The effect of through-thickness cracks on the ballistic performance of ceramic armour systems

Full width through-thickness cracks were introduced into the ceramic tiles of ceramic faced composite armour panels. The ballistic limit velocity for projectiles striking directly on the crack was measured and compared with undamaged panels. The effect of the cracks was to lower the V-50 ballistic limit velocity to 744 m s(-1) compared to 764 m s(-1) for undamaged panels, a drop of only 3%. This means that the presence of cracks in a ceramic armour tile should not be sufficient reason to require replacement of the panel a fact of some importance given the likelihood of damage in the military environment. It is proposed that the small value of the reduction in performance is observed because the cracked ceramic is still effectively confined by the presence of a well bonded composite backing and a frontal spall shield. The presence of a large crack at the impact point has little effect as the ceramic in this area is anyway extensively comminuted ahead of the projectile upon impact. The backing and spall shield conserve the structural integrity of the panel and this acts to contain the radial stresses generated by the impact event. The performance of the armour system has also been assessed by measurement of the V-o ballistic limit velocity determined from residual momentum of penetrating projectiles and armour fragments. The standard panels showed a V-o of 743 m s(-1) compared to 699 m s(-1) for the pre-cracked panels.