Multi-braking tribological behavior of PAN-pilch, PAN-CVI and pitch-resin-CVI carbon-carbon composites

This paper compares the multiple braking behavior of a polyacrylonitrile fiber-pitch matrix (PAN-pitch), polyaclylonitrile fiber-chemical vapor infiltrated (PAN-CVI) matrix and mesophase pitch fiber-phenolic resin-chemical vapor infiltrated hybrid matrix (pitch-resin-CVI) carbon-carbon (C-C) composites. Results indicate that the tribological behavior of all three composites is sensitive to their worn surface morphology. The average friction coefficient of pitch-resin-CVI composite is much higher than that of the other two composites. The pre-transitional type low friction coefficients repeatedly appear in PAN-pitch and PAN-CVI composites, but never in the pitch-resin-CVI composite once the first transition occurs. Compared to pitch-resin-CVI, the high friction coefficients of PAN-pitch and PAN-CVI are much easier to be brought back to their pre-transitional levels by subsequent braking tests. The variations in wear of the three composites have similar trends to those in friction. The higher the friction coefficient during a braking test, the larger the weight loss. Among the three composites, PAN-pitch has the lowest average weight loss and appears to have the most stable performance. The pitch-resin-CVI composite is more susceptible to sliding-induced structural damage than the other two composites. (C) 2000 Elsevier Science S.A. All rights reserved.