Multilayer fiber coating comprising alternate fugitive carbon and ceramic coating material for toughened ceramic composite materials

Abstract

A fiber-reinforced ceramic-matrix composite material exhibiting high tensile strength, high fracture toughness and high-temperature oxidation resistance is produced by alternatively depositing multiple thin layers of ceramic material separated by very thin intermediate layers of fugitive carbon onto the fiber reinforcement prior to the subsequent densification with the ceramic matrix. The energy behind propagating matrix cracks in the resulting composite material are effectively dissipated by the progressive increase in crack deflection/branching and frictional slip through the successive ceramic layers of the multilayer fiber coating system. These energy release and arrest mechanisms sufficiently impede the driving force behind unstable crack propagation and render the cracks non-critical, thereby serving to blunt and/or divert propagating matrix cracks at or around the reinforcing fiber. While significantly increasing the strength and fracture toughness of the composite, the multilayer refractory fiber coating system enables the composite to remain oxidatively stable when stressed at or beyond the matrix cracking stress point and subsequently exposed to temperatures above 800.degree. C. in air.

Dependencies are inferred from the claim text.