Fraunhofer Institute for Microstructure of Materials and Systems IMWS
Sandwich structural components made from thermoplastic plastics offer enormous potential for lightweight construction and, thanks to their meltability, improved suitability for large-scale production and recyclability compared to thermoset systems. In the current project “rSandwich,” the Fraunhofer Institute for Microstructure of Materials and Systems IMWS in Halle (Saale) is working on manufacturing sandwich components based on recycled materials under industry-relevant conditions. To support this, material-specific analysis methods and material adapted simulation models are being developed, enabling precise predictions of material properties and, in particular, the effects of recycling. This makes it possible to expand the fields of application for recycled plastics and ensure the reliable design of components manufactured from them.
Lightweight construction is a key factor in conserving resources, saving energy, and reducing CO₂ emissions. Sandwich structures offer particularly high potential: a very light core is combined with thin, stiff face sheets, resulting in exceptionally high bending stiffness at very low weight. Compared to conventional monolithic structures, this enables weight savings of up to 80 percent.
Despite these advantages, the use of sandwich structures has so far been largely limited to small production volumes for applications such as rail and aerospace vehicles. The main reasons lie in the widespread use of thermoset technology, which is time- and cost-intensive and therefore poorly suited for large-scale production. In addition, integrating functional elements is complex, and recycling is difficult due to the lack of meltability and solubility. As a result, the use of sandwich structures in cost-sensitive industries with high production volumes, such as the automotive sector, has been restricted, despite the strong demand for sustainable lightweight solutions.
This is where the Fraunhofer IMWS research project “RecyclingSandwich” (“rSandwich”) comes in. The goal of the project is to manufacture thermoplastic sandwich components with recycled content under industry-relevant conditions and to reliably predict their properties for use in structural applications. The basis for this lies in a combination of materials science analysis, adapted process- and structure simulation, as well as process engineering and experimental validation using demonstrators. This allows the specific properties of recycled plastics to be systematically captured, integrated into simulation models, and used for the reliable design of components.
A central focus is the detailed characterization of recycled plastics and their blends with virgin materials. Processing-relevant, mechanical, and thermal properties are analyzed, as well as crystallization behavior and the resulting microstructure, in order to understand how recycling and potential multiple reprocessing affect these key characteristics. “Only if we know the material properties of recyclates as precisely as those of virgin materials can we use their full potential in lightweight construction,” emphasizes Dr. Matthias Zscheyge, project manager at Fraunhofer IMWS. The results achieved are directly incorporated into numerical simulation models that enable precise predictions of both manufacturing processes and structural properties of the components.
In parallel, the project team, together with industrial partners, is developing stable and reproducible processes for the industry-oriented production of sandwich structures with a high recyclate content. By comparing simulation results with practical manufacturing trials, the team ensures that the models are reliable and can also be applied in industrial practice. “In this project, we are bridging the gap between sustainability and structural lightweight construction. It is an important step toward establishing recyclates in demanding industrial applications while simultaneously reducing the ecological footprint,” adds Zscheyge.
With “rSandwich,” a holistic approach is being pursued for the first time to make recycled plastics usable for load-bearing lightweight structures – a field that has so far been insufficiently researched both scientifically and technologically. The project makes an important contribution to closing plastic material cycles, increasing sustainability in mobility, and strengthening the industrial base in Saxony-Anhalt. At the same time, it creates new opportunities for cooperation between research institutions, the plastics industry, and suppliers, opening up new perspectives for a resource-efficient and sustainable future in lightweight construction.
(September 17, 2025)