Reclaiming continuous carbon fibre, from end-of-life composites pressure tanks
Engineers at the National Composites Centre, the UK’s centre of excellence for advanced composite applications, along with British SME partners B&M Longworth Ltd and Cygnet Texkimp, have successfully reclaimed continuous carbon fibres from a whole pressure vessel and re-used them to manufacture a new pressure vessel. This is the first time this process has been achieved in the UK and represents a significant milestone in the development of Britain’s hydrogen capability.
As the gas has low energy density it needs to be compressed and stored at very high pressures, between 350 to 700 bar (5,076 – 10,152 psi). This makes high-strength, lower-weight carbon fibre the material of choice, especially for hydrogen pressure vessels in vehicles such as cars or aircraft, where power-to-weight is critical. Demand for carbon-fibre is expected to grow five-fold between 2025 and 2030, exceeding global manufacturing capacity. Creating viable, low cost recovery processes, that retain the inherent strength of continuous carbon fibres for recycling, is therefore key to the development of the hydrogen economy.
Until recently, recycling processes for composite components such as aircraft wings and wind turbine blades has resulted in short fibres with lower mechanical properties than virgin fibre. Whilst there are applications for this material, it is not suitable for re-use in high performing products.
Partnering with Lancashire-based B&M Longworth Ltd, the National Composites Centre team successfully reclaimed continuous carbon fibre, from end-of-life composite pressure tanks, using the company’s revolutionary DEECOM® process. Originally designed to remove waste polymers from filters and production equipment, the process uses superheated steam, under compression, to penetrate microscopic fissures in the composite’s polymer, where it then condenses. On decompression, it boils and expands, cracking the polymer and carrying away broken particles. This pressure swing cycle is then repeated until all the matrix (the material suspended in the polymer) has been separated from the fibre, allowing the monomers to also be reclaimed for possible reprocessing.
Crucially, the DEECOM® process leaves the primary component material intact and undamaged, allowing for any length to be retained. As a result, National Composites Centre engineers working with Cygnet Texkimp Ltd, a Cheshire-based, global leader of fibre handling and conversion technology, could use the reclaimed continuous carbon fibre to make a new pressure vessel using filament winding.
The partnership is now looking to work with manufacturers to scale and industrialise this process, sharing the knowledge of recent recycling trials. The next step is to undertake fibre characterisation analysis of the reclaimed material and recycled vessel, as the team works towards their ultimate goal: developing the disruptive technologies that enable sustainable hydrogen storage solutions.
The fibre recovery and recycling project, forms part of the National Composites Centre’s Hydrogen programme, developing and sharing the technical knowledge, cross-sector composite expertise and state of the art technology that businesses need to achieve their hydrogen ambitions.
As part of this programme, National Composite Centre engineers have worked to refine composite pressure vessel designs, producing detailed design and analysis to minimise waste and trial the tools and manufacturing processes industry will use to reclaim and recycle continuous carbon fibres. They have also delivered composite design specification for cryogenic pressure vessels and are working on a certification pathway for composite pressure pipes, including those to be used offshore.