On the applicability of ASED criterion for predicting mixed mode I+II fracture toughness results of a rock material

A mixed mode fracture criterion based on the strain energy density averaged over a control volume has been successfully used earlier for evaluating the brittle fracture behavior of notched or cracked components made of engineering materials like metals, polymers and graphite. However, the applicability of the average strain energy density (ASED) criterion has never been investigated till now for rock materials. To fill this lack, a set of mixed mode I+II rock fracture toughness data provided experimentally by the authors are recalled and then predicted theoretically using the ASED criterion. The investigated fracture results have been obtained for a brittle white marble by testing an inclined edge crack triangular shape specimen subjected to symmetric three point bend loading. It is shown that very good ASED predictions are obtained for the fracture loads of the tested rock material in the entire range of mode mixities from pure mode I to pure mode II.