Damage initiation and propagation in a SiC_f/SiC ceramic matrix composite (CMC) is being studied in the context of the material’s use in high performance aerospace engines. Acoustic emission (AE) assessment is now routinely employed to assess the condition and performance of an assortment of CMC specimen types in a variety of mechanical stress configurations. This article investigates the differences in AE activity between specimens with stress concentration features and plain dog bone specimens with no stress concentration features. Stress concentration factors of K_t=2.4 and K_t=4.5 were created by machining central circular and elliptical holes respectively. All specimens were subject to tensile mechanical stress at room temperature in monotonic and cyclic fatigue loading regimes with incremental step increases in peak stress.

The influence of stress concentrations on the mechanical performance of the material was explored. AE was monitored with a two-channel system, allowing a linear location-based approach as well as traditional feature-based analysis including cumulative AE energy. Correlation of localised AE accumulation with respect to the location of stress concentrations was investigated and compared to the distribution of AE accumulation in plain coupons. The work further develops understanding of AE to deduce the overall damage condition of the material, and to determine the precise modes of damage that exist at different stress states.