Using a Biocomposite for a Rail Carriage Door Leaf

Huntington-based TRB Lightweight Structures Ltd. presents an all-new biocomposite resin-based Carbon Fibre Reinforced (CFRP) sandwich panel door leaf with a 100% recycled foam core. Specifically designed and fire rated for both overground as well as underground rail use, TRB’s all-new composite structural system is BS 6853, BS 476, and EN 45545 HL3 compliant

Innovative Biocomposite Door Leaf

The biocomposite door leaf product offers a sustainable, ‘green’ alternative to the rail industry, with carriage door leaves that are competitively priced compared to aluminum bonded door leaves, with a 35% weight saving. TRB achieves this by applying its proprietary knowledge of composite materials technology and expertise in railway applications, thus broadening its product portfolio to an established rail industry customer base. This product therefore meets the growing global market need for greener, more energy efficient products.

In close partnership with a renowned resin manufacturer, TRB’s design and engineering team have developed a unique, proprietary carbon fiber compatible bio prepreg resin. TRB’s key criteria was that the new system needed to be extremely sustainable and enable the cost-effective manufacture of lightweight composite parts that would meet the most rigorous fire, smoke and toxic fumes (FST) criteria in subterranean rail applications.

As a result, the new ‘bio’ prepreg is non-toxic and does not use volatile organic solvents. Moreover, the solution is based on a Polyfurfuryl Alcohol (PFA) resin, which is derived from renewable alcohol produced as a natural waste bi-product during the production of refined sugar.

Sustainable Fire-Rated Biocomposite Prepreg System

This unique biocomposite prepreg system is the first sustainable fire rated material of its kind. TRB developed the bio prepreg based system exclusively for FST rail applications, as well as carriage door leaves. Moreover, the flagship product can be applied to other rolling stock parts as well. The foam core used in the production of rail door leaf composite structure comes from 100% recycled consumer plastic.

TRB chose this particular recycled foam core as it meets the company’s key ‘high sustainability’ specification objective. Moreover, the core delivers the desired overall material properties performance of the sandwich panel construction when used in conjunction with the woven carbon fiber fabric on both sides and the bio-resin prepreg.

TRB can also tailor-make matrix design options for a variety of applications using glass fibers, natural fibers, or aramid fibers. Door leaves are then supplied with a gelcoat, finish painted or primed ready to paint, as per the individual requirements of each rail customer.

Functionalities of the Biocomposite-Based System

TRB’s unique biocomposite based system provides unmatched fire performance specified for a rail carriage door. Moreover, as per independent research, the sandwich panel system, upon being tested to BS 476 Part 7: 1977 for ‘Spread of Flame’, achieved a Class 1 Category 1a rating with ease, with a 30% less recorded flame spread of only 50 mm in the 1.5 minute test time; the maximum allowable being 165 mm for the Class 1a rating.     

We are extremely pleased with the overall performance data for the new biocomposite carbon fibre prepreg sandwich panel system, in particular the FST specifications achieved. In the 30 years I have been in the industry, I have never seen such impressive fire performance test results for a non-phenolic based thermoset system, achieving the BS standard so comfortably. Our PFA bio resin prepreg has fire retardant properties greater than phenolics, plus excellent temperature and chemical resistance. We initially developed this biocomposite product for rail door leaves, but it could be used for other mass transport interior applications. We have brought aerospace prepreg technology to our rail customers and can now offer them a truly ‘green’ material design option that is 35% lighter than a bonded Aluminium door at a comparable cost.

Lyndon Newman, Chief Engineer, TRB

TRB provided data to compare a ‘like for like’ aluminum door leaf, which weighed 40 kg excluding any fittings or door furniture. In comparison, the same sized door produced by TRB uses a new biocomposite CFRP prepreg sandwich panel system, and weighs just 26 kg.

TRB’s biocomposite CFRP door leaf, which has an expected 40 year life cycle, is more robust than its aluminum counterpart. Moreover, the product has superior fatigue resistance and incurs lower maintenance costs. Due to the significant reduction in weight, the composite door leaf requires a lighter door operating system and provides a host of cost saving benefits to rail operators, including: reduced energy consumption per journey as well as less track wear and tear.

In addition, benefits include shorter station dwell times as the lighter door leaves open and close several seconds faster. Transport for London has calculated this as a way of improving its daily underground service, and when installed, will enable an additional tube train to be run per day on a line where needed, thereby easing peak time congestion.


TRB has been approved by the International Railway Industry Standard (IRIS), seeing as the company has been manufacturing high quality rail doors and rail interior products ­– used in trains and transportation systems worldwide – for over 60 years. Not just that, the company also has extensive experience in both building new trains as well as refurbishing existing ones.

A leading international manufacturing and engineering company, TRB specializes in the design, testing, validation, and production of lightweight composite products. Today, TRB supplies to rail, aerospace, defense and several other sectors, including electric vehicles, thus providing customers with a complete concept-to-delivery service.

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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