A Novel Strategy for Introducing Metal-Organic Frameworks into Carbon Fiber to Improve the Interfacial and Mechanical Properties of Carbon Fiber/Epoxy Composites

The interfacial properties in carbon fiber (CF)-reinforced polymer composites are substantially limited by the chemically inactive and smooth CF surfaces. In this study, zeolitic imidazolate framework 90 (ZIF90) was chemically grafted onto CF surfaces via polyethyleneimine (PEI) as a coupling agent to construct a hierarchical reinforcement interface in CF/epoxy composite. The successful synthesis of CF grafted with PEI and ZIF90 (CF-PEI-ZIF90) was systematically characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The incorporation of ZIF90 nanocrystals and PEI molecules into CF surfaces effectively improved interfacial adhesion through mechanical interlocking and chemical interactions, thereby optimizing stress transfer efficiency at the fiber–matrix interface and improving the interfacial properties of the composite. Additionally, the resultant CF-PEI-ZIF90/epoxy composite demonstrated significant mechanical enhancement, with the tensile and bending strengths increasing by 33.5% and 21.4%, respectively, compared to unmodified CF/epoxy composites. This work provides a novel strategy for enhancing the interfacial performance of CF composites by leveraging the unique properties of metal-organic frameworks, which is critical for advancing high-performance structural materials in aerospace and automotive applications.