Recent developments in fibers and interphases for high temperature ceramic matrix composites

The long term durability of CMCs is limited by two factors: (1) creep and rupture of the fibers, and (2) environmental degradation of the constituents, primarily in the nonoxide composites. Oxide CMCs are limited by the creep resistance of the fiber at this stage of development and by interphase concepts that are not yet mature. Nonoxide fibers have been developed with excellent creep resistance relative to oxide fibers, but oxidation of the interphase and the interface, particularly at intermediate temperatures, causes embrittlement of these composites. This effect is particularly severe when matrix cracks are present and under cyclic loading conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.