We got a preview of the 2018 Audi A8
We got an exclusive sneak preview of the architecture underpinning the all-new (D5 generation) Audi A8 that will be revealed in July. Rather than fixating on an ‘aluminium-intensive’ formula, as touted by some manufacturers in their bid to shed kilos from their cars, Audi has adopted a multi-material approach to the make-up of the next-gen flagship sedan.
The D5 A8’s core architecture is – not surprisingly – billed as the most advanced Audi platform to date, upping torsional stiffness by 24% over the outgoing model, and it’s been conceived to snare a five-star rating in EuroNCAP crash tests, as well as being future-proofed for autonomous driving tech and the myriad of combustion and plug-in hybrid powertrains destined for the new car.
Somewhat controversially – as it’s believed to have caused some consternation within the VW Group – the all-new A8 is built on an evolution of Audi’s decade-old MLB platform (MLB Evo, duh!), rather than the cutting-edge, Porsche-developed MSB toolkit conceived not only for the latest Panamera, but also other premium VW Group offerings such as the next-gen Bentley Continental GT and Flying Spur.
For what it’s worth, the D5 A8’s architecture is a high-tech showcase of composite construction that features a mix of aluminium, magnesium, carbonfibre-reinforced polymer (CFRP) and conventional and hot-formed steel.
Although claimed to be stronger and more weight-efficient than its predecessor, the new body-in-white is actually heavier than the oldie at 282 kg (versus 236 kg). This is the result of not only satisfying more stringent crash-protection criteria, but also the need to house a full-length panoramic sunroof (necessitating added strengthening to prevent chassis flex) and accommodate autonomous driving tech, plug-in hybrid powertrains (with their heavy and potentially volatile lithium-ion battery packs) and 48-volt electrics with a raft of sensors and high-resolution cameras.
One of the key elements of the new structure is an ultra-high-strength, torsionally rigid CFRP (carbonfibre-reinforced plastic) panel that forms the rear of the passenger cell. This panel is the largest component in the occupant cell of the new Audi A8, and it allegedly contributes 33% to the torsional rigidity of the total vehicle.
Building a composite structure presents great challenges from an engineering perspective, according to A8 project manager Dr Ulrich Widmann. “As soon as you introduce more materials to the mix, you get more complex joining requirements. There’s the need for lots of tools and processes.”
Widmann says another factor to overcome was the problem of “galvanic corrosion”, which is an accelerated corrosion process that occurs when mixed materials are fitted together. And given that 90% of insurance claims are for prangs that occur at speeds of 10 kph or less, the A8’s design also needed to incorporate bolt-on structures at the front and rear to ensure accident-repair costs wouldn’t be stratospheric.
Although the majority of the A8’s skeleton is fabricated from aluminium sheets, castings and box sections, the bits that need to absorb high-impact energy in a severe crash are steel. These include some sections of the car’s frontal structure, the A- and B-pillars, part of the roofline, sidesills and front corners of the passenger floorpan (to prevent the wheel from coming through and pulverising your feet in a front offset collision).
Some of these sheet metal blanks are produced in varying thicknesses using “tailoring” technologies and others also undergo partial heat treatment. Widmann says this reduces weight and increases the strength, especially in areas of the vehicle that are particularly critical for safety.
Rounding out the “intelligent” mix of materials is the magnesium strut brace that sits just in front of the firewall. This is claimed to be 29% lighter than the aluminium brace used in the outgoing A8.
The accompanying images of the new skeleton indicate the next-gen A8 won’t be a me-too version of its smaller siblings from a visual perspective, with much bolder styling inspired by the rakish 2014 Prologue coupe concept. The biggest design departure appears to be at the rear, with angular taillights sitting below a sharp crease that runs the length of the shoulder line. This crease was a complex feature to incorporate into the aluminium pressing, says Widmann.
Although Audi has for now released little in the way of stats, we do know that rear-seat occupants will have an additional 14mm of headroom and 28mm of kneeroom, which will greatly assist the A8’s cause against the accomplished Mercedes S-Class and latest-gen BMW 7 Series, particularly in the chauffeur-drive segment.
The new A8 will also reportedly feature ‘Level 3’ autonomous driving tech, which means the vehicle will be able to handle most “safety critical functions” and allow the driver to take their hands off the wheel for short periods in certain conditions.
Other surprise-and-delight features will include a sophisticated Matrix OLED (Organic LED) lighting package, plus the electromechanical Active Roll Control and electric turbocharging tech (in some powertrains) that features in the latest Audi SQ7.
Interestingly, it seems Audi first toyed with the idea of an all-aluminium structure back in 1987 with an Audi V8 aluminium concept, but it was only in 2002 that the first Audi A8 was built out of aluminium.
Photos by Audi.