Plant ramifications inspire branched lightweight composites

Abstract

The junctions between stems and branches in arborescent monocotyledons and columnar cacti are structurally and functionally poorly understood to date. Therefore, the functional anatomy and morphology of these junctions as well as the arrangement and biomechanics of mechanically relevant tissues were investigated. Both plant groups share distinctive anatomical features. Due to restricted secondary growth, newly formed tissues connecting stem and branch clasp around the main shoot, resulting in a “flange-mounted” structure. In addition, an indentation or a distinct necking forming a specific shape characterizes the area of attachment. As a result, the distribution of mechanical stresses is modified by increasing the resistance against high stresses upon static and presumably also upon dynamic loading. The mechanically important fibrous bundles or wood lamellae are collinearly aligned with the occurring stresses leading to a lateral shift of the stress trajectories and a shape adjustment. This particular branching type shows a remarkable potential to improve joints in braided fiber-reinforced composites. In the near future, a fully automated fabrication of biomimetic branched composites will be possible. First promising demonstrators have already been produced on lab scale.