Fraunhofer Institute, German battery manufacturer Ansmann develop theromplastic PP sheets reinforced with flax fibers for battery housing; organic sheets have same strength as metal sheets, but are lightweight, suitable for construction applications

Sample article from our Bioeconomy

Germany , July 20, 2022 (press release) –

Better mechanical properties, lower weight

The Fraunhofer Institute for Structural Durability and System Reliability (Fraunhofer LBF) and Ansmann AG, a leading German manufacturer of lithium-ion batteries, have developed organic sheets with flax fibers in the Biobattery project. The metal sheets were built into a battery housing for e-bikes for reinforcement.

Organo sheets are fiber-reinforced thermoplastics that can be processed in a similar way to sheet metal. Their strength is in no way inferior to that of classic sheet metal components, while at the same time they are lighter.

The continuous manufacturing process for the natural fiber organic sheets adapted by the Fraunhofer LBF opens the door to serial, industrial production. Due to its mechanical properties and low weight, the new material is particularly suitable for lightweight construction applications with high requirements.

Organo sheets with natural fibers have so far hardly been commercially available on the market. The reason for this is the sensitivity of natural fibers to high temperatures, which makes impregnation with the thermoplastic matrix more difficult. On the other hand, fibers made from hemp and the like are characterized by a low tendency to splinter and high elasticity, which promises materials with hitherto unrivaled impact strength. They could improve crash behavior and reduce the risk of the battery housing breaking in e-vehicles.

In the BioBattery project, the Fraunhofer LBF has adapted a self-developed melt impregnation process so that it is suitable for the continuous production of organic sheets from natural fibers. The materials used by the Fraunhofer team were flax fibers, which have higher thermal stability than other natural fibers, and polypropylene (PP) as the matrix. The researchers also performed tests using bio-based PA11 [1]  as a matrix. In the long term, this could be the more interesting raw material, since its mechanical properties even surpass those of PP.

An e-bike battery housing from Ansmann, which was reinforced with flax PP organic sheets, served as a demonstrator. In tests, samples of these housings exhibited better mechanical characteristics than comparable materials while at the same time being lighter.

The organic sheets were connected to the battery housing using the injection molding process. After cooling, the manufactured components showed a slight, undesired curvature, which the researchers attribute to a different expansion of the matrix and organo sheets. You now want to examine possible solutions. If the optimization of the process succeeds, the industrial use of the natural fiber-based organo sheets will be within reach.

The project "Large-scale lightweight construction with natural fiber-reinforced bio-based plastics using the example of lithium-ion battery housing" was funded by the Federal Ministry of Food and Agriculture (BMEL) via the project sponsor Fachagentur Nachwachsende Rohstoffe e. V. (FNR). Information and the final report are available at under the funding reference 22010018 - and 2219NR064 - available.

Agency for Renewable Resources eV
Robert Hardt
Tel.: +49 3843 6930-204
Email:   r.hardt(bei)

Press contact:
Agency for Renewable Resources
Nicole Paul
Tel.: +49 3843 6930-142
Mail:       n.paul(bei)

PM 2022-42

[1] bio-based polyamide from castor oil

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