Through-thickness compressive properties and oxidation behavior of 2D C/C composites were determined in this study. Microstructural analyses of thermal shock exposed test specimens displayed that at low thermal shock temperatures, oxidation attack was observed by crack/void growth and two/matrix interface degradation within the entire thickness of the composite. Whereas, at moderate thermal shock temperatures, high concentration of oxidation was observed at the surface of the composite. However, test specimens exposed to high thermal shock temperatures experienced both types of oxidation, i.e., surface degradation and oxidation within the exposed surfaces. Other effects of oxidation due to thermal shock on C/C composite were the rapid carbon matrix degradation, “needle-shape” morphology at the exposed ends of the fibers and fiber breakage at the surface of the oxidized test specimens.
Furthermore, through-thickness compressive stiffness and strength decreased with increasing thermal shock peak temperature for test specimens exposed to one and three cycles. It can be concluded that the compressive stiffness of test specimens degraded approximately up to 55% for the most severe condition of three cycles of thermal shock with peak temperature of 1000C. Similarly, the compressive strength degraded about up to 17% for three cycles for thermal shock with peak temperature of 800C. Also, based on the stress-strain responses, it was concluded that non-linearity due to damage was induced to the material with increasing the number of cycles of the thermal shock conditions. Optical observations of the test specimens after one and three cycle thermal shock conditions showed that oxidation effects were significantly greater with increasing number of cycles of any thermal shock process, and even though both thermal configurations displayed similar oxidation behavior, lower values in the compressive properties of test specimens exposed to three thermal cycles were obtained.
Finally, it was suggested that tow/matrix debonding and interlayer shear failure were the main failure mechanisms of the 2D C/C composite specimens during compression tests, since high stress concentrations existed between the plies. Thus, it was concluded that 2D C/C composite properties were strongly affected by oxidation attack on carbon materials during thermal shock expose in an oxidizing environment. This investigation is of great importance to decide the usability of C/C composites for high temperature structural applications.