Ceramics With High Fracture Toughness

The fracture toughness of zirconia alumina and silicon nitride ceramics zirconia and alumina single crystals silicon carbide as well as silicon nitride ceramic particulate composites silicon nitride laminated composites and other ceramics materials were studied by a single edge v notched beam sevnb method.

Ceramics with high fracture toughness. High work of fracture fi ber reinforced ceramics consisting of carbon fiber rein forced glasses and glass ceramics were first demonstrated in 1972 accompanied by the first complete model of composite behavior. Environmentally assisted subcritical crack extension slow crack growth scg and r curve behavior. Ceramic materials are characterized with respect to fracture toughness by measuring the energy required for a defect of known dimensions to propagate and become a crack. The fracture toughness values of the 3y tzp ceramics were determined to be in the range of 4 0 6 2 mp m 1 2 and these values did not vary significantly over a wide sintering range.

When evaluating ceramic or glass fracture toughness kic there are two major complications. The fracture toughness of composites made by combining engineering ceramics with engineering polymers greatly exceeds the individual fracture toughness of the constituent materials. Compared with monolithic ceramics laminated ceramics showed multiple fractures instead of typical brittle fractures. 27 prepared laminated zrb 2 bn ceramics with a flexural strength of 381 mpa and a fracture toughness of 13 31 mpa m 1 2.

The higher the fracture toughness the better the resistance to crack propagation. Fracture toughness k1c is one of the most important mechanical properties of the ceramics which indicates the ability of the ceramic to resist crack propagation. Fine ceramics generally have low toughness. However zirconia which is used to make ceramic knives exhibits high fracture toughness.

The fracture toughness of advanced ceramics is often measured using an indentation technique.