Tribological studies of low wear CMC friction pairings compared to a standard friction pairing
OPEL T. 1, LANGHOF N. 1, KRENKEL W. 1, SCHAFFÖNER S. 1
1 Chair of Ceramic Materials Engineering, University of Bayreuth, Bayreuth, Germany
The environmental impact of the braking systems of different vehicles has become a topic of interest for the general public. With Euro 6 emission limits the particulate matter emissions of standard brake systems are comparable to the particle matter emissions of internal combustion engines, which further expedites the public attention. Therefore, the reduction of the particle matter emissions of brake systems is vital. Consequently, full ceramic friction pairings are promising candidates for future brake systems because of their outstanding wear behaviour.
Three different brake pads were tested on two different brake discs (carbon ceramic, metal-ceramic hybrid). A LowMet brake pad was used as a benchmark, state of the art brake pad material. Furthermore, a short fibre reinforced C/SiC brake pad, which was modified with petrol coke and SiC powder and manufactured using the liquid silicon infiltration process as well as a fabric reinforced C/C brake pad manufactured using chemical vapour infiltration were tribologically tested.
The tribological tests were conducted on the University of Bayreuth’s dynamometer using an adapted Auto-Motor-Sport-test. All friction pairings were characterised using 10 consecutive stop brakings (each ≈ 0.5 MJ) with a starting sliding velocity of 20 m/s at three different braking pressures (1; 2; 3 MPa). The corresponding friction coefficients were recorded as well as the wear rates of the brake pads. For a deeper understanding of the measured tribological characteristics and wear mechanisms of the friction pairings, the resulting friction surfaces of the brake pads were analysed using secondary electron microscopy.