The design of the fibre-matrix interfacial zone in ceramic matrix composites

Abstract Ceramic matrix composites are tough when the fibre-matrix bonding is properly controlled during processing, via the use of an interphase. The interphase is either formed in situ as the result of fibre-matrix interactions or deposited on the fibre surface prior to composite fabrication. It has several key functions, including crack deflection, load transfer, diffusion barrier and residual stress relaxation. Four types of interphase are depicted involving weak interfaces, materials with a layered crystal structure (pyrocarbon, BN, micas and phyllosiloxides, or materials with the β-alumina/magnetoplumbite structures), multilayers such as (PyC-SiC)n or (BN-SiC)n or, finally, porous materials. Achieving high mechanical properties and long lifetimes in severe environments require a subtle design of the fibre-matrix interfacial zone, which is depicted for Nicalon/glass–ceramic and Nicalon/SiC-matrix composites.