Whether they are 100% recycled carbon fibre or hybrids blended with thermoplastic fibres, recycled materials are        cost effective solutions for automotive, rail or aircraft manufacturingWhy recycle carbon fiber?

 

Much of the research activities into composite recycling are focusing on carbon fiber. This makes sense because carbon fiber reinforced plastics are traditionally very difficult to break down or recycle. While thermoplastics can be melted and easily re-used, most composites are thermosets, which cannot easily be returned to their original materials.

In addition, global carbon fiber demand is estimated to more than double by 2020, to 150-180,000 tonnes. However, current manufacturing technologies are leading to almost one third of the overall carbon fiber

demand becoming waste during the conversion and component manufacturing phases. The remaining fiber goes into finished parts that that will have to be disposed of at end-of-life. As CFRP composites are now being used in components with shorter lives, end-of-life can be anything from two to 40 years.

According to ELG Carbon Fibre Ltd., who operate the world’s first and largest carbon fiber recovery plant, there are three main drivers for the recovery and subsequent re-introduction of recycled carbon fiber into the supply chain:

  • Affordability – Economic conversion of both manufacturing waste and end of life components into various recycled carbon fiber formats, technically suitable for many applications, makes lightweight carbon fiber composites more affordable.
  • Supply chain security – The use of recycled carbon fiber mitigates any supply side capacity risk by providing significant additional carbon fiber tonnage from existing production capacity.
  • Legislation and environmental responsibility – Carbon fiber waste can be recovered and converted to new products using less than 10% of the energy required to produce the original carbon fiber, fulfilling legislative and sustainability targets.

 

Recycling through acids...

One interesting example of the research taking place in composites recycling is the work conducted by a team from Washington State University, who have developed a promising way to recycle carbon fiber plastics.

Conventional recycling methods usually involve mechanically grinding carbon fiber products or breaking them down at very high temperatures or with harsh chemicals to recover the carbon fiber. However, the carbon fiber is often damaged in the process.

The team from WSU has developed a new chemical recycling method that uses mild acids as catalysts in liquid ethanol at a relatively low temperature to break down the thermosets. This method preserves the carbon fibers as well as the resin material in a form that could be easily re-used. They have filed for a patent and are working to commercialize their methods.

 

...or electrical discharge

This isn’t the only direction being pursued. Together with the Fraunhofer Institute and FHNW (Fachhochschule Nordwestschweiz), Swiss company SELFRAG is looking into how high voltage power fragmentation could be used to recycle aircraft components made from carbon fibers.

Basically it means applying an electrical discharge, similar to a lightning bolt, to the component to be recycled, such as an aircraft’s wings or fuselage. As it finds its way through the object to the negative electrode, the charge weakens or fragments the object along the natural material boundaries. This means that carbon fibers could be successfully liberated from other component materials in an energy efficient manner - without jeopardizing their strength or quality.

 

Recycling collaboration between China and UK firms

Meanwhile, in China, an interesting cooperation has been announced to develop lightweight composite components for the automotive industry based on recycled carbon fiber.

The collaboration involves Adesso Advanced Materials Wuhu Co. Limited (Wuhu, China) and ELG Carbon Fibre Ltd (Coseley, UK). The initial focus of the cooperation is to investigate how ELG’s recycled carbon fiber materials can be used to make applications for the Chery eQ1 electric vehicle.

The longer-term goal is to apply the knowledge gained from these projects in Chery’s conventional vehicles. A further possible result would see ELG Carbon Fibre establish a carbon fiber recycling operation in China when sufficient volumes of recycled carbon fiber materials are required.

 

A composites recycling guide

A good starting point for a company or individual interested in pursuing composite recycling is what is described as “the first guide to recycling composites” launched by French composite recycling collective CRECOF.

Co-financed by the French plastic and composite innovators IPC and the French Environment and Energy Management Agency (ADEME), the guide seeks to support manufacturers working with fiber reinforced plastics by providing answers to questions such as How can we recycle production waste? and Where can we find recycled raw materials?

The guide reviews current solutions for recycling composites, highlighting the strengths and limits of each and providing practical examples of projects. Solutions include grinding and reincorporation of glass-fiber composites and dry reinforcements; pyrolysis for carbon fiber from composites; the use of plastic materials as an energy source; the incorporation of glass fiber into cement; and emerging technologies such as vapor thermolysis or solvolysis.

 

Improving the sustainability of the composites industry

Recycling composites is now gaining traction, and rightly so. Modern aircraft, for example, are made increasingly out of carbon fiber – as much as 50%. Ten of thousands of aircraft are expected to retire in the next 20 years. Aircraft manufacturers are therefore gearing up for a new wave of recycling challenges.

And it’s not just the aviation industry; the use of carbon fiber in the automotive industry is also increasing - and cars have a much shorter life cycle than aircraft before needing recycling. Continuing investment in R&D is essential to develop better recyclable composites and recycling technologies for composite materials. This will contribute to the sustainable development of the composites industry.

 

Source: "Overview of the global composites industry" - New edition by JEC Group 

 

Written by Denzil Walton

Denzil Walton is a technical copywriter, editor and conference reporter. He has over 30 years’ experience writing on a variety of industrial and high-tech topics.

 

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