Another factor is the addition of protective measures relating to the hybrid powertrains. “Once you add a lithium battery to a car you have to think about how to protect it in the event of a crash,” said Dr Bernd Mlekusch, chief body engineer.
The Audi A8 is expected to be equipped with a 48-volt electrical system and the body has been engineered for full hybrid systems, something which requires further protection from the body structure. “We have taken into account the possibility of a PHEV version of the A8 as well,” said a spokesman.” The extra weight is unlikely to be due to the new model growing in size. “It won’t be significantly larger” than the outgoing model, said the spokesman.
The rear bulkhead and parcel-shelf is made of carbon fibre using a new process developed by Audi and its suppliers weighing just 2.6kg. The bulkhead is made using carbon fibre tape laid up in different directions by machine, impregnated with resin and cured in just five minutes. The panel accounts for only one percent of the total body weight but accounts for 33 percent of the overall stiffness.
The aluminium components take the form of castings, extrusions and sheet. The body also incorporates high-strength steel components and a magnesium cross-brace is used at the front of the car to further increase stiffness.
A number of new manufacturing techniques have slimmed down the B-Pillar and structures around the glass areas creating more comfortable entry and exit for rear-seat passengers and improved vision. New techniques also include remote laser welding which is 53 percent faster than the previous laser welding process, uses 50 percent less heat and produces 25 percent less CO2.
The structure of the new A8 examined
1. Carbon fibre panel punches above its weight
The new A8 incorporates carbon fibre for the first time, in the rear panel and parcel shelf. Although it accounts for just one percent of the materials total, it adds a whopping 33 percent to the total stiffness.
The panel weighs 50 percent less than an aluminium equivalent at 2.6kg and braces the structure horizontally and vertically. Using a new process developed by Audi, traditional sheet carbon fibre is replaced by 50mm wide lengths of carbon fibre ribbon laid by machine on top of one another at 360 degrees around the points of the compass. The process is much faster than traditional labour intensive carbon fibre manufacturing, as is the RTM (resin transfer moulding) process which takes only five minutes.