Upcycling carbon fibre for next-generation aircraft

Researchers at Dornsife College Of Letters, Arts and Sciences in California have made progress towards the upcycling of high-performance composite materials.

Modern aircraft typically feature eight or more layers of woven carbon fibre held together with strong epoxy resin. The lack of effective recycling solutions for this material means many of airplanes have no more use once they have been decommissioned.

Dornsife chemistry professor Travis Williams estimates 99% of aviation and automotive composite materials end up in landfills as recycling is too complex and expensive. The remaining 1% that is recycled is subjected to high temperatures which damage the material.

Unboiled, please

‘Trying to un-thermoset a thermoset or un-epoxy an epoxy is like trying to unboil an egg,’ Williams observes. He is pioneering a method to transform polymer into high-cost, valuable substances.

‘We started inventing reactions to treat the different kinds of epoxies and thermosets they use in aviation. It worked in a number of cases. You can get it back, still woven as fabric and nobody else has been able to do that. So this work has got people’s attention.’

The process of upcycling carbon fibres from composite material consumes 10.8 – 36 megajoules of energy per kilogram. The production of new carbon fibres requires 198 – 594 megajoules per kilogram. On top of that, upcycling accounts for only a fifth of the cost of virgin fibre production.

Lightweight and robust

Williams says the carbon fibres upcycled through this method are lighter and stronger than aluminium. As a result, they would benefit the aviation industry ‘tremendously’.

Being lightweight, aircraft made from recycled carbon fibre would require 20% less fuel which also leads to a significant reduction in CO2 emissions, he adds.

Tests indicate that recycled carbon fibres maintain nearly the same mechanical properties as original fibres. For example, they retain at least 90% of the original tensile strength.