August 2013

NASA/CR–2013-218034

LSP Composite Susbtrate Manufacturing 

Processing Guide

Daniel J. Kovach and Kenneth H. Griess

The Boeing Company, Seattle, Washington
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August 2013

NASA/CR–2013-218034

LSP Composite Susbtrate Manufacturing 

Processing Guide

Daniel J. Kovach and Kenneth H. Griess

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

FIGURES ....................................................................................................................... III

TABLES ......................................................................................................................... IV

FOREWORD ................................................................................................................... V

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

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

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

1.3 DAMAGE PROTECTION PERFORMANCE DATA FOR PANEL CONFIGURATIONS .............. 3 

2 REFERENCES ......................................................................................................... 4

2.1 APPLICABLE DOCUMENTS ...................................................................................... 4 

2.2 NOMENCLATURE ................................................................................................... 4 

2.3 TABLE OF RESOURCE OR INFORMATION LINKS ........................................................ 5 

3 TECHNICAL REQUIREMENTS ............................................................................... 5

3.1 COMPOSITE PANEL FABRICATION AND MATERIAL .................................................... 5 

3.2 ACCEPTANCE CRITERIA ......................................................................................... 7 

3.3 METAL FRAME FABRICATION AND MATERIAL ........................................................... 7 

3.4 LIGHTNING STRIKE PANEL ASSEMBLY ..................................................................... 7 

4 ENGINEERING DESIGN DRAWINGS ..................................................................... 8

4.1 DESIGN DRAWINGS ............................................................................................... 9 
ii

THIS PAGE INTENTIONALLY LEFT BLANK 
iii

 FIGURES 

Figure Page 

Figure 4.1-1 LSP Parts List and Notes Sheet 1 ............................................................... 9

Figure 4.1-2 LSP Panel Assembly Sheet 2 ................................................................... 10

Figure 4.1-3 LSP Panel Detail Sheet 3 .......................................................................... 11

Figure 4.1-4 LSP Frame Detail Sheet 4 ........................................................................ 12
iv

TABLES 

Table Page 

Table 2.3-1 Web Links to Material Vendors and Standards ............................................ 5
v

FOREWORD

The information described in this report was authored by Dan Kovach and Ken Griess. 

The author would like to acknowledge the contributions and support of Noel Gerken and 

Grant Erickson. 

Revision 1 of this document contains provisions for the use of a surface film in 

combination with the Expanded Copper Foil (ECF) specified for use as a baseline 

Lightning Strike Protection (LSP) scheme. 
1

1 SCOPE 

This recommended practice establishes a generic reference standard that will 

accommodate lightning strike testing of composite (carbon/epoxy) panels. 

1.1 Purpose 

This document is intended to define Carbon Fiber Reinforced Plastic (CFRP) 

test panel configurations that can be employed for the purposes of evaluating 

the protection capabilities of Lightning Strike Protection (LSP) materials 

developed by the Aerospace Industry. The configurations are intended to 

provide consistent behavior in their response to simulated lightning strikes at 

pre-defined levels when tested by a capable vendor according to a test 

procedure written to enable consistent results (ref section 2.1.2). In response 

to an attachment of a simulated lightning strike on a CFRP panel, one can 

expect to see various levels of ablation and delamination, both through the 

thickness of the panel and with respect to the amount of panel surface area 

that exhibits damage.

Panel configurations defined in this document include: 

An “unprotected” configuration 128694-1 (ref section 4.1), consisting of 

a cured CFRP laminate stackup of tape and fabric prepregs, coated 

with a typical aerospace primer and paint finishing scheme, attached to 

aluminum grounding bars intended to draw electrical current from the 

lightning attachment point to the panel edges and thus to ground. 

A “protected” configuration 128694-2 (ref section 4.1), wherein a layer 

of an LSP material form often used in the Aerospace Industry is 

included in the laminate stackup prior to cure. The CFRP materials, 

finishes and grounding arrangement for this configuration are the same 

as for the “unprotected” configuration.

1.2 Background 

The growing application of composite materials in commercial aircraft 

manufacturing has significantly increased the risk of aircraft damage from 

lightning strikes. With this growth in composite usage, new technical 

challenges arise. Composite skinned aircraft are far 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 conductive aluminum 

skinned aircraft. The electrical current incident on an aircraft from a typical 
2

lightning strike can exceed 200,000 amperes, occurring in less than 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 known lightning strike occurs, the points of attachment and 

detachment on the aircraft surface must be found by visual inspection, and 

then assessed for 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.

Lightning test standard waveforms are simplified laboratory-generated 

waveforms that represent key parameters including peak current, total energy 

transferred & signal rise time to simulate the statistical lightning environment 

established under previous Society of Automotive Engineers (SAE) standard 

developments. To ensure flight safety, LSP studies are conducted to gain 

FAA certification to show performance characteristics of the conductive layers 

placed over composite substrates and subjected to lightning direct effect 

electrical waveforms for flight safety air-worthiness standards testing. Test 

results are often incomparable due to variability in test procedures & practices 

between independent LSP studies. This prevents the ability to acquire 

performance correlations between different LSP data sets.

A universal common practice procedure is needed to add conformity in future 

lightning strike protection evaluations to allow performance correlations 

across data sets. This document specifies the embodiment of a physical 

finished and grounded CFRP panel that defines the baseline test specimen 

from which further damage evaluations can proceed. In addition, this 

document specifies a configuration of the test specimen which has been 

modified to include a common LSP material incorporated into the laminate. It 

is expected that commercial vendors of existing and emerging LSP materials 

and concepts would use the behavior of this protected configuration as a 

baseline performance standard which they would try to meet or exceed. It is 

recognized that many factors besides damage protection are involved in the 

selection of an appropriate LSP for a particular system (e.g., cost, weight, 

corrosion resistance, shielding effectiveness); this document strives primarily 

to address inconsistencies in the generation of damage protection 

performance data. 
3

1.3 Damage Protection Performance Data for Panel Configurations 

The NASA Aviation Safety Program supports research directed to ensure 

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 this standard. Note that the pre-test Nondestructive 

Examination requirements for these panels is contained here-in, but is also 

provided as a standalone document (see section 2.1.1) in accordance with 

the deliverable provisions of the task order defining these documents. 

Following manufacture and inspection, these panels will be subject to 

simulated strikes per the procedure identified in section 2.1.2. Following test, 

it is intended for the panels to be qualitatively and quantitatively evaluated for 

their response, using the guidelines contained in the procedure identified in 

section 2.1.3. 

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 (757-864-6149). 
4

2 REFERENCES 

2.1 Applicable Documents 

2.1.1 NASA Document # DOC-128695 – LSP Composite Substrate NDE 

Assessment Manual 

2.1.2 NASA Document # DOC-128696 – LSP Composite Substrate 

Lightning Test Operations Manual 

2.1.3 NASA Document # DOC-128697 - LSP Composite Substrate 

Destructive Evaluation Test Assessment Manual 

2.2 Nomenclature 

AEST - Atmospheric Environment Safety Technologies 

AN – Air Force Navy Standard 

CFRP – Carbon Fiber Reinforced Plastic 

CRES – Corrosion resistant steel 

DN – Drawing Note 

ECF – Expanded Copper Foil 

FAA – Federal Aviation Administration 

LSP – Lightning Strike Protection 

MS – Military Standard 

MIL – Military Specification 

NCAMP - National Center for Advanced Materials Performance

NIAR – National Institute for Aviation Research 

NMS – NCAMP Material Specification 

NPS - NCAMP Process Specification 

SAE – Society of Automotive Engineers 

SURF – Surfacer
5

2.3 Table of Resource or Information Links 

Hexcel - HexPly http://www.hexcel.com/Resources/DataSheets/Prepreg-Data-Sheets/8552_us.pdf

Dexmet - ECF http://www.dexmet.com

Cytec - Surfacer https://www.cytec.com/engineeredmaterials/products/Datasheets/SurfaceMaster905C.pdf

NCAMP - Standards http://www.niar.twsu.edu/coe/ncamp.asp

https://www.niar.wichita.edu/NCAMPPortal/default.aspx

https://www.niar.wichita.edu/NCAMPPortal/Contact/tabid/104/Default.aspx

 See bottommost link for contact to get NCAMP account to procure documents. 

Table 2.3-1 Web Links to Material Vendors and Standards 

3 TECHNICAL REQUIREMENTS 

3.1 Composite Panel Fabrication and Material 

3.1.1 General Requirements 

All aspects of composite fabrication including processes and equipment 

(material handling, surface preparation, clean room, autoclave, machining, 

drilling, etc.) should be in accordance to industry standards.

3.1.2 Materials 

The following industry specifications and material designations listed are for 

information purposes. Specific materials will be designated for each design 

and will be noted within the engineering drawing and/or notes.

Tape: Hexcel 8552/AS4 (HexPly 8552/AS4), Hexcel Inc., Stamford, CT. 

Fabric: Hexcel 8552/AS4 (HexPly 8552 / A193-PW, 3K-70-PW), Hexcel Inc., 

Stamford, CT. 

Lightning Protection:

Dexmet 3CU7-100FA, expanded copper foil (ECF), Dexmet Corp., 22 Barnes 

Industrial Road South, Wallingford, CT. 

Cytec Surfacemaster 905C Composite Surfacing Film (SURF), 0.035psf, 

Cytec Engineered Materials, Tempe, Arizona, U.S.A. (Global Headquarters) 
6

3.1.3 Laminate 

Laminates are to be designed per common aerospace industry practices 

(balanced, symmetric and sequence). The typical lightning strike panel will 

be quasi-isotropic in nature with a fabric ply on each side of the laminate.

Typical Laminates:

Unprotected:

16 ply tape with 2 ply fabric (as follows): 

[(0/90F)/45/90/-45/0/45/90/-45/0/0/-45/90/45/0/-45/90/45/(0/90F)]

Protected:

16 ply tape with 2 ply fabric and one ply lightning protection (as follows): 

[(SURF)(ECF)(0/90F)/45/90/-45/0/45/90/-45/0/0/-45/90/45/0/-

45/90/45/(0/90F)]

Any “protective configuration” that is cured into the laminate should be added 

to the tool side of the laminate.

Specific laminates will be designated for each design and will be noted within 

the engineering drawing and/or notes.

3.1.4 Cure Cycle 

An example of an industry standard is seen below.

Lay-up, bag and cure laminate per NCAMP Process Specification NPS 81228 

'Fabrication of NMS 128 Qualification, Equivalency and Acceptance Test 

Panels (Hexcel 8552 and 8552S).’ 

3.1.5 Finish 

Only the tool side surface (lightning attach side) need be primed and painted 

with a top coat.

Paint prep: Solvent clean and scuff sand to remove surface contamination. 

Primer: Use an epoxy primer applied per proper aerospace specifications.

Top Coat: Apply aerospace grade top coat per proper aerospace 

specifications.
7

Specific finish will be designated for each design and will be noted within the 

engineering drawing and/or notes.

3.2 Acceptance Criteria 

Use industry standard Through Transmission Ultrasonic (TTU) ‘C’ Scan 

inspection methods to validate cured laminate quality. Any deviations must 

be clearly noted as such in the final test data and report.

3.3 Metal Frame Fabrication and Material 

3.3.1 General Requirements 

All aspects of metal fabrication should be in accordance to industry 

standards.

3.3.2 Materials 

It is recommended that common aluminum sheet stock is used for the frame.

The recommended alloys are 2024, 6061 and 7075. There is no requirement 

as to temper of the alloy. Specific design details will be designated and noted 

within the engineering drawing(s) and/or notes. 

3.4 Lightning Strike Panel Assembly 

3.4.1 General Requirements 

This section contains the requirements for the attachment of the finished 

CFRP panel (both protected and unprotected configurations) to metallic 

grounding bars intended to pull current from the edges of the panel to ground 

(thus completing the electrical circuit from the source of the simulated 

attachment through the panel). This configuration is suitable for evaluating 

co-cured LSP material configurations. 

For alternative LSP material configurations such as conductive finishes or 

adhesively-bonded appliqués, other grounding configurations may be more 

appropriate. In such cases, it is important to recognize that alternative 

grounding configurations must be representative of the proposed installation 

conditions intended for the end-product, as the expected performance of test 
8

panels employing such alternative materials may be highly sensitive to the 

grounding configuration used. Care must be taken in the selection of an 

alternative grounding configuration to avoid generating unrealisticallyoptimistic test results. 

Assistance in the selection of alternative grounding configurations may be 

acquired by contacting the AEST Task Monitor (ref section 1.3). 

3.4.2 Conductive Frame Attach 

The function of the fasteners is to provide a conductive path from the panel to 

the frame and eventually into the test equipment. Common steel or CRES 

fasteners are suitable. The following fastener example is common and easily 

acquired through local fastener vendors:

MS24694S99 (1⁄4-28 cad plated alloy steel bolt, 100 degree head, 

Phillips drive bolt that has a 0.25” grip).

AN315C4R (1⁄4-28 CRES nut). 

AN960C416 (1⁄4” CRES washer). 

Specific design details will be designated and noted within the engineering 

drawing(s) and/or notes. 

4 ENGINEERING DESIGN DRAWINGS 

The drawings included in this document are considered to be baseline 

drawings for both the “unprotected” configuration (with no lightning protection 

scheme) and the baseline “protected” configuration. For any new lightning 

protection schemes, the “unprotected” drawing can be used for the basic 

panel design. In adding the protection scheme, a determination must be 

made as to whether the scheme is cured into the laminate, added to (or in 

place of) the finish, or added on top of the standard finish.
4.1 Design Drawings

Figure 4.1-1 LSP Pa

9

rts List and Notes Sheet 1 
Figure 4.1-2 LSP

10

 Panel Assembly Sheet 2
Figure 4.1-3 LS

11

P Panel Detail Sheet 3 
Figure 4.1-4 LS

12

P Frame Detail Sheet 4
REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

2. REPORT TYPE 

Contractor Report

 4. TITLE AND SUBTITLE

LSP Composite Susbtrate Manufacturing Processing Guide 

5a. CONTRACT NUMBER

NNL10AA05B

 6. AUTHOR(S)

Kovach, Daniel J.; Griess, Kenneth H.

 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

DOC 128694, Rev. 1

10. SPONSOR/MONITOR'S ACRONYM(S)

NASA

13. SUPPLEMENTARY NOTES

Langley Technical Monitor: George N. Szatkowski

12. DISTRIBUTION/AVAILABILITY STATEMENT

Unclassified - Unlimited

Subject Category 01

Availability: NASA CASI (443) 757-5802

19a. NAME OF RESPONSIBLE PERSON

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

14. ABSTRACT

Manufacturing procedures to fabricate protected and unprotected Carbon Fiber Reinforced Plastic (CFRP) test panel configurations that can be employed for 

the purposes of evaluating the protection capabilities of Lightning Strike Protection (LSP) materials are documented in NASA DOC-128694. The composite 

test panels are intended to provide consistent behavior in their response to simulated lightning strikes at pre-defined levels when tested by a capable vendor 

according to a test procedure written to enable consistent results. It is expected that commercial vendors of existing and emerging LSP materials and concepts 

would use the behavior of this protected configuration as a baseline performance standard which they would try to meet or exceed. The unprotected 

configuration consists of a cured CFRP laminate of tape (Hexcel HexPly 8552/AS4) and fabric (Hexcel HexPly 8552 / A193-PW, 3K-70-PW) prepregs, coated 

with a typical aerospace primer (0.5-1.5 mils thick) and paint (4-6 mils thick) finishing scheme. The protected configuration contains a top LSP layer made up 

of Cytec Surfacemaster 905C Composite Surfacing Film above Dexmet 3CU7-100FA expanded copper foil and is included in the laminate stackup prior to 

cure. 

15. SUBJECT TERMS

Composites; Damage protection; Lightning

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22

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(443) 757-5802

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