Experimental and numerical investigation on the perforation resistance of double-layered metal shields under high-velocity impact of soft-core projectiles

Multi-layered metal shields have been extensively investigated in the past, mainly studying the effect of layering, spacing and order of plates of different materials. However, at present is not feasible to predict the effect of layering and spacing for a particular case but only general pattern can be considered. Some investigations based on numerical simulations showed that the multi-layered configuration made by layers of different metals could be a promising solution in terms of weight reduction of the shield but, different authors obtained contradictory results and comprehensive experimental investigation is still missing. Thus, the scope of this study is to evaluate the perforation resistance of double-layered metal shields constituted by a high-strength steel and an aluminum layer when impacted by a soft-core projectile. It was found that the multi-layered configuration constituted of two layers of different metals, is less efficient than the monolithic configuration. Furthermore, numerical models were developed to increase the understanding of the problem. It was necessary to use an alternative to the commonly used FE method to model extreme deformation occurring in soft-core projectiles in such kinds of scenario. In particular, the SPH method was implemented providing a detailed parametric study of the most relevant numerical parameters. The SPH method was thus exploited to study different configurations of the double-layer target, and it was found that the specific ballistic energy depends on the ratio between the two layers of the target.