Scale effect on the nonlinear vibration of piezoelectric sandwich nanobeams on Winkler foundation

Purpose: Goal for the present research is investigating the effect of scale effect on free vibration of piezoelectric sandwich nanobeams on Winkler foundation. For this purpose, the effects of nonlocal parameters and strain gradient parameters on the free vibration of the model are studied. Methods: Based on the nonlocal strain gradient theory and Timoshenko beam theory, the nonlinear vibration of piezoelectric sandwich nanobeams on Winkler foundation is investigated. The nonlinear governing equations and boundary conditions are derived using the Hamilton's principle. The partial differential equation is transformed into ordinary differential equation by Galerkin's method, and then the nonlinear vibration of piezoelectric nanobeam is numerically analyzed using the Runge-Kutta method. Results and Conclusions: The results show that the nonlinear frequency ratio decreases with the increase of length-to-thickness ratio. When the nonlocal parameter is not less than the strain gradient length scale parameter, the piezoelectric nanobeam exhibits stiffness softening effect. When the nonlocal parameter is not greater than the strain gradient length scale parameter, the piezoelectric nanobeam exhibits stiffness hardening effect. It is also observed that both large length-to-thickness ratios and shear deformation can attenuate the nonlocal strain gradient effect. In addition, changes in the external applied voltage have a significant effect on the natural frequency of the piezoelectric nanobeams and increasing the thickness of the piezoelectric layer can enhance the structural stiffness.