A new nonlinear high order theory for sandwich beams: An analytical and experimental investigation

The paper presents a geometrically nonlinear sandwich panel theory for orthotropic sandwich beams in which the large deformation of face sheets and core is considered. The equations are derived based on high order sandwich panel theory in which the Green strain and the second Piola–Kirchhoff stress tensor are used. Nonlinear equations for a simply supported beam are derived using Ritz method in conjunction with minimum potential energy principle. The resulted set of equations is solved by the Newton–Raphson iterative technique. The results of numerical computation for beams in three point bending are presented and compared with experiments as well as with some other available results. Also simplification was used to obtain the results of linear model and in parametric studies the effect of geometric parameters on difference between results of linear and nonlinear models are discussed. Some experimental tests on sandwich beams with glass/epoxy face sheets and soft polymeric cores were performed. The experimental results of specimens with different arrangement support the claims which were based on analytical predictions about similarities and differences between linear and nonlinear models. In all cases good agreement is obtained between the nonlinear analytical predictions and experimental results.