Mechanical behavior in ceramic matrix composites with fugitive fiber coatings

The sliding and debonding behaviors of ceramic fibers with fugitive coatings in a ceramic matrix composite were characterized using non-destructive and mechanical test techniques. The fugitive coating approach in high temperature brittle matrix composites was found to be a viable methodology for enabling toughening in oxide materials. Carbon was used for the fugitive coating, sapphire for the fibers and polycrystalline alumina for the matrix.; The materials selection assured minimal thermal mismatch stress. The effects of fiber roughness and coating thickness were characterized including roughness dampening. High temperature heat treatments were conducted to explore the stability of the interface with respect to sliding. At temperatures greater than the process temperature interface properties severely changed such that class II or III composite mechanical behavior is anticipated. At temperatures below the process temperature more moderate changes occurred indicating a potential application of this approach.; A model to simulate fiber displacement was developed and compared with experimental data. The comparison indicates that trends in load-displacement behavior are realistically captured. Parametric studies reveal the sensitivity of pushout load on interface geometric parameters.