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  • Writer's pictureNed Patton

Sustainable Composites

What, exactly, do I mean when I say “sustainable composites”? That is a very good question, because sustainability means different things to different people. If you are an aircraft manufacturer (Boeing and Airbus of course), sustainability means permitting production rates of all composite aircraft that rival how many Boeing 737s are produced a month. Neither the 787, nor the Airbus A350 are made at anywhere near the production rates of the 737. And, from what I’ve read, it is the single aisle aircraft like the 737 and A220 that dominate the market in terms of total aircraft delivered to customers. That is because the fleet that is out there now is aging rapidly and there are going to need to be lots more single aisle aircraft produced in the next few years than have been produced for some time. American Airlines is in fact replacing its entire fleet.

But that isn’t what this blog is about. What I want to talk about is the fact that only 10-15% of the current aging composite structures (wind turbine blades are a good example) are recycled and reused in new products. That’s where sustainability of the new composite structures comes in.

Fortunately, there is a lot of research going on in what people are calling “green” composites. This runs the gamut from developing new fibers and resins that can be separated from each other at the end of life of the part or structure, to moving from thermoset plastics to thermoplastics for resins so that the resin can be melted away from the fibers and both constituents can be reused. I talked a bit about that when I talked about composites in the ocean and what NREL is up to. They are looking to use thermoplastics for a number of reasons, but one of them is that they are inherently recyclable and reusable.

And there are some chemical methods for removing the resin from the fibers that allows the fibers to be reused in a new product or structure (see the image to the left). The resin can be separated from the chemistry that dissolved it and also re-processed into new plastic feedstock. This feedstock is far less expensive to use than breaking down petroleum and processing it into new plastic and making new fibers from it.

Bottom line – entrepreneurs and investors are seeing a $billion plus market for recycled feedstocks from end of life composites.

There was an article in Composites World that struck me as completely appropriate for our times. The Luxembourg Institute of Science and Technology (LIST) just opened their Sustainable Composite Materials and Manufacturing Innovation Centre. The LIST Centre is focusing on the transportation sector, and has 4 major players, Toyota, Airbus, Thales Alenia Space and Alstom (rail transportation). Their goals are to build the technologies necessary to introduce bio-based and recycled or recyclable materials into the top end of the transportation sector.

There is also a tremendous amount of work going on in the UK, specifically at the UK’s National Composites Center in Bristol. The NCC is focused in two areas of sustainability. They have entered into a partnership with the Centre for Process Innovation to develop new and better ways to recycle large composite structures that are coming to the end of their life – specifically wind turbine blades to start with (center right pic above). They are also developing new and carbon neutral materials like recycled carbon fiber and plant based phenolic and other resin systems to making new wind turbine blades that are either carbon neutral or eventually carbon sequestering – if made from plants.

And, of course, the major players in the US, like Boeing and all of its suppliers, are working on the development of methods of making composites more sustainable. Not only is it good for the environment, it can eventually become a profit center for companies that recycle composites and/or use the recycled fibers and resins to make new composites at a much lower cost and much lower energy expenditure.


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