Computed Tomography-based Modeling of Structured Polymers

Abstract

A hybrid numerical-experimental approach is proposed to characterize the macroscopic mechanical behavior of structured polymers. The method is based on capturing the details of the material's microstructure using 3D X-ray Computed Tomography (CT). By employing segmentation and voxel-conversion, the reconstructed volume is automatically converted into a finite element model that is subsequently used for mechanical analyses. The approach is demonstrated on a 2D polycarbonate (PC) honeycomb. An ideal representative volume element (RVE), with a volume equivalent to the volume of the real X-ray CT-based model, is used to determine the dependence of the macroscopic response of the structure on intrinsic material behavior, strain rate, and cell wall thickness. A nonlinear elasto-viscoplastic constitutive model is used to describe the intrinsic behavior of the PC base material and a comparison with a hyperelastic material model reveals that local plastic deformation significantly influences the macroscopic behavior. A cubic relation between the stiffness of the structure and cell wall thickness is found, whereas the strain rate has a minor influence. The ideal RVE shows a different response compared to the real X-ray CT-based model due to local variations of the cell wall thickness in the latter, causing nonhomogeneous deformations. In addition to the geometric imperfections, jagged edges, as a consequence of voxel conversion, contribute to this local variation in cell wall thickness.