Browse Publications Technical Papers 2009-01-3010
2009-10-11

Tribological Aspects of Carbon Ceramic and Cast-Iron Brake Rotors with Organic Pad Materials in Simulation and Measurement 2009-01-3010

Over the last two decades, intensive research in the field of innovative brake rotor materials for high performance vehicles has been done. Due to the market demand for lightweight components with high strength even at elevated temperatures, most new concepts are based on fiber-reinforced materials [1]. The most prominent concept is a silicon carbide matrix material with embedded carbon fibers (C/C-SiC), which penetrated into the market for brake rotors in 2000 [2,3]. Such carbon ceramic brake rotor systems (CKB) have already been made available for a wide range of premium sedans, SUVs and sports cars.
In terms of tribology, these rotors pose new challenges for an understanding of the relevant friction phenomena in the boundary layer, as well as for suitable formulations of brake pad materials. The brake system's macroscopic tribological performance with such pads is determined by a closed-loop interaction between heat, wear and sliding resistance on the micro scale. It leads to a load and time dependent process of growth and destruction of smooth contact plateaus [4], which is a major cause for transient friction phenomena [5]. This equilibrium of flow can be well simulated with modern computer methods that even reproduce cycles of the AK-Master testing procedure [6, 7].
CKB development will require deeper insights into the above mentioned equilibrium of flow and the variables that modulate it. Against this background, this paper contrasts tribology relevant parameters of cast-iron rotors with the ones of modern ceramic rotors and outlines the impact of existent differences on the mechanisms in the friction boundary layer. The considerations are supplemented with latest simulation results by a cellular automaton, as well as with surface topography measurements.

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