Carbon fibre in the fast lane

A single fibre is just a fraction of the thickness of a human hair. When combined, however, carbon fibre is an extremely light yet strong material that is now an essential part of aircraft and automotive construction, offering almost limitless possibilities, particularly when combined with other materials.

© Wolfram Schroll

Fibre reinforced plastics – also known as composite materials – are now ubiquitous in many industries: they have taken over the aircraft and automotive manufacturing industries and are the material of choice for modern wind turbines and have even had a lasting influence on boatbuilding.

Composite materials offer many benefits. They are light in weight, extraordinarily strong, and give engineers virtually free rein in design and manufacturing as, unlike metals and other materials, they can be produced in complex shapes. As well as carbon fibre, there are many other fibres – with glass and aramid fibres being most frequently used for vehicles and aircraft. Each material has its own advantages and disadvantages. Carbon fibre reinforced plastic (CFRP) is particularly light with exceptional tensile strength – but it is also expensive and sensitive to pressure with a tendency to shatter when overloaded. Fibreglass components (GRP) are heavier and not as strong, but they are cheaper to buy. Aramid fibres – also known by the brand name, Kevlar, are particularly tough and are used in items such as bulletproof vests. In the aircraft industry, they are the first choice for protecting crew from the consequences of an accident. However, they are difficult to cut and to work with.


Precision is essential

The manufacture of fibre reinforced plastics requires the utmost precision. While small home projects can often be achieved with a manageable amount of effort, in industry, the bar is set extremely high. Aircraft manufacturers in particular must work with extremely high levels of accuracy to achieve the required weight and strength targets. The starting point is always a fibre mat, no matter whether it is made of carbon, glass or aramid fibres. A plan is devised to determine how the fibres will be formed into the shape of the future component. Resin and hardeners are mixed in a precisely defined ratio and combined with the fibre in tightly-controlled conditions in a lamination process. Excess resin is removed by suction in a vacuum. The prepreg process, which uses previously impregnated carbon fibres, is particularly precise. The components are then treated with the application of heat in a tempering chamber or an autoclave to ensure that the finished product meets the required standards. There are multiple variations of this process: components can be made with any numbers of layers, and blends of different fibres are just as possible as the construction of sandwich components that enable greater strength at a lower weight by inserting a layer of foam or honeycomb between the outer composite layers.


Carbon fibre mat used in the manufacture of CFRP

A carbon fibre mat is always used at the start of the process of manufacturing CFRP - © Headhuey [CC BY-SA 3.0], via Wikimedia Commons

 

Modern, yet well-proven

These materials have proven their strength over the course of several decades. As an example in the aircraft industry, the glider manufacturer, Alexander Schleicher, released the Gerhard Waibel-designed ASW-15 fifty years ago. The single-seater, standard-class glider was overwhelmingly made from fibreglass and replaced the Ka 6, which was made from wood. The design can still be encountered at many different airfields today. The story of the RW-3 Multoplane, which dates from 1955, reaches even further into the mists of time: Hanno Fischer’s two-seater was the first German motorised aircraft after the Second World War, as well as being the first to use moulded fibreglass components. Even in the water, composite boats – mainly using glass fibre – have survived several decades without suffering damage, as a glance in the marinas of the North Sea and Baltic, or the market for used sailboats demonstrates. Meanwhile, boats in the Volvo Ocean Race are high-end carbon fibre racers that combine minimal weight with optimal hydrodynamics.


Schleicher ASW 15

Schleicher ASW 15 single-seater glider, which is mainly made from carbon fibre - © Jelle Vandebeek [CC BY-SA 2.0], via Wikimedia Commons

 

The increasing importance of carbon fibre

Applications have become ever more sophisticated over the last few years. From road racing to airliner manufacturing or space travel: light, rigid carbon fibre is firmly in the fast lane. Our photographer, Wolfram Schroll, captured the use of carbon fibre in the production of modern aircraft at Airbus’s plant in Ottobrunn for our July calendar page. Boeing and Airbus are both making increasing use of carbon fibre for their current models. Aircraft such as the Airbus A350, for example, are becoming lighter and offering increased payloads. Corrosion is no longer and an issue and there is less wear on the fuselage than with traditional construction techniques. Airlines benefit from lower fuel consumption and longer maintenance intervals, with these points also applying to aircraft such as the Boeing 787 Dreamliner.

Carbon fibre has created a genuine revolution in the world of ultralight aircraft. Over the last two decades, manufacturers have successfully created fast and light aircraft that no longer have anything in common with the original tubular ultralights of the 1980s and 90s. Designs like the VL3 from JMB Aircraft or the Blackshape Prime are highly visible examples of what can now be achieved using carbon fibre.

Even in the space industry, carbon fibre’s advantages as a material are becoming clear – every kilogramme of weight that is carried into orbit costs a fortune. NASA is therefore rethinking old concepts and working on carbon-fibre based construction. Meanwhile, the spectacular launch of a Tesla electric car into deep space using Space X’s Falcon Heavy launch vehicle was only possible due to the use of carbon fibre.


Carbon fibre is also on the rise in the automotive industry

Anything that is true of the aircraft industry eventually makes its way to the automotive sector. While Formula 1 has long been completely dependent on carbon fibre, the material has gradually made inroads into large automotive manufacturers, with BMW being among those at the cutting edge: the roof panel of the Seven Series saloon is one of the first carbon fibre components to be used in mass production. The focus on CFRP components continues in BMW’s own motorcycle division, while the Swedish supercar manufacturer, Koenigsegg has been reliant on the benefits of carbon fibre for years. One example of this can be found in its CCX model, which was launched in 2006, with supercars having proven the value of carbon ceramic brake discs and pads.


 
 

BMW also uses CFRP components in its G11 7 Series - © BMW Group


Environmentally-friendly wind energy thanks to carbon fibre

Sustainable energy production also relies on composite materials. The blades of a wind turbine have become larger over the last few years and now measure up to 85 metres in length, while the height of the turbine itself approaches the 200-metre mark. While glass fibre plastics were the main material used in manufacturing the blades, the trend has now moved towards carbon fibre as it is the ideal choice of material in view of the enormous forces that result. To increase the efficiency of wind turbines while extending their service lives, DLR is working on intelligent robotic blades that can adapt to the wind. Known as Smart Blades, they work with both active and passive technologies that allow individual robotic blades to adapt to wind conditions.


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