Effect of electrochemical anodic oxidation modification on the interfacial properties of carbon fiber reinforced polyimide composites

Abstract This research involved the modification of carbon fiber (CF) through electrochemical anodizing under different conditions and focused on analyzing the impact of modifying CF surface and examining the interfacial characteristics of thermoset polyimide (PI) composites. The process of electrochemically oxidizing CF consists of two distinct stages. The oxidation stage mainly occurs under the conditions of low current intensity and low electrolyte concentration, at the graphite boundary defects on CF surface. The etching effect stage intensifies on CF surface under high current intensity and electrolyte concentration, resulting in the fracture and detachment of the carbon rings. Electrochemical oxidation improves CF roughness and the quantity of active functional groups, which enhances mechanical interlocking and chemical bonding between CF and PI. Furthermore, the introduction of reactive hydrogen groups can contribute to the PI curing process, significantly improving the weak interface bonding problem between CF and PI. The interfacial shear strength (IFSS) of the composites increased from 82.08 to 104.33 MPa and 114.08 MPa in acidic and alkaline electrolyte environments, respectively. Highlights Improved interfacial compatibility between CF and polyimide resin through electrochemical oxidation The relationship between the physical morphology and chemical composition of the surface of CF and their interfacial properties was investigated. The interfacial shear strength of CF/PI was increased by 38.99% without any loss in mechanical properties of the CF. The electrochemical oxidation mechanism of CF under different electrolytes was revealed.