Assessment of Equivalent Properties for Multilayered Panels

Résumé

The use of lightweight complex heterogeneous structures increased during the last years principally in the transportation sector (i.e., aviation and trains). This sector’s technology enhancement pursues reducing long-term CO2 emissions and increasing efficiency. Lightweight structures may have poor vibro-acoustic behavior and in designs with complex shapes and material heterogeneities, its vibro-acoustic modeling brings new challenges in terms of accuracy and computational cost. Techniques such as model order reduction, homogenization, mesh and meshless methods (with and without periodicity conditions) and energy methods are typically employed to tackle this problem. Within homogenization techniques, an equivalent properties strategy can be utilized to equivalently represent complex structures into more simple ones (for example, a single layer panel). The latter is named equivalent structure or carrier and it is responsible for representing certain conserved quantities of the original structure. This work aims to stress the use and limitations of two equivalent properties strategies applied to multilayered structures. Limitations provide insight into the potential applicability of these strategies in complex structures. In the first strategy, the carrier is represented by a single layer isotropic plate. Five frequency dependent equivalent properties (elastic and shear moduli, Poisson ratio, thickness and density) are obtained using the first three wavenumbers of the original structure. In the second one, the carrier is a thin orthotropic plate. Heading-angle-dispersion curves of the firstthree waves of the original structure areapproximated as an ellipse. From the latter, the frequency dependent equivalent parameters (in-plane and out-of-plane stiffness coefficients) are obtained. To verify the effectiveness of both strategies, five comprehensive examples of multilayered structures (an orthotropic single layer panel, isotropic and orthotropic sandwich panels and a fully asymmetric multilaminated) are presented. The effect of damping is also analyzed in the case of a sandwich panel with a viscoelastic core.