Weibull analysis of strength-length relationships in single Nicalon SiC fibres

Nicalon SiC fibre is naturally brittle and offers high-temperature application in fibrous composites. Due to the randomly distributed flaws along the fibre, the statistical variability in single-fibre strength is obvious. In this paper, the effect of heat-cleaning procedures on Nicalon fibres has been investigated, and the statistical strength and variability of single Nicalon fibres have been characterized in tension and compared. Experimental results show that the strengths of single Nicalon fibres among the three types of heat-cleaning procedures are less than that of as-received unsized fibres by 22–30%. In addition, both the failure load and the failure stress of the fibres, for a given gauge length (50 mm) and yarn cross-section, can be well fitted to a two-parameter Weibull distribution. The effect of gauge length over the range from 10–175 mm, holding the strain rate constant, was also studied. The logarithmic strength-length plots show that the strength of single Nicalon fibres follows the weakest-link rule.