A multilayer ceramic matrix for oxidation resistant carbon fibers-reinforced CMCs

A concept of multilayer functional ceramic matrix has been developed to improve the oxidation resistance of carbon fiber based composites. This concept combines (i) a better control of the crack propagation through the brittle matrix by spreading a fuse material in the matrix and (ii) the use of several sealants to improve the efficiency of the sealing process in a large temperature range. The functional matrix is made of the repetition of a unit sequence (BxC1-x / B4C / BxC1-x / SiC). Processing, mechanical behaviour and oxidation resistance of the carbon fiber-reinforced multilayer ceramic matrix composites are discussed. Lifetime tests at high temperature in air are presented and results are compared to those obtained with conventional CMCs. The benefits of the multilayer matrix are extremely significant. The oxidation of carbon fibers based CMCs is reduced whereas the lifetime is strongly improved.