Full-Scale Dynamometer Test of Composite Railway Brake Shoes – Study on the Effect of the Reinforcing Fibre Type

When designing or developing friction materials, it is crucial to predict how the modification of the formulation will affect their properties. Fibres are introduced in the composition of the phenolic-based brake friction materials to improve their mechanical strength. Apart from reinforcing the composite, fibres can also affect its tribological and thermophysical properties. In this study two composite friction materials are compared. The difference between the materials was the type of reinforcing fibre used in the formulation – in one case it was glass fibre, in the other steel fibre. Thermal diffusivity of both materials was measured and thermal conductivity was calculated. Frictional characteristics determined by means of full-scale dynamometer tests are analysed and discussed. Substitution of glass fibre with steel fibre led to increase in the friction coefficient. Maximum average temperature below wheel surface, observed during the test of the material containing steel fibre, was lower as compared to the test results of the material with glass fibre in its formulation, despite higher heat flux in the course of brake applications. Thermal conductivity of the friction material was enhanced by including steel fibre in the formulation.