Finite element modeling of transverse impact on a ballistic fabric

A 3D finite element analysis model is created using LS-DYNA to simulate the transverse impact of a rigid right circular cylinder onto a square patch of plain-woven Kevlar fabric. The fabric is modeled to yarn level resolution and relative motion between yarns is allowed. A frictional contact is defined between yarns and between the fabric and the projectile. Three different boundary conditions are applied on the fabric: four edges left free; two opposite edges clamped; four edges clamped. Results from the modeling effort show that during initial stage of the impact, the projectile velocity drops very quickly. There exists an abrupt momentum transfer from the projectile to the local fabric at the impact zone. When the impact velocity is low, the fabric boundary condition plays an important role at later stages of the impact. It significantly affects the fabric deformation, stress distribution, energy absorption and failure modes. When the impact velocity is high enough to cause the yarns to break instantaneously, the fabric fails along the periphery of the impact zone and the fabric boundary condition does not take any effects.