A thermo–mechanical cyclic cohesive zone model for variable amplitude loading and mixed–mode behavior

Abstract

A cyclic cohesive zone model is developed which is capable of predicting fatigue driven delamination under thermo–mechanical loading conditions. The model is an extension of an exponential traction–separation law describing the quasi–static constitutive behavior of the interface. Mixed–mode loading conditions are accounted for using an interaction criterion based on the Benzeggagh and Kenane expression. Damage degradation under thermo–mechanical fatigue loading is accounted for by using a cycle–by–cycle analysis. A Paris’ law type formulation is utilized to model fatigue damage which is based on physically interpretable interface properties, overcoming the need of any parameter fitting. Varying load amplitudes are captured by the model formulation. For constant amplitude loading a cycle jump technique is implemented to decrease the computational time. The cohesive zone parameters are assumed to be temperature dependent and the model formulation accounts for interface weakening at elevated temperatures. In addition, the effect of interface degradation onto the heat transfer across the damaged interface is modeled by linking the mechanical damage variable to the thermal conductance of the interface. The model is implemented within the framework of the nonlinear Finite Element Method and includes non–local evaluation of the cohesive zone length and the mode ratio. Finally, the proposed model is demonstrated on mode I, mode II, and mixed–mode delamination tests.