Time-dependent failure mechanisms in silicon carbide composites for fusionenergy applications

Silicon carbide has many properties that are attractive for applications in fusion energy systems. The reliability of monolithic silicon carbide, howe ver, is insufficient for its use in large components. Ceramic matrix compos ites offer greater flaw tolerance and reliability, but their failure mechan isms are less well understood. This work has focussed on studying potential failure mechanisms in silicon carbide fiber-reinforced, silicon carbide ma trix (SiCf/SiCm) composites. In the event of pre-existing cracks, subcritical crack-growth may occur due to creep of fibers that bridge the crack faces. Irradiation-enhanced creep will enhance the subcritical crack-growth rate. The presence of oxygen lea ds to oxidation of the interphase material and subcritical crack-growth con trolled by the rate of interphase recession. Tn addition, fiber shrinkage o r weakening due to exposure to radiation can promote additional failure mec hanisms, including embrittlement. These mechanisms, the conditions, under w hich they occur, and the current state of models of the crack-growth mechan isms will be discussed. (C) 2000 Elsevier Science B.V. All rights reserved.