Interacting defects affect the buckling of imperfect spherical shells

The presence, distribution, and interaction of defects dictate the buckling strength of shell structures. Even if the sensitivity of shell buckling to imperfections has long been recognized, to date, the successful prediction of critical loads is restricted to cases with a single defect, of known geometry. However, in reality, shells typically contain a distribution of defects and their interaction has not been well studied. In this talk, we will focus on spherical shells with multiple defects and study the role of defect interactions in dictating the buckling pressure. In the experiments, we fabricate polymeric shells containing two precisely engineered geometric defects through a customizable coating technique. We vary the relative size and location of these two defects and quantify the relationship between buckling pressure and defect distribution. The experimental results are then contrasted against finite element modeling (FEM) simulations. Upon validation of the numerics, we use FEM to perform a broader and more systematic exploration of the parameter space. Our results provide a better understanding of defect interactions, which we hope will put us on a step to better predict the buckling pressure of practical shell structures.