Fragmentation of an armour piercing projectile after impact on composite covered alumina tiles

In a typical body armour system, a hard armour plate is often used in conjunction with a soft ballistic panel. The main purpose of the armour plate is to erode and fragment an impacting projectile, such as 7.62 mm armour piercing (AP) projectiles with a very hard material core. This is made possible by employing a single ceramic tile as the strike face. This tile is covered by a sheet material. The sheet cover may improve the ballistic performance by partly maintaining the integrity of the ceramic. In this study, the effect of adding a composite cover has been investigated experimentally by ballistic testing of different types of composite-covered targets. The targets were totally perforated by a 7.62 mm AP hard steel core projectile at near-muzzle velocities (around 800 m/s). The post-impact process was monitored by high speed video, and the resulting core fragments were collected and analysed. This allowed the core fragmentation, residual velocity and kinetic energy-loss to be quantified. The results showed that the core fragmentation and the kinetic energy-loss of the projectile were most significant for the targets with the composite-cover on the back of the alumina. For targets with four composite back-layers, and an increased areal density of 9.5%, the mass of the projectile core was reduced by 61%, while the kinetic energy was reduced by 84%. The residual velocity did not vary to the same extent between the different target configurations. The mechanism behind the positive effect of a back cover is believed to be delayed opening of tensile cracks that originate from the back of the ceramic, which gives more time for interaction with the penetrator.