PARAMETRIC ANALYSIS OF A TRIPLE CORE PERIODIC UNIT CELL INCLUDING A MIDDLE RANDOM CORE
Résumé
In the last decades, the main issue concerning structures is related to weight constraint. Many solutions are available as composites or sandwich panels. Nevertheless, it seems that metamaterials such periodic structures focus a specific attention nowadays. In this field, honeycomb structures remain wide used solutions especially in the aerospace industry, but they exhibit a high stiffness-to-weight ratio leading to poor acoustic properties. Consequently, some new designs are created to obtain better acoustic indicators. In this context, this paper proposes to study a new kind of periodic structures using multi-layer core topology systems consisting on stacking layers made of different geometry of cores (auxetic, hexagonal, rectangular…). Several new parameters should be considered to fully understand the dynamic and acoustic behaviour. In this paper we will limit the study to rectangular core combined with a random core located in between. Consequently, we will stack 3 kind of cores: Rect-Random-Rect. The main objective of this study is to analyse the results of the parametric survey. All configurations are constraint to have the same surface density. The chosen acoustic indicator is the Sound Transmission Loss (STL). The transition frequency will be also investigated as well as the compression and shear modulus and the bending waves. Modelling these structures is possible using either Wave Finite Element Method (WFEM) only or combining WFEM and the Transfer Matrix Method (TMM). We assume an infinite panel, real wavenumbers and that the structure is excited by plane waves with the angles of incidence and reflection equal. The model is implemented using MATLAB and ANSYS apdl. Because such structures are made using a 3D printer, the ABS is used as the material for the study. From the parametric study, it turned out that multi-layer core systems correspond to relevant solutions to highly improve the STL. Moreover, it is possible to find out an optimized design giving the best STL. However, as it will be shown, it goes along with less efficiency in terms of mechanical properties and thus should be relevant for some specific applications.
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