lnu.sePublications
Change search
Refine search result
1 - 23 of 23
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Hosseinpourpia, Reza
    Georg-August-University Göttingen, Germany.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Tensile strength of handsheets prepared with macerated fibres from solid wood modified with cross-linking agents2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 8, p. 959-966Article in journal (Refereed)
    Abstract [en]

    This study was conducted to explain the tensile strength loss of wood due to the modification with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and glutaraldehyde (GA). Modified and control wood blocks were macerated to deliberate fibres, and handsheets were produced thereof. The nitrogen content of the fibres indicated that maceration removed the major proportions of DMDHEU. The stability of GA in wood during maceration was not assessed. Tensile strength determined at zero span (z-strength) and finite span (f-strength) was equal for the handsheets from DMDHEU-modified fibres and the control handsheets. The microscopic appearance of the tested finite-span paper strips from DMDHEU-modified fibres mainly indicated interfibre failure and did not differ from the fibre fracture mode of the control handsheets. In contrast, the z-strength of the handsheets from GA-modified fibres was lower than that of controls and decreased with increasing content of GA in the initial modified wood. The f-strength behaviour of the handsheets from GA-modified fibres was the opposite: it was higher than that of controls and increased with increasing GA content. The microscopic appearance of the rapture zones of the finite-span testing mainly indicated intrafibre failure for the GA-modified fibres. It was concluded that cross-linking is likely to be the major reason for tensile strength loss of GA- and DMDHEU-modified wood. In terms of DMDHEU-modified wood, the incrustation of the cell wall by the resin and the reduction in pliability could play an additional role.

  • 2.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 251-258Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 3.
    Amiandamhen, Stephen
    et al.
    Stellenbosch University, South Africa.
    Meincken, Martina
    Stellenbosch University, South Africa.
    Tyhoda, Luvuyo
    Stellenbosch University, South Africa.
    Calcium phosphate bonded wood and fiber composite panels: production and optimization of panel properties2017In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 71, no 9, p. 725-732Article in journal (Refereed)
    Abstract [en]

    The development of phosphate bonded composites with properties comparable with those of current Portland cement bonded products has been investigated. More precisely, the focus of the study was the optimization of calcium phosphate cements in combination with wood processing residues slash pine (Pinus elliottii Engelm.) planer shavings, Black wattle (Acacia mearnsii De Wild.) residues, Blue gum (Eucalyptus globulus Labill.) residues, hemp (Cannabis Sativa L.) hurds and dried crushed sugarcane bagasse (Saccharum officinarum L.) as well as pulp mill sludge and waste paper. A central composite design (CCD) for the response surface methodology (RSM) was applied for selection of the proper parameters. Mechanical tests were conducted on the composite products and the effect of the processing variables was evaluated based on the Pareto analysis of variance. The density of the wood-based panels ranged from 0.68 to 1.21 g cm−3, that of the agricultural fibers from 0.59 to 1.15 g cm−3 and that of the paper pulp panels from 0.81 to 1.21 g cm−3. The modulus of elasticity (MOE) data of the panels ranged from 1.63 to 4.92 MPa for wood, from 0.37 to 3.28 MPa for agricultural fibers and from 0.65 to 3.87 MPa for paper-pulp-based fibers. The physical properties of the composite products met the requirements for Portland-cement-bonded particleboards (EN 634-2, 2007).

  • 4.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Alfredsen, Gry
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Changes in microstructure and stiffness of Scots pine (Pinus sylvestris L) sapwood degraded by Gloeophyllum trabeum and Trametes versicolor Part II: Anisotropic stiffness properties2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 199-206Article in journal (Refereed)
    Abstract [en]

    Fungal decay considerably affects the macroscopic mechanical properties of wood as a result of modifications and degradations in its microscopic structure. While effects on mechanical properties related to the stem direction are fairly well understood, effects on radial and tangential directions (transverse properties) are less well investigated. In the present study, changes of longitudinal elastic moduli and stiffness data in all anatomical directions of Scots pine (Pinus sylvestris) sapwood which was degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks have been investigated. Transverse properties were found to be much more deteriorated than the longitudinal ones. This is because of the degradation of the polymer matrix between the cellulose microfibrils, which has a strong effect on transverse stiffness. Longitudinal stiffness, on the other hand, is mainly governed by cellulose microfibrils, which are more stable agains fungal decay. G. trabeum (more active in earlywood) strongly weakens radial stiffness, whereas T. versicolor (more active in latewood) strongly reduces tangential stiffness. The data in terms of radial and tangential stiffnesses, as well as the corresponding anisotropy ratios, seem to be suitable as durability indicators of wood and even allow conclusions to be made on the degradation mechanisms of fungi.

  • 5.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Alfredsen, Gry
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Microstructure and stiffness of Scots pine (Pinus sylvestris L) sapwood degraded by Gloeophyllum trabeum and Trametes versicolor Part I: Changes in chemical composition, density and equilibrium moisture content2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 191-198Article in journal (Refereed)
    Abstract [en]

    Fungal degradation alters the microstructure of wood and its physical and chemical properties are also changed. While these changes are well investigated as a function of mass loss, mass density loss and changes in equilibrium moisture content are not well elucidated. The physical and chemical alterations are crucial when linking microstructural characteristics with macroscopic mechanical properties. In the present article, a consistent set of physical, chemical and mechanical characteristics is presented, which were measured on the same sample before and after fungal degradation. In the first part of this two-part contribution, elucidating microstructure/stiffness-relationships of degraded wood, changes in physical and chemical data are presented, which were collected from specimens of Scots pine (Pinus sylvestris) sapwood degraded by Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) for up to 28 weeks degradation time. A comparison of mass loss with corresponding mass density loss demonstrated that mass loss entails two effects: firstly, a decrease in sample size (more pronounced for G. trabeum), and secondly, a decrease of mass density within the sample (more pronounced for T. versicolor). These two concurrent effects are interrelated with sample size and shape. Hemicelluloses and cellulose are degraded by G. trabeum, while T. versicolor was additionally able to degrade lignin. In particular because of the breakdown of hemicelluloses and paracrystalline parts of cellulose, the equilibrium moisture content of degraded samples is lower than that in the initial state.

  • 6.
    Bengtsson, Peter
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sanati, Mehri
    Evaluation of hydrocarbon emissions from heart- and sapwood of Scots pine using a laboratory-scale wood drier2004In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, no 6, p. 660-665Article in journal (Refereed)
    Abstract [en]

    The subject of study is the emission of Volatile Organic Compounds (VOC) during the drying of wood. Heart-wood and sapwood from Scots pine were dried at different temperatures (50, 70 and 90oC) in a laboratory kiln.The sampling method, Solid Phase Microextraction was used to collect the different volatile organic compounds during the drying. The gas chromatograph and mass spectrometer was used to identify and quantify the organic matter. The total hydrocarbons were measured with a flame ionization detector. Primarily, different monoterpenes were released during the drying process. 3-carene and a-pinene were most common and were also analytically quantified. The diterpene, pimaral, was found in an estimated large amount in the later stage of the drying process but was not exactly quantified. Large differences in both release behavior and total amount of released hydrocarbon between heart- and sapwood were obtained. Emissions of VOC from heartwood were of a magnitude approximately three times higher than that from sapwood

  • 7.
    Blom, Åsa
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bergström, Mikael
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Elowson, Torbjörn
    Durability of Untreated Norway Spruce (Picea abies) Exposed Outdoors Above Ground for Nine Years.2004In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 58, no 2, p. 167-172Article in journal (Refereed)
    Abstract [en]

    Moisture dynamics and durability during weather exposure as affected by origin and production method were studied for nine years on 113 untreated spruce samples. The moisture content was measured on 67 occasions. The weight loss was determined for each sample at the end of the sampling period. The most important factors, affecting both moisture content and weight loss, were origin and drying technique. The samples originating from central Sweden had the best durability, followed by the southern stand, while the northern stand had the lowest durability in terms of weight loss. Airdrying had a negative impact on the performance of samples from all three stands, but to different degrees. Samples from the northern stand were most sensitive to airdrying, in terms of both weight loss and moisture content, followed by the southern stand, while the central stand was least sensitive. Why the samples from the northern stand were more sensitive to airdrying and showed the largest weight losses is unknown; it can only be suggested that the origin of the wood can be of importance for the durability.

  • 8.
    Blom, Åsa
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Bergström, Mikael
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Elowson, Torbjörn
    Mass loss and moisture dynamics of Scots pine (Pinus sylvestris L.) exposed outdoors above ground in Sweden.2005In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 59, no 2, p. 183-189Article in journal (Refereed)
    Abstract [en]

    The durability of 566 Scots pine (Pinus sylvestris) samples was tested during a period of 9 years of exposure to weather in Sweden. The parameters investigated were heartwood/sapwood, origin, surface treatment, end-seal, storage and drying method, annual ring width and density. The weight was measured on 67 occasions during 9 years in order to assess the moisture content of the samples. The mass loss was determined for each sample at the end of the trial. Sapwood had a higher moisture uptake and a higher mass loss compared with heartwood. Even if sapwood was painted with an impermeable paint and then end-sealed, it still had higher average moisture content than heartwood. The results also demonstrated that sapwood was more sensitive to different handling conditions than heartwood. Sapwood was sensitive to air-drying and water storage, which was evident in the higher moisture uptake. In terms of mass loss, some differences were evident but they were not statistically significant due to the large standard deviation of the sapwood samples from water-stored logs. The only positive influence of water storage was on samples end-dipped in oil. One explanation could be that water storage led to increased permeability due to bacterial attack, which in turn enhanced the penetration of the oil. Heartwood had low and stable moisture dynamics during the test period, almost independent of treatment or handling conditions. No correlation with moisture uptake or mass loss was evident among annual ring width, origin or density.

  • 9.
    Bonarski, Jan T.
    et al.
    Polish Academy of Sciences, Poland.
    Kifetew, Girma
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olek, Wieslaw
    Poznań University of Life Sciences, Poland.
    Effects of cell wall ultrastructure on the transverseshrinkage anisotropy of Scots pine wood2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 4, p. 501-507Article in journal (Refereed)
    Abstract [en]

    A hypothesis for explaining the differential anisotropicshrinkage behavior of wood has been proposed,and it was based on the differences in the cell wall ultrastructure.The starting point of the consideration is thatwood shrinkage is governed by its chemical composition,ultrastructure, and gross anatomy. It is also well knownthat the transverse shrinkage anisotropy of earlywood(EW) is more pronounced than that of the latewood (LW).In the paper, the cell wall ultrastructure and shrinkageanisotropy has been related to each other, and to thispurpose, a set of crystallographic texture descriptorswas applied. The descriptors are based on X-ray diffraction(XRD) experiments conducted on matched EW samplesfrom different growth rings of Scots pine. The rangeof the microfibril angle (MFA) was identified. The ratio ofthe maxima of inverse pole figures (IPFs) of both the tangential(T) and radial (R) directions was determined. Theratios quantify the inhomogeneity of the spatial arrangementof the ordered areas. The results of the study clearlyindicate that the transverse shrinkage of wood is governedmostly by a specific ultrastructural organization of moderatelyorganized cell wall compounds.

    Download full text (pdf)
    fulltext
  • 10.
    Carlsson, Peter
    et al.
    Mid Sweden University.
    Esping, Björn
    Mid Sweden University.
    Dahlblom, Ola
    Lund University.
    Ormarsson, Sigurdur
    Lund University.
    Söderström, Ove
    Royal Institute of Technology.
    Optimization, a tool with which to create an effective drying schedule1998In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 52, no 5, p. 530-540Article in journal (Refereed)
    Abstract [en]

    A method for defining effective schedules for kiln drying of wood is presented. The method is designed in such a way that it proposes an optimized variation of temperature and humidity which yields the minimum total drying time , with the condition that the moisture content and the deformation not exceed specified limits after the drying and that the stress not exceeds a specified level at any time during the drying process in order to avoid crack development. To demonstrate the capability of the optimization method numerical results are presented. It should be noted that ill this first approach, drying starts from moisture content corresponding to the fibre-saturation point, i.e. approximate to 30%).

  • 11.
    Ghavidel, Amir
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Jorbandian, Amin
    University of Tehran, Iran.
    Bak, Miklós
    University of Sopron, Hungary.
    Gelbrich, Jana
    Leibniz-IWT, Germany.
    Morrell, Jeffrey J.
    University of the Sunshine Coast, Australia.
    Sandu, Ion
    Academy of Romanian Scientists (AOSR), Romania;Romanian Inventors Forum, Romania.
    Hosseinpourpia, Reza
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Linnaeus University, Linnaeus Knowledge Environments, Advanced Materials. Linnaeus University, Linnaeus Knowledge Environments, Green Sustainable Development. Michigan Technological University , USA.
    Degradation assessment of archaeological oak (Quercus spp.) buried under oxygen-limited condition2023In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 77, no 3, p. 198-207Article in journal (Refereed)
    Abstract [en]

    The biological deterioration of archaeological wood under oxygen-limited conditions varies due to the limited activities of microorganisms. It is essential to expand the knowledge of the degradation types and the status of archaeological monuments for selecting the proper consolidates. The physical, chemical, and anatomical properties of approximately 600–650 year old archaeological oak collected from an archaeological site in Iasi-Romania were analysed to assess the quality and to identify the degradation types. The results were compared with similar tests on recently-cut oak. X-ray photoelectron spectroscopy (XPS) revealed the presence of more lignin-related peaks in the archaeological oak, which likely reflected the degradation of the wood carbohydrates as evidenced by the decreased oxygen-to-carbon ratio Cox/Cnon-ox. The differences in cellulose crystallinity were not significant suggesting that any cellulose degradation occurred in the amorphous regions. This was also reflected in the dynamic water vapor sorption analysis where the differences in sorption isotherms and hysteresis of archaeological and recently-cut oaks were marginal. Microscopic analysis of the oak cells illustrated bacterial degradation patterns, while the field emission scanning electron microscopy (FESEM) showed the presence of erosion bacteria in the archaeological oak collected from the site with low oxygen conditions.

    Download full text (pdf)
    fulltext
  • 12.
    Hosseinpourpia, Reza
    et al.
    Georg-August-University Göttingen.
    Mai, Carsten
    Georg-August-University Göttingen.
    Mode of action of brown rot decay resistance in phenol-formaldehyde-modified wood: resistance to Fenton’s reagent2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 3, p. 253-259Article in journal (Refereed)
    Abstract [en]

    The mode of action of phenol-formaldehyde (PF)-modified wood has been investigated with respect to its resistance to brown rot decay. The Fenton reaction is assumed to play a key role in the initial brown rot decay. Pine microveneers were modified to various weight percent gains (WPG) with low molecular weight PF and exposed to a solution containing Fenton’s reagent. The mass loss (ML) and tensile strength loss (TSL) as well as the decomposition of hydrogen peroxide within the incubation time decreased with the increasing WPG of the veneers. Incubation of untreated and PF-modified veneers in acetate buffer containing ferric ions without H2O2 revealed that the modification strongly reduces the uptake of iron by the wood cell wall. Further studies indicated that lignin promotes the decay of wood by Fenton’s reagent. The reason for the enhanced resistance of modified wood to the Fenton reaction is attributable to the impeded diffusion of iron ions into the cell wall rather than to the blocking of free phenolic sites of lignin, which accelerate redox cycling of iron.

  • 13.
    Hosseinpourpia, Reza
    et al.
    Georg-August-University Göttingen, Germany.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Mode of action of brown rot decay resistance of thermally modified wood: resistance to Fenton’s reagent2016In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, no 7, p. 691-697Article in journal (Refereed)
    Abstract [en]

    The resistance of heat treated (HT) wood to brown rot fungi has been investigated, while the role of the Fenton reaction (FR) in the initial phase of degradation was in focus. Micro-veneers made of Scots pine, were HT with various intensities and their mass losses (MLHT) were determined before soaking with a solution of Fenton’s reagent containing Fe ions and hydrogen peroxide. The mass loss of the veneers treated that way (MLFT), their tensile strength loss (TSLFT) and the H2O2 decomposition were observed. The MLFT, TSLFT, and H2O2 loss decreased with increasing MLHT of the veneers. Soaking of the veneers in acetate buffer containing only Fe without H2O2 revealed that the heat treatment (HT) strongly reduces the Fe uptake by the cell walls. FTIR spectroscopy indicated oxidation of the unmodified control veneers but did not reveal predominant decay of cell wall components; the HT veneers were not changed at all due to FR. It was concluded that the reason for the enhanced resistance of HT wood to FR is attributable to hindered diffusion of Fe ions into the wood cell wall.

  • 14. Kifetew, G
    The influence of the geometrical distribution of cell-wall tissues on the transverse anisotropic dimensional changes of softwood1999In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 53, no 4, p. 347-349Article in journal (Refereed)
    Abstract [en]

    The influence of the geometrical distribution of cell-wall tissues on the transverse anisotropic dimensional changes of softwood has been studied using two isotropic models. A finite element model has been used to calculate the thermal expansion of two aluminium plates without and with holes in the two perpendicular directions. Moisture expansion measurements in the two perpendicular directions were conducted using a polyamide (PA6) plate containing several holes. No differences were found in either the thermal expansion of the aluminium plates or the moisture expansion of the PA6 plate between the two perpendicular directions. Thus, the investigation suggests that the geometrical distribution of cell-wall tissues has no effect on the transverse anisotropic shrinkage of softwood.

  • 15.
    Konnerth, Johannes
    et al.
    BOKU-University of Natural Resources and Applied Life Sciences, Austria.
    Eiser, Martina
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Jäger, Andreas
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Follrich, Jürgen
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Ters, Thomas
    BOKU-University of Natural Resources and Applied Life Sciences, Austria.
    Hansmann, Christian
    Competence Center for Wood Composites and Wood Chemistry, Austria.
    Wimmer, Rupert
    ood Technology and Wood-based Composites Unit, Germany.
    Macro- and micro-mechanical properties of red oak wood (Quercus rubra L.) treated with hemicellulases2010In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, no 4, p. 447-453Article in journal (Refereed)
    Abstract [en]

    Red oak wood (Quercus rubra L.) samples were submitted to an enzymatic treatment with a commercial mixture of hemicellulases aiming at the selective depolymerization and removal of the hemicelluloses. Mechanical properties of treated samples were characterized and compared with untreated samples at two hierarchical levels. At the macrolevel, tensile properties revealed to be less sensitive to degradation of the cell wall matrix compared to compression and hardness properties. Results obtained through indentation at the microlevel indicated that hardness and the so-called reduced modulus of treated wood were significantly lowered. Accordingly, hardness and reduced elastic modulus have proven to be most sensitive to modification of the cell wall matrix by reducing the content of hemicelluloses. It is proposed that transversal and shear stresses, which are mainly carried by the cell wall matrix, are additional parameters having strong effects on elastic modulus obtained by nanoindentation. Micromechanical modeling was employed to confirm the observed changes. There is consistency between the measured and the modeled properties, obtained at both the microlevel and the macrolevel of wood.

  • 16.
    Kumar, Anuj
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Czech Technical University in Prague, Czech Republic.
    Richter, Jan
    Czech Technical University in Prague, Czech Republic.
    Tywoniak, Jan
    Czech Technical University in Prague, Czech Republic.
    Hajek, Petr
    Czech Technical University in Prague, Czech Republic.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Šegedin, Urban
    University of Ljublijana, Slovenia.
    Marko, Petrič
    University of Ljublijana, Slovenia.
    Surface modification of Norway spruce wood by octadecyltrichlorosilane (OTS) nanosol by dipping and water vapour diffusion properties of the OTS-modified wood2018In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, no 1, p. 45-56Article in journal (Refereed)
    Abstract [en]

    The present research deals with a simple dipping method to insert octadecyltrichlorosilane (OTS) into cell walls of spruce wood and to deposit OTS layers on its inner and outer surfaces. Distribution and chemical interactions of OTS with wood polymers has been investigated by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The OTS/n-hexane solution penetrated into wood via capillary forces through ray tracheids and bordered pits and was deposited as OTS organic-inorganic layers on wood cell walls. The hypothesis is supported by the results, according to which the OTS molecules are hydrolysed by the wood moisture and by free OH groups of the cell wall components. The hydrolysed OTS molecules react with the OH groups and elevate the hydrophobicity of wood.

  • 17.
    Larsen, Finn
    et al.
    Technical University of Denmark, Denmark.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Experimental and finite element study of the effect of temperature and moisture on the tangential tensile strength and fracture behavior in timber logs2014In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 68, no 1, p. 133-140Article in journal (Refereed)
    Abstract [en]

    Timber is normally dried by kiln drying, in the course of which moisture-induced stresses and fractures can occur. Cracks occur primarily in the radial direction due to tangential tensile strength (TSt) that exceeds the strength of the material. The present article reports on experiments and numerical simulations by finite element modeling (FEM) concerning the TSt and fracture behavior of Norway spruce under various climatic conditions. Thin log disc specimens were studied to simplify the description of the moisture flow in the samples. The specimens designed for TS were acclimatized to a moisture content (MC) of 18% before TSt tests at 20°C, 60°C, and 90°C were carried out. The maximum stress results of the disc simulations by FEM were compared with the experimental strength results at the same temperature levels. There is a rather good agreement between the results of modeling and experiments. The results also illustrate the strong decrease of TSt with increasing temperature at a constant MC level.

  • 18.
    Mahnert, K-C
    et al.
    Georg August University of Göttingen, Germany.
    Adamopoulos, Stergios
    Georg August University of Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Koch, G
    Federal Research Institute of Rural Areas, Germany.
    Militz, H
    Georg August University of Göttingen, Germany.
    Topochemistry of heat-treated and N-methylol melamine modified wood of Koto (Pterygota macrocarpa K. Schum.) and Limba (Terminalia superba Engl. et Diels)2013In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 67, no 2, p. 137-146Article in journal (Refereed)
    Abstract [en]

    To broaden the knowledge about the chemical changes at the cell wall level of differently modified tropical hardwoods, heat-treated and N-methylol melamine (NMM)-treated samples of koto (Pterygota macrocarpa) and limba (Terminalia superba) were prepared. UV microspectrophotometry (UMSP) was applied at 278 and 240 nm as specific wavelengths to analyze chemical alterations of the samples caused by heat and NMM treatment, respectively. The absorbance of koto exceeded that of limba before and after treatment, potentially due to the higher extractive content of the former. Regardless of the wood species, the absorbance of the samples increased with increasing intensity of the NMM treatment. Additionally, the absorbance of lignin within the spectrum of 230–350 nm was altered due to the NMM treatment. The functionality of applying specific wavelengths for the analysis of different modification methods of wood was proven. However, the comparison with literature did not show differences in the absorbance, which could be assigned to the characteristics of tropical hardwoods.

  • 19.
    Pearson, Hamish
    et al.
    New Zealand Forest Research Institute (Scion), New Zealand.
    Gabbitas, Brian
    University of Waikato, New Zealand.
    Ormarsson, Sigurdur
    DTU -Technical University of Denmark, Denmark .
    Tensile behaviour of radiata pine with different moisture contents at elevated temperatures2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 5, p. 659-665Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to obtain tensile elastic modulus (EM) information for radiata pine (Pinus radiata D. Don) sapwood in tangential grain direction, over a temperature range of 70 °C to 150 °C for a wide range of moisture contents. Such information is scarce, probably because of difficulties with research equipment design and process control strategies to perform accurate tests. As expected, EM dramatically decreased with increasing temperature and moisture content. The results were modelled to yield a relationship between stress and strain. The results were also successfully transposed into a mastercurve based on temperature-moisture equivalence through a modified form of the Williams, Landel, and Ferry equation for amorphous polymers. This result is consistent with the view that wood is visco-plastic around the glass transition zone of the ligno-hemicellulosic matrix. It is demonstrated that moisture and temperature can play a significant role in reducing stress during drying, regardless of the drying time. Properties of wood, such as tensile elastic information at elevated temperatures, are important for mechanical design, distortion modelling and understanding the fundamental behaviour of wood in general.

  • 20.
    Pearson, Hamish
    et al.
    New Zealand Forest Research Institute (Scion), New Zealand.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Gabbitas, Brian
    University of Waikato, New Zealand.
    Nonlinear tensile creep behavior of radiata pineat elevated temperatures and different moisturecontents2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 7, p. 915-923Article in journal (Refereed)
    Abstract [en]

    Tensile wood creep has not been measured previouslyin the temperature region 135°C – 150°C for a rangeof moisture content (MC) up to fiber saturation point dueto equipment and measurement challenges. Yet this is theregion where the most dramatic softening effects can beobserved. The aim of this study was to develop specializedequipment to measure tensile solid wood creep over70°C – 150° C for a range of MC and loads. Creep displacementwas successfully able to be isolated from elasticand mechanosorptive strains and statistically modeledby regression analysis. This proved more accurate thancomplex series expansions consisting of spring- and dashpot-type components. The best creep displacement relationshipwas a power law with a strain root mean squareerror of 0.28%. The amplitude of the power law was nonlinearwith respect to stress and temperature and changedby a stress factor of up to 0.9 for a stress of up to 1.2 MPaand by a temperature factor 1.2 – 6.3 over the investigatedrange. The creep relationship provides a valuable tool forpredicting time-dependent distortion and internal stressof wood during drying or thermohygromechanical modificationbelow 150°C.

  • 21.
    Sandberg, Dick
    Kungliga Tekniska högskolan (KTH).
    Weathering of Radial and Tangential Wood Surfaces of Pine and Spruce.1999In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 53, no 4, p. 355-364Article in journal (Refereed)
    Abstract [en]

    The development of cracks and changes in appearance have been investigated on radial and tangential surfaces of pine (Pinus silvestris L.) and spruce (Picea abies Karst.) which have been exposed outdoors for 33 months. The degradation of the surfaces has also been studied at the micro-level. Untreated samples, samples impregnated with a CCA-agent and samples surface treated with linseed oil have been tested. The annual ring orientation is the most important factor for crack development on weathering. The type of wood, impregnation treatment and surface treatment with linseed oil have only a marginal effect on the crack development. No relation has been found between the density of the samples and the crack development After 33 months of outdoor exposure, tangential surfaces of pine have 13 times more total crack length per unit area than the corresponding radial surfaces. In spruce, the total crack length on the tangential surfaces is 6 times greater than on the radial surfaces. Tangential surfaces of both pine and spruce have a greater number of cracks per unit area and wider cracks than the corresponding radial surfaces. Tangential and radial surfaces show the same colour change in the surface as a result of weathering. On the micro-level, tangential surfaces have more and deeper cracks than radial surfaces. The cracks on the tangential surfaces occur frequently in both earlywood and latewood. On radial surfaces, cracks occur primarily at the annual ring borders, but to a certain extent also in the earlywood. The radial cell wall of the earlywood has a large number of pits which are degraded at an early stage. Decomposition of the cell wall takes place on both radial and tangential surfaces. Cracks arise which follow the S2 fibril orientation in the cell-wall. Delamination in the middle lamella is especially noticeable in the latewood on tangential surfaces. No differences have been observed regarding linseed oil treatment, impregnation or type of wood.

    Download full text (pdf)
    fulltext
  • 22.
    Sjödin, Johan
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    An experimental study of the effects of moisture variations and gradients in the joint area in steel-timber dowel joints2008In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 62, no 2, p. 243-247Article in journal (Refereed)
    Abstract [en]

    This experimental study examines the influence of moisture variations on the load-bearing capacity of steeltimber dowel joints. The glulam specimens used to manufacture the joints were first exposed to controlled climate changes. After being stored in the climate chambers, holes were drilled and dowels were inserted. Then, the joints were loaded to failure. The main aim of this study was to investigate how and to what extent moisture variations and gradients in the joint area affects the load-bearing capacity in tension parallel to the grain. The load-bearing capacity was found to be reduced under these conditions when compared to reference joints. Moreover, the brittleness of the joints increased with the time the joints had been exposed to drying. Moistureinduced stresses and cracks in the joint area were found to be a possible explanation of the results. A similar interpretation was given in other studies where other structural timber elements have been studied. This raises an important question of how such moisture effects should be considered in design codes. One possibility is to include the influence of moisture-induced stresses in the k_mod factor used in Eurocode 5. Another way could be to consider this type of moisture effect as an equivalent mechanical load case.

  • 23.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    A combined view on composition, molecular structure, and micromechanics of fungal degraded softwood2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 4, p. 471-482Article in journal (Refereed)
    Abstract [en]

    Fungal decay alters the composition, microstructure, and mechanical properties of wood cell walls. To understand better the structure-function relationships during fungal decay, selected annual rings of fungal deteriorated Scots pine sapwood were analyzed in terms of their composition, microstructure, and micromechanical properties. The datasets were acquired separately for earlywood and latewood concerning the S2 cell wall layer and the cell corner middle lamella (CCML) and analyzed by means of principal component analysis and partial least squares regression analysis. Links between cell wall stiffness and hardness and the composition and microstructure could be established. Increased mechanical properties in the CCML, as obtained by nanoindentation, were correlated to the degradation of pectins. In the S2 layer, the altered data were related to the degradation of hemicelluloses and lignin modification during fungal decay.

1 - 23 of 23
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf