Mechanical properties and real-time damage evaluations of environmental barrier coated SiC/SiC CMCs subjected to tensile loading under thermal gradients

Environmental barrier coating (EBC) coated ceramic matrix composite (CMC) systems are currently being investigated for use as turbine engine hot-section components in extreme environments. In these extreme conditions, it becomes critical to understand material response to environmental exposure and performance under thermo-mechanical loading. Electrical resistance (ER) monitoring has recently been correlated to tensile damage accumulation in SiC/SiC CMCs, and the focus of this study is to extend the use of ER to evaluate high-temperature thermal gradient fracture of EBC/CMC systems. Tensile strength tests were performed at high temperature (1200°C) using a laser-based heat-flux technique. Specimens included an as-produced SiC/SiC CMC and coated SiC/SiC substrate that have been exposed to simulated combustion environments in a high-pressure burner rig. Localized stress-dependent damage was determined using acoustic emission (AE) monitoring and compared to full-field strain mapping using a high-temperature digital image correlation (DIC) technique. The results are compared with in-situ ER monitoring, and post-test inspection of the samples in order to correlate ER response to damage evolution. •Decrease in retained properties post HPBR exposure shows degradation of uncoated specimen and performance of EBC system•ER shown to be an effective tool for in-situ damage monitoring of MI SiC/SiC CMCs under high-temperature thermal gradients•AE energy analysis showed good agreement with DIC strain mapping in terms of damage location and distribution•AE waveform analysis revealed some differences in frequency content and energy between the coated and uncoated samples