C Fiber Reinforced Ceramic Matrix Composites by a Combination of CVI, PIP and RB

Abstract

Continuous fiber-reinforced SiC matrix composites present excellent properties particularly as high temperature lightweight structural materials. Nevertheless widespread application of this class of materials is presently hindered mainly due to the very expensive production processes. Among them, Chemical Vapor Infiltration (CVI) and pre-ceramic Polymer Impregnation and Pyrolysis (PIP) into fibrous preforms do not seem to be susceptible of major improvements concerning cost reduction of processes and raw materials.Silicon melt infiltration inside fibrous preforms provided with a porous carbon matrix to be converted into silicon carbide through reaction with silicon (RB), is a potentially cheap process even if quite high processing temperatures are needed (∼1500 °C).The main problems concerning this process are related to unavoidable residual free silicon dispersed inside the reaction bonded matrix and to fiber stability at the processing temperatures. The only commercial SiC fibers (Nicalon C.G.) are still quite expensive and suffer degradation at temperatures exceeding 1300 °C. Therefore the obvious choice for fiber reinforcement is the use of carbon fibers which are intrinsically stable at the processing temperatures.