Title:
Multiscale Modeling of the Deformation of Semi-Crystalline Polymers

dc.contributor.advisor Jacob, Karl I.
dc.contributor.advisor McDowell, David L.
dc.contributor.author Shepherd, James Ellison en_US
dc.contributor.committeeMember Qu, Jianmin
dc.contributor.committeeMember Tannenbaum, Rina
dc.contributor.committeeMember Zhou, Min
dc.contributor.department Mechanical Engineering en_US
dc.date.accessioned 2006-06-09T18:08:13Z
dc.date.available 2006-06-09T18:08:13Z
dc.date.issued 2006-03-29 en_US
dc.description.abstract The mechanical and physical properties of polymers are determined primarily by the underlying nano-scale structures and characteristics such as entanglements, crystallites, and molecular orientation. These structures evolve in complex manners during the processing of polymers into useful articles. Limitations of available and foreseeable computational capabilities prevent the direct determination of macroscopic properties directly from atomistic computations. As a result, computational tools and methods to bridge the length and time scale gaps between atomistic and continuum models are required. In this research, an internal state variable continuum model has been developed whose internal state variables (ISVs) and evolution equations are related to the nano-scale structures. Specifically, the ISVs represent entanglement number density, crystal number density, percent crystallinity, and crystalline and amorphous orientation distributions. Atomistic models and methods have been developed to investigate these structures, particularly the evolution of entanglements during thermo-mechanical deformations. A new method has been created to generate atomistic initial conformations of the polymer systems to be studied. The use of the hyperdynamics method to accelerate molecular dynamics simulations was found to not be able to investigate processes orders of magnitude slower that are typically measurable with traditional molecular dynamics simulations of polymer systems. Molecular dynamics simulations were performed on these polymer systems to determine the evolution of entanglements during uniaxial deformation at various strain rates, temperatures, and molecular weights. Two methods were evaluated. In the first method, the forces between bonded atoms along the backbone are used to qualitatively determine entanglement density. The second method utilizes rubber elasticity theory to quantitatively determine entanglement evolution. The results of the second method are used to gain a clearer understanding of the mechanisms involved to enhance the physical basis of the evolution equations in the continuum model and to derive the models material parameters. The end result is a continuum model that incorporates the atomistic structure and behavior of the polymer and accurately represents experimental evidence of mechanical behavior and the evolution of crystallinity and orientation. en_US
dc.description.degree Ph.D. en_US
dc.format.extent 7223089 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/10479
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Entanglements en_US
dc.subject Molecular dynamics
dc.subject Constitutive model
dc.subject Crystal
dc.subject Internal state variable
dc.subject Polymers
dc.subject.lcsh Nanostructured materials en_US
dc.subject.lcsh Molecular dynamics Computer simulation en_US
dc.subject.lcsh Deformations (Mechanics) en_US
dc.subject.lcsh Crystalline polymers Mechanical properties en_US
dc.title Multiscale Modeling of the Deformation of Semi-Crystalline Polymers en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor McDowell, David L.
local.contributor.advisor Jacob, Karl I.
local.contributor.corporatename George W. Woodruff School of Mechanical Engineering
local.contributor.corporatename College of Engineering
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