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The Effect of Geometry on the Mechanical Properties of Paper Fiber Bonds
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Optimizing the properties of paper products is an important task to reduce waste and increase efficiency in the paper and packaging industry. The mechanical properties of a sheet of paper stem from the strength of individual fibers as well as the strength of bonds between fibers in the fiber network. The fiber bond properties are sometimes the limiting factor in enhancing product strength. Gathering information about the properties of individual bonds experimentally is difficult, as it requires performing tedious and precise manipulations on the bond length scale.

In this work, we investigate the mechanical properties of fiber bonds as a function of their geometrical configuration and loading conditions, particularly how the stiffness of the bonded, collapsed and semi-collapsed fibers varies. The study is performed using a detailed finite element model of a fiber-fiber bond which comprises the essential characteristics of the fiber such as layered structure, chemical composition and fiber cross section geometry.

The results show that the response of the bond is a strong function of pressing conditions and is drastically affected by the closed lumen (inner surface of the fiber). The difference between using contact formulations bonded in both normal and tangential direction and contact formulations bonded only in the normal direction is small, indicating that introducing finite friction in the contact interface does not yield interesting results.

A comparison between the area that would appear bonded to an external observer and the area that is reported as in contact shows that the two differ by a factor of about 2 in the conducted simulations.

Among the geometrical properties the micro fibril angle is shown to have a negligible effect in the investigated range (11-21°). The effect of increasing the wall thickness increases the amount of pressure required to attain fiber collapse while increasing the fiber radius decreases it. This has important ramifications for the fiber to fiber bond stiffness as it is primarily driven by fiber collapse.

Place, publisher, year, edition, pages
2016. , 31 p.
National Category
Applied Mechanics
URN: urn:nbn:se:kth:diva-193556OAI: diva2:1034915
Subject / course
Solid Mechanics
Available from: 2016-10-13 Created: 2016-10-04 Last updated: 2016-10-13Bibliographically approved

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