High-toughness silicon carbide as armor

Silicon carbide, with single-edge precracked beam (SEPB) toughness greater than 7 MPa center dot m(1/2), was made by hot-pressing using Al-B-C (ABC) or Al-Y2O3 (YAG) as additives. The hardness of SiC processed with a liquid phase was always less than SiC densified without a liquid phase despite having a similar or finer grain size. With increasing Al content, the ABC system changed from trans- to intergranular fracture with a drop in hardness and a two- to threefold increase in SEPB toughness. Strength and Weibull modulus for materials processed with a liquid phase were higher than those of solid-state densitied SiC. Ballistic testing, however, did not show any improvement over SiC densitied with B and C additives. Depth of penetration was controlled by hardness of the SiC-based materials, while V-50 values for 14.5 mm WC-Co cored projectiles were in the range of 720-750 m/s for all materials tested.