In order to obtain a better understanding of the role of tribofilms during automotive braking, their structures were investigated and the essential features identified. Next, different ingredient combinations were studied by preparing some model materials with simpler compositions than real tribofilms. A test method was developed for verifying the tribological properties of the model materials and for comparison with results obtained with numerical sliding simulations of such structures. Prerequisites of good brake performance properties were identified. Although the coefficient of friction could be varied in a wide range, smooth sliding conditions could only be achieved with values smaller than 0.4. Tests with artificial third body powders turned out to be useful as screening method for the selection of raw materials for brake pad formulations.
Werner Österle, Cornelius Deutsch, Ilona Dörfel, Thomas Gradt, Ines Häusler, Guillermo Orts-Gil, Claudia Prietzel, Thomas Schneider - Federal Institute for Materials Research and Testing, Max Planck Institute of Colloids and Interfaces, Institute for Colloidal Chemistry at University Potsdam