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22.04.2025

High-volume lightweight construction with thermoplastic sandwich structures

Thermoplastic sandwich moulding technology enables the fully automated production of 3D moulded components in material-efficient lightweight sandwich construction, which are additionally functionalised by injection moulding. The potential of this innovative hybrid technology was demonstrated on a storage compartment flap of a truck driver’s cab.

The fiber composite sandwich construction method enables enormous weight savings in the implementation of structural components. However, component manufacture is still associated with labour-intensive, manual processes and long cycle times.

The use of thermoplastic fibre composite sandwich semi-finished products represents an innovative development approach for use in large-scale production. In contrast to thermoset fibre composite systems, these can be produced particularly efficiently in ThermHex’s continuous processes and processed into components in fast, automated manufacturing processes.

With thermoplastic sandwich moulding technology (TS moulding), the Fraunhofer Institute for Microstructure of Materials and Systems IMWS has developed a process that enables the further processing of pre-consolidated, thermoplastic sandwich semi-finished products. The shaping step takes place by thermoforming in a closed mould, which also enables additional functionalisation by injection moulding.

Mould for thermoplastic sandwich storage compartment flap in ENGEL v duo700 injection moulding machine at the Fraunhofer IMWS

Successful demonstration of feasability

A research and development project now examined the thermoplastic sandwich moulding technology’s applicability for efficiently and reliably producing vehicle interior components. To this end, a storage compartment flap from a truck driver’s cab was selected as a demonstrator structure and prototypically implemented in thermoplastic sandwich construction – for the first time on a real component structure.

Storage compartment flap in a truck driver’s cab / © Daimler Truck

This required a process-appropriate mould design using numerical process simulation tools and experimental research of the feasibility of component-relevant design features. Geometric features such as a visible edge running across the entire width of the component, a circumferentially closed edge and the injection moulding of a recessed grip were demonstrated. Furthermore, the injection moulding functionalisation was successfully implemented on the component. Hinge and fastening elements as well as a holder for the handle mechanism were injection moulded onto the thermoformed sandwich component.

This successfully demonstrated the largescale production of functionalised, 3D-moulded lightweight sandwich components.

Process diagram of thermoplastic sandwich moulding technology

Honored with the JEC Innovation Award

Compared to the reference component (paper honeycomb, PU-GF, SRIM process), a weight saving of approx. 15 % (without decor and functional elements) was achieved with the thermoplastic-based material structure. Its use also has a positive effect on the recyclability of the component. This also convinced the jury of the JEC Innovation Award 2025, which declared the thermoplastic sandwich moulding technology winner in the “Automotive and Road Transportation – Process” category.

Project partner: Fraunhofer IMWS, Daimler Truck AG, ElringKlinger AG, ThermHex Waben GmbH, ENGEL Austria GmbH, Edevis GmbH

Contact:

Fraunhofer Institute for Microstructure of Materials and Systems, Halle (Saale)
Dr.-Ing. Ralf Schlimper
Group leader Evaluation and Design of Fiber Composite Systems
+49 345 55 89-263 | +49 173 529 37 57
ralf.schlimper@imws.fraunhofer.de
www.imws.fraunhofer.de