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A study of the influence of uniform crystallization on the mechanical response of polymers and polymer-matrix composites
Abstract
This study investigates the influence of crystallization on the mechanical response of polymers under different loading conditions. Crystallization is an inherent characteristic of many polymers such as polyethylene, nylon and natural rubber. The continuous microstructural change associated with the process of crystallization induces macroscopic deformations, and increases the toughness and rigidity of the polymer. The present study is composed of three independent parts. The first part is an evaluation of the homogeneous creep response of polymers under both simple shearing and plane strain shearing. In each case the governing equation becomes an integral equation to be solved for the shear strain. Results are shown for the effects of crystallization on creep, residual shapes, and mechanical moduli. The second part focuses on simulating the effects of homogeneous crystallization on the distribution of residual stress and on the development of anisotropic and inhomogeneous mechanical moduli in a polymer containing a spherical inclusion or void and under spherically symmetric loading, or containing a cylindrical inclusion or void and under plane axially symmetric loading. The third part is devoted to numerically simulating the response of polymers during crystallization under plane strain conditions. The numerical procedure is composed of integration over the degree of crystallization and solving an inhomogeneous-anisotropic-incompressible-large deformation and plane strain elasticity problem at each fixed amount of crystallization. A basic finite element formulation is developed using a predictor-corrector method and least square error minimization. Two example problems are considered: (1) evaluation of the effect of crystallization on homogeneous creep under constant uniaxial traction, (2) simulation of stress distribution due to homogeneous crystallization in a square block of polymer which contains at its center a rigid cylindrical inclusion and is loaded by the application of a fixed displacement or a fixed traction on two opposite sides of the block. The redistribution of stress during crystallization is presented in terms of the maximum principal stress, the average stress and the maximum shear stress.
Subject Area
Mechanics|Polymers
Recommended Citation
Ma, Ruojuan, "A study of the influence of uniform crystallization on the mechanical response of polymers and polymer-matrix composites" (1994). ETD collection for University of Nebraska-Lincoln. AAI9516588.
https://digitalcommons.unl.edu/dissertations/AAI9516588