Arundo and fiber composites

From nature ...

Stability and at the same time high flexibility characterize the culms of arundo, a grass up to 8 meters high. They are hollow between the nodes. How does the two to eight millimeter thick culm wall achieve such strength and elasticity? A look through the microscope reveals a matrix of storage tissue with elastic vascular bundle strands lying parallel to each other. Instrument makers have been using this material for centuries for the reed in the mouthpiece of clarinets and oboes.

... to technology

Technical fiber composites, e.g. made of thin glass fibers in epoxy resin, can also produce lightweight, stable components. Studies on plant stalks provided valuable approaches for improvement.

One important aspect is the arrangement of the fibers. Their course can be optimized on the basis of natural models. In less heavily loaded areas, a foam-like matrix with a selectively adjustable pore size can reduce the fiber density to save material. The bond at the transition between fiber and matrix also plays an important role: A gradual transition of the elasticities of fibers and matrix is better than a hard contrast between the two.

Image captions

Arundo (Arundo donax L.) - how does an 8 m tall grass stalk with a wall no more than 8 mm thick "work"?

Cross-section through the stalk wall: the fiber bundles, colored red, are embedded in spongy storage tissue.

Bending test with a biomimetically optimized fiber composite (top) and a conventional specimen.

Text of the information board in the Botanical Garden