Mixed-mode numerical and experimental fatigue crack growth analyses of thick aluminium panels repaired with composite patches

In this paper, fatigue crack growth of repaired thick aluminium panels containing a central inclined crack is studied. The cracked panels were repaired on one side with glass/epoxy composite patches. Effects of patch lay-up configuration on starting the crack growth after bonding and crack growth rate of the repaired panels were investigated. The finite element analyses were performed assuming uniform crack growth along the panel’s thickness to simplify the analyses. The predicted fatigue lives using both mid-plane and un-patched surface fracture parameters of the repaired panels are compared with the experimental results. It is shown that the predicted crack propagation lives using the un-patched surface fracture parameters are too conservative for large crack growth values. However, the obtained lives using the mid-plane results may lead to non-conservative life prediction. It is also shown that the predicted starting crack growth life and the crack growth rate at the early crack propagation stages using the un-patched surface fracture parameters are close to the experimental results.