Carbon fiber/silicon carbide (C/SiC) composites have the potential to overcome the shortcomings of the currently used carbon and metallic friction materials in aircraft brakes. In the present work, chemical vapor infiltration (CVI), melt infiltration (MI) and polymer impregnation and pyrolysis (PIP) were used to fabricate materials for mechanical, thermal and frictional tests. PIP materials exhibited the best mechanical properties, followed by MI and CVI materials. In the case of thermal testing, MI materials were superior to the other materials. C/SiC friction coefficients were higher than the values obtained for a typical carbon composite. Wear rates of the ceramic materials were comparable to the values obtained for C/C.

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A methodology is described for protecting Carbon-Carbon fiber-matrix composite (C-C) components from oxidation for extended use in oxidizing ambients for lifetimes of the order of 10,000 hours, from room temperature to 650°C. This time-temperature profile is relevant to applications such as airborne heat exchangers. Weight changes of oxidation-protected, pitch-fiber based C-C coupons in flowing dry air at 650°C are presented. Two types of external protective approaches are compared: (a) multi-phase, borophosphate-based fluidizing overseal coatings applied directly to C-C, and (b) the same overseal coatings applied to CVD SiOxCy coated C-C. The latter, dual-coating approach provides an effective engineering solution for the above temperature-time profile and is particularly applicable to thin (0.1–3 mm thick), complex-shaped articles. The behavior of inert substrates (oxidized silicon) with the same overseal coatings is compared to the behavior of the C-C substrates. This approach can be applied with optional modifications to suit other environmental conditions, and other carbon-containing materials, such as carbon foams and C-SiC composites.

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