Enhanced wettability and adhesion of carbon fibers with polyimide resin interfaces via grafted modified SiO₂ nanoparticles

Functionalized modified SiO2 was prepared by a mild and simple dip coating method, and a layer of functionalized modified SiO2 coating was introduced onto the carbon fiber surfaces not only to improve the surface wettability and activity of carbon fiber, but also strengthen the interphase of the carbon fiber/polyimide composite. The successful functionalization of SiO2 by bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) silane was confirmed. Moreover, a uniform coating with well-dispersed particles on a carbon fiber surface was achieved with a 1.0 wt% addition of TESPT-modified SiO2 (TESPT@SiO2) particles. Under this condition it was observed that the interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) augmentation was 26.37% and 38.27%, respectively, in comparison with carbon fiber composite coated only with polyimide resin. The functionalized modified SiO2 coating could effectively heal the surface defects of fiber, and the fiber tensile strength increased by more than 10.61%. This study provides a scalable, simple, and cost effective method of simultaneously increasing the interfacial strength of composites.