Geometrically nonlinear analysis of functionally graded power-based and carbon nanotubes reinforced composites using a fully integrated solid shell element

Functionally graded materials are multi-phase composites which are characterized by continuous and smooth variation of the volume fractions of two or more constituents within the structure domain. In this study, geometrically nonlinear analysis of functionally graded power-based (FGMs) and carbon-nanotubes reinforced composites (FG-CNTRCs) is performed using a fully integrated first-order solid shell finite element. This formulation relies on the alternative parametrization of the so-called 7-parameter shell model. The central aspects that motivate the use of this formulation are: (i) the use of unmodified three-dimensional constitutive laws, and (ii) the consideration of the thickness variation of the shell along the deformation process. Locking treatment is carried out by means of the combination of the Enhanced Assumed Strain (EAS) and the Assumed Natural Strain (ANS) methods. This solid shell element is numerically implemented into the commercial FE code ABAQUS through the user subroutine UEL. Several numerical examples are conducted with the aim of examining the effects of different material parameters on the structural response. These applications show the applicability of the current formulation for FG composite simulations undergoing geometrically nonlinear effects. (C) 2016 Elsevier Ltd. All rights reserved.