MI SiC/SiC CMCs with a single edge notch were tested in monotonic uniaxial tension, tensile-tensile fatigue loading, and unload/reload to failure to understand the acoustic emission and change in electrical resistance associated with damage development and from a single-edge notch. For the latter test a camera was used to observe surface cracking. Acoustic Emission (AE) occurred mostly in the notch region associated with highly localized matrix cracking emanating from the stress-concentrator. Four-point electrical resistance (ER) measurements were performed in-situ and were observed to correlate with AE activity. For the fatigue test, an abnormally large amount of AE activity was observed which was discerned to be from crack closure during the "valley" of the fatigue cycle. These types of events are not common for other symmetric stress-concentrators (hole or double-edge notches) of the same composite system. Both AE and ER detected increased activity when the composite was approaching failure. For the unload-reload test, two four-point measurements were performed, one across the edge notch and the other on the opposite un-notched side in order to assess the difference in ER change as to lead placement. For the unload-reload test with a camera, surface cracks were detected only very near the ultimate failure of the composite, potentially due to a lack of resolution or because cracks were not open enough to detect visually.
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