Abstract
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 toughening by crack bowing and crack deflections. Three models of the crack extension process were set up. First, only crack bowing occurs (bowing model); 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 the particle but in the case of sphere particle dispersed glass and the deflection mixture models, it increased by 30% at most.
Then, the fracture 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 particles was normal to the crack plain, the toughening of the composites in the deflection and mixture models became higher than those of the sphere particles dispersed composites as the particle is inhomogenized. Nevertheless, when the major axis of ellipsoidal particles was parallel 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.
