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The sandwich effect
Monte Carlo Rally: Heading for victory – with 4-wheel drive, 315 hp and 2-liter 4-cylinder engine.

The trend is clear, straightforward and based on a simple formula: 95 by 2021. New cars sold in Europe will only be able to burn a maximum average of 95 grams of CO2 per kilometer by 2021. Right now, leading companies are still about 30 grams short of this target. That means we’ll need many more low-emission drive systems, like electric or hybrid. And, of course, more lightweight construction. Which is where we at thyssenkrupp Steel Europe come in.

Lightweight steels are a boom market in today’s car industry. Experts predict that market volumes could grow five times as large by 2025. Until now, aluminum and carbon fiber-reinforced plastic (CFRP) have looked like the most likely future alternatives to the number one construction material for decades, namely steel. It’s true both materials are considerably lighter than steel, but their energy-intensive production also makes them disproportionately expensive.

litecor® is the product of intensive, early predevelopment with carmakers.

Oliver Kleinschmidt, Product Coordination, Steel Sandwich Materials

Reducing vehicle weight by more than 30 kilograms

The ‘third way’ consists of the intelligent combination of various construction materials. To be more precise: steel and plastic. litecor® is Steel Europe’s answer – and the chances that this hybrid material will persuade many manufacturers are looking good.“This new material is a sandwich,” explains Oliver Kleinschmidt, as product coordinator responsible for steel sandwich materials in the steel division.

The principle? A polymer core (0.3–1.0 mm thick) is layered between two steel face sheets (each 0.2–0.3 mm thick). The result? litecor® is considerably lighter than conventional sheet steel, easy to recycle and displays good bending stiffness and dent resistance. And not least: very easy to process.

The layers of the steel sandwich don’t come apart, even when subjected to complex forming operations. Producing hems and flanges, adding smooth design lines, mechanical joining or adhesive bonding – all are equally possible. “We are working hard to develop the spot-welding capability of litecor® with our colleagues from thyssenkrupp System Engineering from the Business Area Components Technology. It already works in the lab,” says Professor Hans Ferkel, Head of Technology and Innovation at the steel manufacturer.

Motor hood for the World Rally champion

Where litecor® is concerned, the pilot project with R&D partner Volkswagen shows how profitable early cooperation can be for both sides. Engineers from both companies jointly developed a front hood using the innovative construction material for the road version of the Polo R WRC, the car with which Volkswagen won the 2013 World Rally Championship at its first attempt. They were able to reduce the weight by almost two kilograms compared with the production engine hood. A limited quantity of litecor® was then produced for the special series at the Dortmund pilot facility for 2,500 front hoods.

It’s already clear that this modern sandwich material is ideally suited for lightweight construction of large body components demanding a high degree of rigidity, such as roof, door, tailgate and engine hood, and equally for interior parts such as the rear rack or vehicle floor. If construction of all these parts were switched to litecor®, thyssenkrupp Steel Europe experts calculate that it would be possible to reduce vehicle weight by more than 30 kilograms. And that’s with considerably lower additional costs (compared with steel) than in the case of aluminum.

We take customers’ interests into account, even in the early stages of product development.

Erik Hilfrich, team leader in Application Concepts
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