Nonlinear bending of sandwich beams with functionally graded negative Poisson's ratio honeycomb core

This paper investigates the nonlinear bending behavior of sandwich beams with functionally graded (FG) negative Poisson's ratio (NPR) honeycomb core in thermal environments. The novel constructions of sandwich beams with three FG configurations of re-entrant honeycomb cores through the beam thickness direction are proposed for the first time. The temperature-dependent material properties of both face sheets and core of the sandwich beam are considered. 3D full scale finite element analyses are conducted to investigate the nonlinear bending behavior and the variation of effective Poisson's ratio (EPR) of the sandwich beam in the large deflection region. The numerical simulations are carried out for the sandwich beams with FG-NPR honeycomb core, from which results for the same sandwich beam with uniform distributed NPR honeycomb core are obtained as a comparator. Finite element results showed that the thickness change of sandwich beams with NPR honeycomb cores are distinctly out of ordinary, and the NPR sandwich beams have significantly lower load-bending moment curves compared with those with positive Poisson's ratio cores. The effects of functionally graded configurations, load distribution types, boundary conditions, temperature changes and length-to-thickness ratios on the bending load-deflection curves and EPR-deflection curves of sandwich beams are discussed in detail.