Studies on Axial and Tangential Properties of Brake Pads

The knowledge of the elastic properties of friction materials is especially important in the development of brake systems. The stiffness of the system directly impacts on the consumption of the fluid during braking and the user interaction with the brake pedal, in addition to being strongly linked to the occurrence or not of certain types of noise. For the analysis of brake pad stiffness, is well known the compressibility equipment, which evaluates the deformation subject to a load in the axial direction. The first stage of the work proves that the compressive deformation of the pad has a non-linear behaviour as a function of the applied force. Based on this non-linearity, tests are carried out on 93 brake pads, where trends between the instantaneous deformation and the final compressibility result are sought. In the second step, we try to evaluate the stiffness of the friction material in the tangential direction, where a new method is proposed using the shear equipment, also well known in the brake industry. The ultimate goal is to correlate these stiffness parameters with natural frequencies from modal analysis, since it is a quick, inexpensive and non-destructive test to qualify brake pads.