Nonlinear vibration of functionally graded fiber-reinforced composite laminated cylindrical shells in hygrothermal environments

Abstract

The effect of hygrothermal conditions on the linear and nonlinear free flexural vibration of anisotropic shear deformable laminated cylindrical shells is investigated. The cylindrical shell is made of fiber-reinforced composites (FRCs) with the reinforcement being distributed either uniformly (UD) or functionally graded (FG) of piece-wise type along the thickness of the shells. The motion equations are based on a higher order shear deformation shell theory with a von Kármán-type of kinematic nonlinearity. The hygrothermal effects are also included, and the material properties of FRCs are estimated through a micromechanical model and are assumed to be temperature-dependent and moisture-dependent. The equations of motion are solved by a singular perturbation technique along with a two-step perturbation approach to determine the linear and nonlinear frequencies of the FRC laminated cylindrical shells. Detailed parametric studies are carried out to investigate effects of material property gradient, the temperature change, the degree of moisture concentration, shell geometric parameter, stacking sequence, as well as the end conditions on the vibration characteristics of FRC shells with polymer matrix. The results show that the temperature/moisture variation has a moderately effect on the natural frequencies of the FRC cylindrical shells, but only has a small effect on the nonlinear to linear frequency ratios of the same shell.