The stability of the sandwich conical shell panel - the stress state analysis

The paper presents an analysis of the stress state in a sandwich open conical shell panel. The shells under consideration consist of two face-layers (facings, claddings) and a core layer. The facings are load-carrying, a core layer is lightweight and it resists transverse shear only. The facings are made of isotropic, compressible, work-hardening materials. The core is the greater part of the whole shell thickness (over 80 %). The shell under consideration is two-parametrical loaded. Pre-buckling deformation of the shell could occur within the elastic, elastic-plastic or plastic range. In order to determine the stress state which occurs during stability loss, the constitutive relations of the Nadai-Hencky deformation (NHd) theory, alongside the HMH (Huber-Mises-Hencky) yield condition, are accepted. The results obtained from the analysis show that during stability loss, the effective stress may temporarily decrease. Then the unloading and hardening phenomena could occur and this should be taken into consideration.