Damage Tolerant Oxide Ceramics Using Pure Fiber and Matrix Laminates

摘要

A fiber-reinforced ceramic composite was developed using matrix-infiltrated and non-infiltrated fiber layers. Processed layers were hot-pressed together resulting in an oxide-fiber (Nextel720), oxide-matrix (mullite) composite. Matrix slurries were prepared using submicron-sized α-Al_2O_3 powder coated with amorphous SiO_2, along with additives to decrease mullite-formation temperature.rnRoom temperature 3-point bend tests were conducted on as-received samples and samples exposed to long-term, high-temperature oxidation. Composites demonstrate both reasonable fracture strength and damage tolerance. The favorable thermo-mechanical behavior can be explained by the composite's laminate-type structure. Matrix-infiltrated fiber layers provide strength but behave in a brittle, quasi-monolithic manner. Non-infiltrated fiber layers connect infiltrated layers, and provide damage tolerance through in-plane crack deflection and crack bridging. Varying matrix-to-fiber ratio allows tailoring of composite properties, trading off strength for damage tolerance. These composites provide damage tolerant behavior in the absence of fiber interface coatings, and when using a matrix which bonds strongly to fibers.