This enclosure for a train’s diesel engine is made of a lightweight polyurethane-based material, yet is extremely durable. Image: Fraunhofer ICT
less trains weigh, the more economical they are to run. A new material
capable of withstanding even extreme stresses has now been developed. It
is suitable for a variety of applications, not least diesel engine
housings on trains—and it makes these components over 35% lighter than
their steel and aluminum counterparts.
their efforts to render cars and trains more economical, manufacturers
are trying to find lighter materials to replace those currently used.
But there is a problem: Lighter materials tend not to be as tough as
steel or aluminum, so they cannot simply be used in place of these
metals. Rather, it is a question of manufacturers deciding which
components can really afford to have weight shaved off and how to
integrate them into the overall systems.
together with Bombardier GmbH, KraussMaffei Kunststofftechnik GmbH,
Bayer MaterialScience AG, DECS GmbH, the DLR’s Institute for Vehicle
Concepts, the University of Stuttgart and the Karlsruhe Institute for
Technology, researchers at the Fraunhofer Institute for Chemical
Technology ICT in Pfinztal have now developed a polyurethane-based
sandwich material that is extremely resilient.
demonstrate the material, we manufactured a component that is subject
to significant stresses and which has to fulfill a number of
requirements—the diesel engine housing for a train,” says Jan Kuppinger,
a scientist at the ICT. This housing is located beneath the passenger
compartment, i.e. between the car and the tracks. Not only does it
shield the engine against flying stones and protect the environment from
any oil that might escape, but in the event of a fire, it also stops
the flames from spreading, thus meeting the flame retardant and fire
safety standards for railway vehicles. Kuppinger adds: “By using this
new material, we can reduce the component’s weight by over 35%—and cut
costs by 30%.”
researchers opted for a sandwich construction to ensure component
stability: Glass fiber reinforced polyurethane layers form the outer
facings, while the core is made of paper honeycomb. Polyurethane is a
bulk plastic combining two substances. Since it can be adapted to
fulfill various requirements, it is referred to as a ‘customizable
material’. In foamed form it is soft, and can be used for example as a
material for mattresses; in compact form it is strong and hard. The
researchers began by incorporating various additives into their
polyurethane, altering it in such a way as to ensure it would meet fire
safety standards. Then, the partners optimized the standard
manufacturing process, fiber spraying, by developing a mixing chamber
which allows even more complex structures to be produced in any required
size. The diesel engine housing they made is approximately 4.5-m long
and more than 2-m wide.
is the first time it has proved possible to use this process to
manufacture such a large and complex component that also satisfies the
structural requirements,” states Kuppinger.
one problem encountered with fiber spraying was that it was impossible
to determine the precise thickness of the polyurethane top layers. But
now the researchers have found a way to do this, using computer
tomography to inspect the manufactured layers and then applying a
specially-adapted evaluation routine to establish their exact thickness.
This information helps to simulate the strength of the component, as
well as its ability to withstand stresses.
scientists produced their diesel engine housing demonstrator as part of
the PURtrain project, which is funded by the German Federal Ministry of
Education and Research (BMBF). The demonstrator passed its first
strength test—in which the scientists placed it in a test rig and then
applied forces to it at various locations, measuring the extent to which
it deformed—with flying colors. In the next stage, the researchers want
to trial the component in a proper field test. If that, too, proves
successful, it will then be possible to use the material to make roof
segments, side flaps and wind deflectors for the automobile and
commercial vehicle industry, and to ramp up the manufacturing process to
produce medium volumes of between 250 and 30,000 units.