Investigation of the use of natural stones as automotive friction materials

One of the most important systems used in vehicles is the brake systems. The system consists of hydraulic fluid, pedals, connections, brake units and pads. The braking components within a braking system are crucial to its safe and efficient operation. The braking system includes mechanisms used to reduce or stop the speed of the vehicle. With the development of vehicles in the automotive industry, new research has emerged on braking systems. Especially in recent years, composite materials with many different components have been used in brake pads in order to minimize the cost using tribological methods. Within the scope of the thesis study, eight composite brake pads containing pumice and garnet in different mass ratios were produced from natural stones found in our country and experimental analysis was carried out. Pumice and garnet sieve analysis was performed and powders with grain sizes between 75-125 µm were used. The composite materials produced include friction modifier alumina, brass powder, cashew, binder resin, lubricant graphite, reinforcing steel fiber and filler barite. According to the specified recipe, the powders were weighed precisely and mixed in a kinetic mixer. The homogeneously mixed powders were combined by hot pressing method in the sample production mold and then the curing process was carried out. Hardness, density, friction coefficient, wear rate and disc roughness of the produced samples were measured experimentally before and after the experiment. After the experiments, the microstructure of the wear surfaces was measured using a Scanning Electron Microscope (SEM) and their surface roughness was measured three-dimensionally using a 3D profilometer. As a result, it has been observed that brake pad composites containing pumice and garnet for automobiles comply with the pad standards and show similar results to the studies in the literature.