Study on the nonlinear bending behavior of soft slabs subjected to vertical compressions

Abstract

Finite bending of soft materials exists in large deformation and great curvature, which correspond to high nonlinearity. It is challenging to investigate such a bending problem using the traditional three-point or four-point bending tests due to giant deflections. This paper provides a new way to study the large bending deformation of a soft slab subjected to vertical compression between two rigid plates. We fabricated three types of PDMS slabs with different stiffnesses and then placed them vertically between two rigid plates. By decreasing the distance between the plates, we can induce bending deformation in soft slabs. The compressive force between the plates is measured with a force transducer while a camera calibrates the deformation with the assistance of CAD software. We used two effective sizes of soft slabs, and each size corresponds to three different ratios of base material and curing agent material. We find that the slab’s deformed inner and outer radii only depend on the slab size rather than the stiffness, and the stretches are independent of both the size and stiffness. A simple linear model and finite element analysis are developed to explain the experimental data. They agree well with each other at finite bending. We, therefore, find that the center portion of the compressive soft slabs is approximately in pure bending. This paper provides an effective way to induce bending deformation in soft slabs and study the nonlinear behaviors.