc/min; the cell was purged with a minimum of 10 cell volumes 

of the calibration or sample gas before any spectral measurements were acquired. In between each sample and 

calibration run, the gas cell was purged with at least 5 cell volumes of nitrogen gas. 

Carbon Dioxide 

Calibration 

A comparison between the sample spectrum to research grade nitrogen (B6939) was performed to differentiate 

the relative spectral contribution from CO2. Four calibration standards were used to bracket the concentration 

range of the samples. In addition, a 425 ppm CO? calibration gas standard (B6294 / MG ) prepared by a 

specialty gas supplier was also used. The gas standard is a NlST traceable gravimetric standard and has a 

reported accuracy of 2%. 

A multicomponent calibration gas mixture (1920 ppm C@, 192 ppm NO? and 96.4 pprn SO,) in air (B7009) 

was used to prepare three calibration standards. The lower concentrations were obtained by diluting the 

calibration gas with research grade nitrogen (B6939). Measuring the absolute pressures with a digital pressure 

gage before and after the dilutions were made, the concentration values for the prepared standards were 

derived. The primary gas (NET traceable) standard was certified by the vendor and has a reported accuracy of 

2%. Linear regression files were constructed that included reference spectra representing the CO? standards. 

The correlation coefficient (r) for the calibration regression line is 0.99936. 

Analvsis 

The analysis results are listed in tables 1,2 and 3. 

Nitrogen dioxide and sulfur dioxide represent integrated samples that must be seen through water interference 

bands. Moisture possesses a feature rich and complicated infrared spectrum; the major moisture bands occur in 

two regions 4000-3400 cm-' and 2000-1300 cm'. Nitrogen dioxide shows two strong spectral regions near 

1600 cm'. Sulfur dioxide is centered at 1360cm'. 

Because of the strong interference from water vapor, a subtractive technique was employed to reconcile the 

sample spectrum for N@ and SO?. Screening tests were performed to make reasonable assumptions about the 

moisture absorption in the samples. Absorbance bands near 3700cm' were measured to determine the moisture 

absorption level. Several trial and error steps were attempted to prepare a suitable background by mixing 

humidified nitrogen in dry nitrogen. The goal was to develop a background (reference) that would subtract 80 

to 95% of the moisture bands from all of the samples. This range is optimal for seeing through the water bands 

without over subtraction. Complete or over subtraction of the spectrum can introduce spectral artifacts (e.g. 

introduction of noise, spike lines, etc.) and degrade spectral features (i.e., band shapes). The trade off is 

between sensitivity and risk of measuring a residual feature. 

After the moisture background is removed, the sample absorbance spectra are compared with the calibration 

spectra that were acquired with a dry nitrogen background. This process is similar in nature with the analytical 

method used to measure CO?. 
Cali bration 

A NlST traceable multicomponent calibration gas mixture (1920 ppm C02, 192 ppm NO2 and 96.4 ppm SO,) 

in air (B7009) was used to prepare four calibration standards. The lower concentrations were obtained by 

diluting the calibration gas with pure nitrogen. Linear regression files were constructed that included reference 

spectra representing the NO2 and SO2 standards. The correlation coefficients for NO2 and SO2 are 0.99610 

and 0.99299 respectively. 

Oualitv Control 

Interference responses were assessed and compensated prior to testing. The position and the slope of the 

spectral base line were monitored as successive spectra were collected. If the base line within a data set for a 

particular sample run began to deviate by more than 1090,a new background would be required. No deviations 

were encountered during the sample runs. 

The time domain detector response (interferogram) for the spectrometer remained stable within 2 sigma or 

10"0 over a 4-month period. 

Table 1 

Exhaust Summarv Results 

Test # THC c02 co NO2 so2 

3 1.8 ppm 158 1 ppm 40 PPm < 10ppm < IOppm 

4 1.7 pprn 2097 ppm 48 ppm < 10ppm < 10 ppm 

Table 2 

Plume Control Data 

Test # THC c02 co NO2 so2 

3 1.1 pprn 409 ppm < 1 PPm < 10ppm < 10 ppni 

4 1.9 ppm 4 1 Oppm < 1 PPm < 10ppm < 10ppm 

Table 3 

Atmospheric Control Data 

Test # THC c02 co NO2 so2 

3 1 .O ppm 429 pprn < 1 PPm < 10ppm < 10ppm 

4 I .9 ppm 40 1 ppm < 1 PPm < 10ppm < 10ppm 
Session F4 Erivironmeiitai Morittoriiig Methods 

//9 , '/' 

Overview of the City of Huntsville Air Pollution Control Program 

DANIEL SHEA 

Division of Natural Resources and Environmental Management, City of Huntsville 

P. 0. Box 308 

Huntsville, AL 35804 USA 

Phone: (256) 427-5750 

Fax: (256) 427-575 1 

E-mail:(dsheacl! ci .huntsvi 1le.al.w 1 

The City of Huntsville implements one of the two local air pollution control programs in the 

State of Alabama. Program implementation responsibilities include monitoring of ambient air 

quality, issuance of pollution control permits, inspection of point sources of emissions, and enforcement of Federal, State, and local air pollution control regulations. This session provides a brief 

overview of the air pollution control program in Huntsville. 

4TH CONFERENCE ON AEROSPACE hfATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc.nasa. gov 
Potential Effects on the Huntsville Area of Revised National Ambient Air Quality Standards 

for Ozone and Fine Particulate Matter 

DANIEL SHEA 

Division of Katural Resources and Environmental Management, City of Huntsville 

P. 0. Box 308 

Huntsville, AL 35804 USA 

Phone: (256) 427-5750 

FE-mail:ldshea~~~ci.hunts\rillc.al.us 1 

In 1997, EPA promulgated a more stringent Federal ozone standard and a new standard for 

very small particulate matter (PM, ,). Ozone concentrations in Huntsville over the past 3 years 

exceed the tighter ozone standard: Consequently, Huntsville and many other urban areas that are 

currently classified as “attainment” or “clean air” areas could be redesignated as “non-attainment 

areas.” (The U. S. Supreme Court will hear the case challenging the standards in November 2000). 

The ramifications of non-attainment designation will be briefly discussed. Preliminary data on fine 

particulate concentrations in the Huntsville airshed will also be summarized. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfc. nasa. gov 
Development of Lead Free Energy Absorber for Space Shuttle Blast Container 

Donald Balles, Thomas Ingram, Howard Novak, Albert Schricker (3 _- 

United Space Alliance 

8550 Astronaut Blvd. 

Cape Canaveral, FL 32920 

INTRODUCTION 

USA SRB Element is responsible for the assembly and refurbishment of the non-motor components of the 

SRB as part of the Space Shuttle Vehicle (SSV) system shown in Figures 1 and 2, and which is developed and 

managed by Marshall Space Flight Center (MSFC) in Huntsville, Alabama. Programs are underway to develop and 

evaluate environmentally acceptable materials for use on aerospace flight hardware in order to eliminate materials 

such as lead, and also; by effective re-design, provide lighter and more efficient systems. The SRE3 blast container 

(BC) is made primarily from Inconel 718 material that interfaces with either Inconel 718 or aluminum alloy 

materials. Four (4) Inconel 7 18 studs are used to holddown each of the SRBs to the Mobile Launch Platform 

(MLP), and each stud is held in place by an upper frangible nut and lower conventional nut. The additional 

assembly of pyrotechnic initiators and booster cartridges to the frangible nuts allow for detonation on command, 

which splits the nuts in halves and releases the SRBs and attached SS\'. The present BC along with a cast Lead 

liner / Shock absorber, contain the high energy pyrotechnic fragments as well as frangible nut elements after 

detonation, and protects the SSV from Foreign Object Damage (FOD). This paper discusses the benefits of 

replacing the cast lead liner with an open cell aluminum foam. 

DISCUSSION 

~ Pr li ' T ti 

oxides resulting from corrosion required special hazardous material handling and disposal. USA, Inc., is actively 

pursuing lead abatement programs, and the potential replacement of the lead BC liner followed those initiatives. A 

replacement material for the lead BC liner was sought by the Materials and Process Engineering Department. After 

an intensive search, the Energy Research and Generation, Inc. (ERG, Inc.) located in Oakland, California; was found 

to be a company that produces a unique type of open cell aluminum alloy foam designed specifically for energy 

absorption. The open cell aluminum foam feature allowed for a larger volume of material to be used in the confines 

of the BC without raising chamber pressure. Conventional materials such as honeycomb. and closed cell foams were 

found to be unacceptable. Mechanical Engineering contracted ERG, Inc. to provide flat test panels of various 

thickness and pore size / density configurations, in preparation for static drop testing. Full size frangible nuts were 

dropped from appropriate heights onto lead and aluminum foam targets below, thereby simulating relative impact 

energies of high velocity nut segments. It was found from these preliminary tests that the aluminum foam allowed 

for improved energy absorption over the present lead liner, and would potentially save 200 pounds at liftoff. As a 

result of these successful tests, USA SRB Element and NASA-MSFC decided to set-up a series of follow-on 

Proof-of Principle tests to determine the dynamic characteristics of the open cell aluminum foam under actual BC 

configuration. 

An incident had occurred where the lead liner used in the present BC had corroded, and the hazardous lead 

Proof-of Principle Tests 

A series of follow-on Proof-of-Principle tests were performed at the NASA-Kennedy Space Center (KSC) 

Launch Equipment Test facility (LETF), which simulated the SRB hold-down post, with actual BC hardware and 

pyrotechnics assembled. After BC assembly and calibration of instrumentation, the hardware was then test fired. 

Figures 3,4, 5, and 6 show the set-up required to perform the dynamic testing. Figures 7, 8,9, and 10 show the 

results after test firing. Post-test results revealed that the aluminum foam had excellent energy absorption 

characteristics, and performed as expected. In addition, operator satisfaction was high, in part caused by the ease of 

handling and installation of the light weight aluminum foam energy absorber, blast attenuator. A cohesive team 

composed of USA SRB Element Mechanical Engineering, Production Engineering and Operations, Launch Support 
Services, and Materials and Processes Engineering. as well as NASA-MSFC and NASA-KSC personnel and 

contractors took part in the successful test program. 

CONCLUSION 

Development and Proof-of Principle testing of an open cell aluminum foam energy absorber i blast attenuator 

has been completed. Data reduction continues, and the initial results were excellent. It was found that selected 

aluminum foam densities, and pore sizes worked better than others for the SRB frangible nut application. Excellent 

instrumentation allowed for accurate measurement of exit stud velocities, chamber pressures, and pyrotechnics firing 

order. Digital cameras, along with high speed, and conventional video taping recorded key elements of the test 

program, and helped with the interpretation of data. 

ACKNOWLEDGEMENTS 

The authors would like to thank the various USA departments both in Huntsville, Alabama and Kennedy Space 

Center, Florida for supporting and assisting in program management, production operations, logistics and testing. 

Many thanks to the NASA-MSFC SRB Program Office personnel who were supportive of this program, and 

NASA-KSC personnel and contractors, who performed the physical testing, and instrumentation at the LETF. 

Additional thanks are given to ERG, Inc. management and engineering personnel who helped make this test 

program a success. 

2 
SEPARATION MOTORS ( 

R EC OV ER Y S YS TE M ELECTRICAL SYST 

A lT AC H M ENT 

STRUCTURE 

TV C W--. AFT ATTACHMEN 

SYSTE 

SEPARATION 

Mm90 

SRM 

MOTORS (4) 

SRB SRB STAGE 

Figure 1. Space Shuttle Vehicle and Solid Rocket Booster 

Holddown 

Post 

er 

G9 

Q 

itward 

*/SRB 

tach 

Attach Strut 

0 0051 76 

Figure 2. Solid Rocket Booster with Blast Container 

3 
Figure 3. Holddown Stud, Frangible Nut, Booster Cartridges 

Figure 4. Aluminum Foam in Place 

4 
Figure 5. Top Section of Blast Container Assembled 

Figure 6. Final Assembly with Spring Housing 

5 
Figure 7. Post Test Frangible Nut Segments and Webs 

Figure 8. Post-Test Showing Foam Impact, Frangible Nut, etc. 

6 
Figure 9. Close-up Showing Foam Impact, Frangible Nut, Pyrotechnics 

Figure 10. Post-Test Showing Aluminum Foam Energy Absorber 

7 
I> f-’ Pmtei Swim I 

Polymer Matrix Composites (PMCs) Cryopipe for Rocket Engine Lines and Ducts 

DAVID BETTINGER 

The Technology Partnership 

8030 Coventry 

Grosse Ile, MI 48 138- 1 1 19 USA 

Phone: 734-675-8295 

Fax: 734-675-8296 

E-mail:l techpartk%home.com 1 

Alloy rocket engine ducts and lines have been targeted for conversion to lighter, polymer composites. The concern with polymer composites is assured performance for multiple reuse. The need is 

for stress control and polymer protection from LOX and LH,. A suite of seven polymer composite 

technologies is presented that make the component fabrication,-assembl y, and performance of polymer 

cryopipe practical and economical. Flanges are eliminated and expensive expansion alloy bellows are 

replaced by more efficient and lightweight components. 

These technologies use stress design to configure superior performance composites with 

existing space-qualified materials. The Air Force Research Laboratory and the Ballistic Missile 

Defense Organization have funded these developments. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:llampet.msfc.nasa,gov 
Nanotechnology Concepts at Marshall Space Flight Center - Engineering Directorate 

BILIYAR BHAT, Raj Kaul, Sandeep Shah. Gweneth Smithers, and Michael D. Watson 

Marshall Space Flight Center/ ED33 

Huntsville, Alabama 358 12 USA 

Phone: 256-544-2596 

Fax: 256-544-5877 

E-mail: Bi1iyar.B hat@msfc.nasa. eov 

Nanotechnology is the art and science of building materials and devices at the ultimate level 

of finesse: atom by atom. Our nation’s space program has need for miniaturization of components, 

minimization of weight, and maximization of performance, and nanotechnology will help us get 

there. MSFC’s Engineering Directorate is committed to developing nanotechnology that will enable 

MSFC missions in space transportation, space science, and space optics manufacturing. MSFC has a 

dedicated group of technologists who are currently developing high-payoff nanotechnology concepts. This poster presentation will outline some of the concepts being developed including, 

nanophase structural materials, carbon nanotube reinforced metal and polymer matrix composites, 

nanotube temperature sensors, and aerogels. The poster will outline these concepts and discuss 

associated technical challenges in turning these concepts into real components and systems. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:/larnpe t. msfc. nasa . gov 
n 

7 *' I' 

i ,* ~ ',,,/- = Postel Sewori 

Microstructure, Mechanical Properties, Hot-Die Forming, and Joining of 47XD Gamma TiAl 

Rolled Sheets 

/,' 1. ,' 

G. DAS I 

/' 

Pratt & Whitney 

P.O. Box 109600 

West Palm Beach, FL 3341 0-9600 USA 

Phone: 56 1-796-6744 

S. Draper, J.D. Whittenberger, and P.A. Bartolotta 

Glenn Research Center 

2 100 Brookpark Road 

Cleveland, OH 44 135-3 19 1 USA 

Phone: 2 16-433-3257 (Draper); 2 16-433-3 I96 (Whittenberger); 2 16-433-3338 (Bartolotta) 

Fax: 2 16-433-8000 

E-mail 

1 Paul.A.Bartolotta(iilerc.nasa.~ov ~ J 

The microstructure and mechanical properties, along with the hot-die forming and joining of 

Ti-47A1-2Nb-2Mn-0.8 vol% TiB, sheets (known as 47XD), produced by a low-cost rolling process, 

were evaluated. A near-gamma microstructure was obtained in the as-rolled condition. The microstructures of heat-treated sheets ranged from a recrystallized equiaxed near-gamma microstructure at 

1,200 to 1,3 10 "C, to a duplex microstructure at 1,350 "C, to a fully lamellar microstructure at 

1,376 "C. Tensile behavior was determined for unidirectionally rolled and cross-rolled sheets for 

room temperature (RT) to 8 16 "C. Yield stress decreased gradually with increasing deformation 

temperature up to 704 "C; above 704 "C, it declined rapidly. Ultimate tensile strength exhibited a 

gradual decrease up to 537 "C before peaking at 704 "C, followed by a rapid decline at 816 "C. The 

modulus showed a gradual decrease with temperature, reaching -72 percent of the RT value at 

8 16 "C. Strain to failure increased slowly from RT to 537 "C; between 537 "C and 704 "C, it exhibited a phenomenal increase, suggesting that the ductile-brittle transition temperature was below 

704 "C. Fracture mode changed from transgranular fracture at low temperature, to a mixture of 

transgranular and intergranular fracture at intermediate temperature, to ductile fracture at 8 16 "C, 

coupled with dynamic recrystallization at large strains. Creep rupture response was evaluated between 649 and 8 16 "C over the stress range of 69 to 276 MPa. Deformation parameters for steadystate creep rate and time-to-rupture were similar: activation energies of -350 kJ/mol and stress 

exponents of -4.5. Hot-die forming of sheets into corrugations was done at elevated temperatures in 

vacuum. The process parameters to join sheets by diffusion bonding and brazing with TiCuNi 70 

filler alloy were optimized for test coupons and successfully used to fabricate large truss-core and 

honeycomb structures. Nondestructive evaluation methods, e.g., ultrasonic C-scans and thermography along with metallography, were used to characterize bond quality. Microstructural evaluation 

during heat treatment, identification of phases at the braze/matrix interface, determination of shear 

strengths of brazed joints, and deformation mechanisms during tensile and creep processes will be 

discussed. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc.nasa.gov 
At Last, Something New! 

Cleaning without Chemistry, and Reusing the Waste Water! 

JOHN DURKEE 

Creative Enterprizes 

105 Anyway, Suite 209 

Lake Jackson, TX 77566 

Phone: 8 15-547-5650 x200 

Fax: 8 15-544-2287 

E-mail! jdurkee(cL:prectsioncleanlng.com J 

The poster describes research performed by Creative Enterprizes and a client firm to investigate management of industrial soils from their existence on parts to their disposal as a concentrate in 

water. These soils came from the manufacture of metal parts and include oils used for drawing, 

forming, cutting, grinding, lubricating, and honing; phosphate-based lubricants used in compression 

threading; dry lubricants, such as molybdenum disulfide; and other materials whose composition 

was unknown. 

The research produced the following knowledge: 

How these soils could be cleaned from parts using only ultrasonic energy and without use 

of cleaning chemistry 

How these soils could be made so as to not reinfect the parts in the cleaning bath 

The surprising effects of temperature and cleaning time on surface finish 

How to construct an evaporator for separation of the soils from water 

Specifications about recycle of the distilled and condensed liquid water. 

knowledge has been implemented in full-scale cleaning machines, which also will be described. 

The technology had been used at both high-precision and low-quality levels of cleaning. This 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfc. nasa. gov 
Polymer Matrix Composite (PMC) Ana.ag Processes for Lightweight Aluminum Matrix Composite (AMC) Structures 

BRIAN GORDON 1- a/ 

Touchstone Research Laboratory 

RDl Box IOOB 

The Millennium Center 

Triadelphia, WV 26059 USA 

Phone: 304-547-5800 

Fax: 304-547-4069 

E -m ai 1 : -1 

Next-generation hypersonic aircraft, reusable launch vehicles, and low-cost spacecraft require new materials to meet decreasing vehicle weights, increasing payload capacity, and dramatically lower operating costs. Materials that have improved specific strength and specific stiffness, 

especially at cryogenic and elevated temperatures, enable commercial and Government customers to 

meet these aggressive program goals by supporting development of stronger, lighter, and more 

thermally stable integrated components. Touchstone's Brazed Aluminum Matrix Composite (AMC) 

material has nearly twice the specific strength and specific stiffness of structural aluminum alloys 

and maintains these properties at higher temperatures than current aerospace alloys. When in situ 

brazed from thin tape, the manufacturing of large highly integrated structures is possible with minimal tooling. As such, this material and associated manufacturing process can serve as an enabling 

technology for many aircraft and spacecraft applications, including engine and thrust structures, feed 

lines and ducts, propellant tanks, and thermally stable satellite structures. This poster presentation 

discusses a new material and, more specifically, a new manufacturing system that enables development of high-performance aircraft and spacecraft components. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc.nasa,gov 
Postel Session 

Further Studies of Materials Compatibility in High-Test Hydrogen Peroxide /+ Lr ‘I’ . ,I 

RUDY GOSTOWSKI 

Department of Chemistry 

Austin Peay State University 

Box 4547 

Clarksville, TN 37044 USA 

Phone: 93 1-648-7624 

Fax: 93 1-648-5996 

E-mail 1 g- I 

Tom Owens 

Marshall Space Flight Center 

Huntsville. AL 358 12 USA 

Assessment of the compatibility of high-test hydrogen peroxide (HTP) with materials, in 

particular new materials such as composites, is critical to the development of new propulsion systems meeting requirements of reduced cost and environmental impact. While compatibility with 

HTP has been addressed previously, newer materials were not considered. The focus of this project 

was to develop a scheme for evaluation of HTP with all materials. In the previous summer, methods 

were developed for production of HTP on site, and preliminary steps were taken to evaluate materials. Methods investigated this summer have included accelerated aging by heating, coupled with 

assay of concentration and stabilization loss, observation of reactivity by means of Isothermal 

Microcalorimetry, and evaluation of changes to the materials by Short Beam Shear testing and by 

Photoacoustic-Fourier Transform Infrared Spectroscopy. Various metals, polymers, and composites 

were examined in this study. 

4TH CONFERENCE ON AEROSPACE bhTERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet.msfc. nasa.gov 
X-traktor: A Rookie Robot, Simple, Yet Complex, Impeccably Designed, A Very Innovative rP 

/, G,/ Multidisciplinary Engineering Masterpiece 

ARTHUR J. HENDERSON, JR. 

Marshall Space Flight Center/ED36 

Huntsville, AL 358 12 USA 

Phone: 256-544-2577 

Fax: 2 5 6-544-5 877 

arthur. henderson@,msfc.nasa.rrov 

FIRST is the acronym of For Inspiration and Recognition of Science and Technology. FIRST 

is a 50 1 .C.3 non-profit organization whose mission is to generate an interest in science and engineering among today’s young adults and youth. This mission is accomplished through a robot competition held annually in the spring of each year. NASA’s Marshall Space Flight Center, Education 

Programs Department, awarded a grant to Lee High School, the sole engineering magnet school in 

Huntsville, Alabama. MSFC awarded the grant in hopes of fulfilling its goal of giving back invaluable resources to its community and engineers, as well as educating tomorrow’s work force in the 

high-tech area of science and technology. 

Marshall engineers, Lee High School students and teachers, and a host of other volunteers 

and parents oficially initiated this robot design process and competitive strategic game plan. The 

FIRST Robotics Competition is a national engineering contest, which immerses high school students 

in the exciting world of science and engineering. Teaming with engineers from government agencies, businesses, and universities enables the students to learn about the engineering profession. The 

students and engineers have 6 weeks to work together to brainstorm, design, procure, construct, and 

test their robot. The team then competes in a spirited, “no-holds barred” tournament, complete with 

referees, other FIRST-designed robots, cheerleaders, and time clocks. 

The partnerships developed between schools, government agencies, businesses, and universities provide an exchange of resources and talent that build cooperation and expose students to new 

and rewarding career options. The result is a fun, exciting, and stimulating environment in which all 

participants discover the important connections between classroom experiences and real-world 

applications. 

traktor, the rookie robot, a manufacturing marvel and engineering achievement. 

This paper will highlight the story, engineering development, and evolutionary design of X4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfc.nasa.gov 
Laser Surface Modification of TiAl Intermetallics 

SHERMAN McELROY 

Department of Metallurgical and Materials Engineering 

The University of Alabama 

Tuscaloosa, AL 35487-0202 USA 

Ramana G. Reddy 

ACIPCO Professor 

Department of Metallurgical and Materials Engineering, 

The University ofAlabama 

Tuscaloosa, AL 35487-0202 USA 

Phone: 205-348-4246 

E-mai 1: I rreddv@ coe. en e. ua. edu I 

PosLer Session 

Using a Nd-YAG laser, laser processing of a series of Ti-A1 alloys, including pure Ti, pure 

Al, and Ti-A1 intermetallic compounds, has been studied. SEM, XPS, and optical microscopy were 

used to determine the surface morphological, chemical, and compositional characteristics of the laser 

processed samples. Analysis of results showed that cracks along grain boundaries caused by rapid 

heating and cooling of laser processing were the dominant characteristics of the surface morphologies of the laser processed samples. A1 content in the Ti-AI alloys plays a very important role in 

crack initiation and/or development. The more AI content in the samples, the more severe the cracks 

that developed after laser processing under the same conditions. 

These experiments were conducted at ambient conditions, resulting in surface oxidation 

layers being observed on the processed samples. XPS results indicate that the oxidation layer consists of adsorbed O,, A1,0,, TiO,, and TiO. In addition, A1 enrichment was found in the oxide film of 

TiAl as well as in the oxidation layers formed on the surfaces of TiAl and Ti,AI intermetallics that 

were processed by the laser; which is different from the reported results for traditional oxidation of 

TiAl at elevated temperature. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

h ttp://ampe t. ms fc. nasa . go v 
I I. Characterization of Ceramic Matrix Composite Combustor Components: 

Pre and Post Exposure 

G. OJARD 

United Technologies Research Center 

4 1 1 Silver Lane M/S 129-24 

East Hartford, CT 06 108 USA 

Phone: 860-6 10-70 13 

G. Linsey and J. Brennan 

United Technologies Research Center 

41 1 Silver Lane 

East Hartford, CT 06 108 USA 

E-mai I 1 OiardGC63utrc. utc. com I 

R. Naik, R. Cairo, R. Stephan, and J. Hornick 

Pratt & Whitney 

United Technologies Corporation 

400 Main Street 

East Hartford, CT 06 108 USA 

D. Brewer 

Glenn Research Center/MS 49 - 7 

2 1000 Brookpark Road 

Cleveland, OH 44 135 USA 

Phone: 2 16-433-3304 

Fax: 2 16-433-8000 

David.N.Brewer&,lerc.nasa.trov I 

The pursuit of lower emissions and higher performance from gas turbine engines requires the 

development of innovative concepts and the use of advanced materials for key engine components. 

One key engine component is the combustor, where innovative design and material improvements 

have the potential to lower emissions. Efforts to develop a High Speed Civil Transport with low 

emissions were focused on the evaluation of combustor concepts with liners fabricated from a 

ceramic matrix composite of silicon carbide fibers in a silicon carbide matrix (SiC/SiC). The evaluation of SiC/SiC composites progressed from simple coupons (to establish a first-order database and 

identify operant failure mechanisms and damage accumulation processes), to feature-based 

subelements (to assess fabricability and in sitti material response), to actual components (to assess 

structural integrity, dimensional, and compositional fidelity) tested under simulated engine conditions. 

fabrication issues is the evaluation of witness areas taken from fabricated components before testing 

the actual component. The witness material from these components allowed microstructural and 

mechanical testing to be performed and compared to the ideal, flat panel, conditions and data that are 

typical of basic characterization. This also allowed samples of similar design to be taken from 

components after 1 15 hours of combustion exposure. Testing consisted of tensile, double notch 

shear, ring burst, and thermal conductivity that sampled various regions of the components. The 

evaluation of the witness material allowed an understanding of the fabrication process, highlighting 

critical issues, in an early phase of the learning curve development of these configuration and material unique parts. Residual property testing, after exposure, showed if degradation of the material 

under actual service conditions was occurring. This paper will present the results of this critical 

testing. Evaluations that consider the degree of complexity of the fabricated part were established to 

relate in situ performance to that of flat panel based coupons. Nondestructive evaluation was used 

throughout the evaluation process. These results will also be discussed as an aid in understanding the 

test results. 

As in the case of all evolutionary material and process work, a key element to resolving 

4m CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet msfc. nasa.gov 
Automated Acquisition and Analvsis of Digital Radiographic Images 

Richard Poland. David lmmel, Boyd Howard 

Randy Singer, and Bob Moore 

Westinghouse Savannah River Company 

Savannah River Site 

Aiken, SC 29808 

(803) 725- 1998 

Kevwords 

Automated Image Analysis Digital Radiography X-ray 

Abstract 

Engineers at the Savannah River Technology Center have designed, built, and installed a fully automated 

small field-of-view, lens-coupled, digital radiography imaging system. The system is installed in one of the 

Savannah River Site s production facilities to be used for the evaluation of production components. 

Custom software routines developed for the system automatically acquire, enhance, and diagnostically 

evaluate critical geometric features of various components that have been captured radiographically. 

Resolution of the digital radiograms and accuracy of the acquired measurements approaches 0.001 . To 

date, there has been zero deviation in measurement repeatability. The automated image acquisition 

methodology will be discussed, unique enhancement algorithms will be explained, and the automated 

routines for measuring the critical component features will be presented. An additional feature discussed is 

the independent nature of the modular software components, which allows images to be automatically 

acquired. processed, and evaluated by the computer in the background, while the operator reviews other 

images on the monitor. 

System components were also a key in gaining the required image resolution. System factors such as 

scintillator selection, x-ray source energy, optical components and layout, as well as geometric unsharpness 

issues are considered in the paper. Finally the paper examines the numerous quality improvement factors 

and cost saving advantages that will be realized at the Savannah River Site due to the implementation of the 

Digital Imaging & Measurement System (DIMS). 

Backpround 

At the Savannah River Site, a U.S. Department of Energy 

facility, a joining technique called "pinch welding" is used 

to seal highly pressurized containers, known as reservoirs. 

Pinch welding seals the tube by applying high force and 

high current over time to heat a portion of the metal tube to 

the plastic state, deform the tube, and ultimately seal the 

tube. Figure 1. 

Because it is not possible to perform destructive testing of 

the pinch welds sealing the reservoirs, the qualification 

process begins with a weld development cycle where 

welding techniques are developed. Development welds are 

pressure tested and then destructively analyzed. At the 

completion of the weld development cycle the acceptable 

ranges for physical characteristics of the qualified weld are 

recorded and used as acceptance criteria for production 

welds. 

Pinch Weld 

Figure 1 
The key physical characteristics of these pinch welds are: 

- minimum wall thickness, 

- closure length, 

- electrode alignment. 

- tube alignment, and 

- open bore length. 

Each characteristic is described in detail below. 

Since the inception of the program, conventional film radiography has been the method utilized to obtain 

the physical characteristics of the pinch welds. Film radiography is an expensive and labor intensive 

method to perform this evaluation; however, quantitative data was a prerequisite prior to component 

acceptance. Until recently it was not possible to obtain the required radiographic sensitivity and spatial 

resolution required for these evaluations with digital radiography; however recent developments in large 

format CCD imaging cameras have made this project possible. The authors presented the customer an 

opportunity to instal I a state-of-the-art imaging device that would provide improvements in quality factors 

as well as yield considerable cost savings. The customer immediately supported a program to evaluate, 

develop, and install the high resolution imaging system. 

Svstem Overview 

The most important aspect of any automated digital radiography imaging system is x-ray image quality. 

Without a sharp, high resolution, high sensitivity radiographic image the accuracy of the automated 

measurements is very low, and may even be useless. Therefore considerable thought must be given to the 

selection of the x-ray components, the scintillating detector, and the optical components. Furthermore, the 

geometric unsharpness of the x-ray image must be considered to ensure that unsharpness is the lowest 

practicable value. (The lower the geometrical unsharpness, the better the image resolution.) 

Each of these factors was considered in the design and development of the system, and each will be 

discussed in this section. The following section discusses the software that processes the images created by 

the digital radiographic system. 

The system is a classical lens-coupled digital radiography system. The x-ray source is a 150 kVp, 3 mA 

Varian x-ray tube with a 1.5 mm spot size. The tube is housed in an interlocked x-ray cabinet with an 

imaging chamber 16 x 18 x 48 . A 2 x 2 x 6mm Industrial Quality, Inc. (IQ1)-401 terbium-doped 

high-density glass scintillator was selected to provide high resolution x-ray to light conversion. A 26 

source to scintillator distance, with an object to scintillator distance of one-eighth inch yields a geometric 

unsharpness of 0.29 mils, which is over three times sharper than the optical resolution of the system. 

The scintillator was placed slightly out of the center of the x-ray cone beam to allow room for all of the 

production components to fit in the cabinet. The plane of the scintillator was therefore tilted at a 5 degree 

angle toward the x-ray spot ensuring that the scintillator plane is perpendicular to the incident x-rays. This 

maintains the sharpest possible images for this geometrical arrangement. 

The optical imaging components are commercially available. A double turning mirror technique was used 

protect the CCD camera from high-intensity x-rays. The base optical breadboard table and the scintillator 

shelf are both lead-backed, and a riser connecting the two tables is also backed with lead. This totally 

shields the camera from direct exposure, thus nearly eliminating x-ray hits to the camera. The camera is a 

Photometrics Series 300 camera head with a KAF-4200 CCD. The KAF-4200 is a scientific grade 2,000 

pixel by 2.000 pixel imager selected specifically to provide 0.001 resolution with a 2 x 2 field-of-view. 

The calibrated optical resolution of the system is 0.927 mils, exceeding the stated customer requirement. 

The pinch weld essentially is in contact with the scintillator during image acquisition: therefore system 

geometric enlargement is one. 
Figirre 3 shows the measured 

Modulation Transfer Function (MTF). 

The system MTF is approximately 10 

Ip/mm at I 40/6 modulation. 

The system, as designed and installed, 

provides high spatial resolution images 

with high contrast sensitivity and a 

dynamic range far greater than that of 

conventional x-ray film. 

Automated Software Modules 

Once a high quality radiographic 

image was assured, the next step was 

to automate the acquisition and 

analysis of the image to provide 

accurate measurements of all pertinent 

pinch weld features. The software to 

accomplish these tasks has been 

Modulation Transfer Function 

lQh. 

"* I \ 

02 - 

01. 

"I 

1 234561 8 9 10 11 

Lplmm 

Figure 2 

designed in modular form, and will be described in detail for each of four modules. The four modules are 

Acquisition, Processing, Analysis, and Review. It is important to note that each module tuns independently 

and concurrently. After the image is acquired it is passed to the processing module, and from the 

processing module to the analysis module. Following the automated computer analysis, a qualified 

operator reviews the image and the measurement results and makes the final acceptkeject decision. 

Accluisition Module 

Prior to the evaluation of each group of reservoirs an ASTM penetrameter is imaged. The #5 penetrameter 

is placed on a 60 mil thick steel shim, imaged, and automatically evaluated by the software. The evaluation 

includes verification of the visibility of the IT hole, where the software evaluates the contrast change from 

the area surrounding the IT hole versus the contrast in the hole, and then evaluates the ratio versus a 

defined threshold. In addition. the dimensional verification of the pixel size is performed by tracing the 

penetrameter edges and measuring the diagonal dimensions of the penetrameter. These measurements are 

compared to National Institute of Standards and Technology (NIST) traceable values. If measurements are 

outside a pre-defined range of values, imaging tests are halted until the discrepancies are resolved. 

The operator then places the reservoir in a fixture that 

precisely places the pinch weld on the surface of the 

scintillator. The fixture, however, does not align the pinch 

weld parallel to the x-ray beam, and therefore the vertical 

pinch weld alignment is dependent on the operator. To 

ensure that each image is properly rotationally aligned, the 

software checks the alignment by evaluating the slope of the 

line profile at the center of the pinch. Essentially, the center 

of a pinch is similar to a rectangle, and for high resolution 

imaging of the pinch weld the rectangle must be precisely 

aligned with the path of the x-ray photons. Figure 3. If the 

rectangle is misaligned, the slope is less, and the operator is 

prompted to realign the pinch weld. 

Misaligned Aligned 

Figure 3 

This alignment procedure is performed on a low resolution postage stamp image that requires only 15 

seconds to acquire. This postage stamp image is also used to define the region of interest (ROI) that is 

required for the full resolution image. A very small amount of the 2 x 2 field-of-view (FOV) is required 

to image the tube, therefore to save data storage space only the required data is acquired and archived. This 

ROI is automatically detected and set by the software for each image (the ROI changes depending on the 

reservoir being evaluated). The software also extracts the pinch weld characteristics to determine which 

measurements will be performed in the analysis module. When the alignment is acceptable and the 
operator has verified proper ROI placement, the software begins a four minute exposure to acquire the full 

resolution image. Following the acquisition the image data is presented to the processing module for data 

processing. 

Processing Module 

De-fog 

A de-fogging algorithm is applied to the recently acquired pinch weld image. I 0, 

sequence. The de-fogging routine is used to remove effects of x-ray scatter and 

scintillator cross talk in the background image and the pinch weld image. Incident 

x-rays transmitted through the pinchweld generate the light in the scintillator that 

makes up the true image, however light is also generated by scattered x-rays. 

Further, the light in the transparent scintillator is transmitted in three dimensions, 

thus there is light cross talk for neighboring pixels within the scintillator. The 

closer the pixels are together, the greater the cross talk effect. The algorithm 

effectively removes both the scatter effect as well as a large portion of the cross 

talk effect. Figlire 4 shows the light generation components of a single 

scintillating pixel. The x-ray intensity transmitted through the subject, IT^, the xray scatter intensity incident upon the pixel, Is. and the cross talk light, Lx, all 

contribute to the total light, LT. detected by the camera at that pixel. 

and to the background image, Ig. that was acquired at the beginning of the run ITX 

Is 

LT 

Figure 4 

Lr = Lii, + LI~ + L.Y (Eq. 1) 

The desired light to be detected is LIT^, therefore the effects of all extraneous light must be removed from 

the data. This is accomplished using the equation 

where a function, F(i.j) scales the effect of the total light, LT, generated in neighboring pixels for a two 

dimensional surrounding area, i by j. F(ij) reduces the effect as the distance away from the pixel increases. 

The effects of the de-fog routine are tremendous. The edge definitions in the image are greatly enhanced 

due to the removal of the low frequency cross talk between neighboring pixels. Further, the contrast within 

the part is greatly increased. Figure 5 shows a comparison of the de-fogged image (bottom) versus the 

unprocessed image (top). Comparison of the contrast curves taken through the base, the pinch, and the tube 

show the increased contrast, the more defined edges, and the removal of the low frequency shadowing 

apparent near the edges of the tube. 

Position 1 

Figure 5 
Background and Dark Correction 

Beer s Law, 

15 IR=- , IO’lD 

(Eq. 3) 

is applied with the de-fogged background image, IB , and the dark image, ID. is the de-fogged full 

resolution pinch weld image. Beer s Law processing removes effects such as scintillator imperfections, 

optical aberrations, differences in pixel responsiveness, as well as other system abnormalities. IR is the 

resultant image data. 

De-speckle 

In the final step of the processing module, the de-speckle routine is applied to IR. The de-speckle routine is 

used to remove bad pixels or pixels that have been over-exposed due to a direct strike of an x-ray photon. 

The center pixel being evaluated, Pc, is compared to the eight surrounding pixels. If Pc is greater than the 

median surrounding pixel by a specified threshold, then Pc is replaced with that median pixel value. 

The processed image is now ready for automated analysis, and is placed in the analysis module s cue. 

Analysis Module 

Two analyses are performed on the radiographic data. The first is the quantitative measurements of the 

weld characteristics performed here in the Analysis Module. The second is actually completed by the 

operator in the Review Module. The operator visual verifies the automated measurements, and then 

visually examines the tube and the weld area for defects. 

The quantitative evaluations are automatically performed by the computer using custom 

developed software to define the characteristics and then measure the parameters. Four 

edges form the basis from which all measurements are determined. Figure 6. These 

edges are the left and right outer edges of the tube (red), and the inner edges on the 

reservoir side of the pinch weld and on the open side of the tube (green). 

The outer edges are determined by simple intensity thresholding. The edge is detected at 

a percentage level above the background contrast level. The inner edges are set by a 

slope threshold method. The slope threshold method detects an inner edge by first 

finding the zero-slope point for the tube s contrast curve. The inner edge is then set at a 

point a percentage below the zero slope on the row s contrast curve. Both threshold 

levels were set and verified by comparison to a calibrated standard tube. As stated 

previously, all edge detection levels have been set, calibrated, and verified numerous 

times. 

With the edges defined. all parametric measurements can be determined. There are 

presently seven parameters that are automatically determined by software. These are: 

Figure 6 

Minimirni Wall Thichness 

Minimum wall thickness is a critical process parameter that measures the thinnest portion of the tube wall 

on the reservoir side of the weld. The minimum wall thickness measurement must be greater than that 

specified for the reservoir being evaluated. The minimum wall thickness is determined by measuring the 

distance from every point on the reservoir inner wall edge to every point on each of the outer wall edges. 

The minimum wall thickness value is extracted from these measurements. 

Weld Closure Length 

The weld closure length is the minimum distance between the reservoir inner edge and the open-end inner 

edge. This measurement is obtained by determining the distance from every point on the reservoir inner 

edge to every point on the open-end inner edge, and then extracting the minimum value. This value 

therefore measures the minimum closure length of the pinch weld. The designer specifies the minimum 

length, and the measurement must be greater than the specification for the unit to be accepted. 
Electrode Alignnient 

The electrode alignment parameter measures the vertical alignment of the two electrodes used to make the 

weld. The alignment is critical because electrodes greater than the acceptable offset could cause a failure 

of the weld process resulting in considerable expense. The software calculates the offset by first generating 

a best-fit electrode from the pinch region of each outer edge. A line is then extended from the center of 

the electrode toward the center of the electrode s deformation in the pinch. The measurement is the 

offset measured at the vertical centerline of the pinch. 

Tube Alignment 

The tube alignment measurement is a measurement of the angular difference of the tube extending from the 

pinch to the reservoir versus the tube extending from the pinch to the open end. This parameter is 

determined by measuring the angular difference between projected centerlines generated from the outer 

edges above and below the pinch area. The customized software provides additional information, the tubecenterline offset value. The value is the offset of the centerlines when extended vertically to the center of 

the weld. 

Open Bore Length 

Open Bore Length is the location where the inner edge diameter drops below a threshold specified by the 

designer. This measurement is acquired by defining two value, the location where the tube extends from 

the reservoir base, and the point at which the reservoir inner edge separation (tube I.D.) drops below the 

threshold. 

Closirre Characteristics 

Closure Characteristics comprise two different measurements. There are two types of welds which must be 

evaluated by the system, and each has unique closure characteristics. The software automatically classifies 

the type of weld, then measures the closure diameter or the extrusion characteristics depending on the 

classification. 

Review Module 

The Review Module is somewhat of an extension of the Analysis Module, however the two run 

independently and therefore are considered separate modules. The Review Module is the most interactive 

module requiring the operator not only to verify the placement of the inner and outer edges. and the 

location of the measurements, but also perform a visual inspection of the radiographic image. 

Although the software has been thoroughly tested, the designers believed that at least initially the operator 

should be required to verify the placement of the edges and concur with the locations of the measurement 

values. Therefore, when the operator reviews an inspection, he is presented with the edge traces and each 

measurement visually. He either accepts the parameter or rejects the parameter with a comment. The 

parameter cannot be rejected without a comment explaining the concern. This allows the production 

engineer to key in on an anomaly during a subsequent examination. 

Operators performing the visual examinations must be minimally qualified as an ASNT limited level 11 xray technician. The operator is presented the processed image with mathematically generated IT holes 

placed on mathematically generated shims ranging from 30 mils to 150 mils. The virtual #5 penetrameter 

IT hole ensures the contrast sensitivity of the system. The extended dynamic range of the digital 

radiograph contains qualitative data throughout this large range of material thickness, unlike the 

conventional film method that was qualified for material thickness of only 50 to 78 mils. This alone is a 

leap forward in the qualitative evaluation of the weld area. which has a material thickness of greater than 

120 mils. 

The system allows the operator to vary the contrast levels, while viewing the pinch weld image and the 1T 

penetrameter swatches. The operator has the ability to reduce the display intensity range to produce a 

higher contrast in a limited range, or expand the range to produce an image similar to film. By ranging 

through the entire range of contrast levels the operator performs a very thorough evaluation of the tube as 
well as the weld area. Again, the operator is permitted to comment on anomalies. These comments are 

written to the file history and permanently stored with the image data. 

Results 

The installation of the automated digital radiography system provides many benefits to the customer in this 

application. The two key benefits are quality improvement and cost savings. Both are obviously critical 

factors when any organization attempts to justify the installation of a capital piece of equipment. 

Oualitv Improvements 

Calibrated Meastrrenients 

The Digital Imaging & Measurement System (DIMS) measurements are calibrated and traceable to NIST. 

On the other hand, there is no way to provide calibration of an operator subjectively determining the edges 

of the x-ray image, and then performing the measurement of the characteristics. 

Greater Measiirement Repeatabilihj 

The automated measurement algorithms provide zero variation in repeated measurements of the same 

image, and assure consistent evaluation of pinch welds throughout the life of the system. The conventional 

method of operator evaluation yielded greater than 25% variation in measurements from operator to 

operator for evaluations of the same radiographic images. 

More Thorough Radiographic Evaluation 

The DIMS provides code quality evaluation of the pinch weld radiograph throughout the required thickness 

range (Le. 0.030" - 0.130"). and allows the operator to change the contrast levels for a more through 

evaluation. The conventional method was set up to radiographically image the pinch weld to allow for 

evaluation of the pinch weld characteristics (0.050" - O.07Ot'), not for anomalies in the weld area (0.125"). 

Process Control Feedback 

The DIMS allows the operator to evaluate the image within minutes of the exposure, and provides the 

pinch weld characteristic measurements within minutes as well. If there is an unacceptable parameter, the 

process can be immediately evaluated and the problem corrected prior to additional reservoirs being sealed. 

This valuable feedback can typically take two weeks with the conventional film method currently in use. 

Cost Savings 

Reduced Labor Expenses 

Time is money, and labor hours consume budgets. This first installation of the DIMS will have a 

considerable effect on reducing the labor required for analysis of these welds, however the larger savings 

will be realized following the conversion of an additional three locations to digital systems. At that point, 

due to the automated nature of the system, full-time subcontract radiographers will no longer be required at 

the facility, saving well over a $100.000 per year. Further, due to the contaminated nature of the inspection 

location, no longer will Radiation Control specialists be required to bag-idbag-out film because the 

digital images will be digitally transmitted from the camera to the computer. In all, labor savings alone are 

estimated to total over $250.000. 

Reduced Film Evaluation Time 

Since the parameters are automatically measured by the software, no longer do operators have to 

laboriously determine several measurements for each pinch weld film, moving from two different 

measurement instruments. Due to the automated and modular nature of the software the operator can be 

performing other tasks while the computer is imaging, processing, and analyzing images. 

Reduced Film and Chemical Requirements 

A considerable cost savings will be realized due to the reduced need for x-ray film and development 

chemicals. Although this cost savings will not scale to the magnitude of the labor savings. this benefit is 

also important to reduce resource consumption and reduce waste streams, 
Reduced Number of Rejected Units 

If a parameter is outside of an acceptable range, the reservoir is rejected and the unit must be re-worked. 

This is a very timely and costly process extending into the hundreds of thousands of dollars. The 

immediate feedback of the DIMS will reduce the number of re-work units, thus providing considerable 

cost savings as well as process quality improvement. 

Additional Benefits 

Digital Nuture 

There are obvious advantages of the system being digital, such as the data being stored on compact storage 

disks, replacing film and paper storage. An additional feature of digital storage is that the digital data never 

degrades, unlike film which will fade over time. Further, the digital images and measurement data may be 

quickly shared electronically for evaluation and discussion. 

Rcdirccd II ask Streams 

As mentioned above, the complete installation of the DIMS will eliminate the bag-out scenario and 

reduce that waste stream, as well as the reduction of waste film and development chemicals. 

Summary 

Throughout the development of the DIMS several advances in digital radiography techniques have been 

developed. A key breakthrough is the de-fogging algorithm that removes cross talk effects that have 

plagued glass scintillators, thus increasing attainable resolution. The display of the virtual penetrameter 

to ensure equivalency to film is another development in the presentation of digital x-ray images. This 

virtual penny display allows for code-quality examination of the entire dynamic range of the digital data. 

In conclusion, the pinch weld image acquisition and analysis system is a production-ready system with 

customized. automated software that controls the imaging and analysis process through the complete 

imaging cycle. The system delivers accurate, repeatable. digital results by eliminating operator bias in the 

imaging process as well as the analysis processes. 
Fabrication of Low-Cost, High-Temperature Composites for Rocket Propulsion Systems 

MARK J. RIGALI, Manish Sutaria, Anthony C. Mulligan, and Ranji Vaidyanathan ~ 

Advanced Ceramics Research, Inc. 

3292 E. Hemisphere Loop 

Tucson, AZ 85706 USA 

Phone: 520-573-6300 

Fax: 520-5 73-2057 

E-mail1 r.vaidvanathanO,acrtucson.com 1 

Advanced Ceramics Research, Inc., (ACR) is currently developing two low-cost, flexible 

manufacturing processes to produce high-temperature composites with zirconium carbide (ZrC) 

matrices for use in current and future NASA and Department of Defense (DoD) propulsion applications. As a monolithic material, ZrC exhibits corrosion and ablation resistance at high temperatures. 

ZrC, however, does not possess the toughness and thermal shock resistance necessary to survive in 

many propulsion system applications. To enhance its toughness and thermal shock resistance, ACR 

is fabricating ZrC-based composites using two novel and low-cost composite fabrication techniques 

called Fibrous Monolith (FM) processing and Continuous Composite Co-extrusion (C') processing. 

structural ceramics. They exhibit mechanical properties similar to fiber composites or laminate 

structures, including very high fracture energies, damage tolerance, and graceful failure. Since they 

are monolithic powder-based composites, however, they can be manufactured by conventional 

powder processing techniques using inexpensive raw materials. In the FM process, an interpenetrating microstructure of elongated polycrystalline 'cells' of the matrix material (in this case, the hightemperature carbides and diborides) are separated and encapsulated by thin cell boundaries of a low 

shear strength material (BN, graphite, etc.) or a ductile material (W, Re, Mo, etc.) This interpenetrating microstructure imparts the necessary toughness and thermal shock resistance to the composite 

that is lacking in the monolithic carbides. The weak interface composites and many of the ductile 

interface composites exhibit fracture behavior similar to fiber reinforced ceramic composites, including the ability to fail in a non-catastrophic manner 

produce continuous fiber reinforced composites. In the C3 process, carbon fiber tow is passed 

through the center of a ceramic powder/thermoplastic binder feedstock during melt extrusion to 

produce a 'green' filament. The resulting filament is flexible, robust, and easily handled using 

traditional processing methods, i.e., hand lay-up or filament winding; it is then pyrolyzed and hot 

pressed to produce dense parts. Although it was originally developed for the fabrication of ZrC and 

HfC carbon fiber composites for propulsion systems, the C' process promises to be applicable to the 

fabrication of a wide variety of other fiber-reinforced composites. 

This paper highlights the mechanical and physical properties of the ZrC-based composites 

currently under development by ACR using the both the FM and C3 fabrication processes. In addition, ACR is applying solid freeform fabrication (SFF) techniques to the production of these composite components currently being developed for several high-temperature DoD and NASA applications, including hot gas valves components, nozzles, thrust cells, and leading edges. 

Fibrous Monolith processed composites are a new class of low-cost, bi- and multi-component 

C', based on the Fibrous Monolith processing technology, utilizes an innovative approach to 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

hftp:/lampet.msfe.nasa.gov 
Electro Spark Alloy Processing for Aerospace Components 

MICHAEL RILEY 

Surface Treatment Technologies, Inc. 

8600 Drumwood Road 

Towson, MD 2 1286 USA 

Phone: 4 10-828-59 14 

Fax: 4 10-828- 1993 

E-mail: /mriley@,stt-inc.com I 

Surface Treatment Technologies has employed the Electro Spark Alloying (ESA) process for 

. 

The ESA process is a low-voltage arc welding technique in which an electrode deposits itself 

Nano-grain structure 

Nano-grain coatings of metal, intermetallic, and ceramic layers have been formed on test 

three NASA hardware needs: 

Repair of pitting corrosion on Solid Rocket Booster (SRB) O-ring grooves 

Repair of 24K gold coatings on Space Shuttle engine components 

Formation of bum-resistant alloy coatings on oxygen delivery hardware. 

on a conductive metal or ceramic substrate. The resultant coating has the following key features: 

Full metallurgical bond to the substrate 

No heat-affected zone in the base alloy 

Capability of coating inside diameters and non-line-of-sight geometries. 

specimens and subjected to relevant customer tests. Process information, metallurgical data, and test 

results from Phase I Small Business Innovation Research and NASA-related contracts will be presented. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http:llampet. msfc. nasa.gov 
Postcr Sessm 

Detection, Identification, and Quantification of Surface Contamination 

M. MARTIN SZCZESNIAK, Michael Beecroft, and Phillip Mattison {' 

I 

Surface Optics Corporation 

11 555 Rancho Bernard0 Road 

San Diego, CA 92 127 

Phone: 858-675-7404 

Fax: 858-675-2028 

Even low levels of surface contamination can affect in a negative way physical properties of 

metal surfaces: adhesion, bonding, heat radiation. Detection of low contamination levels (below 1 

microgradcm') on large surfaces (more than 1 inch in diameter) is a challenge. A portable infrared 

reflectometer is applied to this application with a high level of success. The reflectometer covers the 

spectral region required to detect both the hydrocarbons and silicones. It is achieved with a Fourier 

Transform Infrared spectrometer. The sampling interface depends on the finish of the studied surface. The highly finished mirror-like surfaces can be analyzed with a specular reflectance accessory. 

The rough surfaces (grit-blasted) can be analyzed with the diffuse reflectance accessory. The reflectometer measures infrared spectra of suspected areas. The measurable infrared spectrum is an 

indication of surface contamination. The infrared spectra can be searched against standard or custom 

spectral libraries, which results in contaminant identification. The level of contamination can be 

predicted by applying calibration curves or chemometrics, PLS, CLS. The surface, which can not be 

accessed directly, can be swabbed and the residue extracted into the VSphereTM. The VSphereTM is a 

patented accessory for the detection of nonvolatile residues. The minimum detection limits will be 

presented and discussed. 

4TH CONFERENCE ON AEROSPACE MATERIALS, PROCESSES, AND ENVIRONMENTAL TECHNOLOGY 

http://ampet. msfc. nasa.gov 
Quadruple Lap Shear Processing Evaluation 

,* / /i Tony N. Thornton 

Thiokol Propulsion 

SEHO 

P. 0. Box, 707, M/S 200 

Brigham City, UT 84302 

ABSTRACT 

The Thiokol, Science and Engineering Huntsville Operations (SEHO) Laboratory 

has previously experienced significant levels of variation in testing Quadruple 

Lap Shear (QLS) specimens. The QLS test is used at Thiokol / Utah for the 

qualification of Reusable Solid Rocket Motor (RSRM) nozzle flex bearing 

materials. A test was conducted to verify that process changes instituted by 

SEHO personnel effectively reduced variability, even with normal processing 

variables introduced. A test matrix was designed to progress in a series of steps; 

the first establishing a baseline, then introducing additional solvents or other 

variables. Variables included normal test plan delay times, pre-bond solvent 

hand-wipes and contaminants. Each condition tested utilized standard QLS 

hardware bonded with natural rubber, two separate technicians and three 

replicates. This paper will report the results and conclusions of this investigation. 

INTRODUCTION 

In 1993, the first QLS specimens were processed at SEHO during the downselection of aqueous cleaners for the replacement of 1,1,1 trichloroethane (TCA) 

in vapor-degreasers. Over the course of a year, specimens were processed on 

five different occasions, each producing unacceptable and unexplainable levels 

of variation. A team comprised of NASA, SEHO and Utah S&E was established 

to investigate the problem, but was dissolved when all possible efforts to render a 

solution were exhausted. The QLS portion of the test was then transferred to 

Utah. 

QLS testing at SEHO was revived again in the latter part of 1999, with changes 

to processing methodology that provided ample positive results to proceed with a 

formal Engineering Test Plan. These changes included the use of polyurethane 

foam brushes for primer, adhesive and tackifier applications instead of nylon 

bristle brushes, shimming the QLS molds instead of the cure press and changing 

the cure cycle to include a temperature ramp before initiating the cure cycle. 

0 2000 Thiokol Propulsion, a Division of Cordant Technologies Inc. 
The primary objective of this test was to demonstrate QLS specimens could be 

successfully bonded at the SEHO lab after implementing the changes to our 

processing methodology. The secondary objective was to introduce typical 

variables and contaminants that may be encountered during hardware 

processing to demonstrate that the method was robust. 

The test was designed to progress in a series of steps, each step introducing 

another variable. First, using standard QLS hardware and specified processing 

protocol, three replicates of four QLS specimens were processed at different 

times by two separate technicians. The second iteration incorporated normal test 

plan delay times for contamination purposes, with no contaminant. The third 

iteration incorporated normal test plan delay times that are encountered for 

contamination purposes, with no contaminant and a pre-bond hand wipe with 

TCA. The fourth and fifth iterations introduced the contaminants Conoco HD-28 

grease and PermacelB tape adhesive respectively, delay time'!! and a pre-bond 

hand-wipe cleaning with TCA. The test matrix is shown below in Table I. 

Table I: Test Matrix 

2 
TESTING 

The test specimens consisted of steel QLS plates bonded together with natural 

rubber using a primer (ChemlokB 205); a rubber-to-metal adhesive (ChemlokB 

220); and a tackifier (Tycement). A typical QLS specimen is illustrated below in 

Figure I. 

Figure I: QLS Specimen 

Steel Plates 

Natural Rubber 

All QLS hardware utilized for this test was measured to the nearest .001" and 

placed in sets not varying more than .002". All bonding surfaces were grit 

blasted and spray-in-air cleaned after which they received a final grit blast before 

processing. Baseline specimens were bonded the same day as the final grit 

blast. Normal time delay specimens were allowed to sit undisturbed for 36-48 

hours after the final grit blast prior to bonding. TCA hand-wipe specimens were 

allowed to sit undisturbed for 36-48 hours after which they were wiped using the 

double hand-wipe method prior to bonding. Specimens contaminated with HD-2 

grease and yellow tape adhesive were placed in an oven for 24 hours at IOOOF, 

allowed to sit at ambient for an additional 12-24 hours then cleaned with TCA 

using the double hand-wipe method prior to bonding. 

Test specimens were cured for 2 hours at 300°F then allowed to condition for a 

minimum of 24 hours at ambient. Mechanical testing was conducted at ambient 

laboratory temperature and humidity using a test rate of 0.5 inches per minute. 

3 
RESULTS 

18 

16 - 

Average results for the Baseline specimens exceeded the 500 psi minimum 

shear strength requirement for this bondline by 35%. Results also yielded a 73% 

increase over specimens tested previously at SEHO and surpassed our parent 

lab's historic average by 15%. Shear results are shown in Figure 11. 

Figure 11: Baseline Shear Comparison 

800 

700 

600 

i 

$ 500 

r 

VI 400 

E 300 

3 200 

100 

0 

.- 

U 

.- - U 

Parent Lab Database SEHO (Previous) SEHO (Current) 

Results also denote a significant decrease in the Coefficient of Variance (CV) 

compared to previous SEHO testing and our parent lab's historic database as 

shown in Figure 111. 

Figure 111: Baseline CV Comparison 

Parent Lab Database SEHO (Previous) SEHO (Current) 

4 
Figure IV summarizes average shear strength results obtained from the test 

conditions that were shown in Table I. As with the Baseline specimens, all 

conditions tested significantly exceeded the minimum shear strength 

requirements for this bondline. 

20 

18 - 

16 

14 

2 12 

d 10- 

8 

Figure IV: SEHO Current Shear Results 

800 

-. 

-. 

-. 

. "" 

.- 

UI 

a 600 

i 

500 

L 

400 v) 

300 

f! 

3 200 

100 

n 

Y 

.- 

Baseline Normal Time- TCA Hand-Wipe HD-2 Grease Permacel Tape 

Contaminated 

Delay Contaminated Adhesive 

Process Variables 

Figure V summarizes average CV results obtained from this testing. As with the 

Baseline specimens, all conditions tested displayed minimal percentages of 

variation. 

Figure V: SEHO Current CV Results 

Baseline Normal Time- TCA Hand-Wipe HD-2 Grease Permacel Tape 

Contaminated 

Delay Contaminated Adhesive 

Process Variables 

5 
The program objectives were accomplished demonstrating that SEHO can 

reliably process QLS specimens without unexplainable variation in test results. 

Successful QLS processing can be achieved with or without intentional test 

variables introduced. Current testing demonstrated shear strengths that 

significantly exceeded minimum requirements. 

The success of this program can be attributed to changes made to processing 

methodology that included: 

Brushes 

0 Nylon bristle brushes previously used for application of the primer, 

adhesive and tackifier were found to be conducive to introducing 

“streaks” on the surface that seemed to be causing adhesive bond 

failure 

0 Polyurethane foam brushes currently used produce a thin, uniform 

coating that eliminates streaks and significantly reduces adhesive 

bond failure 

0 QLS mold pre-heat 

0 The previous method of shimming the cure press did not allow top 

platen to contact the QLS molds during pre-heat 

0 The current method of shimming the molds allows maximum heat 

transfer from the top platen directly to the molds 

Cure cycle: 

The cure cycle previously used did not allow time for the press to 

reach cure temperature before initiating the 2 hour cure 

Cure cycle currently used incorporates a ramp to cure temperature 

before the 2 hour cure cycle is initiated 

6 
ACKNOWLEDGEMENTS 

This effort was accomplished as the result of a collaboration of many individuals. 

The following people played significant roles in this work: Richard Boothe, Troy 

Daugette, Charlie Davis, Jill Keen, Ken Peacock and the SEHO Test Lab. 

7 
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Proceedings of the 4th Conference on Aerospace Materials, 

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Proceedings of a conference held in Huntsville, AL, September 18-20, 2000. 

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The next millennium challenges us to produce innovative materials, processes, manufacturing, and 

environmental technologies that meet low-cost aerospace transportation needs while maintaining U.S. 

leadership. The pursuit of advanced aerospace materials, manufacturing processes, and environmental 

technologies supports the development of safer, operational, next-generation, reusable, and expendable 

aeronautical and space vehicle systems. The Aerospace Materials, Processes, and Environmental 

Technology Conference (AMPET) provided a forum for manufacturing, environmental, materials, and 

processes engineers, scientists, and managers to describe, review, and critically assess advances in these 

key technology areas. 

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