Linearized global and local buckling analysis of sandwich struts with a refined quasi-3D model

The global and local buckling of sandwich panels under uniaxial compression is discussed in the framework of classical linearized stability analysis. A refined two-dimensional (2D) plate model is constructed by postulating a layer-wise kinematics within a partially mixed variational statement. The 3D constitutive law is retained, and the interface continuity conditions of both displacements and transverse stresses are exactly satisfied. A Navier-type closed-form solution is adopted for the considered case studies, which solves the 2D equilibrium and compatibility equations in strong form. A comparison against full 3D results obtained by commercial finite element analysis and from open literature shows that the proposed solutions yield quasi-3D accuracy. A comprehensive assessment is given of the geometric and mechanical parameters defining the stability limit of sandwich struts, such as the thickness and stiffness ratios between face sheets and core as well as their orthotropy ratio. Moreover, the effects are discussed of von Kàrmàn’s assumptions and of the definition of the buckling preload in terms of uniform strain or stress.