RECENT DEVELOPMENTS IN SIC MONOFILAMENT REINFORCED SI3N4 COMPOSITES

The use of SiC monofilament to reinforce a Si3N4 matrix has led to a refractory ceramic composite with outstanding high temperature properties. These composites provide many of the properties required for future generation aerospace applications and make viable candidates for structural applications where use temperatures exceed 1350-degrees-C. SiC/Si3N4 composites are fabricated by using collimated fibers and a matrix slurry to produce preform tapes. Fully densified composites are achieved by hot pressing of tapes. Various aspects of the work related to shape forming, fabrication techniques, joining and processing considerations are addressed. Data are presented on high temperature tensile strength, impact characteristics, and environmental behavior. Recent developments are centered about the use of 75-mu-m diameter SiC monofilaments in conjunction with hot isostatic pressing techniques to produce more complex shapes and improved properties.