Effect of temperature on reactions of carbon fiber sizing agent with bismaleimide and their composite interfacial adhesion

In order to study the effect of processing temperature on the regulating function of composite interface, three-stage curing processes of diffusion, cure and post cure are designed, and the interfacial adhesion variation is investigated of three carbon fibers/bismaleimide (BMI) composites under different processing temperatures. In-depth analysis of sizing agent on fiber surface roughness and chemical properties is carried out by AFM and FTIR, the chemical reactivity of sizing agent and the chemical reactions between sizing agent and BMI are studied, and the interfacial shear strengths (IFSSs) of carbon fiber/BMI are measured by micro-droplet. The results show that all the sizings partially react at 200 ℃, and chemical reactions take place between the sizing agent and BMI after 2 h treatment at 170 ℃. Comparing different temperature processes, the post-cure stage is found to have greater effect on the IFSSs of carbon fiber/BMI, and the temperature scheme without the post-cure stage shows the lowest values of IFSS. The diffusion stage of 110 ℃ and 140 ℃ has little effect on IFSSs. Under the same temperature, the reaction degree between CF1 and CF3 sizing agent with BMI is higher than that of CF2, and the corresponding IFSSs of CF1 and CF3 with BMI are higher than that of CF2, indicating that the chemical reaction degree between sizing agent and BMI is a main factor in controlling the interfacial adhesion. These research results may provide reference for the development of carbon fiber sizing.