Carbon-fibre composites are making light work of aeroplanes, and now cars too.
THE central building of BMW’s car factory in Leipzig is a strikingly modern structure by Zaha Hadid, an architect renowned for her neo-futurist designs. The factory produces a variety of vehicles, so it is no surprise to find a group of robots in one area, moving in perfect synchrony as they assemble body sections with a precision no human could hope to match. But the place is unusually quiet, without any thundering metal-stamping machines or showers of welding sparks. The clue to what is going on is the colour of the components. Instead of the usual silver of steel or aluminium, these parts are black. They are made from a composite material called carbon fibre.
Lighter aircraft burn less fuel and thus have lower emissions
This factory is different in other ways, too. “We do not weld; we have no rivets, no screws and no bolts. We just glue components together,” says Ulrich Kranz, the head of the division that since 2013 has been making BMW’s i3 and i8 electric and hybrid vehicles in Leipzig. Since the carbon-fibre body provides the vehicle with its strength, the outer panels are mainly decorative and made from plastic. These are simple to spray in a small paint booth, whereas metal requires elaborate anti-corrosion treatment in a giant and costly paint shop. In all, the i3 factory uses 50% less energy and 70% less water than a conventional facility.
The i-series are upmarket cars, but still produced in volume. BMW has succeeded in taking a new material hitherto used in low-volume specialist applications, such as aerospace and defence, and turning it into something close to mass-produced. That called for radical changes. When in 2007 the BMW board asked Mr Kranz to come up with an electric city car and a low-energy production system, he and his team went into hiding to allow ideas to flow freely.
Mr Kranz’s material of choice was carbon fibre, not least to offset the weight of the battery. The material is made from thin filaments of carbon woven into a cloth. This is cut and pressed into the shape of a part and the fibres bound together with a plastic resin, cured by heat and pressure. The molecular structure of carbon compounds produces strong chemical bonds, much like those in diamonds, and by aligning the fibres at different angles the strength of a component can be reinforced exactly where needed.
The resulting structure, although stronger than steel, is at least 50% lighter, and also about 30% lighter than aluminium. Nor does it corrode. But in the past the production process was expensive, slow and labour-intensive. That may not matter too much when making fighter jets or Formula 1 racing cars. But even aircraft-makers had to speed things up and bring down costs when they started making passenger jets from carbon fibre.
These days carbon fibre makes up about half the weight of aircraft such as the Boeing 787 Dreamliner or the Airbus A380 and A350. Lighter aircraft burn less fuel and thus have lower emissions. They can also carry more passengers and fly farther. There are economies in manufacturing, too, because large sections of the aircraft can be made in one go instead of having to join together lots of smaller aluminium panels. Aircraft-makers have found ways to speed up some of the production process, but it is still too slow and expensive for high-volume car makers.
The answer that BMW came up was a different sort of factory and a new supply chain. It begins in Otake, Japan, with a joint venture between SGL group, another German company, and Mitsubishi Rayon. This produces what is called a precursor, a polyacrylonitrile thermoplastic, which looks a bit like fishing line wound onto large spools. This is shipped across the Pacific to Moses Lake in Washington state, the site of another joint venture, this one between BMW and SGL. The location was chosen because it uses locally generated emission-free hydroelectric power.
The answer that BMW came up was a different sort of factory and a new supply chain. It begins in Otake, Japan, with a joint venture between SGL group, another German company, and Mitsubishi Rayon. This produces what is called a precursor, a polyacrylonitrile thermoplastic, which looks a bit like fishing line wound onto large spools. This is shipped across the Pacific to Moses Lake in Washington state, the site of another joint venture, this one between BMW and SGL. The location was chosen because it uses locally generated emission-free hydroelectric power.
When the stacks arrive at the Leipzig factory, they are heated and pressed into a three-dimensional “preform”. Various preforms are placed together to make up large structures, which together are pressed again, but this time resin is injected into the mould, bonding and curing the final component inside the press tool. This usually happens within minutes, though in some aerospace factories the curing can take the best part of a day and requires a pressurised oven called an autoclave. Robots move the parts around and glue them together to make the main body structure of the car. Further along the production line the body is mated to the drive module, which incorporates an aluminium chassis, electric motor, battery and other components.
Mr Kranz expects carbon fibre to be used more widely in cars, but thinks they will always contain a mix of materials. BMW’s new 7 series executive car now has some carbon-fibre parts as well. Other carmakers are starting to use the material, and Apple, which has hinted that it plans to build an electric car, has reportedly been talking to BMW about carbon-fibre construction. Anthony Vicari, an analyst with Lux Research, a Boston consultancy, predicts that by the mid-2020s carbon fibre will be widely adopted in carmaking.
The upshot is that manufacturers are being offered a wider choice of materials than they had before, says Mr Botti. Carbon fibre has done wonders in aerospace, he reckons, but it is used largely in the bigger, long-range aircraft, of which only a handful might be built every month. To increase the use of carbon fibre in smaller aircraft, aerospace firms have to speed up production and bring down costs further, but “there are new techniques we are thinking about which could tremendously reduce the cost of carbon fibre.” Airbus and Boeing both have plans to raise production of their workhorse short-haul aircraft, respectively the A320s and 737s, to an astonishing 60 or so a month to meet order backlogs. Still, he cautions, companies should always take care to select the best material for a particular job. If Airbus were to replace the A320 with a new model, he says, he would have to look carefully to see if carbon fibre provided the best value in a short-haul aircraft.
Airbus is also developing its own new materials. One of these is a proprietary aluminium-magnesium-scandium alloy called Scalmalloy. It is particularly good for making lightweight high-strength components. It is being commercialised by an Airbus subsidiary and is already used in some racing cars. In powder form, Scalmalloy can also be employed in a revolutionary form of manufacturing that is ideally suited to working with many new materials: additive manufacturing, popularly known as 3D printing.
THE central building of BMW’s car factory in Leipzig is a strikingly modern structure by Zaha Hadid, an architect renowned for her neo-futurist designs. The factory produces a variety of vehicles, so it is no surprise to find a group of robots in one area, moving in perfect synchrony as they assemble body sections with a precision no human could hope to match. But the place is unusually quiet, without any thundering metal-stamping machines or showers of welding sparks. The clue to what is going on is the colour of the components. Instead of the usual silver of steel or aluminium, these parts are black. They are made from a composite material called carbon fibre.
Lighter aircraft burn less fuel and thus have lower emissions
This factory is different in other ways, too. “We do not weld; we have no rivets, no screws and no bolts. We just glue components together,” says Ulrich Kranz, the head of the division that since 2013 has been making BMW’s i3 and i8 electric and hybrid vehicles in Leipzig. Since the carbon-fibre body provides the vehicle with its strength, the outer panels are mainly decorative and made from plastic. These are simple to spray in a small paint booth, whereas metal requires elaborate anti-corrosion treatment in a giant and costly paint shop. In all, the i3 factory uses 50% less energy and 70% less water than a conventional facility.
The i-series are upmarket cars, but still produced in volume. BMW has succeeded in taking a new material hitherto used in low-volume specialist applications, such as aerospace and defence, and turning it into something close to mass-produced. That called for radical changes. When in 2007 the BMW board asked Mr Kranz to come up with an electric city car and a low-energy production system, he and his team went into hiding to allow ideas to flow freely.
Mr Kranz’s material of choice was carbon fibre, not least to offset the weight of the battery. The material is made from thin filaments of carbon woven into a cloth. This is cut and pressed into the shape of a part and the fibres bound together with a plastic resin, cured by heat and pressure. The molecular structure of carbon compounds produces strong chemical bonds, much like those in diamonds, and by aligning the fibres at different angles the strength of a component can be reinforced exactly where needed.
The resulting structure, although stronger than steel, is at least 50% lighter, and also about 30% lighter than aluminium. Nor does it corrode. But in the past the production process was expensive, slow and labour-intensive. That may not matter too much when making fighter jets or Formula 1 racing cars. But even aircraft-makers had to speed things up and bring down costs when they started making passenger jets from carbon fibre.
These days carbon fibre makes up about half the weight of aircraft such as the Boeing 787 Dreamliner or the Airbus A380 and A350. Lighter aircraft burn less fuel and thus have lower emissions. They can also carry more passengers and fly farther. There are economies in manufacturing, too, because large sections of the aircraft can be made in one go instead of having to join together lots of smaller aluminium panels. Aircraft-makers have found ways to speed up some of the production process, but it is still too slow and expensive for high-volume car makers.
The answer that BMW came up was a different sort of factory and a new supply chain. It begins in Otake, Japan, with a joint venture between SGL group, another German company, and Mitsubishi Rayon. This produces what is called a precursor, a polyacrylonitrile thermoplastic, which looks a bit like fishing line wound onto large spools. This is shipped across the Pacific to Moses Lake in Washington state, the site of another joint venture, this one between BMW and SGL. The location was chosen because it uses locally generated emission-free hydroelectric power.
The answer that BMW came up was a different sort of factory and a new supply chain. It begins in Otake, Japan, with a joint venture between SGL group, another German company, and Mitsubishi Rayon. This produces what is called a precursor, a polyacrylonitrile thermoplastic, which looks a bit like fishing line wound onto large spools. This is shipped across the Pacific to Moses Lake in Washington state, the site of another joint venture, this one between BMW and SGL. The location was chosen because it uses locally generated emission-free hydroelectric power.
When the stacks arrive at the Leipzig factory, they are heated and pressed into a three-dimensional “preform”. Various preforms are placed together to make up large structures, which together are pressed again, but this time resin is injected into the mould, bonding and curing the final component inside the press tool. This usually happens within minutes, though in some aerospace factories the curing can take the best part of a day and requires a pressurised oven called an autoclave. Robots move the parts around and glue them together to make the main body structure of the car. Further along the production line the body is mated to the drive module, which incorporates an aluminium chassis, electric motor, battery and other components.
Mr Kranz expects carbon fibre to be used more widely in cars, but thinks they will always contain a mix of materials. BMW’s new 7 series executive car now has some carbon-fibre parts as well. Other carmakers are starting to use the material, and Apple, which has hinted that it plans to build an electric car, has reportedly been talking to BMW about carbon-fibre construction. Anthony Vicari, an analyst with Lux Research, a Boston consultancy, predicts that by the mid-2020s carbon fibre will be widely adopted in carmaking.
The upshot is that manufacturers are being offered a wider choice of materials than they had before, says Mr Botti. Carbon fibre has done wonders in aerospace, he reckons, but it is used largely in the bigger, long-range aircraft, of which only a handful might be built every month. To increase the use of carbon fibre in smaller aircraft, aerospace firms have to speed up production and bring down costs further, but “there are new techniques we are thinking about which could tremendously reduce the cost of carbon fibre.” Airbus and Boeing both have plans to raise production of their workhorse short-haul aircraft, respectively the A320s and 737s, to an astonishing 60 or so a month to meet order backlogs. Still, he cautions, companies should always take care to select the best material for a particular job. If Airbus were to replace the A320 with a new model, he says, he would have to look carefully to see if carbon fibre provided the best value in a short-haul aircraft.
Airbus is also developing its own new materials. One of these is a proprietary aluminium-magnesium-scandium alloy called Scalmalloy. It is particularly good for making lightweight high-strength components. It is being commercialised by an Airbus subsidiary and is already used in some racing cars. In powder form, Scalmalloy can also be employed in a revolutionary form of manufacturing that is ideally suited to working with many new materials: additive manufacturing, popularly known as 3D printing.
