Process Optimization and Performance Investigation of Short Carbon Fiber Reinforced Nylon 6 Composites

ABSTRACT To address the weak interfacial adhesion in carbon fiber (CF)/polyamide 6 (PA6) composites, this study investigates the effects of sizing type, fiber length, fiber content, and sizing amount on composite structure and properties. Composites were prepared via melt blending and injection molding, and characterized using FTIR, XPS, DSC, SEM, and mechanical testing. Results show that an acrylic‐based sizing with C–N groups significantly improves interfacial adhesion, increasing tensile and notched impact strength by 43% and 66%, respectively, over unsized CF. With 5 mm fibers at 15 wt%, optimal crystallinity and mechanical performance were achieved: tensile strength of 104 MPa and impact strength of 34 J/m, representing increases of 89% and 215% over pure PA6. A 4.0% sizing amount provided uniform coating and superior wettability, yielding tensile and impact strengths of 112 MPa and 36.2 J/m, with respective improvements of 35% and 38% over unsized CF. This work demonstrates the role of interfacial regulation in enhancing composite performance and supports automotive lightweight applications.