Statistical energy analysis of the transmission loss of sandwich and laminate composite structures

Abstract

The present study emerges from a present industry need for accurate and fast numerical modeling approaches to estimate the vibro-acoustic behaviours of multilayered composite and viscoelastic treatments configurations.The structure is modeled using a wave approach applied to various multilayer configurations such as: symmetrical laminate composite, symmetrical sandwich composite and general symmetrical or unsymmetrical laminate or sandwich composite as well as viscoelastic treatments. Three behavioural modeling approaches are investigated: smeared laminate, discrete layer sandwich and general discrete layer laminate. Smeared laminate approach is devoted to symmetrical laminate composite panels and uses equivalent elastic properties computed by smearing out the layers' properties through the panel's thickness. Discrete layer sandwich approach is devoted to symmetrical sandwich composite panels and uses individual displacement fields for each layer. Classical assumptions of thick skins sandwich panels are adopted. General discrete laminate approach accommodates both laminate and sandwich composite panels of symmetrical or unsymmetrical layout. Individual displacement fields are used for each layer. These three behavioural modeling approaches are applied in the present work to flat and curved panel configurations as well as laminated beams. Dispersion relations are developed for each configuration and solved in a generalized polynomial eigenvalue problem context. These solutions are used in a SEA framework to compute the group velocity, the modal density, the radiation efficiency as well as the resonant and non-resonant contributions to the transmission coefficient. Moreover, the dispersion relations are used to develop general expressions to compute the ring frequency and the critical frequencies. In the context of viscoelastic treatments modeling the mechanical impedance, the input mobility, the deformation energy as well as the equivalent loss factor are computed for several boundary conditions.The presented approaches are successfully validated with experimental results and previously published theories. In addition to their proven accuracy, the proposed approaches are quick and general.