On the paradox between crack bridging and crack interaction in quasi-brittle materials

Discontinuous cracks observed in quasi-brittle materials subjected to fracture mechanics testing may be idealised by two mechanical models, i.e. an interaction model between the main crack and collinear small cracks, and a crack-wake bridging model A study on these two models is presented in this paper and it shows that the instability of the crack system is significantly dependent on the model used. While the interaction model leads to unstable crack propagation, the crack bridging model predicts stable crack growth. It is concluded that the crack bridging model is more consistent with experimental observations on fracture in quasi-brittle materials.