Capillary control of collapse in soft composite columns

Euler buckling is the elastic instability of a column subjected to longitudinal compressing forces at its ends. The buckling instability occurs when the compressing load reaches a critical value and an infinitesimal deflection leads to a large amplitude deflection. Since Euler's original study, this process has been extensively studied in homogeneous, isotropic, linear-elastic solids. Here, we examine the nature of the buckling in inhomogeneous soft composite materials. In particular, we consider a soft host with liquid inclusions both large and small relative to the elastocapillarity length, which lead to softening and stiffening of a homogeneous composite respectively. However, by imposing a gradient of the volume fraction or varying the inclusion size we can deliberately manipulate the nature of Euler buckling.