Experimental study and finite element modeling of woven fabrics

Woven fabrics are used in many applications, including ballistic armors, propulsion engine containment systems and fabric reinforced composites. In order to facilitate the design and improvement of such applications, the author conducted static and dynamic tensile tests to obtain the material properties of Kevlar 49 fabric and to investigate the strain-rate effect. The author also investigated the Poisson's ratio and shear properties by conducting biaxial tests and picture frame test under quasi-static condition. Single yarn pull-out experiments were used to study the phenomenon of yarn slip and to characterize the frictional forces that oppose it. A simplified analytical model was developed to simulate the pull-out behavior and to relate to the experimental results. A three-dimensional finite element model was proposed to simulate the single yarn pullout behavior. The results show that both the friction between yarns and transverse preload influenced the pull-out force significantly.;A material model suitable for Kevlar 49 fabric was proposed and implemented into LS-DYNA, commercial Finite Element (FE) software, through a user defined subroutine. Two different modeling configurations, which are single FE layer and multiple FE layer, were used to simulate the ballistic tests conducted at NASA Glenn research center. Both the shear properties of the fabric and the parameters used in Cowper-Symonds (CS) model which accounts for strain-rate effect on material properties were optimized to achieve close match between the FE simulation and experimental data. The friction between the fabric layers was considered as an important factor in the ballistic performance of the fabric in the multi-layer model. Sensitivity analysis was carried out to study the effect of the coefficient of friction on the simulation results.