The creep mechanism of ceramic matrix composites at low temperature and stress, by a material science approach

This paper deals with the creep mechanism for ceramic matrix composites reinforced by long ceramic fibers in a ceramic or glass-ceramic matrix, tested at low stresses (<400 MPa) and low temperatures, respectively <1673 K for the former and <1373 K for the latter. The macroscopic results give few ideas on the mechanism, but observations at different scales until high resolution evidence brittle damages which lead the authors to use the damage mechanics approach and to demonstrate that a damage creep mechanism is operating for these CMCs in two steps: (1) matrix microcrack development until its saturation, (2) followed by the opening of some of these microcracks enabling under certain conditions creep of the SiC fibers which bridge the microcracks. This was enlightened by precise damage observations on stepping creep tests and by their quantification with automatic image analysis.