Enhancing Interfacial Toughness of <scp>CFRP</scp> /Honeycomb Sandwich Structures via Basalt Fiber and Graphene Oxide Hybrid Modification

ABSTRACT Interfacial toughening of sandwich structures was achieved by incorporating basalt fibers (BF). The optimal fiber content was first determined by evaluating five different compositions. Under three‐point bending, the specimen containing 2 wt% BF demonstrated the most notable improvement, with peak load and absorbed energy increasing by 27.4% and 102.5%, respectively. To further enhance performance, three toughened interfaces were engineered using this optimal fiber content. Among these, the BF‐GO hybrid treatment yielded superior results, achieving remarkable increases of 38.4% in peak load and 149% in energy absorption. This improvement is attributed to the synergistic effects of the APTES and GO treatments, which enhance the fiber's interfacial properties by improving wettability, increasing surface roughness, and introducing additional functional groups. These modifications promote mechanical interlocking and strengthen the fiber–resin interface. Consequently, this toughening strategy altered the structural failure mode, effectively suppressing interfacial debonding. Basalt fiber thus presents a cost‐effective approach for interfacial toughening in CFRP/honeycomb sandwich structures, mitigating debonding issues and enhancing overall performance.