On the right track

Mike Richardson hears how the railway industry is keeping track with the recent developments seen in aerospace industry to promote the design and manufacture of lightweight composite structures for use in rolling stock. Honeycomb sandwich panel technology has been around since the 1950s and while it’s considered an established technology, its construction of two outer skins either side of a core substrate which provides a lightweight rigid panel is still relevant today.

Huntingdon, Cambridgeshire-based TRB Lightweight Structures design and manufacture bespoke assemblies, bonded structures and composite components based on lightweight honeycomb sandwich panel technology. These products are used extensively in the rail, aerospace & defence, marine and automotive industries.

“Over time, TRB has successfully developed the business to service all major sectors within the rail industry,” begins the company’s technical sales manager – aerospace & defence, Terry Mayston. “The company has now progressed to a point where we offer complete TRB designed, validated and manufactured train doors as ‘plug and play’ solutions. The rail industry hasn’t quite reached the evolutionary stage of building train carriages entirely from composite materials, but gradually a number of interior structures, doors, flooring and interior panelling are increasingly migrating towards the use of lightweight composite materials.”

More than a feeling

Mayston notes that while the aerospace industry has increased its use of carbon fibre-based composite materials, the rail industry tends to prefer the ‘feel’ of metallic materials. Perhaps it’s just a case of old habits die hard?

“Whilst there are many similarities between the two industries, in essence both aerospace and rail require a rigid, lightweight structure, and whether it’s a galley on an aircraft or a train, the principle is the same. There may be variations in terms of the core and skin selection, but the rail industry seems to prefer a metallic aluminium skin product. The aerospace industry is different: it prefers fibrous skins with Nomex or foam core products, but ultimately it really depends on the application.

“We provide assistance to customers by helping them reduce component weight, whilst still offering the optimum mechanical properties. The rail industry is keen that our products help minimise any additional weight requirements in both new build and refurbished trains.”

Another area where parallels can be drawn between the two sectors involves the subject of the material testing validation and certification. Mayston says there are many stringent test certification requirements that satisfy both rail and aviation regulations.

“For product qualification, the aerospace sector is much more intense than we’ve experienced in the rail industry, even though the design of the panel from the outset is pretty much the same,” he confirms. “BS6853:1999 covers ‘Fire Testing to Railway Components’ and is the UK standard for rail interiors. It’s the testing and qualification requirements our honeycomb structures must comply with. Yet as far as Fire, Smoke and Toxicity (FST) requirements go, one set of industry regulations cannot be transferred to others.

“TRB is working towards to achieving aerospace industry’s AS9100 certification. We already hold International Railway Industry Standard (IRIS) approvals - one of only 20 or so UK companies to achieve this accreditation. There’s clearly lots of crossover, but it still means we need to run both quality standards.”

At the Railway Interiors Expo in Cologne 2011, TRB launched a new, lightweight, modular and contemporary design of PRM-TSI universal access toilet module for rail vehicles.

“By 2020, all rail vehicles in the UK must provide toilet facilities for both able-bodied and person reduced mobility (PRM), which includes a wheelchair accessible toilet module,” concludes Mayston. “The innovative design enables the module to be supplied fully assembled and installed as a single unit for new build trains or as a ‘flat pack’ where trains are being refurbished and the module needs to be transported through the existing door apertures and assembled inside the vehicle. With the unique properties, ease of fabrication together with a high level of recyclability, the honeycomb sandwich panels will continue to play a major part in the rail and other industries for many years to come.”

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