Experimental and theoretical study of cone angle in alumina tiles under ballistic impact

The ceramic cone formed within the ceramic tiles provides effective ballistic resistance. Although the critical velocity of ceramic cone formation has been extensively studied, the cone angle in ceramic tiles after crack initiation is still unclear, which is important for understanding the anti-penetration process. In this paper, the cone angle in ceramic tiles is systematically investigated both experimentally and theoretically. First, the dynamic failure process of ceramic tiles is characterized by means of ballistic impact experiments, and the results show that the cone angle gradually decreases with the increase of the thickness of the ceramic tile, while it is independent of the impact velocity. Then, based on the minimization of deformation energy and fracture energy, a theoretical model is established for the first time to predict the cone angle, which takes into account the strain rate effect on tensile strength. This model can well explain the effect of the thickness, impact velocity and fracture properties of the ceramic material on the cone angle obtained in experiments. Increasing the thickness of the ceramic tiles results in larger ceramic fragments while the generated fracture energy declines. This leads to a decrease in the cone angle. Moreover, an increase in the fracture toughness or tensile strength of the ceramic material enhances the resistance to crack propagation, and the generated fracture energy decrease, resulting in a decrease in the cone angle. However, the cone angle does not change much with impact velocity because the impact velocity does not change the stress field distribution of the ceramic tile. This study is meaningful for understanding the ballistic resistance of ceramic tiles.