Influence of fiber coating thickness on fracture behavior of continuous woven Nicalon® fabric-reinforced silicon-carbide matrix ceramic composites

Nicalon® plain-weave fiber fabric-reinforced silicon carbide (SiC) matrix composites with various pyrolytic carbon fiber/matrix interface coating thicknesses have been successfully fabricated by forced chemical vapor infiltration (FCVI) methods. The influence of the carbon interface coating thickness on the fracture behavior of these fiber fabric-reinforced SiC composites has been investigated. Experimental results indicate that fiber coating thickness significantly alters the fracture behavior of SiC composites. The fracture strength exhibits a maximum as the coating thickness increases. A theoretical model has been developed to simulate the fracture behavior in the SiC composites with varied carbon interface coatings. The model assumes that microcracking, which is due to low matrix toughness, initiates and arrests continuously. The model-predicted fracture behavior compares well with the experimental results.