Strength–Toughness Synergistic Epoxy Nanocomposites Coupling a Layered Graphene Framework and Nanomodified Interfaces

Epoxy nanocomposites are essential in various industrial applications for their superior mechanical strength. However, improving toughness while maintaining strength is challenging due to nanofiller agglomeration and poor interfacial interaction. Inspired by nature's hierarchical damage-tolerant structures, a novel multiscale hierarchical reinforcement strategy was proposed to achieve the synergistic improvement of strength and toughness in epoxy nanocomposites. The layered graphene scaffold with interlayer bridges prevents inherent restacking, promoting crack deflection at the graphene-epoxy interface through macro- and microscale features. Graphene surfaces were modified with silicon dioxide nanoparticles (SiO₂ NPs) and carbon nanotubes (CNTs) to enhance the interfacial interaction. Nanoscale SiO₂ NPs alleviate local high stress through frictional sliding, while microscale CNTs enhance the interfacial strength. At 0.625 wt % graphene, RGO-SiO₂-CNTs/EP nanocomposites show 14.85% higher strength, 155% improved fracture toughness (<i>K</i>_IC), and 51.9% enhanced steady-state fracture toughness (<i>K</i>_JC). This synergistic reinforcement strategy provides a new paradigm for the design of high-performance epoxy nanocomposites.