Closed loop system for carbon fibre
The demand for carbon fibre-based composites is growing, particularly in aerospace, prompting the need to look at ways to recycle and reuse carbon fibre in a closed loop system.
In 2006, a year before the launch of the Boeing 787 Dreamliner, Boeing teamed up for the first time with suppliers and waste managers to create a materials closed loop through the Aircraft Fleet Recycling Association (AFRA). Carbon fibre featured strongly in the discussions, and Milled Carbon, in West Bromwich, UK, is one of the partners benefiting.
The company is developing a continuous carbon fibre recycling process and plans to commission a plant in spring 2008, that will process one tonne every eight hours by pyrolysis treatment.
Few companies have tried to recycle carbon fibre because of the perceived technical difficulties and a lack of demand. Aircraft recyclers are, in any case, thin on the ground.
Now that carbon fibre demand is increasing, and more aircraft are coming out of service, interest is growing. Raw material is plentiful in the form of manufacturing offcuts as well as end-of-life scrap.
According to research from Netcomposites, a global research, consultancy and online media company, carbon fibre manufacturers will invest over US$800 million over the next three years, raising capacity by 78%, while aerospace currently makes up 28% of the end use share. Milled Carbon receives between 1-15t each month from sources worldwide. Managing Director John Davidson describes this as a ‘drop in the ocean in terms of what’s out there’.
The company is in a good position financially, receiving free scrap but selling material from its pilot process at £7-10/t.
One of the industry’s goals is to reuse carbon fibre from aeroplanes in aircraft production. At the moment, Milled Carbon, Boeing, and other producers envisage that accessories, such as door handles and food trays, rather than the fuselage, will be the most likely applications for the shorter fibres. However, they are considering substituting a steel inner C-shaped section in the aircraft’s structure for carbon fibre recyclate. Independent tests have shown that recycled carbon fibre has at least 90% of the properties of virgin material.
However, Milled Carbon’s primary market is not the aircraft industry. Instead, carbon fibre recyclate can go into injection moulding, fuel cell plates, non-wovens, tyres, paint, car panels and disc brakes.
The technical challenges are considerable. Lack of knowledge of the content of scrap is a conundrum, and this may be withheld from recyclers for competitive reasons. Different types of resin affect the treatment choice (chemical or heat), while the presence of fibreglass, Kevlar and aluminium, as well as the thickness of the material, are also considerations.