Fraunhofer Institute Develops GFRP Sandwich Material

This diesel engine housing for trains, manufactured by The Fraunhofer Institute for Chemical Technology, incorporates an extremely resilient GFRP-based sandwich material

This diesel engine housing for trains, manufactured by The
Fraunhofer Institute for Chemical Technology, incorporates an
extremely resilient GFRP-based sandwich material.

The Fraunhofer Institute for Chemical Technology (ICT) in Pfinztal, Germany, has developed a glass fiber reinforced polyurethane (GFRP) sandwich material that can reduce the weight of train and automobile components. The resilient material can withstand extreme stresses and makes components 35 percent lighter than their steel and aluminum counterparts, according to the research organization.

In order to test the material strengths of GFRP, Fraunhofer ICT worked with Bombardier Transportation 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 to manufacture a diesel engine housing for passenger trains. The composite diesel engine housing demonstrator is located beneath the passenger compartment, between the car and the tracks. It shields the engine from flying stones and prevents oil from escaping. 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.

The diesel engine housing developed by the Fraunhofer Institute and it partners’ features a sandwich structure with GFRP in the outer layer and honeycombs as a core structure. It was manufactured using an automated polyurethane fiber spraying process. Before the involved researchers started manufacturing the engine housing, they first altered the composite material properties to ensure the engine house would meet safety standards to the same capacity or better than the current metal counterparts. They started incorporating various additives to the polyurethane resin to maximize strength and fire retardant properties.

Next, the team optimized the standard manufacturing process — fiber spraying — by developing a new mixing head that allows manufacturing more complex structures. Additionally, they determined the precise thickness of the face sheets of polyurethane based sandwich structures. Therefore, the researchers opted to use computer topography to inspect manufactured layers, then applied a specially-adapted evaluation routine to establish their exact thickness. This allowed the team to gain information on the strength of the component and its ability to withstand stresses.

Finally, the team was ready to manufacture a strong composite diesel housing. After nearly four years the team produced the first diesel engine housing demonstrator as part of the PURtrain project, which is funded by the German Federal Ministry of Education and Research. The diesel engine housing they produced is approximately 15 x 6.5 feet and passed its first strength test of the components in late 2011. “The project was a success,” says Professor Frank Henning, Head of the Fraunhofer Project Centre for Composite Research (FPC) at Western University in London, Ontario, “quite a transfer of lab know-how into industrial application.”

The demonstrator needs to pass a field test, which is currently on hold awaiting for a response from the Railway Supervisory Authority, says Tobias Potyra, researcher at the FPC. If that’s successful, the GFRP sandwich material could be used to make roof segments, side flaps and wind deflectors for the car and commercial vehicle industry.