Influence of Patch Sizes and Graphene Nanoparticles on the Flexural Behavior of Repaired GFRP Composites

ABSTRACT Composite materials are prone to damage during their operational life under static and fatigue loading. Repairing damaged components with bonded external patches offers a sustainable alternative to disposal. This study investigates the influence of patch size and graphene nanoparticle addition at the patch‐parent interface under flexural loading. Four patch configurations were tested: 8‐layer 15 mm square, 8‐layer 15 30 mm, 16‐layer 15 mm square, and 16‐layer 15 30 mm. Static flexural tests on pristine, drilled, and patched specimens showed improvement in strength due to patch addition. These results were validated using Abaqus simulations with 2D Hashin damage criteria. For GNP reinforcement, the 8‐layer 15 mm square patch was modified with 0.3, 0.5, 0.7, and 0.9 wt% GNP at the interface. GNP addition–enhanced static strength, with a 67% maximum improvement at 0.3 wt%. Fatigue tests (75% of drilled static load) revealed a significant life reduction in drilled specimens (958 cycles) compared with pristine (62,103 cycles). Patch repair improved fatigue life, with 8‐layer and 16‐layer 15 30 mm patches surviving beyond 100,000 cycles. The 16‐layer 15 mm square patch failed between 79,000 and 97,000 cycles, and the 8‐layer 15 mm square patch between 16,000 and 21,000 cycles. Incorporating 0.3, 0.5, 0.7, and 0.9 wt% GNP in the 8‐layer 15 mm square patch improved fatigue life by 362%, 303%, 205%, and 43%, respectively, with 0.3 wt% showing the highest enhancement. Higher GNP content led to decreased fatigue performance. Displacement contours from DIC aided in analyzing the effects of patch dimensions and GNP content.