Fibrous Monolithic Ceramics: II, Flexural Strength and Fracture Behavior of the Silicon Carbide/Graphite System

Abstract
The fibrous monolith microstructure consists of high aspect ratio polycrystalline cells of SiC separated by thin cell boundaries containing graphite. The SiC/100% graphite fibrous monolith has noncatastrophic fracture behavior, is damage tolerant, and is notch insensitive. The failure process is characterized by fracture along weak graphite cell boundaries. The room‐temperature flexural strength is 300–350 MPa. The estimated shear strength along the graphite cell boundaries is ∼ 15 MPa. Increasing the strength of the cell boundary by additions of SiC (40–60 vol%) results in a monolithic SiC material showing brittle fracture behavior but retaining damage tolerance. Strength and fracture behavior are also influenced by cell texture and orientation.

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