Crack-face grain interlocking/bridging of a polycrystalline graphite: The role in mixed mode fracture Original Research Article

The KI/KII-mixed mode fracture of a polycrystalline graphite is examined. The importance of crack-face interaction via crack-face grain interlocking/bridging is emphasized in the mixed mode fracture. The crack-face interaction by no means results in pure mode II fracture, for the interaction inevitably induces a crack-face opening mode (KI-mode) even under in-plane shear deformation. The maximum hoop stress criterion successfully predicts the initial angle of crack extension for the notched specimens, as well as the precracked specimens combined with a micromechanical model for the KII-induced KI deformation.