▎ 摘　　要

An analytical method is developed to explore the wave propagation characteristics of piezoelectric sandwich nanoplates in the present work. The sandwich nanoplates are composed of a graphene reinforced composite core layer with two piezoelectric surface layers exposed to electric field. The material properties of the nanocomposite layer are given by the Halpin-Tsai model and mixture's rule. The Euler-Lagrange equation of the nanoplates is obtained by Hamilton's principle and first-order shear deformation theory. Then, combining the high-order nonlocal strain gradient theory with the hygrothermal constitutive relationship of composite nanoplates, the nonlocal governing equations are presented. Finally, numerical studies are conducted to demonstrate the influences of scale parameters, applied external voltage, temperature variation, moisture variation, graphene size, and weight fraction on wave frequency. The results reveal that low-order and high-order nonlocal parameters and length scale parameters have different effects on wave frequency. The wave frequency can be reduced by increasing temperature and the thickness of graphene. This could facilitate the investigation of the dynamic properties of graphene nanocomposite structures. Graphic abstract