Lightweight Design

New active and passive safety features all add to the weight of the vehicle. Often, however, we can offset this by using lightweight materials and components. Materials that can be used to shed weight include not only aluminium but also plastics and extremely high-tensile steels. Life cycle assessments demonstrate that the normally greater initial cost of these innovative materials is justified by the longer-term ecological and cost benefits. Often, the cost of the weight reduction is neutralised after only a few tens of thousands of kilometres.

Innovative lightweight design from Audi
Audi is a pioneer and technology leader in the field of aluminium-based lightweight design. The company's aluminium spaceframe technology first went into production in 1994. In the meantime, aluminium is by no means the only lightweight material Audi is using. For example, it is also expanding the use of fibre-reinforced composites, thereby making the bodyshell approximately 43 percent lighter than a conventional steel construction. Audi engineers have also developed a ground-breaking technique for the thermal joining of steel and aluminium during the production process, allowing the two materials to be joined with soldered connections. Aluminium and steel panels can now be placed side by side.

Light and also much safer
In the case of all-steel bodies too, the products of the Volkswagen Group are steadily working off the pounds, thanks to use of high- and ultra-high-tensile steel. In the new Volkswagen Passat, these types of steel already account for 82 percent of all steel used, ensuring that despite additional safety features, the body structure is no heavier than that of the previous model.

Optimised ecology and costs
In developing the Passat B6, we established that the cost of a lightweight design solution can be a price worth paying. The necessary information was supplied by a life cycle assessment. We compared the additional costs of producing body components using a resource-intensive shape-hardening process with the fuel savings generated by the resulting weight reduction. It emerged that although the shape-hardening process is considerably more energy-intensive than the conventional process, resulting in additional emissions of approximately 22 kg of CO2 equivalent per vehicle, the greater strength of the components produced by this method, and the fact that less steel is therefore required, means that the weight of the body can be reduced by about 20 kg – thus making the vehicle more fuel-efficient. The savings on every Passat B6 work out at an average of 174 kg of CO2 equivalent per vehicle. If 2.3 million Passat B6 models are sold over the production life cycle, the total saving would therefore be 0.4 million metric tons of CO2 equivalent. This is equal to the annual CO2 emissions of a town of approximately 32,000 people.