A Progressive Damage Model for the Prediction of Fatigue Crack Growth in Bonded Joints

A procedure to predict fatigue crack growth in bonded joints is developed in this work within the framework of cohesive zone modelling and finite element analysis. The idea is to link the fatigue damage rate in the cohesive elements to the macroscopic crack growth rate through a damage homogenisation criterion. In this way, the experimental crack growth rate is related directly to damage evolution in the cohesive zone, that is, no additional parameters have to be tuned beside the quasi-static cohesive zone parameters. The procedure was implemented in the ABAQUS finite element software using the USDFLD subroutine. In order to evaluate the crack growth rate automatically, the strain energy release rate (crack driving force) was calculated and updated automatically within the subroutine. Mode I and Mode II loading cases have been dealt with and the implementation for Mixed Mode I/II is under way.