For more than a decade, investigations of the surface topography and chemical behavior of the boundary layer have been performed. This is of great importance for the understanding of friction, as it provides valuable insights into the dynamic processes that influence the brake pad's performance. The adaption of the boundary layer to a new load condition is of particular interest because it allows for the identification and description of mechanisms that influence macroscopically-observable effects, and quantities such as the coefficient of friction. It is possible to determine time constants that describe this process of adaption.
The investigations discussed in this paper combine tribometer tests and optical investigations at the same time. Therefore, the measured coefficient of friction can be related to the observed surface topography of the brake pad. Using a scaled laboratory-tribometer eliminates the influence of the complete brake system and allows for a highly flexible design of test procedures. This is necessary for an insightful study of the adaptation processes of the boundary layer. The generated information can be used for a macroscopic description of the friction process using dynamic friction laws with a suitable parameterization.
