Crashworthiness of Composite Structures with Various Fiber Architectures

Advanced textile composite structures, such as braids and fabrics, are showing promising characteristics for energy absorption. However, modeling of these composite structures is quite challenging because of their complicated architecture, varied fiber/matrix combinations, and the failure mechanisms associated with them. Unfortunately, none of the existing material models is capable of simulating diverse failure behaviors observed during crushing of these composite structures. This paper will present a material model that can simulate the crushing response of composite structures with different fiber architectures. The material model identifies a smallest repeatable unit (i.e. unit-cell) within the textile composite and considers fiber modeling, strain rate effect, tow rotation and progressive failure criteria at tow level. The composite tow is assumed to be transverly isotropic, and modeled using an elastic- viscoplastic constitutive law. A DyCrash (Dynamic Crash) module is developed and implemented in LS-DYNA® as a user routine. The module is currently being validated for Kevlar fabrics. Results are presented for 00/900 and ± 450 Kevlar fabric coupons. A methodology is developed to back calculate the yarn properties from available Kevlar fabric test data using DyCrash.