LOW-ENERGY WEAR BEHAVIOR OF POLYACRYLONITRILE, FIBER-REINFORCED, PITCH-MATRIX, CARBON-CARBON COMPOSITES

The present paper reports low-energy wear behavior of two-dimensional (2D) and three-dimensional (3D) polyacrylonitrile, fiber-reinforced, pitch-matrix, carbon-carbon composites, as well as a commercial bulk graphite. Results indicate that, under the same conditions, the 2D composite at all times had a larger weight loss than the 3D composite and the bulk graphite. In the first few minutes of wear, weight loss of the 2D was an order of magnitude higher than those of the other two materials. With time, the wear rate of the 2D composite continued to decrease, and eventually approached a level comparable to that of the other two materials. Scanning electron microscopy shows that formation of a debris film is critical to the wear behavior of all three materials. Once a smooth, adherent, and uniform debris film is developed on sliding surfaces, the wear rates dropped at the same time. The much larger wear in the wear-in period of the 2D composite might be explained by the quick formation of loose powdery debris, which presumably escapes from the sliding surfaces more easily.