13th International Conference on Fracture June 16–21, 2013, Beijing, China -5- is due to the fact that the warp yarns have sustained more damage from weaving process and have higher initial crimps. The stress-strain curves of specimens tested are highly repeatable for both sizes and directions. = 0.01 = 0 = 0.02 = 0.04 = 0.08 = 0.16 Warp Fill 0 0.04 0.08 0.12 0.16 0.2 Engineering Strain, mm/mm 50 mm x 200 mm Specimen 0 500 1000 1500 2000 Engineering Stress, MPa Crimp Linear pre-peak region Linear post-peak region Nonlinear post-peak region Figure 3. Typical stress-strain relationship and fabric deformation under quasi-static uniaxial tension Table 1 Summary of Tensile Properties of Kevlar 49 Fabric Specimen Size (mm × mm) Material Direction Tensile Strength (MPa) Young's Modulus (GPa) Toughness (MPa) Ultimate Strain (mm/mm) Warp 1748 ± 56 117.2 ± 3.3 32.4 ± 3.0 0.0223 ± 0.0012 50×200 Fill 2013 ± 44 117.1 ± 3.0 33.9 ± 1.3 0.0201 ± 0.0010 Warp 1859 ± 109 117.9 ± 2.5 32.9 ± 1.4 0.0215 ± 0.0015 25×200 Fill 2055 ± 72 119.7 ± 4.0 33.2 ± 1.2 0.0200 ± 0.0009 25×280 Warp* 1776 ± 100 126.5 ± 4.6 26.9 ± 1.7 0.0197 ± 0.0014 25×355 Warp* 1811 ± 61 132.1 ± 5.8 27.1 ± 1.8 0.0181 ± 0.0008 *These tests were stopped once the load acting on the specimen fell below 222N.
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