Thermo-mechanical stress analysis of variable stiffness composite sandwich plates with auxetic honeycomb core using a higher-order zig-zag theory

The in-plane and transverse shear stresses in sandwich plates under thermo-mechanical loads are investigated here using a C 0 continuous nine-node plate bending element with eleven degrees of freedom per node. The finite element formulation is based on a higher-order zig-zag theory. The sandwich plate is made of variable stiffness composite facesheets and an auxetic honeycomb core. The in-plane stresses are calculated using constitutive relations, whereas the transverse shear stresses are computed using the equilibrium equations satisfying the continuity condition at layer interfaces. Results are validated for constant and variable stiffness composite laminates under thermo-mechanical loads. Thereafter, the in-plane and transverse shear stresses are presented for sandwich plates with VSCL facesheets and auxetic honeycomb core. The combined effect of honeycomb unit cell parameters (core angle and inclined cell rib length), geometric parameters (relative core thickness and span-to-depth ratio), lamination parameters (CSCL and VSCL), boundary conditions (simply-supported and clamped) and loading conditions (mechanical load, uniform heating, heating with through-thickness thermal gradient) on the stress distribution in sandwich plates is investigated for the first time.