Paper number 441

FAILURE OF 2.5D CF-SIC COMPOSITES CREEP TESTED IN TENSION

Séverine DARZENS, Guillaume BOITIER, Jean-Louis CHERMANT, Jean VICENS

LERMAT, URA CNRS 1317, ISMRA
6, Bd Maréchal Juin, 14050 Caen Cedex, France

Summary

This paper concerns the creep behavior of 2.5D Cf-SiC composites. Creep tests have been performed in tension under a low argon pressure at 1273K-1673K between 110 and 220 MPa. From the evolution of the damage parameter vs time, a damage creep mechanism can be assumed. In order to identify such a mechanism, a microstructural investigation has been performed at different scales (by SEM and HREM). Under high testing conditions (T>1473K, (>160 MPa), it appears that the microcrack array, composed of five types of matrix microcracks, is settled upon loading and during the transient stage. During the steady state, the evolution of the damage is mainly due to the opening of these microcracks. So, the lifetime of the ceramic matrix composite will depend mostly on the ability of the interphase to protect the fibers, in other words its capability to deflect microcracks. At the microscopic scale, different types of interfacial sliding have been evidenced: at 1473K a dry friction between two rough solids, and at 1673K a viscous flow.

Keywords

ceramic matrix composite, tensile-creep, matrix microcracking, damage, fiber/matrix interphase, fiber bridging, interfacial sliding, fracture, lifetime, 2.5D Cf-SiC.