Damage and strength analysis of bolted joints in CFRP

A method for prediction of the strength behaviour of mechanically fastened joints in FRP laminates on the basis of progressive damage analysis is considered. The method utilizes a three-dimensional contact stress analysis by means of commercial software ANSYS using specially adapted finite element meshes to account for the brittle material damage in the form of matrix cracking in the laminate plies. Stress criteria similar to those proposed by Puck as well as a set of physically plausible material degradation rules are used to model the effect of damage on the strength response of the laminate. The method has been implemented as an automated ANSYS-based simulation tool. First analyses performed using the model showed an improvement in strength prediction of about 8% in comparison to estimates made with no account for the damage. However, the experimental strengths are still not reached in the predictions and remain in average 20% higher. Corresponding enhancements of the numerical model to account for local delaminations and somewhat different intralaminar damage patterns are expected to further improve the accuracy of the method.