MICROSTRUCTURAL EVALUATION AND FIBER DEBONDING IN ALIGNED CERAMIC-MATRIX COMPOSITES

The slice compression test (SCT) represents a new approach for the estimation of the interfacial shear stress and debond length in fiber-reinforced ceramics. The technique is based upon multiple measurements and simultaneous loading of a large number of fibers in the test specimen. The specimen slice is compressed between a hard ceramic anvil and a ductile metal to produce interfacial debonding and slippage as a result of the fiber/matrix elastic mismatch. The extent of fiber protrusion under maximum load and the residual protrusion of the fibers after load relaxation are the experimentally determined parameters and have been measured for a laminate reinforced with Nicalon SiC fiber (LASIII). The minimum applied stress for the initiation of debonding was estimated. In addition, the microstructure of the ceramic composite was quantitatively characterized to determine numerical values of the microstructural parameters which could affect the interfacial shear stress. The fiber diameters and spatial fiber distribution were determined to obtain the degree of order of the fibers within the composite.