Matrix properties of textile reinforced ceramic matrix composites measuredby nanoindentation

Nanoindentation was used to measure the elastic modulus (E) and hardness (H ) of the matrix materials of three ceramic composites reinforced with woven Nicalon fiber fabrics. The matrices included: (1) alumina produced by the Dimox process; (2) silicon carbide synthesized by chemical vapor infiltrati on; and (3) a SiC/BN material produced by polymer infiltration pyrolysis. T he elastic moduli and hardnesses of the matrices of all three materials wer e found to be significantly lower than bulk ceramics of similar composition , probably due to porosity in the matrix and/or incomplete conversion of th e infiltration materials to ceramic. Each of the composites was exposed to air at 750 degreesC for 64 h, and measurements of E and H were made. The si licon carbide matrix was essentially unaffected, but two other materials ex hibited significant reductions in both E and H caused by thermal exposure.