From natural branchings to technical joints: branched plant stems as inspiration for biomimetic fibre-reinforced composites

Abstract

The manufacturing of nodal elements and/or ramifi cations with an optimised force fl ow is one of the major challenges in many areas of ficomposite technology. The examples include hubs of wind-power plants, branching points of framework constructions in building industry, aerospace, ramifi ed vein prostheses in medical technology or the connecting nodes of axel carriers. Addressing this problem requires the adaptation of innovative manufacturing techniques and the implementation of novel mechanically optimised fi bre-reinforced structures. Consequently, the potential of hierarchically structured plant ramifi cations as concept generators for innovative, biomimetic branched fi bre-reinforced composites was assessed by morphological and biomechanical analyses. Promising biological models were found in monocotyledons with anomalous secondary growth, i.e. Dracaena and Freycinetia, as well as in columnar cacti such as Oreocereus and Corryocactus. These plants possess ramifi cations with a pronounced fi bre matrix structure and a special hierarchical stem organization, which markedly differs from those of other woody plants by consisting of isolated fi bres and/or wood strands running in a partially lignifi ed parenchymatous matrix. The angles of the Y- and T-shaped ramifi cations in plants resemble those of the branched technical structures. Our investigations confi rm that the ramifi cations possess mechanical properties promising for technical applications, such as a benign fracture behaviour, a good oscillation damping caused by high energy dissipation and a high potential for lightweight construction. The results demonstrate the high potential for a successful technical tran sfer and led to the development of concepts for producing demonstrators in lab-bench and pilot plant scale that already incorporate ‘solutions inspired by nature’.