Boeing looks to carbon recycling for weight reduction

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Boeing is nearing the implementation of a carbon fibre recycling effort for its 787 programme to reduce waste and use scraps to develop secondary aircraft structures.

The airframer is aiming to collect uncured carbon fibre scrap used in the manufacturing process to build items such as brackets and clips and cured material for interior parts and passenger seat backs, which may reduce the weight of a widebody aircraft interior as much as 450 to 900kg (1,000 to 2,000lbs), said Boeing's programme manager of composite recycling Bill Carberry, who also serves as deputy executive for the Aircraft Fleet Recycling Association (AFRA).

"We're beyond concept, we're doing it," said Carberry.

 

 
   

Prior to curing in autoclaves, scrap carbon fibre strips accumulate, and following curing certain structures require precision cutouts for windows, cargo and access doors, resulting in unused carbon fibre panels in which Boeing seeks significant future potential.

"For the pre-production ply lay material that's been cured, we are already able to scrap cured carbon fibre, recycle it, bring the fibre back into manufacturing applications. We've made proof-of-concept parts, we're now working on a strategy to make proof of concept assemblies," Carberry explained.

It is easier to take an assemblies-driven strategy combining an array of carbon fibre parts, rather than to swap existing parts with recycled carbon fibre ones due to the complexity of existing engineering drawings.

"If we can get whole assemblies that are made out of recycled material then it's easier to get that incorporated in the airplane. We've cracked that nut," said Carberry of the design ability.

"We don't have whole assemblies designed yet," he added, "We're working on strategies of which ones to do this Fall and I think you're going to see that soon."

Working in conjunction with a British consortium that is partnering with the University of Nottingham and Affordable Recycled Carbon Fibres (AFRECAR), Boeing is developing techniques to use the discarded pre-cured chopped carbon fibre strands.

Carberry said the key to full industrialisation for uses in secondary structure is increasing the carbon fibre density from today's 10 g/m3 to 200 to 250g/m3. The target for "figuring that technology out", to compete with fibreglass is roughly a year away, said Carberry.

"Right now fibreglass is cheap, right now fibreglass is available and when we put a technology like [recycled carbon fibre] on an airplane it's all well and good to do it with a good environmental message," said Carberry, "You have to earn your way on to the plane."

Further, Boeing's vice president for environment, health and safety Mary Armstrong said carbon fibre scrap could have a second life as composite tooling for interior parts.

"We hope to expand that to a much wider range of aerospace tooling," said Armstrong.

Traditional metal construction afforded clearer opportunities for recycling, as metal scraps are compiled, melted down and reused, the widespread application of carbon fibre on the 787 is viewed as holding untapped potential for reducing production cost.

"We've always recycled metals in our processes, but we're just working now on the quantification on the carbon," said Armstrong of the potential economic benefits.

"It's a technology that's new and it is building its place and it is not at the cheapest operational level as it could be, where metal recycling is at a more mature form," said Carberry, who is direct about the work yet to be done to bring the cost down.

"We still have some technologies to develop to make carbon fibre really competitive in terms of revert content going back on the plane.