Evaluation of effective elastic properties of honeycomb sandwich structures by optimization involving modal behavior

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2014
Çınar, Okan
This thesis aims to develop an alternative approach which estimates the effective elastic properties of 2D orthotropic equivalent model of the honeycomb core material. For this purpose, 3D detailed finite element (FE) model of honeycomb structure, with the actual cell geometry and the face sheets, is used as the reference structure. Effective elastic properties of the equivalent 2D orthotropic model, representing the honeycomb core, are determined by means optimization. The objective function of the optimization is defined as the minimization of the error function expressed as the difference of the natural frequency results of certain number of modes of the reference 3D detailed FE model and the equivalent model of the sandwich structure with the honeycomb core. The effective material properties of the 2D orthotropic equivalent model of the honeycomb core are used as the design variables to optimize. The genetic algorithm that available in MATLAB Optimization Toolbox is used as optimizer, and MSC Nastran is used as the finite element solver to perform the modal analysis of the sandwich plates with honeycomb material as the core. Optimizer and the finite element solver are coupled by means of an interface code which is developed in the MATLAB environment. The studies in the literature, in which the effective material properties of the orthotropic equivalent model are estimated analytically, are also used for comparison purposes. Moreover, the effective material properties predicted analytically are used as the initial population of the optimization in genetic algorithm. The results show that developed approach predicts more accurate orthotropic effective material properties for the honeycomb than the present analytical models predict.

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Citation Formats
O. Çınar, “Evaluation of effective elastic properties of honeycomb sandwich structures by optimization involving modal behavior,” M.S. - Master of Science, Middle East Technical University, 2014.