Fluid–structure interaction analysis of sound transmission through composite plates in convected fluid environments

A full layerwise analytical framework is developed to investigate sound transmission loss (STL) and vibro-acoustic response of laminated composite plates subjected to obliquely incident acoustic waves and an external mean flow. The formulation incorporates complete three-dimensional stress fields with interlaminar continuity. Hamilton's principle is used to couple the structural equations to acoustic wave equations for stationary and convecting inviscid fluids. Closed-form harmonic solutions are obtained for infinite plates allowing efficient prediction of structural response and acoustic transmission characteristics. The model is validated against literature solutions and First-Order Shear Deformation Theory. Parametric studies were conducted. A key finding is that increasing the Mach number from zero to a moderate value delays the coincidence dip in frequency. This effect cannot be captured without flow. The mean flow moves the acoustic field. It alters how wavenumbers match and shifts the coincidence frequency. Air flow adds effects that vary with frequency and angle. These effects change the plate dynamic stiffness. Such stiffness changes are not found in stationary fluids. Thickness significantly enhances STL and lowers the coincidence frequency. The interaction between flow direction and fiber orientation produces notable differences in transmission for opposite propagation directions. This is a purely fluid–structure coupling effect. It does not occur in stationary fluid or vacuum. Compared with equivalent single-layer theories, the layerwise formulation provides superior predictive accuracy. This is especially true near and beyond the coincidence region. These results demonstrate that the proposed layerwise approach captures essential fluid–structure physics that simpler models ignore.