The European Union has set a standard that emissions may not exceed an average of 130 grams CO2 per kilometre. This corresponds to the consumption of approximately 4,5 litres of fuel per 100km. One way to achieve this goal is weight reduction. Today, the frame of a car is made almost entirely of steel, which is very solid but relatively heavy. The current plan is to replace the steel with lighter materials and integrate them into mass-produced cars.
Dr. Michael Goede, Volkswagen, was coordinator of the European funded project SuperLightCar. Engineers from 38 European partners succeeded in building a C-class body with lighter materials that consists of steel, aluminium, magnesium and carbon fibre reinforced plastics. This way the engineers achieved a weight reduction of 35%, or 100 kilograms. This lowered the CO2 emissions by 8.5 grams per kilometre. But the effect on fuel consumption is relatively low: only up to 0,5 litres are saved per 100 km.
During the last four years scientists and engineers have developed a new body apparently achieving a weight reduction by 100 kilograms. But was it worth it?
Lightweight design is a key issue for us to reduce CO2 emissions. A 100kg weight reduction corresponds to savings of 0,4 or 0,5 litres of fuel. A weight reduction of 5 to 10 percent does not seem too significant, but it is still an important step for the European car industry. Additionally, less weight has advantages for the propulsion system and driving dynamics.
One of the challenges was that the new materials should not compromise the safety and performance of the car. Have you managed to reach these targets?
For all car manufacturers, the performance in crash tests is a crucial issue for the quality of the vehicle. While all cars for the mass market are tested extensively in crash tests, the body of the Super Light Car was examined with crash test software. Using virtual crash tests the new design was examined in detail, to ensure that the safety of the vehicle would not be compromised. Realizing light construction for auto bodies always includes keeping the passive safety requirements during a crash at the same level or even improve them. This has been done at the SLC body. It fulfils the same crash requirements as a steel body but weighs 100kg less.
The body of the Super Light Car consists of steel, aluminium, magnesium and carbon enforced plastics. Magnesium is significantly lighter than steel. An element produced from Magnesium weighs 75 percent less than produced from steel, and still 33 percent less than an aluminium element. Magnesium has the disadvantage of corrosion. This is a problem…
When car manufacturers will use the SLC body to market their own car, they will probably concentrate on combining only aluminium, steel and some single elements of carbon enforced plastics. For the SLC, we used 100 metres of bond seams, every time we had to connect two different raw materials but also in the area of the roof where we joined steel with magnesium and aluminium. And of course also at the rear where the plastics are implemented. Gluing is always combined with mechanical join connections to additionally fix it in a mechanical way with rivets and screws.
When will the Super Light Car enter mass production?
Unfortunately this prototype will never make it to the mass production. It is simply too expensive. But the study will help car manufactures learn how they can reduce weight in such a way that it also makes economic sense. The construction of this body was a first important step. The SLC body concept for the first time shows an intelligent composite construction for mass production of compact cars. Replacing steel with aluminium, plastics and magnesium.
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