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Prediction of elastic properties of nanofibrillated cellulose from micromechanical modeling and nano-structure characterization by transmission electron microscopy
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
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2013 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 20, no 2, 761-770 p.Article in journal (Refereed) Published
Abstract [en]

Cellulose-based materials have a great potential in terms of mechanical performance, since crystalline cellulose is known to have excellent stiffness along the main axis. This potential is not completely fulfilled in structural wood materials and in composite materials, due to structural inhomogeneities, misalignment, voids etc. on several length scales. This study investigates the difference in stiffness of nanofibrillated cellulose (NFC) compared to that of cellulose crystallites, based on nanostructural characterization, image analysis and micromechanical modeling. Nanofibrillated cellulose is believed to be composed of a distribution of crystallites in an amorphous matrix, and it is assumed to represent the distribution of the crystalline allomorph I-beta. To predict the elastic properties of NFC, a micromechanical model based on a Mori-Tanaka approach and self-consistent scheme was used. The input data, i.e. orientation distribution, aspect ratio and volume fraction of these crystalline regions, were estimated from image analysis of transmission electron micrographs. The model predicts a ca. 56 % loss of stiffness of NFC compared to that of cellulose crystals along the main axis.

Place, publisher, year, edition, pages
2013. Vol. 20, no 2, 761-770 p.
Keyword [en]
Nanofibrillated cellulose, Elastic properties, Micromechanics, Modelling, Transmission electron microscopy
National Category
Natural Sciences Engineering and Technology
Research subject
Engineering science with specialization in Applied Mechanics
URN: urn:nbn:se:uu:diva-197625DOI: 10.1007/s10570-013-9868-8ISI: 000315480400017OAI: oai:DiVA.org:uu-197625DiVA: diva2:614043
Available from: 2013-04-03 Created: 2013-04-02 Last updated: 2015-03-09Bibliographically approved
In thesis
1. Elasticity of Cellulose Nanofibril Materials
Open this publication in new window or tab >>Elasticity of Cellulose Nanofibril Materials
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The demand for renewable load-carrying materials is increasing with increasing environmental awareness. Alternative sources for materials manufacturing and design have to be investigated in order to replace the non-biodegradable materials. The work presented in this thesis investigates structure-property relations of such renewable materials based on cellulose nanofibrils. Cellulose is the most abundant polymer on earth and exists in both ordered and disordered phases, where the ordered crystalline cellulose shows excellent mechanical properties. The celluloses nanofibril is composed of partly crystalline cellulose where the stiff crystal regions, or crystallites, are orientated in the axial direction of the fibrils. The cellulose nanofibrils have a high aspect ratio, i.e. length to diameter ratio, with a diameter of less than 100 nm and a length of some micrometres. In the presented work, different properties of the cellulose nanofibril were studied, e.g. elastic properties, structure, and its potential as a reinforcement constituent. The properties and behaviour of the fibrils were studied with respect to different length scales, from the internal structure of the cellulose nanofibril, based on molecular dynamic simulations, to the macroscopic properties of cellulose nanofibril based materials. Films and composite materials with in-plane randomly oriented fibrils were produced. Properties of the cellulose nanofibril based materials, such as stiffness, thickness variation, and fibril orientation distribution, were investigated, from which the effective elastic properties of the fibrils were determined. The studies showed that a typical softwood based cellulose nanofibril has an axial stiffness of around 65 GPa. The properties of the cellulose nanofibril based materials are highly affected by the dispersion and orientation of the fibrils. To use the full potential of the stiff fibrils, well dispersed and oriented fibrils are essential. The orientation distribution of fibrils in hydrogels subjected to a strain was therefore investigated. The study showed that the cellulose nanofibrils have high ability to align, where the alignment increased with increased applied strain.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 60 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1215
Cellulose nanofibrils, Elastic properties, Micromechanics, Composites
National Category
Engineering and Technology
Research subject
Engineering science with specialization in Applied Mechanics
urn:nbn:se:uu:diva-240250 (URN)978-91-554-9135-2 (ISBN)
Public defence
2015-02-13, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Available from: 2015-01-22 Created: 2015-01-06 Last updated: 2015-03-09

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Josefsson, GabriellaGamstedt, E. Kristofer
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