Mesoscale Simulations of Ballistic Impact: From Woven Fabrics to Unidirectional Composites

Abstract

Following a careful step-by-step validation, simulations of impact on woven fabrics of Kevlar, PBO, and Dyneema were performed. The procedure consisted on, firstly, validating the impact on a single yarn and checking that the transverse wave velocity and the critical velocity matched the theoretical and experimental values observed using an ultra-high-speed camera. Secondly, a single woven layer was created using the “validated†yarns. The pyramid that forms during normal impact on the single layer propagates similarly to the transverse wave of a single yarn (but at a different velocity). This pyramid propagation velocity was also compared and validated with the tests and is a characteristic of the fabric material. Finally, using the single layer from the second step, a lay-up with multiple layers was impacted and the position of the apex and base of the pyramid created on the back was measured in the simulations and tests producing a validated multi-layer model. An additional validation performed on the multi-layer model was to compare the ballistic limit of simulations and tests. The multi-layer fabric model was further explored by adding matrix to create a woven composite. Various meshes were created, always respecting the total areal density, matrix volume fraction, and porosity. The model selected was able to reproduce both the apex and pyramid motion in the composite and provide good estimates of the ballistic limits for thick targets. Unidirectional composites have a very different architecture, i.e. they are made of individual fibers embedded in a matrix in a 0/90 lay-up. An FEA model cannot simulate all the individual fibers (microscale) and their interactions because of the high computational cost. Instead, the strategy adopted was to use a mesoscale model where the fibers of a layer are bundled in a flat yarn. The results and validation of this model as well as future challenges will also be presented in this paper.