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Effect of fiber and bond strength variations on the tensile stiffness and strength of fiber networks
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2016 (English)Report (Refereed)
Abstract [en]

As fiber and bond characterization tools become more sophisticated, the information from the fiber scale becomes richer. This information is used for benchmarking of different types of fibers by the paper and packaging industries. In this work, we have addressed a question about the effect of variability in the fiber and fiber bond properties on the average stiffness and strength of fiber networks. We used a fiber-scale numerical model and reconstruction algorithm to address this question. The approach was verified using the experimental sheets having fiber data acquired by a fiber morphology analyzer and corrected by microtomographic analysis of fibers in these sheets. We concluded, among other things, that it is sufficient to account for the average bond strength value with an acceptable number of samples to describe dry network strength, as long as the bond strength distribution remains symmetric. We also found that using the length-weighted average for fiber shape factor and fiber length data neglects the important contribution from the distribution in these properties on the mechanical properties of the sheets.

Place, publisher, year, edition, pages
2016. , 25 p.
Keyword [en]
fibers, bonds, stress-strain curve, paper strength, network simulation
National Category
Paper, Pulp and Fiber Technology
Identifiers
URN: urn:nbn:se:kth:diva-188480OAI: oai:DiVA.org:kth-188480DiVA: diva2:935135
Note

QC 20160613

Available from: 2016-06-10 Created: 2016-06-10 Last updated: 2016-06-13Bibliographically approved
In thesis
1. Micromechanics of Fiber Networks
Open this publication in new window or tab >>Micromechanics of Fiber Networks
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The current trends in papermaking involve, but are not limited to, maintaining the dry strength of paper material at a reduced cost. Since any small changes in the process affect several factors at once, it is difficult to relate the exact impact of these changes promptly. Hence, the detailed models of the network level of a dry sheet have to be studied extensively in order to attain the infinitesimal changes in the final product.

In Paper A, we have investigated a relation between micromechanical processes and the stress–strain curve of a dry fiber network during tensile loading. The impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds, is discussed. In Paper B, we studied the impact of the chemical composition of the fiber cell wall, as well as its geometrical properties, on the fiber mechanical properties using the three-dimensional model of a fiber with helical orientation of microfibrils at a range of different microfibril angles (MFA). In order to accurately characterize the fiber and bond properties inside the network, via statistical distributions, microtomography studies on the handsheets have been carried out. This work is divided into two parts: Paper C, which describes the methods of data acquisition and Paper D, where we discuss the extracted data. Here, all measurements were performed at a fiber level, providing data on the fiber width distribution, width-to-height ratio of isotropically oriented fibers and contact density. In the last paper, we utilize data thus obtained in conjunction with fiber morphology data from Papers C and D to update the network generation algorithm in order to produce more realistic fiber networks. We also successfully verified the models with the help of experimental results from dry sheets tested under uniaxial tensile tests. We carry out numerical simulations on these networks to ascertain the influence of fiber and bond parameters on the network strength properties.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 32 p.
Series
TRITA-HFL. Report / Royal Institute of Technology, Solid Mechanics, ISSN 1654-1472 ; 97
Keyword
Network simulation, Mechanical properties, Fibers, Fiber-to-fiber bonds, Free fiber length, Number of contacts, Contact density, Paper properties, X-ray microtomography
National Category
Paper, Pulp and Fiber Technology
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:kth:diva-188481 (URN)978-91-7595-994-8 (ISBN)
Public defence
2016-09-02, Kollegiesalen, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160613

Available from: 2016-06-13 Created: 2016-06-10 Last updated: 2016-06-13Bibliographically approved

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Borodulina, SvetlanaMotamedian, Hamid RezaKulachenko, Artem
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