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Tensile Deformation of Polymer Glasses: Crazing, the Brittle-Ductile Transition and Elastic Yielding

Cheng, Shiwang
http://rave.ohiolink.edu/etdc/view?acc_num=akron1382525654

Abstract Details

2013, Doctor of Philosophy, University of Akron, Polymer Science.
Polymer glasses are important engineering materials and undergo various mechanical instabilities in service such as crazing, brittle failure, shear yielding and necking. Although our understanding of these mechanical instabilities starts from 70 years ago, most of previous works borrow the treatment from solid mechanics. A molecular level understanding of these nonlinear mechanical behaviors is still missing and challenge. In this dissertation, we utilize the hybrid structure proposed recently to understand the various mechanical instabilities as well as the origin of the stress in the post-yield region. Different from previous treatments of emphasizing the inter-segmental contribution in stress, we are mainly focused ourselves on the role of chain network (intra-segmental contribution). Our experimental data shows intra-segmental contribution plays a deterministic role in the nonlinear region. Specifically speaking, the existence of chain network ensures the success of load transfer during deformation, which helps the glass to tolerate structural heterogeneities. A sufficient strong chain network could completely suppress crazing and necking, and it could also delay the brittle-ductile transition to toughen the material. On the other hand, we further elucidate the role of chain network by studying the nature of the stress in the post-yield region. Thermal shrinkage and elastic yielding phenomena of cold drawn polymer glasses are studied. Based on a systematic study of the phenomena, we conclude there is a portion of elastic stress (intra-segmental stress) in the post-yield stress and this elastic component comes from the distortion of covalent bonds in the chain backbone.
Shi-Qing Wang, Dr. (Advisor)
Mesfin Tsige, Dr. (Committee Member)
Stephen Z. D. Cheng, Dr. (Committee Member)
Gary R. Hamed, Dr. (Committee Member)
Robert A. Weiss, Dr. (Committee Member)
David Simmons, Dr. (Committee Member)
157 p.
Condensed Matter Physics; Polymers
Polymer glasses, crazing, the brittle-ductile transition, elastic yielding, creep, strain localization

Recommended Citations

Citations

  • Cheng, S. (2013). Tensile Deformation of Polymer Glasses: Crazing, the Brittle-Ductile Transition and Elastic Yielding [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1382525654

    APA Style (7th edition)

  • Cheng, Shiwang. Tensile Deformation of Polymer Glasses: Crazing, the Brittle-Ductile Transition and Elastic Yielding. 2013. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1382525654.

    MLA Style (8th edition)

  • Cheng, Shiwang. "Tensile Deformation of Polymer Glasses: Crazing, the Brittle-Ductile Transition and Elastic Yielding." Doctoral dissertation, University of Akron, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1382525654

    Chicago Manual of Style (17th edition)

akron1382525654
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© 2013, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.