Torsional buckling of graphene platelets (GPLs) reinforced functionally graded cylindrical shell with cutout

This paper studies the torsional buckling of functionally graded cylindrical shells reinforced with graphene platelets (GPLs) through finite element method (FEM). The cylindrical shell is consisted of a number of layers in the thickness direction, in which the GPL concentration varies from layer to layer. The Young's modulus and Poisson's ratio of the composites are determined by Halpin-Tsai model and rule of mixture, respectively. The FEM model is validated by comparing present results with theoretical predictions for homogeneous shells. Parametric study is carried out to investigate the effects of the number of layers, the GPL distribution patterns, the dimensions of shell, the weight fraction and size of GPLs, and the existence of cutout on torsional buckling. The results demonstrate using multi-layers is accurate enough to obtain functionally graded structures. GPL distribution plays a significant role in the buckling. Increasing the number of layers significantly decreases the stress gradient between two adjacent layers. Square shaped GPLs with fewer layers are preferred as reinforcements. With the increase of cutout size, the buckling load decreases and the structure undergoes the transition from global to local buckling mode. Moreover, the effects of the slenderness, orientation and position of the cutout on buckling are examined.