Audi Space Frame in multimaterial mixed construction

Like the previous model, the new R8* also has a body in ASF (Audi Space Frame) construction – which is synonymous with extreme lightweight design. It weighs just 200 kg (440.9 lb), which is ten kilograms (22.0 lb) less than before – thanks to a concept being used at Audi for the first time which combines aluminum and carbon-fiber- reinforced polymer (CFRP). Large components of the occupant cell consist of CFRP, while the front and rear body modules are built exclusively of aluminum. The new multimaterial ASF forms the basis for the lightweight design concept of the high-performance sports car.

In its lightweight design strategy, Audi does not just rely on a single material, but instead on an intelligent material mix – according to the motto “The right material in the right amount at the right place.” The new material CFRP is used where it can attain better results than aluminum. CFRP is used for the rear wall, the center tunnel and the three-part B‑pillars. These large components, which are produced in the efficient resin transfer moulding (RTM) process, form the high-strength backbone of the ASF that is nearly torsion-free. They account for a 13 percent share of the ASF.

CFRP parts differ from one another in their structure, depending on where they are used. Audi fully exploits the material’s specific strengths. In the crossmember of the rear wall, where maximum strength in a transverse direction is what counts, the fiber layers are largely aligned unidirectionally. Up to 14 of them are placed on top of one another to form a five millimeter (0.2 in) thick sheet with very high tensile strength of 3,950 MPa (megapascals). In the B‑pillar reinforcements, on the other hand, the layers are aligned in all directions to support both longitudinal and transverse loads. The tensile strength of these parts is 900 MPa.

The front and rear body modules of the new R8 are constructed entirely of aluminum – from semi-finished goods that include castings, profiles and sheets. The cast nodes, which make up 20.8 percent of the ASF, have complex interior geometries that make them well suited for absorbing large forces while offering plenty of versatility and design freedom. The A‑pillar nodes, for example, join key parts of the front body and the occupant cell to one another. They consist of a new, high-strength alloy with a tensile strength of 350 MPa.

The extruded profiles, together with the cast nodes, form the framework for the front and rear body modules. They have a 47.2 percent material share in the ASF. The profiles too offer a lot of design flexibility. One example is the upright profile between the suspension strut mount and the chassis joint of the rear axle. Over its approximately 60 cm (23.6 in) of length, its wall thickness varies between 1.5 mm (0.1 in) and 6.2 mm (0.2 in), which saves 1.3 kg (2.9 lb) in weight. Audi also took new paths in lightweight design with the structural struts that stiffen the rear body – oval aluminum profiles that weigh just one kilogram (2.2 lb) form the upper structure.

Along with this optimization of topologies, ASF developers also performed a new type of functional integration. Cast nodes from the new, high-strength alloy join the control arms directly and rigidly to the ASF. The floor of the luggage compartment is made of sheet aluminum, and it serves as a shear area that improves crash properties.

Made entirely of aluminum: the exterior skin
The outer skin of the new Audi R8, including doors and lids, is produced entirely of aluminum. Alloy sheets make up an 11.2 percent share of the ASF and are primarily used for the floor of the occupant cell and its bulkhead. A 0.6 percent share is steel, 0.5 percent other materials and 6.7 percent fasteners.

In the ASF of the new Audi R8, the combined length of the welds between the aluminum components is a full 89 meters (292.0 ft). The aluminum and CFRP are joined exclusively by cold methods – the ASF contains 270 semi-hollow punch rivets, 207 blind rivets, 241 metric screws and 270 self-tapping screws. Cathodic dip coating, an engineered adhesive and a special seal ensure that the metal alloy does not corrode in contact areas with the CFRP.

Compared to the previous model, the ASF of the new Audi R8 has been significantly improved in all criteria. It has gained 40 percent in static torsional rigidity – which makes it an excellent material for ensuring precise handling, high crash safety and acoustically quiet vibration behavior. The new multimaterial ASF attains a top figure in the sports car segment for its lightweight index – a measure of the relationship between weight, size and stiffness. If Audi had built it in the previous aluminum technology, the ASF would have been 32 kg (70.5 lb) heavier.

The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.