Micro-, meso- to macroscopic modeling of deformation behavior of semi-crystalline polymer

To represent the elasto-viscoplastic deformation behavior of semi-crystalline polymer (SCP), which has a complicated hierarchical structure, a micro-, meso- to macroscopic computational model was developed. A laminar composite model and FE-based homogenization method were used to relate the mechanical behaviors in micro- to mesoscopic and meso- to macroscopic scales of the material. Using the proposed model, elasto-viscoplastic deformation behaviors of high density polyethylene under several macroscopic boundary conditions were computationally investigated. Material's parameters used in the constitutive equations for microstructure of SCP were defined by fitting the calculated stress-strain relation into the experimental data. Then, the effects of deformation mode and crystallinity on deformation behavior of SCP were investigated. Obtained stress-strain relations represented the experimentally observed characteristics such as an anisotropic strain hardening rate depending on the deformation mode and an increase in the Young's modulus and the flow stress with the crystallinity. Then, the neck propagation process in the uniaxial tension with different strain rate was investigated. The present model represented a development of macroscopic non-uniform deformation characterized by the mechanical response of micro- to mesoscopic deformation.