Buckling Knockdown Factors for Hemispherical Foam Core Sandwich Shells With Single Dimple

Abstract

In this study, nonlinear postbuckling analyses are performed using ABAQUS to derive the buckling knockdown factors (KDFs) for hemispherical foam core sandwich shells under external pressure. Two hemispherical foam core sandwich shells (dimple and flat models) with different inner sheet thicknesses are considered. The crushable foam modeling technique is used to represent the nonlinear compressive behavior of the foam material. The geometric initial imperfection modeling technique, the single dimple imperfection approach, is established to represent the geometric initial imperfection of the hemispherical foam core sandwich shells. The postbuckling analyses using the Riks method are carried out to predict the buckling behaviors of shells with geometric initial imperfections. The KDFs of the dimple and flat models are derived to be 0.20 and 0.22, respectively, which are up to 11.11% and 22.22% higher, respectively, than the previous NASA buckling design criteria. Therefore, the present KDFs provide a lightweight design for hemispherical foam core sandwich shells.