ИСТИНА

Fibrous composite materials are a relatively soft matrix in which there are more rigid fibers. An example of such composites are carbon-carbon composites (carbon fibers are located in the carbon matrix), which are used in the manufacture of brake discs. To calculate the wear characteristics of such composite at the macro level, the wear contact problem with the wear coefficient variable over the surface was formulated and solved based on the method developed in [1]. This coefficient describes the wear rates for the fiber, matrix and transition layer between the fiber and the matrix. Based on the results of the mathematical modelling, it was concluded that the initially smooth surface of the composite becomes wavy during wear process, and the geometrical parameters of the worn surface are determined by the geometrical and tribotechnical parameters of the carbon matrix and carbon fibers. The wear process was analyzed for different values of the ratio of matrix and fiber wear coefficients. It was concluded that if the fibers are characterized by a lower wear coefficient than the matrix, the fibers protrude above the surface of the matrix in wear process. Under certain conditions it can lead to their separation from the surface. This case is typical, in particular, for carbon-carbon composites with carbonized fibers. In the case when the fibers are characterized by a higher wear coefficient than the matrix (this case, in particular, corresponds to the carbon fiber composite with graphitized fibers), as the simulation results showed, the fibers lie below the matrix level on the worn surface or almost at the same level with it. The simulation results are in a good agreement with the experimentally measured microgeometry of the worn surface of such composite materials. The analysis of the effect of the structural parameters of the fibrous composites on their effective wear rate was also carried out. The results of the study can be used in the design of the fibrous composite materials to improve their tribotechnical characteristics.