Dual‐Scale Synergistic Surface Modification of Carbon Fiber Fabric for Enhanced Interfacial Bonding and Mechanical Properties of <scp>PA6</scp> Composites

ABSTRACT Carbon fiber fabric (CFF)/polyamide 6 (PA6) composites suffer from poor interfacial bonding due to incomplete fiber wetting and void formation. This study presents a dual‐scale synergistic surface modification strategy combining mild alkaline etching with 3‐aminopropyltriethoxysilane (KH550) coating. Optimal etching parameters were established at 3 h with 5 wt% NaOH solution at 60°C. The synergistic mechanism operates at micrometer and nanometer scales: alkaline etching creates microscopic grooves and introduces oxygen‐containing functional groups, while KH550 coating forms strong covalent SiOC bonds and hydrogen bonding with the PA6 matrix. CFF/PA6 composites were prepared using resin transfer molding (RTM) with in situ polymerization. The optimized K‐CFF/PA6 composite exhibited superior mechanical properties: tensile strength of 688.1 MPa (29.6% higher than R‐CFF/PA6 composite), Young's modulus of 29.2 GPa (18.7% higher), flexural strength of 472.3 MPa (75.5% higher), and flexural modulus of 23.1 GPa (43.9% higher). Most notably, the composite achieved the lowest porosity (0.498%) among reported materials, with interfacial layer thickness increasing from 540 to 930 nm. Comprehensive characterization confirmed the dual‐scale synergistic mechanism. This strategy offers significant advantages over conventional oxidation methods by preserving fiber integrity while achieving superior mechanical performance, rendering it suitable for industrial‐scale applications in aerospace and automotive sectors.