The Mercedes-Benz F 125! research vehicle: Bodyshell concept - Effective lightweight construction with an intelligent material mix
Specific lightweight construction methods will make a considerable contribution to fuel economy in the automobiles of the future. Here too, Mercedes engineers take a comprehensive approach and use every means at their disposal to make vehicles bearing the Mercedes star lighter, and therefore more economical and efficient. Particular attention is paid to the bodyshell, which accounts for a major proportion of the vehicle weight.
Mercedes-Benz is already one of the largest users of aluminium in the automobile industry. However, the inventor of the automobile consciously opts not to rely only one material, but on a flexible, need-related mix of various metals and plastics. Mercedes-Benz expertise in this field is underlined by its large number of patent registrations in the field of production engineering and new materials. 14 percent of all new developments relate to lightweight construction materials and production processes, e.g. the use of CRP, and environmentally compatible manufacturing processes. CRP technology has long been firmly established in many areas of series production. Today Mercedes-Benz uses carbon-fibre reinforced plastics in various products - from buses to the Unimog, and right up to the AMG models.
Composite CRP materials, aluminium and high-strength steel alloys
With a combination of fibre-reinforced plastics (FRP) and a high content of carbon-fibre (CFRP), lightweight metals and high-strength steel alloys, as well as hybrid materials, precisely designed to meet the relevant requirements, the F 125! impressively demonstrates the great variety of possible applications. Thanks to the intensive use of CRP, the lightweight construction specialists at Mercedes-Benz have been able to reduce the bodyshell weight of the research vehicle to around 250 kilograms - roughly 40 percent less than that of a comparable model in current series production.
At the same time the level of safety has again been significantly improved. For example, the self-supporting structure of the gull-wing doors is a monocoque CRP design, with the material applied in four to 16 layers depending on the requirement. In addition this component is equipped with a crash-responsive PRE-SAFE® structure. This large-surface side impact protector is "inflated" by sensor control like an airbag, enhancing the crash performance during a lateral collision. This protection system first presented in the Mercedes-Benz Experimental Safety Vehicle ESF 2009 ensures that the volume in the impact area is enlarged, with a longer deformation path. Energy dissipation is thus improved without any design compromises becoming necessary.
Thanks to concerted lightweight construction, the doors are fitted with no visible gas-pressure struts or visually intrusive hinges with long lever arms. Instead the gull-wing doors are opened and closed with the help of electro hydraulic actuators fully integrated into the roof, and these are assisted by gas-pressure struts which are likewise concealed. The front and rear side members of the F125! are completely of CRP, making roughly five times the energy absorption of a steel construction possible.
Intelligent use of CRP with the focus on safety-related areas
The front flexural and supporting structure is a load-bearing assembly of hybrid CRP sandwich construction. The door entry sills, rear end and pull-out luggage compartment of the F 125! are faced with carbon-fibre. The seat structure is also substantially of CRP, which ensures an extremely low weight and allows integration of the seat belt into the seat.
In the floor assembly – which accommodates the gas reservoir – mainly ultra-high-strength steel alloys and aluminium are used in combination with fibre-reinforced plastics. A bionically optimised metal/plastic hybrid construction is used for the A-pillars. For the front load dissipating path connecting the firewall and the floor assembly in the centre console area, the engineers have used a highly rigid honeycomb sandwich material.
Exemplary entry and seating comfort in a coupé atmosphere
In combination with an extremely long wheelbase of 3333 mm, the doors opening along the entire flank of the car allow extraordinarily convenient access and egress. By way of comparison, the figure for the current long-wheelbase S-Class is 3165 mm. Because the side windows are also fully retractable as a unit, the F 125! not only offers extremely generous interior space, but also the driving pleasure of a classic coupé.
Source: Daimler AG
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