Significantly Enhanced Interlaminar Shear, Fracture Toughness, and Bending Behavior of Glass Fiber/Epoxy Laminates Containing Aligned Graphene Nanoflakes

ABSTRACT Achieving controlled through‐thickness alignment of graphene flakes within electrically insulating glass‐fiber‐reinforced polymer composites remains a significant challenge due to the limited effectiveness of externally applied electric fields in such structural materials. This study investigates the effect of AC electric‐field‐induced through‐thickness alignment of pristine graphene flakes on the mechanical performance of glass‐fiber/epoxy composites. Initially, the optimum graphene content (0.5 wt%) in a randomly dispersed state was identified based on maximum improvement in composite properties. Subsequently, graphene flake alignment was achieved by applying an AC electric field at 50 Hz with voltages of 500, 600, 700, 800, and 900 V in the through‐thickness direction. Among the aligned composites, the specimen processed at 800 V exhibited the most significant enhancement in mechanical performance, as obtained in form of improvements of approximately 30% in flexural strength, 63% in flexural modulus, 24% in interlaminar shear strength, and 33% and 53% in Mode‐I and ‐II fracture toughness, respectively over the neat glass/epoxy composite. Dynamic mechanical analysis revealed that graphene incorporation and alignment enhanced the room‐temperature mechanical response without affecting the glass transition temperature of the epoxy matrix. Scanning electron microscopy of the fracture surfaces indicated pronounced matrix and interfacial modifications such as prominent and well‐defined river‐line and hackle‐like features, providing insight into the graphene alignment–induced strengthening mechanisms. Overall, the proposed AC electric‐field‐assisted graphene alignment approach is simple, scalable, and effective for exploiting the reinforcing potential of graphene flakes in high‐performance structural composites.