A Model for the Elastoplastic Behavior of Isotactic Poly(propylene) Below the Yield Point

Abstract

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. The stress σ (MPa) versus strain ε in a tensile loading‐unloading test with the maximum strain εmax = 0.09. Circles: experimental data. Solid line: results of numerical simulation.magnified imageThe stress σ (MPa) versus strain ε in a tensile loading‐unloading test with the maximum strain εmax = 0.09. Circles: experimental data. Solid line: results of numerical simulation.

Pre-yield tensile set of a semi-crystalline polymer, its blend and composite

“…As the tensile set is accompanied with a temperature rise of the sample a plastic deformation is taking place. The plastic deformation can be due to the deformation of the crystalline domains and/or the amorphous phase [9][10][11][12].…”

“…The yielding in semi crystalline polymers is very often accompanied by necking with an appreciable temperature rise [4][5][6][7][8]. For PE and PP it has been shown that the assumption that below the yield strain that the deformation in tensile is just nonlinear elastic, it too simple [9][10][11][12]. In cyclic deformation tests at low strains considerable tensile set was observed.…”