Crack branching mechanism of rock-like quasi-brittle materials under dynamic stress

The cracking patterns of a thin sheet with a pre-existing crack subjected to dynamic loading are numerically simulated to investigate the mechanism of crack branching by using the FEM method. Six numerical models were set up to study the effects of load, tensile strength and heterogeneity on crack branching. The crack propagation is affected by the applied loads, tensile strength and heterogeneity. Before crack branching, the crack propagates by some distance along the direction of the pre-existing crack. For the materials with low heterogeneity, the higher the applied stress level is and the lower the tensile strength of the material is, the shorter the propagation distance is. Moreover, the branching angle becomes larger and the number of branching cracks increases. In the case of the materials with high heterogeneity, a lot of disordered voids and microcracks randomly occur along the main crack, so the former law is not obvious. The numerical results not only are in good agreement with the experimental observations in laboratory, but also can be extended to heterogeneity media. The work can provide a good approach to model the cracking and fracturing of heterogeneous quasi-brittle materials, such as rock, under dynamic loading.