Over the last decade or two, manufacturers have started to work on lightening their cars despite the overall increase in size and complexity. This is no easy feat, especially when trying to avoid the use of especially exotic materials (a carbon tub like the kind in a McLaren would make life a lot easier). Both BMW and Audi have taken great steps towards shedding weight, with Audi adopting the use of new platforms and their Audi Space Frame technology, while BMW is rolling out their CLAR platform with the carbon core backbone being especially useful for the 7 Series. What you see above is the latest generation of the Audi Space Frame, which will see use in the upcoming all-new Audi A8.
This latest iteration of the Audi Space Frame sees a mix of four different materials at work in the weight-bearing body structure- more than any Audi model ever before. Aluminium, steel, magnesium, and carbon-fibre reinforced polymer come together to create a structure that is both lighter than its predecessor and stronger as well. In terms of quantifiable metrics, the improvement is roughly 25% over the outgoing version of the Audi Space Frame.
One of the critical breakthroughs to develop this new space frame was the production of carbon-fibre reinforced polymer tape rolls which can be layered and angled in various directions with minimal need for trimming. Using this is far easier and more cost effective than the previous method of using a singular fabricated sheet, and the entire layered package is held together with epoxide resin.
As for the rest of the materials, it's fairly standard fair: hot-formed steel make up the occupant cell , taking up the lower section of the bulkhead and the side sills, as well as the B-pillars and the front edge of the roofline. Heat treatment and varying metal thicknesses help to reduce the overall weight of the frame as well, with extremely light aluminium body panels making up the remaining 58% of the bodywork.
In order to build the new A8, there had to be an entirely new body shop created that could provide 14 different joining processes, including remote laser welding. All of these processes and their refinement in this latest form are what has led to the new A8 being so much lighter and stronger than the models that came before. Both costs and CO2 emissions go down as a reuslt of these improvements.