Fraunhofer Institute for Microstructure of Materials and Systems IMWSElectromobility, dwindling resources, and stricter climate targets are increasing pressure on the automotive industry to design lighter, safer, and more sustainable vehicles. This is where the research project "Circular Bio-Hybrids" comes in: a consortium coordinated by Evonik Operations GmbH is developing metal-reinforced components made from bio-based, natural fiber-reinforced plastics that can be recycled at the end of their life cycle. The Fraunhofer Institute for Microstructure of Materials and Systems IMWS in Halle (Saale) is contributing its comprehensive expertise in natural fiber-reinforced thermoplastics and hybrid injection molding technologies.
The focus is on seat structures for electric vehicles and child seats – components that must meet high requirements for safety, rigidity, and comfort. Until now, glass- or carbon-fiber-reinforced plastics or pure metal solutions have mostly been used for this purpose, but these are energy-intensive to manufacture and difficult to recycle.
"We want to show that components made from domestic natural fibers and bioplastics are not only ecologically sound, but also suitable for high-performance applications," says Dr. Patrick Hirsch, project manager at Fraunhofer IMWS. "If we combine this with a well-thought-out recycling concept, the result is a lightweight construction that is both technically and climatically sustainable."
Hybrid components combine natural fibers, biopolymers, and metal
In the project, hemp and flax fibers are combined with biopolymers such as bio-based polyamide and bonded with metallic inserts – for example, made of steel or aluminum – to form so-called hybrid components. For this purpose, UD tapes made of natural fibers are being developed, i.e., continuous fiber-reinforced tapes of various widths with unidirectionally aligned reinforcing fibers. These provide additional stability exactly where it is needed for crash safety and rigidity. At the same time, processes are being developed that allow the metal and plastic components to be cleanly separated and recycled when no longer in use. To achieve this goal, Evonik Operations GmbH (Essen), Centrotherm Systemtechnik GmbH (Brilon), Sachsen-Leinen e.V. (Markleeberg), ImpulsTec GmbH (Radebeul), HANFFASER Uckermark eG (Prenzlau), the Fraunhofer Institute for Machine Tools and Forming Technology IWU (Chemnitz), and Fraunhofer IMWS cooperate.
Compared to the current state of the art, the new bio-hybrids are expected to combine several advantages: lower weight, a significantly higher proportion of renewable raw materials, a reduced carbon footprint, and a design for recycling approach that has been considered from the outset.
Bio-based UD tapes and suitable processes in injection molding
Fraunhofer IMWS is contributing its expertise in natural fiber-reinforced thermoplastics and hybrid injection molding to the project, which will run until February 2028. The researchers
- develop and manufacture the bio-based UD tapes from hemp and flax fibers,
- characterize the materials down to their microstructure and derive characteristic values for component design,
- are designing the seat demonstrators together with their partners, based in part on an existing child seat shell,
- and are further developing the injection molding process, in which metal parts and natural fiber-reinforced bioplastics are joined in a single step to form a hybrid component.
"Our job is to get the right material to the right place – and to think ahead during the development stage about how it can be separated and recycled as easily as possible later on," explains Hirsch. "To do this, we combine material characterization, simulation, and process development along the entire value chain."
The main challenge is to translate the fluctuating property profile of natural fibers into robust, reliably predictable components while at the same time creating a stable, recyclable bond between metal and plastic. To this end, Fraunhofer IMWS is working with Fraunhofer IWU and industry partners to develop new design methods and joining concepts that can also be transferred to other applications.
The result should be functional demonstrator components – such as seat structures for electric vehicles – that can be used to evaluate the technical, ecological, and economic potential of the technology. In the long term, the materials and processes developed could be used not only in automotive engineering, but also in areas such as rail vehicles, sports equipment, and furniture. For domestic agriculture, the approach opens up additional sales opportunities for hemp and flax fibers, thereby contributing to regional value creation and greater sustainability in the material cycle.
"Circular Bio-Hybrids" is funded by the BMEL's "Renewable Resources" funding program through the Agency for Renewable Resources (FNR).
(March 6, 2026)