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The nonlinear free vibration and transient response of laminated composite cylindrical and spherical shells with imperfection in hygrothermal environments is studied using the finite element method. The theoretical formulations are based on the first-order shear deformation theory and von Kármán-type nonlinear kinematics. An imperfection function capable of modeling a variety of sine type, global type, and localized type imperfections is used. The analysis is carried out using quadratic C0 eight-noded isoparametric element. The governing nonlinear equations are solved using the direct iteration method for the eigenvalue problem for free vibration and Newmark average acceleration method in the time integration in conjunction with modified Newton—Raphson iteration scheme for transient analysis. The validity of the model is demonstrated by comparing the present results with those available in the literature. The effects of moisture, temperature, amplitude of imperfection, and imperfection types on the nonlinear free vibration and transient responses of laminated composite shells are studied.

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