Nominal strength of quasi-brittle open hole specimens under biaxial loading conditions

One of the main purposes for an accurate strength prediction is to get a reliable design tool of a given structure. Since most of aircraft and aerospace structures contain many holes and are subject to multidirectional loading conditions, due to stress concentration, cracks will necessarily emanate from these holes before failure. Therefore, the nominal strength prediction of open hole specimens under biaxial loading conditions is very necessary for the safe design of these structures. The main goal of this work is to develop an analytical model able to predict the nominal strength and the failure envelope of isotropic quasi-brittle open hole specimens under biaxial loading conditions. In this model, the nominal strength is analyzed taking into account the hole radius and the biaxiality load ratio. The model is formulated based on the cohesive zone model considering various shapes of the cohesive law. Other approaches such as the different methods of the critical distance theories are also presented and compared with the results of the cohesive crack model.