Geometrically Nonlinear Response of Modern Sandwich Panels - Distributed Loads and Localized Effects

The article presents the results of an investigation on the role of the localized effects in the geometrically nonlinear response of modern sandwich panels made of a ‘soft’ core when subjected to distributed loads. The adopted nonlinear analysis approach incorporates the effects of the vertical flexibility of the core, and it is based on the approach of the high-order sandwich panel theory (HSAPT). The nonlinear governing equations are solved using the multipoint shooting method along with parametric and arc-length continuation procedures. The nonlinear response of the distributed loads is described in terms of deflections and stress resultants in the face sheets, as well as in terms of the interfacial stress components at the upper and lower face-core interfaces. In addition, the equilibrium curves of the load versus the extreme absolute values of the aforementioned structural quantities are presented. The numerical study investigates the localized effects involved in the case of a panel made of a core with uniform properties and a core that is reinforced at its mid region when subjected to a uniformly distributed loading. One of the findings of this research is that a typical modern panel exhibits a limit point response even when subjected to uniformly distributed loads that cause bending. The material discontinuity of the core as well as the buckling of the compressed face sheet leads to localized effects that significantly affect the nonlinear response.