Biaxial wrinkling analysis of composite-faced sandwich plates with soft core using improved high-order theory

•Improved high-order theory is used for biaxial wrinkling analysis of sandwich plate.•Continuity conditions for transverse shear stresses at the interfaces are satisfied.•Zero transverse shear stresses on the plate upper and lower surfaces are satisfied.•The dimensionless wrinkling loads decrease with increase in load ratio.•For K ≤ 1.15, the wrinkling waves only propagated along x direction.

In the present paper, an improved high-order theory is used for wrinkling analysis of sandwich plates with soft orthotropic core. Third-order plate theory is used for the facesheets and quadratic and cubic functions are assumed for transverse and in-plane displacements of the core, respectively. Continuity conditions for transverse shear stresses at the interfaces as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the plate are satisfied. The nonlinear Von-Karman type relations are used to obtain strains. Also, the transverse flexibility and transverse normal strain and stress of the orthotropic core are considered. The equations of motion and boundary conditions are derived by principle of minimum potential energy. Analytical solution for static analysis of simply supported sandwich plates under biaxial in-plane compressive loads is presented using Navier's solution. The effect of geometrical parameters of the facesheets and the core and the biaxial loads ratio are studied on the buckling and wrinkling behavior of sandwich plates. Comparison of the present results with the published results in the literature for the special case, confirms the accuracy of the proposed theory. Results showed that the increase in the biaxial load ratio, cause to change the direction of wrinkling wave propagation.