Abstract: The failure mechanisms of graphene modified B₄C composites with and without TiB₂ under the penetration of 12.7 mm armor-piercing projectiles were studied for the development and optimization of new lightweight materials for bulletproof armor. The Vickers hardness, bending strength and fracture toughness of the two ceramic matrix composites were obtained by using Vickers hardness tester, three-point bending method and single edge notched beam method. The anti-penetration performances of the two composites penetrated by 12.7 mm armor-piercing projectiles are studied through the residual penetration depth experiment, which are quantitatively characterized by the protection coefficient. A scanning electron microscope (SEM) was used to analyze the macroscopic damage morphologies of 7075 aluminum alloy back-plates and ceramic fragments to study the failure mechanism of ceramic and the strengthening mechanisms of TiB₂ and graphene. Experimental results show that the addition of TiB₂ can enhance the properties of graphene modified boron carbide ceramics. Compared with the material without TiB₂, the Vickers hardness, bending strength and fracture toughness of the material containing 14wt.% TiB₂ are increased by 19.66%, 24.06% and 19.70%, respectively, and its anti-penetration performance is increased by 15.11% under the penetration of 12.7 mm armor-piercing projectiles at 750 m/s. It is shown that the B₄C ceramic matrix composite exhibits a variety of energy absorption modes and a better crushing resistance due to the addition of TiB₂ and the strengthening effect of graphene, which is the main reason for the improvement of anti-penetration performance.

Key words: B₄C/TiB₂compositeceramic, dynamicfailure, graphene, degreeofparticlesfracture