Friction and wear of PAN/pitch-, PAN/CVI- and pitch/resin/CVI- based carbon/carbon composites

In this study we compared the tribological behavior under a high speed condition (1.7 MPa, 2000 rev min^-1) of six different carbon/carbon composites including three two-dimensional PAN/pitch composites (TH, TM and TL), one two-dimensional PAN/CVI composite (E), one two-dimensional pitch/resin/CVI composite (A) and one three-dimensional PAN/pitch composite (T3D). Results indicated that, among the five two-dimensional composites, TM and E performed significantly better than the other three composites under the present condition. Both TM and E exhibited a reasonably low friction coefficient (both about 0.4) and a wear rate that was an order of magnitude lower than those of the other three. A transition in friction occurred for A, TH and TM, but not for E or TL. The pre-transitional friction coefficients of the three composites were 0.1-0.2, similar to those measured under the low speed condition. During transition, the initially formed thin, smooth lubricative film was suddenly disrupted and turned into a thick powdery debris layer that caused the friction coefficient to rise abruptly to 0.5-0.9. The powdery debris on TM and E was easily "ironed" into a smooth and tight lubricative film to cause both friction and wear to decline. The three-dimensional composite T3D was not suitable for high speed applications owing to extensive structural damage.