Abstract
The successful application of SiC/SiC ceramic matrix composites as high-temperature structural materials depends strongly on maximizing the fracture or rupture life of the load-bearing fiber and matrix constituents. Using high-temperature data measured under stress-rupture test conditions, this study examines in a mechanistic manner the effects of various intrinsic and extrinsic factors on the creep and fracture behavior of a variety of SiC fiber types. It is shown that although some fiber types fracture during a large primary creep stage, the fiber creep rate just prior to fracture plays a key role in determining fiber rupture time (Monkman–Grant theory). If it is assumed that SiC matrices rupture in a similar manner as fibers with the same microstructures, one can develop simple mechanistic models to analyze and optimize the stress-rupture behavior of SiC/SiC composites for applied stresses that are initially below matrix cracking.
Highlights
For long-term structural applications under high-temperature oxidizing conditions, research efforts are ongoing throughout the world to develop SiC fiber-reinforced
SiC/SiC composites are still in their infancy in terms of selecting and demonstrating the optimum fiber, interphase, and matrix constituents, there currently exists a strong need for studies that mechanistically analyze and predict the fracture-limited envelope of thermostructual capability provided by currently available constituents
Since the time-dependent fracture of these materials is controlled by creep-induced flaw growth, these models are based on key experimental observations made on the creep-rupture behavior for various SiC fiber types
Summary
For long-term structural applications under high-temperature oxidizing conditions, research efforts are ongoing throughout the world to develop SiC fiber-reinforcedSiC matrix composites [1,2]. SiC/SiC composites are still in their infancy in terms of selecting and demonstrating the optimum fiber, interphase, and matrix constituents, there currently exists a strong need for studies that mechanistically analyze and predict the fracture-limited envelope of thermostructual capability provided by currently available constituents. Since the time-dependent fracture of these materials is controlled by creep-induced flaw growth, these models are based on key experimental observations made on the creep-rupture behavior for various SiC fiber types. These observations are important because the fibers are the primary structural constituents controlling ultimate composite rupture, and because SiC fibers display microstructures and fracture behavior representative of SiC matrices, which can carry structural loads in SiC/SiC composites
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