November 2011 

NASA/CR—2011-217309

PRSEUS Acoustic Panel Fabrication 

Alex Velicki, Nicolette P.Yovanof, Jaime Baraja, Gopal Mathur, Patrick Thrash, 

and Robert Pickell 

The Boeing Company, Huntington Beach, California 
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Hampton, Virginia 23681-2199 under Contract NNL10AA05B

 

November 2011 

NASA/CR—2011-217309

PRSEUS Acoustic Panel Fabrication 

Alex Velicki, Nicolette P.Yovanof, Jaime Baraja, Gopal Mathur, Patrick Thrash, 

and Robert Pickell 

The Boeing Company, Huntington Beach, California 
Available from: 

NASA Center for AeroSpace Information 

7115 Standard Drive 

Hanover, MD 21076-1320 

443-757-5802 

The use of trademarks or names of manufacturers in this report is for accurate reporting and does not 

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National Aeronautics and Space Administration. 
iii



This document summarizes the work performed by Boeing Research & Technology, Huntington 

Beach, California under the Environmentally Responsible Aviation (ERA) Project to explore and 

document the feasibility, benefits, and technical risk of advanced vehicle configurations and 

enabling technologies that will reduce the impact of aviation on the environment. This report 

documents the work that was performed under a task order contract to design and fabricate a

PRSEUS acoustic test panel. The panel was delivered to NASA-LaRC in April for final 

specimen preparation and acoustic testing in the Structural Acoustics Loads and Transmission 

(SALT) test facility. The ultimate goal of this activity is to assess the sound transmission 

characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body (HWB) 

operating environment. 

The NASA technical monitor was Richard Silcox, Chief Engineer for Acoustics, Research 

Directorate, NASA-LaRC. Major contributions to the written report were made by Mr. Albert 

Allen of the NASA Structural Acoustics Branch by providing the testing and advanced concepts 

write-ups. 

This document was written and contributed to by the following Boeing personnel: 

Mr. Alex Velicki Principal Investigator

Ms. Nicolette Yovanof Program Manager

Mr. Jaime Baraja Structural Design Engineering 

Mr. Gopal Mathur Acoustic Design Engineering 

Mr. Patrick Thrash Manufacturing Engineering

Mr. Robert Pickell Manufacturing Engineering
iv

	

		

Introduction ..................................................................................................................................... 1

1.0 Baseline Specimen Design .................................................................................................. 3

1.1 Boundary Layer Calculation ........................................................................................... 3

1.2 Acoustic Testing Approach ............................................................................................. 4

1.3 PRSEUS Panel Design and Fabrication Background ..................................................... 5

1.4 Specimen Design ............................................................................................................ 6

1.5 Panel Material Properties .............................................................................................. 10

2.0 Panel Fabrication .............................................................................................................. 15

2.1 Preform Assembly and Stitching .................................................................................. 15

2.2 Resin Infusion and Cure................................................................................................ 17

2.3 Edge Trim Machining ................................................................................................... 19

2.4 Panel Dimensional Check ............................................................................................. 20

2.5 Panel Adaptor Frame and Shim Fabrication ................................................................. 21

3.0 Test Specification Preparation .......................................................................................... 25

3.1 Freely Hung Structural Vibration Testing .................................................................... 25

3.2 In-situ Vibroacoustic Testing ........................................................................................ 28

3.3 Testing Responsibilities and Contact Information ........................................................ 29

4.0 Advanced Concept Development ..................................................................................... 30

4.1 Possible Areas of Study ................................................................................................ 30

4.2 Proposed Future Work .................................................................................................. 32

5.0 Summary ........................................................................................................................... 33

Appendix – Specimen Design Drawings (5 pages) ...................................................................... 35
v

	

Figure 1. Overview of HWB PRSEUS Airframe Development Testing ........................................ 1

Figure 2. Baseline Schedule and Work Statement .......................................................................... 2

Figure 3. Aerodynamic BWB Baseline Configuration ................................................................... 3

Figure 4. Boundary Layer Thickness for the BWB-450-1L Configuration .................................... 4

Figure 5. Acoustic Testing Approach in SALT Facility ................................................................. 5

Figure 6. Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) .................................... 5

Figure 7. Stitched Dry Fabric Used to Create Self-Supporting Preform ........................................ 6

Figure 8. Resin Infusion Approach and Cured Panel ..................................................................... 6

Figure 9. PRSEUS Panel Materials Used for Multi-Bay Box Specimen ....................................... 7

Figure 10. Test Panel Stringer and Frame Layout .......................................................................... 7

Figure 11. Stringer Wrap Geometry ............................................................................................... 8

Figure 12. Nominal Panel Edge Geometry ..................................................................................... 8

Figure 13. Nominal Frame Geometry ............................................................................................. 9

Figure 14. Nominal Stitch Seam Locations in Frames and Stringers ............................................. 9

Figure 15. Warp-Knit Fabric Arrangement .................................................................................. 10

Figure 16. Stringer and Frame Details Inserted into Preform ....................................................... 15

Figure 17. Doubler and Skin Details Added Prior to Stitching .................................................... 16

Figure 18. Single-sided Stitching Technique (Different Panel Shown) ....................................... 16

Figure 19. Acoustic Panel During Resin Infusion ........................................................................ 17

Figure 20. Completed Resin Infusion Operation .......................................................................... 18

Figure 21. Cured Specimen Blank Prior to Edge Trim ................................................................. 18

Figure 22. Close-up of Cured IML Surface .................................................................................. 19

Figure 23. Cured Specimen OML Surface ................................................................................... 19

Figure 24. Specimen Edge Trim Machining at Vendor Facility ................................................... 20

Figure 25. Panel OML Surface Displacement (inches) – Frames are Vertical ............................. 20

Figure 26. Adaptor Frame Detail .................................................................................................. 21

Figure 27. Adaptor Frame Geometry ............................................................................................ 22

Figure 28. Adaptor Frame Cross Section Geometry ..................................................................... 22

Figure 29. Layer Shim Map .......................................................................................................... 23

Figure 30. Shim Fabrication ......................................................................................................... 24

Figure 31. SALT Facitily Layout.................................................................................................. 26

Figure 32. PRSEUS Test Panel FEM with Adaptor Frame (235,914 DoFs) ................................ 27

Figure 33. Statistical Energy Analysis (SEA) Model of PRSEUS Test Panel ............................. 28

Figure 34. Candidate Integral Acoustic Improvements Under Consideration .............................. 30

Figure 35. Specimen Drawing Sheet 1 of 5 .................................................................................. 35

Figure 36. Specimen Drawing Sheet 2 of 5 .................................................................................. 36

Figure 37. Specimen Drawing Sheet 3 of 5 .................................................................................. 37

Figure 38. Specimen Drawing Sheet 4 of 5 .................................................................................. 38

Figure 39. Specimen Drawing Sheet 5 of 5 .................................................................................. 39
vi 

		


Table 1. Panel Fabric Specifications ............................................................................................. 10

Table 2. Warp-Knit Fabric Stacking Architecture ........................................................................ 11

Table 3. Laminate Stiffness .......................................................................................................... 11

Table 4. Laminate Unnotched Strengths [ksi] .............................................................................. 11

Table 5. Laminate CAI Strength for Exterior Members (100 ft-lb impact).................................. 12

Table 6. Laminate CAI Strength for Interior Members (20 ft-lb impact) ..................................... 12

Table 7. Rohacell Minimum Properties ........................................................................................ 12

Table 8. Rod Mechanical Properties ............................................................................................. 13

Table 9. Environmental Correction Ratios ................................................................................... 14

Table 10. Frame Component Material Properties ......................................................................... 23
vii 





BHD Bulkhead 

BWB Blended Wing Body 

CAI Compression After Impact 

CD Cold Dry 

CAPRI Controlled Atmospheric Pressure Resin Infusion 

CG Center of Gravity

COLTS Combined Loads Test System 

D&DT Durability and Damage Tolerance

FAR Federal Aviation Regulations 

FEM Finite Element Model

H/W Hot/Wet

HWB Hybrid Wing Body 

ICD Interface Control Drawing 

IML Inner Moldline 

IRAD Independent Research and Development

KEAS Knots Equivalent Airspeed 

KIPS Thousand Pounds 

KSI Thousand Pounds Per Square Inch 

MLG Main Landing Gear

MTOGW Maximum Takeoff Gross Weight 

MZFW Maximum Zero Fuel Weight

NDE Nondestructive Evaluation

NDI Nondestructive Inspection

Nx Axial Load in x-direction

Nxy Shear Load in xy-plane

Ny Axial Load in y-direction

OB Outboard 

OEW Operator Empty Weight 

OML Outer Moldline 

OHC Open Hole Compression 

OML Outer Moldline 

PRSEUS Pultruded Rod Stitched Efficient Unitized Structure

PSI Pounds per Square Inch 

SALT Structural Acoustics Loads and Transmission 

SEA Statistical Energy Analysis

SQ-IN Square Inches

TBL Turbulent Boundary Layer 

VARTM Vacuum-Assisted Resin Transfer Molding
PRSEUS Acoustic Panel Fabrication

1

	
	

NASA has created the Environmentally Responsible Aviation (ERA) Project to explore and 

document the feasibility, benefits, and technical risk of advanced vehicle configurations and 

enabling technologies that will reduce the impact of aviation on the environment. A critical 

aspect of this pursuit is the development of a lighter, more robust airframe that will enable the 

introduction of unconventional aircraft configurations that have higher lift to drag ratios, reduced 

drag, and lower community noise. The primary structural concept being developed under the 

ERA program in the Airframe Technology element is the Pultruded Rod Stitched Efficient 

Unitized Structure (PRSEUS) structural concept.

To improve structural performance and reduce fabrication costs beyond those achieved using 

conventional state-of-the-art composite fabrication techniques, the PRSEUS panel construction 

utilizes an integral one-piece design approach with cocured details that are joined together by

stitching to provide exceptional out-of-plane strength and improved damage tolerance. Although 

the resulting structure has been shown to meet the demanding out-of-plane loading requirements 

of the Hybrid Wing Body (HWB) flat-sided pressure cabin design, there are concerns that the 

lighter, stiffer, cocured details of the PRSEUS structure could have higher sound transmission 

levels than those exhibited by conventional build-up structures flying today.

To address these concerns, and to establish a baseline set of acoustic characteristics for a

PRSEUS panel, an acoustic test panel was designed, fabricated, and then delivered to 

NASA-LaRC for testing. The test panel design was based on the Hybrid Wing Body (HWB) 

minimum-gauge pressure cabin panel geometry established during the NASA NRA Phase I trade 

studies (Ref 1) and then structurally tested during the Phase II portion (Ref 2) of the program. An 

overview of the partially completed NRA/ERA PRSEUS specimen testing is shown Figure 1. 

FIGURE 1. OVERVIEW OF HWB PRSEUS AIRFRAME DEVELOPMENT TESTING
PRSEUS Acoustic Panel Fabrication

2

The primary objective of this task order contract was to design and fabricate an acoustic test 

specimen that would be delivered to NASA-LaRC to support a NASA-funded test program. In 

parallel with this testing, some initial conceptual investigations were completed to assess the 

manufacturing feasibility of changing specific panel design parameters that could improve the 

acoustic signature without adding substantial weight to the panel. Techniques such as integral 

damping and hybrid materials in the skin were conceptually assessed, along with some other 

alternatives that could potentially reduce sound transmission through PRSEUS structures. The 

overall work statement of this 12-month project is summarized below in Figure 2.

FIGURE 2. BASELINE SCHEDULE AND WORK STATEMENT

In parallel with the concept development activities, the specimen fabrication tasks were

completed and resulted in the delivery of a 4-ft by 4-ft PRSEUS test panel to the NASA-LaRC 

Structural Acoustic Loads Transmission (SALT) test facility in mid April 2011. The completion 

of this milestone represented the majority of the work plan, leaving only the final reporting and 

test coordination activities to close out the task order contract.

At this early stage in the development of the PRSEUS structural concept, the acoustic studies are 

emphasizing experimentation in order to quantify a baseline set of noise and vibration 

parameters that can be used to quantitatively measure the baseline, as well as calibrate the 

analytical methods that will ultimately be required to assess future candidate improvements to 

the baseline panel construction. 
PRSEUS Acoustic Panel Fabrication

3

 



Gathering a consistent set of design guidelines for the acoustic specimen was complicated 

slightly by the fact that several different HWB baseline configurations are being concurrently 

studied within NASA and Boeing at any given point in time. Although nearly all of the structures 

data was derived using the 408,000-lbs MTOW BWB-5-200G planform (Ref 1), the 

aerodynamic studies were primarily focused on the larger 867,000 to 940,000-lbs MTOW BWB450 baseline airplane. Normally such large differences in MTOW would lead to substantially

different structural gauges and panel geometries, but in this case, the critical acoustic regions are 

typically concentrated in the thinnest or minimum-gauge regions of the cabin. For a conventional 

tube-and-wing aircraft the minimum-gauge panel regions are strongly influenced by the fuselage 

radius, which is more or less, dictated by the specific payload/MTOW of the design. This is 

different for the flat-sided HWB panels, which are primarily sized by the internal pressure, or 2P 

loading condition, making it much less sensitive to vehicle size or weight. As such, the 

minimum-gauge panel geometries derived from the BWB-5-200G configuration can easily be 

combined with the aerodynamic properties derived for the BWB-450 configuration to generate a 

consistent set of test parameters needed for conducting an initial acoustic assessment.

  
!"!#$

The higher MTOW BWB-450-1L planform (Figure 3) was used to derive the boundary layer 

thickness for the acoustic analyses and testing activities. (Note: The “1L” nomenclature 

designation is for configuration control and denotes a minor planform change for a particular 

study.) 

FIGURE 3. AERODYNAMIC BWB BASELINE CONFIGURATION
PRSEUS Acoustic Panel Fabrication

4

B	 
	 
	 	 	 
	 
	 	 
	 
	 
	 

 were 

calculated using CFD methods and are plotted in Figure 4 using the following flow parameters: 

M= 0.85, Re = 170,380, T= 394°R.

FIGURE 4. BOUNDARY LAYER THICKNESS FOR THE BWB-450-1L CONFIGURATION

% 
"&#$"	 &#$'
((")

The nominal 4-ft by 4-ft test frame opening in the SALT test facility was selected as the design 

envelope for the acoustic specimen (Figure 5). Diffuse acoustic field transmission loss and point 

excited radiated sound power measurements will be made while the panel is installed in the 

SALT test facility window. These results will then be compared with known structures concepts. 
PRSEUS Acoustic Panel Fabrication

5

FIGURE 5. ACOUSTIC TESTING APPROACH IN SALT FACILITY

Vibration tests will be conducted in two different boundary conditions: a) free-free, and 

b) semi-clamped condition - around all panel edges when mounted in the TL suite window. A 

laser vibrometer may be used to scan the normal velocity response on the surface of the panel 

subject to point force shaker excitation. 

*  ! &$'+$"#$",'

The highly integrated collection of dry warp-knit fabric, pre-cured rods, and foam-core materials 

are assembled and then stitched together to create a PRSEUS panel (Figure 6). Load path 

continuity at the stringer-frame intersection is maintained in both directions. The 0-degree fiber 

dominated pultruded rod increases local strength/stability of the stringer section while 

simultaneously shifting the neutral axis away from the skin to further enhance the overall panel 

bending capability. Frame elements are placed directly on the IML skin surface and are designed 

to take advantage of carbon fiber tailoring by placing bending and shear-conducive lay-ups 

where they are most effective. The stitching is used to suppress out-of-plane failure modes, 

which enables a higher degree of tailoring than would be possible using conventional laminated 

materials.

FIGURE 6. PULTRUDED ROD STITCHED EFFICIENT UNITIZED STRUCTURE (PRSEUS)
PRSEUS Acoustic Panel Fabrication

6

In addition to enhanced structural performance, the PRSEUS fabrication approach is also ideally 

suited to the compound curvatures found on the HWB airframe. The self-supporting stitched 

preform assembly feature that can be fabricated without exacting tolerances and then accurately 

net molded in a single oven-cure operation using high-precision outer moldline (OML) tooling

(Figure 7). Since all of the materials in the stitched assembly are dry, there are no out-time, or 

autoclave limitations as in prepreg systems, which can restrict the size of an assembly as it must 

be cured within a limited processing envelope. 

FIGURE 7. STITCHED DRY FABRIC USED TO CREATE SELF-SUPPORTING PREFORM

Resin infusion is accomplished using a soft-tooled fabrication method where the bagging film 

conforms to the inner moldline (IML) surface of the preform geometry and seals against a rigid 

OML tool, thus eliminating costly internal tooling that would normally be required to form 

net-molded details (Figure 8). The manufacture of multiple PRSEUS panels (Ref 1 and 2) proved 

that the essential feature of this concept – the self-supporting preform that eliminates interior 

mold tooling – is feasible for the near-flat geometry of the HWB airframe. This task order will 

use these same techniques to fabricate the acoustic test panel. 

FIGURE 8. RESIN INFUSION APPROACH AND CURED PANEL

- ( "$.  &$'

The acoustic specimen was designed using the same materials, features, dimensions, and 

processing parameters as were used in the prior testing efforts (Ref 1 and 2). The material 

callouts were also consistent with the Multi-Bay Pressure Box specimen (Figure 9). The nominal 

6-inch stringer and 24-inch frame pitch used for the acoustic test panel were selected to match 

existing toolsets to minimize fabrication costs. (Figure 10) 
PRSEUS Acoustic Panel Fabrication

7

FIGURE 9. PRSEUS PANEL MATERIALS USED FOR MULTI-BAY BOX SPECIMEN

FIGURE 10. TEST PANEL STRINGER AND FRAME LAYOUT
PRSEUS Acoustic Panel Fabrication

8

The wider stringer flange base (3.37 dimension in Figure 11) was used to maintain continuity 

with the Phase II tooling and second-generation stitching head end effector. This flange width 

and stitch seam spacing differs from the newer improved narrower design used for the Multi-Bay 

Box specimen which is enabled by the third generation stitching head improvements. 

FIGURE 11. STRINGER WRAP GEOMETRY

The nominal skin gauge is .052-inch thick (1 stack) in the center region of the panel. Filler stack

pieces (Figure 12) were added around the periphery of the panel to create a common three-stack 

land (.156 inch) that was later ground flat on the IML side to create a uniform surface for 

clamp-up within the test frame. The principle material axis for the skin is aligned perpendicular 

to the stringers to minimize pressure pillowing during pressurization. 

FIGURE 12. NOMINAL PANEL EDGE GEOMETRY

The frames are a two-stack arrangement with the principle material axis aligned along the length 

of the frame. A Rohacell closed-cell foam detail with machined features is used as the core 

element of the sandwich-like frame design (Figure 13). Fiberglass inserts were not needed, or 

used, for the core ends since the frames are not bolted or restrained by the test fixture.
PRSEUS Acoustic Panel Fabrication

9

FIGURE 13. NOMINAL FRAME GEOMETRY

Conventional single-sided double-row stitching was used to attach the frame and stringer details. 

Stitch placement along the fillets and flange edges (Figure 14) is primarily dictated by the fixed 

needle penetration geometry of the stitching end effector, but also changes slightly as the overall 

stack thickness varies.

FIGURE 14. NOMINAL STITCH SEAM LOCATIONS IN FRAMES AND STRINGERS
PRSEUS Acoustic Panel Fabrication

10

/  !# $!( #$ &

Material properties and design values were derived from the test data developed by the ACT 

Composite Wing program (Refs 3 and 4). The fiber system was generally based on 

medium-performance AS-4 fibers, with some selective usage of IM-7 fibers to improve tensile 

performance. The acoustic test panel utilized the Class 72 Type I warp-knit fabric arrangement 

which is comprised exclusively of AS-4 (or equivalent intermediate modulus fibers). Further 

acoustic optimization studies should consider changes to the warp-knit fabric architecture

(Figure 15) by modifying or adding mixed fibers, embedded elements, and/or interlayer damping 

features. The inclusion of such features, introduced during the warp knitting operation, would 

have little effect on the overall material costs.

FIGURE 15. WARP-KNIT FABRIC ARRANGEMENT

The panel material properties are largely based on the results of material testing performed in 

support of the ACT wing program (Ref 3). Although the current version of the materials 

properties database is limited in scope and only encompasses a simplified set of baseline material

properties proposed for use in development activities, it will continuously be updated to reflect 

the future design, testing, and analysis needs as additional test data becomes available (Table 1). 

TABLE 1. PANEL FABRIC SPECIFICATIONS

Skin and Tear Straps DMS-2436D, TYPE 1, CLASS 72

Stringer Wrap DMS-2436D, TYPE 1, CLASS 72

Frame Wrap DMS-2436D, TYPE 1, CLASS 72

Edge Doublers DMS-2436D, TYPE 1, CLASS 72

Type 1 laminates consist of AS4 fibers only and have a fiber pattern of (44.9/42.9/12.2) and per 

the stacking sequence shown in Table 2. The laminate stiffness for Type I laminates is listed in 

Table 3, while the laminate strengths for thin gauge samples are listed in Table 4. The stitching 

angle for these laminates is in the X direction (0-deg fiber direction). 
PRSEUS Acoustic Panel Fabrication

11

TABLE 2. WARP-KNIT FABRIC STACKING ARCHITECTURE

Ply Number Orientation FAW-Class 72

1 +45 153

2 -45 153

3 0 320

4 90 173

5 0 320

6 -45 153

7 45 132

TABLE 3. LAMINATE STIFFNESS

Tension Compression

Ex

(msi)

Ey

(msi)

Gxy

(msi)

xy Ex

(msi)

Ey

(msi)

Gxy

(msi)

xy

Type 1 Class 72 10.25 5.07 2.48 0.403 9.23 4.66 2.26 0.397

TABLE 4. LAMINATE UNNOTCHED STRENGTHS [KSI]

Laminate

B-Allowable stress

Ftx Fcx Fty Fcy Fs

Type 1 Class 72 105.1 79.2 46.5 37.9 29.9

The compression strength design values are typically governed by the compression-after-impact 

(CAI) values which are a function of the number of stacks and the non-detectable damage levels 

that are used. For the external components, the impact energy limits were 100 ft-lb, while 

internal components were limited to 20 ft-lb impacts. Table 5 and Table 6 specify the allowable 

CAI strength for the Class 72 Type I laminate as a function of material thickness. (Ref 4) 
PRSEUS Acoustic Panel Fabrication

12

TABLE 5. LAMINATE CAI STRENGTH FOR EXTERIOR MEMBERS (100 FT-LB IMPACT)

Stacks Thickness

[in]

Stress, longitudinal 

[ksi]

Stress, transverse 

[ksi]

2 .110 38.8 19.6

3 .165 38.8 19.6

4 .220 38.8 19.6

5 .275 38.8 19.6

TABLE 6. LAMINATE CAI STRENGTH FOR INTERIOR MEMBERS (20 FT-LB IMPACT)

Stacks Thickness

[in]

Stress, longitudinal 

[ksi]

Stress, transverse 

[ksi]

2 .110 37.9 22.2

3 .165 42.0 24.6

4 .220 47.6 27.9

5 .275 53.3 31.2


  # $! ( #$ & - Rohacell 110 WF foam was used in the frame. Table 7 lists the 

minimum stiffness and strength properties for Rohacell foam at RT.

TABLE 7. ROHACELL MINIMUM PROPERTIES

Rohacell Density Compressive 

Strength

Tension 

Modulus 

Shear 

Strength

Shear 

Modulus 

Tensile 

Strength

lbs/ft3 psi psi psi psi psi

110 WF 6.24 407 21000 294 7950 441
PRSEUS Acoustic Panel Fabrication

13

 # $! ( #$ &- The rods were fabricated using a compression molding technique 

with a Toray unidirectional T800/3900-2B fiber/resin system. Since only a limited test database 

exists for the rods using this manufacturing approach, a representative set of mechanical 

properties (Table 8) was generated for the molded rods used in the PRSEUS panels. Since this 

data was compiled from material supplier literature, it is only intended to be used for preliminary 

development activities and should be replaced with actual test data at the earliest opportunity. 

TABLE 8. ROD MECHANICAL PROPERTIES

Laminate Mechanical Properties Test 

Condition Minimum Average

Tension

 Ultimate Strength, ksi RT 390

 Modulus, Msi RT 22.0

 Ultimate Strain, percent RT 1.68

Notched Tension,

Ultimate Strength, ksi

RT

180°F

67.5

62.0

Notched Compression,

Ultimate Strength, ksi

RT

180°F

42.0

35.0

Compression

 Ultimate Strength, ksi RT

180°F

200

176.2

 Modulus, Msi RT

-75°F

18.2

18.2

Comp After Impact,

Ult Strength, ksi, 270 in-lb RT 40.5

Compression Interlaminar Shear, Ult 

Strength, ksi

RT

180°F

9.00

7.50
PRSEUS Acoustic Panel Fabrication

14

0$. #!1 ",2& - All reported strength values in this document are for RTD 

condition. When environmental conditions are to be considered in the analysis, these RTD 

strength value should be multiplied by the appropriate Renv ratio listed in Table 9. (Ref 3)

TABLE 9. ENVIRONMENTAL CORRECTION RATIOS

$!   # $! . # 




 #$

#") # &$ All Ft CD 0.933

#") ".( &&$ All Fc HW 0.601

	 &$3# $.("# All tai CD 0.933


.( &&$3# $.("# All cai HW 0.919

4!  #5& "#$# &$ Warp/knit uht CD 0.954

4!  #5& "#$# &$ Braided uht CD 0.819

4!  #5& "#$".( &&$ AS4 

Warp/knit 

uhc HW 0.823

4!  #5& "#$".( &&$ IM7 

Warp/knit 

uhc HW 0.814

4!  #5& "#$".( &&$ Braided uhc HW 0.768

4! + $'$$#$!$ ! Warp/knit Fbri HW 0.779

4! + $'$$#$!$ ! Braided Fbri HW 0.809

4! + $'$ ! Warp/knit Fbry HW 0.776

4! + $'$ ! Braided Fbry HW 0.842

4! + $'!#$.#  Warp/knit Fbru HW 0.863

4! + $'!#$.#  Braided Fbru HW 0.908

&#  (!!5#)')$ ! All Fpty HW 0.771

&#  (!!5#)')!#$.#  All Fptu HW 0.882
PRSEUS Acoustic Panel Fabrication

15

% 


	

One 4-ft by 4-ft specimen was fabricated under this task order contract. The stitching and cure 

tooling shown in the photographs was procured under a prior NASA NRA Phase II task contract 

(NNL07AA48C, Project No. 4200208122) and loaned to this task order. 

%  3.
&& .+!#$#")$'

Although the acoustic test panel was designed to accommodate an existing toolset, some 

modifications were made to the stitching frame tooling to make room for the additional stack 

build-ups around the panel edges. Once these changes were made, the specimen fabrication 

proceeded as planned without any problems or deviations during any aspect of the build process. 

Each step in the preform build-up – from the initial material trimming on the Gerber flatbed 

plotter, to the stringer and frame detail placement (Figure 16), to the tear strap and skin lay 

down, to the final stitching operation to complete the preform assembly (Figure 17) – was 

completed as planned. 

FIGURE 16. STRINGER AND FRAME DETAILS INSERTED INTO PREFORM

The preform was stitched using two types of stitching methods. The stringer details were 

individually stitched with two rows of stitching placed through the webs using a conventional 

two-sided needle-and-bobbin arrangement prior to being loaded into the preform assembly 

fixture. Once all the preform details were located in the fixture, they were stitched together using 

the numerically controlled-and-driven single-sided stitching process pictured in Figure 18. 
PRSEUS Acoustic Panel Fabrication

16

FIGURE 17. DOUBLER AND SKIN DETAILS ADDED PRIOR TO STITCHING

FIGURE 18. SINGLE-SIDED STITCHING TECHNIQUE (DIFFERENT PANEL SHOWN) 
PRSEUS Acoustic Panel Fabrication

17

The six-axis robotic stitching system inserts two seams simultaneously, one vertically and the 

other at a 45-deg angle to produce a modified single-sided chain stitch of 1200d Vectran sewing 

thread. The combined preform and assembly tool is then flipped upside-down as a single unit and 

placed onto the cure tool surface, where the stitching tool foam block details are released and 

removed. 

%%  &$3&$
 

The edges of the stringer and frame members of the dry preform are indexed to tooling features 

on the cure tool that provide positive dimensional control. Silicon bagging aids are placed over 

the stringers, and a pleated nylon bag is then placed over the entire preform and sealed against 

the cure tool surface. The bagged preform was then placed in an oven, where under vacuum 

pressure, a liquid resin system was infused at 140-deg F into the dry fabric (Figure 19), and then 

cured using the Controlled Atmospheric Pressure Resin Infusion (CAPRI) out-of-autoclave 

forming process. 

FIGURE 19. ACOUSTIC PANEL DURING RESIN INFUSION 

The infused panel was initially cured at 250-deg F (Figure 20), before being removed from the 

oven and stripped of the bagging material and resin infusion lines. It was then placed back in the 

oven for the final 350-deg F free-standing post-cure operation. The final cured specimen is 

shown in Figure 21. 
PRSEUS Acoustic Panel Fabrication

18

FIGURE 20. COMPLETED RESIN INFUSION OPERATION

FIGURE 21. CURED SPECIMEN BLANK PRIOR TO EDGE TRIM

The surface quality and overall appearance of the panel was good (Figure 22 and 23). Visual 

inspection of the part surfaces, along with a detailed inspection of the discarded flow media, 

indicated that resin flow and penetration went as expected and there was no suggestion of voids 

or resin starved areas. Therefore, an NDI inspection was not needed nor performed. 
PRSEUS Acoustic Panel Fabrication

19

FIGURE 22. CLOSE-UP OF CURED IML SURFACE

FIGURE 23. CURED SPECIMEN OML SURFACE

%* ' 	$.")$$'

The final edge trim and land grinding operations were performed by a local machining vendor. 

The stringers and frame elements were machined away at the ends to create a 1/8-inch gap 

relative to the test frame holding fixture. Once the edge trim was completed (Figure 24), the 

panel was boxed up and shipped to NASA-LaRC where the perimeter holes were match-drilled 

to the existing hole pattern in the test fixture opening. 
PRSEUS Acoustic Panel Fabrication

20

FIGURE 24. SPECIMEN EDGE TRIM MACHINING AT VENDOR FACILITY

%-  !$. &$!
) ",

Depending on the panel size, curvature, fiber orientation, and edge configuration, PRSEUS 

panels are known to display some degree of panel warping; particularly washout at the edges 

caused by the thermal residual stresses that build up during the cure cycle. For panels with free 

edges, i.e. those not restrained by a parallel stiffening element (stringer, frame, or integral cap 

feature), the out-of-plane displacements are more pronounced and can be up to a .10 inch. In the 

center regions of the panel where the skins are restrained by the highly rigid stringer and frame 

elements, skin displacements that cannot be seen with the naked eye can be measured. In these 

regions, the skin bows slightly toward the IML side of the panel (which will be pushed out 

during pressurization). These out-of-plane displacements were measured for the acoustic panel 

by NASA-LaRC and are shown plotted in Figure 25. Although the panel deflections are within 

typical airframe assembly tolerances, more work should be done to characterize these distortions 

since they can be compensated for in the cure tooling so that the final part positions are 

net-molded to the nominal engineering dimensions. 

FIGURE 25. PANEL OML SURFACE DISPLACEMENT (INCHES) – FRAMES ARE VERTICAL
PRSEUS Acoustic Panel Fabrication

21

%/  !
(#. )$.+$"#$

An adaptor frame required to install the test panel in the SALT test facility has been manufactured 

and is shown in Figures 26-28. The adaptor frame is a stiff, 6-inch wide sandwich configuration 

consisting of a two inch thick medium density fiberboard (MDF) core bonded between two 0.25-inch 

thick aluminum face sheets. Inner and outer hole patterns were machined in the frame corresponding 

to the test panel perimeter and SALT window hole patterns respectively. The inner hole pattern was 

assigned a uniform distribution while the outer hole pattern was developed from a 2D projection of 

the actual SALT window hole pattern measured with a LTD-901-B Leica scanning system. 0.25-inch 

thick by 1.125-inch wide clamping bars are applied to secure the panel to adaptor frame with a nearly 

uniform pressure distribution. The clamping bars were overlapped at the corners to avoid significant 

discontinuities in the boundary condition. Material properties of the adaptor frame components used 

for modeling purposes are given in Table 10. 

FIGURE 26. ADAPTOR FRAME DETAIL
PRSEUS Acoustic Panel Fabrication

22

FIGURE 27. ADAPTOR FRAME GEOMETRY

FIGURE 28. ADAPTOR FRAME CROSS SECTION GEOMETRY
PRSEUS Acoustic Panel Fabrication

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TABLE 10. FRAME COMPONENT MATERIAL PROPERTIES

Tensile Modulus (Msi) Poisson’s Ratio Density (lb/ft3)

Aluminum 10.59 0.33 173.55

MDF 0.13 0.25 45.20

The panel warp described in the previous section was accommodated with the layered aluminum 

shim shown in Figures 29 and 30. The shim consists of two parts conforming to the IML and OML 

sides of the panel perimeter respectively and is comprised of approximately 23 layers of 3MTM 438 

Heavy Duty Aluminum Foil Tape in total. The tape was applied in layers to the adaptor frame and 

clamping bar underside according to the panel OML scan data set to provide a contoured shim fitted 

to the perimeter. The shim was then compressed between clamping bars and adaptor frame with 15 

ft-lbs torque applied to each fastener and left to relax over time. Prior to this, a 10-layer deep test 

shim was applied to one leg of the adaptor frame and compressed in a similar manner to assess 

relaxation and measure the final layer thickness. The layer thickness was found to approach the 

nominal aluminum backing thickness after relaxing. 

FIGURE 29. LAYER SHIM MAP
PRSEUS Acoustic Panel Fabrication

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FIGURE 30. SHIM FABRICATION
PRSEUS Acoustic Panel Fabrication

25

* 		


	

	

The purpose of the planned testing is to establish baseline vibroacoustic characteristics of the 

HWB PRSEUS minimum gauge pressure panel geometry under point force and diffuse field 

acoustic excitations. Acoustic TL measurements of the panel will be taken and compared with 

historical TL measurements from conventional fuselage configurations. Experimental results will 

also be used to update and verify Finite Element Analysis (FEA) and Statistical Energy Analysis 

(SEA) models of the test article so that the noise reduction capability of the HWB PRSEUS 

concept under representative flight acoustic loads can be further studied with reduced 

uncertainty. The testing is divided into freely hung structural vibration and in-situ vibroacoustic 

tests as described in the following sections. 

*  !4'#"#!6$+#$	 &#$'

The HWB PRSEUS minimum gauge pressure panel is expected to exhibit multiple wave types 

including flexural and in-plane plate waves in the bay and frame regions as well as torsional, 

flexural, and in-plane waves in the pultruded rod stiffeners. The wave type of most interest is the 

flexural plate waves as they are the largest contributors to normal velocity in the bays and 

frames, which are expected to be the most significant radiators. By measuring the normal 

velocity of the OML under point force excitation, the behavior most important for interior noise 

consideration can be studied and used to verify numerical models of the structure. The test 

procedures described below are designed to do this over three decades of frequencies – 

approximately from 10 Hz to 10 kHz. 

2 7 "' : The low frequency range is qualitatively defined as the frequency range 

within which the modal overlap is low and separate modes are easily discernable from one 

another. Modes of the panel in the low frequency range are considered global in nature, that is, 

the characteristic flexural wavelength in the panel is large and spans multiple bays. In this 

frequency range, it is suitable to model the structure with deterministic FEA. 

The panel will undergo a modal survey and the results will be used to evaluate the FE model’s 

ability to adequately represent the low frequency dynamics. It will be situated in a freely hung 

boundary condition and excited with normal point force excitation at specified locations while 

the OML normal velocity is recorded with a scanning laser vibrometer. The freely hung 

configuration is desired to avoid additional complexities due to boundary effects. Bungees are to 

be used to approach a freely hung boundary condition and should be situated along the perimeter 

of the panel near the frames to avoid bungee interaction with the lowest frequency modes 

(ignoring rigid body modes). With the vibrometer scan data set, a modal correlation can be made 

using the Modal Assurance Criterion to evaluate mode shape accuracies and, subsequently, 

natural frequencies. Modal curve fitting methods can also be used to evaluate the panel’s modal 

damping. 

To evaluate the vibroacoustic capabilities of the FEA and SEA models, the test panel will be 

installed in the SALT facility window (Figure 31) separating reverberant and anechoic chambers 

for TL and sound radiation testing. The in-situ configuration requires an adaptor frame, which 

has been designed as discussed previously to provide a nearly clamped boundary condition at the 

panel perimeter. The adaptor frame will, however, introduce a boundary condition at the panel 

perimeter that is influenced by a combination of the adaptor frame’s modal content and the 

stiffness of the panel-to-adaptor frame coupling. 
PRSEUS Acoustic Panel Fabrication

26

FIGURE 31. SALT FACITILY LAYOUT

An extension to the panel FE model including the adaptor frame has been developed. The 

veracity of the extended model, shown in Figure 32, is to be evaluated by first evaluating the 

model of the adaptor frame in isolation. A modal survey of the adaptor frame in a freely hung 

configuration will provide the low frequency modal content for model correlation. Once this is 

completed, an evaluation of the panel-to-adaptor frame coupling can also be made by repeating 

the modal survey with the panel coupled to the frame in a freely hung configuration. 
PRSEUS Acoustic Panel Fabrication

27

FIGURE 32. PRSEUS TEST PANEL FEM WITH ADAPTOR FRAME (235,914 DOFS)

$ 7 "' : The mid frequency range exhibits both global and local mode behavior. 

In this frequency range, the modal overlap becomes too great to study the dynamic behavior 

deterministically, but the global mode dynamics require a deterministic modeling approach (as 

opposed to a statistical modeling approach such as SEA) to be effectively represented. The 

approach taken here is to use a deterministic FE model to capture the dynamics of the structure 

up to 3 kHz, which is expected to overlap the early frequencies of the high frequency range. FE 

model results up to 3 kHz are then to be post processed in terms of frequency band averaged 

subsystem energy content and power input. Here, a subsystem is defined as a group of modes 

with similar characteristics, such as the flexural modes in a bay. 

The FE model in the mid frequency range is to be correlated with experimental results. For this, 

the panel is to be situated in a freely hung condition and excited with normal point force 

excitation while the normal velocity is recorded from the OML side with a scanning laser 

vibrometer. Multiple point force excitations are required in this case to assess the spatial 

variation of input mobility and power input. Data from the vibrometer scan can then be used to 

determine subsystem energy content relative to power input. Correlation of the test results with 

the FE model in the mid frequencies would then be evaluated in a band and space averaged sense 

as opposed to correlating mode by mode. Structural damping is expected to play a significant 

role in the amount of energy seen in the subsystems relative to the power input. Given this, the 

damping loss factor of the panel should be estimated from experiment and applied to the 

numerical model a priory in order to make a meaningful mid frequency correlation. Estimation 

of the damping can be made using, among others, the Impulse Response Decay Method, which is 

used to estimate the damping in a band averaged sense. 
PRSEUS Acoustic Panel Fabrication

28

4$')  7 " ' 8 The high frequency range exhibits local mode, small wavelength 

behavior with high modal overlap. SEA becomes more applicable in the high frequency range 

and is often useful even in the mid frequencies. 

An SEA model of the PRSEUS panel has been developed and is shown in Figure 33. Energy 

methods will be used to correlate SEA model results with experimental data. The experimental 

data used here will be taken from the same vibrometer scan data sets used when correlating the 

FE model in the mid frequency ranges as discussed previously. Experimental damping 

estimations will be required to arrive at meaningful estimates of subsystem energy.

FIGURE 33. STATISTICAL ENERGY ANALYSIS (SEA) MODEL OF PRSEUS TEST PANEL

*% 5&$#6$+"&#$"	 &#$'

The interaction of the HWB PRSEUS panel with the coupled acoustic field is of additional 

interest for interior noise assessments and concept evaluations. The characteristic structural 

wavelength relative to that of the exterior pressure field and interior acoustic volume determines 

the exterior acoustic loading acceptance and interior acoustic radiation efficiency, respectively. 

Wavelengths in the structure are frequency dependant and are influenced by the substructure 

geometry and laminate configurations among others. The diffuse field excitation TL and point 

force excitation sound power radiation are useful metrics when verifying the numerical models’ 

capability to represent coupled structural acoustic interactions. TL can also be shown in 

comparison with other conventional fuselage types while taking into account mass differences. 

The diffuse field excitation TL of the HWB PRSEUS test panel is to be measured using the 

reverb and anechoic chambers at NASA Langley’s SALT facility. During the TL test, a 

traversing array of acoustic intensity probes will be used to measure the panel’s radiated sound 

power due to OML side diffuse field excitation. The reverberation chamber speaker system is 

capable of exciting room modes from 100 Hz to 12.5 kHz center frequency 1/3 octave bands. 

Reverberation chamber sound levels are measured during the intensity probe scan with an array 

of randomly distributed microphones. The intensity TL measurement method is described further 

in ASTM E2249. 

Sound radiation due to point force excitation is to also be measured in-situ. Point force loading 

tends to excite a more replete set of modes relative to diffuse field excitation, which tends to only 

excite the odd modes. This loading is more characteristic of turbulent boundary layer excitation.

By using the intensity probe array during shaker excitation, the radiated sound power of the 

panel relative to point excited power input can be measured. 
PRSEUS Acoustic Panel Fabrication

29

** 	 &#$' &(&$+$!$#$ &
#"#3.#$

Specimen Configuration: 

Drawing Number: ZJ153699-1 Acoustic Panel Assembly, initially released November 2010. 

NASA Test Responsibilities:

1. Prepare SALT test facility and install specimen.

2. Develop loading profiles and testing sequence. 

3. Develop instrumentation package, install and calibrate gages.

4. Conduct testing and record data. 

5. Prepare and distribute test report. 

Boeing Test Responsibilities:

1. Deliver test specimen and support panel rigging questions. 

2. Provide panel design and material property data as requested.

3. Witness testing.

Cognizant NASA/Boeing Personnel:

1. Richard Silcox, NASA Acoustics, (757) 864-3590, r.j.silcox@nasa.gov 

2. Albert Allen, NASA Acoustics, (757) 864-8462, albert.r.allen@nasa.gov 

3. Adam Przekop, NASA Acoustics, (757) 864-2278, adam.przekop@nasa.gov

4. Alex Velicki, Boeing Structures, (562) 797-2753, alexander.velicki@boeing.com

5. Gopal Mathur, Boeing Acoustics, (714) 714 896-1475, gopal.p.mathur@boeing.com
PRSEUS Acoustic Panel Fabrication

30

- 
6



	6	

As with the development of most new composite structure technologies, the PRSEUS 

development activities have been focused primarily on reducing airframe weight under structural 

loading conditions. Only recently, has consideration been given to optimizing the overall 

fly-away weight, which would also include system-related weight increases for such items as 

lightning strike or as in this case, acoustic treatments. By modifying the base materials and 

design parameter selections, the potential for improving the acoustic response of the cabin 

structure can be more thoroughly explored. Such a multidisciplinary approach at this early stage 

in the development cycle should lead to the lightest weight solution, as well as, identify 

cost-effective improvements that can easily be added during the preform assembly operations 

completed at the material supplier - rather than later in the airframe assembly cycle when 

fabrication costs are proportionally higher. Such simple modifications as depicted in Figure 34

would be of particular interest to include in future design trades and testing activities.

FIGURE 34. CANDIDATE INTEGRAL ACOUSTIC IMPROVEMENTS UNDER CONSIDERATION

- &&$+! 
 &3#

Once the baseline acoustic characteristics of the PRSEUS panel are established, possible areas of 

study could also include the following:

# ! .($' – A highly damped layer embedded in the laminate can potentially reduce 

vibration and sound radiation efficiently by increasing the inherent damping of the structure prior 

to the addition of parasitic damping treatments. In a constrained layer damping configuration, the 

effectiveness of the core damping material is maximized when embedded in the region of highest 

shear strain near the neutral axis. The neutral axis is expected to be located near the middle of the 

laminate cross section for flat or low curvature laminates found in the HWB concept. Reductions 

in interlaminar shear strength are of concern with this approach and may be compensated for 
PRSEUS Acoustic Panel Fabrication

31

with additional stitching or tailored stitch patterns that could encompass entire damping layers or 

discrete features.

4+$ $+ & - Increasing the stiffness of the skin laminate is expected to reduce the 

coincidence frequency above which the bending vibration radiates noise most efficiently. 

Conversely, a higher stiffness will tend to have a lower acceptance of exterior acoustic excitation 

such as the TBL. Using numerical models to vary the laminate material properties may provide 

an opportunity to effect an acoustically beneficial change in the early design stages by modifying 

the laminate configurations. 

 '!' &- Frame and stringer flanges may be tailored (possibly in conjunction with tear 

strap placements) to promote poorly radiating even modes and impede efficiently radiating odd 

modes within the early bay local mode frequency range. Such highly contoured edge features at 

stack drop-offs can easily be accommodated within the PRSEUS fabrication approach because 

the interior surfaces are not hard tooled, thus requiring less precision in material fit-up and tool 

design tolerances.

	  #(!" . # - Creating periodic structures within the bays may be used to promote 

band gap effects within target bandwidths. In terms of the wave description, band gap wave 

propagation is prohibited and enforced motion tends to decay evanescently. In modal terms, 

modal structures are not allowed to form at frequencies within the band gap, thus effecting a 

reduction in response. Periodicity may be applied to the bays through additional tear straps 

running transverse to the pultruded rod stringers. The addition of periodic tear straps solely as a 

noise treatment is not much different than additional parasitic noise treatments late in the design 

stage. However, other multidisciplinary benefits may offset the additional mass. For example, the 

load path created at the tear strap may allow for removal of nearby laminas as mass 

compensation. Tear straps may also be designed to allow systems attachments directly to the 

bays. Systems running along the fuselage would then be able to provide extra mass and damping 

to the bays with little overall added mass. Mid-bay tear straps have also been shown by 

preliminary analyses to reduce bay pillowing due to cabin pressurization. Bay crack arresting 

capabilities may also be improved with additional tear straps.

&& .( & - Distributed vibration absorbers are masses integrated into an insulation foam 

matrix and are used to provide distributed mass-spring tuned damping.

3$' - Conventional noise treatments consist of stand-off layer damping tiles affixed 

to bays with bagged fibrous material placed in channels between frames. Possible areas of 

investigation for conventional noise treatments are:

- Surveying existing damping tile materials, designs

- Surveying existing fibrous material or foam acoustic treatments

- Optimizing area coverage of damping tiles for PRSEUS

- Optimizing acoustic fiber or foam arrangements for PRSEUS

Newly available materials and configurations for damping tiles and acoustic foams may provide 

increased performance per weight over their predecessors. For example, newer polyimide foam 

insulations may have the physical property characteristics to meet aerospace requirements, 

including aircraft sidewall insulation. These new polyimide foams are produced at low densities 

ranging from .2 to 1.0 lb/cu-ft and can be utilized as thermal and/or acoustical insulation. It is 

important to note that polyimide materials are inherently fire retardant due to their chemical 
PRSEUS Acoustic Panel Fabrication

32

composition. This new foam technology has the advantage over previous polyimide foams of 

being manufactured and cured using microwave energy at a lower cost and faster production 

rate. (Ref 5) 


"#$0  $&  (( &&$ - Active noise systems tend to be cost, complexity, and weight 

prohibitive and have not been well suited for broadband noise control historically. However, for 

tonal noise sources produced by, for example, open rotor engines, active noise control may 

become a viable option. Others have effectively applied active noise control near propeller noise 

sources, e.g. Bombardier’s Q400 series aircraft. Such an approach could also be applicable for 

the PRSEUS near open rotor engines currently being assessed as a means of propulsion for the 

HWB.


!#$"! #)& 	 &#$' .(0 . #& – Analytical improvements in the areas of

TBL uncertainty from existing experimental data sets and Random Ensemble approaches applied 

to diffuse field and TBL excitation could also be pursued and then validated with panel testing.

-% (& # ,

Further development activities aimed at improving the acoustic response of PRSEUS structures 

will be undertaken once the initial test results are evaluated relative to known structures. As the 

basic sound transmission characteristics of a PRSEUS structure become better understood, 

different panel design parameters will be analytically assessed, compared back to the test 

database and then ultimately considered for further experimentation – characterized first 

analytically and then validated by further testing. 
PRSEUS Acoustic Panel Fabrication

33

/ 


The primary objective of this task order contract was to design, fabricate, and then deliver a test 

panel to NASA-LaRC for acoustic testing in the SALT test facility. The test results will be used 

to quantitatively measure the fundamental sound transmission characteristics of a PRSEUS 

structure, while also serving as a basis of comparison to calibrate future advanced analysis 

methods development activities. The intent of this testing is to begin addressing the concern that 

a lighter, stiffer, cocured PRSEUS panel construction could be more efficient in transmitting

sound than a conventional built-up aluminum structure - which has more mass and a multi-part 

attachment scheme that helps provide dampening effects. If such a premise is true, then a portion 

of the weight savings achieved by improving the structural efficiency could be lost when the 

system-level weight allocation for sound proofing material must be increased. The test data 

derived from this activity will ultimately be used to minimize these adverse effects by modifying 

PRSEUS materials and design parameters to reduce the overall sound transmission levels

through the integral panel construction. 
PRSEUS Acoustic Panel Fabrication

34

 3  " &

1 NASA Phase I Final Report, “Damage Arresting Composites for Shaped Vehicles”, Velicki, A., 

NASA/CR-2009-215932, Contract NNL07AA48C Project No. 4200208122, September 2008. 

2 NASA Phase II Final Report, “Damage Arresting Composites for Shaped Vehicles”, Velicki, A., NASA/CR-2011-

216880, Contract NNL07AA48C Project No. 4200208122, October 2010. 

3 Mirsamadi, Syd, Advanced Subsonic Technology (AST) Composite Wing Material Stiffness and Allowable 

Strength Properties for Stitched Composite Laminates, 98K0318, Rev. C, September 1998. 

4 Hawley, Art, BWB Material Stiffness and Allowable Strength Properties, March 2005.

5 J. Stuart Bolton, Validation of a polyimide foam model for use in transmission loss applications, Journal Acoustic

Soc. Am. Volume 127, Issue 3, pp. 1872-1872, March 2010.
PRSEUS Acoustic Panel Fabrication

35


9:

;/
<

FIGURE 35. SPECIMEN DRAWING SHEET 1 OF 5
PRSEUS Acoustic Panel Fabrication

36

FIGURE 36. SPECIMEN DRAWING SHEET 2 OF 5
PRSEUS Acoustic Panel Fabrication

37

FIGURE 37. SPECIMEN DRAWING SHEET 3 OF 5
PRSEUS Acoustic Panel Fabrication

38

FIGURE 38. SPECIMEN DRAWING SHEET 4 OF 5
PRSEUS Acoustic Panel Fabrication

39

FIGURE 39. SPECIMEN DRAWING SHEET 5 OF 5
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Contractor Report

 4. TITLE AND SUBTITLE

PRSEUS Acoustic Panel Fabrication 

5a. CONTRACT NUMBER

NNL10AA05B

 6. AUTHOR(S)

Velicki, Alex; Yovanof, Nicolette P.; Baraja, Jaime; Mathur, Gopal; 

Thrash, Patrick; Pickell, Robert

 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

 NASA Langley Research Center The Boeing Company 

Hampton, Virginia 23681-2199 Boeing Research and Technology

 5301 Bolsa Avenue

 Huntington Beach, CA 92647

 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

Langley Technical Monitor: Richard J. Silcox

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 71

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

STI Help Desk (email: help@sti.nasa.gov)

14. ABSTRACT

This report describes the development of a novel structural concept, Pultruded Rod Stitched Efficient Unitized Structure 

(PRSEUS), that addresses the demanding fuselage loading requirements for the Hybrid Wing or Blended Wing Body (BWB) 

airplane configuration with regards to acoustic response. A PRSEUS panel was designed and fabricated and provided to 

NASA-LaRC for acoustic response testing in the Structural Acoustics Loads and Transmission (SALT) facility). Preliminary 

assessments of the sound transmission characteristics of a PRSEUS panel subjected to a representative Hybrid Wing Body 

(HWB) operating environment were completed for the NASA Environmentally Responsible Aviation (ERA) Program. 

15. SUBJECT TERMS

Acoustics; Blended wing body; Composites; Integrated structures; Pultruded rod; Resin infusion; Stiffened panel; Stitched 

composites

18. NUMBER

 OF 

 PAGES

49

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

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Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

October 2010 - September 2011

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

NNL10AD07T

5f. WORK UNIT NUMBER

699959.02.08.07.04

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/CR-2011-217309

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PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE (DD-MM-YYYY)

01- 11 - 2011