Creep behaviour and structural characterization at high temperatures of Nicalon SiC fibres

Abstract

Two types of Nicalon SiC fibres having different structures have been examined. Their mechanical properties and their microstructures have been studied up to 1300° C. The fall in strength above 1000° C has been shown to be due to the microcrystallization of the fibre structure. Under low loads this change in structure led to a shrinkage of the fibre. The fibres were found to creep at temperatures above 1000° C when loads greater than a threshold level were applied. The creep of the fibres has been shown to be controlled by the changes which occur to the fibre structure. Degradation of the fibres on heating in air or argon has been shown to depend on SiO2 and free carbon, which have been shown to exist in the fibre.