Plastic Deformation Mechanisms of Semicrystalline and Amorphous Polymers

We use large-scale molecular dynamics simulations to investigate plastic deformation of semicrystalline polymers with randomly nucleated crystallites. The strain-softening regime is dominated by deformation of crystallites via reorientation of chain-folded lamellae toward the tensile axis, fragmentation of largest crystalline domains, and a partial loss of crystallinity. The strain-hardening regime coincides with unfolding of chains and recrystallization as a result of strain-induced chain alignment. These observed deformation mechanisms are consistent with experimental findings. We compare the tensile behavior of semicrystalline polymers with their amorphous counterparts at temperatures above and below the glass transition temperature.