Effect of composite covering on ballistic fracture damage development in ceramic plates

This paper describes the damage development in ceramics with and without composite cover during ballistic impact. This is relevant for ceramic inserts in body armor that are often covered with a composite material. To study the effect of the cover on the damage development in the ceramic, projectile impact experiments were performed at sub-muzzle velocities on bare alumina tiles and plates covered with a fiberglass composite. In addition to the experiments, finite element simulations were performed. An atypical formulation was used; Arbitrary Lagrangian–Eulerian (ALE) for the projectile and Lagrangian for the ceramic target. For the ceramic target, an unconventional material model was chosen; the pseudo-geological model 72_R3 in LS-DYNA. Cracking damage in the recovered plates was characterized in a manner that clearly distinguished between cracking mechanisms and allowed the cracks to be tracked and quantified. In light of the common use of composite cover for ceramics in body armor, an unexpected result was found; that the covered plates showed significantly more damage than the bare plates. The simulations successfully matched details of the cracking patterns and elucidated the damage evolution in the ceramic plates. The simulation results explained the damage observations as the result of restraining effects, i.e. the restraining effect of the composite cover keeps the damaged ceramic in the path of the projectile resulting in increased damage.