Composite materials and methods for making the same

摘要

The present invention generally relates to mechanisms for preventing undesirable oxidation (i.e., oxidation protection mechanisms) of reinforcement materials in composite bodies. In a preferred embodiment of the invention, a coated ceramic filler material adaptable for use as a reinforcing component in a ceramic matrix composite is provided with a plurality of superimposed coatings. The coating system includes a first coating in substantially continuous contact with the ceramic filler material and one or more additional or outer coatings superimposed over the underlying coating and in substantially continuous contact therewith. Zonal junctions are formed between the filler and the first coating, between superimposed coatings, and between the outer coating and the ceramic matrix. The coatings are selected so that the interfacial shear strength of at least one of these several zones is weak relative to the other zones. Upon the application of fracture stress to the composite, the weak zone allows for debonding of the filler before the filler fractures, and pull-out or shear of the filler upon fracture of the filler. This debonding and friction pull-out enhances certain mechanical properties of the composite, and in particular, debonding improves the fracture toughness.