Fiber-reinforced polymer composite interfaces: research progress on mechanisms, modification, and multifunctionalization

The performance of fiber-reinforced polymer composites is highly contingent upon the properties of the interfacial region between the fiber and the matrix. The interface acts not only as a critical medium for load transfer but also fundamentally governs the damage evolution mechanisms and the resultant macroscopic performance of the material. With increasing applications of composites in aerospace and advanced equipment, interfacial research has progressed from simply pursuing strong bonding to the deliberate design of interfacial structure and functionality. This paper reviews recent advances in composite interface science. First, the physicochemical mechanisms of interfacial bonding and typical failure modes are analyzed to establish the relationship between interface behavior and macroscopic performance. Second, various interfacial modification strategies, including chemical treatment, physical methods, and coating techniques, are compared in terms of their working mechanisms and limitations. Third, the use of nanoparticles and nanofilms to enhance interlaminar performance is discussed, along with their toughening mechanisms. Finally, the emerging trend of developing the interface from a mechanical link into a multifunctional platform is considered, and current challenges such as scalable fabrication and long-term reliability are summarized. This review aims to provide useful insights for both fundamental research and practical applications of composite interfaces.