DOT/FAA/AR-04/40,P4 

Office of Aviation Research 

Washington, D.C. 20591 

Explicit Finite Element Modeling of 

Multilayer Composite Fabric for 

Gas Turbine Engine Containment 

Systems 

Part 4: Model Simulation for Ballistic 

Tests, Engine Fan Blade-Out, and 

Generic Engine

November 2004 

Final Report 

This document is available to the U.S. public 

through the National Technical Information 

Service (NTIS), Springfield, Virginia 22161. 

U.S. Department of Transportation 

Federal Aviation Administration
NOTICE 

This document is disseminated under the sponsorship of the U.S. 

Department of Transportation in the interest of information exchange. The 

United States Government assumes no liability for the contents or use 

thereof. The United States Government does not endorse products or 

manufacturers. Trade or manufacturer's names appear herein solely 

because they are considered essential to the objective of this report. This 

document does not constitute FAA certification policy. Consult your local 

FAA aircraft certification office as to its use. 

This report is available at the Federal Aviation Administration William J. 

Hughes Technical Center's Full-Text Technical Reports page: 

actlibrary.tc.faa.gov in Adobe Acrobat portable document format (PDF). 
 Technical Report Documentation Page 

1. Report No.

DOT/FAA/AR-04/40,P4

2. Government Accession No. 3. Recipient's Catalog No.

5. Report Date

November 2004

4. Title and Subtitle 

EXPLICIT FINITE ELEMENT MODELING OF MULTILAYER COMPOSITE 

FABRIC FOR GAS TURBINE ENGINE CONTAINMENT SYSTEMS 

PART 4: MODEL SIMULATION FOR BALLISTIC TESTS, ENGINE FAN 

BLADE-OUT, AND GENERIC ENGINE 

6. Performing Organization Code

7. Author(s)

Reha Gomuc

8. Performing Organization Report No. 

21-12288 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

Honeywell Engines, Systems & Services 

111 S. 34th Street, P.O. Box 52181 

Phoenix, AZ 85072-2181 

11. Contract or Grant No. 

01-C-AW-ASU 

Subagreement 02-11 

13. Type of Report and Period Covered

Final Report

9/2001 – 5/2003

12. Sponsoring Agency Name and Address

U.S. Department of Transportation 

Federal Aviation Administration 

FAA William J. Hughes Technical Center 

Atlantic City International Airport, NJ 08405 

14. Sponsoring Agency Code

 ANE-100

15. Supplementary Notes

The FAA William J. Hughes Technical Center COTR was Donald Altobelli.

16. Abstract

Honeywell Engines, Systems & Services (Phoenix, AZ) collaborated with Arizona State University (Tempe, AZ), SRI International 

(Menlo Park, CA), and NASA Glenn Research Center (Cleveland, OH) to develop a robust explicit finite element analysis modeling 

methodology for gas turbine engine containment systems using multilayer composite fabrics. Honeywell’s role was to simulate 

ballistic tests using LS-DYNA to validate the fabric material models (Task 3) and to apply the methodologies developed during this 

program to an engine fan blade containment analysis (Task 4). In addition, Honeywell developed a generic model for demonstration 

purposes. This report describes the work performed and the results obtained. 

17. Key Words 

Aircraft Engine, Composite fabric, Material modeling, 

LS-DYNA, Fan containment, Kevlar, Zylon

18. Distribution Statement 

This document is available to the public through the National

Technical Information Service (NTIS) Springfield, Virginia 22161.

19. Security Classif. (of this report)

 Unclassified 

20. Security Classif. (of this page)

Unclassified

21. No. of Pages

 68

22. Price

Form DOT F1700.7 (8-72) Reproduction of completed page authorized
TABLE OF CONTENTS 

Page 

EXECUTIVE SUMMARY ix 

1. INTRODUCTION 1-1 

1.1 Purpose 1-1 

1.2 Background 1-1 

2. NUMERICAL SIMULATION OF BALLISTIC TESTS (TASK 3) 2-1 

2.1 Objective 2-1 

2.2 Analytical Procedure 2-1 

2.3 Finite Element Model Description 2-2 

2.4 Analysis Tools 2-6 

2.5 Analysis Results 2-6 

2.5.1 Kevlar Ballistic Test Simulations 2-10 

2.5.2 Zylon Ballistic Test Simulations 2-13 

2.6 Conclusions 2-18 

3. NUMERICAL SIMULATION OF ENGINE FAN BLADE-OUT TEST 

(TASK 4) 3-1 

3.1 Objective 3-1 

3.2 Analytical Procedure 3-1 

3.3 Fan Blade-Out Test Results 3-2 

3.4 Analysis Results 3-4 

3.4.1 Baseline (1999) Analysis 3-4 

3.4.2 1999 Model With New Kevlar Material Formulation 3-6 

3.4.3 Optimized Methodology and New Kevlar Model 3-7 

3.4.4 Fan Containment Predictions With Zylon 3-9 

3.5 Conclusions 3-10 

4. GENERIC CONTAINMENT MODEL 4-1 

4.1 Objective 4-1 

4.2 Background 4-1 

4.3 Generic Model Files 4-1 

4.4 General Model Recommendations 4-3 

iii 
5. JOHNSON-COOK MATERIAL MODEL 5-1 

5.1 Background 5-1 

5.2 Johnson-Cook Material Model by LLNL 5-1 

5.2.1 Impact Analysis Using the Johnson-Cook Material Model 5-1 

5.2.2 Impact Analysis Using the Honeywell Material Model 5-3 

5.3 Conclusions 5-4 

6. ISSUES, LIMITATIONS, AND LESSONS LEARNED 6-1 

6.1 Background 6-1 

6.2 Effects of Computer Platform and Software Version/Revision 6-1 

6.3 Effects of Contact Parameters 6-3 

7. CONCLUDING REMARKS 7-1 

8. REFERENCES 8-1 

APPENDICES 

A—LS-DYNA User Input for Kevlar and Zylon Material Model

B—Ballistic Test Data and LS-DYNA Simulation Results for Kevlar and 

Zylon Materials

C—Comparison of Ballistic Test Results and LS-DYNA Simulation Results for

Zylon Material

iv 
LIST OF FIGURES 

Figure Page 

2-1 Overall Procedure for the Numerical Simulation of Ballistic Tests 2-2 

2-2 Ballistic Test Setup at NASA GRC 2-3 

2-3 Ballistic Test Finite Element Model 2-4 

2-4 Schematic of the Fabric Simulation Techniques 2-5 

2-5 Ballistic Test Results (NASA GRC Test Data) 2-9 

2-6 Kevlar Ballistic Test Results Versus LS-DYNA Predictions 2-10 

2-7 Projectile Velocity Histogram During a 16-Layer Kevlar Simulation Test 2-11 

2-8 Projectile Position Histogram During a 16-Layer Kevlar Ballistic Test 2-11 

2-9 A 16-Layer Kevlar Ballistic Test Result Versus LS-DYNA Deflection Predictions 2-12 

2-10 Analytical Versus Experimental Deflections for a 16-Layer Kevlar Ballistic Test 2-12 

2-11 Zylon Ballistic Test Results Versus LS-DYNA Predictions 2-13 

2-12 Normalized Ballistic Test Results Versus LS-DYNA Predictions 2-13 

2-13 Zylon Ballistic Test Results Versus LS-DYNA Predictions With MultipleLayer Shells 2-14 

2-14 Effect of Multiple-Layer Fabric Modeling 2-14 

2-15 Deflected Shapes With Single- Versus Multiple-Layer Fabric Modeling 

(Four Fabric Layers) 2-15 

2-16 Deflected Shapes With Single- Versus Multiple-Layer Fabric Modeling 

(24 Fabric Layers) 2-16 

2-17 Kinetic Energy With Single- Versus Multiple-Layer Fabric Modeling 

(Four Fabric Layers) 2-17 

2-18 Kinetic Energy With Single- Versus Multiple-Layer Fabric Modeling 

(24 Fabric Layers) 2-17 

3-1 Overall Procedure for the Engine Fan Blade-Out Simulation 3-1 

3-2 Overall View of the Honeywell Model AS907 Turbofan Engine 3-2 

v 
3-3 Frame From a High-Speed Movie of the AS907 Fan Blade-Out Test 3-3 

3-4 AS907 Fan Containment Housing Following Blade-Out Test 3-3 

3-5 LS-DYNA Model for Fan Blade-Out Containment Analysis 3-4 

3-6 1999 Baseline Fan Containment Analysis—Overall View 3-5 

3-7 1999 LS-DYNA Baseline Fan Containment Analysis—Predicted Internal Damage 3-6 

3-8 1999 LS-DYNA Model Enhanced With New Kevlar Material Formulation 3-7 

3-9 LS-DYNA Analysis With Optimized Methodology and New Kevlar Model 3-8 

3-10 LS-DYNA Analysis With Optimized Methodology and New Kevlar Model—

Predicted Internal Damage 3-9 

3-11 LS-DYNA Predictions With Kevlar and Zylon Material 3-10 

5-1 The LLNL Analysis Using the Johnson-Cook Material Model 5-2 

5-2 Comparison of Predictions Using the Johnson-Cook and Elastoplastic 

Material Models 5-3 

6-1 Effects of LS-DYNA Contact Parameters (Steel Target) 6-3 

6-2 Effects of LS-DYNA Contact Parameters and Platform (Fabric Target) 6-4 

LIST OF TABLES 

Table Page 

2-1 Fabric Properties 2-2 

2-2 Analysis Matrix and Summary of Ballistic Test Simulation Results for Kevlar 2-7 

2-3 Analysis Matrix and Summary of Ballistic Test Simulation Results for Zylon 2-8 

5-1 Johnson-Cook Material Constants for Ti-6Al-4V Determined by LLNL 5-2 

6-1 LS-DYNA Platform, Version/Revision Investigation Summary 6-2 

vi 
LIST OF ACRONYMS 

FAA Federal Aviation Administration 

Honeywell Honeywell Engines, Systems & Services 

HP Hewlett-Packard Company 

IBM International Business Machines 

LLNL Lawrence Livermore National Laboratory 

LSTC Livermore Software Technology Corporation 

NASA GRC NASA Glenn Research Center 

SRI SRI international 

vii/viii 
EXECUTIVE SUMMARY

Modeling a multilayer fabric composite for engine containment systems during a fan blade-out 

event has been a challenging task. Nonlinear transient (explicit) finite element analysis (FEA) 

has the greatest potential of any numerical approach available to industry for analysis of these 

events. Significant research is still required to overcome difficulties with numerical stability, 

material modeling (pre- and postfailure), and standardizing model methods to achieve accurate 

simulation of the complex interactions between individual components during these high-speed 

events. The primary focus of this research was to develop the methodology for testing, 

modeling, and analysis of a typical fan blade-out event in a multilayer fiber fabric composite 

containment system. ABAQUS finite element code was used to verify the basic material model 

(prefailure state) developed through laboratory testing. LS-DYNA was the primary modeling 

tool used in the explicit finite element analysis of ballistic events. 

During the Fourth Federal Aviation Administration (FAA) Uncontained Engine Debris 

Characterization Modeling and Mitigation Workshop (held in May 2000 at SRI International, 

Menlo Park, CA), a representative of Honeywell Engines, Systems & Services presented the 

capability of modeling complicated engine hub-burst and fan blade-out events. Predicting most 

of the event with high confidence was shown. At the same time, SRI International presented 

their efforts on modeling the material characteristics within LS-DYNA and developing a new 

composite fiber material called Zylon that appeared to be stronger, lighter, and more 

temperature resistant than Kevlar. Both parties showed interest in each other’s work, and both 

agreed they could benefit from each other if collaborative mechanisms could be arranged. After 

the workshop, Honeywell and SRI contacted each other and began talks of a joint project. The 

FAA, National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC), 

and Arizona State University (ASU) were later invited into the discussion, resulting in this FAAfunded research under the Aircraft Catastrophic Prevention Program and the Airworthiness 

Assurance Center of Excellence Program. 

The goal of this research was to use the technical strengths of Honeywell, SRI, NASA GRC, and 

ASU for developing a robust explicit FEA modeling methodology for the purposes mentioned 

above. Since the development of an experimental set of data to support the calibration of the FE 

models is essential, various experimental methods to measure material and structural response of 

the fabrics were conducted. NASA GRC under the NASA Aviation Safety Program, conducted 

a series of fabric engine containment ring tests that were used for modeling in this program. 

Each member of the team took a leadership role and developed a comprehensive report 

describing the details of the research task and the findings. The complete FAA report is 

comprised of the following four separate reports (parts 1 through 4). 

• 

• 

Part 1: Static Tests and Modeling by Arizona State University Department of Civil 

Engineering 

Part 2: Ballistic Testing by NASA Glenn Research Center 

ix 
• 

• 

Part 3: Material Model Development and Simulation of Experiments by SRI 

International 

Part 4: Model Simulation for Ballistic Tests, Engine Fan Blade-Out, and Generic Engine 

by Honeywell Engines, Systems & Services 

This report describes work performed under the AACE Cooperative Agreement No. 01-C-AWASU Subagreement 02-11 during the period September 2001 through May 2003 and the results 

of the analytical simulations. 

Overall, the analytical results agreed well with the ballistic test results. Acceptable correlation 

was obtained between the simulation and ballistic test results for both Kevlar and Zylon 

materials, using a single shell-element layer simulating all the fabric layers. Both the energy 

absorption and the overall deflection behavior of the fabric systems were successfully simulated. 

Similar successful analysis-to-test correlations were also obtained when up to four layers of shell 

elements are used to model all fabric layers. 

In addition, a full-scale engine fan blade-out event was successfully simulated using the fabric 

material models and developed analytical methodologies. Acceptable correlation was obtained 

between the simulation results and the engine containment test results, using the new Kevlar 

material model and the single shell layer modeling technique. 

Based on the experience gained during the execution of the above simulations, a generic 

containment FE model, including fabric wraps, was created. This model provides LS-DYNA 

users with generic guidelines for modeling composite fabric wraps in impact containment-related 

applications. This generic model is provided on the CD-ROM version of the report. The 

sensitivity of the results of this type of analysis-to-analysis parameters and solution algorithms

and to the program version and computer platform choices is also discussed. 

x 
1. INTRODUCTION.

1.1 PURPOSE. 

This research effort was undertaken as a direct result of discussions from the Fourth Federal 

Aviation Administration (FAA) Uncontained Debris Characterization Modeling and Mitigation 

Workshop (held in May 2000 at SRI International). A team effort between government, 

academia, and industry was seen as an excellent opportunity to transition fabric modeling and 

testing research, which was being sponsored by the FAA Aircraft Catastrophic Failure 

Prevention program, into commercial aircraft. 

1.2 BACKGROUND.

Composite fiber fabric wraps are widely used in the containment systems of aerospace gas 

turbine engines. Such systems have been found to be especially cost-effective for mitigating 

engine debris during a possible engine fan blade-out event. Compared against traditional 

metallic containment systems, these fabric wrap systems have very high strength per unit weight 

properties and are inexpensive to manufacture. 

LS-DYNA is a commercial explicit finite element program widely used in the analysis of gas 

turbine engine rotor containment applications. This program has been successfully used at 

Honeywell Engines, Systems & Services as an analysis tool to design and optimize containment 

structures. Although there are challenges involved, due to the complexity of these types of 

analyses, many successful modeling experiences exist, especially for containment systems using 

metallic materials. On the other hand, the modeling and analysis of a typical fan blade-out event 

in a multilayer fiber fabric composite containment system has always been a difficult task, 

mainly due to the lack of accurate numerical modeling techniques and material formulations. To 

properly use the advantages of the fabric containment systems, it is necessary to have a robust 

finite element analysis modeling methodology that integrates the representative material 

behavior and the problem-specific analysis techniques. The resulting tool can then be used to 

analyze and optimize the performance of the fabric-based containment systems. 

The primary focus of this research program was to address the technology gaps in this area and 

develop a robust modeling methodology for the analysis of fan blade-out event in a multilayer 

fabric containment system. Some of the specific program objectives are as follows. 

• Couple the LS-DYNA modeling expertise of Honeywell with the material modeling 

capability of SRI, the ballistic testing capabilities of National Aeronautics and Space 

Administration (NASA) Glenn Research Center (GRC), and the experimental facilities 

and finite element analysis/modeling capabilities of Arizona State University. 

• Incorporate the material model developed by SRI into the LS-DYNA modeling 

methodology developed by Honeywell and correlate against the results from controlled 

laboratory hardware tests and then develop new methodologies if necessary. 

1-1
• Develop methodologies for numerical simulation of engine fan blade-out events with 

composite fiber fabric wraps using SRI’s material model and Honeywell’s LS-DYNA 

modeling methodology. Validate the methodologies using existing engine fan blade-out 

containment test results from Honeywell. 

• Compare the efficiency of Kevlar and Zylon wraps through laboratory hardware tests 

and LS-DYNA analysis of the test coupons. 

• Explore the potential of Zylon for future gas turbine engine containment systems. 

This report describes the details of the work conducted by Honeywell to complete tasks 3 and 4. 

First, the ballistic tests were numerically modeled and simulated using the LS-DYNA code. The 

material model developed by SRI using the static test data obtained during task 1 was also 

incorporated into the modeling. Modifications were made to the material model until a 

reasonable correlation was obtained between simulations and the test data for both Kevlar and 

Zylon materials. Second, the resulting material model and the modeling techniques were used to 

model and simulate a recent fan blade-out containment test of a full-scale Honeywell turbofan 

engine to validate the approach. In addition, a generic containment model was also prepared to 

provide the LS-DYNA users with a generic guideline for modeling composite fabric wraps in 

impact containment applications. 

Also included in this report is a brief discussion of the comparisons between a new JohnsonCook material model developed by Lawrence Livermore National Laboratory (LLNL) and the 

conventional metallic material model used by Honeywell in impact-related applications. 

1-2
2. NUMERICAL SIMULATION OF BALLISTIC TESTS (TASK 3).

2.1 OBJECTIVE. 

The primary objective was to develop and calibrate the Kevlar and Zylon material models 

developed under this research program using ballistic test data. 

2.2 ANALYTICAL PROCEDURE.

To achieve the above objective, Honeywell simulated the Kevlar and Zylon ballistic tests 

conducted at NASA GRC and compared the simulation results to the actual test results. The 

detailed steps for the correlation efforts are given below. Figure 2-1 schematically illustrates the 

overall process followed during the execution of task 3. Table 2-1 shows the fabric properties of 

the Kevlar 49 and Zylon AS that were tested. Only the light Zylon AS and Kevlar 49 are 

included in the analysis of this report. 

1. The ballistic tests were conducted at NASA GRC, and the details of the test procedures 

and results are reported in Part 2 of this report [1]. 

2. A composite fabric material model code (common for Kevlar and Zylon) provided by 

SRI was compiled together with the standard LS-DYNA binary files to obtain the userdefined executable. The typical LS-DYNA input deck included the model file (finite 

element nodes and elements), the user-controlled material input parameters (different sets 

for Kevlar and Zylon), the contact file defining the contact types to be used, and the 

control parameters required to run the LS-DYNA code. 

3. Each test condition was properly simulated by changing input parameters, such as the 

fabric material constants, the projectile speed, and the number of fabric layers. In the 

case where a test condition was repeated (two or more replicates), an average speed was 

used to simulate a nominal test result. 

4. The calculated versus observed energy absorption was then compared for all tests of the 

same fabric to judge if the material code was acceptable or not. Iterations were made 

until acceptable correlation was obtained for both fabrics. The iterations mainly included 

the changes in internal formulation of the SRI material model fabrics and also LS-DYNA 

control parameters for contact representation between the fabric and the projectile. 

2-1
HON

FE Models

ASU FE

FE Model

ASU Tests SRI Fabric

 Matl Model

Kevlar / Zylon

 Matl Input

LS-DYNA

 Deck

Stock

 LS-DYNA

User-def

 LS-DYNA

Contact

 parameters

Other LS-DYNA

 parameters

NASA

Tests

Ball. Test

parameters

NASA

Tests

Results

Results

N

Y

Task 4 Correlation

OK?

FIGURE 2-1. OVERALL PROCEDURE FOR THE NUMERICAL SIMULATION OF 

BALLISTIC TESTS 

TABLE 2-1. FABRIC PROPERTIES 

Zylon AS 

Poly-benzobisoxazole 

Kevlar-49 

P-Aramid 

Light Heavy Standard

Volume Density (g/cm3) 1.54 1.54 1.44

Yarn Denier (measured) (g/9km) 500 1500 1490 

Yarn Linear Density (mg/cm) 0.556 1.654 1.656 

Yarn Count (yarns/in) 35 × 35 17 × 17 17 × 17 

Yarn Count (yarns/cm) 13.8 × 13.8 6.7 × 6.7 6.7 × 6.7 

Fabric Ply Thickness (mm) 0.21 0.28 0.28 

Fabric Areal Density (g/cm2) 0.01575 0.0223 0.02275

Degree of Crimp Warp Yarns (%) 3.1 2.2 1.1 

Degree of Crimp Fill Yarns (%) 0.6 0.9 0.8 

2.3 FINITE ELEMENT MODEL DESCRIPTION.

The ballistic test specimen(s) consisted of a thick steel cylinder welded on a plate, as shown in 

figure 2-2. For each individual test, the composite fabric was wrapped around this cylinder. A 

local window was machined out of the cylinder to provide access for the fabric wrap from the 

inside of the cylinder. The whole setup was inclined 15 degrees with respect to the horizontal 

2-2
plane such that the projectile could be shot directly into the exposed wrap area without 

interference from the rest of the cylinder. 

FIGURE 2-2. BALLISTIC TEST SETUP AT NASA GRC 

In the test samples, the composite fabric wraps were flat at the local opening of the cylinder, 

since there was no physical support to force the wraps to follow the curvature of the cylinder. In 

the finite element model, the shell simulating the fabric wraps follows the curvature of the 

cylinder even at the open area, as shown in figure 2-3. This is more representative of an actual 

engine fan containment structure where the fabric layers are always supported by a thin metallic 

or composite support layer. However, further comparison of the results with flat and curved 

modeling of the fabric at the opening did not reveal considerable differences. 

2-3
FIGURE 2-3. BALLISTIC TEST FINITE ELEMENT MODEL 

The following nomenclature was used to identify the fabric modeling used: 

Total number of fabric layers simulated, n = k × m

Where k is the number of shell-element layers physically modeled, and m is the number of 

composite fabric layers simulated per each shell. For example, the simulation 2 × 4 means that 

there was a total of eight layers of fabric wrapped around the cylinder during the test, and that 

the finite element modeling was done with two shell-element layers each representing the 

thickness and properties of four physically wrapped layers. 

Figure 2-4 schematically illustrates different ways a test case could have been simulated. For the 

example chosen, there are eight layers of fabric wraps that are physically tested. This test can be 

simulated theoretically by one of the combinations satisfying the relationship: k × m = 8, 

namely, 1 × 8, 2 × 4, 4 × 2, or 8 × 1. The primary focus of this program was to be able to 

2-4
simulate all the fabric layers by a single shell-element layer (1 × 8 in the given example), 

representing the total thickness of the pack. It was assumed that the fundamentals of the material 

formulation was adequate for simulating a single fabric layer as well as multiple fabric layers, as 

long as the total thickness is well represented. In this program, both Kevlar and Zylon ballistic 

tests were, therefore, simulated by a single layer shell element, representing the total number of

fabric layers tested (1 × n). There are obvious advantages of single shell layer modeling since it 

provides a computationally inexpensive way to simulate overall behavior of the containment 

system. It avoids computational complications mainly related to contact interactions between 

individual fabric layers when all layers are explicitly modeled as separate shells, especially if the 

large number of fabric layers typically used in the fan containment design systems is taken into 

consideration (>30 layers in some cases). On the other hand, the single layer modeling by nature 

does not have the capability to predict the number of penetrated (or failed) versus nonpenetrated 

fabric layers. In the engine containment design problems, this information is usually valuable 

because it relates to the available margin of the containment system. To investigate the current 

capability of modeling multiple shells within the LS-DYNA limitations and computational 

constraints, the Zylon ballistic tests were also modeled with remaining combinations, namely 

multiple shell-element layers, representing 1 to 24 layers of fabric each. 

Example: 8 layers of fabric tested

Analytical thickness of each layer = t

Total thickness =8t

(1 x 8)

(# shells x fabric layers simulated per shell)

8t

8t/2

(2 x 4)

4t

4t/2

(4 x 2) 2t

2t/2

(8 x 1)

 t

t/2

Sim

ulati

ons possibiliti

e

s

Fabric wrap

Ring

FIGURE 2-4. SCHEMATIC OF THE FABRIC SIMULATION TECHNIQUES 

A common finite element practice is to model the shell elements at the mid-plane of the physical 

thin member (fabric in this case). Appropriate gaps between two consecutive shells and also 

between the ring and the first neighboring shell should then be provided for accurate contact 

computations, as shown in figure 2-4. Due to these required gap adjustments, the finite element 

model was unique for each simulated case. 

2-5
It is important to note that when a shell-element layer is used to represent a fabric layer, the 

thickness of the shell is not the physical measured thickness of the fabric. The equivalent 

thickness, which is obtained by dividing the fabric areal density (g/cm2 or lb/in2) by the volume 

density from the manufacturer (g/cm3 or lb/in3

), is more appropriate for numerical calculations. 

In addition, due to the fact that in a woven fabric structure, only the fibers along the axis of 

loading will react to the external load, only half of the fibers should be involved in the structural 

calculations. The shell-element thickness used in the model (analytical thickness) is, therefore, 

half of the calculated equivalent fabric thickness. Throughout this program, the Kevlar and 

Zylon shell-element analytical thicknesses were 0.00311 in. (0.0079 cm) and 0.00201 in. (0.0051 

cm), respectively. Due to the fact that this analytical thickness adjustment will also reduce the 

weight of the modeled fabric, the density of the fabric was also adjusted in the analysis by 

multiplying by a factor of two in order to capture the representative dynamic behavior. 

2.4 ANALYSIS TOOLS.

The same version of the LS-DYNA was used throughout this project, unless otherwise specified. 

This type of analysis, which involves high nonlinearities, failure, and contact interactions, is 

sensitive to program version, the computer platform used, the number of microprocessor(s) or 

type(s), and the operating system. A brief discussion on the effects of these parameters is given 

in section 6. To ensure consistency of the results, the following parameters were intentionally 

kept constant during this project: 

• Standard LS-DYNA file: ls960_s_447_hp_102; LS-DYNA Version 960, Revision 477 

• HP8000 Unix machines, with operating system Version 10.2, single processor, and single 

precision 

2.5 ANALYSIS RESULTS.

The analysis matrices followed to simulate the ballistic test results are given in tables 2-2 and 

2-3 for Kevlar and Zylon material, respectively. As outlined previously, only the single shell 

layer modeling was performed for Kevlar (first row of table 2-2), whereas single and multiple 

shell layer modeling were investigated for Zylon. After iterations, per figure 2-1, the final 

results obtained for both fabric materials were as reported in tables 2-2 and 2-3. These results 

were obtained using the latest version of the material model code dated 10-08-2002. The 

material model code was then kept unchanged throughout the rest of the project, including work 

conducted in task 4. Minor adjustments to the user-input time constant parameter were made to 

obtain the best correlation possible to the overall test results. The specifics of the material time 

constant are discussed by SRI in Part 3 of this report [2]. The optimal value of this parameter for 

Kevlar and Zylon was 0.008 and 0.002, respectively. Once the optimal values were determined, 

they were kept constant throughout the analyses performed in tasks 3 and 4. The user-defined 

material input decks are given in appendix A. 

2-6
TABLE 2-2. ANALYSIS MATRIX AND SUMMARY OF BALLISTIC TEST SIMULATION 

RESULTS FOR KEVLAR 

Kevlar Ballistic Tests 

No. of 

Layers 1 2 4 8 16 24

Percent 

Energy 

Absorbed 

11.0 

11.6 

34.6 

36.6 

10.0 

11.9 

16.6 

17.1 

20.4 

37.9 

47.4 

55.9 

69.5 

78.3 

LS-DYNA Simulations 

k × m 1 × 1 1 × 2 1 × 4 1 × 8 1 × 16 1 × 24 

Model ID Model 231_1 Model 232_2 Model 222_4 Model 228_8 Model 230_16 Model 229_24

Prediction 19.2% 56.6% 9.5% 18.6% 43.2% 73.5%

2 × 2 2 × 4 2 × 8 2 × 12 

* * * *

* * * *

4 × 1 4 × 2 4 × 4 4 × 6 

* * * *

* * * *

8 × 1 8 × 2 8 × 3 

* * *

* * *

16 × 1 12 × 2 

* *

* *

24 × 1 

*

*

Notes: 

k × m = no. of shells × no. of fabric layers simulated per shell. Prediction = predicted percent energy absorbed. 

* = simulation not performed. 

2-7
TABLE 2-3. ANALYSIS MATRIX AND SUMMARY OF 

BALLISTIC TEST SIMULATION RESULTS FOR ZYLON 

Zylon Ballistic Tests 

No. of 

Layers 2 4 8 16 24

Percent 

Energy 

Absorbed 

N/A 12.9

15.6 

21.4 

21.6 

23.2 

25.8 

52.2 100.0

100.0 

LS-DYNA Simulations 

k × m --- 1 × 4 1 × 8 1 × 16 1 × 24 

Model ID --- model122_4 model128_8 model130_16 model129_24

Prediction --- 8.3% 19.4% 65.8% 99.0%

2 × 2 2 × 4 2 × 8 2 × 12 

model122_2 model128_4 model130_8 model129_12

9.9% 17.0% 48.0% 98.6%

4 × 1 4 × 2 4 × 4 4 × 6 

model122 model128_2 model130_4 model129_6

9.3% 18.0% 44.4% 98.9%

8 × 1 8 × 2 8 × 3 

model128 model130_2 model129_34

16.8% 36.6% 68.5%

16 × 1 12 × 2 

model130 model129_2

33.3% 55.2%

24 × 1 

model129

46.1%

Note: 

k × m = no. of shells × no. of fabric layers simulated per shell.

Prediction = predicted percent energy absorbed. 

A detailed summary of the test results and the analytical predictions is also given in appendix B. 

As already mentioned in section 2.2, some of the ballistic tests were repeated up to four times, 

resulting in some scatter in the results, which is expected from this type of experimental work. 

Part of this scatter is due to slightly different initial conditions for the individual tests. For 

example, there are three replicas for the eight-layer Kevlar test. Each of the tests has its own 

measured projectile mass and initial velocity, contributing to variation in impact energy values, 

and, therefore, affecting the exit velocity and energy. The initial velocity variation and the 

projectile mass variation in this example were 11 percent and 1 percent, respectively. The 

2-8
resulting exit velocity, exit energy, and absorbed energy variations were 10, 20, and 7 percent, 

respectively. 

On the analytical side, it was not practical to simulate individual tests by adjusting the initial 

velocity and projectile mass; therefore, a single analysis was performed at a nominal initial 

kinetic energy level. In most cases, the initial test velocities were then updated by NASA GRC 

(due to further detailed data processing) after the completion of the simulation analysis. This 

resulted in further discrepancy between the test initial conditions and the corresponding 

simulation initial condition. For the example chosen, the simulation kinetic energy was 

deviating from individual test kinetic energies by 5 to 20 percent. To be able to compare the 

results from individual tests to a single nominal analysis result, the following adjustment was 

made: the predicted exit kinetic energy was scaled by the ratio of the initial energy of the 

analysis to the individual test initial energy. In this way, an exit kinetic energy prediction 

corresponding to each individual test condition was estimated for a more realistic comparison. 

Figure 2-5 is reproduced from the NASA GRC test data to show the trends obtained during the tests. 

The energy absorbed by the fabric layers increased as the number of layers increased for all three 

fabrics tested. The material model creation and the analytical simulations were only conducted for 

light Zylon AS and Kevlar 49; the heavy Zylon was not studied. Zylon performed slightly better 

than Kevlar, especially for the cases having more than eight layers. The heavy Zylon outperformed 

both Kevlar and light Zylon for any number of layers. It should be noted that the areal weight of the 

heavy Zylon and Kevlar 49 were similar but the light Zylon AS was significantly less. 

0

20000

40000

60000

80000

100000

120000

0 5 10 15 20 25 30

Number of Layers

Energy Absorbed (in-lb)

Kevlar49

Zylon AS

Zylon AS, heavy

Linear (Zylon AS, heavy)

Linear (Zylon AS)

Linear (Kevlar49)

FIGURE 2-5. BALLISTIC TEST RESULTS (NASA GRC TEST DATA) 

2-9
2.5.1 Kevlar Ballistic Test Simulations.

Table 2-2 also summarizes the percent energy absorbed during the simulation as well as the 

particular model used for reference (single shell-layer modeling only, 1 × m). The predicted 

percent energy absorption can be compared to observed energy absorption for each test given in 

table 2-2. The compilation of the analysis models and the results are also given in table B-1 of 

appendix B. Figure 2-6 shows the experimental results for Kevlar from figure 2-5, compared 

against the LS-DYNA simulation results. The overall correlation for the amount of energy 

absorbed was found to be acceptable for the range investigated. The energy absorption is a 

measurable parameter that can be used to judge the success of the simulation. However, to make 

a thorough judgment of the material modeling capability, other parameters, such as velocity and 

deceleration histograms during the penetration process, are desirable. LS-DYNA has the 

capability to provide the change in these parameters during the event, as shown in the velocity 

histogram in figure 2-7. The current ballistic testing technology provides only the information at 

the beginning and end of the event, and no measurements are available during the course of the 

event, to correlate with the analysis. Later in the program, some additional data processing work 

was performed by NASA GRC to obtain further position-time and deflection-time information 

on selected tests. Figure 2-8 shows an example where the position of the projectile was tracked 

on the high-speed camera throughout the event to better evaluate the overall behavior. Although 

this effort gave more information about the before and after impact conditions, there was not 

enough resolution during the impact portion for further comparison to analytical results. 

0

20000

40000

60000

80000

100000

120000

0 5 10 15 20 25 30

Number of Layers

Energy Absorbed (in-lb)

Kevlar 49 Test

LS_DYNA: 1 Shell Layer

Linear (Kevlar 49 Test)

Linear (LS_DYNA: 1 Shell Layer)

LS-DYNA analysis using single layer shell element (1 x n)

FIGURE 2-6. KEVLAR BALLISTIC TEST RESULTS VERSUS LS-DYNA PREDICTIONS 

2-10
y = -0.034x + 8.758

8.00

8.50

9.00

9.50

10.00

10.50

11.00

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90

Time (msec)

Velocity (in/sec *10-3)

Afte r pe rfora tion

Be fore impact

During impa c t

Linear (Afte r pe rfora tion)

Linear (Be fore impact)

y = 0.000x + 10.756

y = -10.755x + 11.41

R2

 = 1

Slope=Velocity= 10.755*1000/12 = 896 ft/sec

FIGURE 2-7. PROJECTILE VELOCITY HISTOGRAM DURING A 

16-LAYER KEVLAR SIMULATION TEST 

2 1

3

y = -10.827x + 7.8999

y = -10.686x + 11.387

y = -7.7964x + 4.8403

y = -8.738x + 9.670

R2

 = 1.000

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00

Time (msec)

Position (in)

Point 1 x (before impact)

Point 2 x (before impact)

Point 2 x (during impact)

Point 3 x (during impact)

Point 3 x (after perforation)

C.G. LS-Dyna (before impact)

C.G. LS_Dyna (during impact)

C.G. LS_Dyna (after perforation)

Avg. Slope=(10.827+10.686)/2= 10.756=10756 in/sec = 896 ft/sec

Slope=Velocity= 8.738*1000/12 = 728 ft/sec

Slope=Velocity= 7.796*1000/12 = 650 ft/sec

FIGURE 2-8. PROJECTILE POSITION HISTOGRAM DURING A 

16-LAYER KEVLAR BALLISTIC TEST 

LS-DYNA has more than the capability to predict the end result, it also provides the local and/or 

the overall deflection behavior during the event. Figure 2-9 shows the results from a 16-layer 

Kevlar test at the verge of the fragment penetration and the corresponding LS-DYNA analytical 

prediction. The deformed shape of the fabric and the interaction with the projectile can also be 

realistically simulated in addition to the energy absorption. More examples of the deformed 

shape comparisons are given in section 2.5.2, where the analytical results for Zylon are 

discussed. One particular piece of information that is useful to the engine containment designers 

2-11
is the maximum deflection of the fabric layers during the containment event, especially when the 

projectile is fully contained. This allows designers to adequately position the surrounding 

engine parts and accessories without safety concerns. An attempt was made to correlate the 

maximum deflection measured during a selected (16-layer Kevlar) test to the respective LSDYNA prediction. Figure 2-10 compares the analytical versus experimental deflections for the 

test case shown in figure 2-9. It was concluded that LS-DYNA is able to predict the maximum

fabric deflection reasonably well based on this limited data. 

FIGURE 2-9. A 16-LAYER KEVLAR BALLISTIC TEST RESULT 

VERSUS LS-DYNA DEFLECTION PREDICTIONS 

-3

-2

-1

0

1

2

3

-4 -3 -2 -1 0 1 2

x (in)

y (in)

Before Impact

At Perforation

LS-Dyna Before

Impact

LS-Dyna At

Perforation

FIGURE 2-10. ANALYTICAL VERSUS EXPERIMENTAL DEFLECTIONS 

FOR A 16-LAYER KEVLAR BALLISTIC TEST 

2-12
2.5.2 Zylon Ballistic Test Simulations.

Table 2-3 summarizes the percent energy absorbed during the Zylon test simulations. Similar to 

table 2-2, the first row of simulation is for single shell-layer modeling (1 × m). The analytical 

results are also compiled in table B-2 of appendix B. Figure 2-11 shows the experimental test 

results for Zylon from figure 2-5, compared against the LS-DYNA simulation results. Once 

more, the overall correlation for the amount of energy absorbed was found to be acceptable for 

the range investigated. Figure 2-12 shows the correlation data for both Kevlar and Zylon, for 

energy absorbed (normalized per total areal density of the fabric system). This normalized 

parameter is useful in comparing the performance of fabrics with different densities. It can be 

concluded from figure 2-12, for example, that for the same weight of the wrapped containment 

system, Zylon can absorb more energy than Kevlar. This type of comparison will be further 

discussed in section 3. Figure 2-12 shows that the predictions agreed well with the test results 

for systems with more than eight layers of fabric. But for one to four layers, the predictions 

deviated by more than 50 percent. 

0

20000

40000

60000

80000

100000

120000

0 5 10 15 20 25 30

Number of Layers

Energy Absorbed (in-lb)

Zylon AS Test

LSDYNA: 1 Shell Layer

Linear (LSDYNA: 1 Shell Layer)

Linear (Zylon AS Test)

FIGURE 2-11. ZYLON BALLISTIC TEST RESULTS VERSUS LS-DYNA PREDICTIONS 

0.00E+00

5.00E+00

1.00E+01

1.50E+01

2.00E+01

2.50E+01

3.00E+01

3.50E+01

4.00E+01

0 5 10 15 20 25 30

Number of Layers

Energy Absorbed / Areal Weight / # of layers

(in-lb / lb/in2

)x10^6

Kevlar 49

Zylon AS

Zylon AS, Heavy

LSDYNA Zylon AS

LSDYNA Kevlar 49

FIGURE 2-12. NORMALIZED BALLISTIC TEST RESULTS VERSUS 

LS-DYNA PREDICTIONS 

2-13
Table 2-3 also includes the results with multiple shell modeling (k × m) to simulate the actual 

fabric layers. The results indicate that for all fabric configurations (4 to 24 layers), the multiple 

shell-element modeling yields very similar results as the single shell-element modeling, when up 

to four shell-element layers are modeled. When more than four shell-element layers are used, 

the models failed to realistically simulate the test results. This is believed to be the result of

solution divergence, due to numerical instabilities and complicated contact interactions between 

multiple layers. This correlation trend is also graphically illustrated in figures 2-13 and 2-14, 

where it is shown that the prediction capability rapidly decreased for models with more than four 

shell-element layers. 

0

20000

40000

60000

80000

100000

120000

0 5 10 15 20 25 30

Number of Layers

Energy Absorbed (in-lb)

Zylon AS Test

LSDYNA: 1 Shell Layer

LSDYNA: 2 Shell Layers

LSDYNA: 4 Shell Layers

LSDYNA: 8 Shell Layers

LSDYNA: 16/12 Shell Layers

LSDYNA: 24 Shell Layers

Linear (Zylon AS Test)

Linear (LSDYNA: 1 Shell Layer)

FIGURE 2-13. ZYLON BALLISTIC TEST RESULTS VERSUS LS-DYNA 

PREDICTIONS WITH MULTIPLE-LAYER SHELLS 

0

20000

40000

60000

80000

100000

120000

4 8 16 24

Number of Layers

Energy Absorbed (in-lb)

Zylon AS Test

LSDYNA: 1 Shell Layer

LSDYNA: 2 Shell Layers

LSDYNA: 4 Shell Layers

LSDYNA: 8 Shell Layers

LSDYNA: 16/12 Shell Layers

LSDYNA: 24 Shell Layers

FIGURE 2-14. EFFECT OF MULTIPLE-LAYER FABRIC MODELING 

2-14
In terms of the overall deflection behavior, some prediction-to-test comparisons are given in 

appendix C for the single shell-layer modeling technique. Similar to Kevlar, the Zylon 

deflection shape predictions matched very well against the high-speed camera test data. Figure 

2-15 summarizes the effect of single- versus multiple-layer modeling techniques on deflection 

shape predictions. Similar to the energy absorption conclusion, a four-layer Zylon fabric system

can be represented equally well with either one single shell-layer simulating four fabric layers (4 

= 1 × 4) or four shell layers simulating one fabric each (4 = 4 × 1). Similarly, figure 2-16 

summarizes the results of single- and multiple-layer modeling to simulate a 12-layer Zylon 

system. Once again, 1 × 24 and 4 × 6 models provided similar results and were successful in 

simulating the test behavior, whereas a 24 × 1 model failed to simulate the test behavior and 

diverged from the ideal representation towards the end of the simulation. 

FIGURE 2-15. DEFLECTED SHAPES WITH SINGLE- VERSUS MULTIPLE-LAYER 

FABRIC MODELING (FOUR FABRIC LAYERS) 

2-15
FIGURE 2-16. DEFLECTED SHAPES WITH SINGLE- VERSUS MULTIPLE-LAYER 

FABRIC MODELING (24 FABRIC LAYERS) 

2-16
LS-DYNA also keeps track of the kinetic energy of the projectile during the impact event. 

Figures 2-17 and 2-18 provide the time histories of the kinetic energy for the previously 

mentioned 4-layer and 24-layer Zylon analyses, respectively. For all analyses that were 

successful in predicting the correct energy absorption and the overall deflections, the kinetic 

energy curves were similar. Whereas for the 24 × 1 case, the kinetic energy curve reflects the 

early failure, therefore supporting the poorly correlating result. 

96000

98000

100000

102000

104000

106000

108000

0.0 0.1 0.2 0.3 0.4 0.5 0

Time (msec)

Projectile Kinetic Energy (in-lb)

.6

ZYLON 1 x 4

ZYLON 4 x 1

FIGURE 2-17. KINETIC ENERGY WITH SINGLE- VERSUS MULTIPLE-LAYER 

FABRIC MODELING (FOUR FABRIC LAYERS) 

0

20000

40000

60000

80000

100000

120000

0.0 0.5 1.0 1.5 2.0

Time (msec)

Projectile Kinetic Energy (in-lb)

ZYLON 1 x 24

ZYLON 4 x 6

ZYLON 24 x 1

FIGURE 2-18. KINETIC ENERGY WITH SINGLE- VERSUS MULTIPLE-LAYER 

FABRIC MODELING (24 FABRIC LAYERS) 

In conclusion, regardless of the number of total fabric layers to be simulated, the multiple-layer 

modeling techniques, using up to four layers, provided promising results for both energy 

2-17
absorption and the overall deflection behavior. Increasing the number of fabric layers caused 

divergence from the test data. 

2.6 CONCLUSIONS.

The conclusions drawn from the task 3 results are summarized as follows: 

• The new user-defined material model was successfully compiled within the LS-DYNA 

code. The same model is able to represent both Kevlar and Zylon material behavior, with 

separately provided material-specific constants. The model formulation is based on 

actual material data and provides a more realistic representation of the fabric behavior. 

• The new material model is independent of the number of fabric layers, therefore 

providing the flexibility to model single- or multiple-fabric layers. 

• Acceptable correlation was obtained between the simulation results and the ballistic test 

results for both Kevlar and Zylon using a single shell-element layer simulating all the 

fabric layers. Both the energy absorption and the overall deflection behavior of the fabric 

systems were successfully simulated. The relative simulations are able to depict the 

ballistic strength differences between Zylon and Kevlar. 

• Promising successful analyses to test correlations are obtained when up to four layers of 

shell elements are used to model all fabric layers. Although good trends were observed 

up to four shell-element layers, the prediction capability was not satisfactory for 

modeling techniques using more than four shell-element layers. More work is needed to 

explore the limitations of modeling techniques involving high numbers of shell layers. 

• The results are valid for the versions, the computer hardware, and the LS-DYNA 

parameters used. 

• The mesh density was kept constant (0.25 inch (6.4 mm)) during this program. The 

possible effects on the results were not investigated. 

2-18
3. NUMERICAL SIMULATION OF ENGINE FAN BLADE-OUT TEST (TASK 4).

3.1 OBJECTIVE. 

The primary objective of this task was to validate the Kevlar and Zylon material models 

developed under this research program for use in LS-DYNA fan containment analyses. 

3.2 ANALYTICAL PROCEDURE.

To achieve the above objective, Honeywell simulated an actual engine fan blade-out test using 

the material model and the analysis techniques developed during task 3 of this program. 

Figure 3-1 schematically illustrates the overall process followed during the execution of task 4. 

The detailed steps for the analytical efforts are given below. 

Engine

FE Model

SRI Fabric

 Matl Model

Kevlar / Zylon

 Material Input

LS-DYNA

 Deck

Baseline

 LS-DYNA

User-defined

 LS-DYNA

Contact

 parameters

Other LS-DYNA

 parameters

AS907

Test

Results Compare

Task 3

FIGURE 3-1. OVERALL PROCEDURE FOR THE ENGINE 

FAN BLADE-OUT SIMULATION 

• A Honeywell turbofan engine model was chosen for validation of the techniques 

developed in task 3. The fan blade-out development test for this engine was conducted 

during 1999. A baseline 1999 LS-DYNA analysis predicted the results of this test using 

approximations related to the fabric material behavior due to a lack of material data. 

• The composite fabric material model code, developed in previous tasks in this program, 

was used in the task 4 analyses to simulate the engine fan containment. The typical LSDYNA input deck included the model file (finite element nodes and elements), the usercontrolled material input parameters (see appendix A), the contact file defining the 

contact types to be used, and the LS-DYNA control parameters from task 3. 

3-1
• The analytical predictions were then compared against the engine fan blade-out test 

results. The test results were captured in the form of engine hardware pictures taken 

before, during, and after the test, which allowed qualitative comparison of the ability of 

LS-DYNA to predict various failure modes against actual engine test results. 

3.3 FAN BLADE-OUT TEST RESULTS.

During the development of the new Honeywell AS907 turbofan engine, a containment test was 

conducted on a full-scale engine to verify the fan blade-out containment and related design 

features prior to the official qualification test required by the FAA certification authorities. An 

overall view of this engine is shown in figure 3-2. The AS907 fan containment design 

incorporates composite fabric wraps with material properties equivalent to Kevlar. The number 

of layers required to adequately contain a possible fan blade separation were calculated using 

empirical Kevlar penetration design curves based on Honeywell experience with similar designs. 

The diameter of the AS907 containment system was comparable to the diameter of the ballistic 

test specimen in this project. 

FIGURE 3-2. OVERALL VIEW OF THE HONEYWELL MODEL AS907 

TURBOFAN ENGINE 

During the engine fan blade-out containment test, a fan blade was intentionally released by 

artificial means while the engine continued to operate for 15 seconds after the event. The engine 

was then shutdown by the operator. The released blade penetrated the containment system, but 

stopped between the fan housing and the fabric wraps. Figure 3-3 shows a still frame 

photograph of particular interest from the high-speed motion picture taken during the test in 

which just the tip of the intentionally released fan blade is shown sticking out of the last fabric 

layer. Figure 3-4 shows photographs of the disassembled fan housing immediately after the test 

with the intentionally released blade at its resting position. The airfoil had penetrated the 

containment system up to approximately mid span, but the heavier root section, including the 

platform and the shank, was contained within the fabric wraps. The blade tip was damaged and 

bent due to the resulting impact. Although this containment test stopped the blade, the design 

3-2
was modified for certification test by increasing the number of layers by approximately 15 

percent to achieve additional safety margin. As a result, during the official AS907 certification 

test, the intentionally separated fan blade was entirely contained within the fabric containment 

system. 

FIGURE 3-3. FRAME FROM A HIGH-SPEED MOVIE OF THE AS907 FAN 

BLADE-OUT TEST 

FIGURE 3-4. AS907 FAN CONTAINMENT HOUSING FOLLOWING BLADE-OUT TEST 

3-3
3.4 ANALYSIS RESULTS.

3.4.1 Baseline (1999) Analysis. 

During design, before execution of the above engine test, an LS-DYNA analysis was conducted 

to guide the containment design incorporated into the test engine and also to predict the possible 

outcome of the test. The objective of the analysis was not only to predict the containment 

capability of the composite fabric system but also to predict the performance of other design 

features contributing to the success of such complex designs. Therefore, this analytical model 

not only included the containment hardware but also a good portion of the front section of the 

engine to study blade-to-blade interactions, shaft dynamic motion and interaction with support 

structures, and the dynamic loads transmitted to the remaining structures and to the engine 

mounts, etc. As a result, as shown in figure 3-5, this model was very large and cumbersome to 

use in the present fabric containment study. A subportion of the model was extracted to simulate 

blade release and the containment event only, as also shown in figure 3-5. This reduced model 

was already confirmed in 1999 to have adequately captured the physics and boundary conditions 

of the full model for the containment portion of the problem. The reduced model includes two 

blades (one released and one trailing) and the fan containment hardware, with three shell layers 

representing all the fabric layers as well as other layers, such as the metallic housing, abradable 

coating, and honeycomb and graphite epoxy shell. 

FIGURE 3-5. LS-DYNA MODEL FOR FAN BLADE-OUT CONTAINMENT ANALYSIS 

3-4
To establish a proper baseline, the 1999 fan blade containment analysis was repeated again with 

the current version of the program and current computer hardware. The result is qualitatively 

presented in figure 3-6, where the picture shows the final condition of the hardware when the 

containment event was over (5 milliseconds after blade release). When compared to actual 

posttest engine hardware photographs, the predictions were found to be on the optimistic side. 

The fabric layers were not perforated and the containment system did not show any signs of 

distress. Also, the blade deformation during the impact did not correlate well with the posttest 

hardware observations. 

FIGURE 3-6. 1999 BASELINE FAN CONTAINMENT ANALYSIS—OVERALL VIEW

The following specific features of this model should be noted: 

• The mesh density of the fabric layers was considerably coarser than the ballistic model 

mesh density, namely ~0.750 inch (19 mm) compared to 0.250 inch (6.4 mm). 

• Three shell-element layers were used to represent all the fabric layers. This configuration 

worked well within LS-DYNA, without any contact-related instabilities. The coarse 

mesh density might have helped for the possible contact issues. 

• Kevlar was modeled with a standard elastic-plastic material model, which is mainly used 

for metallic materials. This is a very rough assumption because the composite fabrics do 

not behave like metallic materials. 

• The physical fabric thickness was used as the basis for the shell elements representing the 

fabric. This is not exactly correct, for reasons discussed in section 2.3. 

• The fan blade was modeled with coarse shell elements. It should be noted that the 

projectile in the earlier ballistic test simulation was modeled with solid elements with a 

fine mesh density. 

3-5
Nevertheless, except for the optimistic fabric behavior and the unrealistic blade deformation, the 

other aspects of the containment event were simulated quite well. Figure 3-7 compares the 

results of the baseline analysis against actual hardware damage in terms of the blade-housing 

interaction, blade final orientation within the sacrificial containment hardware, and secondary 

damage created by the blade. 

FIGURE 3-7. 1999 LS-DYNA BASELINE FAN CONTAINMENT ANALYSIS— 

PREDICTED INTERNAL DAMAGE 

3.4.2 1999 Model With New Kevlar Material Formulation.

In the next step of the investigation, the baseline 1999 analysis was repeated, but this time the 

fabric material model developed during this research program was introduced to replace the 

1999 material model. As discussed in section 2, this material model was used and calibrated 

with the equivalent half-thickness concept; therefore, the fabric shell thicknesses were also 

updated for consistency. Other features such as fabric mesh density, shell blade elements, 

number of shell layers modeled (three), and legacy contact types were not modified. Figure 3-8 

summarizes the results with the isolated effect of the material model and compares the resulting 

predicted hardware damage to the actual engine test results. Incorporation of this new material 

model had a large effect on the overall outcome, when compared with the results from the 

baseline analysis. The blade was estimated to completely rip the fabric layers, making the 

prediction more conservative with respect to the actual test. It is also worth noting that the 

multishell modeling (three shell-element layers) was still successful. 

3-6
FIGURE 3-8. 1999 LS-DYNA MODEL ENHANCED WITH NEW

KEVLAR MATERIAL FORMULATION 

3.4.3 Optimized Methodology and New Kevlar Model.

In the final phase of the engine fan blade-out simulations, other modeling techniques developed 

in the earlier calibration work were also introduced in the analysis in addition to the new 

material model. The LS-DYNA model was modified to incorporate a single-layer shell 

representing all fabric wraps, since this method was shown to be the most consistent during the 

earlier ballistic simulation work. The mesh density was also refined to be consistent with the 

ballistic test simulation models. The blade was also modeled more realistically using solid 

elements. Finally, the new advanced contact types (SOFT=2), which gave the best results during 

the ballistic test simulations, were also incorporated into the analysis. As shown in figure 3-9, 

the predictions matched much better with the overall behavior seen in the engine test. 

3-7
FIGURE 3-9. LS-DYNA ANALYSIS WITH OPTIMIZED METHODOLOGY 

AND NEW KEVLAR MODEL 

It was predicted that the fabric layers would be punctured by the blade tip at the front portion of 

the containment system and that the blade tip would also be exposed, as it was in the engine test. 

The damage caused by the heavy root portion of the blade at the aft section of the fabric system

was also realistically captured. Predictions obtained with a coarser fabric mesh density similar 

to the 1999 model are also shown in figure 3-9. Comparison of the predictions with the two 

mesh densities suggests that the coarser mesh model produces more optimistic results. This is 

also consistent with the results of the 1999 analysis. Predicted damage to the internal (nonfabric) 

components of the containment system is shown in figure 3-10. The extent of damage made by 

the blade, the size of the opening before reaching the fabric layers, and the location of the impact 

of the heavy blade shank with the housing wall were realistically captured. Similarly, the 

deformed posttest shape of the blade was successfully predicted, including features such as the 

tip section curved opposite to the direction of rotation, the tip leading edge and the shank trailing 

edge severely damaged, and the platform severed by the impact of the trailing blade. This type 

of detailed information permits the containment designer to consider other aspects of the fan 

containment problem, such as support structure integrity, and blade design. 

An attempt was made to replace the single-layer fabric model in figure 3-10 with a three-layer 

model to duplicate the results. This could not be achieved because of premature analysis 

termination due to extensive element distortion and contact instabilities. The software program

manufacturer was consulted in an attempt to resolve these issues, but these efforts were 

unsuccessful. The reasons for failure of the multilayer modeling capability compared to the 

earlier successful ballistic test simulations and the 1999 modeling are not well understood. It is 

speculated that the very fine mesh density used in this complicated model could have negative 

effects. No further work was performed to investigate this effect. 

3-8
FIGURE 3-10. LS-DYNA ANALYSIS WITH OPTIMIZED METHODOLOGY 

AND NEW KEVLAR MODEL—PREDICTED INTERNAL DAMAGE 

As already discussed in section 3.3, although the containment system stopped the blade during 

the AS907 engine development test, the design was later modified for the upcoming official 

certification test by increasing the number of layers by approximately 15 percent for additional 

safety margin. As a result, during the AS907 fan blade-out certification test, the intentionally 

separated blade was entirely contained within the fabric system. An updated analysis with the 

AS907 design changes incorporated was also performed with LS-DYNA, and the new results 

correlated well with the final engine qualification test results. 

3.4.4 Fan Containment Predictions With Zylon.

To study differences in behavior between Kevlar and Zylon materials in a fan containment 

environment, the Kevlar material properties used in section 3.4.3 were replaced by properties for 

Zylon material. However, there were no fan blade-out containment test results using Zylon to 

make a thorough comparison. Nevertheless, the analytical comparison results using Zylon have 

great value in determining the ability of the analysis to reflect the conclusions drawn from the 

ballistic tests (i.e., Zylon has equal or slightly better capabilities) in a more complex containment 

environment. No other geometrical changes were made in the model, and the number of layers 

3-9
simulated was kept the same, except the total thickness of the Zylon fabric wraps was properly 

simulated. Comparison of the Zylon and Kevlar analysis results shown in figure 3-11 indicates 

that a similar containment capability (based on the total amount of energy absorbed) is predicted 

when Zylon is substituted. In general, a similar level of containment was predicted with both 

materials in terms of retaining the separated blade within the containment system; whereas some

details were observed to be different. For example, in a manner consistent with the ballistic test 

results, the slightly higher properties of Zylon prevented local penetration of the separated blade. 

But at the same time, higher hoop loads developed within the fabric layers, causing more axial 

ripping of the layers, without total release of the blade. It should be noted that even if the 

containment capability of Kevlar and Zylon is the same for this design (considering a similar 

number of fabric layers for both materials), Zylon offers a substantial weight reduction because 

of its 30 percent lower density when comparing the Kevlar 49 (1490 Denier, 17 × 17 mesh) to 

the Zylon (500 Denier, 35 × 35 mesh) used in the analysis. 

FIGURE 3-11. LS-DYNA PREDICTIONS WITH KEVLAR AND ZYLON MATERIAL 

3.5 CONCLUSIONS.

The conclusions drawn from the task 4 results are summarized as follows: 

• An engine fan blade-out event was successfully simulated using the fabric material 

models and developed analytical methodologies. 

3-10
• Acceptable correlation was obtained between the simulation results and the engine 

containment test results, using the new Kevlar material model and the single shell-layer 

modeling technique. 

• Prediction capability was significantly improved with the new material model and the 

associated modeling techniques, with respect to the previously used (1999) methodology. 

• In spite of successful results during the ballistic test simulations, further analytical 

enhancement with multilayer modeling was not possible, due to numerical instabilities. 

• Comparison of Kevlar and Zylon capabilities within the same containment design 

revealed containment results consistent with the ballistic test results trends. For the same

number of fabric layers, Zylon offers weight reduction possibility if it is used in lieu of

Kevlar. 

• The mesh density was kept constant during the program, but the possible effects on the 

results were not investigated. Further investigation of the effects of mesh sensitivity, 

contact parameters, and multilayer numerical instabilities are recommended. 

3-11/3-12
4. GENERIC CONTAINMENT MODEL. 

4.1 OBJECTIVE.

One of the deliverables of this research project was to build and provide a Generic Containment 

Finite Element Model for Kevlar or Zylon wrap materials. The purpose of this model was to 

provide LS-DYNA users with generic guidelines for modeling composite fabric wraps in impact 

containment-related applications. 

4.2 BACKGROUND.

During the planning stage of this project, specifics of the generic model were not defined but 

were left to the participants of the project, depending upon the outcome of the previous tasks. 

One possibility considered was to build a model of a simplified engine containment system, 

including fabric layers, a metallic support housing, and a generic blade as the projectile. After 

completion of task 4, it was concluded that this type of problem was too complex for the purpose 

of initiating typical LS-DYNA users to fabric-related impact simulations. Another downfall of a 

fictitious engine containment model was a lack of experimental test data to verify the accuracy of 

predictions that potential users may obtain by experimenting with various parameters. 

Therefore, it was decided, in principle, to provide a complete tool, including the numerical 

model and the test results, which will give users the possibility to study and calibrate their own 

analytical systems. The only comprehensive fabric experimental test data available to date that 

can be used to support analytical predictions is the ballistic tests performed by NASA GRC 

under this research program. Therefore, it was decided to electronically provide the LS-DYNA 

finite element models (refer to section 2.3) to satisfy the requirements of the Generic 

Containment Model. Potential users will be able to run these models, which are already set up 

with appropriate materials, contact algorithms, boundary conditions, etc., with their respective 

software versions, operating systems, and computer platforms, to observe any variations with 

respect to the results already reported herein. Section 6 gives a brief discussion of the variations 

in the results that can be experienced using LS-DYNA, depending on the contact types, 

processor types, and computer platforms. This discussion, together with the ballistic test 

simulation model, will guide the users to experiment with the simulations, keeping always in 

sight the corresponding experimental results. 

4.3 GENERIC MODEL FILES.

The computer files constituting the generic containment model are included in the CD-ROM 

version of this report. A list of the files and their descriptions is given below: 

a. zylon_1x4.input: This is the complete LS-DYNA input deck, including the following: 

• Baseline LS-DYNA control cards used in the current study. 

• Finite element nodes and elements simulating the four-layer Zylon ballistic test. 

One layer of shell elements was modeled to simulate four layers of fabric (1x4). 

4-1
• User material input for Zylon (see appendix A) compatible with the developed 

fabric material model. Kevlar material input is also included. The user can 

convert this model to an alternative model for Kevlar simulations by switching to 

the Kevlar properties instead of Zylon (shell thickness should then be updated 

accordingly). The material properties for the steel components are also provided 

in the input file. 

• Shell thickness definition for four-layer Zylon. For Kevlar analyses, change the 

thickness to the appropriate four-layer Kevlar thickness. 

• Definition of parts within the model. 

• Contact types (cards) between defined parts. 

b. zylon_1x4.results: This is the directory containing the output files of the analysis 

performed using zylon_1x4.input. These results were obtained using the following: 

• LS-DYNA code (before the user-defined material compilation): ls960_s_447_hp_102 

• LS-DYNA version 960, revision 477 

• HP8000 Unix machines, with operating system version 10.2, single processor, and 

single precision. 

c. ansys_model_1x4.db: This is the ANSYS model defining the geometric configuration of 

the ballistic test (single shell model). Geometry is available for further modifications to 

zylon_1x4.input, if desired. This also includes bare finite element model (nodes and 

elements) but not the control cards, contact cards, and part definitions. This model is 

required if other thicknesses for the shell elements (rather than the thickness provided 

above) are investigated. For example, for a desired 1x8 model, the total thickness of the 

shell can be easily modified in the input file, but the shell (fabric) mid-plane should be 

adjusted using this model file to provide the required gap between the shell surface and 

the support ring. 

d. zylon_4x1.input: This is the complete LS-DYNA input deck, similar to zylon_1x4.input, 

except the following: 

• Finite element nodes and elements simulating the four-layer Zylon ballistic test. 

Four layers of shell elements were modeled to simulate four layers of fabric (one 

fabric layer per shell, 4x1). 

• Shell thickness definition for one-layer Zylon, since all layers are explicitly 

modeled. For Kevlar analyses, change the thickness to appropriate single-layer 

Kevlar thickness. 

4-2
e. zylon_4x1.results: This is the directory containing the output files of the analysis 

performed using zylon_4x1.input. 

f. ansys_model_4x1.db: This is the ANSYS model defining the geometric configuration of 

the ballistic test (multiple shell model). Geometry is available for further modifications 

to zylon_4x1.input, if desired. This also includes bare finite element model (nodes and 

elements) but not the control cards, contact cards, and part definitions. This model is 

required if more shell layers are to be considered. For example, for a desired 8x1 model, 

this model can be modified to create extra shell layers. Depending on the number of 

fabric layers that each shell layer represents (8x1 or 4x2), the thicknesses and the shellto-shell or shell-to-ring gaps should be adjusted. 

g. fabric_material_code: This is the user-defined FORTRAN code defining the composite 

fabric (Zylon and Kevlar) material behavior. This file should be used in conjunction with 

the baseline LS-DYNA binary files to create a user-defined LS-DYNA executable. This 

file has been successfully used on the HP8000 Unix machines. For other platforms, 

changes to the FORTRAN program might be required to make it compatible with the 

specific compiler. 

h. read_me.txt: This file provides descriptions of the above files as well as the lessons 

learned that are discussed in the following section. 

4.4 GENERAL MODEL RECOMMENDATIONS.

The following recommendations provide the potential users of the Generic Containment Model 

with important tips about its capability and limitations. The lessons learned, obtained during the 

course of the project, are also included. 

a. The first thing that the user should do is to choose the appropriate version of LS-DYNA 

to compile the user-defined material model. The binary models can be downloaded from

a special FTP website maintained by the LS-DYNA supplier, Livermore Software 

Technology Corporation (LSTC). Not all of the LS-DYNA versions and revisions for 

different operating systems and platforms have a user-defined material capability. Please 

note that the example problems and the results were obtained with a specific computer 

setup, as noted in section 2.4. 

b. Next, the user should establish a baseline capability of the LS-DYNA version on the 

computer hardware available. If more than one computer platform is available to the 

user, it is strongly recommended to compare the results from one of the examples given, 

using each of the platforms. The results might be different, especially if the same

problem is analyzed using single processing or massive parallel processing. 

c. For a given computer platform, the largest source of variation in the results is due to the 

various contact algorithms available in LS-DYNA. The user should read the parametric 

study discussed in section 6 to learn more about the effects of the contact parameters. 

4-3
d. The same contact type and parameters were consistently used in all the simulation 

analyses as reported in the previous sections. Particularly in the fabric containment 

problem where a stiff projectile hit a low stiffness fabric, the successful contact 

parameters are hard to pick. Throughout the analyses of the current research, segmentbased SOFT=2 (automatic surface-to-surface contact type) was consistently used. 

Although other types of contact algorithms were initially considered, the best results for 

the simulation of the fabric impact problem were obtained by using this contact type. 

The SOFT=2 option causes the contact stiffness to be determined based on stability 

considerations, taking into account the time-step and nodal masses. This approach is 

generally more effective for contact between materials of dissimilar stiffness or dissimilar 

mesh densities. The best results were also obtained by using slave and master contact 

penalty factor (SFS and SFM) of 0.1. 

e. Another parameter that is closely related to the successful contact modeling is the timestep. With the contact setup of item d, a reduced time-step was concluded to give the 

most stable solution to the expense of longer computational time. The time-step scale 

factor TSSFAC in the *CONTROL_TIMESTEP control card was, therefore, set to 0.2. 

4-4
5. JOHNSON-COOK MATERIAL MODEL. 

5.1 BACKGROUND.

An additional investigation was done to compare the performance during impact analyses of the 

Johnson-Cook material model recently improved by LLNL and the conventional Honeywell 

metallic material model. The Johnson-Cook material model is specific to metallic materials used 

in impact applications. The containment system of the Honeywell engine described in section 

3.3 is conceptually a fabric wrap system, and the contribution of the metallic support layers are 

negligible. This system is, therefore, not adequate to investigate the performance of a material 

model designed for metallic materials. Since LLNL had already modeled a published impact test 

using its material formulation and obtained successful results, it was decided to use the same

analytical model to obtain comparative results using the alternative Honeywell material model. 

5.2 JOHNSON-COOK MATERIAL MODEL BY LLNL.

Several material models have been developed which can represent, with varying degrees of 

accuracy, the high-strain rate deformation response of materials to adequately formulate the 

penetration and perforation of aircraft and engine materials. Of these, the Johnson-Cook model, 

which was developed during the 1980s to study impact, ballistic penetration, and explosive 

detonation problems, is the most widely used, and it has been introduced in explicit finite 

element codes such as DYNA-3D and LS-DYNA. Its use for a particular material, however, 

requires determination of many material constants and also failure strain damage parameters. A 

LLNL report [3] describes the motivation for using the Johnson-Cook material model in 

simulations involving engine containment and engine debris mitigation on aircraft structures. In 

that report, experimental studies of the deformation and failure behavior of Ti-6Al-4V and 2024-

T3 aluminum at high strain rates and large strains were reported. The report also describes the 

generation of material constants for the Johnson-Cook strength model. A more recent report [4] 

describes the determination and validation of parameters for Ti-6Al-4V and 2024-T3 aluminum

that can be used in the failure portion of the Johnson-Cook material model. The governing 

equations representing the material behavior and the failure strain damage accumulation can also 

be found in the same references. 

5.2.1 Impact Analysis Using the Johnson-Cook Material Model.

The flow surface material constants and the failure parameters that were obtained by the 

Hopkinson bar test simulations are given in table 5-1 [3 and 4]. 

5-1
TABLE 5-1. JOHNSON-COOK MATERIAL CONSTANTS FOR Ti-6Al-4V 

DETERMINED BY LLNL 

Yield Surface Parameters 

A B C n m

159.2 ksi 158.4 ksi 0.014 0.93 0.11 

Failure Strain Parameters 

D1 D2 D3 D4 D5

-0.090 0.270 0.480 0.014 3.870

The failure strain parameters were validated by LLNL using DYNA-3D on penetration test data, 

as shown in figure 5-1 (reproduced from reference 4). The report [4] states that the test targets 

were rolled plate Ti-6Al-4V, per specification Aerospace Material Specification (AMS) 4911, 

0.601 inch (15.3 mm) thick. The targets were in a free-boundary condition, hanging from holes 

in the corner of each 36-inch- (914-mm)-square flat plate. The projectiles weighed 

approximately 8 lbs (3.6 kg) and were beveled at the nose to simulate a fan blade root impact 

footprint. The finite element model solution convergence issues were simplified in this study by 

maintaining close to uniform mesh resolution for the Ti-6Al-4V simulations. The through-thethickness mesh resolution of this three-dimensional, 1/4 symmetry model was 0.05 inch 

(1.3 mm) per element. An element aspect ratio less than 3:1 was maintained throughout this 

portion of the study. Eight-node solid brick elements with a one point integration were 

employed throughout this study. The outer regions of the targets were sometimes meshed with 

fewer elements through the thickness (by a factor of three) and then tied to the finer-zoned 

impact region to reduce the number of elements in each calculation. The finer-zoned impact 

region extended to between two to three times the relevant impactor dimension. 

FIGURE 5-1. THE LLNL ANALYSIS USING THE JOHNSON-COOK MATERIAL MODEL 

5-2
The available test data consisted of the initial conditions plus photographs and observations of 

the posttest target condition. The simulation predicted the correct amount of penetration and 

approximate crack patterns. 

5.2.2 Impact Analysis Using the Honeywell Material Model.

Before performing any comparison work with an alternative material model, Honeywell reran 

the same analysis using computer platforms and LS-DYNA versions consistent with other work 

reported in this document. The LLNL DYNA-3D finite element model was converted to an LSDYNA model by LLNL and provided to Honeywell. The material constants listed in table 5-1 

were used to activate the LS-DYNA-embedded material model, *MAT_JOHNSON_COOK 

(material type 15). After a baseline was established, the material model was replaced with the 

elastoplastic material model widely used in impact applications at Honeywell. This later model 

does not have the capability to represent material behavior under high strain rates, but it is used 

in a variety of applications because of its simplicity (no material constants). Figure 5-2 shows 

the comparison between the results produced by the two material models. Except for deflections 

at the outside boundaries of the plate, the baseline analysis using the Johnson-Cook model 

produced very similar results to figure 5-1. 

FIGURE 5-2. COMPARISON OF PREDICTIONS USING THE JOHNSON-COOK AND 

ELASTOPLASTIC MATERIAL MODELS 

On the other hand, for the example investigated, the conventional Honeywell material model 

could not adequately represent the test results. The simulation could not predict the petalling 

5-3
type of failure of the target, nor the crack patterns from the corners. Rather, the analysis 

predicted a shear (plug) type of failure for the plate. 

5.3 CONCLUSIONS.

The conclusions drawn from the Johnson-Cook material model comparison results are 

summarized as follows: 

• The Johnson-Cook material model provided a more realistic simulation of the test results 

than the alternative model. 

• The predicted failure modes were different for the two material models investigated. The 

Johnson-Cook model predicted a petalling type of failure, whereas the alternative model 

indicated a shear failure. 

• The Johnson-Cook model successfully predicted the complete energy absorption of the 

test, whereas the elastoplastic model conservatively predicted only 85 percent. 

• The Johnson-Cook model requires an extensive evaluation of the set of material constants 

for every material involved in a given practical problem. The alternative method is noted 

to be simple and inexpensive. 

• A very high mesh density was absolutely required to accurately simulate the test results 

with the Johnson-Cook model in the simple example studied: 1/4 model; 4 × 110,000 

elements. In a typical engine containment model, it is not practical to use this type of

mesh density, i.e., the task 4 fan blade-out containment problem featured approximately 

30,000 elements. 

5-4
6. ISSUES, LIMITATIONS, AND LESSONS LEARNED. 

6.1 BACKGROUND.

The LS-DYNA explicit finite element program is considered to be an excellent design tool to 

address impact and penetration modeling problems. The popularity of LS-DYNA is 

continuously increasing, especially in dealing with complex aerospace applications such as rotor 

fragment containment. For example, at Honeywell, LS-DYNA has permitted the successful 

design and optimization of a variety of gas turbine engine containment systems. Using LSDYNA has been instrumental in considerably reducing the number of expensive tests required to 

validate such containment designs. On the other hand, adaptation of LS-DYNA to impactrelated problems is not straightforward and requires careful understanding of the effects of the 

parameters involved. Users should understand that, as in any other complex analysis tools, a 

certain variation in results exists in LS-DYNA analyses. It is the user’s responsibility to 

understand the effects of the control parameters and to use them to adequately represent the 

physical behavior studied. 

In the following sections, variations in the results encountered during the course of the project, 

due to some computer hardware or software environments and due to contact choices dealing 

with part-to-part interaction, are summarized. The purpose of including this material is not to 

provide an absolute answer as to how to set these parameters but to promote better user 

awareness about possible variations when using LS-DYNA. 

6.2 EFFECTS OF COMPUTER PLATFORM AND SOFTWARE VERSION/REVISION.

In the course of the ballistic test simulations of composite fabric systems (see section 2), it was 

observed that conducting the same analyses at SRI and Honeywell gave different results, in 

terms of how much of the fragment kinetic energy was absorbed by the barrier. LSTC was 

contacted to isolate the reason for these differences, including the fact that analyses at 

Honeywell and SRI were performed on different platforms, using different versions or revisions 

of LS-DYNA. To avoid the possible effects of the newly created material model for fabrics, it 

was decided to create a more conventional impact example to investigate platform and revision 

issues. 

For this investigation, a simpler model was analyzed using standard material models in LSDYNA rather than the material model being developed by SRI for fabrics. This model consisted 

of a 0.160-inch- (4.1-mm)-thick steel plate impacted by a steel projectile. The kinetic energy 

absorbed by the barrier is calculated as the difference between the initial and residual kinetic 

energy of the projectile. A summary of the results of the calculations on different platforms and 

with different slideline types and parameters are listed in table 6-1. Because this case uses steel 

properties for the barrier, there are no experimental results to compare the analyses against. 

6-1
TABLE 6-1. LS-DYNA PLATFORM, VERSION/REVISION INVESTIGATION SUMMARY 

Percent Kinetic Energy Absorbed 

LS-DYNA Contact Type 

Auto Surface to Surface Single Surface 

Platform Version/Revision Soft=0 Soft=1 Soft=2 Auto Erode

HP ls960_s_447_hp8000_102 27.3 28.5 39.9 25.1 26.7

IBM ls960_s_447_ibmpwr3_43_p 27.0 28.5 39.9 26.1 26.7

IBM ls960_d_447_ibmpwr3_43_p 27.0 30.5 39.8 25.9 26.8

HP ls960_s_1488_hp8000_102 27.3 27.8 39.9 25.7 27.1

IBM ls960_s_1488_ibmpwr3q32_43_p 27.0 28.1 39.9 25.7 27.0

IBM ls960_d_1488_ibmpw3_43_p 27.2 30.2 39.9 25.8 27.0

Linux ls960_s_1488_linux_71_p 25.2 30.2 --- 24.1 ---

Linux ls960MPP_s_3041_linux_lam652pg 24.0 29.4 46.1 25.0 23.9

Example: ls960_d_447_ibmpwr3_43_p 

Ls960: version 

d: double precision (s: single precision) 

447: revision 

ibmpwr3: computer platform

43: operating system version 

p: parallel processing 

Honeywell used Hewlett-Packard (HP) and International Business Machines (IBM) Unix 

workstations, whereas SRI used PC-based Linux clusters. The Linux-based system was capable 

of multiparallel processing. The findings are summarized as follows: 

• The LS-DYNA results are consistent across computer platforms, given the same input 

and the same code version/revision. 

• Different versions of LS-DYNA will give different results with the same input, although 

the differences are not very large. Between Unix machines, differences were a maximum

of 5 percent, regardless of the revision, precision, or the operating system used. The 

largest difference observed was between the Unix and Linux machines, up to 16 percent. 

• Based on further investigations, it was found that the differences in results depended 

upon the complexity of analyzed problem and how intense the nonlinear contact/failure 

mechanisms were. For example, a subsequent analysis using one of the ballistic fabric 

analyses contained in section 2 showed that the results could be as much as 20 percent 

different between IBM and HP machines. 

6-2
• Different contact formulations will give significantly different results for the same

problem (using the same version and platform). Further investigation was performed and 

is reported in section 6.3. 

6.3 EFFECTS OF CONTACT PARAMETERS.

Some of the contact parameters of LS-DYNA were varied on the same example to find out the 

variation in the results. The computer platform and the program version were kept the same. 

Figure 6-1 summarizes the findings. Automatic-single-surface, eroding-single-surface, surfaceto-surface, and automatic-surface-to-surface are standard contact options within LS-DYNA. 

SOFT=0, 1, or 2 are available options to treat contacting entities. SFS and TSSFAC are the 

contact penalty factor and the time-step scale factor (see section 4.4), respectively. In addition, 

El=2 and 16 are two types of shell element formulation. The results show that energy absorbed 

can be considerably different (by approximately a factor of 2.5) due to various combinations of 

listed parameters. 

Steel target 0.160" thick

Steel Projectile - HP8000_102

0

10

20

30

40

50

60

6789 10

En

erg

y A

bsorbed (

%)

auto_surface_to_surface auto_single_

surface

erod_single_

surface

surface_to_

surface

SFS=1.0

TSSFAC=0.9

SFS=0.1

TSSFAC=0.9

El=2 El=16

SFS=1.0

TSSFAC=0.2

SFS=0.1

TSSFAC=0.2

SOF4T=0 SOF5 T=1 SOFT=2

FIGURE 6-1. EFFECTS OF LS-DYNA CONTACT PARAMETERS (STEEL TARGET) 

A limited parametric study was also performed on the ballistic test simulation of an eight-layer 

Zylon model (1x8) (see section 2.3), which also includes the user-defined fabric material model. 

As mentioned in section 2.4, the software version and the platform were kept the same

throughout the current research program for consistency. The percent energy absorption for the 

baseline analysis was 19.4 percent, as shown in table 2-3. Figure 6-2 shows the effects on the 

6-3
results of the studied contact parameters and the element type; the middle column being the 

baseline analysis for which the results were acceptable when compared to the test results. To 

establish the variation on the result due to the computer platform only, the baseline analysis was 

also repeated on a different platform (IBM Unix workstation). The result was observed to be 20 

percent less than the baseline using an HP Unix workstation. No other parametric combinations 

were studied. 

Fabric Target 0.016" thick, user material (ZYLON 1x8)

Steel Projectile - HP8000_102

0

10

20

30

40

50

60

2 3

E

nerg

y Absorbed (

%)

SFS=0.1

TSSFAC=0.2

auto_surface_to_surface

El=2 El=16

20% lower

on IBM

19.4 %

on HP

1

SOFT=1 SOFT=2

FIGURE 6-2. EFFECTS OF LS-DYNA CONTACT PARAMETERS AND PLATFORM 

(FABRIC TARGET) 

6-4
7. CONCLUDING REMARKS.

This report contains numerical modeling of the engine containment ring ballistic tests conducted 

by NASA Glenn Research Center. LS-DYNA code was used for modeling. The material model 

used in this study was developed by SRI International. Modifications were made to the material 

model until a reasonable correlation was obtained between simulations and the test data. 

Subsequently, the resulting material model and modeling techniques were used to model and 

simulate a recent fan blade-out containment test of a full-scale Honeywell turbofan engine. 

The following items summarize the overall conclusions of the work performed by Honeywell in 

this study: 

• The new user-defined material model was successfully compiled within the LS-DYNA 

code. The same model is able to represent both Kevlar and Zylon material behavior, 

with separately provided, material-specific constants. The model formulation was based 

on actual material data and provides a more realistic representation of the fabric behavior. 

The new material model is independent of the number of fabric layers and, therefore, 

provides the flexibility to model single or multiple fabric layers. 

• For the range of analytical parameters considered in this work, promising correlation was 

obtained between the simulation and the ballistic test results for both Kevlar and Zylon, 

using a single shell-element layer simulating all the fabric layers. Both energy absorption 

and overall deflection behavior of the fabric systems were successfully simulated. The 

relative simulations are able to depict the ballistic strength differences between Zylon and 

Kevlar. Similar successful analysis-to-test correlations were obtained when up to four 

layers of shell elements were used to model all fabric layers. Although good trends were 

observed up to four shell-element layers, the prediction capability was not satisfactory for 

modeling techniques using more than four layers. More work is needed to explore the 

limitations of modeling techniques involving a high number of shell elements. 

• A full-scale engine fan blade-out event was successfully simulated using the fabric 

material models and developed analytical methodologies. Good correlation was obtained 

between the simulation and the engine containment test results, using the new Kevlar 

material model and the single shell layer modeling technique. The prediction capability 

was significantly improved with the new material model and the associated modeling 

techniques, with respect to the previous methodology used at Honeywell. 

• In spite of successful results during the ballistic test simulations, further analytical 

enhancement with multilayer modeling was not possible due to numerical instabilities. 

• Comparison of Kevlar and Zylon capabilities within the same containment design 

revealed containment results consistent with the ballistic test trends. For the same

number of fabric layers, Zylon offers a weight reduction possibility if it is used in lieu of

Kevlar. 

• The mesh density was kept constant during this program, but the possible effects on the 

results was not investigated. Further investigation on mesh sensitivity, contact 

parameters, and multilayer numerical instabilities are recommended. 

7-1
• The results showed that the choice of analysis parameters and solution algorithms, such 

as contact treatment, had a big effect on the resolution of the predictions. A brief 

discussion of the variations in the results that can be experienced using LS-DYNA, 

depending on the contact types, processor types, and computer platforms, was provided 

in section 6.

• Based on the experience gained during the execution of the impact and containment 

simulations, a generic containment finite element model, including fabric wraps, was 

created. The purpose of this model is to provide LS-DYNA users with generic guidelines 

for modeling composite fabric wraps in impact containment-related applications.

It is recommended that the following topics be examined in future work. 

• Material model for alternative composite fabrics—Although ballistic testing on heavy 

Zylon was also performed by NASA, a model was not produced due to a lack of static 

material property data. The material model for this fabric can be derived with reasonably 

short effort and will help increase the validation database. Due to its high strength, this 

material offers a high potential for weight reduction in engine fragment containment 

applications. 

• More representative fan blade release experiments—Ballistic experiments should be 

performed in which more representative tangential trajectory of the fan blade fragment is 

studied. This will facilitate the interpretation of the ballistic test results for potential use 

in containment design systems. 

• Multiple shell-element layers to model multiple fabric plies—Efforts to investigate fabric 

impact simulations using multiple layers of shells to model thick fabric layers should be 

continued. This would provide the capability to indicate the number of layers penetrated 

versus the number of layers remaining during a containment event and, therefore, better 

evaluate the containment margin. 

• Sensitivity to modeling parameters—The effects of the mesh sensitivity, various contact 

parameters, and other computational parameters should be further investigated. 

• Simulation of more fan blade containment applications—The derived fabric material 

model should be used to simulate other engine fan blade containment systems. This 

would increase the confidence in adequately simulating different designs with the same

methodology. 

• LS-DYNA benchmarking for containment problems—Similar to crashworthiness 

industry applications, Livermore Software Technology Company should establish 

aerospace benchmark examples to ensure that LS-DYNA code predictions are consistent 

across platforms and future software versions. 

7-2
8. REFERENCES.

1. Periera, M. and Revilock, D., “Explicit Finite Element Modeling of Multilayer 

Composite Fabric for Gas Turbine Engine Containment Systems, Part 2: Ballistic Impact 

Testing,” FAA report DOT/FAA/AR-04/40,P2, 2004. 

2. Simons, J., Erlich, D., and Shockey, D., “Explicit Finite Element Modeling of Multilayer 

Composite Fabric for Gas Turbine Engine Containment Systems, Part 3: Model 

Development and Simulation of Experiments,” FAA report DOT/FAA/AR-04/40,P3, 

2004. 

3. Lesuer, D., “Experimental Investigation of Material Models for Ti-6Al-4V and 2024-

T3,” FAA report DOT/FAA/AR-00/25, September 2000. 

4. Kay, G., “Failure Modeling of Titanium 6Al-4V and 2024-T3 Aluminum With the 

Johnson-Cook Material Model,” FAA report DOT/FAA/AR-03/57, September 2003. 

8-1/8-2
APPENDIX A—LS-DYNA USER INPUT FOR KEVLAR AND ZYLON MATERIAL

MODEL

*KEYWORD 

$ ------------------------------ 

$ 

$ DEFINITION OF MATERIAL 192 Zylon 

$ =================================================== 

$ === Zylon AS 35x35, 500 Denier 

$ User-defined material model from FAA AACE Grant Project 

$ fabric density = 1.54 g/cm^3 or 0.0556 lb/in^3 

$ “model equivalent” density (x2)= 3.08 g/cm^3 or 0.1112 

lb/in^3 

$ LS-DYNA units: 0.1112 / 386.4 = 2.877E-04 

$ --------------------------------------------------- 

$ 

*MAT_USER_DEFINED_MATERIAL_MODELS 

$ mid ro mt lmc nhv iortho 

ibulk ig 

 192 2.877e-4 47 48 15 1 

1 1 

$ card 2: ivect ifail 

$ ivect ifail 

 0 1 

$ card 3: aopt 

$ aopt 

 3.0 

$ card 4: 

 0 0 1 

$ emod epmin epmax sigmax crimpx crimpy 

epsoft ecrimp 

 13.34 0.0250 .036 0.4205 0.037 0.006 

0.01 0.047 

$ comfac g2 epc epu epfail ddmax 

tc 

 .005 0.0 0.005 0.005 0.00 0.1 

2.e-3 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

A-1
$ 

$ DEFINITION OF MATERIAL 292 Kevlar 

$ =================================================== 

$ === Kevlar 29 AS 17x17, 1500 Denier 

$ User-defined material model from FAA AACE Grant Project 

$ fabric density = 1.44 g/cm^3 or 0.052 lb/in^3 

$ “model equivalent” density (x2)= 2.88 g/cm^3 or 0.104 

lb/in^3 

$ LS-DYNA units: 0.104 / 386.4 = 2.6915E-04 

$ --------------------------------------------------- 

$ 

*MAT_USER_DEFINED_MATERIAL_MODELS 

$ card 1: mid ro mt lmc nhv iortho ibulk ig 

$ mid ro mt lmc nhv iortho 

ibulk ig 

 292 2.69e-4 47 48 15 1 

1 1 

$ card 2: ivect ifail 

$ card 2: ivect ifail 

 0 1 

$ card 3: aopt 

 3.0 

$ card 4: 

 0 0 1 

$ card 5 - 10 

$ emod epmin epmax sigmax crimpx crimpy 

epsoft ecrimp 

 10.15 0.0235 0.0262 0.3045 0.010 0.010 

0.01 0.091 

$ comfac g2 epc epu epfail ddmax 

tc 

 .005 0.0 0.005 0.005 0.00 0.1 

8.e-3 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

 0.0 0.0 0.0 0.0 0.0 0.0 

0.0 0.0 

$ 

A-2
APPENDIX B—BALLISTIC TEST DATA AND LS-DYNA SIMULATION RESULTS FOR

KEVLAR AND ZYLON MATERIALS

B-1
TABLE B-1. LS-DYNA ANALYSIS RESULTS AND BALLISTIC TEST RESULTS FOR KEVLAR 

LS-DYNA Analysis Ballistic Tests 

Analysis Scaled 

to Tested Energy

Model 

ID 

Fabric 

Layers 

(n) 

Shell 

Layers 

(k) 

Analysis 

Impact 

Velocity

(ft/sec) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Test 

ID 

Test 

Impact 

Velocity

(ft/sec) 

Projectile 

Mass 

(g) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Average

Absorbed 

Energy

(in-lb) 

model231_1 1 1 388 19977 16133 3844 19.24 LG433

LG434 

389 384 

316.7315.9 

19703 19151 

1753716926 

21662225 

10.9911.62 

1970319151 

1591215466 

37913685 3738 

model232_2 2 1 345 16040 6966 9074 56.57 LG444

LG449 

349 345 

316.4316.2 

15844 15473 

1005310119 

57915354 

36.5534.60 

1584415473 

68816720 

89638753 8858 

model222_4 4 1 904 110150 99656 10494 9.53 LG403

LG410 

900 912 

318.4316.4 

106033 108195 

9346997331 

1256410864 

11.8510.04 

106033108195 

9593197887 

1010210308 10205 

model228_8 8 1 875 103030 83846 19184 18.62 LG404

LG409LG424 

897 888 834 

317.8316.0320.9 

105128 102331 

91766 

876408481973029 

174881751218737 

16.6417.1120.42 

105128102331

91766 

855548327774680 

195751905417087 

18572 

model230_16 16 1 896 108270 61487 46783 43.21 LG429

LG432 

914 896 

316.2320.0 

108601 105620 

6739255585 

4120950035 

37.9547.37 

108601105620 

6167559982 

4692645638 46282 

model229_24 24 1 904 110150 29186 80964 73.50 LG405

LG411LG427 

898 886 915 

319.0314.8317.9 

105761 101598 109424 

322652207648315 

734967952261110 

69.4978.2755.85 

105761101598109424 

280232692028994 

777387467880431 

77615 

B-2
TABLE B-2. LS-DYNA ANALYSIS RESULTS AND BALLISTIC TEST RESULTS FOR ZYLON 

LS-DYNA Analysis Ballistic Tests 

Analysis Scaled 

to Tested Energy

Model 

ID 

Fabric 

Layers 

(n) 

Shell 

Layers 

(k) 

Analysis 

Impact 

Velocity

(ft/sec) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Test 

ID 

Test 

Impact 

Velocity

(ft/sec) 

Projectile 

Mass 

(g) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Average

Absorbed 

Energy

(in-lb) 

model122_4 4 1 891 107020 98175 8845 8.26 LG406

LG412 

895 798 

319.5318.4 

105220 

83361 

91585.270333.5 

1363513027 

12.9615.63 

105220

83360 

9652476471 

86966890 7793 

model122_2 4 2 891 107020 96378 10642 9.94 LG406

LG412 

895 798 

319.5318.4 

105220 

83361 

91585.270333.5 

1363513027 

12.9615.63 

105220

83360 

9475775071 

10463

8289 9376 

model122 4 4 891 107020 97055 9965 9.31 LG406

LG412 

895 798 

319.5318.4 

105220 

83361 

91585.270333.5 

1363513027 

12.9615.63 

105220

83360 

9542375599 

97977762 8780 

model128_8 8 1 904 110150 88753 21397 19.43 LG408

LG413LG417LG425 

904 901 892 908 

318.0319.9314.6316.6 

106843 106769 102913 107316 

82008.579198.980926.984140.4 

24834275702198623176 

23.2425.8221.3621.60 

106843106769102913107316 

86088860298292286469 

20755207401999120846 

20583 

model128_4 8 2 904 110150 91430 18720 17.00 LG408

LG413LG417LG425 

904 901 892 908 

318.0319.9314.6316.6 

106843 106769 102913 107316 

82008.579198.980926.984140.4 

24834275702198623176 

23.2425.8221.3621.60 

106843106769102913107316 

88685886248542389078 

18158181451749018238 

18008 

model128_2 8 4 904 110150 90339 19811 17.99 LG408

LG413LG417LG425 

904 901 892 908 

318.0319.9314.6316.6 

106843 106769 102913 107316 

82008.579198.980926.984140.4 

24834275702198623176 

23.2425.8221.3621.60 

106843106769102913107316 

87627875668440488015 

19216192031850919301 

19057 

model128 8 8 904 110150 91643 18507 16.80 LG408

LG413LG417LG425 

904 901 892 908 

318.0319.9314.6316.6 

106843 106769 102913 107316 

82008.579198.980926.984140.4 

24834275702198623176 

23.2425.8221.3621.60 

106843106769102913107316 

88891888308562289285 

17951179391729118031 

17803 

B-3
TABLE B-2. LS-DYNA ANALYSIS RESULTS AND BALLISTIC TEST RESULTS FOR ZYLON (Continued) 

LS-DYNA Analysis Ballistic Tests 

Analysis Scaled 

to Tested Energy

Model 

ID 

Fabric 

Layers 

(n) 

Shell 

Layers 

(k) 

Analysis 

Impact 

Velocity

(ft/sec) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Test 

ID 

Test 

Impact 

Velocity

(ft/sec) 

Projectile 

Mass 

(g) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Absorbed 

Energy

(%) 

Impact 

Energy

(in-lb) 

Exit 

Energy

(in-lb) 

Absorbed 

Energy

(in-lb) 

Average

Absorbed 

Energy

(in-lb) 

model130_16 16 1 904 110150 37645 72505 65.82 LG426 911 316.8 108094 51694.9 56400 52.18 108094 36942 71152 71152 model130_8 16 2 911 111840 58109 53731 48.04 LG426 911 316.8 108094 51694.9 56400 52.18 108094 56163 51932 51932 model130_4 16 4 911 111840 62208 49632 44.38 LG426 911 316.8 108094 51694.9 56400 52.18 108094 60125 47970 47970 model130_2 16 8 911 111840 70876 40964 36.63 LG426 911 316.8 108094 51694.9 56400 52.18 108094 68502 39592 39592 model130 16 16 830 106730 71246 35484 33.25 LG426 911 316.8 108094 51694.9 56400 52.18 108094 72157 35938 35938 model129_24 24 1 904 110150 1510 108640 98.60 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

14561227 

104749

88245 96497 

model129_12 24 2 904 110150 1266 108884 98.90 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

12211028 

104984

88444 96714 

model129_6 24 4 904 110150 1155 108995 99.00 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

1114

938 

105091

88534 96812 

model129_3 24 8 904 110150 34700 75450 68.50 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

3345728186 

7274761286 67017 

model129_2 24 12 904 110150 49365 60785 55.18 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

4759740098 

5860849374 53991 

model129 24 24 904 92840 50000 42840 46.14 LG407

LG414 

904 830 

316.1315.9 

106204 

89472 

0 0 

106204

89472 

100.00100.00 

106204

89472 

5719848186 

4900741286 45146 

B-4
APPENDIX C—COMPARISON OF BALLISTIC TEST RESULTS AND LS-DYNA

SIMULATION RESULTS FOR ZYLON MATERIAL

(a)

(b) 

FIGURE C-1. ANALYSIS VS TEST FOR FOUR-LAYER ZYLON 

C-1
(c) 

(d) 

FIGURE C-1. ANALYSIS VS TEST FOR FOUR-LAYER ZYLON (Continued) 

C-2
(e) 

(f) 

FIGURE C-1. ANALYSIS VS TEST FOR FOUR-LAYER ZYLON (Continued) 

C-3
(a) 

(b) 

FIGURE C-2. ANALYSIS VS TEST FOR 24-LAYER ZYLON 

C-4
(c) 

(d) 

FIGURE C-2. ANALYSIS VS TEST FOR 24-LAYER ZYLON (Continued) 

C-5
(e) 

(f) 

FIGURE C-2. ANALYSIS VS TEST FOR 24-LAYER ZYLON (Continued) 

C-6