Real-Time Observation of Damage Nucleation in 3D Braided Carbon/Carbon Composites

Abstract

The micro mechanisms of flexure damage at the notch tip in a three-dimensionally braided carbon/carbon composite (3D–C/C) were investigated in real-time through a Scanning Electron Microscopy. It was found that the damage was nucleated in the fibre bundle/matrix interface around the notch tip. The different damage modes were found in different directions of the 3D–C/C. The x-directional flexural specimens seem to be insensitive to the pre-notch while the z-directional flexural specimens seem to be sensitive to the pre-notch. Fibre yarns acted as an obstacle to crack propagation and it was necessary to increase the load to propagate the crack through the adjacent fibre yarn. Comparing with the x-directional flexural specimens, the forces could be better transmitted in z-directional flexural specimens because the fibres of z-direction bundles can tightly adjoin to each other.

Thermal shock resistance analysis of a semi-infinite ceramic foam

“…A number of interesting observations were made during the research works aiming at investigating the thermal shock resistance. The thermal shock resistance analysis of ceramic media was mainly focused on the measuring and calculating of Young's modulus and retained strength after thermal shock (Dimitrijevic, Posarac, Majstorovic, Volkov-Husovic, & Matovic, 2009;Ding, Zeng, & Jiang, 2006;Kan, Wei, Meng, & Xu, 2009;Orenstein & Green, 1992;Rendtorff, Garrido, & Aglietti, 2011;Vedula, Green, & Hellman, 1998;You et al, 2005), the length of crack growth (Panda, Kannan, Dubois, Olagnon, & Fantozzi, 2002;Yuan, 2008), and thermal stress resistance parameter (R 0 f ) (Vedula, Green, & Hellman, 1999). It is essential to establish theoretical models for the evaluation of thermal shock resistance behavior of these advanced materials.…”