In situ strength distribution of carbon fibers in unidirectional metal-matrix composites-wires

Based on an etching method and the fiber-bundle tensile testing technique, a new method has been developed for the testing and characterization of the strength distributions of in situ fibers in unidirectional aluminum-matrix-composite wires. According to this method, a systematic study on in situ properties of T300 fiber and M40J fibers in MMCs wires have been performed at strain rates ranging from 0.001 to 1300 1/s. Experimental results show that both T300 fiber and M40J fibers are strain-rate insensitive materials. Results also show that the modulus, ultimate strength and unstable strain of two fibers have been degraded to some degree by high-temperature processing. Micrographs indicate that there are obvious crack distributions on the surfaces of in situ fibers and this is the main reason for the decreasing fiber strength. On the basis of the fiber-bundles model and the statistical theory of fiber strengths, the distribution parameters for in situ fiber strength have been obtained. The evaluated stress/strain curves from the theoretical model are in good agreement with the test data. Statistical analysis results show that the high-temperature manufacturing processing only affects the Weibull scale parameter, σ0, of T300 fibers and does not affect the shape parameter, β whereas for M40J fibers, both the shape and scale parameters have been changed by high-temperature manufacturing processing.