Multiscale plasticity simulation considering spherulite structure of polypropylene

Abstract

Polymeric materials are divided broadly into two categories, amorphous and crystalline polymers. Polypropylene (PP) is widely used from daily necessities to machine parts because of its high formability and light weight. PP that is classified as a crystalline polymer has the following multiscale structures. Lamellae consisting of amorphous and crystalline phases grow radially and spherulites are generated. PP is filled with the spherulites, whose size and crystallinity are determined by molding conditions. Many researchers have studied the deformation of crystalline polymeric materials. However, many points remain unclear, such as the effects of multiscale structures on the material and mechanical properties of the crystalline polymer. A computational model reproducing the properties of PP based on multiscale structures is desired in the materials science and engineering fields. In this study, we perform a polymer plasticity simulation considering a spherulite structure consisting of amorphous and crystalline phases in order to investigate the effects of the amorphous and the crystalline phases of PP on macroscopic stress-strain behavior. PP samples with different crystallinity are prepared by changing the cooling conditions. Information on the crystallinity of specimens based on the experiment results is introduced into a computational model. We thoroughly investigate the effect of spherulite structures on the material properties of PP.

Keywords

• high polymer materials
• finite element method
• amorphous
• law of mixture
• constitutive equation
• stress-strain measurement
• plasticity
• spherulite
• polypropylene