Creating a sustainable future for carbon fibre in manufacturing

Posted on 28 Sep 2021 by The Manufacturer

Iain Bomphray, Director at the Lightweight Manufacturing Centre (LMC), a specialist technology centre within the University of Strathclyde's National Manufacturing Institute Scotland (NMIS), talks about his team's work with carbon fibres.

Increasing demand for lighter products

As the world seeks to reduce CO2 emissions to meet environmental targets, there is a greater demand than ever for lightweight manufacturing, resulting in a growing need for materials such as carbon fibre across industries, including automotive and aerospace.

Iain Bomphray Director at the Lightweight Manufacturing Centre (LMC) - Courtesy of NMIS
Iain Bomphray, Director at the Lightweight Manufacturing Centre (LMC) – Courtesy of NMIS

Significant weight reduction can be achieved through the use of carbon fibre in manufacturing. According to research from Toray Industries, if all passenger cars and aircraft in Japan adopted carbon fibre to reduce weight and improve fuel efficiency, 22 million tons of CO2 could be saved. So far, so good; however, the high energy and fossil fuel-hungry production process associated with it is proving increasingly problematic as demand for fibre products increases.

Meeting this increased demand with a more environmentally friendly supply process is one part of the solution, but effectively reusing materials that would otherwise be destined for landfills is also extremely important.

A dual approach that involves improving the green credentials of the production process and new methods of recycling existing carbon fibre materials can make a big difference, delivering an effective, lightweight solution without the associated carbon footprint. This is exactly what we are striving to achieve at the Lightweight Manufacturing Centre (LMC), a specialist technology centre within NMIS, through two of our latest projects – FutureFibre and Sustainable Composites.

Our engineers and scientists have extensive knowledge and experience in polymer science and synthesis, fibre and composite production, fibre and composite mechanical testing, and fibre recycling from composites. We have the expertise on site and are already making strides towards developing a more sustainable approach to the production of composite materials.

FutureFibre – improving the carbon fibre production process

Carbon fibre is a remarkable substance that has become vital in producing a whole range of products where mechanical performance and weight reduction are essential requirements. From spaceships to golf clubs and jumbo jets to family hatchbacks, it is a versatile material with some impressive properties.

As is so often the case, however, there are downsides. Carbon fibre production requires significant amounts of fossil fuels and energy, with temperatures of up to 1000°C needed to create the fibre material. Not only is production highly complex, but it’s costly too, with carbon fibre up to 10 times more expensive than steel.

A climate crisis solution is high on the agenda for many manufacturers, particularly in the build-up to COP26 in November. With this in mind, the search for a more eco-friendly alternative to traditional fibre production is well and truly on.

While the research is still in the relatively early stages, the FutureFibre project here at the LMC has big aspirations. FutureFibre is a collaborative research and development project that aims to combine the experience of academics and industry professionals to provide the environment, infrastructure and resources to delve deeper into alternatives to the traditional fibre manufacturing process.

Sustainability - Shutterstock

Positive progress has already been made with more sustainable materials, with wood biomass showing promise, both in terms of sustainability and mechanical performance. Wood biomass contains lignin and cellulose, which can be used to produce polyacrylonitrile (PAN), one of the key industrial pre-cursors to carbon fibre production. It is more sustainable than fossil fuels and can use waste wood such as residuals from manufacturing, post-consumer waste and leftovers from timber harvest.

This is progress that we want to build on. Finding a more sustainable resource to replace fossil fuels will be the most crucial step in making carbon fibre production greener. Unfortunately, the unique chemical and mechanical properties required are not easy to find.

While wood biomass has shown significant potential within carbon fibre production, there are still challenges before it can be used as a workable alternative to fossil fuels in the production process. The high tensile strength of carbon fibre is one of its most valuable characteristics; however, it is also the most difficult to reproduce.

Unfortunately, the initial research shows the mechanical properties of wood biomass differ considerably compared to more traditional methods. Carbon fibre made using fossil fuels can achieve a tensile strength – the maximum load that a material can support without fracture when being stretched – roughly seven times stronger than when using wood biomass. We aim to develop these alternatives, improve performance and, ultimately, achieve a product for use in industry.

As with any undertaking of this kind, there are undoubted challenges ahead. However, our lab-scale production line is almost complete, and we are optimistic about the progress being made. It’s an exciting time and a vitally important area that we look forward to progressing with the result of, ultimately, making fibre production more sustainable.

Sustainable Composites – recycling fibres from composites

As the use of carbon fibre increases, so do the requirements for manufacturers to ensure the recyclability of their products. Using car production as an example, at least 95% of a new vehicle, by weight, needs to be recycled at the end of life. Without an effective solution for reusing carbon fibre, many carmakers could find it difficult to hit these targets.

Currently, 35% of carbon fibre ends up in landfills, with only 20% recycled. That figure gets worse when looking at glass fibre. However, recycling carbon fibre products use only 20% of the energy required to produce them in the first place – so why is more effort not being put into reusing old fibre materials?

The answer lies in the mechanical properties of the material that initially emerges from the recycling process. The first stage of recycled carbon fibre typically resembles rough wire wool in terms of the random alignment of its fibres. This new material lacks that all-important tensile strength that makes carbon fibre such a valuable product. However, this initial wool-like material can then be processed into something that closely resembles traditional carbon fibre in terms of appearance and performance, regaining many of the properties required for industrial use.

As part of the Sustainable Composites project at the LMC, we plan to scale up the current novel process to pilot scale as soon as possible. We would welcome industrial partners to join this project, including complex manufacturers and material suppliers, to monitor the full impact of the recycling process. Using life cycle analysis and cost modelling related to specific industrial requirements, we hope to establish a closed-loop system for carbon fibre that will see the material recycled and reused rather than discarded.

A combined approach

The benefits of carbon fibre are clear to see, and the product can undoubtedly help reduce CO2 emissions as more and more industries look to reduce weight and improve efficiency. However, as demand continues to rise, we must explore every option available to us to reduce the environmental impact of the production process. A combined approach is essential here, and there is no one correct answer. What is clear is that increased recycling and a more ecological approach to production could see meaningful improvements made to our efforts to reduce emissions.

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