Benny Bar-On - Plant wings as biocomposites
School of Mechanical Engineering Seminar
Monday, March 7, 2021, at 14.00
Wolfson Building of Mechanical Engineering, Room 206
Plant wings as biocomposites
Department of Mechanical Engineering, Ben-Gurion University of the Negev, Israel
Autorotating winged seeds, such as tree samaras, incorporate self-generating aerodynamic lift forces that reduce their falling velocities upon detachment from the tress and enable their passive dispersal into distant places by occasional winds. Understanding the structural–mechanical principles of the samara wings may pave the way to designing high-performance, small-scale wing elements for advanced unmanned aerial vehicles. From a structural–mechanical viewpoint, plant wings are complex hierarchical biocomposite elements that are supposed to resist aerodynamic forces to prevent undesired structural deformations that possibly deter their flying capabilities. In this work, we analyzed the anisotropic structural characteristics and the mechanical properties of the Tipuana tipu (T. tipu) samara wing biocomposite by microscale and nanoscale analysis methods. We quantified the effective elastic properties of wing segment experimentally by micro-tensile testing and its underlying material properties by nanoindentation experiment. Then, we used electron microscopy and computer tomography methods to identify the structural characteristics of the wing material. Finally, we used analytical composite-mechanic models to analyze the structural–mechanical relationship of the T. tipu samara wing. We found that the wing material includes substantial mechanical anisotropy, which its orientation locally varies within the wing; this mechanical “design” plays a significant role in the overall bending and twisting stiffness of the T. tipu samara wing. These insights may lead to new engineering concepts of small-scale wing elements.