EFFECT OF IRREVERSIBLE ENERGY-LOSS ON THE FRACTURE-TOUGHNESS AND THE WORK-OF-FRACTURE OF CERAMICS TOUGHENED BY CRACK FACE BRIDGING

The relationship between the fracture toughness and the work-of-fractu re of ceramics toughened by crack bridging was discussed using a const ant crack closure stress model including irreversible energy loss in t he bridging region during crack propagation. The Irwin similarity rela tionship could not be applied to the bridged crack without modifying s tress intensity factor and energy release rate considering the crack c losure stress and the energy loss. Moreover, the fracture toughness wa s not simply related with the work-of-fracture even if the modified Ir win similarity was applied. The fracture toughness was determined as a function of the crack closure stress and the length of the bridging r egion regardless of the energy loss. On the other hand, the work-of-fr acture of bridged crack was increased by the irreversible energy consu mption as well as crack closure stress.