NPE: Driving technology

Lou Reade

21-Nov-2014

The automotive industry has always been at the cutting edge of technology – and was among the first to adopt engineering plastics as a material of choice.

One futuristic material finding its way into cars is carbon fibre composites – not just supercars, but higher volume models such as BMW’s i3 series of electric “city cars”. The i3 illustrates how carbon fibre is being adopted by the industry, especially in forward-looking models that run on electricity or, potentially, fuel cells.

New materials go hand-in-hand with new technologies. And 3D printing – also known as additive manufacturing (AM) – is one of the newest. It builds components up in layer-by-layer fashion, using powdered material (usually plastic) that is cured into a solid.

3D printed car

Strati concept car: 3D-printed using a carbon fibre-reinforced ABS material from SABIC

A special conference on the subject, 3DNPE, will run during the show. Among the speakers are Tom Hocker, a scientist at SABIC, who will explain how high-performance thermoplastics – such as its Ultem, Cycolac and Lexan resins – are increasingly being used in AM.

Although AM is normally used for relatively small components, it was recently used to form the entire shell of a concept car called Strati using LNP Stat-Kon AE003, a 15% carbon fibre-reinforced acrylonitrile-butadiene- styrene (ABS) from SABIC. Cincinnati Inc made the car using its Big Area Additive Manufacturing machine. It chose SABIC’s material because it extrudes well and has low thermal expansion, which cuts warpage to a minimum.

“The automotive industry has used additive manufacturing as a prototyping tool for many years,” says Tony Cerruti, director of industrial marketing for the Americas at SABIC’s Innovative Plastics business unit. “More recently, it’s been adopted to produce assembly jigs and fixtures. But we expect the industry to embrace AM technologies for part production.”

Strati, which SABIC is hoping to showcase at the event, is a concept car, so unlikely to become commercial. But the process of building it could help manufacturers understand where 3D printed parts could be used commercially.

“Initial target applications will likely include those that take advantage of the available material portfolio and unique design capabilities of AM, such as interior decorative trims or custom seating,” says Cerruti.

In a similar vein, technology and specialty materials company Celanese will explain its part in using advanced materials for cars of the future. Its subsidiary Ticona is part of the collaborative Durastor project in the UK, which is developing a composite pressure vessel to store hydrogen at pressures of 70MPa for use in fuel cell-powered cars. The prototype vessel is 900mm long, 300mm in diameter and has an internal volume of nearly 33 litres – equivalent to around 1.3kg of hydrogen.

EARLY STAGES

During NPE2015, Celanese global composites business director Michael Ruby will outline the first phase of the project, including the design of the inner cylinder, choice of materials and processing technologies.

Early work focused on rotomoulded polyacetal (POM) liners, overwrapped with filament-wound, carbon fibre-reinforced POM in the form of unidirectional tapes. When heated, they will create a “fatigue-resistant, monolithic structure”.

This design overcomes several problems of hydrogen storage cylinders. First, they tend to use different materials for the liner and reinforcement, which can be susceptible to fatigue. Metal-lined structures are also subject to damage through hydrogen embrittlement, which can cause cracks.

Using thermoplastic POM rather than thermoset materials also makes the vessel recyclable – a key aim of the project.

LIGHT WORK

Whether cars are powered by electricity, fuel cells or conventional fuel, plastics are there to help the industry fulfil its number one issue: reducing weight.

“Lightweighting is the song of the day in automotive,” says Austen Angell, chairman of the Industrial Designers Society of America. “The industry wants materials that can help it meet emission standards.”

Plastics have always been central to lightweighting in automotive, and many have sufficient aesthetic qualities to satisfy consumers. However, Angell sounds a warning: lightweighting can mean removing “layers” from the car interior – which can expose previously “hidden” materials.

“These underlying materials must now be seen in daylight – so their aesthetic qualities will need to improve,” he says. “The onus is on material compounders to solve that.”

For example, a car interior may have used a vinyl leather effect covering to mask an underlying material. If that material could be engineered to take colour well, the cover could be eliminated.

“The part may no longer have a leather effect, but it should have a pleasing aesthetic with reduced cost, material use and weight,” he says.

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