Construction and Performance of an Interfacial Layer in Carbon Fiber/Polyamide Composites via Electrostatic Self-Assembly

The interfacial properties of carbon fiber (CF)-reinforced composites are crucial for advancing the application of high-strength composite materials. In this study, a micro–nano hierarchical rough structure was constructed on the carbon fiber surface through electrostatic self-assembly of PEI–KH560 and nanosilica (SiO 2 ) to enhance the interfacial bonding between the carbon fiber and polyamide 6 (PA6) matrix. The results indicate that PEI–KH560 and SiO 2 were uniformly coated on the CF surface, significantly improving the interfacial interaction through mechanical interlocking and chemical bonding. The influence of the carbon fiber content on composite properties was investigated via melt blending. When the CF content reached 15 wt %, the flexural strength and modulus of the composite reached 447.43 MPa and 9.10 GPa, representing increases of 336.96 and 225%, respectively, compared to pure PA6. The interlaminar shear strength (ILSS) reached 66.19 MPa, an improvement of 86.13%. The rheological and crystallization behaviors of the CF/PA6 composites were also systematically analyzed. This study explores the fundamental interfacial phenomena in carbon fiber composites, utilizing electrostatic self-assembly as a model platform to investigate the synergy between surface topography and chemical interactions, and provides a strategy for designing high-performance CF-reinforced thermoplastic composites.