▎ 摘　　要

A new model of microplate is used to evaluate the vibrational response of a size-dependent three-layered sandwich structure, including functionally graded (FG) composite core by sinusoidal shear deformation plate theory. Also, this FG core is reinforced by graphene nanoplatelets (GPLs) and embedded between piezo-electromagnetic (PEM) face sheets. The matrix of the core is made of Epoxy and the extended rule of mixture (ERM) besides Halpin-Tsai model is chosen to predict the mechanical properties of the nanocomposite core. Moreover, BaTiO3-CoFe2O4 composition is considered as constituting material of PEM face sheets. Furthermore, the visco-Pasternak substrate is used to carry the whole structure. The aforementioned theories are employed efficiently to obtain motion equations. Finally, the vibrational response of the described model due to the different parameters' variations is presented in tables and figures. Based on the results, temperature difference leads the structure to become stiffer and accordingly reduces the frequency. Moreover, using a square basis for a sandwich structure makes the lowest frequency and consequently stiffness.