Mullins’ effect in semicrystalline polymers

Observations are reported on isotactic polypropylene in uniaxial cyclic tensile tests at room temperature. A model is derived for the viscoplastic response of semicrystalline polymers at three-dimensional deformations with small strains. Adjustable parameters in the stress–strain relations are found by fitting the experimental data. It is shown that polypropylene reveals some characteristic features of the Mullins effect that can be quantitatively predicted by the constitutive equations.