Abstract/Details

Yield and energy absorption in single and multi-phase glassy polymers subjected to multiaxial stress states: Theoretical and experimental studies


2004 2004

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Abstract (summary)

This thesis investigates the macroscopic yield behavior and microscopic energy absorption mechanisms in single and multiphase polymers. One unique aspect is the evaluation of polymers under multiaxial loading conditions. This is important because in many applications polymers are subjected to complex loading conditions and hence optimal design requires experimental evaluation and modeling of behavior under multiaxial stress states. This work has resulted in a more quantitative understanding of yield and energy absorption in the different polymers considered.

Multiaxial stress states are achieved using thin-walled hollow cylinder specimens. The hollow tubes are simultaneously subjected to internal pressure and axial load, leading to biaxial stress states. Stress states ranging from uniaxial compression to equibiaxial tension are interrogated using the same specimen geometry, a procedure uncovering true material behavior.

In the first part of this study, a generalized model for the yield behavior of single-phase polymers is evaluated for a polycarbonate system. The generalized model accounts not only accounts for viscoelasticity (i.e., rate and temperature dependence) but also the effect of pressure on yield behavior. The effects of physical aging on the behavior of amorphous polycarbonate are also highlighted.

For rubber-modified polymers, existing models for both macroscopic yield behavior and the onset of microscopic damage (e.g., cavitation) are evaluated under multiaxial conditions (chapter 3). Serious discrepancies are found for both cases, prompting an investigation into the nature of energy absorption mechanisms in the materials. Apart from the chosen rubber-modified systems, a toughening mechanism in the form of overlapping parallel cracks is identified to be generic to a range of polymers (chapter 4).

The last part of the thesis (chapter 5) involves a quantitative investigation of interactions in overlapping crack patterns. This effort is vital, because for better design of materials, the interaction has to be related to intrinsic material properties. The interactions in an infinite 2D array of parallel and overlapping cracks are analyzed using a complex stress function method. The size and number density of cracks in the array are related to intrinsic material properties and conditions for damage stability are identified.

Indexing (details)


Subject
Chemical engineering;
Polymers;
Materials science
Classification
0542: Chemical engineering
0495: Polymers
0794: Materials science
Identifier / keyword
Applied sciences; Pure sciences; Energy absorption; Glassy polymers; Multiaxial stress
Title
Yield and energy absorption in single and multi-phase glassy polymers subjected to multiaxial stress states: Theoretical and experimental studies
Author
Sankaranarayanan, Ramaswamy
Number of pages
120
Publication year
2004
Degree date
2004
School code
0118
Source
DAI-B 65/06, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
Advisor
Lesser, Alan J.
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3136776
ProQuest document ID
305177483
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305177483
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