MICRO-MECHANISM BASED VISCOPLASTIC CONSTITUTIVE MODEL FOR ANISOTROPIC PROPERTIES OF SEMI-CRYSTALLINE POLYMER

Crystalline polymer materials are being increasingly used to replace many structural and non-structural metal components due to their low cost, lightweight, and ease of processing. A deeper understanding of their anisotropic mechanical behavior contributes to their wider engineering applications. In this study, a homogenization-based constitutive model for anisotropic viscoplasticity of semi-crystalline polymers is developed. Firstly, constitutive models for viscoplasticity and hyperelasticity are established separately for the crystalline and amorphous phases. Then, by volume averaging of layered inclusions composed of crystalline and amorphous phases, the macroscopic equivalent mechanical properties of semi-crystalline polyethylene considering the influence of temperature and strain rate are established. The developed constitutive model is experimentally calibrated and validated, and applied to analyzing the uniaxial and biaxial tensile mechanical properties of polyethylene under different conditions. Numerical studies discuss the effects of loading direction and crystallinity on the mechanical properties of polyethylene materials. The research enriches and advances the heterogeneous inclusion models and provides a theoretical basis for promoting the application of semi-crystalline polymers in various fields.