Metal cocktail Audi A8

The body of the next generation Audi Space Frame (ASF) A8 is a multi-piece structure using aluminum, steel, magnesium and carbon fiber. This combination of materials also requires different joining methods. The A8 uses 14 of them, from welding to bonding to sheet metal.

Hot rolled steel parts form the structure of the passenger compartment, including the lower front wall sections, side sills, pillars and the front roof arch area. Some of the metal plates are suitably rolled to achieve the desired thickness. This reduces weight and increases strength, especially in critical areas.

Aluminum components account for the largest proportion of the new Audi A8. Cast units, extruded sections and sheets represent up to 58 percent of the volume. In addition, the materials have progressed under the pressure of competition. New heat treated cast alloys with the highest tensile hardness retain strength at over 230 MPa. The corresponding tensile yield strength is more than 180 MPa, and in the case of profiles made of alloy, 280, or even more than 320 MPa.

The intelligent composition of materials also includes magnesium impact parts. Compared to the previous model, they are 28 percent lighter. Aluminum screws unite the elements, thus ensuring high body rigidity. In the event of a frontal collision, the generated forces are distributed across three impact buffers from the front of the vehicle.

The new, deformation-resistant CFRP rear wall is the largest component in the passenger compartment of the new Audi A8. The individual fiber layers consist of 50 mm wide strips that can be positioned at any fiber direction, cut and combined into a finished package. An innovative, specially developed method of direct bonding of individual layers eliminates the need for an intermediate stage. Full sheet production is possible with a completely new epoxy impregnation method.

In addition, Audi has developed and is using the remote laser welding method. Precise positioning of the laser beam in relation to the seal lip reduces the risk of temperature cracks in the manufacturing process.