Mechanical behavior of a NextelTM 610/alumina-silica, oxide/oxide ceramic matrix composite

Oxide/oxide ceramic composites can be used for structural applications operating continuously at temperatures between 500°C and 900°C under oxidizing environment, such as in areas close to aircraft engines. In particular, composites based on a matrix combining alumina and silica are promising because this system has good mechanical properties up to 1000°C and allows to limit the grain coarsening in Nextel 610 alumina fibers. In this work, the mechanical behavior of a Nextel 610/alumina-silica oxide/oxide ceramic matrix composite is studied. The matrix system initially associates submicron particles of alumina (AKP-50, d50 = 200 nm, Sumitomo Chemical Co. Ltd.) and colloidal particles of silica (Ludox AS-40, d50 = 20 nm, Grace Davison). Unidirectional composite plates were manufactured. The fibers were impregnated with the suspension by contact molding and the green body was subsequently sintered. The composite material was then characterized. In particular, the elastic properties and the behaviors in diametral compression and in 4-point bending were determined. The mechanical behavior of the material is closely related to its microstructure which results from the flow of the viscous silica phase during sintering. In addition, the influence of the alumina-silica ratio is discussed. Relationships between processing/microstructure/properties were finally established by considering the behavior of the matrix system during the various stages of the manufacturing.