Comparison on failure behavior of three-dimensional woven carbon/carbon composites joints subjected to out-of-plane loading at room and high temperature

In the present work, an experimental investigation on the failure of 3D woven carbon/carbon all-composites mechanically fastened bolted joints with protruding-head and countersunk-head bolts has been implemented under out-of-plane loading in air at room temperature and up to 1100 degrees C for the first time. The load-displacement curves and main damage mechanisms for the required temperature points were determined and evaluated, respectively. It follows that, for room temperature, the global mechanical response was characterized by pseudoplastic, and the failure was dominated by the damage mechanisms including matrix cracking, interface debonding and threads fracture, especially, edge bending to breakage occurring for countersunk fastener. For 1100 degrees C, silicon carbide ceramic anti-oxidation coating was applied to prevent from oxidizing. Due to the relief of the thermal stresses, joints bearing capacity was enhanced by fiber/matrix interface performance improvement accompanying with a brittleness tendency of mechanical response, and the dominating failure mechanisms were carbon/carbon substrate oxidation caused by air entering through the cracks in SiC coating.