In recent years, there has been a paradigm shift in the automotive industry to phase out the internal combustion engine. This process requires the optimization of every component of the vehicle for alternative drive systems. For instance, the brake systems must be optimized to meet the performance requirements of electrified vehicles – enhanced corrosion resistance, minimized non-exhaust particle emissions and negligible brake noise issues. The braking system of an electric vehicle relies mainly on regenerative braking, which implies that the issues of corrosion and brake noise (any vibration) will become prominent in the usage of friction couples in electric cars. Besides, the new particle emissions regulations signify another hurdle that the Original Equipment Manufacturers (OEMs) must fulfil in the coming years. However, the mentioned issues will become a great deal to contend with by the OEMs whilst conventional friction brakes are still needed for safety reasons but are less used on electric vehicles. This investigation was motivated by the need to find an alternative brake disc material that could satisfy/fulfil the above-highlighted challenges. The study also highlights the prospects of a lightweight SICALight rotor as a potential alternative to the traditional grey cast iron (GCI) brake discs for future car applications with electrified propulsion. Cooperation between the brake disc and brake pad manufacturers was initiated to evaluate the potential of the aluminium rotor with compatible brake pads in meeting the requirements for the electrified vehicle application. The friction couples were investigated by running typical dyno and vehicle tests on a current production rear axle brake application. The focus of this test was to confirm the overall performance of the friction couples in terms of wear, corrosion, non-exhaust emissions, durability & NVH (Noise, Vibration & Harshness). The results indicated a suitable braking performance with fast creation of the tribolayer at a stable level throughout the testing with low brake pads wear and no disc wear, no corrosion issues, reasonable durability and good NVH behaviour. Besides, a significant advantage is seen with lower particle emissions compared to conventional grey cast iron discs with corresponding brake pad material. The friction couples (SICALight rotor and pads) also performed at the same level as the hard-coated GCI brake rotor or even better in terms of particle emissions. With the support of regenerative braking and refined brake rotor design, the low maximum operating temperature of the aluminium rotor can be optimized for the brake application. Apart from this, the friction couples look very promising for application in battery electric vehicles (BEVs) to save weight, resulting in a reduction of unsprung mass and less energy consumption for vehicle motion, eventually converting this into a longer driving range. This study provides more application tests to confirm the suitability of the SICALight disc as an alternative solution for brake systems in electrified vehicles. In summary, the investigation showed that the friction couples (SICA rotor and compatible brake pads) are suitable to replace the traditional brake friction couples for electrified vehicles application in terms of sustainability, durability, particle emissions reduction, corrosion resistance and NVH issues.

Dr. Eng. Samuel Awe, Research Manager, AUTOMOTIVE COMPONENTS FLOBY AB; Mr. Ewald Eilers, Application Engineer, Tenneco Braking; Dr.-Ing. Florian Gulden, Foundation Brake Engineer, AUDI AG