Siloxane Precursor-Based Protective Coatings for High Modulus Carbon Fibers in Ceramic Matrix Composites

Carbon fibers are outstanding reinforcements for ceramic components due to their excellent creep and long-term thermochemical and thermomechanical stability. Nevertheless, these properties are dramatically downgraded if the unprotected fibers are exposed to an oxidative or corrosive environment. Thin ceramic coatings can improve the corrosion resistance and tailor the fiber/matrix interface in order to achieve optimized stress transfer and damage tolerance. The continuous liquid phase coating (CLPC) technique with subsequent pyrolysis is a promising alternative to chemical vapor deposition (CVD) processes. The possibility to deposit homogenous thin flaw-free coating layers on every filament of high tenacity carbon fiber bundles has been successfully proven in previous studies. In this work, high modulus carbon fibers were coated with different polysiloxane-based resins, and the obtained rovings were implemented in SiOC matrices by the precursor impregnation and pyrolysis (PIP) route. Thermogravimetric analysis shows an increased oxidation resistance of the coated fibers compared with reference samples. Enhanced fiber/matrix interface strength further improved the mechanical performance of the fabricated composites.