Micromechanical modeling of intraspherulitic deformation of semicrystalline polymers

Semicrystalline polymers often show a spherulitic morphology, consisting of a radial assembly of twisted crystalline lamellae and amorphous layers. A multiscale numerical model is used to investigate the mechanics of intraspherulitic deformation of polyethylene. The model establishes links across the microscopic, the mesoscopic, and the macroscopic levels. Constitutive properties of the material are identified for the crystallographic and amorphous domains. The averaged fields of an aggregate of individual phases, having preferential orientations, form the constitutive behavior of intraspherulitic material. The spherulitic macrostructure is described by finite element models. The macroscopic stress–strain response resembles that of a previous random polycrystalline model. However, the current model includes the geometrical effect of the anisotropic structure within a spherulite, causing strain concentrations in the centers, which spread out in the equatorial region for uniaxial loading conditions and in inclined directions for plane strain loading. The deformations are linked to microstructural processes as interlamellar deformation and intralamellar crystallographic slip.