Multiscale Interphase Engineering of Carbon Fiber/Epoxy Composites via Hyperbranched Epoxy Grafting

Abstract

A combined experimental and molecular simulation study was conducted to investigate the effect of hyperbranched epoxy (HPE) grafting on the interfacial and mechanical properties of carbon fiber/epoxy (CF/EP) composites. HPE was chemically grafted onto carbon fiber surfaces to construct an engineered interphase with enhanced physicochemical compatibility toward the epoxy matrix. Surface characterization revealed significantly increased roughness and wettability after HPE grafting. Compared with untreated CF/EP composites, the HPE‐functionalized composites exhibited improvements of 117.2%, 34.2%, and 13.5% in interfacial shear strength, interlaminar shear strength, and flexural strength, respectively, together with enhanced thermal stability. Fracture morphology analysis demonstrated substantially improved fiber/matrix adhesion and suppressed interfacial debonding. Molecular dynamics simulations further revealed increased interfacial interaction energy and reduced mean square displacement and free volume fraction, indicating restricted molecular‐chain mobility and the formation of a more compact interfacial structure. Overall, this work provides multiscale insights into the interfacial reinforcement mechanisms induced by HPE grafting and demonstrates the potential of interphase engineering for the development of high‐performance CF/EP composites.