Mechanics of large-strain deformation of particle-modified polymers

Abstract

Over the past several decades, engineering polymers have become increasingly prevalent in the manufacture of virtually all types of products. Polymers are substantially less dense than metals, easy to machine, and readily formed into quite complex geometries. The properties of polymers may be altered by the introduction of second-phase particles. Typically, soft, rubber particles are added to increase fracture toughness while rigid, mineral particles are added to reduce costs or to increase stiffness, thermostability, or porosity. The deformation to large strains of particle-modified thermoplastic polymers is investigated. Blends with rubber particles and blends with calcium carbonate particles are considered. A novel experimental technique is utilized to characterize the three-dimensional deformation of polycarbonate blends and high-density polyethylene blends during uniaxial tension tests. True stress, true strain, volumetric strain, and full-field contours of strain are extracted from images of the deforming specimens. The experimental results are used to construct and verify single-particle and multi-particle micromechanical models.

(cont.) In the micromechanical models, the stress triaxiality ratio and the properties of the particles, matrix, and interfaces are varied in order to determine their effects on local and macroscopic deformation. A constitutive model for polymers with perfectly bonded or debonding rigid particles is developed based on the knowledge gained from the experiments and micromechanical models.