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 corre lation is established between increased degree of fragmentation and re duced ceramic toughness. Front confinement of the ceramic results in g reater overall fragmentation, however fewer, very fine fragments are p roduced for confined targets compared to unconfined targets. By attrib uting the fine fragments principally to crushing ahead of the impactin g projectile, and coarse fragmentation to the interaction of stress re lief waves, the effects of confinement can be qualitatively explained in terms of a simple model for loading and stress relief during perfor ation. The use of blunt projectiles increases the degree of fragmentat ion in those cases where the ceramic strength itself is insufficient t o fracture the tip on impact. Measurements of fractured ceramic surfac e area and calculations of fracture work demonstrate that very little of the projectile kinetic energy is consumed in creating new ceramic f racture surface, and it is shown that a high proportion of the project ile impact kinetic energy is redistributed to residual kinetic energy of ejected ceramic debris. For cases where the projectile does not def orm during penetration it is possible to derive a value for the averag e pressure resisting the penetrator. The ballistic efficiency of the c eramic increases with hardness for the lower strength ceramics, howeve r, for the hard ceramics, where the principal influence of the ceramic is to destroy the projectile nose and create an inefficient penetrato r, it is found in these tests that the residual penetration depths are similar, and ballistic efficiency is then unrelated to ceramic streng th.