Identifier

etd-04052016-010115

Degree

Master of Science in Engineering Science (MSES)

Department

Engineering Science (Interdepartmental Program)

Document Type

Thesis

Abstract

As an important class of smart materials, thermal-induced shape memory polymers can store and release deformation energy on demand, in terms of recovery strain or recovery stress. Consequently, shape (strain) memory effect and stress memory effect can be identified. However, owning to some engineering and biomedical applications, stress memory effect sometimes can play an even more important role. In this work, stress memory effect is experimentally studied via two examples, namely, styrene-based bulky SMP by compression programming and polyurethane-based SMP fiber by stretch programming. Experimental results indicate that stress memory effect is closely related to programming temperature. In addition, “stress overshoot” and “temperature memory effect” are observed. We believed that at lower temperature the stress memory effect is primarily enthalpy driven, whereas at higher temperature it mainly driven by entropy, which provides a key clue for better understanding the origin of stress memory behavior programmed at different temperatures. We also proposed a multi-mechanism phase transition based phenomenological model, which includes shape memory effect, thermal expansion, mechanical relaxation and damage effect, to more accurately capture the recovery stress. In addition, a new concept of a fourth-order anisotropic stress memory effect tensor is introduced to help quantifying the general stress memory phenomena.

Date

2016

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Li, Guoqiang

Available for download on Friday, January 01, 9999

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