Chapter 10 - Macro-and micromechanics of elevated temperature crack growth in ceramic composites

Abstract

The chapter first provides a tutorial-type presentation of fracture macromechanics and micromechanics related to cracks in creeping solids, including models for creep-crack growth in monolithic solids. Next, the topic of elevated-temperature crack growth in ceramic composites is considered. General aspects of the modeling of stationary cracks containing cohesive or bridging zones are also reviewed in this chapter. Then, the chapter presents very recent models that have attempted to describe the case of growing creep cracks containing cohesive zones. All these models are preliminary and more development is necessary before specific microstructural guidelines begin to emerge for the use of ceramic composites at elevated temperature. The chapter is concerned with a fracture-mechanics description of creep-crack growth in ceramic composites—namely, in monolithic ceramics reinforced with fibers or whiskers, or a second ceramic phase. Current structural ceramic composites also include particulate-reinforced ceramic matrices; however, this category of ceramic composite is not specifically considered in this chapter. The emphasis on whisker-reinforced composites and fiber-reinforced composites reflects the generally much larger ambient temperature toughening obtained in these systems when compared to the particulate-reinforced case. In the chapter, readers will find an idea on crack building and its role in creep-crack growth.