Acoustic emission monitoring of temperature-dependent tensile behavior of unidirectional SiCf/SiC ceramic matrix composites

Ceramic matrix composites (CMCs) are of interest for high-temperature structural applications, including use in turbine engine components. Knowledge of high temperature damage mechanisms is critical to predict the durability of these systems. SiC_f/SiC minicomposite specimens were tested in tension at room temperature, and at elevated temperatures of 1200°C, 1315°C, and 1482°C, to understand the effect of temperature on the mechanical properties, damage mechanisms, and acoustic emission (AE) response. Damage initiation and accumulation was monitored using AE during tensile tests at each temperature. Temperature dependence of mechanical properties including elastic moduli, ultimate tensile strength, AE-based onset of matrix cracking, proportional limit, and crack density were investigated. The specimen toughness and ultimate tensile strength decreased with an increase in temperature. The decline in mechanical strength properties and extent of minicomposite matrix cracking as the temperature was increased was related to interactions between the specimen matrix, fiber, and interphase.