PU Sandwich Elements for Commercial Vehicles
High-strength PU-based sandwich components can now be produced by means of a new process that was developed jointly by a group of researchers and industrial companies. A diesel engine enclosure has been manufactured as a demonstrator. This enclosure is located under the passenger compartment, i.e. between the compartment and the rails. It is claimed that, by using the new material, the weight of this component is reduced by more than 35 percent, while manufacturing costs are lowered by 30 percent.
The component achieves its stability from its sandwich construction. The exterior surfaces are formed by a glass fiber-reinforced layer of polyurethane (PU), the interior is formed by a cardboard honeycomb. The PU was modified in order to achieve compliance with the flame and fire retardance standards for rail vehicles. In a second step, the researchers optimized the fiber spraying process. This involved developing a special mixing head that permitted production of large, complex parts. The diesel engine enclosure is about 4.5 meters long and over two meters wide. According to the developers, this is the first time that fiber spraying has been used successfully to manufacture a complex part of this size that satisfies the structural requirements.
The thickness of the resulting PU sandwich layers can be determined precisely via computer tomography. This information helped to predict the strength of the component. The next step calls for testing the enclosure in field trials. If the tests are successful, it may also be possible to manufacture roof segments, side panels and wind deflectors from this material for the automobile and commercial vehicle sectors in the future.