Microcracking mechanism in a SiCf-SiBC composite creep-tested in argon

This paper addresses the creep behaviour of a woven SiCf-SiBC composite, tested in tension under a partial pressure of argon, between 1273 K and 1473 K. It appears that the creep strain begins from 1273 K and becomes larger at higher temperatures. Moreover, the shapes of the creep curves led to the assumption of the existence of two competing deformation mechanisms depending on the temperature domain. The creep mechanism involved is microcrack damage-creep. From higher resolution studies at higher scales (scanning electron microscopy, transmission electron microscopy (TEM) and high resolution electron microscopy (HREM)), many types of damage were observed, for example matrix microcracking, fibre/matrix debonding and fibre/matrix sliding. The observations via TEM and HREM enabled us to specify the existence or not of the classical creep mechanism of the constituents of the composite, and also to characterize the behaviour and the role of the different interfaces and especially of the pyrocarbon interphase. These multiscale observations will be discussed in order to highlight the creep-damage mechanism as a function of temperature of the SiCf-SiBC composites.