Atomistic simulations of elastic-plastic deformation of amorphous polymers

As the demand for polymers with superior properties increases, an understanding of the fundamental connections between the mechanical behavior and underlying chemical structure becomes imperative. In this work, the thermo-mechanical behavior and the molecular-level origins of plastic deformation of an amorphous glassy polymer were studied using atomistic simulations. Understanding of the molecular response will aid the development of physics-based continuum level models for these materials. A polyethylene-like molecular network was numerically constructed using a Monte Carlo algorithm and then subjected to uniaxial deformation over a wide range of strain rates and temperatures using Molecular Dynamics. The model exhibits many experimentally observed characteristics such as an initial elastic response followed by yield then volume preserving plastic deformation. The stress response was decomposed into intra and inter molecular components and analyzed throughout deformation. In the glassy regime, activation parameters were calculated in the context of the Eyring Model of flow in a solid. In addition, observations were made of the evolution of chain configuration and the correlation of transitions between dihedral angle states. Below the glass transition, dynamic heterogeneity is observed. It was also observed that mobility, as measured by the transitioning between dihedral angle states, increases during plastic deformation to levels observed at much higher temperatures under zero stress. At temperatures near the glass transition temperature, the mobility approaches levels of undeformed samples at the glass transition temperature.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Mechanical Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Capaldi, Franco Mario, 1977-

Advisor dc:contributor.advisor

• Mary C. Boyce.

• Mechanical Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/8921

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/8921