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Blomqvist, L., Berg, S. & Sandberg, D. (2019). Distortion in Laminated Veneer Products Exposed to Relative-Humidity Variations Experimental Studies and Finite-Element Modelling. BioResources, 14(2), 3768-79
Open this publication in new window or tab >>Distortion in Laminated Veneer Products Exposed to Relative-Humidity Variations Experimental Studies and Finite-Element Modelling
2019 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 2, p. 3768-79Article in journal (Refereed) Published
Abstract [en]

A shortcoming of the laminated bending process is that the product may become distorted after moulding. This study focused on the influence of fibre orientation deviation for individual veneers on the distortion of a moulded shell. The distortion of 90 cross-laminated shells of the same geometrical shape, consisting of seven peeled birch veneers, were studied under relative humidity variation. All the veneers were straight-grained in the longitudinal-tangential plane, but to simulate a deviation in fibre orientation, some of the individual veneers were oriented at an angle of 7 degrees relative to the main orientation of the other veneers in the laminate. A finite element model (FEM) was applied to study the possibility of predicting the results of a practical experiment. The study confirms the well-known fact that deviation in fibre orientation influences shape stability. The results also show how the placement of the abnormal veneer influences the degree of distortion. From this basic knowledge, some improvements in the industrial production were suggested. However, the FE model significantly underestimated the results, according to the empirical experiment, and it did not show full coherence. The survey shows the complexity of modelling the behaviour of laminated veneer products under changing climate conditions and that there is a great need to improve the material and process data to achieve accurate simulations. Examples of such parameters that may lead to distortion are density, annual ring orientation in the cross section of the veneer, the orientation of the loose and tight sides of the veneer, and parameters related to the design of the moulding tool.

Keywords
Birch; Cup; FEM; Veneer; Wood; Twist
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-39232 (URN)10.15376/biores.14.2.3768-3779 (DOI)
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Blomqvist, L., Sterley, M., Sandberg, D. & Johansson, J. (2015). The effect of veneer modification on the bond-line strength in laminated veneer products (ed.). Pro Ligno, 11(4), 43-49
Open this publication in new window or tab >>The effect of veneer modification on the bond-line strength in laminated veneer products
2015 (English)In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 43-49Article in journal (Refereed) Published
Abstract [en]

A major problem in the manufacture of three-dimensional laminated veneer products (LVP) is damage due to stretching and/or buckling of the veneer. To reduce or eliminate this problem, veneer densification or adding a strengthening layer to the veneer can be an alternative. To study how veneer modification influences the veneer-to-adhesive bond strength, three methods of modification were studied in relation to an unmodified reference veneer: (1) densified veneer, (2) veneer pre-bonded with paper and hot melt adhesive (HMA), (3) veneer pre-bonded with non-woven polypropylene (NW) fabric glued to the veneer (a) with a urea formaldehyde (UF) adhesive, (b) with a mixture of UF and polyvinyl acetate (PVAc) adhesive, and (c) with a PVAc adhesive. Densification, pre-bonding with paper, and NW with UF/PVAc adhesive mixture resulted in no or only a slight decrease in strength of the bond-line compared to the reference. NW glued with UF or PVAc adhesive showed a considerable reduction in the strength of the bond-line. The climatic cycling had no significant influence on the bond strength.

Keywords
densification, HMA, pre-bonding, PVAc, strengthening, THM processing, UF, wood
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-6920 (URN)30861 (Local ID)30861 (Archive number)30861 (OAI)
Available from: 2016-09-08 Created: 2016-09-08 Last updated: 2019-07-09Bibliographically approved
Blomqvist, L., Sterley, M., Sandberg, D. & Johansson, J. (2014). The influence of veneer modification on adhesive bond strength (ed.). In: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014).: . Paper presented at Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014). Edited by Peter Wilson. Edinburgh Napier University
Open this publication in new window or tab >>The influence of veneer modification on adhesive bond strength
2014 (English)In: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014)., Edinburgh Napier University , 2014, , p. 150-155Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Edinburgh Napier University, 2014. p. 150-155
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-12378 (URN)16701 (Local ID)16701 (Archive number)16701 (OAI)
Conference
Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE 2014). Edited by Peter Wilson
Available from: 2016-09-13 Created: 2016-09-13 Last updated: 2019-06-20Bibliographically approved
Blomqvist, L., Oscarsson, J. & Svensson, N. (2002). Säkerhet och organisation vid CNC-maskiner i träindustrin (ed.). Paper presented at .
Open this publication in new window or tab >>Säkerhet och organisation vid CNC-maskiner i träindustrin
2002 (Swedish)Report (Other academic)
Abstract [sv]

Denna rapport är en redovisning av projektet Säkerhet och organisation vid CNC-maskiner i träindustrin. Målsättningen med detta projekt har varit att utveckla, beskriva och sprida kunskap om arbetssätt, arbetsorganisation och kringutrustning vid arbete med träbearbetande CNC-maskiner. Sådant arbete är förknippat med stora risker, vilket bl a beror på maskinernas komplexitet, höga varvtal samt korta bearbetningstider i kombination med manuell hantering av arbetsstycken. Det sistnämnda innebär att en operatör ofta arbetar nära en maskins arbetsområde samtidigt som maskinen är i drift. Innehållet i denna rapport bygger på en inledande litteraturstudie, en inventering av olycksfall och incidenter samt fallstudier vid tre företag och en gymnasieskola.

Publisher
p. 53
Series
Rapport / Trätek., ISSN 1102-1071 ; 203012
National Category
Natural Sciences
Identifiers
urn:nbn:se:ri:diva-28564 (URN)
Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2019-06-20
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8644-4099

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