MECHANICAL TESTING OF OXIDATION-PROTECTED CARBON-FIBER-REINFORCED CARBON AT HIGH-TEMPERATURES

Carbon-fibre-reinforced carbon in a bidirectional, satin weave layup a nd protected against oxidation by liquid silicon infiltration, and wit h CVD SiC and SiO2 protecting and sealing layers on the surface, was i nvestigated under the combined influence of load in bending, temperatu re (800-1250 degrees C) and oxidation (flowing air). From the limited number of experiments the following could be concluded: the protected material showed non-linear stress/strain behaviour in comparison to th e unprotected composite; the lower the temperature, the less effective the protection; for static loads at 1200 degrees C the lifetime drops drastically beyond a certain threshold stress and tensile stresses ar e more dangerous than compressive strain. The most effective method of testing a protecting system proved to be thermocycling under constant load.