Composites track down rail opportunities As composite industry,
s rail operators
strive to reduce
an attractive mass transport
alternative to steel for applications. While con-
ventional metal body shells provide high static and dynamic strength, they offer little scope for weight reduction or design flexibility, and manufacture and repair can prove costly. Using composite constructions not only reduces weight, thereby improving fuel economy and increasing payload capacity, but also enables the design of aerodynamic, stable vehicles with low centres of gravity.
more accessible increasingly
to the transport
used in both reports.
walls can be made
fibre reinforcements with polyester or phenolic resin with a wet lay-up process. This method can result in parts with poor mechanical properties, which limits their use to non-structural applications. However, as composite manufacturers
rial than those made using wet-lay up because of a more precise resin content and optimum fibre volume. According to prepreg manufacturer Hexcel Composites, to obtain the equivalent mechanical performance using wet lay-up, components can weigh up to 50% more than those made using prepregs. Inter-laminar shear resistance with epoxy prepreg is also three times higher than with phenolic or polyester resins in a wet lay-up operation.
Ju n e 2 0 0 I
insulation, saving yet more weight. Prepreg components require less mate-
develop core materials and prepregs designed specifically for mass transit applications, composite primary structures are being increasingly used. Compared with parts made using wet lay-up processes, sandwich structures offer improved flexural rigidity and flexural strength, which means that
is CIcomposite sandwich construction of GRP skins with a Klegecell
lation and structural dampening properties eliminate the need for additional
The ET 423’s
space. High thermal
Swedish core material manufacturer DIAB is currently working with several European train component builders to provide both core materials and processing technology for high speed express and commuter trains. Projects include the ET 423 built by Alstom/LHB and Adtranz Niirnberg, Germany. The front of the ET 423 consists of a sandwich structure of glass fibre reinforced plastic (GRP) skins over a [email protected]
R 65 GS foam core attached to a metal chassis. In this case, DIAB estimates that composites have provided weight savings of approximately 4 kg/m2. The Adtranz Regio-Shuttle train takes the composite sandwich concept even further by using sandwich constructions based on various grades of DIAB’s Divinycell and Klegecell core materials for the front, sides and roof.
Elsevier Science Ltd. A// rights reserved.
kg of the bogies
The use of composites in train interiors, side panels and driver cabs is well
are used for both primary
known, but European Transport is moving
company Alstom into other areas
with the development
of an innovative
bogie. Rail carriages
by two bogies weighing
around 7 tonnes each, so they account for a great deal of the structure and weight on a train. Using composites tried
suspension. The dampening properties of the composite will also contribute to a smoother
and quieter ride for passengers
says Hexcel. One part of the bogie that has undergone intensive research is the all composite leafspring. Manufactured by French
Hexcel’s HexPly Ml0 glass unidirectionin bogies has been
shown that the leafspring
can carry three
DaimlerChrysler) produced a prototype bogie based on an existing metal design
times more payload that the existing version, withstand more than 10 million
in the 1980s
nents were replaced with composites. Alstom’s bogie, however, is specially designed to take full advantage of composite properties. Designed to support a main line train travelling at 200 km/h, Alstom’s bogie weighs 22% less than the model currently used on Intercity 200 km/h trains. Composites account for
track down rail opportunities
and meet French
fire safety standards. The next step for the leafspring
be more rigorous testing in a test bed and in a working rail carriage. The bogie is expected to enter full production within the next two-three years and one major European rail operator is said to have already shown an interest.
and processing developments
Hexcel Composites developed HexPly M34 epoxy prepreg specifically for the manufacture of large structural components in ground-based mass transport applications. M34 cures at 75°C and is processed using vacuum bag moulding. According to Hexcel, its adhesion to polyvinyl chloride (PVC) foam and aluminium and nonmetallic honeycomb makes it particularly suitable for use in sandwich structures. It also meets German and French specifications for fire retardancy in rail applications. Recent developments from DIAB include a core material (DivinycellB HPS) that is designed for use with low epoxy prepreg. The temperature, material is said to offer excellent dimensional stability up to 12O”C, and is designed to provide a costeffective alternative to honeycomb and to allow current users of foam sandwich technology to produce
higher quality laminates. The company has also developed a infusion process based around its [email protected]
, [email protected]
and [email protected]
core materiis designed to reduce als, which process cycle times. The infusion system, which is already being used to manufacture train roofs, sides, fronts and internal components, is a closed production method for sandwich panels with FRP skins. Compared with other resin infusion methods, DIAB says that its system has a number of advantages that make it particularly suitable for train components. A pattern of small grooves in the core material transports the resin to wet out the fibres quickly to enable the production of large panels. No addimaterial is tional distribution required, which also reduces production costs. A flexible second mould can be used to give an excellent finish on both sides of the component.
Composites reduce the weight of the bogie by 22%. (Image courtesy of Alstom Transport.)
Crash safety Composites still face problems associated with use in safety-critical areas as they tend to fail in an unpredictable and often catastrophic manner. At the end of the 1990s the HYCOTRANS project, coordinated by the Advanced Railway Research Centre at Sheffield University, UK, was launched in order to produce a crashworthy composite sandwich structures that fails predictably. The 36 month project resulted in the development of a hybrid composite sandwich structure consisting of two fibre reinforced plastic (FRP) skins and a relatively weak foam or honeycomb core containing corrugated FRP. The corrugated FRP forms a continuous channel that is designed to fail at a predetermined stress level. In order to exploit this technology in the future the HYCOPROD project was launched. Over 48 months, Hycoprod is working to develop a production process that will enable the systematic coque
manufacture of very large monohybrid composite sandwich W structures.
Thomas Skoglund, DIAB AB; tel: +46-430+46-320-l 6395; e-mail: 16300; fax: [email protected]
www.diabgroup.com. Bruno Bolzinger, Hexcel Composites; +33472-252663; fax: +33-472-252728; e-mail: website: [email protected]
; ww w.hexcelcomposites.com.