Paper number 781


Jun Liu and Paul Bowen

School of Metallurgy and Materials/IRC in Materials for High Performance Applications
The University of Birmingham, Birmingham, B15 2TT, UK
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Summary Stable and unstable fatigue crack growth in titanium matrix composites (Ti MMCs) has been studied with emphasis on the influence of specimen geometry, loading configuration, and fibre strength distribution. Particular attention has been paid to the maximum initial stress intensity factor, K0,max, above which eventual catastrophic failure results. Experimental results show a marked influence of initial notch size and specimen width: a small notch under high stress is found to be more damaging than a large notch under low stress; and wider specimens can sustain higher K0,max than narrower ones. Some influence of loading configuration is also found in that unstable fatigue crack growth is often more likely to occur under tension-tension than under three-point-bending. The importance of fibre strength distribution on fatigue crack growth in Ti MMCs has also been investigated by means of measurement of fibre strength in the composites and theoretical analysis of stresses in bridging fibres.
Keywords titanium-matrix composites, fibre-reinforced composites, silicon carbide, fatigue crack growth, notch effect, fibre strength degradation, fibre strength distribution.

Theme : Metal Matrix Composites ; Characterisation and Modelling

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