MATERIALS:The use of carbon fibre in the mass production of cars could revolutionise the industry and help to make electric cars more affordable for all
MARIO STANDS IN front of us, bent over his work. He’s delicately trimming a black material with nothing more sophisticated than a sharp knife. The location is Lamborghini’s factory in Sant’Agata in Italy; the material is carbon fibre; the year is 2011.
Take a step back 30 years and the scene would have been little different. In 1981 McLaren introduced the MP4/1 Formula One car, featuring a carbon fibre reinforced plastic monocoque for the first time. (Monocoque means single shell in French. It is a construction technique that uses the external skin to support some or most of the load.) John Barnard was the designer of that car.
“It came about because of the need to make space in the chassis for the ground effect tunnels. The thinner the material we could use, the more effective these would be,” he says.
Carbon fibre reinforced plastic (CFRP), commonly referred to simply as carbon fibre had been used sporadically in motorsport before that, but never structurally, and at first Barnard and McLaren were told by the tiny carbon fibre industry that existed at the time that they were too ambitious in their plans to make a whole chassis out of this unknown material.
Eventually Hercules, an American aerospace company, expressed interest in the project and it built the race car tubs (the protective shells that surround the driver) to begin with.
In those days, detailed finite element analysis (FEA) took months to complete, so the designers had to err on the side of caution when constructing a chassis. Even so, the first one made was nearly three times as stiff as an aluminium equivalent. Barnard realised that they were on to something.
Despite that, scepticism remained in Formula One, mainly because of how the material had been used until then. Previous crashes had resulted in the carbon fibre components shattering, virtually into dust. However, Barnard points out that there was little understanding of how to use carbon fibre and his approach was completely new.
John Watson, McLaren’s number one driver of the time, proved the sceptics wrong when he crashed the MP4/1 heavily in Monza: “I felt a big bang and saw an engine lying on the road in front of me. Only when I got out of the car did I realise it was mine.”
He walked away unscathed and though most components were torn from it, the carbon fibre tub was completely intact – and still usable. It took the rest of the Formula One field only a few years to switch over completely to the same construction.
Barnard stumbled upon carbon fibre in a bid to win races, but it has since been acknowledged that it is an important material for the future. Its strength-to-weight ratio is unsurpassed as yet. The aerospace industry is at the forefront of its development: the newest commercial airliners are made of 40 per cent carbon fibre. It’s also becoming increasingly common in sports such as golf and fishing.
As with the aviation industry, carmakers are focused on reducing fuel consumption, emissions and pollutants. At the same time, however, consumers are demanding more from each generation of car, necessitating the inclusion of extra equipment and more safety. This all adds weight.
As battery technology is still in its infancy, electric cars in particular have an inherent weight problem. Reducing this weight is of major importance for efficiency and driving dynamics, so interest in carbon fibre is higher than ever.
Yet, it’s still seen as a young, expensive material. The figures speak for themselves. Global automotive production is about 60 million cars per year. Just 500 of those are considered to be supercars. Although nearly all supercars made since the McLaren F1 of 1991 use carbon fibre construction, only 10,000 have been produced in the past 20 years.
The new MP4-12C sits below the supercar class, according to McLaren, and it’s a sector that sells about 25,000 units per year. Until now, virtually all of them were aluminium-based. Even if all carmakers in this segment move over to carbon fibre as McLaren has, it represents just 0.05 per cent of global production.
Performance cars are targeted at buyers willing to pay for new technology and so the cost can be absorbed and the production processes designed for lower numbers. Will this ever translate into mass production?
Somewhat surprisingly, the techniques used to create the MP4/1 in 1981 are still widely in use today, where the carbon fibre weave is draped over a mould and then cured in a hot oven called a clave. However, resin transfer moulding (RTM) is coming to the fore. Dry fibres are laid onto the mould, which is then placed in the tooling before resin is injected under pressure at a higher temperature.
Lamborghini adopts this process for the production of the monocoque of its new Aventador supercar, as does McLaren for the MP4-12C. The companies’ approaches are different, in that the Lamborghini monocoque is made up of several individual components brought together within a composite tool, while McLaren prefers to create a single body piece and has invested in steel tooling. McLaren also uses multiaxial non-crimp fabrics, which are faster to produce.
Although McLaren’s steel tooling is designed for relatively high production figures, a lot of manual labour still goes into every car. That’s despite the use of a robot to remove the finished MonoCell from the tool. In both cases, the laying out of the dry fibres is done manually.
Claudio Santoni, function group manager for body structures at McLaren Automotive, says McLaren’s process could be fully automated for mass production, though as its target is only 1,000 cars per year, it does not make economic sense to invest in this.
It is time for the volume manufacturers to move into the limelight. BMW has already begun work on a new carbon fibre manufacturing facility in conjunction with SGL Carbon Fibers, an American firm. The German company has claimed openly that it will be the first carmaker to bring carbon fibre construction to mass production. CFRP passenger cells will be employed in the BMW models due to market in 2013.
These cars will be battery-powered, and BMW claims to have cancelled out the extra weight of the batteries by using carbon fibre. It admits that the production process is still more expensive than it would be if using metals, but economies of scale will be in its favour.
Earlier this month, Volkswagen AG bought an 8.18 per cent share in SGL, while its sister company, Audi, opened its FRP Technical Centre last year. This forms part of the Audi Lightweight Design Centre and employs up to 50 people researching and developing production processes for carbon and other fibre-reinforced plastics.
Unsurprisingly, as Audi owns Lamborghini, there is significant cross-pollination of ideas between the two companies – despite the different target markets.
Mario’s knife skills will be required for some time yet, though perhaps not another 30 years.
