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Elastic models coupling the cellulose nanofibril to the macroscopic film level
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
Paper and Fiber Research Institute (PFI AS), Trondheim, Norway.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
2015 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 5, no 71, 58091-58099 p.Article in journal (Refereed) Published
Abstract [en]

The mechanical behaviour of cellulose nanofibrils is typically characterized by casting thin films and performing tensile tests on strips cut from these films. When comparing the stiffness of different films, the stiffness of the nanofibrils is only qualitatively and indirectly compared. This study provides some schemes based on various models of fibre networks, or laminated films, which can be used to assess the inherent stiffness of the nanofibrils from the stiffness of the films. Films of cellulose nanofibrils from different raw materials were manufactured and the elastic properties were measured. The expressions relating the nanofibril stiffness and the film stiffness were compared for the presented models. A model based on classical laminate theory showed the best balance between simplicity and adequacy of the underlying assumptions among the presented models. Using this model, the contributing nanofibril stiffness was found to range from 20 to 27 GPa. The nanofibril stiffness was also calculated from mechanical properties of nanofibril films found in the literature and compared with measurements from independent test methods of nanofibril stiffness. All stiffness values were found to be comparable and within the same order of magnitude.

Place, publisher, year, edition, pages
2015. Vol. 5, no 71, 58091-58099 p.
National Category
Nano Technology
URN: urn:nbn:se:uu:diva-240247DOI: 10.1039/c5ra04016gISI: 000357805500100OAI: oai:DiVA.org:uu-240247DiVA: diva2:776073
Available from: 2015-01-06 Created: 2015-01-06 Last updated: 2015-12-18Bibliographically 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, Kristofer
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