A new nonlinear model for studying a sandwich panel with thin composite faces and elastic–plastic core

• An new non-linear model is developed for studying elastic–plastic behavior of a sandwich beam.
• The governing equations are derived using higher order sandwich panel theory.
• Different boundary conditions are studied.

In this paper elastic–plastic behavior of a sandwich beam with a transversely flexible core and thin faces is investigated. The elastic–plastic behavior of the core is described by a bilinear constitutive relation of the shear stress. The governing equations for linear and nonlinear regions are derived using higher order sandwich panel theory. The governing equations are solved by finite element method based on the Galerkin weighted residual method. Since the limits of the plastic regions spread through the solution, an iterative procedure is employed to obtain reliable results. Three different boundary conditions including simply supported, clamped and three point bending configurations are studied. The results are compared with the available results in literatures and a good agreement can be seen. The results reveal that as the bilinear ratio decreases the maximum of the shear stress decreases and the plastic region extends. Comparing different boundary conditions shows that by increasing the constraint of the edges, the maximum of shear stress decreases. In addition, the plastic regions spreads by decreasing bilinear ratio and the maximum growth is belonged to clamped configuration.