Graphene Nanosheets Enhanced Hygrothermal Aging Resistance of Epoxy Composites: A Combined Experimental and Molecular Dynamics Simulation Study

This study explores the hygrothermal aging resistance of graphene nanosheet (GN)-reinforced epoxy composites via a combined experimental and molecular dynamics (MD) simulation approach. Epoxy systems with 0–1.0 wt% GN are fabricated and aged at 80 °C for 516 h. Optimal performance is achieved at 0.75 wt% GN, exhibiting improved tensile strength, impact toughness, hardness, and glass transition temperature. GN addition reduces moisture uptake and diffusion by physically obstructing water pathways and restricting chain mobility. Scanning electron microscopy analysis shows suppressed crack formation, while MD simulations reveal that GN enhanced interfacial bonding, decreases fractional free volume, reduces mean square displacement, and limits water-induced hydrogen bonding. Notably, GN increases interfacial interaction energy by up to 96.4% relative to water–epoxy bonding. These results demonstrate a multiscale reinforcement mechanism and offer a rational strategy for designing durable epoxy composites for aerospace and electronic packaging applications.