Mixed‐Mode Fracture Performance of Cracked Aluminum Plates Repaired With <scp>GFRP</scp> Composite Patches

ABSTRACT This study evaluates the effectiveness of adhesively bonded glass fiber‐reinforced polymer (GFRP) patches in repairing cracked aluminum specimens under Mode I (opening), Mode II (in‐plane shear), and mixed‐mode I/II loading conditions. Performance was assessed using critical load and absorbed energy measured from load–displacement responses. The focus is on the influence of fiber orientation—unidirectional (UD) 0°, UD 90°, and woven—on fracture behavior and load‐bearing capacity. Composite patches were bonded to aluminum plates using Araldite 2011 adhesive, and tests were performed using an Arcan fixture. Results show that fiber orientation plays a critical role in repair performance. Under Mode I loading, the GFRP‐UD‐0° patch achieved the highest critical load, while the woven patch demonstrated superior absorbed energy. In Mode II, the woven patch increased critical fracture load by approximately 350% compared to the unrepaired specimen. For mixed‐mode loading, the UD‐0° configuration provided the highest critical fracture load and absorbed energy. Overall, considering performance across all loading modes, the woven patch delivered the most balanced improvement in both load capacity and energy absorption. Finite element analysis confirmed that fiber orientation strongly influences stress intensity factors. Under Mode I loading, the UD‐0° patch exhibited the highest critical stress intensity factor, followed by the woven patch. In contrast, woven patches yielded the highest stress intensity factors under mixed‐mode and Mode II loading. Scanning electron microscope analysis revealed mixed adhesive–cohesive failure, with woven patches enhancing load transfer and energy dissipation. All patched specimens outperformed the unrepaired samples, confirming the effectiveness of patch repairs.