Influence of axial load function and optimization on static stability of sandwich functionally graded beams with porous core

Static stability of beams subjected to nonuniform axial compressive and shear loads is essential in many industrial applications, such as aircraft, automotive, mechanical, civil and naval. Thus, this article tends to investigate and optimize critical buckling loads of thin/thick sandwich functionally graded (FG) beam with porous core, for the first time. The proposed model is developed to consider a sandwich beam with three layers, which has top and bottom FG layers reinforced by single-walled carbon nanotubes (SWCNTs) and core porous layer with various porosity distributions. The variable in-plane compressive load is described by different distributed functions. Parabolic higher-order shear deformation theory of Reddy is adopted to describe kinematic displacement field and consider both thin and thick structures. The equilibrium governing variable-coefficient differential equations are obtained in detail by generalized variational principle. Equilibrium equations are solved numerically by differential quadrature method to get critical buckling loads. Numerical results are illustrated to examine influences of porosity function, porosity percentage, distribution gradation index, load types and boundary conditions on buckling loads of sandwich FG SWCNTs beam with porous core. Particle swarm optimization algorithm is adopted to get optimal axial load function.