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Author: Constantinescu, Andrei × Type: Report ×

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    Design and testing of 3D-printed micro-architectured polymer materials exhibiting a negative Poisson's ratio
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2019) Agnelli, Filippo; Constantinescu, Andrei; Nika, Grigor
    This work proposes the complete design cycle for several auxetic materials where the cycle consists of three steps (i) the design of the micro-architecture, (ii) the manufacturing of the material and (iii) the testing of the material. In more precise terms, we aim to obtain domain micro-architectured materials with a prescribed elasticity tensor and Poisson's ratio. In order to reach this goal we use topology optimization via the level set method for the material design process. Specimens are manufactured using a commercial stereo-lithography Ember printer and mechanically tested. The observed displacement and strain fields during tensile testing obtained by digital image correlation match the predictions from the FE simulation.
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    Design of thin micro-architectured panels with extension-bending coupling effects using topology optimization
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2021) Agnelli, Filippo; Nika, Grigor; Constantinescu, Andrei
    We design thin micro-architectured panels with programmable macroscopic behaviour using inverse homogenization, the Hadamard shape derivative, and a level set method in the diffuse interface context. The optimally designed microstructures take into account the extension-bending effect in addition to in-plane stiffness and out-of-plane bending stiffness. Furthermore, we present numerical examples of optimal microstructures that attain different targets for different volume fractions and interpret the physical significance of the extension-bending coupling. The simultaneous control of the in-plane, out-of-plane and their coupled behaviour enables to shift a flat panel into a dome or saddle shaped structure under the action of an in-plane loading. Moreover, the obtained unit cells are elementary blocks to create three-dimensional objects with shape-morphing capabilities.