Low energy tribological behavior of carbon-carbon composites

The present study compares low energy tribological behavior among five different carbon-carbon composites designated "E" (2D PAN/CVI), "A" (2D pitch/resin/CVI), "TH" (high density 2D PAN/pitch), "TL" (low density 2D PAN/pitch) and "T3D" (3D PAN/pitch). Results indicate that all composites had steady-state friction coefficients close to 0.2, except for "TL" which had a much larger initial friction peak (up to 0.6) and higher average friction coefficient (nearly 0.3). Unlike the other four composites, which had quite constant friction coefficients after the initial peaks, the friction coefficient of "TH" continued to increase up to 66 meters of sliding. Weight losses of "TL" were an order of magnitude higher than those of the other four composites, due to the high wear rate during the first few minutes of sliding. After thirtysome meters of sliding the wear rate of "TL" decreased to a level comparable to those of the other four composites. Among "E," "A," "TH," and "T3D," the composite "T3D" had the largest weight loss, whereas "A" had the smallest. The composites "E" and "TH" had nearly identical weight losses up to 66 meters. For all composites, a flat and smooth self-lubricative debris film was generated on the worn surfaces after sliding for a few meters. Compared to the other composites, the debris film covering the "TH" surface was developed at a lower rate. For the present carbon-carbon composites, the development of a steady-state friction coefficient value generally occurred earlier than the development of a steady-state wear rate.