Discrimination of basic influences on the ballistic strength of opaque and transparent ceramics

The study addresses (1) the impact (i) of ceramic microstructures and (ii) of the deformation of the ceramic/backing composite on ceramic fragmentation and resulting projectile erosion, and (2) other materials influences which may affect the abrasive destruction of the penetrator via the mechanical properties of the ceramics (Young's modulus E, hardness, HEL, bending/compressive strength, KIc). Regarding the highly dynamic interaction, the study had to find out whether all mechanical parameters must be dynamically recorded for understanding the ballistic performance. The results show that the ballistic strength of Al2O3 and spinel ceramics and single crystals with different backings (steel, aluminum, glass) is subject to a 3-fold hierarchy of influences: 1. Top priority is the cera mic fragmentation governed by the microstructure and by the dynamic stiffness (not simply by the Young's modulus E) of the ceramic/backing target. These influences also affect the relative importance of dwell and penetration phases. 2. On a middle rank, E and the dynamic stiffness of the ceramic are responsible for the projectile deformation during dwell. 3.On penetration, the abrasive benefit of a high ceramic hardness depends on the size of the ceramic debris, i.e. on ceramic fragmentation; this effect increases the projectile erosion by ceramics with glass backing compared with Al backing. In contrast, all strength data are weakly correlated with the ballistic figure. This hierarchy explains apparently contradictive findings of the past.