Off-axis creep of a ceramic-matrix/continuous-ceramic-fiber composite: Experimental evaluation

摘要

The compression creep of a unidirectionally reinforced, SiC continuous fiber/calcium aluminosilicate (anorthite) glass-ceramic matrix composite was evaluated experimentally. Experiments covered the stress (-sigma (1)) and temperature (T) ranges of 20-40 MPa and 1300-1320 degreesC, respectively. The experiments also emphasized characterization of the rheology as a function of the angle of misorientation (phi) between the applied compressive load and the direction of reinforcement. For any given sigma, T condition, the highest steady-state strain rate occurred for phi similar to 50 degrees (up to an order of magnitude faster than in the transverse, phi = 90 degrees, case); overall composite strain in this case included a substantial contribution from displacement across the fiber-matrix interface. The data reveal that the interfacial rheology responsible for the displacement is distinctly temperature sensitive. Evaluation of the composite flow through its comparison to numerical/rheological models that scrutinize the interfacial effect implies that the interface is characterized by a non-Newtonian viscous rheology; this suggests that the interface response involves specifically the flow of the thin amorphous silica interphase that comprises a portion of the fiber-matrix interface in this material. The overall plastic response of the unidirectionally reinforced material is nevertheless rate-limited by plastic flow of the matrix and can be described by the superposition of three modes of strain, the magnitude of each being dependent specifically on phi. (C) 2001 Kluwer Academic Publishers. [References: 31]