Hygro-thermal buckling of porous FG nanobeams considering surface effects

Hygro-thermal buckling of the porous FG nanobeam incorporating the surface effect is investigated. The even distribution of porosities is assumed in this paper. Various porous FG nanobeam models including classical beam theory (CBT), Timoshenko beam theory (TBT), Reddy beam theory (RBT), sinusoidal beam theory (SBT), hyperbolic beam theory (HBT) and exponential beam theory (EBT) are developed in this paper. The nonlocal strain gradient theory with material length scale and nonlocal parameters is adopted to examine the buckling behavior. The governing equations of the porous FG nanobeam are derived from principle of minimum potential energy. In the numerical examples, the effect of the nonlocal parameter, material length scale parameter, the temperature rise, the moisture concentration, surface effect, material gradient index, and porosity volume fraction on the buckling temperature and moisture are analyzed and discussed in detail. The results show that the stiffness of the beam depends on the relation of size between nonlocal parameter and length scale parameter. The paper will be helpful for the design and manufacture of the FG nanobeam under complex environments.