Dynamic and acoustic properties of viscoelastic laminated structures

Numerical computation of wave characteristics in composite laminated structures is obtained using a Wave Finite Element method. The method involves conventional finite element (FE) analysis of a small segment of the structure. Typically, this consists of a stack of solid elements meshed through the cross-section. Each layer can be discretised using either one solid element or more solid elements. The analyst must select element type and number appropriately in order to accurately model the three-dimensional stress-strain state of the structure (in the context of FE analysis). The advantages of the proposed method are that it involves post-processing of a small FE model, commercial FE packages can be used to generate the model, no new elements need to be derived and implemented, and the computational cost is extremely small. Axisymmetric properties of the structure can be exploited, and the method can take advantage of the capability of commercial FE packages to model acoustic fluids and fluid-structure interaction. The method is described and illustrated by application to a laminated viscoelastic sandwich panel in vacuo and a laminated viscoelastic sandwich cylinder filled with fluid. Complex dispersion curves and wave modes are given. The global loss factor as a function of the frequency is also predicted, and the effect of the initial pre-stress is discussed.