Carbon fiber-reinforced polyamide composites with efficient stress transfer via plasma-assisted mechanochemistry

Carbon fiber-reinforced polymers (CFRPs) show excellent mechanical strength and lightweight. However, conventional CFRPs require high loading of carbon fibers (CFs) to improve their mechanical properties due to poor polymer–CF interfacial adhesion. We propose a dry and ecofriendly method to fabricate high-performance CFRPs by improving interfacial adhesion. The plasma-assisted mechanochemistry (PMC) process can create physical and chemical linkages between polymers and carbon fillers via application of a mechanical force and plasma treatment. We use carbon nanotubes as bridge materials to increase the effective interfacial area and promote mechanical interlocking. The PMC-treated CFRPs exhibit reduced C-factor and increased degree of entanglement, indicating efficient stress transfer the polymer to the filler. Additionally, the PMC process can provide the significantly improved mechanical properties of CFRPs even at low CF loading. Notably, the PMC-treated CFRPs showed continuously increasing tensile strength, Young's modulus, and elongation at break with increasing CF content up to 30 wt%, which has not been observed previously for CFRPs. As a result, the tensile strength, Young's modulus, and elongation at break of the PMC-treated composites with a CF content of 30 wt% increased by 47.1%, 43.0%, and 91.7%, respectively, compared to those of the conventional composites. We believe that this simple approach opens a new route to the fabrication of high-performance CFRPs exhibiting extraordinary mechanical properties.