Lightweight Passenger Busses
Collaboration between Aliancys, Büfa and VDL Bus & Coach
Passenger bus manufacturer, VDL Bus & Coach, Valkenswaard, The Netherlands, has introduced its new Citea series of busses to the market, incorporating multiple light-weight composite components. These components are made by applying a foaming resin formulation supplied by Büfa Composite Systems, Rastede, Germany, on the basis of resin from Aliancys AG, Schaffhausen, Switzerland. Besides bringing unique shapes and great aerodynamics, the use of low density composite parts results in major weight savings for the bus, translating into lower fuel cost and emissions.
VDL already has a good experience using composites in its busses. Yet for its new Citea busses it wanted to step up its efforts in reducing weight and manufacturing efficiency for the medium-sized production series. The company has been actively looking for composite material technologies that better combine design flexibility, mechanical strength and light weight. Molding company OMB Composites, Psáry, Czech Republic, made for VDL multiple composite components in a vacuum expansion process (VEX-technology), working with specially formulated resin compounds supplied by Büfa Composite Systems. After opening the mold, the mold surface is covered with a gelcoat, then reinforcement and resin is applied. After closing the mold the resin starts to foam and fill the mold.
Depending on part design and end-use performance requirements, the vacuum expansion process (VEX-technology) with foaming resin allows to make large components up to 2 x 6 m. With weight savings up to 45 % compared to parts made from conventional resin technologies, the technology enables to have a cycle time of only 3 hours per part. Using Hand lay-up production techniques results in a much longer production time. With this new technology, part surface can be very smooth, enabling the application of surface coatings for a perfect Class A finish.
Finding the Right Resin
When developing the special foaming resin compounds, Büfa worked closely together with Aliancys to fine-tune resin composition and cure. The special Orthophthalic base resin used for making the foaming resin compound was tailored by Aliancys to the specific needs of the application. “We like very much working together with our customers in the development of new process technologies”, comments Paul Vercoulen, CTO of Aliancys. “With this close collaboration, BÜFA and Aliancys have been able push the limits of composites part performance and processing, delivering light weight, sustainability and great system cost.”
The technology of vacuum expansion with a foaming resin is explained in a short video on YouTube .
BÜFA GmbH & Co. KG
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