The influence of thermal shock on inter-laminar shearing strength of woven C/C composites

Abstract

Although the mechanical properties of carbon fiber reinforced carbon (C/C) composites under high temperature environments have been widely studied to date, the influence of thermal shocks on C/C composites have scarcely been investigated due to the lack of high-speed heating equipment. Our equipment based on a high frequency induction heating method provided a solution to this problem. In the present study, we examined the influence of thermal shocks on the inter-laminar shearing strength (ILSS), which is one of the most important subjects of designing a plain woven C/C composite with a three point bending test. By the change of the span-to-height ratio (l/h), the failure mode shift of the inter-laminar shearing to the bending was observed. By a series of tests, we proposed an appropriate l/h ratio to obtain a reliable inter-laminar shearing strength of C/C composites, which would be higher than that for the conventional CFRPs. The observation of the failure specimens was done by scanning electron microscopy (SEM) and optical microscopy. Not only debondings at 0°/90° interface but also propagation of transverse cracks were observed in the thermal shocked specimens. The 0°/90° interfacial debondings were suggested as the main source of the inter-laminar shearing strength deterioration.