Experimental and Numerical Analyses of the Effects of Overload on the Fatigue Life of Aluminum Alloy Panels Repaired with Bonded Composite Patch

In this study, we analyzed the effect of a single overload fatigue cycle on the efficiency of bonded composite patch repair on a cracked Al 2024 T3 aluminum plate. Experimental and numerical analyses were performed to achieve the objective of the study. In the experimental part of the study, fatigue tests were conducted on a V-notched aluminum plate subjected to a constant amplitude fatigue loading with an overload applied at a relative crack length of 0.06 (a/W = 0.06). The plate was repaired with a carbon/epoxy composite patch. A fatigue life curve (a = f(N)) was plotted for the patched and unpatched specimens using the results of the experimental tests, and scanning electron microscopy images of the fracture surfaces of the failed specimens were observed. In the numerical part, the elastic–plastic finite element method was used to evaluate the plasticity induced by the overload on the patched plate and to analyze the adhesive damage after this overload was applied. The obtained results demonstrate that the patch deposition of the overload can lead to an extended fatigue life, and the adhesive damage after the overload is quite significant, but the risk of total failure of the adhesive layer is not high.