Multiscale modeling of particle-modified polyethylene

Abstract

A common practice in toughening of semicrystalline polymers is to blend them with second-phase rubber particles. A toughening mechanism has recently been suggested which considers a layer of transcrystallized material around well-dispersed particles. This layer has a reduced yield strength in certain preferentially oriented directions. A multiscale numerical model is used to investigate the effect of such a specific microstructural morphology on the mechanical behavior of voided systems. A polycrystalline model is used for high density polyethylene (HDPE) matrix material. The basic structural element in this model is a layered two-phase composite inclusion, comprising both a crystalline and an amorphous domain. The averaged fields of an aggregate of composite inclusions, having either a random or a preferential orientation, form the constitutive behavior of the polymeric matrix material. The anisotropy of material with preferential orientations is determined. The particle-dispersed system is described by finite element RVE models, with in each integration point an aggregate of composite inclusions. Transcrystallized orientations are found to have a limited effect on matrix shear yielding and alter the triaxial stress field. An hypothesized, flow-influenced, microstructure is shown to further improve material properties if loaded in the appropriate direction.