Plastic composites – living up to the hype

Materials World magazine
5 Nov 2014

Plastic composites have challenges to overcome in order to live up to their considerable potential. James Perkins reports from Interplas, in Birmingham, UK.

The plastic composites industry is at an important juncture. Can these materials muscle in and take pride of place in the structures of next-generation cars? Their qualities are ideal, but right now they are expensive, slow to produce and difficult to recycle.

The aerospace industry has embraced plastic composites – both the Boeing 787 and the Airbus A360 are 50% composite. Carmakers have shown in prototype low-carbon vehicles (LCVs), such as Volkswagen’s XL1, that if they had the choice, the vehicle would be made almost entirely of fibre-reinforced plastic. But this is currently not realistic for affordable mass-produced vehicles.

Gareth Davies of Composite Evolution said the aerospace industry alone ‘is putting increased pressure on the supply chain’.

Dr Alan Wood, Principal Scientist at Victrex, Lancashire, asked the question in his keynote address, do high-performance thermoplastic composite materials have a future? The answer was yes, but Dr Wood said production needed to improve so that the end product did not need machining or trimming and could be stamped at a good rate.

Challenges to overcome include maintenance of fibre orientation through the thermoforming process, heat control while laminating the matrix, producing composites with varied thickness and reducing the amount of waste that needs to be cut from the material post-moulding.

Dr Wood said, ‘We need to make the benefits of composites a reality, rather than just saying that thermoplastics are beautiful.’

Recycling composites

Engineering natural fibres, such as flax and jute, to perform as well as carbon fibre will help solve the end-of-life dilemma for many composites. Davies said, ‘There is significant opportunity in the auto industry in the future for natural fibres. We are a long way from getting the function and form needed, but work is ongoing. There are environmental advantages to natural fibres, but customers are putting performance ahead of environmental concerns.’

Alex Edge of West Midlands-based ELG Carbon Fibre said the amount of composite waste poses ‘significant challenges for us as a business and as an industry’. There are about 18,000t of composites thrown out each year in the UK, and about 40t of laminate ready to be processed at the ELG plant alone. Metal contamination is a problem for the recycler, while sandwiched materials and those that use a honeycomb structure can’t be processed. He said, ‘We can’t recycle hybrid materials – there is no commercial value to fibreglass.’

Trusting adhesives

Knowledge and trust of adhesive technology needs to increase among engineers to take full advantage of plastic composites. One comment was, ‘If I seal it up, I don’t want people drilling through the fibre.’ The question is, can adhesive technology improve to the point where rivets are no longer required, even in risk-averse sectors such as aerospace? If it does, significant cost savings could be found in the manufacturing process.