NUMERICAL-SIMULATION OF TOUGHENING BY CRA CK DEFLECTION AND BOWING OFELLIPSOIDAL PARTICLE DISPERSED GLASS MATRIX COMPOSITES

A numerical simulations of crack bowing and deflections was performed on glass matrix-alumina particulate composite to evaluate relationship between the aspect ratio of the ellipsoidal particle and the tougheni ng by crack bowing and crack deflections. Three models of the crack ex tension process were set up. First, only crack bowing occurs (bowing m odel); secondly, only crack deflection occurs (deflection model); and thirdly, both of them occur (mixture model). The numerical simulation revealed that in the case of the bowing model, the fracture toughness of composites increased monotonously with the fracture toughness of th e particle but in the case of sphere particle dispersed glass and the deflection mixture models, it increased by 30% at most. Then, the frac ture toughness of the composites whose aspect ratios were changed from 0.2 to 5 was calculated. The fracture toughness of the composites in the bowing model was almost unchanged from that of the sphere particle dispersed composites. Meanwhile, when the major axis of ellipsoidal p articles was normal to the crack plain, the toughening of the composit es in the deflection and mixture models became higher than those of th e sphere particles dispersed composites as the particle is inhomogeniz ed. Nevertheless, when the major axis of ellipsoidal particles was par allel to the crack plain, the fracture toughness of the composites was lower than that of the sphere particle dispersed composites and thus the fracture toughness of the composites was also inhomogenized as the particle was inhomogenized.