Bio-Composite Automotive Bodywork Panels

Bio-Composite Automotive Bodywork Panels

About the Project

A £100,000 research project evaluated the potential use of bio-composite materials in the production of future automotive vehicle bodywork panels. Research supported by a £50,000 grant from the Niche Vehicle Network was led by Performance Engineered Solutions (PES) Ltd, alongside project partners, TEKS UK Ltd and the University of Sheffield Advanced Manufacturing Research Centre (AMRC) with Boeing.

The ELCOMAP (Environmentally friendly lightweight composite materials for aerodynamic body panels) project researched the potential alternatives to composite technologies currently in use such as carbon fibre and epoxy resin systems. The technology has the potential to revolutionise the production of low volume specialist components for high performance vehicles.

The Project

The project used a partially bio-based composite to create large Porsche and Subaru components. They were made from an epoxy-based composite. But 30% of the epoxy resin was replaced with cashew nut shell liquid, while the fibre used was flax.

Cashew nut shell liquid was originally a waste product of the cashew nut extraction process. The dark oil, obtained from within the shell, has become a popular precursor for making ‘green’ resins.

The team produced two Porsche rear panels and a larger Subaru front end using the material. The company has done lots of previous work on bespoke vehicles, spending more than 10 years taking weight out of road-going Porsche cars which gave a good platform to benchmark against what had been done in the past.

The team chose to make prototype panels for high performance, niche road vehicles, and deliberately decided to go beyond traditional ‘flat aesthetic’ panels in favour of ones with more complex geometries.

The Porsche parts were a rear bonnet and boot. The boot lid was designed as an upper and lower skin, which allowed the geometry to be moulded and removed from the tooling. Threaded inserts were included in the part allowing it to be mounted to the chassis. The part ended up being 2mm thick. Overall, the part was 6kg lighter than the 1mm thick steel original and the added thickness of the part ensured a higher stiffness. Because the component was based on epoxy it was cured in an autoclave at 120°C for two hours at 6-7bar.

The Subaru part was a full front splitter. The tooling was created from glass fibre composite, with wooden stiffeners – a low cost option. Components were laminated using the same process as for the Porsche boot lid, and oven cured at around 90°C. The lower temperature was to take account of the materials used in the mould.

Results

The test parts showed that commercial bio-composites components using these materials could potentially become a reality. Traditionally, the move away from established materials towards bio-based grades can lead to a loss of mechanical properties. But in this case, the resin, with 30% cashew nut oil, was found to be actually tougher than standard epoxy. The next target is a full bio-composites panel – in which epoxy has been completely replaced by cashew nut oil.

Market acceptance of such bio-composite parts will be more dictated by whether they can be made via an automated process, rather than the properties of the material itself.

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