Dynamic failure of quasi-brittle materials under dynamic loading has been a hot issue; the direction of crack propagation of pre-cracked specimens with mode II crack subjected to impact shear loading is closely related to its mechanical properties and impact velocity. The numerical simulations of dynamic shear crack propagation in specimens with two parallel edge pre-notches subjected to impact loading were carried out to investigate the propagation of mode II crack using rock failure process analysis-dynamic code. The effects of material properties

material heterogeneity

incident stress pulse amplitude and duration on the mode II crack propagation path were also investigated. The numerical results show that the mode II crack propagation under impact loading is induced by the shear damage as well as the tensile damage. Microcracks around main-crack are due to the material heterogeneity

which in turn influences the crack bifurcation and associated stress fields around cracks. Crack branching occurs and the specimen is further damaged when stress amplitude and duration are respectively beyond a certain value. The study result is of great help to investigate the law of mode II crack propagation and reveals the mechanism of damage and fracture of quasi-brittle materials under impact loading.