Effect of sizing on the interfacial properties of carbon FIBER/BMI under different processing temperature

This paper aims to study impact of sizing on the interfacial properties of two T700 grade carbon fibers with bismaleimide (BMI), with the composites fabricated by different processing temperatures. Effect of sizing on the fiber surface properties, including fiber surface morphology and roughness, was analyzed. The sizing agent was extracted and it proved that the sizing content changed with the heat-treatment temperatures on the carbon fiber. The results suggest that sizing content decreases with increasing treatment temperatur e, especially after 170°C and 200°C treatment. Functional groups of the extracted sizing and the mixture of sizing and BMI resin were investigated by FTIR. It demonstrates that the sizing is chemically reactive at 200°C, and chemical reactions can take place between the fiber sizing and BMI at 170°C. In addition, different diffusion, cure, and post-cure processing temperatures were conducted on the carbon fiber/BMI composites. Interfacial shear strength (IFSS) of the two composites shows the lowest values for the temperature scheme (without post-cur e stage). However, no significant difference can be observed from the IFSS values of CF1/BMI and CF2/BMI composites, which were fabricated by with/without diffusion stage and different diffusion temperatures at 110°C or 140°C, respectively. Comparing the two composites, CF1/BMI always presents higher interfacial strength than CF2/BMI, which is consistent with the degree of reactions between its fiber sizing and BMI. This indicates that the interfacial chemical bonding plays a key role in the interfacial strength of the carbon fiber/BMI composites.