A STUDY OF THE PERFORATION OF ALUMINUM LAMINATE TARGETS

Experiments are described in which laminated aluminium alloy targets, of a variety of configurations, are perforated by flat-ended and conic al penetrators. Target ballistic limit velocities are determined and t he results are used to evaluate energy absorption mechanisms and to co mpare deformation and failure modes. It is demonstrated by modelling t hat increasing the numbers of layers in multi-layer targets increases the tensile stretching work in perforation. However, since this is acc ompanied by reductions in other work terms, only small changes are fou nd in total energy absorption, despite large changes in failure geomet ry. The propensity to stretch and bend or to shear a plug is affected by target exit-side layer thickness relative to projectile diameter, w ith thick layers tending to favour plugging by a shear mechanism. In t argets with thin exit-side layers tensile, rather than shear, mechanis ms are apparent in failure and plug separation. A model is developed w hich treats the perforation of laminates as a two-stage process of ind entation on the impact side, and either shear or dishing failure on th e exit side, depending on target configuration. For the cases examined the model gives good predictions of the ballistic limit, including di stinguishing between differently configured laminates, and correctly a ccounts for the effect of projectile nose shape. As part of this proce ss, the estimation of dishing energies is improved by accounting for t he effect of tangential curvature. In spite of its success in predicti ng ballistic limits, the model involves some simplifications which do not mirror experimental observations. A notable example is its neglect of the detailed geometric features of deformation. Nevertheless, the model can be used to elucidate design features for laminated targets. (C) 1998 Aeronaurical and Maritime Research Laboratory. Published by E lsevier Science Ltd. All rights reserved.