IN-SITU OBSERVATION OF THE SINGLE-FIBER FRAGMENTATION PROCESS IN METAL-MATRIX COMPOSITES BY ULTRASONIC-IMAGING

Single-fiber fragmentation tests with continuous silicon-carbide fiber s in a Ti-6Al-4V alloy matrix have been conducted with in situ ultraso nic imaging to monitor the fragmentation process. Straining proceeded incrementally on a specially designed load frame with acoustic emissio n detection (AE) performed during each increment, and shear-wave back reflectivity (SBR) ultrasound images were acquired following each incr ement. Metallographic examination of the fragmented fiber was performe d following the straining sequence by electropolishing and scanning el ectron microscopy. Good agreement was found between the fiber breaks i maged by ultrasound, the number of breaks detected by acoustic emissio ns, and the breaks observed by metallography.