Multiscale simulation for crystalline polymer using inelastic response law based on free volume change and homogenization method of molecular chain plasticity

Most of polymers used as structural materials are crystalline polymers that are mixtures consisting of glassy and crystalline phases. In this paper, we propose a material model representing the deformation behaviors of both crystalline and glassy phases by use of a unified manner based on crystal plasticity theory. A homogenization method is introduced into the above model in order to carry out deformation analysis connecting macroscopic specimen and microscopic unit cell. Then a further multiscale simulation bridging three hierarchical material structures, i.e., molecular chain scale, lamellar crystal scale and practical macroscopic scale is conducted for a polypropylene plate subjected to tensile load. It is tried to reproduce formation and propagation of shear bands and to visualize directly orientation of molecular chains inside the macroscopic structure. The relationship on deformation behavior between macroscopic plate and unit cell is investigated. Moreover, an inelastic response law based on a probabilistic theory considering change of local free volume is adopted as a hardening law of glassy part so as to express characteristic mechanical properties, i.e., nonlinear viscoelastic response before initial yielding, strain softening after initial yielding and nonlinear strain recovery in unloading process in crystalline polymers. © 2013 The Japan Society of Mechanical Engineers.