Reactive Poly(Acrylonitrile‐ co ‐Glycidyl Methacrylate)/Azide‐Functionalized Graphene Composite Sizing Toward Multifunctional Interfacial Engineering of Carbon Fiber/Epoxy Composites

ABSTRACT Carbon fiber (CF)‐reinforced epoxy composites are widely used in lightweight structural applications, but their performance is often limited by insufficient interfacial adhesion between the chemically inert CF surface and the epoxy matrix. In this study, a reactive multifunctional sizing system based on poly(acrylonitrile‐ co ‐glycidyl methacrylate) (PAG) and azide‐functionalized reduced graphene oxide (RGO‐N 3 ) was developed to improve interfacial adhesion while retaining electrical functionality in the corresponding composite sizing films. PAG was synthesized by free‐radical copolymerization of acrylonitrile and glycidyl methacrylate, and RGO was functionalized with azide groups to improve its compatibility with the polymeric sizing matrix. Structural analyses confirmed the preservation of reactive glycidyl groups in PAG and the successful introduction of nitrogen‐containing functionalities onto RGO. SEM observation indicated a relatively uniform distribution of RGO‐N 3 within the PAG sizing agent, with favorable coating morphology at intermediate filler contents. Microdroplet pull‐out testing showed that the interfacial shear strength increased from 7.6 ± 1.2 MPa for desized CFs to 18.7 ± 2.0 MPa for the composite containing 0.7 wt% RGO‐N 3 , corresponding to an approximately 146% improvement. Post‐fracture SEM observations revealed increased epoxy retention on the fiber surface, indicating a transition from adhesive interfacial debonding to cohesive failure within the epoxy matrix. The enhanced interfacial performance is associated with the combined effects of possible PAG‐epoxy chemical interactions during curing, nitrogen‐containing surface functionalities, favorable graphene distribution, and improved stress transfer. This study demonstrates that integrating reactive polymer chemistry with functionalized graphene provides an effective strategy for engineering electrically functional and mechanically robust CF/epoxy interphases.