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Research Papers

Modeling of Fabric Impact With High Speed Imaging and Nickel-Chromium Wires Validation

[+] Author and Article Information
Sidney Chocron1

e-mail: schocron@swri.edu

Trenton Kirchdoerfer, Nikki King, Christopher J. Freitas

 Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78238

1

Corresponding author.

J. Appl. Mech 78(5), 051007 (Jul 28, 2011) (13 pages) doi:10.1115/1.4004280 History: Received November 23, 2010; Revised May 23, 2011; Published July 28, 2011; Online July 28, 2011

Ballistic tests were performed on single-yarn, single-layer and ten-layer targets of Kevlar® KM2 (600 and 850 denier), Dyneema® SK-65 and PBO® (500 denier). The objective was to develop data for validation of numerical models so, multiple diagnostic techniques were used: (1) ultra-high speed photography, (2) high-speed video and (3) nickel-chromium wire technique. These techniques allowed thorough validation of the numerical models through five different paths. The first validation set was at the yarn level, where the transverse wave propagation obtained with analytical and numerical simulations was compared to that obtained in the experiments. The second validation path was at the single-layer level: the propagation of the pyramidal wave observed with the high speed camera was compared to the numerical simulations. The third validation consisted of comparing, for the targets with ten layers, the pyramid apex and diagonal positions from tests and simulations. The fourth validation, which is probably the most relevant, consisted of comparing the numerical and experimental ballistic limits. Finally for the fifth validation set, nickel-chromium wires were used to record electronically the waves propagating in the fabrics. It is shown that for the three materials the waves recorded during the tests match well the waves predicted by the numerical model.

Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Example image obtained during single yarn impact (test yarn 03). Impact velocity 477 m/s.

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Figure 2

Images recorded with Imacon camera for a single layer impact on Dyneema® . One image every 5 μs.

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Figure 3

Dyneema® single layer results. Experimental results are shown as symbols for the warp direction (DV) and for the fill direction (DH). The lines are the simulation predictions.

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Figure 4

Squares (1 cm  × 1 cm) of the fabric models developed: (upper left) Dyneema® , (upper right) PBO® , (lower left) KM2 850 denier and (lower right) KM2 600 denier

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Figure 5

Pyramid development for the .30 cal FSP impacting Dyneema® fabric. The pyramid corner is tracked manually to determine its position at different times: (a) 5 μs, (b) 15 μs, (c) 25 μs, (d) 35 μs.

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Figure 6

Perspective of the pyramid formed 35 microseconds after impact of an FSP on 10 layers of Dyneema® . (a) side view and (b) top view.

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Figure 7

KM2 single layer results. The symbols are the experimental results and the lines the numerical results. (a) 600 denier fabric and (b) 850 denier fabric.

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Figure 8

PBO® single layer results. The symbols show the experimental results while the LS-DYNA prediction is the thick line.

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Figure 9

Images recorded at 5 μs intervals with the Imacon camera for test # 38: 0.22 cal FSP versus ten layers of Dyneema® at 309 m/s. The projectile was stopped by the target in this test.

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Figure 10

Test and computation results are compared for the pyramid’s apex position and diagonal extent in a ten layer Dyneema® target. The symbols are data points from the tests and the lines are the numerical prediction. (a) apex position and (b) diagonal extent.

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Figure 11

Test and computation results are compared for the pyramid’s apex position and diagonal extent in a PBO® ten layer target. The symbols are data points from the tests and the lines are the numerical prediction.

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Figure 12

Test and computation results are compared for the pyramid’s apex position and diagonal extent in a ten layer KM2-850d target. The symbols are data points from the tests and the lines are the numerical prediction.

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Figure 13

Typical signals recorded by the NiCr wire. (a) Dyneema® and (b) KM2.

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Figure 14

Strain distribution inferred from the NiCr wires. (a) 10-layered targets and (b) full targets.

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Figure 15

Comparison of waves recorded with the NiCr wire on Dyneema® for test #38 and waves simulated with LS-DYNA. (a) Free boundaries in the simulations (TBD_18), (b) clamped boundaries (TBD_21).

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Figure 16

The NiCr waves on PBO® are compared for tests (thin continuous lines) and simulations (thick dashed lines, TBD_20). The projectile, a .22 cal FSP impacted at approx. 300 m/s. (a) test #626 and (b) test # 627.

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Figure 17

The NiCr waves on KM2 (850 denier) are compared for tests (thin continuous lines) and simulations (thick dashed lines, TBD_19). The projectile, a .22 cal FSP impacted at approx. 300 m/s. (a) test #120 and (b) test #121.

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