Abstract
Uniaxial fatigue damage analyses were performed on borosilicate glass-ceramic matrix, Nicalon (silicon carbide) fibre reinforced unidirectional composites. The fibre volume fraction varied from about 0.25 to 0.60. Load-controlled tension-tension fatigue tests (R ratio = 0.1) were conducted at room temperature and 540°C (1000°F). The fatigue life was found to decrease with increasing cyclic stress level and a power-law relationship of the form σapp = σuts(2N f)b was established where σapp is the applied maximum stress, σuts the monotonic tensile strength, N f is the number of cycles to failure and b is the fatigue strength exponent. The fatigue damage evolution manifested itself as a decrease in stiffness of the composite with fatigue cycles. This stiffness drop was associated with matrix cracking followed by fibre-matrix debonding and fibre sliding breakage/pull-out, and final failure, respectively at 540°C. The damage evolution at room temperature was associated with degradation of the matrix followed by steady breakage of fibres with no debonding/pull-out, leading to eventual failure of the net section of the composite. In general, quantitative microscopic observations of debonded and pulled-out fibres showed a good correlation with the observed reduction in stiffness. A predictive model to interpret the drop in stiffness is presented and validated using experimental results from the current study.
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Ramakrishnan, V., Jayaraman, N. Fatigue behaviour of borosilicate glass-ceramic matrix, nicalon (silicon carbide) fibre composites. JOURNAL OF MATERIALS SCIENCE 28, 5580–5591 (1993). https://doi.org/10.1007/BF00367834
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DOI: https://doi.org/10.1007/BF00367834