Numerical modelling of the compressive and tensile response of brittle materials under high pressure dynamic loading

Ceramic materials are commonly used as ballistic protection materials. The response of a ceramic to impact, perforation and penetration is complex and only limited physical instrumentation can be used in experiments. This paper demonstrates how a hydrocode, such as AUTODYN, can be used to aid in the understanding of the response of brittle materials to high pressure impact loading. While the penetration process is dominated by the material compressive thermodynamic and deviatoric response, the final damaged state of the material can be significantly influenced by the tensile behaviour. Modelling of the final damage state is important since this is often the only physical experimental information available. In this paper we present a unique implementation, in a hydrocode, of a tensile crack softening model for improved modelling of brittle materials in the tensile regime. Tensile failure initiation is based on principal stress while the post-failure tensile strength of the material is controlled through a damaging Rankine plasticity failure surface. The performance of the model is demonstrated with the relatively new meshless SPH technique; simulations of steel ball impacts onto alumina ceramic are presented and compared with experiments.