1D strain rate-dependent constitutive model of UHMWPE: From crystalline network to fibrillar structure behavior

International audienceA combined experimental and analytical investigation has been performed to understand and predict the mechanical behavior of UHMWPE with different molecular weights: 0.6; 3.9 and 10.5 Mg.mol −1. These materials were tested to a wide range of strain rates using uniaxial compression tests on a servo-hydraulic testing machine (10 −4 to 10 s −1). A hyperelastic-viscoplastic approach based on a relevant physical basis was adopted to predict the mechanical behavior of UHMWPE. The key point of the proposed model is to capture the huge microstructural evolution which occurs during fibrillation (crystalline network collapse) through a mechanical coupling parameter between the confined amorphous phase and the crystal stacks. The description of the amorphous phase is split in two parts, confined and global macromolecular networks in order to account for experimental results such as the huge strain recovery observed even after large plastic deformation of UHMWPE. It is found that this model successfully describes the compressive hyperelastic-viscoplastic behavior of sin-tered UHMWPE for different molecular weights over a wide range of strain rates and can be qualitatively extended to high strain rate and tensile loading