Startup company LF GmbH & Co. KG (Leverkusen, Germany) develops and produces friction materials for industrial clutches and brake linings. In contrast to established technologies, the special way in which they are manufactured allows "intelligent" friction linings to be produced, as they are made from liquid phase and pressureless in a comparatively low temperature range (120°C). As part of the implementation project, experts from LF GmbH and her research partner Fraunhofer LBF first selected suitable sensors, which they contacted prior to the manufacturing process and then integrated in the liquid phase. In this way, the sensors were able to provide data from inside the friction lining, which were determined during extensive brake tests.
Even the pre-tests showed how sensitive the integrated sensors were to external loads and pressure changes. By integrating several sensors in one brake pad, the team was also able to identify conditions of unequal pressure distribution in the brake pad. By measuring the vibration characteristics of the sensors in conjunction with the friction lining, the experts were also able to make statements about the layer thickness of the friction lining. "This will enable the evaluation algorithm used to assess the wear condition of the friction linings in the future and detect damage caused by changes in the stiffness of the friction layer. In the long term, we see the possibility of teaching self-optimising brake systems with such information," explains Jonas Martin Brandt, who is in charge of the project at Fraunhofer LBF.
In tests on a brake test stand, the researchers exposed the sensors in the brake pads to the loads and temperatures typical for real-world braking processes. The interactions of different brake pressures with the brake hydraulics were analysed, so that the experts were able to determine the optimum force application for the different pressure ranges. In future, the researchers hope that the embedded sensors will enable conclusions to be drawn beyond the actual brake pad