Optimization of the nose shape of an impactor against a semi-infinite FRP laminate

A model is proposed to describe the penetration of a monolithic semi-infinite FRP laminate struck transversely by a rigid projectile with an arbitrary shape. The shape of the impactor that penetrates at a given depth of penetration (DOP) with the minimum impact velocity is found by the use of a numerical procedure for solving a corresponding non-classical variational problem. It is shown that the optimum shape depends on the given DOP which is assumed to be larger than the length of the nose of the impactor. For a relatively small DOP, the optimum impactor is a sharp, awl-shaped body. With increasing DOP, the optimal nose geometry of the impactor varies and becomes close to a blunt cone. It is proved analytically that a flat-nosed cylinder requires the maximum impact velocity in order to penetrate at a given DOP. Comparison of different projectile head shapes for penetration into a semi-infinite target is performed.