J integral as a fracture criterion of rubber-like materials using the intrinsic defect concept

► New fracture criterion for rubbers based upon the intrinsic defect concept. ► Generalized expression of the J integral under biaxial loading. ► Very nice agreement with experimental data on two kinds of rubbers. ► Promising extension to the failure analysis of thermoplastic polymers. Using the fracture mechanics framework, a fracture criterion based upon the intrinsic defect concept was developed to predict the failure of rubber parts under biaxial monotonic loading. This fracture criterion requires as input data the fracture toughness of the material in terms of critical value of the J integral, the constitutive law of the material and the breaking stretch of a smooth specimen under uniaxial tension. To develop this criterion a generalized expression of the J integral under biaxial loading is proposed on the basis of finite element calculations on a RVE containing a small circular defect. The estimated failure elongations were found in very nice agreement with experimental data on two kinds of rubber materials. Moreover, we have also shown that this criterion could be extended to the failure analysis of thermoplastic polymers.