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Multi-material design of the A8

Lightweight Construction Succeeds with Material Mix

| Author / Editor: Svenja Gelowicz / Alexander Stark

Frank Venier from the Audi Lightweight Construction Centre started this year's "Automobil Industrie" Lightweight Summit with a keynote speech on the multi-material design of the new A8 and the fourth generation of the "Audi Space Frame".

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The Audi A8 is the ultimate example of a successful lightweight concept in a premium car.
( Bild: AUDI AG )

Lightweight construction for tomorrow's mobility: With a keynote on OEM strategies and the example of the flagship Audi A8 project, the starting signal for the seventh "Automotive Industry" lightweight construction summit was given on March 13. The specialist Frank Venier from the Audi Lightweight Construction Centre spoke to almost 230 participants about the lightweight construction technologies used in the flagship A8.

The lightweight construction specialist Frank Venier from the Audi Lightweight Design Centre spoke to around 230 participants about lightweight construction technologies used in the flagship A8.
The lightweight construction specialist Frank Venier from the Audi Lightweight Design Centre spoke to around 230 participants about lightweight construction technologies used in the flagship A8.
( Source: Stefan Bausewein )

For the electrification of the powertrain, the VW subsidiary is focusing on weight reduction. "It is not sufficient to restrict our efforts on extending the range," says Venier at the beginning. The result should always be an overall system in which points such as tire load ratings and driving license categories are considered.

The well-known slogan "The right material in the right place", coined by Audi's head of Lightweight Construction Heinrich Timm, still applies to future e-architectures. "Achieving the goal of economical lightweight construction is just as important," says Frank Venier. According to Venier, Audi now uses a complete range of materials. But why did Audi switch from the aluminium body to the multi-material mix; and what components has the company optimized in the new A8?

The Fourth Generation of the Audi Space Frame

Today, more than one million Audi models are based on the Audi Space Frame (ASF) design principle. The ASF, a framework consisting of aluminium components, extruded profiles, castings and aluminium sheets, is now produced in its fourth generation — its internal designation is D5. For the latest generation, for example, the AFS has also been equipped with steel parts.

Venier explains this move above all with stricter requirements of the market and regulatory authorities, especially with regard to crash behavior and electrification. But these are not the only new demands: The internal requirements of Audi are also increasing, for instance in the premium segment where maximum security plays an important role.

Audi relies on three systems to ensure the highest possible degree of crash safety:

  • Multi-material mix
  • Lightweight construction
  • Active system

Only the combination of lightweight material construction and lightweight design ensure that forces are deflected properly and can guarantee the desired crash behaviour. This combination is complemented by a "Predictive Safety Crash Side Assistance" system. If required, the active chassis can raise the vehicle slightly in the event of a crash. This improves the positive effects of the structures in the area of the rockers and the B-pillar. These three construction elements significantly improve the crash behaviour.

Audi's Material Toolbox

The Audi A8 consists of 29 different materials, including steel, extruded aluminium profiles, die-cast aluminium parts, sheet metal components and forged parts — for the first time in the A8 the magnesium strut brace was installed. Venier is also proud of the carbon fibre-reinforced rear wall: Compared to its predecessor, this CFRP rear wall reduces the weight by 50 % — whilst improving functionality, the lightweight construction expert from Audi said.

Lightweight Construction

Will lightweight construction be neglected in view of the megatrends of electric mobility, connectivity and automated driving? On the contrary: the new disciplines are even giving new impetus to lightweight construction. This is because they add to the existing demands placed on vehicle architecture, which can only be met with lightweight construction measures, for example to meet load limits.

This article was first published by Automobil Industrie

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