Simulation of fracture behavior in particle-dispersed ceramic composites

A two-dimensional crack path is simulated in particle-dispersed ceramic composites along with the related variation of fracture resistance with crack extension. The direction of crack propagation is influenced by the geometrical crack shape and localized residual stresses due to the thermal expansion mismatch between particle and matrix. The simulation is conducted for both a SiC matrix composite dispersed with Al2O3 particles and an Al2O3 matrix composite dispersed with SiC particles, under an assumption of hard particles. In the SiC-Al2O3(p) composite, a crack propagating near the Al2O3 particles has a tendency to be repelled due to the residual tensile stress in the radial direction around the particles, and the entire fracture resistance shows a lower value than the matrix toughness. In the Al2O3-SiC(p) composite, a crack is attracted by the SiC particles. Due to the residual compressive stress in the radial direction around the SiC particles, the fracture resistance increases up to five times the matrix toughness when the crack propagates along the interface. The apparent fracture resistance of the Al2O9-SiC(p) composite shows a higher value than the matrix toughness, and an increasing R-curve behavior with crack extension is predicted. The approximately estimated two-dimensional fracture toughness of the Al2O3-SiC(p) composite increases with the volume fraction of particles, while it decreases in the SiC-Al2O3(p) composite. (C) 1998 Elsevier Science Ltd.