Synergistic Construction of a Carbon Fiber/Epoxy Interface Layer by Polyaryletherketone/Polydopamine for Interfacial Enhancement

Carbon fiber reinforced epoxy resin composites (CFRP) are widely used in aerospace and advanced manufacturing fields due to their high specific strength, high modulus, and excellent fatigue resistance. However, the chemical inertness of the carbon fiber (CF) surface and the limited interfacial compatibility with the epoxy resin (EP) matrix restrict the effective load transfer within the composite. To enhance interfacial bonding, this study employed an aqueous polyaryletherketone (PAEK) sizing system combined with polydopamine (PDA) to synergistically modify carbon fiber and construct a stable interfacial structure. The surface chemical structure of the fibers was characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The interfacial morphology and mechanical properties were evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM) modulus mapping, and interlaminar shear strength (ILSS) measurements. The results show that PAEK/PDA forms a continuous interface layer on the fiber surface, achieving effective control of the CF/EP interface through the synergistic effects of π–π interactions, hydrogen bond networks, and covalent bonds. Atomic force microscopy (AFM) modulus mapping revealed that the interface layer thickness increased from approximately 84 nm to 286 nm, forming a significant modulus gradient that alleviated interfacial stress concentration. Consequently, the interlaminar shear strength (ILSS) of the composites increased from 47 MPa to 72 MPa (CF-PAEK/PDA6), indicating a significant improvement in load transfer efficiency. This study provides insights into the interfacial design of high-performance CFRP and the development of environmentally friendly sizing systems.