This paper presents a comparison of behavior and energy absorption of neat Kevlar fabric and polymer matrix composites under high velocity impact loading. Two types of matrices including rubber and thermoset (epoxy) matrices were used in order to study the effect of a hard and brittle matrix compared with the soft and flexible matrix on energy absorption of the composite. Moreover, two types of rubber matrix with high hardness (HH) and low hardness (LH) were used in this study to investigate the effect of rubber matrix formulation on impact resistance of composites. Ballistic impact tests were performed by firing a 10 mm hemispherical projectile onto neat fabric and composites in a velocity range of 30 m/s to 150 m/s for two-and four-layer samples. Results show that the matrix affects the ballistic performance of composites significantly. Rubber matrix enhances the energy absorption of the fabric by keeping composite flexibility. Increase the number of layers for Kevlar/rubber composite results in better ballistic performance. On the contrary, the thermoset matrix leads to an inflexible composite that restricts the fabric deformation and has a negative effect on the fabric's ballistic performance. Finally, damage mechanisms were discussed in detail for each sample.

This study presents the response of rubber panels subjected to high velocity impact loading. The vulcanization characteristics of compositions have been obtained by using rheometer and the panels have been prepared at the appropriate temperature and pressure. The mechanical properties and impact performance of rubber panels is altered by the variation of compound ingredients. To investigate the effect of compound ingredients, two types of rubber panel have been prepared and mechanical properties and impact resistance of the panels have been measured by high velocity impact tests. A finite element simulation has been performed to investigate numerically the ballistic performance of rubber panels. Rubber panels was modeled by using LS-DYNA software and employing the experimental results of tensile test to characterize the behavior of rubber panel. The findings reveal a good agreement between numerical and experimental data. According to Experimental results, the ballistic limit of low and high hardness rubber panels was 80 and 94 m/s respectively that shows energy absorption of rubber panels increases as filler loading increases.

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In this paper closed form analytical solution for stress components of thick spherical shell made of transversely isotropic functionally graded hyperelastic material subjected to internal and external pressure is presented. Reinforced neo-Hookean strain energy function with variable material parameters is used to model pressure vessel material. The material constants of strain energy function are graded along the radial direction based on a power law function and have been calculated from experimental data by using LevenbergMarquardt nonlinear regression method. Stress components and stretches of pressure vessel have been obtained for centrally symmetric condition. Following this, profiles of extension ratio, deformed radius of sphere, normalized radial stress and normalized circumferential stress are plotted as a function of radius of sphere in the undeformed configuration for different material inhomogeneity parameter m . The obtained results show that the inhomogeneity properties of FGMs structure parameter have a significant influence on the displacement, stretch and stresses distribution along the radial direction. KeywordsTransversely isotropic hyperelastic material, thick-walled spherical shells, finite deformation, functionally graded material.

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