Impact response of layered steel–alumina targets

The efficacy of a ceramic in protecting against penetration by high velocity projectiles depends not only on its hardness but also on its resistance to flow after comminution. Here we investigate experimentally the response of a model armor system comprising an alumina tile and two steel face sheets subject to impact by steel spherical projectiles. Complementary experiments are performed on the face sheet materials and the ceramic alone in order to gain insights into the inelastic responses of the constituent materials. A parallel numerical modeling study is performed of the system response with emphasis on the shape of the back face following impact. To this end, we employ the ceramic deformation model developed by Deshpande and Evans and modified here to account for dilatational softening following full comminution. Comparisons between model predictions and experimental measurements demonstrate the important role of granular flow. Preliminary parametric studies further suggest that additional effort is required to understand the transition in mechanical response of a ceramic as it transforms from a monolithic solid to a densely-packed granulated medium.

► We investigate experimentally the impact response of steel/alumina/steel trilayers. ► We assess the utility of the Deshpande–Evans constitutive law for ceramic deformation. ► The DE model has good predictive capability at moderately high impact velocities. ► We propose a modification to DE to allow for dilatational softening after comminution. ► The proposed modification gives better agreement between experiment and model.