Co-authors​ :

 Faustino MUJIKA (SPAIN), Ainhoa ARRESE (SPAIN) 

The double cantilever beam (DCB) test was designed to characterize interlaminar fracture in pure mode I and the end notched flexure test (ENF) was designed to analyse interlaminar fracture in pure mode II. Nevertheless, in the case of geometric, material or combined asymmetry of the cracked arms of the specimen, combination of modes appear in both test configurations. In the present study, an analytical model is presented to decompose the energy release rate in mode I and mode II contributions. The model is based on the assumption of point loads at the crack tip zone. The J integral is applied to cases of small fracture process zone, where linear elastic fracture mechanics prevails. In those cases, the J integral is the same as the energy release rate G. The calculation process is based on the complementary strain energy or coenergy of the specimen in both test configurations. The results obtained from the analytic approach, are compared with those obtained by the FEM with the virtual crack closure technique.