Supercar firms focus on carbon-fiber composites
European Plastics News staff
Posted 4 October 2010 10:48 am GMT
European carmakers including Lamborghini, Ferrari, Bentley and McLaren made carbon-fibre composites the standard for high-end “supercars”.
Now those same companies are taking carbon fibre even further, creating new ways to process it that will reduce the amount of time needed to mould the composite, and push it even further into structural parts.
Automobili Lamborghini made its new technology the centrepiece of its Sesto Elemento concept car introduced 30 September at the Paris Motor Show. The company uses carbon fibre for the passenger cell, the front and rear-end structures, suspension components, the interior, all exterior panels, suspension components and the propeller shaft. Even the tailpipe is made from a carbon and glass-ceramic composite.
The new thrust, said Stephan Winkelmann, president and CEO of Lamborghini, is part of an effort to reduce weight significantly, pushing performance even further than its 570-horsepower engine can do on its own.
“The Sesto Elemento shows how the future of the super sports car can look,” Winkelmann said. “Extreme lightweight engineering, combined with extreme performance, results in extreme driving fun.
“It is our abilities in carbon-fibre technology that have facilitated such a forward-thinking concept.”
And Lamborghini is not alone in taking carbon fibre further. During the Society of Plastics Engineers’ 2010 automotive composites conference in Troy on 15 and 16 September, engineers from Lamborghini were joined by engineers from Bentley Motors and McLaren Automotive in talking about new production techniques for carbon fibre.
Bentley has added cobalt to its carbon fibre to make it magnetic and is using magnets to automate the layup process, which speeds production and cuts costs. UK-based McLaren has been focusing on liquid-resin infusion.
BMW of Munich has developed its own carbon-fibre processing technique that it will use on its future Megacity Vehicle electric car.
Lamborghini — which has been working with Boeing engineers at its Advanced Composite Structures Laboratory in the US as well as running its own Advanced Composite Research Center in Lamborghini’s home town of Italy — is focused on advanced compression moulding using short carbon fibers in a low-pressure injection mold, said Paolo Feraboli, director of the structural carbon-fibre research group. Lamborghini also has signed a development agreement for carbon fiber with golf-club maker Callaway Golf to expand the technology further.
The process, which Lamborghini calls “forged composite”, is far faster than traditional hand lay-up prepreg and autoclave processing, he said. That system could produce a maximum of four passenger cells — called a monocoque — per week, which is too slow even for a low-volume producer.
Lamborghini considered vacuum-assisted resin transfer moulding, similar to the process used for yachts and other marine structures, but it had problems with variable thickness on mould lines.
Traditional RTM provided consistent thickness and a controlled shape, but requires an expensive machine and large and expensive tooling, and it would be difficult to achieve large parts like the monocoque and the front and rear structural cells. ( Lamborghini calls these cells the “cofango,” combining the Italian words “cofano” or hood, and “parafango” or fender.)
Using an “RTM light” method with low pressures, vacuum assist and carbon tooling still will require the investment in injection presses — it has more flexibility in tooling than traditional RTM while still speeding up production, Feraboli said.
Lamborghini’s experiment using compression moulding with a carbon-fibre sheet moulded compound produced a structural suspension part that was 30% lighter than an aluminum part, and its three-minute cycle time beat both traditional carbon-fibre and aluminum processing, he said.
While the Sesto Elemento is a technology study car, Winkelmann said it is a clear indication of where Lamborghini will take carbon fibre.
“Systemic lightweight engineering is crucial for future super sports cars,” he said in introducing the car in Paris. “We will apply this technological advantage right across our model range.”
Its high-end competitors will be on the same track.
Bentley, based in Crewe, the UK, has focused on ways to speed the hand layup of carbon-fiber parts, said Antony Dodworth, principal research manager with Bentley Materials Technology.
“We need to automate,” he said. “We cannot afford to continue with prepreg processes as it is.”
The process, called “directed carbon-fiber pre-forming,” adds a very small amount of cobalt to the carbon fibre. The company can then robotically shoot a fine stream of carbon fiber into a magnetized mold at a rate of 6 kilograms per minute.
“The robot can achieve that delivery all day, every day,” he said.
Bentley compared its automated system to a bumper system for a race car that takes a day and a half with hand labour, Dodworth said. Its new process completed the layup in 20 minutes.
The company already has used the process in a structural carbon-fiber spare wheel well on its Mulsanne sedan.
After a longer period of stagnation it is clear that big European players like BMW, VW group and also McLaren are making very serious efforts to automate manufacturing CFC structural and body parts.
