Improving the Interfacial Adhesion of Carbon Fiber/Polyether Ether Ketone Composites by Polyimide Coating

Polyimide (PI) as a sizing agent for short carbon fiber (SCF) was explored, and a series of SCF-reinforced polyether ether ketone (PEEK) composites with PI sizing concentrations varying from 0 to 2.0 wt % were fabricated using the extrusion and injection molding techniques. It was found that the PI sizing layer forms homogeneously and compact on the SCF surfaces, and when the PI sizing concentrations was 1.0 wt %, the tensile strength and flexural strength of the corresponding SCF/PEEK composite was significantly increased by 16.8 % and 8.2 % respectively in comparison with the untrelated case. Additionally, dynamic mechanical analysis (DMA) curves demonstrated that storage modulus of SCF/PEEK composites were enhanced with the increasing concentration of PI sizing, resulting the higher stiffness and the lower damping behavior of the composites. Further, the single fiber pull-out testing was also measured, with the increased interfacial shear strength (IFSS) of CF/PEEK composites by 24.8 % from 70.6 to 88.1 MPa for the CF modified with 1.0 wt % PI sizing, which illustrated that PI sizing can improve fiber surface wettability and interfacial adhesion between CF and PEEK.