A STUDY OF FRAGMENTATION IN THE BALLISTIC IMPACT OF CERAMICS

Experiments in which both confined and unconfined ceramic targets are perforated by pointed and blunt projectiles are described, and a correlation is established between increased degree of fragmentation and reduced ceramic toughness. Front confinement of the ceramic results in greater overall fragmentation, however fewer, very fine fragments are produced for confined targets compared to unconfined targets. By attributing the fine fragments principally to crushing ahead of the impacting projectile, and coarse fragmentation to the interaction of stress relief waves, the effects of confinement can be qualitatively explained in terms of a simple model for loading and stress relief during perforation. The use of blunt projectiles increases the degree of fragmentation in those cases where the ceramic strength itself is insufficient to fracture the tip on impact. Measurements of fractured ceramic surface area and calculations of fracture work demonstrate that very little of the projectile kinetic energy is consumed in creating new ceramic fracture surface, and it is shown that a high proportion of the projectile impact kinetic energy is redistributed to residual kinetic energy of ejected ceramic debris. For cases where the projectile does not deform during penetration it is possible to derive a value for the average pressure resisting the penetrator. The ballistic efficiency of the ceramic increases with hardness for the lower strength ceramics, however, for the hard ceramics, where the principal influence of the ceramic is to destroy the projectile nose and create an inefficient penetrator, it is found in these tests that the residual penetration depths are similar, and ballistic efficiency is then unrelated to ceramic strength.