Microstructural evidence for the thermal oxidation protection of carbon/phenolic towpregs and composites Original Research Article

This study provides microstructural information on changes in the carbon fiber surface as a function of heat-treatment temperature up to 900 °C in air, for carbon/phenolic towpregs and composites, respectively, as made from carbon fiber tow and carbon fabric pre-coated with a 0.5 vol.% phosphoric acid solution in methanol. Thermogravimetric analysis and scanning electron microscopy were used. The results show that within the temperature range used in this study, the surface of the carbon fiber in the towpreg and the composite is protected from pitting and damage due to thermal oxidation by the coating, and showed a smaller reduction in fiber diameter, compared to the uncoated material.