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-fracture of ceramics toughened by crack bridging was discussed using a constant crack closure stress model including irreversible energy loss in the bridging region during crack propagation. The Irwin similarity relationship could not be applied to the bridged crack without modifying stress intensity factor and energy release rate considering the crack closure stress and the energy loss. Moreover, the fracture toughness was not simply related with the work-of-fracture even if the modified Irwin similarity was applied. The fracture toughness was determined as a function of the crack closure stress and the length of the bridging region regardless of the energy loss. On the other hand, the work-of-fracture of bridged crack was increased by the irreversible energy consumption as well as crack closure stress.