Vibration and acoustic radiation of composite plate in hygrothermal environments

The vibration and acoustic radiation characteristics of a composite laminated plate subjected to harmonic excitation in hygrothermal environments are studied. The laminated plate is constituted of arbitrary number of orthotropic layers. Considering the effects of hygrothermal stress and additional mass, the natural frequency formulations are derived from the first-order shear deformation theory and mode superposition approach, the sound radiation formulations are obtained by using Rayleigh integration. Furthermore, the equivalent coefficients of thermal expansion are obtained based on the equivalence of hygrothermal expansion. Numerical simulations obtained by the finite element method are used to verify the analytical solutions. It is observed that the natural frequencies decrease with the increasing of moisture content and temperature due to the effect of hygrothermal stress. Meanwhile, compared with the laminated composite plate with angle-ply, the effects of temperature on the natural characteristic, sound pressure level and the sound power of the laminated plate with cross-ply are more significant. The peaks of sound pressure level and sound power curves generally shift towards lower frequencies and this phenomenon is evident in the low frequency region.