Composite Materials in the Rail Industry

For over sixty years, TRB have been making use of lightweight composite materials to deliver innovative solutions. TRB’s lightweight aluminum honeycomb composite sandwich panels and bulkheads were part of the Bluebird World Land Speed record car driven by Donald Campbell in 1964. TRB’s lightweight aluminum honeycomb composite sandwich panel was used to construct a monocoque chassis for the1970 World Championship winning Lotus Formula 1 car.

The London Underground District Line trains launched the first production trains fitted with lightweight aluminum honeycomb composite doors in the United Kingdom in 1978. The Team Antarctic solar vehicle is the latest example that was made almost from lightweight composite panels.

Need for Weight Reduction in Rail Vehicles

Increasing passenger requirements, including universal access toilets, CET tanks, power sockets, air conditioning, more tables, tilting mechanisms, improved crash structures and crumple zones, and alterations to the seating regulations, are making trains heavier. For example, compared to a 1970’s Mk 3 rolling stock carriage, the year 2000 Bombardier Voyager train was 40% heavier. The train weight cannot continue to increase. Body shell, external doors, bogies, HVAC, couplers, drivers cab, interior linings, interior doors, and passenger interior including seats are the key areas for weight reduction using composites (Figure 1).

Body shell, HVAC, external doors, bogies, couplers, interior doors, drivers cab, interior linings, and passenger interior including seats are the major areas for weight reduction using composites.

Figure 1. Body shell, HVAC, external doors, bogies, couplers, interior doors, drivers cab, interior linings, and passenger interior including seats are the major areas for weight reduction using composites.

Current Successes in Weight Saving in Rail Vehicles

The mass of Bombardier’s new AVENTRA platform to substitute the Electrostar is in the range of 30-35 tons, a reduction of 17% to 28% when compared to previous designs of 42 tons. Furthermore, the new platform consumes 50% less electricity than the Class 319 equivalent and facilitates reduced journey times. The weight of latest Desiro City platform from Siemens is 25% less than the average existing UK fleets and consumes 50% less energy using regenerative breaking, energy efficient lighting, and much more.

Another example is the new generation commuter train for the UK, Alstom X’Trapolis, which claims to have a weight 28% less than the average UK fleet and 50% less energy consumption through the use of lightweight composites and regenerative braking systems as well as by using energy judiciously.

Options for Further Cost Effective Weight Savings in Rail Vehicles

Composite seats, composite doors using fibrous composites, stand backs, ceiling panels, cab fronts and body ends, body side panels, and floors with increased functionality, including floor covering, heating, thermal/acoustic insulation, and easier cleaning options, are the other areas to accomplish further cost-effective weight reduction in rail vehicles.

Alternative Lightweight Composites Materials to Meet Rail Industry Demands

The alternative lightweight composites materials to solve the rail industry demands in the coming years include phenolic SMC (sheet molding compounds), modified epoxy glass pre-preg that complies with the newest EN 45545 fire standards, carbon/phenolic pre-pregs, fire retardant foam cores, and the latest thermoplastic materials with good FST properties. Compared to monolithic composites, there are several lightweight core materials capable of providing stiffness and lowering complete panel weight. Balsa, Nomex honeycomb, aluminum honeycombs, foam, and cork composites are few of the examples for lightweight core materials (Figure 2).

A number of lightweight core materials can assist in providing stiffness and reduce overall panel weight compared to a monolithic composite.

Figure 2. A number of lightweight core materials can assist in providing stiffness and reduce overall panel weight compared to a monolithic composite.

New Potential Advances in Composites for the Rail Industry

Although natural fiber and bio-resins reinforcements are in the emerging stage, they can solve the FST requirements for rail applications, according to initial tests. The XMTM30 resin system from Cytek is a bio-renewable sustainable source complying with the specifications of EN 45545 category HL3. It can create a truly bio-sustainable system in combination with natural fibers. Cytek MTM® 348FR is another product complying with the requirements of EN 45545 category HL2. Cytek MTM® 348FR and XMTM30 are suitable to fabricate lightweight composite components for both interior and exterior structural and non-structural applications.

Lightweight aluminum honeycomb materials are lightweight alternative solutions to conventional materials such as plywood. Lower refurbishment costs, longevity particularly in wet areas, and increased loading per sq/m for given support spacing are the key benefits of lightweight aluminum honeycomb floors (Figure 3).

Lightweight aluminum honeycomb floors

Figure 3. Lightweight aluminum honeycomb floors

Aluminum honeycomb bonded structures are lightweight substitute to conventional materials, including metal fabrication, plywood, and aluminum casting, for use in external and internal doors (Figure 4). Lower inertia during operation, recyclable at end of life, and lower demands on the operating mechanism due to lightweight factor are the key advantages of aluminum honeycomb bonded structures.

Aluminum honeycomb bonded structures are lightweight alternative to conventional materials, including plywood, metal fabrication, and aluminum casting, for use in internal and external doors

Figure 4. Aluminum honeycomb bonded structures are lightweight alternative to conventional materials, including plywood, metal fabrication, and aluminum casting, for use in internal and external doors

Aluminum honeycomb can replace plywood and metal fabrications in saloon partitions and draft screens. Easier installation due to the lightweight factor, recyclable at end of life, less prone to altering moisture conditions, and increased available passenger space because of reduced thickness are the benefits of aluminum honeycomb.

In window pans, phenolic pre-pregs and phenolic SMC can substitute traditional materials such as wet layup and GRP with or without honeycomb cores as seen in Figure 5. Their main advantages include enhanced weight control, more consistent thickness control, better tolerance control, and reduced painting/finishing time because of improved surface finishes. Most recent phenolic pre-pregs and thermoplastics can be used instead of metal fabrications and wet layup GRP as lightweight alternative in stand backs (Figure 6). Less re-work due to tighter tolerances, enhanced surface finishes, and lighter weight are the main advantages of these lightweight materials.

Phenolic pre-pregs and phenolic SMC can replace traditional materials such as wet layup and GRP with or without honeycomb cores in window panes

Figure 5. Phenolic pre-pregs and phenolic SMC can replace traditional materials such as wet layup and GRP with or without honeycomb cores in window panes

Latest phenolic pre-pregs and thermoplastics can be used in place of metal fabrications and wet layup GRP as lightweight alternative in stand backs.

Figure 6. Latest phenolic pre-pregs and thermoplastics can be used in place of metal fabrications and wet layup GRP as lightweight alternative in stand backs.

Aluminum honeycomb composites can be a lightweight substitute to GRP wet layup in toilet module/cabin as seen in Figure 7. Adaptable without high tooling expenses for new design/configuration or alterations, option for multiple finishes such as hpl, Novagraph/decals, paint, significant weight reduction of up to 100 kg, and recyclable at end of life are the key benefits of these lightweight materials. Aluminum honeycomb composites can also offer lightweight alternative solutions to plywood and metal fabrications in galleys and catering units as shown in Figure 8. Longevity, wide selection of finishes, better fire performance, and easy installation because of lightweight are the main advantages of using aluminum honeycomb composites.

Aluminum honeycomb composites can be a lightweight alternative to GRP wet layup in toilet module/cabin.

Figure 7. Aluminum honeycomb composites can be a lightweight alternative to GRP wet layup in toilet module/cabin.

Aluminum honeycomb composites can also provide lightweight alternative solutions to plywood and metal fabrications in galleys and catering units.

Figure 8. Aluminum honeycomb composites can also provide lightweight alternative solutions to plywood and metal fabrications in galleys and catering units.

Conclusion

Lighter trains and minimal load through the use of lightweight structures are beneficial to have lower access charges because of minimized rail wear and infrastructure damage. Optimized corrosion resistance, reduced energy requirements, lower running costs, and faster journey times are the other plus points. Also, placing the mass in the correct position can enhance ride and passenger comfort.

This information has been sourced, reviewed and adapted from materials provided by TRB Lightweight Structures Ltd.

For more information on this source, please visit TRB Lightweight Structures Ltd.

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