A generalised damage model for constant amplitude fatigue loading of adhesively bonded joints

The fatigue resistance of adhesively bonded joints is an important aspect of reliable structural design in many sectors. In this paper, the effect of load ratio on the fatigue behaviour of adhesively bonded joints was investigated using both experimental and numerical approaches. Single lap joints were tested under cyclic loading at different load ratios and load levels to characterise their response. A numerical model that accounts for the load ratio effect in constant amplitude fatigue loading was developed to predict the response of these bonded joints. The progressive damage of the adhesive material was modelled using a cohesive zone approach with a bi-linear traction-separation response. Damage initiation and propagation phases were monitored using the backface-strain and in-situ video-microscopy techniques. The load ratio effect on the fatigue behaviour of adhesively bonded joints was successfully predicted using a strain-based fatigue damage model. The numerical results were found to be in good agreement with the experimentally observed fatigue damage evolution and failure life.