Asymmetric stacking patch for debonding suppression in single-sided patch repair of composite structures

With the increasing use of composite structures, a simple and effective repair method is needed to enhance operational efficiency. While conventional single-sided patch repairs are straightforward, they are prone to debonding due to secondary bending deformation, leading to low post-repair strength. This study proposes a single-sided patch with an asymmetric lay-up designed to suppress debonding by utilizing coupled tensilebending deformation. The stacking sequence of the patches was optimized using a genetic algorithm to minimize the adhesive's expansion strain energy density. The optimal stacking sequence generates bending deformation with curvature opposite to the secondary bending observed under tensile loading in a patch-repaired plate. This discrepancy in bending deformation alleviates the hydrostatic stress in the adhesive at the patch edges and reduces the contribution of Mode I to patch debonding. Tensile tests using optimized patches demonstrated the debonding suppression mechanism, showing that the onset strain for debonding improved due to material failure occurring in the base CFRP laminate.