Study on crack curving and branching mechanism in quasi-brittle materials under dynamic biaxial loading

Attempts are made to analyze the temporal and spatial effect and the complex mechanical behaviors of microcracks and the macro crack at mesoscopic scale based on the damage evolution principle. The mechanism of crack curving and branching in quasi-brittle materials under dynamic biaxial loading is investigated. The effects of different ratios between the load in the horizontal and vertical directions (for convenience, the loading ratio is denoted by B in this paper), crack dip angles and material homogeneity on crack curving and branching are considered. The results indicate that: Crack curving is mainly controlled by the loading ratio, while initiation and propagation of branch microcracks are related to the stress level. The initial dip angle of crack can vary the stress configuration at the crack tip zone. If the loading ratio remains constant, the crack tends to propagate toward the vertical direction with increasing crack dip angle. It is also found that heterogeneity due to defects in the material play an important role in the distribution of tiny voids and cracks in the material and the crack propagation mode. The results in this study are not only in good agreement with the physical test results, but also can provide some valuable reference for studies on the tensile properties and failure modes of heterogeneous quasi-brittle materials with internal defects.