A CVI-processing marker study

Abstract

Fiber reinforced ceramic composites greatly extend the region of application for ceramic materials because the inclusion of a second phase such as fibers helps to prevent catastrophic failure via the mechanisms of crack branching, deflection, bridging and fiber pull-out. While ceramic composites are excellent candidate materials for high temperature structural applications, many conventional manufacturing processes damage the fibers during fabrication and thereby reduce the strength and toughness from what is theoretically possible. Chemical vapor infiltration (CVI) is an effective and versatile technique for fabrication of ceramic matrix composites which promises to reduce fiber degradation.While CVI is no longer a truly novel processing technique, it is still difficult to predict the best set of operating conditions for what can be a tedious process. Conventional CVI methods may take up to a week to fully infiltrate a small part and even state-of-theart forced flow-thermal gradient CVI (FCVI) processing takes the better part of a day. It is, more over, difficult to monitor the evolution of deposition within a, for example, woven preform.