The AFRECAR (Affordable Recycled Carbon Fibres) project will develop low-cost, high-strength manufacturing materials based on recycled carbon fibre.
Half of the weight of Boeing’s new 787 passenger airliner is made up of carbon fibre composites. This makes it stronger, lighter, more fuel efficient and therefore cheaper to fly. Older aircraft which are now out of service are ending up in aircraft ‘graveyards’ located in deserts across the world. The idea is to recycle and reuse the valuable carbon fibre which up to now has only been disposed of in landfill.
New carbon fibre costs upwards of £10,000 a tonne which is why the industry considers it worth recycling. Lead researcher on the project in the Division of Mechanics, Materials and Structures in the University’s Faculty of Engineering, Dr Steve Pickering, said: “The UK is taking a lead globally in developing recycling technology for carbon fibre and this research will ensure that we continue to be at the forefront of new developments.” The project team also includes Professor Nick Warrior and Dr Ed Lester.
Billy Glover, Managing Director, Environmental Strategy for Boeing Commercial Airplanes, said: “The Boeing commitment to the environment is reflected in our proactive involvement in composites recycling. We continue to work with industry leading technology developers and recyclers towards environmentally progressive recycling for aircraft production and end-of-life. This project will provide key technology contributions for carbon fibre composite recycling solutions.””
There are emerging commercial processes for extracting the carbon fibre from a composite but there are two problems that need solving; how to process the recycled carbon fibre to produce new products that can give the very best structural properties and how to improve on the existing recycling processes to recover useful products from the polymer resin used to bond the carbon fibres together in the composite? Up to now, work on recycling carbon fibre has used thermal (heat) processing to decompose the polymer resin leaving clean carbon filaments which can be bundled or pressed into sheets for re-use. But this process leads to a slightly degraded product. This new research will investigate a cleaner and more efficient way of extracting the fibre by dissolving the composite in supercritical fluids. This method will also extract the chemicals out of the polymer resin so there will be less waste.
Supercritical fluids are substances at a temperature and pressure above their thermodynamic critical point. They can diffuse through solids like a gas and dissolve materials like a liquid and are suitable as a substitute for organic chemical solvents in a range of industrial and laboratory processes.
New techniques are also being developed to process the recycled carbon fibre into forms that can achieve much greater proportions of recycled carbon fibre in a composite and so give better structural properties.
The £900,000 project is funded by the Technology Strategy Board. The other partners are the aircraft makers Boeing, the Ford Motor Company, composite materials supplier Advanced Composites Group, fibre processing company Technical Fibre Products, carbon fibre manufacturer Toho Tenax and Milled Carbon, a company leading the way in carbon fibre recycling.
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