Application Center for Wood Fiber Research HOFZET®

Research project

Bioconcept-Car: Sustainable lightweight bodywork as a building block for climate-neutral mobility

Together with Porsche Motorsport and the Four Motors racing team, we develop bio-based lightweight components made from natural fiber-reinforced plastics for the automotive industry and assess their suitability for series production by testing them under extreme conditions on the racetrack. They are a sustainable, cost-neutral alternative to conventional body materials and offer technical advantages. For the future, it is planned for the bio body parts to be used initially in motorsport vehicles and subsequently in large-scale production for everyday vehicles.

Porsche racing car stands at the edge of the Nürburgring racetrack with the passenger door open.
© Fraunhofer WKI | René Schaldach
The “Bioconcept-Car” racing car, equipped with bio body parts, during testing at the Nürburgring.

In the automotive industry in particular, but also in aerospace, rail transport and shipping, efficient lightweight construction solutions are playing an increasingly significant role. These reduce the total weight and therefore contribute towards saving energy and reducing emissions. To date, lightweight construction using fiber-reinforced plastics has primarily utilized carbon fibers. Carbon fibers offer very good stiffness and strength, but their production requires fossil resources and a large amount of energy. Technical challenges exist concerning handling, repair and recycling.

Currently, natural fibers made from flax, hemp, wood or jute are moving into focus as a sustainable alternative. The use of renewable raw materials is also interesting from an economic point of view, as natural fibers are cheaper than carbon fibers. Although, in comparison, natural fibers have lower stiffness and strength values, these values are nevertheless sufficient for many applications. Due to their natural structure, they dampen sound and vibration better. Their lesser tendency to splinter can help reduce the risk of injury in accidents. In addition, they do not cause skin irritation during processing.

In this project, we are developing lightweight body parts made from natural fiber-reinforced plastic for automotive construction. Our aim is to use the biogenic proportion to improve the ecological balance of industrial high-performance composites during the manufacturing, use and disposal phases. We take a holistic view of the supply chain: from the definition of the requirements profile, through the optimization of the individual material constituents and component structures, on to the practical testing and the characterization of possible property changes during the utilization phase. In the final step of the project, we will apply our manufacturing process on a pilot-plant scale in order to demonstrate how industrial large-scale production could look. In addition to upscaling approaches for the components to be produced in higher quantities, we will thereby also consider recovery strategies and recycling concepts.

The test vehicle in the current project phase is a Porsche Cayman GT 4 Clubsport. In cooperation with the project partners Porsche Motorsport and the Four Motors racing team, we are identifying components of the outer skin made from carbon fiber-reinforced plastic (CFRP) and replacing them with natural fiber-reinforced plastic (NFRP). In collaboration with the project partners, these parts are then redesigned, tested in practice on the racetrack as a supplement to standardized test procedures, and subjected to a life-cycle analysis (LCA) and economic evaluation within the framework of a small series. The NFRP components in their new design must not exceed the weight of an equivalent component made from CFRP. Furthermore, they must meet the technical requirements of the component in a cost-neutral manner and, in the best case, exhibit reduced CO2 emissions.

Project results (intermediate status)

Single, white-painted car door stands in front of a wall. The top image shows the outside of the door, the bottom image shows the inside of the door.
© Fraunhofer WKI | Federico Böhm
Door of the “Bioconcept-Car”, made from natural fiber-reinforced plastic (NFRP).
The left image shows a flat test specimen made from carbon fiber-reinforced plastic (approx. 1 mm thick, 6 cm long and wide) with visible fabric structure and a hole in the center; at the edges of the hole, the material stands erect. The right image shows a flat test specimen made from natural fiber-reinforced plastic (approx. 1 mm thick, 6 cm long and wide) with visible tissue structure and a hole in the center; at the edges of the hole, the material stands erect.
© Fraunhofer WKI | Ole Hansen
Ball penetration in test specimen (left: CFRP, right: NFRP).
Die linke Mikroskopsaufnahme zeigt 16 schwarze, längliche, dünne Teile mit speerartiger Form und einer ungefähren Länge von 3 mm bis 12 mm. Die rechte Mikroskopaufnahme zeigt drei hellbraune Teile mit faseriger Struktur und einer ungefähren Länge von 1 mm.
© The left microscope image shows 16 black, elongated, thin pieces with a spear-like shape and an approximate length of 3 mm to 12 mm. The right microscope image shows three light-brown pieces with fibrous structure and an approximate length of 1 mm.
Splinters following ball penetration (left image: CFRP, right image: NFRP).

For the components, the doors and the rear wing as a dynamically loaded component were selected. We then identified the critical or load-bearing points of the components. These are, for example, a certain degree of bending stiffness in the door root, the transition from the door or window frame to the door panel. For a quick and reproducible comparison of different laminate structures, we produced the laminates of the two shells at the critical points as a two-dimensional test panel. By comparing existing laminate structures made from CFRP, we were able to determine benchmark values with regard to relevant properties. Using these values as a basis, the redesign was carried out using various semi-finished products on the basis of renewable raw materials, including natural fibers and bio-based sandwich materials. We thereby considered the differing properties of the laminate structure variants, including mechanical properties, splintering behavior and fire behavior, and supplemented key economic indicators.

From the promising structures, we then produced doors and rear wings using existing tools and vacuum infusion. These parts were tested on the test vehicle in practical use and evaluated for their suitability. This included dimensional and weight changes and an alteration of the gap dimension over up to 24 hours of use on the vehicle. The most successful structures were then transferred to a new tool or component geometry, taking into account economic aspects in small-series production. The door was produced using the resin transfer molding (RTM) process. The rear wing was manufactured using the prepreg autoclave process. Both components were subjected to internal endurance tests at Porsche Motorsport and ultimately rated positively.

At the beginning of 2019, the Porsche 718 Cayman GT 4 Clubsport was presented to the public as the world's first series-produced racing car with natural-fiber body components. We are currently developing recycling concepts as a further basis for the still-pending life-cycle analysis of the components.

With our project, we are helping to ensure that bio body parts can be used in the industrial large-scale production of everyday vehicles in the future.

Project partners

  • Porsche Motorsport
  • Four Motors

Funding

Funding body: German Federal Ministry of Food and Agriculture (BMEL)

Project management: Fachagentur Nachwachsende Rohstoffe e. V. (Agency for Renewable Resources, FNR)

FNR funding reference: 22007717

Duration: 15.6.2017 to 14.6.2020