Stability of cylindrical sandwich shells - experiments

This paper is a second part of an investigation to the stability of sandwich cylinders. Alternatively to a cylindrical steel shelf a sandwich shell was analyzed with regard to the stability. The sandwich shell consists of an inner and outer steel face, which are bonded adhesively to different core materials between them. Two grout and one elastomer core were investigated in this study. In comparison with linear buckling analyses the validity of a laminate composites shell theory was proven. Within a test series the stability of sandwich shells was analyzed against shell buckling due to axial compression and compared to tests with steel shells. Optical measurements were used to record the geometrical imperfections and to import the imperfect geometry of such shells in FE-models. Furthermore, a comparison of critical buckling loads was carried out with numerical solutions. The test series show a significant increase in bearing loads for the sandwich cylinders, which depends on the compressive strength of the core materials. The sandwich shells with a grout as core material show a catastrophic post buckling like steel shells. In contrast to this the elastomer core supports a ductile post buckling. The failure criteria for all variants of tested sandwich shells is more a local failure due to the steel faces called face wrinkling and not a global shell buckling.