A model for ballistic impact on multi-layer fabric targets

An analytical model has been developed in this paper for the ballistic impact behavior of two-dimensional woven fabric composites of interest in body armor applications. The target in this model was assumed as a square with a length L and made by n layers fabric with no bonding between layers and clamped boundary condition. Each thin layer was assumed to have plain weave with linear-elastic mechanical properties. The penetration process of flat-faced cylindrical projectiles based on conservation of momentum and wave theory was simulated by this model. Using the analytical formulation, ballistic limit, surface radius of the cone formed and projectile velocity during perforation were predicted for typical multi-layer woven fabric. Also the model allowed variation of spacing between the layers in order to study their combined effects on the ballistic performance of the system. The results obtained from the present model showed that ballistic limit for constant number of layers, when increasing layer spacing would decrease. This reduction however stopped after a specific distance between layers which was named layers decoupling threshold. Further increases in the gaps between layers did not have any effect on the performance of the armor. In thick armors fracture in layers started at a velocity much less than the ballistic limit velocity. In a thin one (with same number of layers) it started at a velocity near ballistic impact velocity and the total layers fracture happened in a shorter time. The effect of target dimensions on its ballistic performance was also been studied in this model which could be used for armor dimensions optimization. Comparison between results of new model with Dupont experimental data and Van Gorp semi-experimental formula showed a very good correlation. (C) 2010 Elsevier Ltd. All rights reserved.