Development of a cohesive zone model for fatigue/fracture characterization of composite bonded joints under mode II loading

In this work a suitable cohesive zone model for high-cycle fatigue of bonded joints under mode II loading is developed. Stiffness degradation as a function of time is simulated by means of a damage parameter that accounts for static and fatigue damage. Finite element analyses of the end notched flexure test considering different coefficients of the modified Paris law and different load ratios were performed. A data reduction scheme based on the crack equivalent concept and Timoshenko Beam theory was adapted to fatigue analysis thus avoiding monitoring crack length during experiments, which is particularly cumbersome to execute in fatigue tests under mode II loading. The resulting numerical crack growth rates as a function of mode II strain energy release rate were compared with the input modified Paris laws. The verified good agreement shows the suitability of the model concerning fatigue/fracture characterization of adhesively bonded joints under high-cycle fatigue submitted to mode II loading.