Enhanced Toughness SiC with High Hardness for Advanced Armor

"Recent efforts at engineering the microstructures of SiC have resulted in fracture toughness values that are 2-3 times that of conventionally sintered SiC. However, these methods of toughening have resulted in decreased hardness, a property that iscritical for armor applications. The proposed research attempts to toughen SiC without sacrificing hardness. The Phase I effort is based on toughening using two secondary phases. The first is a sintering aid that results in elongated SiC grains, whichtoughen by crack bridging and crack branching. The second, added at a much higher volume fraction, allows microcrack toughening to enhance the toughness of the composite material without sacrificing hardness. A Taguchi designed experiment is proposed tolook at interactions between the secondary phases, as well as other key variables. A 25 mm x 200 mm x 200 mm SiC composite tile having the target toughness and hardness will be delivered at the end of the Phase I research. Lightweight SiC with enhancedtoughness will allow improved protection for the Army, as well as law-enforcement agencies and private armored vehicles. This same material is expected to perform well in non-corrosive environments, such as nozzles for oil well drilling and water-jetcutting."