Thermal post-buckling of sandwich beams with functionally graded negative Poisson's ratio honeycomb core

This paper investigates the thermal post-buckling behavior of sandwich beams with functionally graded (FG) negative Poisson's ratio (NPR) honeycomb cores. Two symmetric FG configurations of re-entrant honeycomb cores along the beam thickness direction are proposed for the first time. The material properties of both face sheets and core of the sandwich beams are assumed to be temperature-dependent. The thermal post-buckling behavior and the variation of effective Poisson's ratio (EPR) of the sandwich beam in the large deflection region are studied by using 3D full scale finite element simulations. Numerical results are presented for the sandwich beams with FG-NPR honeycomb core under a uniform temperature field, from which results for the same sandwich beam with uniform distributed NPR honeycomb core are obtained as a comparator. The EPR-deflection curves are obtained for the first time, and the results reveal that greater bending stiffness could bring about higher EPR-deflection curve. The effects of functionally graded configurations, boundary conditions, facesheet-to-core thickness ratios, cell wall-to-facesheet thickness ratios and length-to-thickness ratios on the thermal post-buckling load-deflection curves and EPR-deflection curves of sandwich beams are discussed in detail.