Hemp car moves forward


A BMW door panel made from a hemp mix
A BMW door panel made from a hemp mix

German researchers are using natural fibres in composites to make car bodies and components

German researchers are using natural fibres from hemp, wood, flax and cotton to make car bodies.

Engineers from the Application Centre for Wood Fibre Research at the Fraunhofer Institute for Wood Research have developed processes that combine natural fibres with carbon and plastic and can be shaped to make vehicle body parts and components.

The natural fibres are cheaper than carbon fibres, around the same price as glass fibres and weigh less. They can also be incinerated at the end of their lifecycle to produce additional energy, without leaving residue. In addition they have a “high degree of durability” and possess “excellent acoustic properties”, claim the research team.

Professor Hans-Josef Endres, head of the Application Center for Wood Fiber Research, said: "Depending on the application, we are combining carbon with various bio-based textile fibres. We use carbon fibres in those areas where the part undergoes intense mechanical stress - in other areas, it's natural fibres. This way, we can leverage the strengths of the respective fibres and get rid of the disadvantages to a great extent. "

The fibres are placed in fabric form on each other and are embedded into the plastic matrix. The surface of natural fibres are usually treated so that they can be run easily through textile equipment and processed into fabrics - "sizing the surface of the fibre". While this is important for textile production, it is counterproductive, for processing composite materials. "This is why, from a materials engineering perspective, we optimize the surfaces of the fibres," said Endres.

Instead specially-developed surface treatments or coatings are used to ensure that the fibres can be combined and interact in the best possible way with the matrix or the plastic mass. These surface treatments are used with glass and carbon fibres for reinforcement and it is the first time they have been used with textile fibres. According to Endres the potential is vast: "By ensuring that the fibres bond to the matrix optimally, we can increase the durability of the materials by up to 50%."

The researchers are studying how to scale up production of the hybrid materials and investigating recycling methods, such as how to extract and recover carbon fibres from the matrix. The team are also developing various fibre form-pressed components for the automotive industry. Fibres inside these parts are embedded into a thermoplastic matrix and can be shaped at ultra-high temperatures, or into a duroplastic synthetic matrix that, once it has fully hardened, can no longer be formed.


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