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Mechanical Behavior of Non Cross-lin...

Sengab, Ahmed.

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Mechanical Behavior of Non Cross-linked Networks with Adhesion.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Mechanical Behavior of Non Cross-linked Networks with Adhesion./
Author:	Sengab, Ahmed.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
Description:	105 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-02, Section: B.
Contained By:	Dissertations Abstracts International81-02B.
Subject:	Mechanical engineering. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13856961
ISBN:	9781085559713

Mechanical Behavior of Non Cross-linked Networks with Adhesion.
Sengab, Ahmed.

Mechanical Behavior of Non Cross-linked Networks with Adhesion. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 105 p.

Source: Dissertations Abstracts International, Volume: 81-02, Section: B.

Thesis (Ph.D.)--Rensselaer Polytechnic Institute, 2019.

This item must not be sold to any third party vendors.

Adhesion plays an important role in the mechanics of nanoscale fibers such as various biological filaments, carbon nanotubes (CNTs) and artificial polymeric nanofibers. We study assemblies of non cross-linked CNTs and characterize their adhesion-driven structural evolution and their final stable structure. The key parameters of the problem are the network density, the fiber length, the bending stiffness of fibers, the inter-fiber friction and the strength of adhesion. The system of CNTs self-organizes in one of three types of structures: locked networks, in which CNTs remain in the asdeposited state, cellular networks, in which fibers form bundles and these organize into a larger scale network, and disintegrated networks, in which the network of bundles becomes disconnected. We determine the parametric space corresponding to each of these structures. The analysis provides design guidelines and a physical picture of the stability and structure of any random fiber network with adhesion. Further more we dry stretch buckypaper to form yarns of stochastic microstructure. We study the mechanical behavior of the resulting yarns, function of the CNT length and of the state of the CNT assembly before stretching. Large adhesive forces stabilize CNT bundles. Packing defects and pores of the initial structure of the buckypaper are incorporated in the yarn. The yarn is further tested in uniaxial tension. A parametric study is conducted to investigate the effect of the dry stretching procedure, and of the CNT length and deformation temperature on the flow stress of the resulting yarns. Since the mechanical behavior of the yarns is affected by the presence of defects which are incorporated in the yarn structure during production, a separate analysis is dedicated to the individual effect of such defects on the yarn flow stress. To this end, we identify three types of defects: filament waviness, strongly bent filaments denoted as hairpins, and filament length polydispersity. The analysis indicates that each of these defects influences the yarn flow stress through the way they modify filament packing. The thesis provides new physical insights into the structure and mechanics of fibrous materials stabilized by adhesive inter-fiber interactions and guidelines for engineering such networks for specific applications. In particular, it provides information that may assist the production of high strength carbon nanotube yarns of high strength for structural applications.

ISBN: 9781085559713Subjects--Topical Terms:

649730
Mechanical engineering.
Subjects--Index Terms:

Adhesion

Mechanical Behavior of Non Cross-linked Networks with Adhesion.
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520 $a Adhesion plays an important role in the mechanics of nanoscale fibers such as various biological filaments, carbon nanotubes (CNTs) and artificial polymeric nanofibers. We study assemblies of non cross-linked CNTs and characterize their adhesion-driven structural evolution and their final stable structure. The key parameters of the problem are the network density, the fiber length, the bending stiffness of fibers, the inter-fiber friction and the strength of adhesion. The system of CNTs self-organizes in one of three types of structures: locked networks, in which CNTs remain in the asdeposited state, cellular networks, in which fibers form bundles and these organize into a larger scale network, and disintegrated networks, in which the network of bundles becomes disconnected. We determine the parametric space corresponding to each of these structures. The analysis provides design guidelines and a physical picture of the stability and structure of any random fiber network with adhesion. Further more we dry stretch buckypaper to form yarns of stochastic microstructure. We study the mechanical behavior of the resulting yarns, function of the CNT length and of the state of the CNT assembly before stretching. Large adhesive forces stabilize CNT bundles. Packing defects and pores of the initial structure of the buckypaper are incorporated in the yarn. The yarn is further tested in uniaxial tension. A parametric study is conducted to investigate the effect of the dry stretching procedure, and of the CNT length and deformation temperature on the flow stress of the resulting yarns. Since the mechanical behavior of the yarns is affected by the presence of defects which are incorporated in the yarn structure during production, a separate analysis is dedicated to the individual effect of such defects on the yarn flow stress. To this end, we identify three types of defects: filament waviness, strongly bent filaments denoted as hairpins, and filament length polydispersity. The analysis indicates that each of these defects influences the yarn flow stress through the way they modify filament packing. The thesis provides new physical insights into the structure and mechanics of fibrous materials stabilized by adhesive inter-fiber interactions and guidelines for engineering such networks for specific applications. In particular, it provides information that may assist the production of high strength carbon nanotube yarns of high strength for structural applications.
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