Characterization of interfaces in C fiber-reinforced laminated C–SiC matrix composites

Interfacial studies of carbon fiber-reinforced laminated matrix composites (LMCs) of alternating matrix layers of SiC and carbon prepared by forced-flow thermal-gradient chemical vapor infiltration (FCVI) have been undertaken by transmission electron microscopy (TEM). The carbon–carbon interfacial region consistently displayed distinctive features that enabled the microstructures of the fiber carbon, a thin carbon layer deposited as fiber coating, and the matrix carbon to be distinguished. A thin discontinuous layer of relatively lower graphitic degree was observed at the interface of the fiber and its carbon coating, whereas the interface between the fiber coating and the first carbon layer of the matrix displayed a thin, patchy, and partially ordered layer. At the C–SiC interfaces within the matrix, the interface was observed to be well-defined on one side with the c-axis of the pyrocarbon layers nearly perpendicular to the interface, but, at the other end, the interface appeared rough and somewhat diffuse due to the nature of SiC growth during CVI.