Composite patch geometry effect on the strength of reinforced damaged plates: a numerical study

In aerospace and naval applications, the optimization of the geometry of repair patches is a key factor in improving load transfer efficiency in damaged areas, thereby restoring structural integrity. The shape of the patch plays a significant role in influencing stress distribution through the adhesive layer, potentially reducing stress concentrations at the patch edges. This study introduces a geometry-driven redesign of bonded composite repair patches, proposing two novel in-plane architectures that enhance structural efficiency without increasing patch area or material thickness. The proposed geometries are evaluated on a 2024-T3 aluminum plate with a central circular notch under tensile loading, using bonded carbon/epoxy composite patches. A systematic numerical investigation of mechanical behavior up to failure is conducted and validated against available experimental results. The tensile response is simulated using the extended finite element method (XFEM) coupled with cohesive zone modeling (CZM) and the results show strong agreement between numerical predictions and experimental data. The obtained results demonstrate that geometric tailoring alone enables improved stress redistribution, reduced adhesive debonding, and measurable material savings compared to a conventional square patch. Therefore, the paper can provide practical design guidance for high-performance adhesive repairs in critical structural applications.