Composites set to benefit transportation industries

Introducing exotic materials into industries where metallic's have ruled is an ongoing challenge for the composites sector. The materials' inherent low-density has always been its best selling point.

Though composites have become synonymous with performance, it's the superior strength-to-weight ratio and parts-consolidation capability that is able to offer dramatic reductions in weight, which ultimately enables performance benefits to particular vehicles and systems.

Composite, as a material type, is more varied than any traditional engineering material. And the fact that composites can, and should be, tailored to an application means that it's far from straightforward to design and manufacture.

Though this makes many hesitant, the overwhelming need for all kinds of transport systems to improve efficiency has seen its application trickle down from low volume aerospace to higher-volume automotive uses. With this in mind, the composites sector has now set its sights firmly on the rail industry.

And the UK is well placed to exploit the potential advantages given the number of rail projects on the table, from High Speed 2 to Cross Rail and even new rolling stock for the Underground.
Finding application

While there has been some fairly niche application of composites in the rail industry already, a recent event set up by Composites UK, 'Composites in Rail Infrastructure', set out to increase interest for future projects.

"We are getting a lot of interest from the rail sector around composite materials, in particular for lightweighting," says Darren Hughes, assistant professor in materials and manufacturing at the Warwick Manufacturing Group, part of the High Value Manufacturing Catapult. "A project has just started looking at making a lightweight bogie structure using composites. And bridges are another potential area where composite structures can replace steels and even aluminium. But there are questions around how to join them with other materials, form them, manufacture them, and test them. And in particular, the rail industry wants to produce at a similar cost level to the automotive industry."

The event primarily set out to build confidence, in rail engineers and purchasing managers looking to specify composites, by dispelling many of the myths over its cost and manufacturability. And a key message was composite design usually requires experience, and that means perhaps a closer working relationship with material suppliers than rail engineers are typically use to.

Julian Smith, engineering director at Fibre Content, says: "It can be difficult to design composite parts and structures effectively. You can easily be wowed by some of the properties but you need to do cost engineering to get the most out of the materials. So you need to be clever with your application and design. It is complicated to select the right fibres and resins, which may all use different processes and tooling.

"It is specialised, but it is not a black art. It is not mysterious or risky, but it does need that experience gathered from working with earlier adopters in aerospace and automotive. If you design it properly it can be cost effective, use low cost tooling and have a good surface finish that stays looking good. And you don't have to have the same properties in every direction, and if you do, the other properties may dilute out a bit.

"Given the composites base there is in the UK, it should be no problem engineering and supplying composite components for the rail industry."
Composite crossroad

Future rolling stock and infrastructure in the UK is at a materials crossroad. There is genuine interest from the rail sector to lightweight, increase efficiency and better exploit lighter and more exotic materials. The rail sector knows it is behind the materials technology curve compared to other industries and wants to see improvement in the projects now coming through.

Application of composites can aid the aerodynamic performance of high speed train systems as well as reduce the energy needed to acceleration and deceleration those commuter trains travelling shorter distances with more stops.

The aim is to help make the whole system become more economical and efficient, from the energy needed to provide forward movement to reducing the wear on the tracks and infrastructure maintenance.

Getting it done
Composite implementation for rail is the same as it has been for every industry in that it can't be just about lightweighting. System wide benefits from maintenance to operating costs must all be assessed and balanced.

"The rail industry has a requirement for lightweight structures with good fatigue performance, low overall maintenance, fire resistance and better acoustic performance," says Chris Monk, engineering manager at STRUCTeam. "So, you can quite quickly see composites are a very good fit.

"If you look at aerospace and automotive who have led the way on this, they have shown that you can navigate your way from traditionally metallic structures to composite applications, so clearly it can be done."

There are of course barriers to entry, one perhaps more abstract than practical, is about clearly understanding the commercial proposition that composite materials can offer. But, that is often far from straightforward and is about convincing those holding the purse strings.

For example, the wind turbine sector is moving to carbon fibre from glass fibre to make its blades. From a project management perspective this adds expensive. However, a reduction in blade weight reduces the structural costs of the tower, allows the blades to be made bigger, yields more energy, and as a system reduces implementation, operating and maintenance costs.

"For the rail sector it is more difficult to see exactly what the value chain is and who gets the benefit," says Monk. "The franchised business models at the moment would see people and organisations that invest upfront in the benefits of a composite structure not always reap the rewards later on in the life cycle."

Identifying the business case is closely linked to identifying parts, components and even systems that are most advantageous to be made out of composites.
Composites can't do everything

Like any material, composites have their own set of advantages and disadvantages that must be considered during material selection.

These lighter materials tend not to be as tough as steel or aluminium, particularly with regards to impact damage as well as not lending themselves to overly complicated joints. While they can be made to work, sometimes other materials maybe more suitable. So identifying the components that would benefit most from the properties of composites is key.

"But, it's not always straightforward whether it is or isn't," says Monk. "You sometimes need that degree of experience to make the assessment.

"The materials are very tuneable and that sets the commercial basis. You have lower grade glass fibre with polyester resin, to expensive carbon fibre epoxy prepregs, both are used by the marine industry, for example, just for different applications. So you need to get that balance of performance against cost.

"And the lifecycle cost breakdown can be quite different compared to traditional metallic structures. This is something the purchasing community within the rail industry needs to start recognising, so they can see where the benefits are later on."

A challenge for the rail industry is the relative lack of experience in the design and engineering of composite parts, so there is a steep learning curve ahead. However, many important lessons can be learnt from the aerospace and automotive industries, which have had far from an easy journey in their increasing uptake of the materials. Rail engineers must take heart from these early adopters that are still finding their way through many new technical challenges, but get real benefits from composite application.

"The supply chain is ready," says Monk. "It has been ramped up over many years, it's ready for automotive and for aerospace and it's ready for the rail industry. But there needs be some good dialogue and a pragmatic approach to identify the applications and get the rail industry onboard."

Lighter rail not just for the UK
Many of the large OEMs associated with train manufacture are embracing composites including Siemens and Bombardier, and there are also significant projects underway looking at the future of rail systems such as Revolution VLR, a consortium of UK companies looking to develop the next generation of technology.

But it is not solely the UK that has its eyes on the future. German based Voith has recently highlighted a number of potential applications for composites from drive components, couplers and service concepts to other lightweight solutions, among them the modular front nose of the new German ICx high speed train.

The front nose replaces what use to be made of steel helping reduce fuel consumption, minimising axle loads and track wear, as well as actually allowing capacity to be increased. The front structure can also be made in one piece to help reduce manufacturing and assembly time, as well as improving aerodynamics.

Another example is the energy absorber made of glass fibre reinforced plastics (GFRP) that weights only one third of the standard steel absorber. Apart from its fibre composite crash tube, the absorber comprises a bearing and an anti-climber plate, both made of aluminium. The components excel in longevity, and they offer constant energy absorption behaviour even when the absorbers meet at an offset. Weighing 70 to 95kg, a 60% weight reduction is achieved compared with standard steel absorbers.

Adapter couplers have also been identified. These are mainly used for towing operations of failed trains, and every train has to have at least one of them on board. The CFRP (carbon-fibre reinforced plastics) adapter coupler developed by Voith is extremely compact and has a total weight of only 23kg.

Where two people were necessary to fit an adapter coupler on the train, this one can be carried and mounted by one person alone. First practical tests in the market were successfully concluded.

Justin Cunningham

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Do you have any comments about this article?
Great article and well balanced points to consider from a sales and promotion point of view.
Great read thanks bill

Comment William Bolton, 06/10/2014
With the number of rail journeys increasing in the UK, and the cost of operating the network estimated to be over £10 billion a year, keeping track maintenance at a minimum is essential so it’s great that composites are starting to get looked at for practical rail applications.

Comment Tim Britt, 06/10/2014

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