A model for the elastoplastic behavior of isotactic poly(propylene) below the yield point

Observations are reported on isotactic poly(propylene) (iPP) in a series of tensile loading-unloading tests with a constant strain rate at room temperature. A constitutive model is developed for the elastoplastic behavior of a semicrystalline polymer at isothermal uniaxial deformations with small strains. The stress-strain relations are determined by 5 adjustable parameters which are found by fitting the experimental data. [GRAPHICS] The stress sigma (MPa) versus strain epsilon in a tensile loading-unloading test with the maximum strain epsilon(max) = 0.09. Circles: experimental data. Solid line: results of numerical simulation.