The ballistic failure mechanisms and sequence in semi-infinite supported alumina tiles

The basic ballistic failure mechanisms and their sequence occurring in dense alumina tiles during projectile penetration were investigated. The alumina tiles were supported by semi-infinite support blocks made of three different materials. Initially, a drop-weight test (DWT) was used to gain an insight into the damage mechanisms and sequence during quasi-static impact conditions. The quasi-static damage mechanisms were compared with the damage obtained in 0.3 cal. armor-piercing tests (APT). The DWT's results suggested the following sequence of quasi-static failure mechanisms: Radial tensile cracks, associated with the low tensile strength of the ceramic formed initially, as a result of the bending induced by local deformation at the opposing surface. Subsequently, a shear-dominated cone crack propagated from the edge of the contact zone. If sufficient energy was available, crushing of the material beneath the contact zone developed during the final stages of failure. It is shown that these so-called "quasi-static" damage mechanisms, identified from the DWT's, also corresponded to the damage mechanisms and sequence during APT's.