Influence of the interface ply orientation on the fatigue behaviour of bonded joints in composite materials

The paper deals with the study of the fatigue behaviour of bonded joints in composite materials. The influence of the orientation of the composite layer at the adhesive–adherend interface is investigated on single lap joints prepared by carbon fabric/epoxy laminates bonded together with a two-part epoxy adhesive. Different laminate lay-ups ([45/02]s and [452/0]s), overlap lengths (20 and 40 mm) and corner geometry of bonded area (square edge and fillet, respectively) were investigated under tension–tension fatigue. Particular attention was devoted to the analysis of the fatigue damage evolution to identify initiation and subsequent growth of cracks. A previous model developed by the authors, for the prediction of the fatigue life of bonded joints as the sum of an initiation and propagation phase, was successfully applied to summarise the new data.