Opportunities for composites in rail

Ask a member of the general public what composites mean to them, and what they are used for, and you are quite likely to get the answer ‘Formula One’.

Which is a correct answer. Formula One race car chasses are made from a composite material – carbon fibre. As you would expect given its usage, they are constructed from a very high-tech composite. Sheets of woven carbon fibres, pre-impregnated with epoxy resin, are cut to shape and carefully laid up into moulds, with the various layers orientated with the weave in different directions.

The finished component is then wrapped into a plastic bag and placed in an autoclave, a high-pressure oven, where it is ‘cooked’ at between 120 and 180°C and at a pressure of around 6 bar (six times atmospheric pressure or 87 pounds per square inch).

The pressure and temperature activate the epoxy resin to produce the finished high-strength and lightweight laminate.

This is all very complex and expensive but is basically the same process that anyone doing repairs to their cars uses to produce fibreglass. The glass-fibre mat is placed in position and the epoxy resin, with the hardener mixed in, is then applied using a paintbrush to soak the fibres. When the hardener goes off, the result is glass-fibre reinforced plastic (GRP) – another composite.

In fact, a composite is just one material that is made up from a number of other materials. The Cambridge Dictionary defines a composite as “a material made up of more than one substance that is used for building things”. Carbon fibre is a composite (carbon and epoxy resin), as is fibreglass and other fibre-reinforced plastics (FRP). It’s nothing new – plywood is a composite, as is chipboard with a wood veneer coating.

Composites are used for many applications, most of them not nearly as demanding in terms of technology as world-class motorsport. Many of the components of a train are composites of one sort or another.

The complex shape of the driver’s cab at the front of many passenger trains is possible due to it being moulded from composite materials. There are strong metal structures underneath for safety and crash protection, but the smooth, curved exterior is a composite moulding.

So too are the interior wall panels, the ceiling, and even the doors.

The flat sides of the carriage are also quite likely to be a composite, though one of a different form. Many coach bodyshells are made from two flat sheets of aluminium sandwiching and bonded to an aluminium honeycomb core that adds bulk and stiffness but keeps the overall panel light.

With the sheer number of applications in rail that utilise composites in one form or another, it is little wonder that the industry was attracted to the recent International Composites Summit, held over two days at the Marshall Arena in Milton Keynes. The Railway Industry Association (RIA) organised a short workshop on the morning of the second day, entitled “Composites in Rail: Challenges and Market Opportunities”.

Sam Bemment, RIA’s technical and innovation manager, hosted the session, which highlighted the wide range of applications that already exist for composites in rail as well as developments that are still being undertaken.

Revolution

Eversholt Rail is one of the three rollingstock-owning companies established when the former British Rail was privatised. Since 2015, the company has been owned by the Hong Kong-based CK Hutchinson and CK infrastructure group. Eversholt Rail’s core business is the acquisition and through-life management of a large and diverse portfolio of passenger rolling stock and freight locomotives, which it leases to UK passenger-train and freight operators.

Eversholt prides itself on being a proactive asset manager, working closely with its customers and suppliers to ensure that its trains meet their ever-increasing market expectations. As part of this activity, the company has a long history of investing in innovative new products and supplies.

Tim Burleigh, head of external relations at Eversholt Rail, described the Revolution Very Light Rail Vehicle (RVLR). The use of composites has played a key role in the development of this vehicle, a novel and low-cost, lightweight alternative to conventional heavy rail vehicles that is targeted at stimulating line re-openings and achieving improved connectivity, particularly in rural areas.

Lightweighting is absolutely fundamental to minimising the cost of operation, Tim explained. The lighter the vehicle is, the less energy it requires to propel it and the less wear it causes to the track and infrastructure on which it runs. Very light rail solutions can also operate on lighter, simpler track forms. The design must be balanced, however, and low vehicle mass must not be achieved at the expense of robustness and reliability.

The use of composite materials for the body on a lightweight, welded steel, ladder frame, and the adoption of a modular design that uses five identical panels to form each side of the body structure, has resulted in a 19-metre-long vehicle capable of 65mph (105km/h) and of seating 56 passengers.

Composites are also used in the drive train, which is 50% lighter than an all-steel equivalent would have been, and 70% of the components in the demonstrator vehicle have been sourced from the UK supply chain, supporting UK employment and minimising the net carbon impact of its manufacture.

The demonstrator is currently under test on a line at Ironbridge in Shropshire.

Infrastructure

Jonathan Howard, head of growth for Dura Composites, spoke of applications for composites on the railway’s infrastructure. “We’re starting to see a cultural change around innovative solutions when it comes to overcoming the big challenges to upgrade and renew the rail industry,” he told his audience.

“The big factor is a new focus on slashing time and slashing costs. Using materials like composites, which are lightweight, we can demonstrate we are able to reduce time on site and time for delivery, but we are also looking at saving time in terms of maintaining that solution.

“We’re also understanding that minimal viable product is being considered for certain applications, where we’re now providing end solutions which are not being over engineered, are not being over specified, but are achieving the client’s end goals.”

With 50% of the railway’s embodied carbon being in its infrastructure, a new focus is being given to whole life carbon costs, not just the carbon content of the material itself. So, lightweight materials, which can be installed without the need for heavy diesel-powered machinery and don’t involve the use of concrete – another high-carbon product – has resulted in carbon reduction of up to 47% on some projects.

As part of a recent project on the Isle of Wight, contractors Hammond and PodTrak installed nine station platforms in 13 weeks. The platforms were built off-site and then delivered and installed by hand. In addition, due to the lightweight platform surface, the quantity of steel in the substructure could be reduced. This reduced the weight of a six-metre section of platform from 26 tonnes for a traditional concrete trestle to 2.5 tonnes for a composite and steel structure.

There are many other applications for composites. Jonathan briefly listed some of them – drainage systems for train washes that reduce the amount of water being dumped on the track, fencing and safety barriers, walkways and permanent formwork for use when cast concrete is the best solution.

Train refurbishment

Lewis Melia, Key Accounts Manager at Gemini Rail, spoke on his own behalf about the use of composites for train refurbishment. These usually call for a train’s interior to be refreshed, with new seat covers and carpets, new LED lights, upgraded Wi-Fi and other improvements. This is a very time and cost-sensitive operation, and there is a very short window to refurbish a train as the train operator wants it back in service as soon as possible.

There is therefore little time to replace internal components with composites, although many of those items – interior wall and ceiling panels, grab handles and poles, toilet fittings and interior doors – are already of composite construction from when the carriage was first built. A coat of paint and some in-situ repair may be all there is time for during a refurbishment.

However, the wider rolling-stock market, including both mid-life retrofits as well as new build, is working hard to reduce weight and increase the use of composite materials. New vehicles have to be around 20% lighter than the trains they are replacing, as operators strive to reduce both fuel costs and track access charges.

So, lighter materials are being investigated for everything, from running gear to tables, while standards in terms of fire protection and accident resilience are becoming increasingly demanding. Leadership from the top is essential so that manufacturers can reduce weight and carbon while still meeting the various standards and specifications that are imposed on them by the industry’s governing bodies.

Materials

The final properties of any composite material, whether those be weight, strength, or fire resistance, depend largely on their component chemicals. Tom Kugelstadt is group head of technical support at Scott Bader, a global manufacturer of advanced composites, structural adhesives and functional polymers that has been employee-owned since 1951.

The company has manufacturing sites around the world, and this allows it to have close relationships with both component and train manufacturers wherever they may be operating. Furthermore, the ownership model “allows us to be very stable in our long-term thinking and to form great partnerships with our customers and suppliers. This is particularly important for rail, where we need to form long relationships and trust at multiple levels in that chain,” Tom commented.

Previous speakers had already listed a number of applications for composites on a train. design flexibility, scalability, manufacturing processes, corrosion resistance, and strength-to-weight ratio. The requirements for a composite on the nose of a train, constantly facing high speeds and air resistance, are very different to the material used for the side skirts, or for interior mouldings or the flooring within the train. So, it’s not a case of just having one composite solution for rail, it has to be tailored for the specific application within the train, which makes choosing the correct material quite complex.

One of the main things that differentiates rail requirements from many others is the need for fire protection. Globally, the industry seems to be adopting the EN45545 standard, not just in Europe but elsewhere. But Tom’s key point was that everything that goes into the final composite configuration – the combinations of resins, coatings, fibres, foam cells, inserts – all need to come together and still deliver the right level of fire performance for the final component.

As well as fire resistance, weight and strength, there are other considerations such as the method of manufacture, the required UV resistance, the level of surface gloss finish, the use of anti-graffiti coatings and cleaning materials, all of which complicate the designer’s final selection.

Research

Unsurprisingly, much research is being carried out on the use of composites for various rail applications. The University of Huddersfield’s Institute of Railway Research is a Centre of Excellence in Rolling Stock as part of the UK Rail Research Innovation Network. Senior research fellow Samuel Hawksbee outlined some of the work being done on the use of composites in train and locomotive running gear.

The Carbon Fibre Bogie project (CaFiBo) aims to match the properties of existing steel bogies, including the location and functionality of existing pickup points for brakes, suspension and drive train, while achieving a 36% reduction in mass. A prototype bogie, manufactured using a nonwoven carbon fibre mat material made with 100% recycled carbon fibre, has been tested using the university’s Huddersfield Adhesion and Rolling Contact Laboratory Dynamic (HAROLD) test rig that can simulate running at 125mph (201km/h) and is still performing well after eight million cycles.

A carbon-fibre axle (CaFiAx) is also under development in an 18-month joint project with the University of Nottingham and ACS-Australia (Advanced Composite Structures) to minimise track impact damage by reducing the unsprung mass of the axle and to cut CO2 emissions. The idea is to develop a demonstrator prototype that can be taken forward into testing.

Leadership forum

To round off the formal presentations, Dr Faye Smith, chair of the Composites Leadership Forum (CLF) Strategic Engagement Group, explained that the CLF was established in 2009 as a result of the UK Composites Strategy to strengthen leadership in the sector. Its objective is to convene industry and support bodies to understand industry needs and to lobby for and direct support and effort to ensure growth and industrial success for the UK composite sector.

“The CLF was set up because if you’ve got a strategy, you need a body to keep looking at it,” she told delegates.

Working groups have been established looking at the need for and use of composites in aerospace, defence, automotive, rail, construction, marine, oil & gas, and renewables. The aim is to deliver growth in sectors already using composites through increased productivity, to develop technologies and supply chains for high volume, lower cost production, to establish the capability to manufacturing large structures and so increase the use of composites in other sectors, and to help deliver the green revolution through sustainable, low-carbon, composite solutions.

Dr Smith finished by appealing for volunteers to join in the work of the CLF and help the industry to work together on the future.

Final questions

The panel assembled to take a few last questions. Andy Blake of the National Composites Centre introduced himself and sought to connect with others operating in the composites field. He also discussed a Network Rail contract to encourage the use of composites on railway infrastructure.

Richard Brine of Elemy suggested that discussions should be looking forward to the future rather than looking back at past trends. His company is currently manufacturing 34 structures such as footbridges and rail should be adopting modular design that can be used, in one form or another, almost anywhere on the network.

The UK currently is very quiet in terms of rolling stock orders, and therefore for the composite components that those trains would contain, and a discussion took place on the need for more orders as part of the government’s decarbonisation strategy. RIA has recently published a report on “The UK Rolling Stock Industry: Making 2023 the year of opportunity not crisis” and this strategy was supported by delegates as a way of smoothing out the ‘boom and bust’ procurement policy, creating conditions for increased productivity and reducing whole life cost.  After a couple of discussions on cost, risk, and return on investment for train operators, Sam Bemment thanked delegates and the panel for their participation in a most interesting morning event and released them to have a look around the main exhibition.