BionicResearch On The Relation Between The Multi-scaled Structure And Mechanical Behavior Of Dragonfly Wing

The extraordinary mechanical performances of biological materials have fascinatedmany scholars and scientists. The dragonfly wing, as the dragonfly’s flying organ, is ofthis kind. The wing is quite thin and light. Its specific strength and stiffness, however,are far beyond various kinds of aluminums alloy.Empirically, the outstandingmechanical properties should be connected with the structure of the material. In thiswork, the dragonfly wing is investigated by observation experiments to describing itssophisticated microstructures. Based on this, pertaining models are constructed tocharacterize the mechanical behavior of the structured wing. Furthermore, theory andnumerical approaches are employed for identifying the relationship between thestructure and mechanical behavior of the wing.To begin with, the morphologicaland wing mass parameters of the wing aremeasured. Underlying the obtained data, the Beta distribution function is chosen for theanalytical representation of the wing shape by the chord c and the distance from wingbase r. The wing mass parameter could provide an understanding of the wing massdistribution along the wing span direction. Moreover, the moment of inertia of the wingcan be calculated, as well as the center of gravity of the wing.Furthermore, the ESEM images reveal that the wing could be describedin terms ofa three hierarchical levels of composite biomaterial from macro-, micro-to nano-scale.The first level is the3D arrangement of main longitudinal formed the “W”corrugationof the leading edge at the macro level; the sandwiched wing including the chitinousshells and protein layer and the upper and lower epidermis of the membrane at themicro level are the second level; cluster of nano-fibrils embedded protein layer, theparalleled multilayered chitinous shells and membrane are considered as the third levelat nano scale. Arising from the structure, theory models are introduced to evaluatemechanical properties of individual hierarchical component and relations.It reveals thatthe “W” corrugated configuration is induced by the microstructure and nanostructure ofthe wing. The corrugation of the leading edge also connectto the dragonfly body as thewing hinge, is similar to a damped torsional spring model.Besides, the relation between the structure and mechanical performance of the wing is twofold: Firstly, the dragonfly wing adopting the hierarchical compositematerial optimizes the specific structure’s distinguished biomechanical characteristicswhen exerted by a variety of loadings. The introduction of the fibril strengthenedprotein and lamella of the chitinous layers bring a more flexible wing, besides, theinterface between the chitinous layer and soft layer and the circumferentially growth ofnano-fibrils help to absorb larger torsional deformation. Even the torsional spring hingecan serve as an active control mechanism to fulfill specific aerodynamic requirements.Secondly, the three level hierarchy of thedragonfly wing are selected by insect wing’smechanicalprerequisites taking the bending and torsionloadings into account duringservice.The natural frequency and mode analysis indicates thatthe structure inducedwing corrugation increases its resistance to bending, but is compliant to torsion.