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Experimental investigation of damage at folding of coated papers
KTH, Superseded Departments, Solid Mechanics.
KTH, Superseded Departments, Solid Mechanics.ORCID iD: 0000-0001-6232-8819
KTH, Superseded Departments, Solid Mechanics.ORCID iD: 0000-0001-8699-7910
2002 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 17, no 1, 34-38 p.Article in journal (Refereed) Published
Abstract [en]

An experimental investigation of damage occuring at folding of coated paper has been performed. For this purpose an experimental device was constructed in such a way that close resemblance with an industrial situation was achieved. During the experiments the influence on the damage levels in the coating from such features as delamination, humidity and paper thickness have been studied using an optical microscope. The behaviour of two different paper materials has been investigated. A stress (or strain) based fracture criterion is relevant for the present problem but biaxiality of stresses as well as in-plane anisotropy must be taken into account. It was observed that cracking of the coating would not lead to subsequent cracking of the paper substrate and that delamination occurred during folding, in the base stock and not at the paper/coating interface, but its quantitative influence as regards cracking could not be determined. The influence from sheet grammage was investigated and it was found that the only case when (visible) cracks did not appear was at low values. High humidity did not affect the cracking.

Place, publisher, year, edition, pages
2002. Vol. 17, no 1, 34-38 p.
Keyword [en]
coated paper, folding, delamination, cracking, moisture content
National Category
Materials Engineering
URN: urn:nbn:se:kth:diva-5324ISI: 000174750900006OAI: diva2:8514
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2011-08-26Bibliographically approved
In thesis
1. On folding of coated papers
Open this publication in new window or tab >>On folding of coated papers
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The mechanical behaviour of coated papers during folding has been investigated. This problem has been studied with experimental techniques and numerical analyses in order to give a better understanding of the folding properties of coated papers pertinent to the mechanical behaviour in general, and particularly cracking along the fold.

A microscopy investigation has been performed. The surface of the folded paper has been carefully examined to study the event of fracture and related issues. The influence of the grammage on the cracking event has been studied and it was shown that the coating material would not fail if the paper sample was sufficiently thin. It was found that a stress or strain based criterion is sufficient to describe the cracking of the coating layers and that the anisotropy of paper should be taken into account when studying the folding process.

The finite element method has been used for the numerical analyses remembering that the geometry of the problem is rather complicated, excluding a solution in analytical form. Using different constitutive models for the base stock, it has been shown that the deformation of the coated paper during folding is much governed by the paper substrate. The numerical results also suggested that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. Furthermore, it has also been shown that delamination buckling, in the present circumstances, has a very small influence on the strain levels in the coating layer subjected to high tensile loading.

Dynamic effects have also been studied and it has been shown that a quasi-static analysis of the problem is sufficient in order to describe many of the important features related to cracking. An attempt to model strong anisotropy of paper has been presented and the results indicate that the large anisotropy in the thickness direction of coated papers needs to be taken into account in order to fully understand the mechanics of folding.

Finally, an experimental investigation has been presented in order to study if important mechanical properties of the coating material could be determined by microindentation techniques. The results presented indicate that microindentation can be a powerful tool for characterization of these materials, but only if careful efforts are made in order to account for the influence from plasticity as well as from boundary effects.

KEYWORDS: folding, coated papers, finite element method, cracking, indentation, anisotropy, plasticity.

Place, publisher, year, edition, pages
Stockholm: Hållfasthetslära, 2004
Trita-HFL, ISSN 1104-6813 ; 0307
Materials science, folding, coated papers, finite element method, cracking, indentation, Materialvetenskap
National Category
Materials Engineering
urn:nbn:se:kth:diva-28 (URN)
Public defence
2004-10-01, STFI-salen, STIFI, Drottning Kristina väg 61, Stockholm, 10:00
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2012-03-19Bibliographically approved

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Barbier, ChristopheLarsson, Per-LennartÖstlund, Sören
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