High-speed Photogrammetric Analysis on the Ballistic Behavior of Kevlar Fabrics Impacted by Various Projectiles

Transcription

1 High-speed Photogrammetric Analysis on the Ballistic Behavior of Kevlar Fabrics Impacted by Various Projectiles by Jian H. Yu, Peter G. Dehmer, and Chian-Fong Yen ARL-TR-5333 September 2010 Approved for public release; distribution unlimited.

2 NOTICES Disclaimers The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. Citation of manufacturer s or trade names does not constitute an official endorsement or approval of the use thereof. Destroy this report when it is no longer needed. Do not return it to the originator.

3 Army Research Laboratory Aberdeen Proving Ground, MD ARL-TR-5333 September 2010 High-speed Photogrammetric Analysis on the Ballistic Behavior of Kevlar Fabrics Impacted by Various Projectiles Jian H. Yu, Peter G. Dehmer, and Chian-Fong Yen Weapons and Materials Research Directorate, ARL Approved for public release; distribution unlimited.

4 REPORT DOCUMENTATION PAGE Form Approved OMB No Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports ( ), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) September REPORT TYPE 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE High-speed Photogrammetric Analysis on the Ballistic Behavior of Kevlar Fabrics Impacted by Various Projectiles 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jian H. Yu, Peter G. Dehmer, and Chian-Fong Yen 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) U.S. Army Research Laboratory ATTN: RDRL-WMM-B Aberdeen Proving Ground, MD PERFORMING ORGANIZATION REPORT NUMBER ARL-TR SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR S ACRONYM(S) 11. SPONSOR/MONITOR'S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT There is a need to understand the penetration mechanics on Kevlar fabrics, as they are widely used in protective armors. Photogrammetry is an imaging technique that determines geometric properties, such as the displacement history, by tracking the minute changes in the pixel pattern on the digital image of interest. By combining high-speed photography with photogrammetric technique, a full-field view on the 3-D displacement by the fabric during ballistic impact is made possible. The displacement data is essential for evaluating the ballistic performance of the fabrics. More importantly, the experimental data not only provides valuable insight into effects of yarn properties, boundary conditions, crimps, and frictions on the mechanics of the fabrics, but also serves as a validation tool for the modeling of fabrics. Results from high-speed photogrammetric analysis of Kevlar fabrics that undergo ballistic impact are presented in this report. 15. SUBJECT TERMS ballistic impact, Kevlar fabric, KM2 fiber yarn, photogrammetry deformation, high-speed photography 16. SECURITY CLASSIFICATION OF: a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 32 19a. NAME OF RESPONSIBLE PERSON Jian H. Yu 19b. TELEPHONE NUMBER (Include area code) (401) Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 ii

5 Contents List of Figures List of Tables iv v 1. Introduction 1 2. Material and Technique Fabric Preparation Impact Experiment Setup Result and Discussion Photogrammetric Analysis Boundary Confinement Residual Energy Conclusion References 14 Appendix A Displacement Tables 17 Appendix B. Residual Energy Tables 21 Distribution List 23 iii

6 List of Figures Figure 1. A Type 706 Kevlar fabric is painted with a permanent black ink....2 Figure 2. Three types of projectiles; from left to right: 5.56 mm sphere, 0.22 CAL. RCC, 0.22 CAL. FSP....3 Figure 3. Impact experiment setup and camera placement; the weft yarns are oriented along the x-axis....3 Figure 4. Displacement history in the out-of-plane, z-direction; the projectile was a 5.56 mm sphere that had an impact speed of 63 m/s; 5.08 cm diameter boundary. The contour scale is from 0 to 7 mm....5 Figure 5. x- and y-displacements at 14.8 µs after impact; the projectile was a 5.56 mm sphere that had an impact speed of 63 m/s; 5.08 cm diameter boundary....6 Figure 6. z-displacements history of a fabric impacted by a 5.56 mm sphere at a speed of 157 m/s; 5.08 cm diameter boundary....6 Figure 7. z-displacement histories at the impact point by 5.56 mm sphere impact at various speeds; 5.08 cm diameter boundary....7 Figure 8. z-displacement histories at the impact point by 0.22 Caliber RCC impact at various speeds; 5.08 cm diameter boundary....8 Figure 9. z-displacement histories at the impact point by 0.22 Caliber FSP impact at various speeds; 5.08 cm diameter boundary....8 Figure 10. Net displacement histories of the principal weft yarn at the boundary....9 Figure 11. Displacements from three tests and their average displacement of fabrics that were impacted by the 5.56 mm sphere at 63 m/s Figure 12. Dissipated energy as function of impact energy. The shade zone is for illustration purpose only, which does not delineate the exact boundary of the V 50 zone Figure 13. Normalized energy dissipated per broken yarn as function of impact energy at impact speed well above V 50. The error bars indicated the error due to not accounting for the partial broken yarns Figure 14. Photographs of the damage fabrics by the three projectiles at impact speed above V iv

7 List of Tables Table A mm sphere, 5.08 cm dia. clamp Table A Caliber RCC, 5.08 cm dia. clamp Table A Caliber FSP, 5.08 cm dia. clamp Table B mm sphere, 5.08 cm dia. clamp Table B Caliber RCC, 5.08 cm dia. clamp Table B Caliber FSP, 5.08 cm dia. clamp Table B mm sphere, cm dia. clamp v

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9 1. Introduction Due to its superior mechanical properties and low density, Kevlar fabric is an important textile used in ballistic protection applications. Currently, the design of soft armor is mostly based on empirical studies, such as V 50 results and impact on a clay backing experiments (1 3). However, these two ballistic testing methods provide only a benchmark on the ballistic performance i.e., pass or fail criterion. The tests do not provide any information on how the fabric is interacting with the projectile, nor do they provide a deformation history on the fabric. Computational modeling is another method used to study the ballistic behaviors of Kevlar textile (4 10). Modeling provides both visual and numerical data of the fabric during a ballistic event. However, the models need to be validated before they can be implemented as a design tool for soft armors. One way to validate the model is to compare its results to experimental data. Aside from V 50 data and residual speed measurements, there is almost no quantitative data on the deformation of the fabric during a ballistic impact event. Photogrammetric analysis has been used to measure the deformability of fabrics and textile composites (1, 12). Lomov et al. studied the in-plane deformation of yarns in a fabric that underwent shearing using 2-D photogrammetry (12). Weerasooriya et al. obtained the out-ofplane deformation of a Kevlar fabric impacted by a blunt object at low speed using 3-D photogrammetry (13) Chocron et al. wove a nickel-chromium wire into a fabric that can indirectly measure the strain on the yarn (14). This report presents a 3-D photogrammetric analysis on the displacement of a Kevlar fabric that is impacted by different projectiles. 2. Material and Technique 2.1 Fabric Preparation We used a 7 7 in 2 plain-woven Kevlar fabric (Hexcel Co, Type 706, 34 warp yarns per inch and 34 weft yarns per inch, KM2 fibers) in the ballistic impact test. A single-ply fabric was clamped to a steel frame that has a circular aperture with a diameter of 5.08 cm (2 in). The contacting surfaces of the steel frame were covered with a coarse anti-slip tape. The fabric was patterned with burnt holes for aligning with the frame. Then, the frame and the fabric were bolted down with a total pressure of 3 GPa. The targeted area on the fabric was painted with a random pattern of black dots for displacement tracking. Figure 1 shows a fabric piece after painting with a permanent black ink (Sharpie ink). The proper size of the black dots is critical for photogrammetric analysis. The dot size is about five pixels in diameter, as it rendered digitally in a TIFF formatted image file. The dot coverage over 1

10 the field-of-view should be more than 50% of viewing area. The paint can be any color; however, it must exhibit a high contrast on the target s surface. 2.2 Impact Experiment Setup Figure 1. A Type 706 Kevlar fabric is painted with a permanent black ink. Ballistic impacts were carried out with a 0.22 CAL gas gun. The gas gun was pressurized at different pressures with helium gas to propel the projectile at selected impact speeds. Figure 2 shows the three types of projectiles that were used in the experiment: (1) 0.22 CAL fragment-simulating projectile (FSP, 0.22 CAL, 1.1 g, MIL-P-46593A); (2) stainless steel right circular cylinder (RCC, diameter = 5.51 mm, length = 5.50 mm, mass = g, SS type 440C); and (3) stainless steel sphere (diameter = 5.56 mm, mass = g, SS type 440C). The speed of the projectile was tracked with a Doppler radar (BR-3502, Infinition Inc.). Two digital high-speed cameras (SA1, Photron USA, Inc.) were used to generate stereo images of the impact event. The cameras were placed behind the target fixture, in the z-direction (figure 3). The angle between the cameras was set to 18. The images were recorded at pixels resolution; the frame rate was set at frames-per-second; the exposure on each frame was 1/67500 s; and the images were saved as 8-bit TIFF files. 2

11 Figure 2. Three types of projectiles; from left to right: 5.56 mm sphere, 0.22 CAL. RCC, 0.22 CAL. FSP. Figure 3. Impact experiment setup and camera placement; the weft yarns are oriented along the x-axis. To record the full-view of the deforming fabric, a macro-lens (Nikon AF-Nikkor) was mounted on each camera. The focal length and the f-stop were set at 35 mm and f/8, respectively. The distance between the target and the cameras was 0.6 m. The field of view was about 5 cm 2, and it was centered on the location of the impact point. The stereo images were analyzed using a commercially available photogrammetric software program called ARAMIS (GOM GmbH, Germany, distributed by Trilion Quality Systems in the United States). The following ARAMIS settings were used to analyze the images: the facet size was set to 11 11; the facet step was set to 5 5; an average noise filter routine was applied to the results; the filter was set for 1 run; and the filter size was set to 3. 3

12 3. Result and Discussion 3.1 Photogrammetric Analysis Although the high-speed cameras were too slow to capture the longitudinal elastic wave at frames-per-second, they were fast enough to record the slower transverse deflection wave. Figure 4 shows the transverse wave in a fabric that was impacted by a steel sphere traveling at 63 m/s. The transverse wave traveled down the principal weft and warp yarns faster than it can travel radially away from the impact point in other directions. The deflection of the principal yarns drove the secondary yarns into motion at the crossovers. However, the yarns interlocked each other at the crossovers, resisting the movement of the principal yarns. As a result of this interaction, the fabric deformed out of the xy-plane into a shape that resembled a square pyramid, which is a well-documented phenomenon in the literature (1 10). However, the photogrammetric analysis revealed previously unobserved details in the deformation. The principal yarns were displaced immediately after impact, in advance of the square pyramid deformation, which indicated that the principal yarns were under loading before the bulk out-ofplane deformation. The pyramid corners are actually stretched out in the directions of the principal yarns. The base of the pyramid resembles a cross more than a rhombus (see figure 4 for t >14.8 µs). Although the deflection is small, the principal yarns are already being pulled ahead of the square pyramid deformation. Figure 5 shows the displacements in the x- and y-directions, 14.8 µs after impact. The principal yarns were bowing toward the impact location. Although the displacement is small about 0.05 mm the principal yarns were being pulled at the boundary before the onset of the transverse wave. At µs after impact, the slow-moving transverse wave finally reached the clamp boundary and was reflected back toward the impact point. The maximum recorded out-of-plane displacement was not reached until 163 µs after impact. There was no penetration at an impact speed of 63 m/s. Figure 6 shows a fabric that is penetrated by the sphere at an impact speed of 157 m/s, which is above the V 50 (110 m/s) of the fabric under the imposed 5.08 cm diameter clamp boundary. The penetration is indicated by the disappearance of the color contours on the digitized image of the fabric. The cross forming phenomenon is not observed at high impact speeds where penetration occurs. The impact is so fast that the yarns have little time to react. At the impact speed of 157 m/s, the deformation rate on the fabric is much higher than the 63 m/s impact. The sphere penetrated the fabric before the transverse wave reached the boundary. The fabric did not deform to its maximum allowable z-displacement before penetration. The impact force loading was concentrated on the impact region at a fast rate; the fabric did not have enough time to 4

13 redistribute the load from its principal yarns to the secondary yarns. Thus, the principal yarns ruptured before the transverse wave could propagate through the secondary yarns. Figure 4. Displacement history in the out-of-plane, z-direction; the projectile was a 5.56 mm sphere that had an impact speed of 63 m/s; 5.08 cm diameter boundary. The contour scale is from 0 to 7 mm. 5

14 Figure 5. x- and y-displacements at 14.8 µs after impact; the projectile was a 5.56 mm sphere that had an impact speed of 63 m/s; 5.08 cm diameter boundary. Figure 6. z-displacements history of a fabric impacted by a 5.56 mm sphere at a speed of 157 m/s; 5.08 cm diameter boundary. Figure 7 plots the displacement histories in the z-direction for fabrics that are impacted by 5.56 mm spheres at various impact speeds. Similar displacement plots are also obtained for the 0.22 CAL right circular cylinder (RCC) projectiles and fragment simulating projectiles (FSP) (figures 8 and 9). The numerical values are presented in the appendix A. The measurement 6

15 error in the z-displacement is ± 0.02 mm. For penetrated fabrics, the last z-displacement value is recorded just before the yarns rupture around the impact point. The tabulated values are provided in appendix A. For the non-penetrating impact speeds, the upslope of the z-displacement-versus-time curve is not exactly symmetrical with the downslope part of curve i.e., the curve is not parabolic, which means the kinetic energy is not conserved. The collision between the projectile and the fabric is inelastic; a small amount of kinetic energy is lost through the frictional force between the yarns, the dissipated strain energy on yarns, and air drag on the fabric during the deflection. The maximum z-displacement value increases with increasing impact speed. The fabric would reach its maximum allowable displacement limit at an impact speed just below the penetration speed. Above V 50, the penetration speed, the maximum z-displacement value would decrease with increasing impact speed. The principal yarns reach their failure strain at the impact point before the yarns can distribute the stress to other parts of the yarns by uncrimping mm sphere impact z-displacement (mm) m/s 63 m/s 83 m/s 105 m/s 124 m/s 142 m/s 157 m/s 170 m/s time (µs) Figure 7. z-displacement histories at the impact point by 5.56 mm sphere impact at various speeds; 5.08 cm diameter boundary. 7

16 z-displacement (mm) Caliber RCC impact 39 m/s 60m/s 78 m/s 91 m/s 101 m/s 123 m/s 143 m/s 156 m/s 182 m/s time (µs) Figure 8. z-displacement histories at the impact point by 0.22 Caliber RCC impact at various speeds; 5.08 cm diameter boundary. z-displacement (mm) Caliber FSP impact 39 m/s 48m/s 81 m/s 98 m/s 122 m/s 140 m/s time (µs) Figure 9. z-displacement histories at the impact point by 0.22 Caliber FSP impact at various speeds; 5.08 cm diameter boundary. 8

17 3.2 Boundary Confinement The level of boundary confinement on the fabric can affect the ballistic results greatly. Yarn pull-out (yarn slippage) can take place on the boundary if the fabric edges are not fully confined. Slippage frequently occurs at impact speeds just below V 50. If there is yarn slippage at the boundary, the ballistic data of the experiment will not be consistent and reproducible. To examine the boundary condition at the clamping edge, the net displacement of the principal weft was tracked at the edge (figure 10). The fabric was impacted by a sphere at a speed of 116 m/s, which was the highest non-penetrated speed recorded. Most of the initial displacements were due to the z-displacement. The final displacement indicated that the yarn was pulled no more than 14 microns from the edge of the clamp. Figure 10. Net displacement histories of the principal weft yarn at the boundary. Figure 11 show the reproducibility of a set of ballistic tests below the penetration speeds. All three test results do not vary significantly from each other. The standard deviation from the average is no greater than 0.08 mm. In general, the ballistic results are reproducible at speeds below V 50. Around the V 50 range and beyond, the results are subject to statistical variation; the yarns break with a probabilistic distribution the number of yarns broken varied in each test, except for the sphere impact cases. However, at low impact speeds, yarns were not broken at all; the results are not subjected to the statistic failure of the yarns. 9

18 z-displacement (mm) test1 test2 test3 average time (µs) 3.3 Residual Energy Figure 11. Displacements from three tests and their average displacement of fabrics that were impacted by the 5.56 mm sphere at 63 m/s. To validate simulation models, not only is the displacement history required, but the collision energy is needed as well at least in both impact speed extremes, low and high. Figure 12 plots the dissipated energy of the projectile after the collision with fabric and the initial kinetic energy of the projectile (see appendix B for tabulated values). Below V 50, the energy dissipated has a linear relation with the impact energy, which means the amount of energy that is absorbed by the fabric is proportional to the impact energy. Regardless of the projectile type, the fabric is able to absorb at least 73% of the impact energy until the impact speed approaches V 50. We think the proportional relation is due to the number of yarns that were engaged in the deformation during the impact. At very low impact speed, the projectile engages and uncrimps only a few secondary yarns (yarns that are not in contact with the projectile) before the projectile is deflected back; the remaining secondary yarns are not stretched to their limit. As the impact speed increases, the projectile has enough energy to engage more yarns before being deflected. Most of the impact energy is transferred to the kinetic energy of the fabric, the yarn strain energy, and the yarn frictional energy. We also obtained a linear relation, which has a slope of 0.83, for a cm (4 in) diameter circular clamp (see table B-4). As the boundary opens up to infinity (unbounded), the slope should approach unity. All the impact energy would be absorbed by the fabric, mostly in the form of kinetic energy exchange for the non-penetration cases. 10

19 Near but still below V 50, additional energy is used to break the principal yarns; the ratio between the energy dissipated and the impact energy is about one. Even though yarns are broken at the impact area, there are not enough broken yarns to allow penetration. Figure 12. Dissipated energy as function of impact energy. The shade zone is for illustration purpose only, which does not delineate the exact boundary of the V 50 zone. At impact speeds well above V 50, the energy dissipated is proportional to the number of broken yarns. Figure 13 is a normalized energy dissipated per broken yarn as function of impact energy. Since it is difficult to account for partially broken yarns, only the number of completely broken yarns was used in the normalization. Figure 14 shows the damage area on the fabric for each of the three projectiles at speeds around 300 m/s. The number of yarns broken at high impact speed is consistent from test to test for each projectile. The sphere completely breaks five yarns; the RCC breaks 11 to 12 yarns; and the FSP breaks 10 to 11 yarns. Since the fabric deformation is highly localized at the impact point, and the projectile penetrates before the rest of the fabric is set into motion, almost all of the dissipated energy is spent on breaking the yarns. The normalized dissipate energy becomes constant at high impact speeds, independent of projectile types. 11

20 Figure 13. Normalized energy dissipated per broken yarn as function of impact energy at impact speed well above V 50. The error bars indicated the error due to not accounting for the partial broken yarns. Figure 14. Photographs of the damage fabrics by the three projectiles at impact speed above V Conclusion Photogrammetry is capable of recording the deformation history of fabrics during a ballistic impact event. The experimental results obtained not only provide information that is not easily observed quantitatively by other methods, but also reveal the full field response of the fabric during impact, which was not previously recorded in great details. The effect of boundary confinement was tested to guarantee the consistence and the reproducibility of the data set, which is important for the purpose of validating simulation models. In addition to the displacement history, the residual energy was obtained for each of the three projectiles at several 12

21 impact speeds. A linear relation exists between the dissipated energy and the impact energy at low impact speeds. Whereas, at high impact speeds, the energy dissipated is proportional to the number of broken yarns. 13

22 5. References 1. Tan, V.B.C.; Lim, C. T.; Cheong, C. H. Perforation of High-strength Gabric by Projectiles of Different Geometry. International Journal of Impact Engineering 2003, 28, Karahana, Mehmet; Kus, Abdil; Erenc, Erenc. An Investigation into Ballistic Performance and Energy Absorption Capabilities of Woven Aramid Fabrics. International Journal of Impact Engineering 2006, 35, Cork, C. R.; Foster, P. W. The Ballistic Performance of Narrow Fabrics. International Journal of Impact Engineering 2007, 34, Roylance, David; Wilde, Anthony; Tocci, Gregory. Ballistic Impact of Textile Structures; AMMRC TR 73-8, February Praga-Landa, B.; Hernandez-Olivares, F. An Analytical Model to Predict Impact Behavior of Soft Armours. International Journal of Impact Engineering 1995, 16, Tan, V.B.C.; Ching, T. W. Computational Simulation of Fabric Armour Subjected to Ballistic Impact. International Journal of Impact Engineering 2006, 32, Shahkarami, A.; Vaziri, R. A Continuum Shell Finite Element Model for Impact Simulation of Woven Fabrics. International Journal of Impact Engineering 2007, 34, Grujicic, M.; Bell, W. C.; He, T.; Cheeseman, B. A. Development and Verification of a Meso-scale Based Dynamic Material Model for Plain-woven Single-ply Ballistic Fabric. Journal of Material Science 2008, 43, Rao, M. P.; Duan, Y.; Keefe, M.; Powers, B. M.; Bogetti, T. A. Modeling the Effects of Yarn Material Properties and Friction on the Ballistic Impact of a Plain-weave Fabric. Composite Structures 2009, 89, Wang, Youqi; Miao, Yuyang; Swenson, Daniel; Cheeseman, Bryan A.; Yen, Chian-Feng. Digital Element Approach for Simulating Impact and Penetration of Textiles. International Journal of Impact Engineering 2010, 37, Lomov, S. V.; et al. Full-field Strain Measurement for Validation of Meso-FE Analysis of Textile Composites. Composites: Part A 2008, 39, Lomov, S. V.; et al. Full-field Strain Measurements in Textile Deformability Studies. Composites 2008, 39,

23 13. Weerasooriya, T.; Gunarsson, C. A.; Moy, P. Measurement of Full-field Transitent Deformation of the Back Surface of a Kevlar KM2 Fabric During Impact for Material Model Validation. Proceeding of the 2008 Int. Cong. Expo. On Experimental Mechanics and Applied Mechanics, Orlando, FL, June Chocron, S.; et al. Measurement of Strain in Fabrics Under Ballistic Impact Using Embedded Nichrome Wires. Part I: Technique. International Journal of Impact Engineering 2009, 36,

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25 Appendix A. Displacement Tables Table A mm sphere, 5.08 cm dia. clamp. 17

26 Table A Caliber RCC, 5.08 cm dia. clamp. 18

27 Table A Caliber FSP, 5.08 cm dia. clamp. 19

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29 Appendix B. Residual Energy Tables Table B mm sphere, 5.08 cm dia. clamp. Impact Residual Impact Residual Dissipated speed (m/s) speed (m/s) Energy (J) Energy (J) Energy (J) Table B Caliber RCC, 5.08 cm dia. clamp. Impact Residual Impact Residual Dissipated speed (m/s) speed (m/s) Energy (J) Energy (J) Energy (J)

30 Table B Caliber FSP, 5.08 cm dia. clamp. Impact Residual Impact Residual Dissipated speed (m/s) speed (m/s) Energy (J) Energy (J) Energy (J) Table B mm sphere, cm dia. clamp. Impact Residual Impact Residual Dissipated speed (m/s) speed (m/s) Energy (J) Energy (J) Energy (J)

31 No. of Copies Organization No. of Copies Organization 1 ADMNSTR ELEC DEFNS TECHL INFO CTR ATTN DTIC OCP 8725 JOHN J KINGMAN RD STE 0944 FT BELVOIR VA HCS US ARMY RSRCH LAB ATTN IMNE ALC HRR MAIL & RECORDS MGMT ATTN RDRL CIM L TECHL LIB ATTN RDRL CIM P TECHL PUB ADELPHI MD HC US ARMY RSRCH LAB ATTN RDRL CIM G T LANDFRIED BLDG 4600 ABERDEEN PROVING GROUND MD HCS US ARMY RSRCH LAB ATTN RDRL WMM A E WETZEL R MERRILL ATTN RDRL WMM B T BOGETTI B CHEESEMAN B POWERS M VANLANDINGHAM T WEERASOORIYA C-F.YEN J YU ATTN RDRL WMM D S WALSH L VARGAS-GONZALEZ ATTN RDRL WMM E P DEHMER ATTN RDRL SLB D JAMES GURGANUS ATTN RDRL SLB D DIXIE HISLEY ATTN RDRL WMP B CHRISTOPHER HOPPEL REUBEN KRAFT ATTN RDRL WMP D BRAIN SCOTT ABERDEEN PROVING GROUND MD HC PAUL CAVALLARO NAVAL UNDERSEA WARFARE CENTER CODE 70T ENGINEERING TEST & EVALUATION DEPARTMENT 1176 HOWELL STREET NEWPORT, RI HC KANSAS STATE UNIVERSITY DEPT. MECHNICAL AND NUCLEAR ENGINEERING ATTN: PROF. YOUQI WANG 3002 RATHBONE HALL MANHATTAN, KS HC UNVIERSITY OF DELAWARE DEPT. MECHNICAL ENGINEERING ATTN: PROF. MICHAEL KEEFE 107 SPENCER LABORATORIES NEWARK, DE HC MASSCHUSETTS INSTITUTE OF TECHNOLOGY DEPT. MATERIALS SCIENCE AND ENGINEERING ATTN: PROF. DAVID ROYLANCE OFFICE CAMBRIDGE, MA TOTAL: 26 (1 ELEC, 25 HCS) 23

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