Generally, composites such as sandwich elements can be used for structural and for non-structural applications (e.g. interior coach panels). According to TIFAC, weight savings of up to 75 % can be reached in non-structural and up to 50 % in structural components. These are very optimistic estimates. The following examples describes two applications already realised:

Application of sandwich composites for structural elements

Hexcel claims that the separating floor structural panels produced for Schindler Waggon AG (to be used in IC2000 double-deck train carriage) are 20% lighter than the conventional welded aluminum extrusion profile system.

Application of sandwich composites for non-structural elements

For non-structural elements (such as interior panels) the weight savings achievable are even higher. According to Schuon 1998, Interior panels for passenger coaches are approx. 35% lighter than conventional panels, which reduces the total coach weight by some 350 kg. Given typical coach weights of 40 tons this is a weight reduction of ~ 1 %.

Overall effect

An overall effect on energy consumption strongly depends on the specific application and cannot be assessed in a general manner.

The following rough estimate may give a general idea of the potential:

Currently, applications of sandwich materials are mainly limited to interior equipment (floor panels, interior wall and roof panels etc).

• Interior equipment usually accounts for 10 - 20 % of the total coach weight
• It is assumed that about one half of the corresponding components may be substituted by sandwich components (panels, floor etc)
• The relevant components may be reduced by up to 50 %.

This yields the maximum weight reduction through sandwich materials will be around 5 %.

The following elasticity table gives estimates for the overall effect on energy consumption.

	Traction	Brake energy recovery	Effect on train mass	Elasticity with regard to train mass	Effect on total energy consumption for traction
High speed train	electric	no	5 %	0,17	1 %
		yes		0,12	1 %
Intercity train	electric	no		0,19	1 %
		yes		0,14	1 %
	diesel	-		0,19	1 %
Regional train	electric	no		0,52	3 %
		yes		0,44	2 %
	diesel	-		0,52	3 %
Suburban train	electric	no		0,64	3 %
		yes		0,57	3 %
	diesel	-		0,64	3 %
Range:					1 – 3 %

The environmental impact of composite materials cannot be assess in a general fashion but rather depends on the concrete materials used. The following aspects play a role:

• Composite materials always pose recycling problems.
• Possible environmental impacts of the substances used for honeycomb structures have to be carefully assessed, e.g. foam cores (such as CFCs) that contribute to atmospheric ozone depletion.

A target conflict can therefore arise between energy efficiency gains through sandwich materials and newly induced recycling problems. However, given the long life-time of rail vehicles, the environmental benefit of mass reduction will presumably compensate slight drawbacks in other fields.