Understanding the creep behavior of a 2.5D C-f-SiC composite II. Experimental specifications and macroscopic mechanical creep responses

Macroscopic results for a 2.5D C-f-SiC composite creep tested in tension ar e presented. After the development and the optimization of a new accurate h igh temperature tensile device, tests were conducted in argon, under a redu ced pressure, for stresses ranging from 110 to 220 MPa and temperatures bet ween 1273 and 1673 K. The macroscopic mechanical creep responses of the com posite were analyzed and interpreted. Since ceramic matrix composites (CMCs ) contain constituents of a different nature, with an influence of a struct ural aspect, it is not possible to apply the hypotheses of homogeneity and isotropy as described in Dorn's theory. Consequently, the physical meaning of the mechanical parameters, obtained by such a classical treatment, is li mited. It is then necessary to discuss the global creep responses using an approach based on damage mechanics, which is more consistent with the speci fic features of the CMCs. This new approach adopted here reveals less class ical parameters to be more accurate indicators of the creep behavior and th e strain mechanisms of the 2.5D C-f-SiC composite. (C) 2000 Published by El sevier Science S.A.