Airborne sound transmission loss and damping characteristics of fiber metal laminates with constrained viscoelastic interlayers

A sublaminate layer-wise approach is proposed based on the generalized high-order shear deformation theory coupled with the local coordinate mapping principle, so as to accurately evaluate the airborne sound transmission loss and damping characteristics of complex composite laminates with a constrained viscoelastic interlayer. The method not only allows for the independent selection of three-dimensional displacement fields for each geometric layer, which can effectively represent the discrete layer information, but also can equivalently condense multiple geometric layers with similar dynamic characteristics into a single layer to enhance computational efficiency. The approach also incorporates the frequency-dependent properties of viscoelastic materials into the acoustic-structural coupling equations, by employing an iterative modal strain energy method to solve complex eigenvalues. This approach is verified through comparisons with previously published experimental and computational results. This study investigates the sound transmission loss of fiber metal laminates under planar wave excitation at various incident angles at narrow frequency bands from 10 Hz to 2000 Hz, for discussing the damping contribution mechanism. The results show that constrained layer damping can significantly enhance sound insulation performance of the structure at resonance frequencies.