A size-dependent shear deformable computational framework for transient response of GNP-reinforced metal foam cylindrical shells subjected to localized impulsive loads

Abstract

In this study, the transient responses of functionally graded graphene nanoplatelet reinforced porous cylindrical microshells subjected to time-dependent localized distributed impulsive loads are investigated for the first time. The impulsive loads act vertically on the outer surface of the shell. The shell comprises graphene-nanoplatelet (GNP)-reinforced metal foam. In the current work, the internal pores are uniformly distributed with the graphene nanoplatelets, according to a given distribution, either uniformly or non-uniformly dispersed in the thickness direction of the shell, resulting in graded material properties. The effective elastic modulus of the nanocomposite is evaluated using the modified Halpin–Tsai micromechanics model combined with the extended rule of mixtures. A closed-cellular metal foam model is implemented to determine the mechanical properties of the porous nanocomposite. A modified couple stress-based hyperbolic shear deformable model is developed and implemented to capture the microstructure dependency of the mechanical behavior. The Lagrange equations in conjunction with double trigonometric functions are applied to derive the equations of motions of the microshells with simply supported boundary conditions. Further, the time-dependent dynamic responses are computed via modal superposition and the Newmark direct integration scheme. In the parameter study, the dynamic deflections of the microshell produced by various types of localized loads are compared, with the effects of internal pores, GNP distribution patterns, and external load parameters examined. It is found the circular-type and square-type localized loads yield very similar dynamic deflections. When adding a higher content of GNPs into the matrix, dispersing more GNPs near the top and bottom surfaces of the shell can effectively strengthen the shell stiffness, thereby considerably reducing the peak values of dynamic deflection.