Venation Pattern of Butterbur Leaf and Its Mechanical Contribution
Hidetoshi KOBAYASHI, Masashi DAIMARUYA and Kaori KURIBAYASHI
Abstract:One of the typical leaves with wide leaf shape is a leaf of butterbur (Petasites japonicus). To investigate the mechanical contribution of veins in wide leaves, the length and diameter of veins, the angle between veins and the thickness of lamina were measured by using optical devices. It was found that butterbur leaves have veins with an ellipse cross-section instead of a circle cross-section and analogous geometry irrespective of their size. To obtain the mechanical properties of veins and lamina, static tensile tests were carried out. Young's modulus of veins was about 60 Mpa, which was about eleven times greater than that of lamina. By using the geometrical data and mechanical properties of veins and a lamina, a number of leaf models were made for FEM analysis. It was found that the capability for supporting load of the leaf model with the most similar venation pattern to a real butterbur leaf was greater than that of other models with simplified patterns, even the total mass of a leaf was maintained to be constant. Key Words:Biomimetics, Butterbar leaf, Vein, Tension test, FEM analysis, Supporting structure