Concepts for Morphing Airfoil Using Novel Auxetic Lattices
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In nature, the wings shape of a bird can be adjusted to be suitable for all flight situations providing optimal aerodynamic performance. Unfortunately, wings of traditional aircraft are optimized for only a few conditions, not for the entire flight envelope. Therefore, it is necessary to develop the morphing airfoil with smart structures for the next-generation excellent aircraft. Combined with the actuators, sensors and controller techniques, the smart airfoil will bring a revolution for aircraft. Hence, the design of smart structure which is applicable for the morphing airfoil is the first step, especially the flexible airfoil which exhibits many more changeable degrees than rigid structures. In this paper, the composite structure based on re-entrant quadrangular is designed to be applied in the deformable aircraft. The re-entrance structure can show negative Poisson’s ratio performance, also called auxetic, which can offer a great advantage in morphing mechanism. Based on fundamental work about re-entrant quadrangular lattices, the scheme of morphing airfoil is firstly given. Firstly, as shown in the FFT-based homogenization analysis, the enhanced re-entrant lattice outperforms remarkably the original one in stiffness and has similar flexibility. The mechanical characteristics of morphing airfoil with auxetic lattice core are the focus of our paper, which are investigated by using the finite element model. The design loads are extracted from the aerodynamic loads, which are converted to effective nodal loads distributed in the airfoils. The estimated natural model frequencies are given using the model analysis method, which accords with the limits. Furthermore, the compliance performances of the airfoil are investigated under passive and active morphing, respectively. The morphing airfoil with auxetic lattices has the advantages of high deformable, ease of control, variable stiffness, and the ability to bear large amounts of stress. These works offer researchers and designers novel ideas for designing morphing aircraft.
KeywordsMorphing airfoil Re-entrance lattices Auxetic Stiffness
The authors are grateful for the support provided by National Key R&D Program of China (No. 2017YFB0103204), Natural Science Foundation of Shanghai (No. 18ZR1440900) and Chinese Scholarship Council (No. 201706260056).
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