Optimization of composite patch designs for enhanced repair efficiency in damaged aircraft structures

The effectiveness of bonded composite patch repairs in extending the service life of damaged aircraft structures is largely influenced by the mechanical behavior of the adhesive layer, particularly shear stresses. Adhesive or cohesive failure due to debonding remains a major concern, yet the degradation mechanisms are not fully understood. This study employs finite element simulations to analyze the impact of patch geometry, specifically thickness distribution, on repair efficiency. Three patch configurations with varying thickness distributions were developed, demonstrating that repairs using inhomogeneous-thickness patches significantly outperform conventional uniform-thickness patches. Compared to a standard rectangular patch of constant thickness, the optimized patches led to lower stress intensity factors (SIF) and a substantial reduction in shear stresses within the adhesive layer. Notably, a stair-shaped patch and a digressive stair patch provided the best performance, effectively distributing stresses while minimizing peak concentrations. These findings highlight the potential for advanced patch geometries to enhance repair durability and reliability in aerospace applications.