13th International Conference on Fracture June 16–21, 2013, Beijing, China -9- 0 40 80 120 Strain Rate, s-1 80 100 120 140 160 Young's Modulus, GPa Kevlar 49 Single Yarn L0 = 50 mm L0 = 25 mm (a) 0 40 80 120 Strain Rate, s-1 1200 1600 2000 2400 Tensile Strength, MPa Kevlar 49 Single Yarn L0 = 50 mm L0 = 25 mm (b) 0 40 80 120 Strain Rate, s-1 0.015 0.02 0.025 0.03 0.035 Maximum Strain, mm/mm Kevlar 49 Single Yarn L0 = 25 mm L0 = 50 mm (c) 0 40 80 120 Strain Rate, s-1 16 20 24 28 32 Toughness, MPa Kevlar 49 Single Yarn L0 = 50 mm L0 = 25 mm (d) Figure 6. Strain rate effect on the dynamic material properties of single yarn: (a) Young’s modulus, (b) tensile strength, (c) maximum strain, and (d) toughness 4. Conclusions This work investigated the mechanical behaviors of Kevlar 49 fabric and single yarn under quasi-static and dynamic tensile loadings. Weibull parameters have been obtained to characterize the considerable scatter in the mechanical properties due to different amount and distribution of imperfections in the fabric and yarn specimens. The following conclusions can be reached: (1) Under quasi-static loading, the stress-strain response of Kevlar 49 fabric exhibits non-linear and orthogonal behavior in both warp and fill directions, and the fabric can deform up to 20% before the stress decreases to zero. The Young’s modulus is almost identical to one another in both directions. The major difference between warp and fill directions is the crimp strain, the tensile
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