High Temperature Mechanical Assessment of a SiCf/SiC Ceramic Matrix Composite in a Vacuum Environment

Abstract Due to their excellent specific strength and stiffness at elevated temperatures, ceramic matrix composites (CMCs), in particular silicon carbide fibre reinforced silicon carbide (SiCf/SiC) CMC systems, have been designed for application in the hot sections of the gas turbine engine. In comparison to their nickel superalloy counterparts, CMCs have the potential to operate at higher temperatures whilst reducing the requirement for intricate internal cooling systems. Nonetheless, because of their complex structural architecture resulting from multiple steps of manufacture, CMCs can subsequently exhibit a range of damage modes. Therefore, to enable a comprehensive understanding of material behaviour, damage progression and accumulation needs to be studied under a range of thermomechanical conditions and environments. This article describes the development of a high temperature mechanical testing capability for the purpose of assessing a SiCf/SiC CMC under vacuum. Monotonic and cyclic loading tests were performed at ambient and high temperatures in air and vacuum environments to investigate the influence of temperature and environment on mechanical behaviour. Results demonstrate an improvement in mechanical performance at high temperature under a vacuum environment compared to high temperature tests performed in air. Fracture surfaces were analysed to validate these results and provide insight and understanding of associated damage mechanisms.