Improving soundproof characteristics of an FG-CNT–reinforced composite structure by adding a coating magneto-electro-elastic layer

This paper deals with sound propagation through a two-layer sandwich plate in which the carbon nanotubes with functionally graded (FG) distribution are coated by a thin layer of magneto-electro-elastic (MEE) materials. Firstly, the derivation of governing equations for each layer of the sandwich plate is followed according to the three-dimensional elasticity theory. In this regard, the relationship between the equations of motion for the layer, made of MEE materials, and the electric and magnetic potentials is established. Additionally, the effective properties of the nanocomposite layer are extracted by employing the rule of mixture. Afterward, the solution is finalized by employing the approximate layer and transfer matrix technique, in accordance with the definition of state space and sound transmission loss. In the next stage, to confirm the reliability of the derived relationships, three configurations of the panel are examined. Firstly, according to the obtained results, it is evident that adding a thin coating layer of triple-phase MEE materials effectively improves the sound insulation in the sandwich plate. Secondly, considering the electromagnetic boundary conditions can lead to a noticeable enhancement in the STL in the stiffness region. Moreover, the magnetic potential, compared to the electric one, is seen to be more effective on the acoustic radiation of the sandwich panel.