Monotonous, symmetric, and nonsymmetric patterns of porous core in vibration study of nano-composite sandwich plate bonded by piezoelectric sheets

This paper deals with the free vibrations of a 5-layer sandwich plate consisting of a sutured porous material core. Two randomly oriented straight single-walled carbon nanotube (CNT) reinforced composites and face sheets manufactured of piezoelectric material that is subjected to an external electric voltage, are placed on a Visco-Pasternak foundation. The relationship between strain and stress in the core is expressed by considering the pore fluid pressure based on the Biot theory, and for pore distribution along the core thickness, three uniform, symmetric and nonsymmetric patterns are considered. A quasi-3D sinusoidal shear deformation theory which that couples the effects of shear strain and normal deformation without the need for any shear correction factor which uses Hamilton’s principle and Navier’s method is used to derive the governing equations of the sandwich structure for the simply supported case. Effects of different parameters on the natural frequencies of the plate are studied including layer thickness ratio, porosity parameter, porosity distribution pattern, pores compressibility, the volume fraction of CNTs and external voltage. The maximum frequency in different modes could be an important design factor that is calculated based on the type of the porosity distribution. Controlling the material properties based on specific needs is the most important advantage of the 5-layer sandwich structure. This paper introduces sandwich panels with porous cores, nanocomposite layers and piezoelectric overlays for the first time which is analyzed to determine system vibration frequencies under external voltage and by changing various parameters with emphasis on different porosity distributions. The frequency of monotonous distribution was 4% higher than symmetric and asymmetric distributions for a constant porosity.