یاسین حیدرپور

The transient thermoelastic behavior of functionally graded graphene platelets reinforced composite (FGGPLRC) spherical shells under thermo-mechanical loadings is studied based on the Lord-Shulman thermoelasticity theory, which includes the coupled as well as the nonlinear terms. The problem formulation is so prepared that both types of commonly used FG-GPLRC in the literature (i.e., multilayer FG-GPLRC, for which the material properties vary in a layerwise or piecewise continuous manner and those with continuously varying material properties) can be analyzed. The modified Halpin-Tsai micromechanical model, rule of mixture and a newly introduced micromechanical model are employed to estimate the effective thermo-mechanical properties of FG-GPLRC shells. The governing equations are discretized in the spatial domain using the layerwise differential quadrature method (LW-DQM). Then, a novel multi-step time integration scheme based on non-uniform rational B-spline (NURBS) in conjunction with Newton-Raphson algorithm are employed to solve the resulting system of nonlinear ordinary differential equations iteratively. In addition, the Laplace transform is employed to obtain the solution in the time domain. The method is validated by performing the convergence study and comparing the obtained results with available solutions in the limit cases. Afterward, the effects of the GPL distribution pattern, GPLs weight fraction and dimensions ratios, the shell thickness-to-outer radius ratio and suddenly applied thermo-mechanical loadings on the thermoelastic behavior of FG-GPLRC spherical shells are investigated. The results show that adding a very small amount of GPLs into polymer matrix significantly increase the shell stiffness and heat wave speed, and considerably changes the temperature and displacement distributions of the FG-GPLRC spherical shells.