A Novel Phenomenological Constitutive Model for Semi-Crystalline Polymers Across a Wide Strain-Rate Range

Focusing on the complex mechanical responses exhibited by semi-crystalline polymers under the coupled influences of strain hardening, strain-rate strengthening, and temperature softening, this paper proposes a phenomenological constitutive model employing a three-branch parallel structure. Using a hybrid global optimization algorithm, the optimal parameters for polypropylene were identified, attaining a coefficient of determination of 0.9834 and controlling the average absolute relative error within 6.4%. Moreover, the effectiveness of the proposed constitutive model was accurately validated through two material models from the LS-Dyna software 4.8.29 database, and the simulation results exhibited high consistency with the theoretical model. This study provides a high-confidence material model suitable for high-strain-rate simulation scenarios.