Crack growth and debonding analysis of an aluminum pipe repaired by composite patch under fatigue loading

In this study, the behavior of a cracked aluminum pipe, repaired by glass/epoxy composite patch, is investigated under fatigue tension loading through the experimental test and numerical modeling. While most previous investigations on crack growth problems assume that the composite patch is tied to the cracked panel, in this study debonding of the adhesive layer between the pipe and the composite patch is modeled besides crack growth in the aluminum pipe. The crack growth is modeled through XFEM framework while cohesive elements are implemented to consider debonding in the adhesive layer. It is shown that such a numerical model can present more realistic behavior of the structure in comparison to similar experimental tests. Three different shapes of composite patches are then considered to investigate the debonding procedure during fatigue loading of the cracked pipe. A parametric study is also presented for such a cracked repaired pipe to observe the effect of fiber orientation on fatigue crack growth. Finally the debonding is studied in a repaired pipe with an inclined crack. These parametric studies would lead to reaching optimized designs of patch repaired pipes under fatigue loading.