Effect of variable radius on the initial creep rate of ceramic fibres

The effect of variable fibre radius on the initial creep rate, ˙ε∗, of monofilament ceramic fibres was investigated using a numerical integration method. The following parameters were studied: (i) radius variation geometry, (ii) creep stress exponent, n, (iii) fractional radius variation, rν , and (iv) fraction,m, of the characteristic radius variation wavelength, λ; the ranges of n (0 < n < 3) and rν (0 < rν < 0.5) were chosen to be similar to those for current ceramic fibres based on the silicon carbide (SiC) system. Values of ˙ε∗ were found to be consistently greater compared to those for a constant radius fibre with an equivalent mean radius and increased with both n and rν . The main result of this work was a recommendation for creep testing of monofilament ceramic fibres to be limited to certain radius variation geometries and gauge lengths. C 2005 Springer Science + Business Media, Inc.