A possible mechanism for the difference in ballistic performance between sapphire and spinel

The contradictory finding that sapphire has advantages in most mechanical properties but is inferior to spinel in ballistic performance has been re-examined. The ballistic performance of sapphire and spinel against armor-piercing-incendiary (API) projectiles of caliber 7.62 mm was explored through experiments and numerical simulations. During the parameterization of the Johnson-Holmquist 2 (JH2) model, several assumptions concerning the material constants were suggested. The observed agreement between experiments and numerical simulations validated the simulation method. On this basis, a parametric study was carried out in which some of the JH2 parameters for sapphire were modified to those for spinel. The results showed that ceramics with lower tensile strength and lower Poisson's ratio tend to form a larger fracture cone, which contributes to higher ballistic resistance by spreading the load over a larger area. This work would offer new insight into the complex relationship between mechanical properties and ballistic performance.