Abstract The assessment of the differences in results obtained from various micromechanics homogenization schemes, as well as the implications of assuming different volume fraction profiles was carried out in the present work. The functionally graded composite chosen for the analysis was Al-SiC and comparisons were made in terms of stress and strain distributions along the wall of an internally pressurized hollow cylinder. Different micromechanics homogenization schemes were implemented into Abaqus as user-defined subroutines (UMAT). The numerical simulations were compared to a set of analytical solutions available on the literature. The obtained results varied substantially according to the homogenization scheme employed. It was also found that the type of function chosen to describe the volume fraction distribution plays a major role on the development of the hoop stresses. Additionally, the finite element analysis showed significant stress variation when the actual volume fraction distribution was used. These gradients did not appear when the same profile was approximated by smooth exponential functions. This paper points out some important issues related to common practices associated with the analysis of FGM composites and serves as an overture to a more in-depth discussion of such problems.

Abstract The use of thin-walled composite beams in Engineering has attracted great interest in recent years. Composite beams and other structural elements tend to have thin walls due to the high strength of the material. Other important aspect is that, even without reaching large strains and without overcoming the elastic limit of the material, such as beams present geometric nonlinear behavior due to their high slenderness, leading to large displacements and rotations. In this paper, a three-dimensional frame finite element for geometric nonlinear analysis of thin-walled laminated composite beams is presented. The finite element uses the Total Lagrangian formulation in order to allow the treatment of large displacements, but with moderated rotations. The constitutive matrix of the laminated beams is evaluated through a suitable thin-walled beam theory. In this theory, the effects of the couplings for several layups are considered, but the effects of the warping and transverse shear are neglected. Comparisons with numerical experiments demonstrate the very good accuracy of the proposed finite element.