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Lightening the atmosphere with low-weight cars

Most people understand that a heavy car is a slow car, but weight also increases an automobile’s burden on the environment. In order to meet Europe’s Kyoto commitments, car manufacturers are looking at a number of technologies for reducing vehicle weight. A recent workshop looked into EU-backed projects that will lighten the load on the atmosphere while maintaining stringent safety standards.

Light-weight body parts;  Image: 3D STRUCTURES
Light-weight body parts;
Image: 3D STRUCTURES

Concern over the environmental impact of fossil fuels has galvanised the international community into taking action to minimise emissions. Although criticised by some environmentalists as not going far enough, the Kyoto Protocol is the most ambitious international treaty tackling this thorny problem.

Traffic emissions are a major source of human-produced CO2 in the atmosphere, and the amount of exhaust fumes produced by a vehicle depends largely on its weight. While increasingly stringent safety measures are making cars heavier, innovative technologies and new lightweight materials offer the prospect of trimming back the flab.

Recognising the potential of weight loss, the European Union has, since 1994, been backing research into ways of making cars lighter while improving their safety performance. Under its Fourth, Fifth and now Sixth Framework Programmes, it has funded and continues to fund dozens of projects in this vital area.

A recent workshop in Turin, Italy showcased a number of European Commission-funded projects that aim to help the automotive industry to produce lighter cars. The nearly 30 different projects presented at the conference focused on incorporating state-of-the-art lightweight materials and new production technologies, particularly in the areas of forming and machining.

Car-lite – material change

Car bodies are currently produced out of a single material – either aluminium or steel. These ‘unibody’ automobiles will have to give way to vehicles made of an optimal mixture of the most efficient and compatible materials. Some EU-backed projects are looking into incorporating aluminium alloys and magnesium into car structures. Others are exploring the potential of so-called sandwich and composite structures that mix plastics with metal or carbon fibres.

But new materials are not the only way to make cars lighter. More efficient manufacturing processes can help produce components that give the same performance at lighter weights. New production technologies include hydro- or electromagnetic forming, which aim to bundle more components into a single, complex shape.

And new processes

The Fiat-led ‘3D-STRUCTURES’ project was aimed at reducing vehicle weight and increasing safety through the development of an innovative ‘double-sheets hydroforming’ process, whereby water is injected at high pressure between two sheet metal blanks. This allows the formation of complex components that are lighter and more structurally sound.

3D-STRUCTURES has also developed an innovative body side concept, resulting in a successful door ring structure demonstrator. Altogether, the project has shown a potential weight reduction of up to 10% when using high strength steel and up to 30% if aluminium alloys are used.

Meanwhile, the HYDROSHEET project is working towards developing new hydroforming techniques to form high-strength steel and aluminium into complex novel car components, while HYDROTUBE is developing processes to bend and pre-form tubular components – particularly thin-walled ones – for body and chassis applications. HYDROTUBE has already borne fruit in the shape of demonstrator prototypes for the frame above the windshield and a pillar and the development of a new process known as Kinematic Bending. Both HYDROSHEET and HYDROTUBE are being led by Volvo.

Bringing lighter cars to market

Although individual EU-backed project could slash the weight of individual components by up to half, the overall impact on total vehicle weight is far from clear. This will depend on the particular mix of materials and processes chosen by individual car manufacturers.

This highlights a new focus for future research that the EU is beginning to address: optimal joining technologies for different materials that could be suitable for mass production. The Commission has launched a call for proposals for an Integrated Project that will allow the industry to assess and integrate the technologies developed in past projects.

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