Rw. Neu et I. Roman, ACOUSTIC-EMISSION MONITORING OF DAMAGE IN METAL-MATRIX COMPOSITES SUBJECTED TO THERMOMECHANICAL FATIGUE, Composites science and technology, 52(1), 1994, pp. 1-8
Acoustic emission (AE) was monitored during thermomechanical fatigue (
TMF) tests conducted on a silicon carbide fiber, titanium alloy matrix
composite, SCS-6/TIMETAL(R)21S. The tests were stress-controlled with
a stress Patio of 0.1, and temperature was cycled from 150 to 650 deg
rees C. In-phase and out-of-phase TMF cycling were characterized by di
stinct AE behavior The pare of fiber fractures as indicated by AE duri
ng in-phase cycling was much higher than during out-of-phase cycling,
correlating with metallography and micromechanics analyses which indic
ate thar the fiber stress is higher under in-phase than out-of-phase c
ycling. The fiber fracture rate was proportional to the maximum fiber
stress and remained nearly constant during most of the test. The Fate
was greater during the early cycling as well as near the end. AE also
indicated that most of the early cyclic damage occurred during the ini
tial loading.