High-tech pistons and ultra-high-strength CFRP technology
Stuttgart/Munich Mercedes-Benz innovations received two of the coveted “MATERIALICA Design and Technology Awards” judged by a panel of experts. The newly steel pistons, developed for passenger-car diesel engines, impressed in the category focused on the potential for reducing CO2 and delivering high performance. The ultra-high-strength CFRP struts also won an award in its respective category focused innovative material usage. The CFRP struts can now be produced cost-effectively in larger volumes for the first time, thus opening up new possibilities in the field of lightweight construction. These awards underscore the leading role Mercedes-Benz Research and Development plays in terms of material innovations.
Steel pistons for passenger-car diesel engines
2 to 4 percent lower fuel consumption and CO2 emissions – an impressive overall performance from Mercedes-Benz passenger-car diesel engines which are the first engines worldwide being equipped with innovative steel pistons in conjunction with a lightweight aluminium cylinder case. The reduction in fuel consumption is even more pronounced at lower and mid-range engine speeds. These ranges play an important part in everyday driving. Mercedes-Benz received a MATERIALICA “Best of Award” for the innovative steel pistons in the category “CO2 Efficiency.”
At first glance, the combination of aluminium cylinders and steel pistons seems problematic: steel expands less than aluminium when heated; it conducts heat worse and is heavier than aluminium. These are the reasons why aluminium pistons have been used to date. Yet the Stuttgart MB engine designers have succeeded in turning these apparent disadvantages into advantages. For example, the lower expansion of steel as operating temperatures rise ensures increasing clearance between piston and aluminium housing. This reduces friction by 40 to 50 percent. At the same time, the fact that steel is stronger than aluminium allows very compact, lightweight pistons that even offer additional strength reserves. Finally, the lower thermal conductivity of steel leads to increased component temperatures, thus improving the thermodynamic efficiency with higher ignition performance and reduced burn time.
High-strength CFRP struts: extremely lightweight construction designed for mass production
All vehicle designers aim to produce a vehicle body that is as stiff as possible, since having a stiff body shell as a basis allows dynamic handling and also helps to minimise vibrations and noise. Fibre composites, particularly those that include carbon fibres, are ideal for ensuring maximum stiffness with minimum weight. Until now high costs have prevented their widespread use in vehicles.
However, a Mercedes-Benz innovation has changed all this. This innovation allows automatic, low-waste and therefore, cost-effective production of ultra-stiff and extremely light CFRP struts, making mass production possible. Mercedes-Benz received a MATERIALICA “Gold Awards” for this innovation in the category “Material.”
The core of this innovation is the combination of several components: carbon-fibre layers provide maximum stiffness and additional outer layers, applied at different angles ensure high pressure resistance. A third component, which was developed by Mercedes-Benz; are the innovative force elements which transfer all loads safely to the CFRP-struts.
The results are extremely lightweight struts that are up to 70 percent lighter than standard steel struts. The lighter weight also helps to reduce fuel consumption. The CO2 break-even point (i.e. the distance the more fuel-efficient vehicle has to travel before the increased amount of CO2 used to produce the carbo-fibre components is saved) is only approximately 50,000 kilometres. Furthermore, this Mercedes-Benz innovation allows a production process for more than 300,000 vehicles per year.
The award ceremony took place during the MATERIALICA trade fair, 21 – 23, October 2014, in Munich, Germany. MATERIALICA is an international trade fair for material applications, surfaces and product developments. The MATERIALICA Design + Technology Award focuses on product and technological developments in all sectors which implement a successful bundling of competencies.