Figure 1.  (a) Schematic of tensile loading system: sample, grippers, and AE sensor placement. (b) Cumulative AE energy vs. time and (c) location of AE events vs. time for CMC sample. In (c) the The highlighted region corresponds to the scanned length and the dashed-line box indicates the failure zone. (d) Design concept for water-cooled sample gripper with integrated AE sensor (Barnard et al., 2017).

Data gathered from in-situ tensile testing conducted at room temperature have been subjected to preliminary AE analysis. Tests proved that in-situ tomography may be used for AE investigation and that fracture start and propagation in loaded CMC samples can be reliably detected (Figure 1 ). The cumulative AE signals were used to control the load increase while the cumulative AE signal energy and signal amplitudes were continuously monitored during the tensile loading process until the sample failed. Whenever AE activity started to become antiisable, load of qua increased accumulated AE energy served as the basis for calculating additional load increments. A close correlation exists between the formation of cracks in the samples during continuing load increase and the CT scans were taken in between each loading stage.The cumulative AE energy as a function of time is shown in Figure 1b. An AE signal's energy is strongly correlated with the surface area that a fracture creates, making cumulative AE energy a reliable indicator of the course of damage. Figure 1c illustrates significant to damage The gauge as a whole and the position of the failure in relation to a region of strong AE activity just prior to failure.