Carbon-fibre composite frame braided for very light rail

Materials World magazine
1 Jul 2019

A braided composite frame is one of several components created as an initiative for a new, lightweight, low-cost rail system in Coventry. Shardell Joseph reports.

A project to create a new rail system in Coventry, UK, has developed the latest component – a braided frame made from carbon-fibre composites. Made for the body of electric tram-style carriages, the composite frame will be used instead of more traditional steel frames, making it lighter, cheaper and easier to assemble.

The composite frame was designed by Warwick Manufacturing Group (WMG) researchers at the University of Warwick, UK, with composite components company Far, and Transport Design International (TDI). The researchers constructed the frame using a series of tubes that can be easily erected with adhesive and basic welding techniques.

With the aim to develop an affordable and lightweight rail system, the braided frame is an essential part of the very light rail (VLR) service, which is aiming to carry approximately 50 passengers, while reducing the amount of energy required to propel the vehicle. The frame will also help lower the weight stress the vehicle places on rails and road surfaces.

‘What we are doing is using a lighter load, low-cost composite solution,’ University of Warwick Associate Professor of Materials and Manufacturing, Darren Hughes, told Materials World. ‘Carbon-fibre composites offer significant potential in terms of lightweight, and the idea is to make the frame lighter. So we’re replacing the steel frame with a composite lightweight frame.’

According to Hughes, using carbon-fibre composites is not only a lighter alternative to steel, but is stronger. ‘We’re creating a multi-directional material. The fibres are woven together, giving it strength in different directions. The specific strength - strength per unit mass - of a carbon-fibre composite is higher than steel generally. So it means you can build the same structure with the same strength, but it is lighter.’

The researchers used an underlying tubular space frame chassis to build the frame. ‘Rail vehicles generally have what is called a ladder chassis. So it looks like a ladder, and the frame is what is up in the body, which then has the body panels on it,’ said Hughes. ‘Essentially, all vehicles follow that type of design.’

The tubes or beams have been designed so they can be easily removed and replaced, in the event of being damaged through accidental impact. According to the researchers, the parts of the frame use a thermoplastic material, motivated to making the new rail recyclable and eco-friendly.

The VLR project

The braided frame is just one component of a broader initiative set by Coventry Council to create a quieter, more environmentally friendly and cheaper rail system than at present. According to WMG, the system could significantly reduce the cost of rail construction – potentially costing just £7mln/km in contrast with Edinburgh’s rail system that cost approximately £80-100mln/km to build.

Looking to transform tram-style travel, the vehicle will be electric-powered and designed with the view to being autonomous in the future. Coventry Council and WMG aim to have the VLR demonstrator completed by 2020, and ready to use by 2024.

As a collaboration between WMG engineers and researchers, alongside TDI, the project has secured more than £14mln from the West Midlands Combined Authority Devolution Deal and Coventry and Warwickshire Local Enterprise Partnership Growth Fund.

‘WMG have expertise in the automotive industry, and what they are doing is adapting the types of unique revolutionary materials developed for the automotive industry,’ Cllr Jim O’Boyle told Materials World.

The VLR project is Coventry’s plan to tackle the rail sector’s four C’s challenge – cost to be halved, capacity to be doubled on key routes, carbon emissions halved, and customer satisfaction to be increased from 90-99%.

The VLR is also expected to use the lightweight materials to increase the capacity and speed of rail.

Since the start of the project, there has been considerable amount of interest in the technological designs of the VLR and its potential. On completion of the braided frame prototype, Parliamentary Under Secretary of State and Minister for Business and Industry, Andrew Stephenson, visited WMG to see the design. Because of the VLR’s potentially large-scale economic and environmental benefits, it is expected by both WGM and Coventry Council that the technology will soon be adopted elsewhere.

‘We’ve already had interest from other parts of the country, and we think there is absolutely a market for it going forward,’ said Hughes.

O’Boyle explained, ‘We really believe this is innovative, and people want to see it, because people are looking for cost-effective new forms of public transport, particularly in the drive to improve quality and make sure that we meet our climate change targets as well.

‘It ticks a lot of boxes, and I think a lot of cities will want to look at the traditional tram as hellishly expensive, and see that new technology is becoming potentially affordable in the future.’