Abstract: The study focused on GFRP-Balsa sandwich structures, conducting three-point bending tests on a total of 9 specimens of three types of sandwich beams: non-toughened, Kevlar short fiber toughened, and Kevlar short fiber combined with graphene oxide hybrid toughened. By analyzing the interfacial delamination morphology, crack propagation patterns, and strain energy release rates of the GFRP-Balsa sandwich structures, the toughening mechanisms of different methods were elucidated. Experimental results demonstrated that, compared to non-toughened specimens, the hybrid toughened specimens exhibited a 25.96% increase in critical delamination load and a 92.4% enhancement in average strain energy release rate, indicating that the hybrid toughening method significantly improves the interfacial toughness of GFRP-Balsa sandwich structures. Scanning electron microscopy images and experimental data revealed that the toughening mechanism of Kevlar fibers involves the formation of composite fiber bridging structures, while graphene oxide modifies the resin, enabling it to tightly encapsulate the hybrid fibers, thereby increasing the difficulty of interfacial delamination.

Key words: GFRP- Balsa sandwich structure, toughening, Kevlar short fiber, graphene oxide, interfacial toughness