Experimental investigation of thermal shock effects on carbon–carbon composites

In this paper, both compressive properties and oxidation behavior of pristine and thermal shock exposed 2D C/C composite specimens were examined. Pristine test specimens were exposed to thermal shock conditions with temperatures ranging from 400 °C to 1000 °C in an oxidizing environment, followed by compression tests on pristine and thermal shock exposed specimens to obtain their compressive responses. The experimental results showed that 2D C/C composite compressive stiffness and strength decreased with increasing thermal shock temperature. Also, upon exposure to thermal shock, the stress–strain response displayed a non-linear behavior prior to failure as compared to the pristine C/C composite that failed in a brittle manner. Furthermore, it was observed by microstructural analysis that at low temperatures, i.e., 400 °C, the oxidation attack was uniform through the interior of the composite. On the other hand, at moderate temperatures, i.e., 600 °C, oxidation occurred rigorously at the surface of the composite. At high temperatures, i.e., above 600 °C, the specimens experienced the two aforementioned oxidation mechanisms. Therefore, it was concluded that carbon matrix degraded rapidly when exposed to thermal shock conditions in oxidizing environments and protective coating is required to maintain the quality of the composite under such conditions.