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Audi to present hybrid body materials

News International-French

12 Mar 2012

Major breakthroughs mostly begin in a small way. At first glance, the exhibits presented by Benjamin Bender seem to have nothing spectacular about them: narrow strips of aluminum with a thin layer of carbon-fiber reinforced plastic (CFRP) on the back.

In fact this advanced development project, which postgraduate Bender is undertaking in the Audi Lightweight Design Center (ALZ) at the Neckarsulm plant, has great future potential. At a later date, when the new hybrid metal and CFRP structures go into series production, they will represent another step forward in ultra-lightweight construction at Audi.



The Audi brand became a leader in lightweight vehicle construction some years ago with its aluminum bodies. Using the ASF (Audi Space Frame) construction principle on the Audi A8, Audi R8 and Audi TT models reduced the weight of their bodies by as much as 40 percent compared with conventional steel structures. Now Audi is launching the next stage in the process: the Multimaterial Space Frame, which combines aluminum, steel and fiber-reinforced components.



Audi engineers have in-depth competency in working with all these materials. They are not forced to work with a single material; instead, their motto is ‘the right material in the right place for outstanding performance’.
The new bodies, by combining the advantages of the various materials, will be much lighter than conventional metal structures.



Benjamin Bender’s project takes the multimaterial concept a step further, by making the individual components into ‘hybrids’. If a metal element in the body structure – a B-post or a sill – is systematically reinforced with CFRP, its properties are enhanced, for instance its strength or its deformation behavior in a crash. Yet at the same time it weighs less, because the comparatively heavy metal – steel or aluminum – has been partly replaced by much lighter CFRP.



At the Audi Lightweight Design Center in Neckarsulm about 180 specialists work on the future of Audi vehicle bodies. Benjamin Bender has to find answers to a number of questions. How should the metal and CFRP be combined in order to obtain optimal properties in each component? At which points does the reinforcement have its maximum effect? And what do practical tests tell us about the components’ crash performance or resistance to corrosion?



The method used to join the two materials is another central topic. This is normally done with rivets, screws or technical adhesives. The new project adopts a more ingenious approach: the synthetic resin needed to produce a component entirely in CFRP acts here as the connecting medium.



Bender is currently investigating whether RTM (resin transfer molding) can be used to bond the two materials together. The RTM process is suitable for higher production volumes and is one of the key technologies at the Audi Lightweight Design Center.



“Even if development work goes according to plan, it will take several more years,” says Bender, “and we will still need some time before it’s ready for series production.” Audi knows very well that major breakthroughs often take a bit longer – in ultra-lightweight construction too.


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