The effect of thermo-oxidative aging on carbon fiber reinforced cyanate ester composites

In this work, the aging of two different carbon fiber reinforced cyanate ester polymer matrices (CFRP-A and CFRP-B) was investigated after their exposure to aggressive thermo-oxidative conditions. The materials’ degradation at 230℃ under 1 atm for 30 days in oxidative atmosphere was evaluated with regard to changes in mass (mass loss), glass transition temperature T_g, interlaminar shear strength, as well as physical characteristics that were examined under scanning electron microscopy. For both the systems, the aging study showed significant mass loss that reached ∼4% in the case of CFRP-B. The mass loss is accompanied with a considerable decrease in interlaminar shear strength and T_g properties. The study of the scanning electron microscopic images clearly shows the surface deterioration due to the oxidation process, accompanied with formation of matrix microcracking and development of matrix-fiber interfacial debonding. The contribution of the chains scission to the materials degradation was also detected by performing in situ aging through isothermal thermo-gravimetric analysis measurements at 230℃ under oxidative and inert atmosphere. However, the thermo-gravimetric analysis results showed minor chain scission proving thus, that the oxidation was the main degradation mechanism for both materials.