EFFECT OF DUCTILE PARTICLE DEBONDING DURING CRACK BRIDGING IN CERAMICS

The increased fracture toughness due to a dispersed ductile phase in a brittle material is studied. For a ductile particle intercepted by a brittle matrix crack the large elastic-plastic deformations during crack bridging are analyzed numerically, and the work of deformation is determined. Debonding at the particle-matrix interface is represented in terms of a cohesive zone model that describes decohesion by normal separation as well as decohesion by tangential separation. The particle deformations are analyzed for various levels of strain hardening and for different interface strengths. It is found that, compared to perfectly bonded particles, the toughening effect of the particles is significantly increased if partial debonding takes place during bridging. Thus, a limited amount of debonding is advantageous, but the computations also show that too low bond strength gives complete debonding, which adds only a little toughness to that of the brittle matrix material.