The Carbon Paradox: What Next for Carbon Fibre?


Carbon-fibre-reinforced polymer has long been seen as the new wonder-material. Light and incredibly strong, it’s ideally suited for precisely satisfying the requirements of varied structural rigidity throughout a single panel or member. Widely adopted in aerospace, military, Formula One, low-volume supercars, wind turbines and the sports and recreational industries, we are now on the verge of seeing CF filtering through to higher production, lower cost cars. But what about its suitability for mainstream automotive use and its green impact both today and in the future? What about the dark side of the dark stuff?

Is naked carbon fibre pleasing to the eye or not?

The automotive industry today is suffering from burgeoning weight. Power steering, air conditioning, ABS, powered windows, mirrors, sunroof, locks and seats as well as numerous airbags and additional safety devices are all expected – whether we need them or not – and increased crash protection consequently balloons weight further. CF offers an excellent solution to weight reduction. Using a CF chassis alone can reduce weight by around 12.5%, and with the addition of CF panels replacing pressed steel it’s possible to trim over 300kg from the total weight of a car. The end result is a 15-20% saving in fuel consumption – something that’s hard not to get excited about. Aside from its low weight, high tensile strength, excellent resistance to fatigue, ability to be moulded into complex shapes and its high modulus (resistance to stretching), CF is also particularly suitable in high temperature and high damping applications as well as those requiring chemical inertness. You don’t have to think about rust, for example, and compared to steel it can be as much as five times as strong, twice as stiff and a third of the weight. These fundamental benefits of carbon fibre soon add up; it is impossible to discount the oil-based material from the world’s manufacturing future.

Current drawbacks are, however, quite severe. And for the most part are the result of under-development due to its relative youth and niche usage. Compared with steel and aluminium, production is slow, requiring huge amounts of energy, and costs and wastage are high. The component sections of each fabricated part are cut from a roll of fibre, and even with computerised optimisation of the most economical layout wastage of around 30% can be expected: these offcuts are in fact the largest source of CF waste. Following production, wastage due to imperfections is typically 6% compared to a figure many thousand times smaller with steel or aluminium. Conversely, costs can be 10 times as much when compared to pressed steel and are currently dependent on the price of oil, which increases as night follows day.

The problem with recycling carbon fibre is that samples get progressively smaller

McLaren, again building road cars alongside the fastest Formula One cars on the grid, identify one of their major issues as supply chain problems, which can occur if there is a sudden demand for CF in large aerospace projects, although recently these have seen a decline. Furthermore, certain materials (for example pre-preg matting) have a limited shelf-life. CF is unstable when crashed and unlike metal cannot be pulled back into shape. Finally due to the nature of composites, CF is extremely difficult to separate and is neither biodegradable nor photodegradable.

Despite the current drawbacks, automotive manufacturing is expected to account for up to 10% of total CF consumption by 2015, and automakers at all levels in the industry are experimenting. Most mainstream manufacturers are investing strongly, the leader presently being BMW with their new BMWi sub-brand - formed to handle BMW's electric car and mobility service offerings. The i concepts focus on the cradle-to-cradle lifecycle of the vehicles and solutions that are based on intensive research in megacities around the world. The cars will introduce the LifeDrive concept: two separate modules comprising the passenger cell (‘Life’) and beneath it a flat aluminium rolling-chassis containing the batteries, running gear and providing impact absorption (‘Drive’). This is an entirely new architecture which opens up an enormous amount of flexibility in terms of both build and design. BMW are investing strongly in the new brand, upgrading their production facilities throughout Germany and more significantly, in conjunction with SGL Group – one of the largest carbon-based manufacturers, are building a CF manufacturing plant in Moses Lake, Washington. The initial phase alone will cost US$100 million.

Large oxidation ovens are part of the manufacturing process

Ford are also investing strongly in CF and have recently demonstrated a prototype CF bonnet which could be produced quickly enough to join existing Focus production lines. The bonnet is constructed using a refined gap-impregnation process where resin is introduced to pre-formed carbon fibre textile. It also performs well in pedestrian crash tests due to a construction of a foam core sandwiched between two layers of CF, although Ford have made it clear that this component will not reach production in the near future. Meanwhile Ferrari CEO Amedeo Felisa has stated that Ferrari have chosen aluminium alloy in favour of CF, but has suggested that CF will meet their production requirements by 2020. Riversimple, an innovative British hydrogen car company is currently developing an open-source hydrogen fuel cell car, and CF is the obvious choice for chassis and body manufacture. They will be turning the conventional sales model on its head by making the car available on a lease-only basis. Instead of producing cars with ‘built-in obsolescence’, Riversimple cars will be designed and made to last as long as possible, with a cradle-to-cradle lifecycle key in the production. In this way, Riversimple will be able to either reuse or recycle the cars/components in-house, massively reducing the environmental impact of the vehicles both throughout, and at the end of, their life. This fits well with the issue that even though CF itself is extremely durable, other major components have a shorter life and can render the remainder of the vehicle redundant.

One of the chief arguments for CF is that steel is likely to become less cost efficient over the coming years due to increasing European Union taxes on vehicle emissions. Currently manufacturers that exceed targets pay a penalty for each car registered, amounting to €5 for the first g/km of CO2 over the limit, €15 for the second g/ km, €25 for the third, and €95 for each subsequent gram. It soon adds up, and from 2019 the fine will rise to €95 from the first gram. Conversly, the price of composites fabrication is constantly falling and annual growth in the automotive sector is around 10%, yielding a 10% annual reduction in process cost due to increased capacity and volumes. CF technology is constantly advancing and although current processes are largely dependent on the oil industry, there are new organic materials in the wings such as curran (based on carrot fibre) and lignin (also a renewable organic material). These could be up to 25% less expensive than current petroleum-based fibres.

Carbon fibre production isn't cheap in energy terms, typically with 30% wastage

The most significant problem today with recycling CF is that the product is more expensive than new material and often inferior. The fibres are already shorter due to breakage caused by high moulding pressures and recycling processes can further damage them. Together with their increased weakness, they are usually only suitable for physically smaller applications. This can often be handled by ‘closing the loop’ where manufacturers reuse the recycled material in-house. For example, a redundant bonnet could be used as source material for interior trim panels. A further issue is that the feedstock received by recyclers is mixed, of massively variable unknown quality and often contaminated which complicates the process further. There is no doubt whatsoever that CF is going to penetrate the automotive mass-market at some point between 2015 and 2030. BMW’s considerable investment is an early indicator, and as take-up increases, costs will fall and adoption will rise exponentially. Current technology is far from viable in terms of mass-market D production processes, time constraints and wastage, and recycling is currently a concern, but following Riversimple’s model of reuseable cars, perhaps a perception shift will lead in part to the acceptance of reuse rather than recycling. This, however, is likely to be a longer-term proposition and will become less of a requirement in the shorter-term as soon as viable mass-market bio-based resins and fibres reach production. Once the price of CF has fallen to a critical point, the cost of manufacturing could be cut by as much as 80% due to substantially reduced tooling and simplified assembly and joining. The ever more stringent emissions regulations will also force manufacturers to invest in weight-saving measures.

As with any new technology, take-up begins slowly and doubts threaten to undermine success, but with CF once the drawbacks are sufficiently mitigated (and they will be) we will see an exciting and sustainable leap forward in automotive construction. It is not unreasonable to imagine by 2030 fully degradable and recyclable materials which use significantly less energy to produce and are truly viable replacements for steel and aluminium.

The end product: Mercedes' SLS Electric Drive extensively uses carbon fibre

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