Fracture toughness of niobium/alumina interfaces: an analysis based on a micromechanical model

Abstract

The fracture toughness is predicted for an interface between niobium and alumina. It is assumed that voids at the triple points of grain junctions on the interface are the sites of cleavage decohesion. These voids are treated as microcracks and the plastic zone is modelled by a cohesive zone of constant shear stress. The interaction between the microcrack and the main crack is studied using an integral equation approach. The fracture toughness is calculated via various fracture criteria and compared against experimental data. Scatter in the experimental data is related to the variability in microdefect size.