Progressive damage and failure of mechanically fastened joints in CFRP laminates – Part I: Refined Finite Element modelling of single-fastener joints

This paper presents a refined Finite Element modelling for strength prediction, and especially bearing strength prediction, of mechanically fastened joints in CFRP laminates. Although the importance of delamination on the bearing strength of the joint is well established in the literature, only rarely has it been introduced into the models. In the present work, delamination onset and propagation are explicitly taken into account in the model by means of cohesive elements. The ply behaviour is described through a viscoelastic model combined with a progressive damage approach. A multi-model calculation strategy is developed to reduce the calculation costs. Prediction of the proposed model are compared to both bearing tests and open-hole tests results. For further validation, numerical predictions are also compared to filled-hole tensile tests and bearing/bypass interaction tests. Bearing, open-hole, and filled-hole tests are performed in this study. An original pin-bearing test configuration is proposed. Predicted strengths and experimental results turn out to be in good agreement. The obtained results are promising and demonstrate the capability of the proposed model to capture the material and stacking sequence effects on the joint behaviour and strength, as well as the influence of the geometrical dimensions of the joint.