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  • 301.
    Hochreiner, Georg
    et al.
    Vienna University of Technology, Austria.
    Schweigler, Michael
    Vienna University of Technology, Austria.
    Riedl, Christian
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Matrix Failure of Multi-Dowel Type Connections Engineering Modelling and Parameter Study2016Inngår i: Proceedings of the 2016 World Conference on Timber Engineering (WCTE), Vienna University of Technology, Austria , 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A simplified numerical engineering model for the design of the surrounding timber matrix of dowel groups, developed within the framework of a commercial structural analysis software, is presented herein. This model was applied to highlight and reflect various dowel arrangements in timber to steel connections from building practice subjected to arbitrary sets of internal forces against the background of both the real mechanical behavior and the present practice of design. A parameter study revealed the interdependence of stresses in the timber matrix and geometrical and mechanical properties of dowel groups.

  • 302.
    Hofstetter, Karin
    et al.
    Vienna University of Technology, Austria.
    Eitelberger, Johannes
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Computational Multiscale Approach to the Mechanical Behavior and Transport Behavior of Wood2009Inngår i: Computational Structural Engineering: Proceedings of the International Symposium on Computational Structural Engineering, held in Shanghai, China, June 22–24, 2009, Springer, 2009, s. 79-85Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Moisture considerably affects the macroscopic material behavior of wood. Since moisture takes effect on wood at various length scales, a computational multiscale approach is presented in this paper in order to explain and mathematically describe the macroscopic mechanical and transport behavior of wood. Such an approach allows for appropriate consideration of the underlying physical phenomena and for the suitable representation of the influence of microstructural characteristics of individual wood tissues on the macroscopic behavior. Continuum (poro-)micromechanics is applied as homogenization technique in order to link properties at different length scales. Building the model on universal constituents with tissue-independent properties and on universal building patterns, the only tissue-dependent input parameters are wood species, mass density, moisture content, and temperature. All these parameters are easily accessible, what renders the models powerful and easily applicable tools for practical timber engineering.

  • 303.
    Hofstetter, Karin
    et al.
    Vienna University of Technology, Austria.
    Hellmich, Christian
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    Poro-micromechanical Estimates for Elastic Limit States of Wood2008Inngår i: Eleventh East Asia-Pacific Conference on Structural Engineering and Construction, Taipei, Taiwan, 2008, s. 550-551Konferansepaper (Annet vitenskapelig)
  • 304. Hofstetter, Karin
    et al.
    Hellmich, Christian
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Relevance of Microstructural Failure Mechanismus for Macroscopic Elastic Limit States of Wood2008Konferansepaper (Annet vitenskapelig)
  • 305.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH.
    Diagrambilaga till Rapport KTH-Trä TRITA-TRÄ R-95-12.1995Rapport (Annet vitenskapelig)
  • 306.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH Träteknologi.
    Kvistars frekvens, form och beskaffenhet i trekantprofil av furu (Pinus silvestris L) och gran (Picea abies Karst).1995Rapport (Annet vitenskapelig)
    Abstract [en]

    Frequency and Character of Knots in Triangular Profiles of Pine (Pinus silvestris L) and Spruce (Picea abies Karst).

    by

    Hans

    Holmberg Dick Sandberg

    Abstract

    This report describes the structure and amount of knots in triangular profiles from StarSawing of pine (Pinus silvestris L) and spruce (Picea abies Karst). The yield of blanks is determined mainly with a defined knot structure and the fibre aberration around knots. In addition a minor investigation of the amount of pitch pockets has been carried out.

    The specimens comprise of butt logs from three different areas in Sweden. The specimens are taken from normal grown pine, and both normal and fast grown spruce.

    Large amounts of the knots found in triangular profiles from butt logs are unacceptable for further refinement. Thus, the knots have to be removed. When producing blanks free from knots there is a volume decrease of 8 and 21 percent in average for pine and spruce respectively, referring to the original volume. Further refinement including fibre aberration increases the volume loss by another 5 percent for pine and 6 percent for spruce. The length of the refined blanks varies between 2 and 500 centimetres for pine and between 2 and 400 centimetres for spruce.

    Measurement results are included in the report for calculating the volume yield of blanks free from knots, with or without fibre aberration. The distributions of lengths of blanks and corresponding volume yields are shown in different graphs.

  • 307.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH Träteknologi.
    Structure and Properties of Scandinavian Timber1997Rapport (Annet (populærvitenskap, debatt, mm))
  • 308.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för teknik, TEK.
    Transportprocesser i trä.: Permeabilitet.1997Rapport (Annet vitenskapelig)
  • 309.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH, Träteknologi.
    Utvärdering av en ny ströläggningsmetod för stjärnsågad trekantprofil.1995Rapport (Annet vitenskapelig)
    Abstract [sv]

    En ny typ av ströläggning för trekantprofiler har undersökts. Profilema har torkats i buntar om tre där man alltid har lagt de tangentiella sidoma inåtvända för att minska risken för sprickbiIdning.

    Trekantprofilema som undersökts hade sidomåttet 120 mm. Torken som använts var en kammartork som styrs med ett torkschemat anpassat för furu med tjockleken 100 mm. Slutfuktkvoten var avsedd att bli 18 % om man torkat 100 mm virke.

    Efter torkning har prover tagits i rot, mitt och topp för att mata fuktkvotsgradienten i virket. I samband med fuktkvotsmätningen har även densiteten för virket bestämts. Resultaten visar att furu erhåller en större fuktkvotsgradient an gran för det parti som undersökts. Medelfuktkvoten för furn var efter torkning 15,8 % medan gran erhöll en medelfuktkvot på 13,0 %. Fuktkvotsskillnaden mellan torraste och fuktigaste parti i tvärsnittet var för furu 6,4 % och för gran 2,1 %.

    I undersökningen jämfördes trekantprofilemas slutfuktkvot med avsseende på placering i grupperna och med avseende på densitet. Med ett 95 % konfidensintervall kan man inte säkerställa att det finns skillnad mellan de olika placeringama i gruppen. Det går vidare inte att finna några samband mellan densiteten för virket och dess slutfuktkvot.

    En undersökning av ungefär tio kubikmeter virke visar att cirka 15 % av de torkade trekantprofilerma hade lättare angrepp av mögelsvampar. Mindre an 5 % av det genomgångna virket hade angrepp av blånad. Tryckskador fran strön förekom på två tredjedelar av virket och dessa skador kan i många fall härledas till dåIig måttnoggrannhet på profilema.

  • 310.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH.
    Volym- och kvalitetsutbyte vid stjärnsågning.1996Rapport (Annet vitenskapelig)
    Abstract [en]

    Volume yield and quality of timber when using Star-sawing technique

    by

    Hans Holmberg and Dick Sandberg

    Abstract

    Volume yield and quality are investigated when starsawing logs of pine (Pinus silvestris L) and spruce (Picea abies Karst). Topdiameters of timber were for pine sorted in two classes 260-300 rnm and 300-340 mm. Spruce timber were sorted in one class with top diameters between 290 and 340 mm.

    The investigation shows a volume yield considerably higher for starsawing compared to conventional techniques. This investigation, carried out on a simple testplant, yields 68 %calculated from top volume of log. Volume yield calculated from a cone with top and root diameters is 56 %. With sideboards included these numbers will incerease with one percent. The triangular profiles is 47 % of the total volume and the rest 53 % are quarter sawn boards.

    The volume yield of spruce is about one percent higher than for pine. The difference is assumed to depend on more pronounced taper of the log in spruce, wich allows easier positioning of the log.

    Quality is determined with a method developed especially for quarter sawn timber.

     

  • 311.
    Holmberg, Hans
    et al.
    KTH.
    Sandberg, Dick
    KTH.
    Volymutbyte vid tillverkning av furulimfog från stjärnsågad trekantsprofil.1997Rapport (Annet vitenskapelig)
    Abstract [da]

    Volume yield in manufacturing gluelam board of Scots pine from star-sawn triangular profiles.

    by

    H.Holmberg

    D. Sandberg

    Abstract

    Triangular profiles from star-sawing have been used to produce knot free gluelam boards with radial surfaces and a length of 2.1 m. The volume yield has been evaluated in two different gluelam qualities. One was with finger joints and the other one without finger joints. The material used was 7.78 mtriangular profiles of pine. The quality and dimension was sawfallen. The manufacture of the profiles has been carried out in five steps:

    1. Removal of knots and defects.
    2. Finger jointing of cut pieces.
    3. Planing of triangular profiles.
    4. Clueing of triangular profiles into blocks.
    5. Splitting the blocks into gluelam boards and finishing the surface.

    The measurements comprises all steps except splitting and final finishing. These steps have been simulated theoretically.

    The total volume yield was 53.8 %. In the process three operations were found to be critical for the result. They are: removal of knots and defects, planing and splitting of blocks and finishing. These operations account for more than 93 % of the total loss during manufacturing.

    Removal of knots and defects resulted in 12,8 % loss of volume. 13 % of the manufactured blocks were without knots, defects and finger joints. The average length of the pieces after cutting was 0,41 m.

  • 312.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). University of Göttingen, Germany.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Holstein, Nonna
    University of Göttingen, Germany.
    Mai, Carsten
    University of Göttingen, Germany.
    Dynamic vapour sorption and water-related properties of thermally modified Scots pine (Pinus sylvestris L.) wood pre-treated with proton acid2017Inngår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 138, s. 161-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study investigates the effect of proton acid pre-treatment and subsequent thermal modification at relatively low temperatures (up to 180 °C) on wood with respect to dimensional stability and water vapour sorption properties. The effects are compared to those of solely thermally-modified wood at higher temperatures (up to 250 °C). Scots pine sapwood (P. sylvestris L.) was impregnated with a proton acid or demineralised water, and subsequently, thermally modified to various mass losses (ML). Acid pre-treatment and thermal modification improved the dimensional stability and reduced the equilibrium moisture content (EMC) until certain ML. Excess surface work (ESW) obtained from vapour sorption studies indicated that, at comparable ML, the acid pre-treatment reduced the available sorption sites as compared to sole thermal treatment. Samples pre-treated with acid also showed stronger decreasing courses of EMC- and ESW-ratios than sole thermally modified ones. This was attributed to degradation of amorphous wood polymers and a stiffer matrix due to cross-linking of the cell wall polymers as a consequence of acid pre-treatment. Electron spin resonance (ESR) analysis indicated that acid pre-treatment did not enhance the concentration of phenoxy radicals, whereas thermally modified wood showed a considerably higher concentration of phenoxy radicals, suggesting that high radical density cannot be used as an indicator for high matrix stiffness.

  • 313.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, C
    Georg-August-University Gottingen, Germany.
    Analysis of the vapour sorption behaviour of wood modified with thermosetting resins with Hailwood-Horrobin and Excess Surface Work models2018Inngår i: 29th International Conference on Wood Science and Technology, ICWST 2018: Implementation of Wood Science in Woodworking Sector - Proceedings / [ed] Spanic N.,Zupcic I., University of Zagreb , 2018, s. 87-92Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Wood modification is a well-known technology to enhance the dimensional stability of wood and the resistance to abiotic and biotic degradation. Impregnation modification of wood with thermosetting resins, such as melamine formaldehyde (MF) or phenol formaldehyde (PF), alters the material properties of wood through formation of a three-dimensional network within the cell wall. This work investigates the vapour sorption behaviour of Scots pine (Pinus sylvestris L.) micro-veneers modified with MF and PF resins by means of Hailwood-Horrobin (H-H) and excess surface work (ESW) models. The analysed sorption data indicated that the available sorption sites were increased in the modified samples compared to the unmodified controls due to an increase of the monolayer sorption. However, modification resulted in a considerable reduction of the multilayer sorption. This could be attributed to the formation of a rigid, three-dimensional corset within the cell wall formed by auto-polymerization reactions of resin monomers and oligomers, which is known to reduce the cell wall swell-ability upon water absorption.

  • 314.
    Hosseinpourpia, Reza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Dynamic vapour sorption of wood and holocellulose modified with thermosetting resins2016Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 1, s. 165-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Micro-veneers of wood and holocellulose (HC) were modified with the thermosetting resins phenol formaldehyde and melamine formaldehyde. The dynamic water vapour sorption of the modified and untreated veneers was studied in a dynamic vapour sorption apparatus to assess the effects of resin modification. The adsorption of wood and HC as well as the desorption of wood was little affected by the modification in the low relative humidity (RH) range but decreased in the RH range above 60–70 %. The desorption isotherm of HC, however, was increased in the RH range of 15–80 % due to modification. Resin modification gradually decreased the EMC ratio of wood and HC and also influenced the moisture increment, equilibrium time and sorption rate in RH range above 50–60 % RH for wood and above 70–80 % RH for HC. HC exhibited a clearly lower hysteresis than wood. Modification of wood slightly reduced hysteresis compared to untreated wood, but modification of HC clearly increased hysteresis about to the same extent as that of wood. This indicates that the stiffening effect of lignin and thermosetting resins reduces the flexibility of the HC matrix, which results in increased hysteresis.

  • 315.
    Hosseinpourpia, Reza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Dynamic water vapour sorption properties and dimensional stability of thermally and acid-treated Scots pine (Pinus sylvestris L.)2015Inngår i: 69th Forest Products Society (FPS) International Convention, June 10-12, Atlanta, GA, Forest Products Society , 2015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In order to accelerate the thermal modification process, Scots pine sapwood samples were subjected to two types of treatments. One group of samples was impregnated with water and exposed to 220oC and the second group was initially treated with low concentration of acids (1 mol l-1 AlCl3 and a mixture of 0.5 mol l-1 H2SO4 and 1 mol l-1 AlCl3), and then heated at different temperatures (180 and 120oC) to achieve comparable mass loss (ML) levels. The water vapour sorption isotherms of the thermally and acid-treated wood samples were determined using a dynamic vapour sorption (DVS) apparatus. Increasing the temperature in both thermally and acid-treated samples resulted in ML attributable to hemicelluloses degradation. As a result thereof, dimensional stability and reduction in the hygroscopicity of wood were observed. Acid-treated samples heated at lower temperature exhibited similar water sorption behaviour as water-treated samples subjected to considerably higher temperature. The sorption data were analysed using the Hailwood-Horrobin (H-H) and excess surface work (ESW) models. The data indicated that the monolayer and polylayer sorption were reduced by the acid and thermal treatments, but acid treatment reduced the monolyer sorption stronger than the thermal. The effect of thermal and acid treatments on the flexibility of the cell wall matrix could not be fully distinguished.

  • 316.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, Carsten
    Effect of lignin and hemicelluloses removal on dynamic water vapour sorption behavior of wood2017Inngår i: IUFRO Division 5 Conference, 12-14 June, 2017 - Vancouver, British Columbia: Final program, proceedings and abstracts, IUFRO Division 5 Conference , 2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Water-related properties of wood are strongly depended on the sorption behavior of its hygroscopic polymers such as cellulose, hemicelluloses and lignin. To assess the sorption performance of wood matrix in the absence of hemicelluloses and lignin, micro-veneers of Scots pine (Pinus sylvestris L.) were hydrolyzed with sulphuric acid and delignified with sodium chlorite and acetic acid, respectively. The dynamic water vapour sorption of the hydrolyzed, delignified and untreated veneers was studied in a dynamic vapour sorption (DVS) apparatus. The moisture adsorption of hydrolyzed veneers was decreased in the relative humidity (RH) range above 60-70 %. Delignified veneers, however, showed obviously higher moisture adsorption at RH above 70%, as compared to untreated controls. Hydrolyzed and untreated veneers exhibited a comparable hysteresis, while delignified veneers showed a considerably lower hysteresis in comparison to them. This explains that, despite the fact that the hydrophilic hemicelluloses influence the moisture sorption of wood, the expand-ability of the cell wall matrix is mainly controlled by lignin.

  • 317.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Georg-August-University, Germany.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, Carsten
    Georg-August-University, Germany.
    Effects of acid pre-treatments on the swelling and vapor sorption of thermally modified Scots pine (Pinus sylvestris L.) wood2018Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, nr 1, s. 331-345Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Scots pine sapwood samples were pre-treated with a Lewis acid (AlCl3) and a combination of Lewis and protonic acids (AlCl3 and H2SO4), and were subsequently exposed to respective temperatures of 180 °C and 120 °C for establishing a comparable mass loss with those impregnated with demineralized water and solely thermally modified at 220 °C. Water impregnated samples dried at 120 °C also served as controls. The swelling behavior of all wood samples was examined with respect to maximum swelling in water, anti-swelling efficiency (ASE), shrinkage, and dynamic water vapor sorption at relative humidity ranges of 0% to 95%. The thermal modification at 220 °C diminished swelling and moisture adsorption, and also reduced moisture increment and decrement compared with the unmodified control. However, it was less obvious than both acid pre-treated samples. Excess surface work and Hailwood-Horrobin results calculated from water vapor sorption studies demonstrated that, at comparable mass loss, the available sorption sites were reduced to a greater extent by Lewis acid and combination of Lewis and protonic acids pre-treatment than the sole thermal treatment. This was attributed to more pronounced degradation of polysaccharides, mainly hemicelluloses and amorphous parts of cellulose, and to cross-linking of cell wall polymers due to the acid pre-treatments.

  • 318.
    Hosseinpourpia, Reza
    et al.
    Georg August University Göttingen, Germany.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Mai, Carsten
    Georg August University Göttingen, Germany.
    Tensile strength of handsheets from recovered fibers treated with N-methylol melamine and 1,3-dimethylol-4,5-dihydroxyethyleneurea2015Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, nr 3, artikkel-id 41290Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The main objective of this study was to assess the effect of two amino resins, N-methylol melamine (NMM) and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), on the intrafiber and interfiber strengths and water absorption of two types of waste paper categories, office paper (OP), and old corrugated containers (OCCs). The tensile strength of individual fibers measured at zero span was reduced by increases in the resin concentrations. The dry tensile strengths of the recovered handsheets measured at a finite span were enhanced with increases in the weight percentage gain of the resins. The increasing of the resin concentration also significantly improved the intrabonding of the OP and OCCs in moist measuring conditions. The water absorption of the handsheets considerably decreased at the higher concentration of the thermosetting resins, especially with NMM. The results are promising for the use of NMM- and DMDHEU-treated recovered fibers as an alternative fiber resource for the production of laminated paper and also for the use of DMDHEU as a new N-methylol compound for laminated paper.

  • 319.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Georg-August-University, Germany.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Mai, Carsten
    Georg-August-University, Gemany.
    Hemmilä, Venla
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Effect of Bio-Based Additives on Physico-Mechanical Properties of Medium Density Fibreboards2017Inngår i: 28th International Conference on Wood Science and Technology (ICWST), Zagreb, Croatia, 7-8 December, 2017 / [ed] Ivica Zupcic; Vjekoslav Zivkovic; Josip Miklecic, University of Zagreb, Faculty of Forestry , 2017, s. 153-158Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dimensional stability of wood-based panels is generally improved with application of suitable additives. Most of these additives, such as paraffin wax, are petroleum-based and with relatively high cost, and therefore, it is desirable to develop low-cost and effective substitutes from renewable resources. This work studied the potential of using a renewable water-repellent additive, such as tall oil fatty acid, for lab-scale manufacturing of medium density fibreboards (MDF). Tall oil fatty acid (TOFA) was used at 1 and 3% w/w of urea formaldehyde (UF) resin. MDF panels with similar concentrations of paraffin wax (wax) and panels without adding a water-repellent agent were served as controls. It was assessed the dimensional stability of the panels in terms of thickness swelling and water uptake after 4 and 24h immersion in water, and their mechanical performance in terms of modulus of elasticity, modulus of rupture and internal bonding. Results showed no obvious differences in the strength behaviour of the panels by addition of water-repellent agents. Dimensional stability, however, considerably improved by addition of TOFA, but it was still inferior when compared to that provided by wax.   

  • 320.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Parsland, Charlotte
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Utilization of different tall oils for improving the water resistance of cellulosic fibers2019Inngår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 136, nr 13, artikkel-id 47303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was conducted to assess the effect of the pulping by-products crude tall oil (CTO), distilled tall oil (DTO), andtall oil fatty acid (TOFA) on dynamic water vapor sorption behavior, interfiber strength, and thermal stability of cellulosic paper-sheets.The results were compared against those obtained in cellulose papers treated with the conventional petroleum-derived hydrophobicagent hydrowax and in untreated ones. The tall oil treatments caused strong reduction in equilibrium moisture content of the paper-sheets during adsorption and desorption runs. The same trend was noticed for the hydrowax-treated papers, however, it was lesspronounced than the CTO-treated and DTO-treated samples in the relative humidity range of 75–95%. The sorption hysteresis was con-siderably decreased after the treatments. The ultimate dry-tensile strengths of the paper-sheets were significantly reduced by TOFA andhydrowax treatments, while CTO and DTO showed comparable strength as that of untreated control. The ultimate wet-strengths of thepaper-sheets were improved after the treatments. The thermal stability of the specimens was improved by the tall oil treatments, and thehydrowax-treated samples illustrated lower degradation temperature than the untreated control. The results are promising for the use oftall oils as alternative hydrophobic agents of cellulosicfiber-based products, such as wood panels and paper packaging.

  • 321.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Echart, Arantzazu Santamaria
    University of the Basque Country UPV/EHU, Spain.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Gabilondo, Nagore
    University of the Basque Country UPV/EHU, Spain.
    Eceiza, Arantxa
    University of the Basque Country UPV/EHU, Spain.
    Modification of Pea Starch and Dextrin Polymers with Isocyanate Functional Groups2018Inngår i: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 10, nr 9, artikkel-id 939Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pea starch and dextrin polymers were modified through the unequal reactivity of isocyanate groups in isophorone diisocyanate (IPDI) monomer. The presence of both urethane and isocyanate functionalities in starch and dextrin after modification were confirmed by Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (13C NMR). The degree of substitution (DS) was calculated using elemental analysis data and showed higher DS values in modified dextrin than modified starch. The onsets of thermal degradation and temperatures at maximum mass losses were improved after modification of both starch and dextrin polymers compared to unmodified ones. Glass transition temperatures (Tg) of modified starch and dextrin were lower than unmodified control ones, and this was more pronounced in modified dextrin at a high molar ratio. Dynamic water vapor sorption of starch and dextrin polymers indicated a slight reduction in moisture sorption of modified starch, but considerably lower moisture sorption in modified dextrin as compared to that of unmodified ones.

  • 322.
    Hosseinpourpia, Reza
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Göttingen university, Germany.
    Mai, Carsten
    Dynamic water vapour sorption properties of wood cell wall polymer constituents2015Inngår i: COST FP1303 (Performance of bio-based building materials) / [ed] Dennis Jones, Christian Brischke, Jaan Kers, Triinu Poltimäe and Joachim Schmid, SP Technical Research Institute of Sweden , 2015, s. 42-44Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Lignin, cellulose and hemicelluloses have main roles on swelling and shrinkage of wood products. Interaction of these components with moisture has an important effect on market-friendly when the wood is subjected to the outside utilizations. In the heterogeneous structure of wood, sorption and desorption are occurred in different stages and it calls hysteresis. Hysteresis is a characteristic result from a moisture/temperature/time-dependent, slow, non-equilibrium, swelling-related conformational change, which is facilitated by increasing free volume and mobility in a polymer that is being plasticized during sorption that usually progresses through the stage of water clustering (Reina et al. 2001). Cell wall polymers of wood have a different behavior in the face of moisture in terms of sorption, desorption and hysteresis (Engelund et al. 2013).

    In order to better comprehension of the effect of cell wall material such as lignin, cellulose and hemicelluloses, Scots pine micro-veneers were subjected to hydrolysis with sulphuric acid or delignification with acidic sodium chlorite, as previously described (Klüppel and Mai 2012). Then the hemicelluloses were isolated from the delignified veneers according to the chloride method. The commercial lignin was also used after dialysis tubing. The water adsorption and desorption mechanism of delignified and hydrolysed veneers as well as cell wall polymers such as cellulose, hemicelluloses and lignin were determined using a dynamic vapour sorption (DVS) apparatus.

    The hydrolysed veneers were resulted in obviously lower moisture content in adsorption and desorption processes with increasing the relative humidity (RH) (Fig. 1a). While, delignified veneers showed slightly higher moisture content compared to control with increasing the ambient moisture until 70% RH and then considerably higher until 95% RH. Control specimens shown higher hysteresis than hydrolysed veneers and also higher hysteresis than delignified veneers after hygroscopic range (Fig. 1b). Moisture content of cell wall constituents in various relative humidity exhibited the higher moisture sorption and desorption of cellulose than lignin, however, hemicelluloses illustrated the significantly higher moisture content than other two cell wall polymers which might be attributed to the softening of hemicelluloses in higher relative humidity (Fig. 2a,b,c). Lignin showed higher hysteresis than cellulose in different relative humidity. Hemicellulose demonstrated the relatively low hysteresis until 50% RH, and with increasing the ambient pressure from 60% RH the hemicelluloses exhibited the extremely higher hysteresis than other cell wall polymers.

  • 323.
    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 reagent2016Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 3, s. 253-259Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 324.
    Hosseinpourpia, Reza
    et al.
    Georg-August-University Göttingen.
    Mai, Carsten
    Georg-August-University Göttingen.
    Mode of action of brown rot decay resistance of acetylated wood: resistance to Fenton’s reagent2016Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, nr 2, s. 413-426Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acetylation is known to enhance the resistance of wood to brown rot fungi. As initial decay by some brown rot fungi is assumed to be caused by the Fenton reaction, pine micro-veneers acetylated to various weight percent gains (WPG) were exposed in a solution containing iron ions and hydrogen peroxide, i.e., Fenton’s reagent. Mass loss and tensile strength loss as well as the decomposition of hydrogen peroxide within the incubation time decreased with increasing WPG of the veneers. Incubation of untreated and acetylated veneers in acetate buffer containing ferric ions without H2O2 revealed that the modification strongly reduced the uptake of Fe ions by the wood cell wall. FT-IR analysis indicated oxidation of the unmodified control veneers but did not show predominant decay of specific cell wall components. Spectra of acetylated veneers did not reveal any significant changes induced by Fenton’s reagent. It was concluded that one possible reason for the enhanced resistance of acetylated wood to the Fenton reaction could be the reduced or almost completely prevented uptake of Fe ions by the wood cell wall.

  • 325.
    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 reagent2016Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 70, nr 7, s. 691-697Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 326.
    Hosseinpourpia, Reza
    et al.
    Islamic Azad University, Iran ; Georg-August University, Germany.
    Hosseini, Payam
    Sharif University of Technology, Iran.
    Mofidian, Seyedehrashin
    Mazandaran University of Science and Technology, Iran.
    Hosseinpourpia, Rezvan
    Islamic Azad University, Iran.
    Varshoee, Ali
    Islamic Azad University, Iran.
    Influence of Nanosilica on Properties of Green Cementitious Composites Filled with Waste Sulfite Pulp Fiber and Aminosilane2014Inngår i: The Arabian Journal for Science and Engineering, ISSN 1319-8025, Vol. 39, nr 4, s. 2631-2640Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Developments in the field of green cement-based products are characterized as an important approach to sustainable development and are being devoted much attention by the construction industry. Numerous types of materials are utilized; however, based on other published studies, the use of waste material as a filler normally deteriorates the performance of cementitious products. Appropriate additives thus need to be employed to improve the performances and properties of green products. As a consequence, the aim of this study has been to investigate the properties of a novel green cement-based composite—a hybrid system composed of cement, waste natural fiber, silica nano-particles, and aminosilane. Experiments were performed to assess the physical properties (density and flowability), mechanical properties (compressive strength and bending performance), and microstructural properties (as determined by scanning electron microscopy) of the cement sheets. The results demonstrated an improvement in the mechanical and microstructural properties of green cement-based composites by using this hybrid system.

  • 327.
    Hosseinpourpia, Reza
    et al.
    Islamic Azad University, Iran ; Georg-August University, Germany.
    Varshoee, Ali
    Islamic Azad University, Iran.
    Soltani, Mojtaba
    Islamic Azad University, Iran.
    Hosseini, Payam
    Sharif University of Technology, Iran.
    Ziaei Tabari, Hassan
    Islamic Azad University, Iran.
    Production of waste bio-fiber cement-based composites reinforced with nano-SiO2 particles as a substitute for asbestos cement composites2012Inngår i: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 31, s. 105-111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The environmental impact of asbestos fibers on human health and their consequent safety-related problems indicate that there is a significant need to replace this material in all asbestos-containing products. Many different types of fibers have been introduced to replace asbestos fibers.

    In this study, the performance of silica nano-particles combined with waste paper pulp fibers (sulfite fibers) has been investigated. Different mechanical (compressive and flexural strengths and bending performance), durability (water absorption), physical (bulk density and flowability), and microstructural (scanning electron microscopy) tests were conducted to examine the properties of manufactured green composites.

    The results reveal that the mechanical properties of cement-based composites containing a ternary system of “natural waste fiber–silica nano-particle cement” have been enhanced. Adding silica nano-particles allows the development of green cement-based composites and movement toward sustainable development in the concrete industry.

  • 328.
    Hu, Min
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Local variation in bending stiffness in structural timber of Norway spruce: for the purpose of strength grading2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Most strength grading machines on the European market use an averagemodulus of elasticity (MOE), estimated on a relatively large distance along awood member, as the indicating property (IP) to bending strength. Theaccuracy of such grading machines in terms of coefficient of determination israther low at R2 ≈ 0.5. This research is motivated by a desire to increase theaccuracy of the strength grading in the industry today. The aim of the presentstudy is to contribute knowledge of local variation in bending stiffness/MOEwith high resolution and thus locate weak sections due to stiffness reducingfeatures (the most important is knots) for structural timber.The present study introduces three methods that involve structural dynamics,classical beam theory and optical measurement to assess local wood stiffness.Specifically:

    • The dynamic method, in which a wood member is treated as an ordinaryphysical structure and the local stiffness is studied by exploring itsdynamic properties.
    • In Method II, a bending MOE profile is established based on local fibre angle information. The local fibre orientation is detected through highresolution laser scanning based on the tracheid effect.
    •  For Method III, a bending MOE profile is established using surfacestrain information under four-point bending. A high resolution strainfield is obtained using the digital image correlation (DIC) technique.

    From the present study, the two latter methods are more favourable inevaluating the local stiffness within a piece of structural timber. Moreover, thestudy reveals that the established bending MOE profiles using the two lattermethods, i.e. based on information of the local fibre angle and surface strain,agree reasonably well. However, for some patterns of knot clusters, the localbending MOE, calculated on the basis of fibre angles, is significantly higherthan the local bending MOE estimated on the basis of surface strain.

  • 329.
    Hu, Min
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Studies of the fibre direction and local bending stiffness of Norway spruce timber: for application on machine strength grading2018Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Machine strength grading is a production process in the sawmill industry used to grade sawn timber boards into different strength classes with specific characteristic values of the bending strength, modulus of elasticity (MOE) and density. These properties are called grade determining properties. Each of these is predicted on the basis of a statistical relationship between the property and a so-called indicating property (IP), which is based on non-destructively assessed board properties. In most cases, the prediction of strength is crucial for the grading. The majority of commercial grading machines rely on a statistical relationship of strength to an IP, which is either a global dynamic MOE or an averaged flatwise bending MOE measured over a board length of about one meter. The problem of today’s machine strength grading is that the accuracy of the strength prediction is rather poor with a coefficient of determination of about R2 ≈ 0.5 − 0.6. One consequence of this is that much of the strength potential of timber is unused.

    The intention of this research is to contribute to a long-term goal, which is development of a method for prediction of bending strength that is more accurate than the methods available today. The research relies on three hypotheses. First, accurate prediction of bending strength can be achieved using an IP that is a localized MOE value (determined over a short length) that represents the lowest local bending stiffness of a board. Second, knowledge of the local bending stiffness with high resolution along a board’s longitudinal direction can be established on the basis of fibre direction within the board in combination with dynamic MOE. Third, fibre directions in the interior of a board can be determined by application of fibre angle models utilizing data of fibre directions on the board’s surfaces obtained from tracheid effect scanning. Following these hypotheses, this work has included laboratory investigations of local material directions, and development of models for fibre directions of the interior of boards. The work also included application of one-dimensional (1D) analytical models and three-dimensional (3D) finite element models of individual boards for the mechanical behaviour, analysis of mechanical response of boards based on experiments and based on the suggested models. Lastly, the suggested models were evaluated by comparisons of calculated and experimentally determined local bending stiffness along boards, and of predicted and experimentally determined bending strength.

    The research contributes with in-depth knowledge on local fibre directions close to knots, and detailed information on variation of the local bending stiffness in boards. Moreover, fibre angle models for fibre directions in the interior of boards are presented. By application of the fibre angle models in the 3D model of the whole board, the local bending stiffness along timber boards can be determined over a very short length (l < 50 mm). A comparison with results determined on an experimental basis show a very close similarity implying that the applied models are sufficient to capture the variation of local bending stiffness, caused by knots and fibre distortions, with very high accuracy. Furthermore, it is found that by means of IPs derived using the suggested models, bending strength can be predicted with high accuracy. For a timber sample comprising 402 boards, such IPs results in coefficient of determination as high as R2 = 0.73. However, using IPs based on the 3D finite element model did not improve the R2 value achieved when using the IPs based on the 1D model.

  • 330.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Briggert, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation2018Inngår i: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, nr 1, s. 7-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The strength of structural timber largely depends on the occurrence of knots and on the local material directions in the surroundings of such knots. There is, however, a lack of methods for establishing a full dataset of the local material directions. The present research aims at the development and application of a laboratory method to assess the geometry of growth layers and the orientation of fibres in a high-resolution 3D grid within wood specimens containing knots. The laboratory method was based on optical flatbed scanning and laser scanning, the former resulting in surface images and the latter, utilizing the tracheid effect, resulting in in-plane fibre angles determined in high-resolution grids on scanned surfaces. A rectangular solid wood specimen containing a single knot was cut from a tree in such a way that it could be assumed that a plane of symmetry existed in the specimen. By splitting the specimen through this plane through the centre line of the knot, two new specimens with assumed identical but mirrored properties were achieved. On one of the new specimens, the longitudinal-radial plane was subsequently scanned, and the longitudinal–tangential plane was scanned on the other. Then, by repeatedly planing off material on both specimens followed by scanning of the new surfaces that gradually appeared, 3D coordinate positions along different growth layers and 3D orientation of fibres in a 3D grid were obtained. Comparisons between detected fibre orientation and growth layer geometry were used for the assessment of the accuracy obtained regarding 3D fibre orientation. It was shown that the suggested method is well suited to capture growth layer surfaces and that it provides reliable information on 3D fibre orientation close to knots. Such knowledge is of great importance for understanding the properties of timber including knots. The quantitative data obtained are also useful for calibration of model parameters of general models on fibre orientation close to knots.

  • 331.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Briggert, Andreas
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Säll, Harald
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Three dimensional growth layer geometry and fibre orientation around knots: a laboratory investigation2016Inngår i: Proceedings of WCTE 2016 World Conference on Timber Engineering / [ed] Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, 2016Konferansepaper (Fagfellevurdert)
  • 332.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Enquist, Bertil
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för bygg- och energiteknik (BE).
    Comparison of local variation of modulus of elasticity determined on basis of scanned fiber angles and full strain field measurements2013Inngår i: The 18th International Nondestructive Testing and Evaluation of Wood Symposium, Madison, WI, USA, 2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Strength grading methods are normally based on relationships between one measured value of modulus of elasticity (MOE), regarded as being valid for the whole board, and bending strength. Studies have shown, however, that with a detailed knowledge of local variation of MOE within boards, a highter coefficient of determination (R2) with respect to bending strength can be obtained. Measurements of fiber angles from laser scanning has shown to be a powerful tool to establish MOE profile along boards in a speed that cooresponds to the production speed at a sawmill. The present study aims at investigating the accuracy of the local MOE profile determined on basis of fiber angles from laser scanning. The study was carried out on a board of Norway spruce of dimension 50 by 150 by 3,900 mm. First the fiber angles on all four surfaces were identified using a WoodEye scanner and on the basis of these measurements, a MOE profile was calculated. Thereafter, the board was subjected to a constant bending moment and suring loading an image correlation system, Aramis, was employed for detection of the strain field with high resolution along the whole board. This strain field was then used to estanlish a 'true' MOE profile along the board. The MOE profiles determined in two different ways were compared and they show a close compliance. However, some difference were found and these were used for calibration of the method for MOE determination on the basis of scanning results. The present research thus contributes further improvement of a newly suggested grading method.

  • 333.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Modelling local bending stiffness based on fibre orientation in sawn timber2018Inngår i: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, nr 6, s. 1605-1621Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Strength of structural timber depends to a high degree on the occurrence of knots and on the local fibre deviation around such defects. Knowledge of local fibre orientation, obtained by laser scanning, has been utilized in a previously developed machine strength grading method, but rather crude assumptions regarding the fibre orientation in the interior of boards and a mechanical model that does not capture the full compliance of knotty sections were adopted. The purpose of the present study was to suggest and verify a model with which local bending stiffness can be predicted with high accuracy. This study included development of a model of fibre orientation in the interior of boards, and application of a three-dimensional finite element model that is able to capture the compliance of the board. Verification included bending of boards in the laboratory and application of digital image correlation to obtain strain fields comparable to those obtained by finite element simulation. Results presented comprise strain fields of boards subjected to bending and calculated bending stiffness profiles along boards. Comparisons of results indicated that the model suggested here was sufficient to capture the variation of local bending stiffness along boards with very high accuracy.

  • 334.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Johansson, Marie
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Oscarsson, Jan
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Serrano, Erik
    Lund University.
    Assessment of a Three-Dimensional Fiber Orientation Model for Timber2016Inngår i: Wood and Fiber Science, ISSN 0735-6161, Vol. 48, nr 4, s. 271-290Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wood is an orthotropic material with very different properties along and across fibers, and every board has its own pattern of knots and fiber deviations. Therefore, detailed knowledge of the three-dimensional (3D) fiber orientation of individual boards would enable more accurate assessment of properties such as stiffness, strength, and shape stability. This paper presents a method for modeling 3D fiber orientation of side boards of Norway spruce. The method is based on dot laser scanning and utilization of the tracheid effect, and it is verified by a comparison between strain fields calculated on the basis of the fiber orientation model and corresponding strains determined using digital image correlation (DIC) technique. By means of the method, it is possible to identify knots and to reproduce the fiber orientation in clear wood in the vicinity of knots. Fiber orientation models of side boards including traversing edge knots were established and integrated in finite element models of boards used for simulation of four-point bending tests. The same boards were also tested in laboratory and displacement fields of the wide faces were recorded at different load levels using DIC technique. Comparisons of strain fields from measurements and simulations showed close agreement, regarding both strain patterns and strain levels. Local strain concentrations caused by very small defects were detected using the models and also found from the laboratory test results. The modeling approach may be used both to achieve improved accuracy of existing machine strength grading methods and, after further development, also for more advanced analysis of eg crack propagation and strength of timber.

  • 335.
    Huber, Johannes Albert Josef
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Ekevad, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Girhammar, Ulf Arne
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Träteknik.
    Review of Robustness in Timber Buildings2017Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Timber buildings today aim for taller and larger dimensions to accommodate increased numbers of occupants.  In tall buildings, more human lives are at risk if large portions of the structure collapse progressively during catastrophic failure events. To safeguard timber structures from disproportionate collapse due to localised failures, the aspect of robustness in particular needs to be considered. In the literature about building structures the term robustness seems to be contemplated in diverse ways. Several possible approaches to define and analyse this property can be found. However, certain consensus as to what characterises a robust structure seems to exist. A review of the concept of robustness for building structures in general and timber structures in specific is presented in this paper. Certain commonly applied terminology and definitions in the context of robustness are analysed. In the literature, risk-based, reliability-based and performance-based concepts for robustness appear to be established. The first two concepts are briefly summarised. The performance-based concept is treated in greater detail to highlight different procedures of deterministic robustness analyses. Common general characteristics of robust buildings which seem to be agreed upon are summarised. Robustness provisions for timber buildings in specific are described and compared to provisions in other building materials such as steel and concrete. The development of alternate load paths during local failure seems to play an essential role in preventing progressive collapse in buildings. The literature about robustness seems to be comprehensive concerning general considerations and concerning structures built in concrete or steel but appears to be rather limited in regards to timber structures. Evaluations of robustness in timber structures seem to be focused on risk-based and reliability-based concepts in literature.

  • 336.
    Huc, Sabina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik. Univ Boras, Fac Text Engn & Business, SE-50190 Boras, Sweden.
    Svensson, Staffan
    Univ Boras, Fac Text Engn & Business, SE-50190 Boras, Sweden.
    Hozjan, Tomaz
    Univ Ljubljana, Fac Civil & Geodet Engn, SI-1000 Ljubljana, Slovenia.
    Hygro-mechanical analysis of wood subjected to constant mechanical load and varying relative humidity2018Inngår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 72, nr 10, s. 863-870Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A hygro-mechanical (H-M) analysis of a wooden specimen sustaining a mechanical load while subjected to varying relative humidity was performed to predict the long-term rheological behavior of wood. The numerical analysis was based on the experimental results of total strains, monitored in two orthotropic material directions on oak wood specimens under constant uniaxial compression and with moisture content (MC) variation. For the moisture analysis, a multi-Fickian moisture transport model (MFMTM) was used to obtain temporal and spatial MC fields, which were the input data in the mechanical analysis. The presented mechanical model assumed a decomposition of the total strains into the elastic, viscoelastic and mechanosorptive strains and the strains due to shrinkage and swelling. The moisture and mechanical analyses required material parameters, which were taken from the literature or were empirically obtained by a fitting procedure. The performed H-M analysis gave accurate numerical predictions of the experimentally obtained total strains in two orthotropic directions simultaneously. Thus, the analysis developed has a high potential for predicting the long-term rheological behavior of timber structures, assuming that the material parameters are determined previously, based on specific, extensive, multidimensional experimental analyses.

  • 337.
    Hu, Min
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY).
    Olsson, Anders
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggteknik (BY). Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för byggd miljö och energiteknik (BET).
    Local bending stiffness for prediction of bending strength: Evaluation of models and conceptManuskript (preprint) (Annet vitenskapelig)
  • 338.
    Izekor, David
    et al.
    University of Benin, Nigeria.
    Amiandamhen, Stephen
    University of Benin, Department of Forestry and Wildlife Management.
    Combustion properties of briquettes produced from sawdust of three different indigenous wood species2013Inngår i: Journal of Agriculture and Environment, Vol. 9, nr 1 & 2, s. 107-111Artikkel i tidsskrift (Fagfellevurdert)
  • 339.
    Izekor, David
    et al.
    University of Benin, Department of Forestry and Wildlife Management.
    Amiandamhen, Stephen
    University of Benin, Department of Forestry and Wildlife Management.
    Utilization of fuelwood as household energy among residents of Benin metropolis, Edo State, Nigeria2017Inngår i: Nigerian Journal of Agriculture, Food and Environment, ISSN 0331-0787, Vol. 13, nr 2, s. 174-178Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The study evaluates the utilization of fuelwood as household energy among residents in Benin metropolis. Its utilization andavailability as household energy source as well as reasons for its preference to other household energy sources was assessed.A random sampling technique was used to select 10 communities within the study area namely; Uselu, Siluko, Uwelu, Ogbaarea, Airport road, Ekehuan, Evbotubu, Aduwawa - Urora quarters, Upper sakponba The survey was carried out in theseareas with the aid of a semi-structured questionnaire administered to respondents who utilize and sell fuelwood in thesecommunities. A total of 200 copies of questionnaire were administered. The main variables measured were those of fuel woodconsumption, availability and sources of fuelwood utilization. The results showed that the 50% of the respondents utilizedfuelwood as their source of domestic house hold energy. 51% of the respondents sourced their fuelwood from fuelwoodvendors while 25% source for fuelwood from their local farmland. 60% of the respondents in the study area spent an averageof N200 daily on fuelwood while 52% of the respondents have a weekly expense of above N700 on fuel wood utilization. Theaverage weekly consumption of fuelwood by 50% of the respondents was between 22 – 27 kg. Hevea braziliensis representing33% of fuelwood species was the most abundant fuelwood consumed by residents in the study araea. The results from T-testand Pearson correlation showed that there was a significant difference in the amount of fuelwood consumed in the differentcommunities within the study area. Therefore the quantity of fuelwood consumed is related to the number of persons perhousehold.

  • 340.
    Izekor, David
    et al.
    University of Benin, Nigeria.
    Amiandamhen, Stephen
    University of Benin, Nigeria.
    Agbarhoaga, Stephen
    University of Benin, Nigeria.
    Effects of geometric particle sizes of wood flour on strength and dimensional properties of wood plastic composites2013Inngår i: Journal of Applied and Natural Science, ISSN 0974-9411, Vol. 5, nr 1, s. 194-199Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of different wood flour sizes on strength and dimensional properties of wood-plastic compositeswere examined. Wood flour of different particle sizes viz; 1.00mm, 2.00mm and >2.00mm were compounded withrecycled low-density polyethylene (LDPE) at different wood/plastic ratio of 1: 1, 2: 3 and 3: 2. The results obtainedshowed that wood flour size > 2.00mm has the highest MOR and MOE values of 1.206N mm-2 and 2484.72Nmm-2while wood flour size of 1.00mm had the lowest MOR and MOE values of 0.505Nmm-2 and 2195.89Nmm-2 respectively.Also the results of the physical properties showed that wood flour size of 1.00mm had the lowest thickness swellingpercentage with mean values of 0.28% and 2.08% while water absorption percentage has mean values of 0.91%and 10.58% after 2 hours and 24 hours of water immersion respectively. It was observed that wood flour size of2.00mm and particle size >2.00mm had the highest thickness swelling and water absorption percentages. Thisshowed that strength properties of wood plastic composites increased with increased particle sizes whereas itsdimensional properties increased with decreased particle sizes. The results of analysis of variance carried out onmechanical and physical properties showed that particle sizes and wood/plastic ratio had a significant effect on themechanical and physical properties of wood plastic composites (p 0.05).

  • 341.
    Izekor, David
    et al.
    University of Benin, Nigeria.
    Amiandamhen, Stephen
    University of Benin, Nigeria.
    Awenagbiku, E
    University of Benin, Nigeria.
    Effect of taper and sawing methods on log conversion among selected sawmills in Edo State, Nigeria2016Inngår i: Nigerian Journal of Forestry, Vol. 46, nr 1-2, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study was carried out to determine the effect of taper and sawing methods on log conversion among selected sawmills in Egor andOvia-North East Local Government Areas of Edo State. Ten representative sawmills and thirty round logs were sampled for eachspecies making a total of 300 logs based on the relative abundance of available timber species were sampled. The diameter of the logs,length and girth at small and large ends were measured before conversion. The data were analyzed using descriptive statistics. Theresults obtained showed that Egor Local Government Area has the highest frequency of the selected species representing 56% of totallogs sampled while Ovia North-East Local Government Area has 44% of total logs sampled. Conversion efficiency varied from 56.49to 76.26%. Factors such as inherent defect in the timber, age of the machine and the severity of the log taper affected conversionefficiency at the sawmills. Lumber recovery efficiency increases with bigger log, short log length and narrower taper. Therefore, logsize, taper and log length have positive relationship on lumber recovery efficiency.

  • 342.
    Izekor, David
    et al.
    University of Benin, Nigeria.
    Amiandamhen, Stephen
    University of Benin, Nigeria.
    Comparative analysis on the trends in the volume of logs supplied to sawmills in Edo State, Nigeria2011Inngår i: Journal of the Nigerian Society for Experimental Biology, ISSN 1595-6938, Vol. 11, nr 3, s. 257-263Artikkel i tidsskrift (Fagfellevurdert)
  • 343.
    Jalilzadehazhari, Elaheh
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Material properties of wooden surfaces used in interiors and sensory stimulation2019Inngår i: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By covering interiors, such as walls, ceilings and floors, with wooden surfaces, one can change the quality of indoor environments and thereby affect both psychological and physiological responses. Psychological responses refer to individuals’ emotional reactions toward interiors, while physiological responses include changes in the activity of the brain, the autonomic nervous system, the endocrine system, and the immune system. The above-mentioned responses considered in this study are those caused by visual, auditory, olfactory and tactile stimulation from interior wooden surfaces. Although earlier studies have presented valuable information on this subject, questions remain about the material properties of wood which are associated with the stimulation. Specifying the material properties can support architects, designers and engineers who intend to use wood in interiors for improving psychological and physiological responses. A literature study therefore has been conducted to determine (i) the material properties of wood which are associated with sensory stimulation, and (ii) to specify relevant recommendations or requirements which should be fulfilled when covering interiors with wooden surfaces. The results show a lack of knowledge regarding the material properties of wood and the degree in which it affects sensory stimulation.

  • 344. Janga, K.K.
    et al.
    Öyaas, K.
    RISE., Innventia, PFI – Paper and Fiber Research Institute.
    Hertzberg, T.
    Moe, S.T.
    Application of a pseudo-kinetic generalized severity model to the concentrated sulfuric acid hydrolysis of pinewood and aspenwood2012Inngår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, s. 2728-2741Artikkel i tidsskrift (Fagfellevurdert)
  • 345.
    Jansson, M.B.
    et al.
    RISE, Innventia.
    Aldaeus, F.
    RISE, Innventia.
    Reimann, A.
    RISE, Innventia.
    Ljungquist, P.
    RISE, Innventia.
    Schweinebarth, H.
    RISE, Innventia.
    Boklund, M.
    Extraction of bioactive chemicals in spruce wood residues2011Konferansepaper (Fagfellevurdert)
  • 346. Jensen, Anders Vestergaard
    et al.
    Craig, Nic
    Wood in Construction - 25 cases of Nordic Good Practice2019Annet (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Building with wood has an untapped potential to transform the construction industry and create the next generation of low-carbon and healthy buildings. The Nordics, with an abundance of sustainably managed forest resources and a long history of building in wood, are well placed to lead in this construction revolution. Across the wood in construction value chain, from forestry and processing, through production and design, to construction and decommission, the Nordic region is innovating to build bigger and more sustainably with wood than ever before.

    This publication features 25 Nordic cases from across the value chain working with wood in exciting and innovative ways. These projects demonstrate the benefits and drivers for building with wood, and provide inspiration for architects, land managers, city planners, designers, suppliers and many more. The 25 cases point to five trends within Nordic wood in construction that paint a picture of where the industry is headed: 1) multifunctionality; 2) saving time and costs; 3) investing in scalability; 4) pushing the boundaries; and 5) circular design.

    The team behind this report – the Nordic Wood in Construction Secretariat – is an initiative commissioned by the Nordic Council of Ministers and the Swedish Government, and hosted by EIT Climate-KIC. The secretariat’s aim is to support and accelerate the use of wood in Nordic construction through a portfolio of projects, fostering greater dialogue, knowledge-sharing and collaboration between stakeholders from the private sector, public sector, and academia.

  • 347.
    Jiang, Wen
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Kumar, Anuj
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT). Natural Resources Institute Finland (Luke), Finland.
    Adamopoulos, Stergios
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Liquefaction of lignocellulosic materials and its applications in wood adhesives — A review2018Inngår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 124, s. 325-342Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Liquefaction, a useful method of turning whole biomass into liquids, provides advantages for energy andpolymers and finds applications in many sectors. This paper reviews the different liquefaction technologies andrecent advances in the development of sustainable wood adhesives. Current liquefaction technologies includehydrothermal liquefaction (HTL) and moderate acid-catalyzed liquefaction (MACL). HTL produces bio-oils asprimary products, and solid residues and gases as by-products. MACL depends on the solvent types used, whichare grouped to polyhydric alcohols and phenols. Bio-polyols from alcohol liquefaction, phenolated biomass fromphenol liquefaction and phenolic compounds rich-HTL bio-oils have been used in the production of liquefiedbiomass-based adhesives, which have shown competitive properties but face challenges for industrial uses. Yet, abetter understanding of reaction pathways and optimization of the liquefaction processes is needed.

  • 348.
    Johansson, Amanda
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för skog och träteknik (SOT).
    Granvirkes permeabilitet beroende av dess fysikaliska utformning och applicerat färgsystem2015Independent thesis Basic level (degree of Bachelor), 180 hpOppgave
    Abstract [sv]

    Densitetsmätningar och permeabilitetstest enligt EN 927-5 har utförts för att studera huruvida granvirkes fysikaliska egenskaper i kombination med applicerat färgsystem påverkar permeabiliteten. De egenskaper som studerats är frod- och senvuxenhet, splint- och kärnved samt densitet. Aktuella färgsystem som studerats är alkyd, akrylat och linolja, vilka jämförts med omålad referens. Studien påvisar inget samband mellan virkets densitet och permeabilitet, bestruket eller ej. Det som istället tycks påverka vattenabsorptionen är närvaro av splint-/kärnved samt frod-/senvuxenhet. Senvuxen kärnved var den bestrukna vedtyp som absorberade mest vatten gällande samtliga färgsystem. Vedtyp som hade lägst vattenabsorption varierade dock. Linolja var generellt det färgsystem som gav lägst permeabilitet, främst på frodvuxen kärnved. Denna kombination hade lägst absorption genom hela försöket.

  • 349.
    Johansson, Ingvar
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    Kungliga Tekniska Högskolan (KTH), Träteknologi.
    Plastisk deformation hos trä utsatt för varierande fuktbelastning: Förstudie1994Rapport (Annet vitenskapelig)
  • 350.
    Johansson, Jimmy
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Institutionen för teknik och design.
    Mechanical processing for improved products made from Swedish hardwood2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Swedish hardwood is today used in the energy, pulp and mechanical hardwood industries. Only very small volumes of Swedish hardwood are, however, consumed by the mechanical industry that normally pays the highest timber price. The smallness of the volumes used for mechanical refinement is a result both of forestry not focusing on the production of hardwood for these uses, and of the fact that the mechanical hardwood industry, particularly the sawing industry, is not designed to process the existing raw material in an optimal manner. This thesis discusses the possibilities of improving the conditions for the mechanical refinement of hardwood. The aim of the work has been to investigate the possibilities of developing products and methods for processing of Swedish hardwood.

    The thesis proposes a new manufacturing system for Swedish hardwood to better utilize the inherent properties of the wood material. The system is based on the so-called PrimWood Method and the star-sawing concept. Compared to normally sawn wood, the sawing concept utilizes the raw material more efficiently with regard to volume yield, and increases the distance between knots in the sawn wood. The material produced has vertical annual rings which give the wood smaller movements as a result of moisture variations and a different textural appearance. Using the PrimWood Method for hardwood would make it possible to more closely match customer requirements regarding hardwood products.

    Since Swedish hardwood is nowadays mainly used indoors, a possible way of expanding the market would be to increase the outdoor use of the material. Here the durability is of great importance, and one important factor is then the capillary characteristics of the material. The thesis therefore focuses on the characterisation of the capillarity in wood for the future improvement of its durability. It is shown that with the material produced by the proposed manufacturing system, i.e. wood with vertical annual rings, the possibility of using hardwood outdoors increases, because the susceptibility to cracking decreases.

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