November 2013

NASA/CR–2013-218043

LSP Composite Susbtrate Destructive 

Evaluation Test Assessment Manual 

Daniel J. Kovach and Grant J. Erickson 

The Boeing Company, Seattle, Washington
NASA STI Program . . . in Profile

Since its founding, NASA has been dedicated to the 

advancement of aeronautics and space science. The 

NASA scientific and technical information (STI) 

program plays a key part in helping NASA maintain 

this important role. 

The NASA STI program operates under the 

auspices of the Agency Chief Information Officer. 

It collects, organizes, provides for archiving, and 

disseminates NASA’s STI. The NASA STI 

program provides access to the NASA Aeronautics 

and Space Database and its public interface, the 

NASA Technical Report Server, thus providing one 

of the largest collections of aeronautical and space 

science STI in the world. Results are published in 

both non-NASA channels and by NASA in the 

NASA STI Report Series, which includes the 

following report types: 

 TECHNICAL PUBLICATION. Reports of 

completed research or a major significant phase 

of research that present the results of NASA 

Programs and include extensive data or 

theoretical analysis. Includes compilations of 

significant scientific and technical data and 

information deemed to be of continuing 

reference value. NASA counterpart of peerreviewed formal professional papers, but 

having less stringent limitations on manuscript 

length and extent of graphic presentations. 

 TECHNICAL MEMORANDUM. Scientific 

and technical findings that are preliminary or of 

specialized interest, e.g., quick release reports, 

working papers, and bibliographies that contain 

minimal annotation. Does not contain extensive 

analysis. 

 CONTRACTOR REPORT. Scientific and 

technical findings by NASA-sponsored 

contractors and grantees. 

 CONFERENCE PUBLICATION. 

Collected papers from scientific and 

technical conferences, symposia, seminars, 

or other meetings sponsored or cosponsored by NASA. 

 SPECIAL PUBLICATION. Scientific, 

technical, or historical information from 

NASA programs, projects, and missions, 

often concerned with subjects having 

substantial public interest. 

 TECHNICAL TRANSLATION. 

English-language translations of foreign 

scientific and technical material pertinent to 

NASA’s mission. 

Specialized services also include organizing 

and publishing research results, distributing 

specialized research announcements and feeds, 

providing information desk and personal search 

support, and enabling data exchange services. 

For more information about the NASA STI 

program, see the following: 

 Access the NASA STI program home page 

at http://www.sti.nasa.gov

 E-mail your question to help@sti.nasa.gov

 Fax your question to the NASA STI 

Information Desk at 443-757-5803 

 Phone the NASA STI Information Desk at 

443-757-5802

 Write to: 

 STI Information Desk 

 NASA Center for AeroSpace Information 

 7115 Standard Drive 

 Hanover, MD 21076-1320 
National Aeronautics and 

Space Administration 

Langley Research Center Prepared for Langley Research Center 

Hampton, Virginia 23681-2199 under Contract NNL10AA05B 

 

November 2013

NASA/CR–2013-218043

LSP Composite Susbtrate Destructive 

Evaluation Test Assessment Manual 

Daniel J. Kovach and Grant J. Erickson 

The Boeing Company, Seattle, Washington
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 

constitute an official endorsement, either expressed or implied, of such products or manufacturers by the 

National Aeronautics and Space Administration. 
i 

Contents

FOREWORD .................................................................................................................. III

1 SCOPE ..................................................................................................................... 1

1.1 PURPOSE ............................................................................................................. 1 

1.2 BACKGROUND ...................................................................................................... 1 

1.3 DAMAGE PROTECTION PERFORMANCE DATA FOR PANEL CONFIGURATIONS .............. 2 

2 REFERENCES ......................................................................................................... 3

2.1 APPLICABLE DOCUMENTS ...................................................................................... 3 

2.2 NOMENCLATURE ................................................................................................... 3 

3 POST-TEST INSPECTIONS/EVALUATIONS .......................................................... 4

3.1 NON-DESTRUCTIVE DAMAGE AREA ASSESSMENTS ................................................. 5 

3.2 DESTRUCTIVE DAMAGE ASSESSMENTS .................................................................. 6 

4 DELIVERABLES ...................................................................................................... 8
ii

THIS PAGE INTENTIONALLY LEFT BLANK 
iii 

FOREWORD 

The information described in this report was authored by Dan Kovach and Grant 

Erickson. 

The authors would like to acknowledge the contributions and support of Patrice 

Ackerman. 

 
1 

1 SCOPE 

This document provides standalone information for the Post-test Destructive 

Evaluation of composite panels manufactured to NASA Document DOC-128694, 

reference 2.1.1 and tested per NASA Document DOC-128696, Reference 2.1.3. 

1.1 Purpose 

This document defines the post-test non-destructive and destructive 

evaluations of Carbon Fiber Reinforced Plastic (CFRP) test panels for the 

purpose of evaluating the protection capabilities of Lightning Strike Protection 

(LSP) materials developed by the Aerospace Industry. The lightning direct 

effects test described in Reference 2.1.3 of the test articles described in 

Reference 2.1.1 provides a common baseline for correlation and comparison 

between LSP datasets. This will permit technically meaningful comparisons 

between different material types submitted by different manufacturers when 

tested by a capable vendor according to this test procedure. A simulated 

lightning strike on a CFRP panel is expected to produce ablation and 

delamination damage, both through the thickness of the panel and across the 

panel surface area. That damage will be evaluated per instructions in this 

document 

1.2 Background 

The growing application of composite materials in commercial aircraft 

manufacturing has increased the risk of aircraft damage from lightning strikes. 

With this growth in composite usage, new technical challenges arise. 

Composite skinned aircraft are more vulnerable to damage from lightning 

strikes than their aluminum skinned predecessors and new mitigation 

strategies and engineering practices are required to maintain the same level 

of safety and protection as achieved by aluminum skinned aircraft. The 

electrical current incident on an aircraft from a typical lightning strike can 

exceed 200,000 amperes, occurring in a fraction of a second. Without proper 

lightning strike protection, carbon fiber/epoxy and dielectric composites can 

be significantly damaged, particularly at the entry and exit points of the strike. 

Approaches have been developed to protect the composite structures from 

lightning direct effects to reduce damage to acceptable levels by using 

conductive foils or meshes in the outer layer of the composite system. 

When a lightning strike occurs, the points of attachment and detachment on 

the aircraft surface must be found by visual inspection, and then assessed for 
2 

damage by maintenance personnel to ensure continued safe flight operations. 

Repairs may be required to replace damaged composite sections per Federal 

Aviation Administration (FAA) procedures if the damage exceeds the 

allowable damage limits for the structure. 

Lightning test standard waveforms are simplified laboratory-generated 

waveforms that represent key lightning parameters including peak current, 

total energy transferred and signal rise and fall times. These statistical 

lightning environments are specified in the Society of Automotive Engineers 

(SAE) standard, Reference 2.1.4. To ensure flight safety, LSP studies are 

conducted for flight safety air-worthiness standards testing and to gain FAA 

certification. However, differences in preparation of test articles as well as 

variability in test procedures and practices between independent LSP studies 

have made it difficult to compare and contrast performance differences 

between different LSP data sets. A LSP Composite Substrate Lightning Test 

Operations Manual, reference 2.1.3, has been prepared to ensure 

consistency in future lightning strike protection evaluations to allow 

performance correlations across data sets. 

This document specifies the processes to perform post-strike destructive 

damage evaluation of tested CFRP panels. It is recognized that many factors 

besides lightning damage protection are involved in the selection of an 

appropriate LSP for a particular system (e.g., cost, weight, corrosion 

resistance, shielding effectiveness, etc). This document strives primarily to 

address the standardized generation of damage protection performance data. 

1.3 Damage Protection Performance Data for Panel Configurations 

The NASA Aviation Safety Program supports research directed to ensure that 

future composite aircraft will survive lightning prone environments to safely 

navigate the National Air Space. Research to detect and mitigate lightning 

damage on composite aircraft is contained in the Atmospheric Environmental 

Safety Technology project managed at NASA Glenn Research Center, which 

includes a NASA Langley-led subproject titled Atmospheric Hazard Safety 

Mitigation led by Robert Neece. Project milestone AEST4.4.37 (Atmospheric 

Environment Safety Technologies) provides the funding mechanism for the 

development of this document. Additionally, it is the intention of the AEST 

program to manufacture and inspect test panels, both protected and 

unprotected, according to the document cited in section 2.1.1. Note that the 

pre-test Nondestructive Inspection (NDI) requirements for these panels are 

contained in reference 2.1.2. Following manufacture and inspection, these 
3 

panels will be subject to simulated strikes per the procedure identified in 

reference 2.1.3. Following test, it is intended for the panels to be qualitatively 

and quantitatively evaluated for their response, using the guidelines and 

procedures identified in this document. 

Parties interested in acquiring a copy of these documents and the data 

generated from this test effort are invited to contact the AEST Task Monitor, 

George Szatkowski, at his email address (george.n.szatkowski@nasa.gov) or 

phone number (757-846-6149). 

2 REFERENCES 

2.1 Applicable Documents 

2.1.1 NASA Document # DOC-128694, LSP Composite Substrate 

Manufacturing Processing Guide 

2.1.2 NASA Document # DOC-128695, LSP Composite Substrate NDE 

Assessment Manual 

2.1.3 NASA Document # DOC-128696, LSP Composite Substrate Lightning 

Test Operations Manual 

2.1.4 SAE ARP5412A, Aircraft Lightning Environment and Related Test 

Waveforms Rev A 

2.1.5 ASTM E2580 – 07, Standard Practice for Ultrasonic Testing of Flat 

Panel Composites and Sandwich 

2.2 Nomenclature 

AEST - Atmospheric Environment Safety Technologies 

ARP – Aerospace Recommended Practice 

CFRP – Carbon Fiber Reinforced Plastic 

FAA – Federal Aviation Administration 

IWWF – Interwoven Wire Fabric 

LSP – Lightning Strike Protection 

NDI – Nondestructive Inspection 

SAE – Society of Automotive Engineers 
4 

3 POST-TEST INSPECTIONS/EVALUATIONS 

To ensure consistency in lightning strike protection evaluations, perform the 

inspections and evaluations detailed in this section. 

The tested panels will be nondestructively and destructively examined for 

damage including fiber breakout or backside fracture of the panel. 

Nondestructive evaluations include visual surface damage area assessments, 

macro-photography, damage depth assessments by pulse-echo ultrasonic 

methods and optional metal damage assessment by X-ray inspection. 

Destructive inspection is performed by taper sanding and documented by 

macro-photography after completion of the nondestructive inspections. The 

results of this evaluation must be clearly noted in the deliverable report. 

The following list is a summary of the steps to be performed: 

1. Visually examine both sides of panel for evidence of damage. Determine if 

back side of panel has been damaged. Mark outline of visible damage on 

panel side(s), including paint blistering, with indelible non-black marker, 

color #1. Ref section 3.1.1. 

2. Do ultrasonic pulse-echo examination of panel from both sides and mark 

outline of damage on front side of panel with indelible non-black marker, 

color #2 (perceptibly different from color #1). Ref section 3.1.2. 

3. Perform optional X-ray examination of panel. Overlay X-ray film (or 1:1 

rendering of digital image) on panel and mark outline of damage on front 

side of panel with indelible non-black marker, color #3 (perceptibly 

different from colors #1 and #2). Ref section 3.1.3. 

4. Mark a key on each panel delineating mapping between color selection 

and inspection method. Then photograph both sides of panel to capture 

all damaged areas and markings. 

5. Measure and calculate damaged area. Ref section 3.1.1. 

6. Taper sand from the front side to remove damaged material under strike 

point and any simulated lightning reattachment points until only 

undamaged material remains. Ref section 3.2. 

7. Measure remaining thickness (if any) of undamaged panel material in 

locus of attachment point(s) using deep-throat micrometer. 

8. Photograph the areas where damaged material was removed in step 6. 
5 

All indelible markers used to record damage boundaries shall be resistant to 

water and isopropyl alcohol. No solvents or cleaning agents shall be applied 

to panels except for water and isopropyl alcohol. 

Note that all photographs will be shot at 6 megapixel or higher resolution 

using a color digital camera and good photographic technique. Include a 

scale aligned in both X and Y axes and panel identification number in all 

photos. All images shall be provided in .TIFF or .JPEG formats. 

Frequently, damaged regions are circular in shape and an average diameter 

can be measured and used in an area calculation. There are also instances 

where the damage is more rectangular or parallelogram shaped and length 

and width measurements can be made and used to calculate the area of a 

damage region. If the damage is of irregular shape, use geometric 

calculations or computer calculations based on image analysis of a digitized 

photo to determine area of damage. 

Detailed instructions for each step with optional processes for more detailed 

information are in the sections that follow. 

3.1 Non-Destructive Damage Area Assessments 

Surface damage area assessments are made by general visual examination, 

ultrasound and optional X-ray techniques. The visual damage areas are 

obtained by naked eye visual examination of the panels and marking of all 

damage including paint blistering. Pulse-echo ultrasonic technique provides 

the ability to identify borders between damaged areas (i.e., areas containing 

delaminations between composite plys) and undamaged areas in the 

composite through use of instrumented NDI equipment. The optional X-ray 

technique provides X-ray films or photos which can be used to determine 

areas of missing LSP metal elements that cannot be discerned using visual or 

pulse-echo ultrasonic methods. 

3.1.1 Visual Damage Assessment 

Accurate measurements of the damage should be made on the front-side of 

each panel (i.e, the side that is paint-finished and is exposed directly to the 

simulated lightning strike) and back-side (unfinished side) of each panel if 

there is any back-side damage (use a magnifying glass if necessary to 

examine for back-side damage as this can be difficult to detect). Visual 
6 

damage assessment is performed by measurement and calculation of the 

area of the damage. The visual damage area includes the areas of minor 

damage such as paint pitting or blistering as well as major damage such as 

missing material and CFRP fiber breakout and back side fracture. Smoke 

trails may be present after lightning testing, they can extend beyond where 

the paint damage is noticeable and may be an artifact of the test method 

used. The presence or quantity of smoke trail indications is not to be 

considered with respect to the quantification of damaged areas. Once the 

extent of visual damage is determined, draw a line around the damage using 

a non-black indelible marker, color #1. Please note in the deliverable report if 

the back of the test article has been damaged or not. 

3.1.2 Pulse-Echo Ultrasonic Assessment 

Perform pulse echo ultrasonic testing to determine extent or boundary of nonvisible damage in the CFRP of the test article panel. Pulse echo testing 

should be performed to both sides of the panel. It uses a single transducer 

that transmits and receives longitudinal waves in the range of 0.5 to 20 MHz. 

An ultrasonic indication (flaw) is an area with ultrasonic attenuation that is at 

least 6dB larger than the attenuation of the adjacent areas without flaws or 

defects. Delaminations in composites are also exhibited as acoustic signal 

returns at depth levels less than the full thickness of a laminate. This 

procedure, which is explained in Reference 2.1.5, is a manual operation. 

Draw outline of damaged area as determined by pulse echo technique on the 

panel using non-black indelible marker, color #2. 

3.1.3 X-ray Assessment (Optional) 

X-Ray damage assessment may be performed if damage to the protective 

metal layer beyond what can be detected by visual or ultrasonic means is 

suspected. Lightning Strike Protection materials based on Interwoven wire 

fabric (IWWF) concepts tend to be damaged more easily than metal foil or 

expanded metal foil. X-ray is performed with either film or digital techniques, 

and X-Ray resolution is good down to five microns. This technique senses a 

change in density to detect missing metal. From the X-ray results, mark the 

outline of damage on the panel using an indelible non-black marker, color #3. 

3.2 Destructive Damage Assessments 

Destructive assessment involves taper sanding of the damaged area of the 

part to determine how deep the damage actually is since pulse-echo 

ultrasound techniques have difficulty finding damage regions laying deeper 
7 

into a laminate than damaged regions laying closer to the surface contacting 

the ultrasonic transducer. Perform the process as follows: 

1) Clean panel to remove loose paint taking care not to remove markings 

that identify visual and NDI damage. 

2) Carefully inspect the panel to determine if there is a complete puncture 

through the panel. If water or isopropyl alcohol can pass through the 

panel, it shall be considered as punctured. Record remaining undamaged 

depth of laminate as “0.0 cm”. 

3) From the front side only, remove damaged material under strike point in a 

generally circular area by: 

a) Taper sanding (scarf) a relatively circular region under the strike point 

to a depth sufficient to remove all the damaged plies. Use pulse-echo 

ultrasonics to verify that the remaining material after sanding is 

undamaged. Repeat sanding until there are no more indications. Note 

that this could result in eventually sanding completely through the 

panel. 

b) Taper sanding is performed either manually or mechanically using 

various grits of sandpaper and sandpaper grit cutting wheels, 

beginning with coarse (~100 grit) sandpaper. Finish sand with a 240 

grit or finer sanding disk. 

c) Taper sand at a ~30:1 pitch (approximately 0.6 cm per ply for the tape 

and fabric materials employed in the panel (see Reference 2.1.1), the 

ratio of the taper length to depth. The panels contain 16 plies of CFRP 

prepreg tape (with a cured thickness of ~7.5 mils/ply) sandwiched 

between an outer ply on each side of prepreg cloth (with a cured 

thickness of ~8 mils/ply). 

4) Find and measure a minimum value for remaining thickness of each panel 

using deep-throat micrometer and count the plies removed (from the 

sanding operation) in the region of minimum thickness. The taper sand 

pitch and ply orientation allow the number of plies damaged to be easily 

counted. 

5) Solvent clean and wipe dry. 

6) Photograph the areas where damaged material was removed. Verify that 

undamaged plies can be seen and counted, otherwise adjust lighting and 

repeat photograph. Take additional close-up (macro) photos if necessary 

to show detail. 

7) Examples of panels destructively examined in this fashion are given 

below: 
8 

4 DELIVERABLES 

The following items will be included in the deliverable report: 

1) All front and back side photos taken to record artifacts from testing (e.g., 

delamination, fiber breakout, smoke trails, paint blistering, etc.) and 

boundaries of damage visible to eye, pulse-echo ultrasonics and X-ray 

examination(if applicable). 

2) Final calculated values of damage areas (in units of cm^2) for each panel 

for all inspections performed (visual, ultrasonic, X-ray). 

3) Photo(s) of panels with damaged material removed. 

4) Minimum thickness values and removed ply counts for all panels. 
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Contractor Report

 4. TITLE AND SUBTITLE

LSP Composite Substrate Destructive Evaluation Test Assessment Manual

5a. CONTRACT NUMBER

NNL10AA05B

 6. AUTHOR(S)

Kovach, Daniel J.; Erickson, Grant J.

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

NASA Langley Research Center 

Hampton, Virginia 23681 

 

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

National Aeronautics and Space Administration

Washington, DC 20546-0001

 8. PERFORMING ORGANIZATION

 REPORT NUMBER

Document Number: DOC-128697

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

Langley Technical Monitor: George N. Szatkowski

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 24

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

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

14. ABSTRACT

200Word Limit

15. SUBJECT TERMS

Composites; Lightning

18. NUMBER

 OF 

 PAGES

16

19b. TELEPHONE NUMBER (Include area code)

(443) 757-5802

a. REPORT

U

c. THIS PAGE

U

b. ABSTRACT

U

17. LIMITATION OF 

 ABSTRACT

UU

Prescribed by ANSI Std. Z39.18

Standard Form 298 (Rev. 8-98)

3. DATES COVERED (From - To)

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

 62897.02.04.07.20 

11. SPONSOR/MONITOR'S REPORT

 NUMBER(S)

NASA/CR-2013-218043

16. SECURITY CLASSIFICATION OF:

The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, 

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this 

collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and 

Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person 

shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

1. REPORT DATE (DD-MM-YYYY)

01-11 - 2013