Mechanics of amorphous polymers and polymer nanocomposites during high rate deformation

It has been suggested that a polymer's macroscopic mechanical response to a general loading case is governed by its ability to access various primary and secondary molecular mobilities. Specifically, under conditions of high strain rate, restricted secondary molecular motions are thought to bring about enhanced stiffness and strength. In accordance with this theory, an experimental protocol and associated analytical techniques were established to better understand the rate- and temperature-dependent mechanical behavior of two exemplary amorphous polymers, PC and PMMA. The experiments included dynamic mechanical thermal analysis (DMTA), as well as uniaxial compression tests over a wide range of strain rates. In both cases, the polymer exhibited a distinct transition in the rate-dependent yield behavior, under the same temperature/strain rate conditions as the observed viscoelastic 0-transition. Drawing off of previous research in the field of polymer mechanics, a new continuum-level constitutive model framework is proposed to account for the contributions of different molecular motions which become operational in different frequency/rate regimes. This model is shown to capture well the unique rate-dependent yield behavior of PC and PMMA, as well as the compressive stress-strain response under isothermal conditions.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Mechanical Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Mulliken, Adam Dustin, 1979-

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/1721.1/38265

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/38265