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On folding of coated papers
KTH, Superseded Departments, Solid Mechanics.
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.
Series
Trita-HFL, ISSN 1104-6813 ; 0307
Keyword [en]
Materials science, folding, coated papers, finite element method, cracking, indentation
Keyword [sv]
Materialvetenskap
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-28OAI: oai:DiVA.org:kth-28DiVA: diva2:8519
Public defence
2004-10-01, STFI-salen, STIFI, Drottning Kristina väg 61, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2012-03-19Bibliographically approved
List of papers
1. Experimental investigation of damage at folding of coated papers
Open this publication in new window or tab >>Experimental investigation of damage at folding of coated papers
2002 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, 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.

Keyword
coated paper, folding, delamination, cracking, moisture content
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5324 (URN)000174750900006 ()
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-04Bibliographically approved
2. Numerical investigation of folding of coated papers
Open this publication in new window or tab >>Numerical investigation of folding of coated papers
2005 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 67, no 4, 383-394 p.Article in journal (Refereed) Published
Abstract [en]

Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the numerical analysis, the basepaper is modelled as an anisotropic elastic-plastic material (both elastic and plastic anisotropy is accounted for) while the constitutive behaviour of the coating layers are approximated by classical (Mises) elastoplasticity. The numerical results suggest, among other things, that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. It is also shown that delamination buckling, in the present circumstances, will have a very small influence on the strain levels in the coating layer subjected to high tensile loading.

Keyword
Coated paper (A), Finite element analysis (FEA) (C), Layered structures (A), Mechanical properties (B), Plastic deformation (B)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5325 (URN)10.1016/j.compstruct.2004.01.024 (DOI)000227052800002 ()2-s2.0-10644264191 (Scopus ID)
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-04Bibliographically approved
3. On dynamic effects at folding of coated papers
Open this publication in new window or tab >>On dynamic effects at folding of coated papers
2005 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 67, no 4, 395-402 p.Article in journal (Refereed) Published
Abstract [en]

Folding of coated papers is examined numerically using the finite element method. The analysis is focused on the influence from dynamic effects on the folding process. In particular, the behaviour of field variables relevant for cracking of the coating layers are studied in some detail. The results presented indicate that dynamic effects are of little importance as regards maximum strain levels in the coating but will influence the stress and strain distributions. Accordingly, a quasi-static analysis of the problem will be sufficient in order to describe many of the important features related to cracking.

Keyword
layered structures (A), mechanical properties (B), plastic deformation (B), finite element analysis (FEA) (C), dynamic effects (C)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5326 (URN)10.1016/j.compstruct.2004.01.025 (DOI)000227052800003 ()2-s2.0-10644232866 (Scopus ID)
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2017-12-04Bibliographically approved
4. On the effect of high anisotropy at folding of coated papers
Open this publication in new window or tab >>On the effect of high anisotropy at folding of coated papers
2004 (English)Report (Refereed)
Publisher
28 p.
Series
Trita-HFL, ISSN 1104-6813 ; 0374
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5327 (URN)
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2011-11-23Bibliographically approved
5. On material characterization of paper coating materials by microindentation testing
Open this publication in new window or tab >>On material characterization of paper coating materials by microindentation testing
Show others...
2005 (English)In: Journal of Coatings Technology Research, ISSN 1547-0091, Vol. 2, no 6, 463-471 p.Article in journal (Refereed) Published
Abstract [en]

Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts arc, made to account for the influence from plasticity as well as from boundary effects.

Keyword
non-destructive testing, microindentation, mechanical properties, packaging, paper, FEM
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-5328 (URN)10.1007/BF02733889 (DOI)000228531900006 ()2-s2.0-18144400445 (Scopus ID)
Available from: 2004-10-01 Created: 2004-10-01 Last updated: 2011-08-26Bibliographically approved

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