High-Temperature Tribotechnical Properties of Carbon-Carbon Friction Composites

Tribotechnical testing results are presented for novel carbon-carbon composites (CCCs) based on a pitch matrix and a pyrocarbon matrix material, developed by foreign companies for aircraft multidisk brakes. The carbon composites under consideration differ in the internal structure affected both by the technology of carbon fiber production and by the level of thermal treatment, as well as by many other factors. The length of the fibers used for the reinforcement of the composite matrix is varied, too. The tribotechnical properties have been determined using a laboratory tribometer according to a ring-to-ring contact scheme for normal loads ranging from 0.5 to 1.1 MPa and sliding velocities ranging from 1 to 4 m/s. The experimental investigation has been carried out with the use of a two-factor experimental design method. In order to eliminate the intense oxidation of the samples caused by the frictional heating thereof, the testing has been performed in an inert gas environment. The friction film has been studied by means of Raman spectroscopy using a green laser with a wavelength of 532 nm for excitation. The tribotechnical properties of the developed materials have been determined to demonstrate that the temperature on the friction surface exerts a significant effect on the friction coefficient and the wear rate of the material. It has been found that a frictional film is formed on a friction surface, resulting from the formation of the third body, whose film, in turn affects the tribotechnical properties of the friction pair. Depending on the structure of the composite and the maximum temperature on the friction surface, the friction film can consist both mainly of a matrix, and mainly of carbon fibers.