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11-01-2017

PU Spraying plus RIM for Series Application

High-Performance Sandwich Composites Made in a Single Step

Leichtform GmbH in Bernsdorf, Saxony, Germany, is developing a process to produce high-performance sandwich structures for hybrid lightweight construction. They work together with scientists from the ILK Institute of Lightweight Engineering and Polymer Technology, University of Applied Sciences Dresden, Germany, while the project is managed by Professor Maik Gude from the same institute. The Shape research project is funded by the Federal Ministry for Economic Affairs and Energy, and is concerned with the production of sandwich structures with complex geometries, which has been very demanding until today. The project is due to facilitate the manufacturing process and make it ready for series production.

Easy Process Control Yields Increase in Productivity

The new type of process benefits from the expansion reaction of foamable polyurethane (PU) in a closed mold, while the reactive PU mixture penetrates the semi-finished textile products. This way, the mold is filled close to the contour. Production of the foam core and impregnation of the final covering layer of the sandwich take place in a single stage. In addition to pure foam cores, the process will allow to integrate unlaminated honeycomb paper structures, too.

High-performance sandwich composites with polymer core and covering layers of semi-finished textiles (left, center), plus integrated unlaminated paper honeycomb (center), compared to structures with covering layers made of cut-to-size long fibers (right), produced in a polyurethane spraying process (© TUD/ILK)

High-performance sandwich composites with polymer core and covering layers of semi-finished textiles (left, center), plus integrated unlaminated paper honeycomb (center), compared to structures with covering layers made of cut-to-size long fibers (right), produced in a polyurethane spraying process (© TUD/ILK)

Process Takes only Few Minutes

The process is superior because it manufactures the fiber-reinforced covering layers and the foam core of the sandwich in one and the same mold. Until today, especially structures with a complex shape could be obtained only by producing the core in a separate step, followed by subsequently adding the laminar layer by adhesion bonding.

Subject to the respective foam system, the new process requires production times of only few minutes. If thermoplastic films are integrated right during the process, a component is obtained with excellent surface quality, which is why there is no need to varnish the part in a subsequent step. Inserts can also be included by insert molding with foam, which makes it possible to integrate subcomponents directly, without any complex processing steps.

Integrating Textile Reinforcing Structures and Thermoplastic Films

The scientific work conducted in the framework of the Shape project is aimed to establish a process that is ready for serial production, on the basis of the polyurethane spraying and the RIM reaction injection molding process. Headed by engineer Oliver Weißenborn, the team of scientists is developing concepts to integrate textile reinforcing structures and thermoplastic films, as well as load introduction elements that fit the respective material.

The scientists plan to investigate the sandwich composites for their range of properties in comprehensive mechanical tests. By defining the number of covering layers, density of foam and thickness of layers according to the respective load, the customized structures are obtained that are necessary for the complex geometries.

Company profile

TU Dresden - Institut für Leichtbau u. Kunststofftechnik

Holbeinstr. 3
DE 01307 Dresden
Tel.: 0351 463-38142
Fax: 0351 463-38143

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