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  • 251.
    Hosseinpourpia, Reza
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Hemmilä, Venla
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Effect of Bio-Based Additives on Physico-Mechanical Properties of Medium Density Fibreboards2017In: 28th ICWST, International Conference on Wood Science and Technology: Implementation of Wood Science in Woodworking Sector, Proceedings. Zagreb, 7th - 8th of December 2017 / [ed] Ivica Zupcic, Vjekoslav Zivkovic, Josip Miklecic, Zagreb: University of Zagreb, Faculty of Forestry , 2017, p. 153-158Conference paper (Refereed)
    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.   

  • 252.
    Hosseinpourpia, Reza
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Taghiyari, Hamid Reza
    Shahid Rajaee Teacher Training University, Iran.
    Properties of medium-density fibreboards bonded with dextrin-based wood adhesive2019In: Wood research, ISSN 1336-4561, Vol. 64, no 2, p. 185-194Article in journal (Refereed)
    Abstract [en]

    This study focuses on manufacturing of medium density fibreboard (MDF) panels bonded with dextrin-based wood adhesive and crosslinked in situ with various weight ratios of synthetic (e.g., polymeric-methane diphenyl-diisocyanate, pMDI) or bio-based (e.g., glyoxal) crosslinkers. The physical and mechanical properties of the panels were evaluated and compared with those from panels without crosslinker (control). Modulus of rupture (MOR) and internal bond (IB) strength of the MDF panels were considerably increased by increasing the crosslinkers’ content. While, slight improvements were observed in modulus of elasticity (MOE) of the panels as a function of crosslinker type and content. Addition of crosslinkers clearly reduced the thickness swelling (TS) and water absorption (WA) of the panels, whereas, the panels with pMDI showed superior performances than the control and glyoxal added ones within 4 h and 24 h immersion in water. The results indicate the potential of dextrin as wood panel adhesive along with the use of appropriate crosslinkers.

  • 253.
    Hosseinpourpia, Reza
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Parsland, Charlotte
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Utilization of different tall oils for improving the water resistance of cellulosic fibers2019In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 136, no 13, article id 47303Article in journal (Refereed)
    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.

  • 254.
    Hosseinpourpia, Reza
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Echart, Arantzazu Santamaria
    University of the Basque Country UPV/EHU, Spain.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    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 Groups2018In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 10, no 9, article id 939Article in journal (Refereed)
    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.

  • 255.
    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 Aminosilane2014In: The Arabian Journal for Science and Engineering, ISSN 1319-8025, Vol. 39, no 4, p. 2631-2640Article in journal (Refereed)
    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.

  • 256.
    Hosseinpourpia, Reza
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Göttingen university, Germany.
    Mai, Carsten
    Dynamic water vapour sorption properties of wood cell wall polymer constituents2015In: 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, p. 42-44Conference paper (Refereed)
    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.

  • 257.
    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.

  • 258.
    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 reagent2016In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, no 2, p. 413-426Article in journal (Refereed)
    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.

  • 259.
    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.

  • 260.
    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 composites2012In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 31, p. 105-111Article in journal (Refereed)
    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.

  • 261.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local variation in bending stiffness in structural timber of Norway spruce: for the purpose of strength grading2014Licentiate thesis, comprehensive summary (Other academic)
    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.

  • 262.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Studies of the fibre direction and local bending stiffness of Norway spruce timber: for application on machine strength grading2018Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 263.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Briggert, Andreas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Growth layer and fibre orientation around knots in Norway spruce: a laboratory investigation2018In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, no 1, p. 7-27Article in journal (Refereed)
    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.

  • 264.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Briggert, Andreas
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Säll, Harald
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Three dimensional growth layer geometry and fibre orientation around knots: a laboratory investigation2016In: Proceedings of WCTE 2016 World Conference on Timber Engineering / [ed] Eberhardsteiner, W. Winter, A. Fadai, M. Pöll, Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
  • 265.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Comparison of local variation of modulus of elasticity determined on basis of scanned fiber angles and full strain field measurements2013In: The 18th International Nondestructive Testing and Evaluation of Wood Symposium, Madison, WI, USA, 2013Conference paper (Refereed)
    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.

  • 266.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Local bending stiffness for prediction of bending strength: Evaluation of models and conceptManuscript (preprint) (Other academic)
  • 267.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Modelling local bending stiffness based on fibre orientation in sawn timber2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 6, p. 1605-1621Article in journal (Refereed)
    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.

  • 268.
    Hu, Min
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Serrano, Erik
    Lund University.
    Assessment of a Three-Dimensional Fiber Orientation Model for Timber2016In: Wood and Fiber Science, ISSN 0735-6161, Vol. 48, no 4, p. 271-290Article in journal (Refereed)
    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.

  • 269.
    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 species2013In: Journal of Agriculture and Environment, Vol. 9, no 1 & 2, p. 107-111Article in journal (Refereed)
  • 270.
    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, Nigeria2011In: Journal of the Nigerian Society for Experimental Biology, ISSN 1595-6938, Vol. 11, no 3, p. 257-263Article in journal (Refereed)
  • 271.
    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, Nigeria2017In: Nigerian Journal of Agriculture, Food and Environment, ISSN 0331-0787, Vol. 13, no 2, p. 174-178Article in journal (Refereed)
    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.

  • 272.
    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 composites2013In: Journal of Applied and Natural Science, ISSN 0974-9411, Vol. 5, no 1, p. 194-199Article in journal (Refereed)
    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).

  • 273.
    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, Nigeria2016In: Nigerian Journal of Forestry, Vol. 46, no 1-2, p. 1-6Article in journal (Refereed)
    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.

  • 274.
    Jalilzadehazhari, Elaheh
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Material properties of wooden surfaces used in interiors and sensory stimulation2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 4, p. 192-200Article in journal (Refereed)
    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.

  • 275. Jiang, W
    et al.
    Medved, S
    Adamopoulos, S
    Particleboards with partially liquefied bark of different sizes2019Conference paper (Refereed)
    Abstract [en]

    Utilizing biomass waste for wood-based composites has been driven by harsh competition for raw materials and environmental concerns for more sustainable products. Bark, as a by-product of the sawmilling and pulping industries, is a lignocellulosic material that is rich in lignin and extractives, and holds potential for producing chemicals and value-added materials. There are many possibilities of using bark in wood-based panel manufacturing such as making adhesives (e.g. bark tannin extractives, liquefied bark) or using it as a furnish in small amounts. Instead of using the completed liquefied bark products in the adhesive mixture, we have been working on a novel method of making particleboards by using partially liquefied bark as a furnish material with binding abilities. Thus, partially liquefied bark was mixed with wood chips with an aim to investigate the effect of different bark sizes on the properties of particleboards.Maritime pine (Pinus pinaster Ait.) bark was partially liquefied in the presence of ethylene glycol as solvent and sulphuric acid (H2SO4) as catalyst in 180˚C for 30 minutes. Four different sizes of bark were used: mix, coarse (> 2 mm), middle (1-2 mm), and fines (< 1 mm). One-layered 8-mm particleboards were prepared by mixing dry wood chips with the partially liquefied bark categories (9.1% or 20% w/w). Melamine-urea-formaldehyde (MUF) resin was 10% of the total weight of the furnish materials (dry wood chips and partially liquefied bark); while boards were also made without adding the resin. Mechanical and physical properties of the particleboards were tested according to the European standards, and ANOVA analysis of the results showed no statistically significant differences between varying bark sizes. Particleboards made with 9.1% of partially liquefied bark and with 10% of MUF resin met all the standard requirements for mechanical strength and thickness swelling. Particleboards made with 20% of partially liquefied bark and without adding MUF resin were inferior to those with MUF resin.From the current results we can conclude that it is possible to make particleboards from partially liquefied bark with competitive properties, and this supports our original idea of not completing the liquefaction process. In that respect, our work can contribute to energy and material savings when using liquefied products in wood panel manufacturing. More research is needed to optimize the process as well as to evaluate the formaldehyde emission level from this type of panels. 

  • 276.
    Jiang, Wen
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Kumar, Anuj
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Natural Resources Institute Finland (Luke), Finland.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Liquefaction of lignocellulosic materials and its applications in wood adhesives — A review2018In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 124, p. 325-342Article in journal (Refereed)
    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.

  • 277.
    Jiang, Wen
    et al.
    University of Eastern Finland, Finland.
    Tomppo, Laura
    University of Eastern Finland, Finland.
    Pakarinen, Timo
    Karelia University of Applied Sciences, Finland.
    Sirviö, Juho A.
    University of Oulu, Finland.
    Liimatainen, Henrikki
    University of Oulu, Finland.
    Haapala, Antti
    University of Eastern Finland, Finland.
    Effect of Cellulose Nanofibrils on the Bond Strength of Polyvinyl Acetate and Starch Adhesives for Wood2018In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 13, no 2, p. 2283-2292Article in journal (Refereed)
    Abstract [en]

    Nanocellulose is a competitive reinforcement material for usein biocomposite structures and fibrous products. In this study, adhesive mixtures of dicarboxylic acid cellulose nanofibrils (CNF) were dispersed into commercial polyvinyl acetate (PVAc) and starch adhesives, whichwere applied to Norway spruce (Picea abies) to assess their performance in wood joining. Single-lap joints were prepared and tested with PVAc mixtures with0 to 0.64 wt% CNFand starch glue mixtures containing 0 to 1.07 wt% CNF. CNF suspensionshaving three concentrations(0.64, 0.96,and 1.28%)were compared. The results showed that the optimum amount of CNF, 0.48% suspensions, added to PVAc increased the average lap joint strength (EN 205:2003) by 74.5% when compared to control specimens with pure PVAc. Correspondingly, 0.96% CNF suspensions also enhanced the strength of starch adhesive by 34.5%. Lower and higher CNF concentrations showed clearly inferior performance. (PDF) Effect of Cellulose Nanofibrils on the Bond Strength of Polyvinyl Acetate and Starch Adhesives for Wood

  • 278.
    Johansson, Amanda
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Granvirkes permeabilitet beroende av dess fysikaliska utformning och applicerat färgsystem2015Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    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.

  • 279.
    Johansson, Ingvar
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    Kungliga Tekniska Högskolan (KTH), Träteknologi.
    Plastisk deformation hos trä utsatt för varierande fuktbelastning: Förstudie1994Report (Other academic)
  • 280.
    Johansson, Jimmy
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Mechanical processing for improved products made from Swedish hardwood2008Doctoral thesis, comprehensive summary (Other academic)
    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.

  • 281.
    Johansson, Jimmy
    University of Kalmar, Department of Technology.
    The Swedish hardwood sawmill industry: Structure present status and development potential2008In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 3, no 3/4, p. 94-101Article in journal (Refereed)
    Abstract [en]

    This study describes the Swedish hardwood sawmill industry with respect to its structure, raw material, production and market conditions in order to seek ways of increasing the competitiveness of the industry. Fifteen sawmills were studied through observations and interviews. The Swedish hardwood sawmill industry creates job opportunities in sparsely populated areas and uses a biological raw material which is important for environmental biological diversity. Any decrease in the use of this material will mean a drop in the incentive for forest owners to cultivate deciduous forests. Today, the hardwood sawmill industry is experiencing problems in securing the supply of raw material of the desired quality, i.e. without knots and discoloured heartwood (red-heart or brown-heart). To increase the competitiveness of the Swedish hardwood sawmill industry, the raw material supply must be secured. Production should be geared towards products demanded by the market, and new markets need to be entered.

  • 282.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Blomqvist, Lars
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nilson, Henrietta
    Linnaeus University, School of Business and Economics, Department of Organisation and Entrepreneurship.
    Landscheidt, Steffen
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Influencing factors to enable automation of wood furniture production2016In: Proceedings of the 12th meeting of the Northern European Networkfor Wood Science and Engineering (WSE): Wood science andengineering – a key factor on the transition to Bioeconomy / [ed] Bruno Andersons and Arnis Kokorevics, Riga, Latvia: Latvian State Institute of Wood Chemistry , 2016, p. 208-213Conference paper (Refereed)
    Abstract [en]

    The wood furniture industry in Sweden has an identified need of technological development in order to stay competitive. Especially the necessity to focus on automation has been identified. In the industry there are often needs to handle large levels of customization at the same time as keeping the production effective. This requires flexible automation solutions, often described as automated equipment that can rapidly be reconfigured for new products.Before automated applications are implemented in an industry there are issues to solve related to organisational, human and technological aspects. Based on this, the project - Flexible automation in manufacturing of laminated veneer products was initiated. The project is running since January 1, 2016 and is a two year national Swedish project. The aim of the project is to investigate challenges concerning automation in the wood furniture industry and especially focusing on bended laminated veneer products.In the project a case-study with the aim of identifying factors important for successful automation implementation in an involved wood manufacturing industry was performed. Key persons and staff of the company were asked to tell their life stories and a process mapping of the production was conducted.The results indicate a problematic relation between the management and the production staff, which partly can be referred to the shift from a family business to a private owned firm. Based on the process mapping, internal transport and handling are identified improvement areas. Productivity is disturbed by stops caused by processing residues and poorly defined materials. There is potential for improvement by adapting a process-oriented approach and defining the materials used.The case–study confirms the need to consider organizational and human aspects in production before initiating production. The study concludes the need to consider the special aspects of the wood material in production development.

  • 283.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Blomqvist, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Challenges using dielectric heating for THM processing of solid wood2013In: Evaluation, processing and predicting of THM treated wood behaviour by experimental and numerical methods / [ed] Carmen-Mihaela Popescu and Maria-Cristina Popescu, Iasi, Romania, 2013, p. 55-56Conference paper (Refereed)
  • 284.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Salin, Jarl-Gunnar
    Application of percolation modelling on end-grain water absorption in aspen (Populus tremula L.)2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 3, p. 112-118Article in journal (Refereed)
  • 285.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Automatic sorting of sawn birch: Defect detection possibilities on sawn and planed wood surfaces2010In: Hardwood research and utilisation in Europe: New Challanges / [ed] Robert Nemeth and Alfred Teischinger, Sopron: University of West Hungary Press , 2010, p. 206-213Conference paper (Refereed)
    Abstract [en]

    In the production of sawn hardwood a critical processing step is the quality grading. The grading has normally been handled manually in the hardwood sawmills. The process has been labour intensive and a problematic working environment. With the help from existing scanning technology it is possible to automate the process with several benefits as a result. These are e.g. a decreased need of labour, a better working environment and the possibility to use more complicated grading rules. Thereby the wood could be used in a more optimal way with both cost and environmental benefits.

    One problem when grading hardwood is that camera and laser based scanning technology has mainly been used on planed surfaces. Normally the quality grading in hardwood sawmills is performed before planing. The wood may then be cross-cutted to components before planing in order to minimise the volume losses because of deformations of the wood pieces.

    In order to investigate the possibilities to scan the sawn wood before planing rip-sawn birch boards (Betula pubescens Ehrh., Betula pendula Roth.) was scanned before and after planing the wood. The used scanner was a commercial system for automatic sorting of wood. Before the scanning it was estimated that the sawn surfaces exposed to the surrounding environment during drying would not generate any usable results from the scanning. Therefore only the two rip-sawn surfaces were used for evaluation before and after planing. The evaluation was made by comparing the results from the quality grading before and after the planing based on grading rules used by Swedish hardwood sawmill. The results show that there are possibilities to grade the birch wood before planing. The study, however, shows that the scanner has difficulties in detecting small colour variations as brown streaks and fresh knots. It is also difficult to detect fibre angle deviations because of loose fibres on the sawn surface. The possibilities to scan the birch wood are thereby related to the grading rules, i.e. if the mentioned quality parameters are allowed or not.

  • 286.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Luleå University of Technology.
    Integrated use of product data for improved wood material utilization in the furniture and joinery production2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 321-327Article in journal (Refereed)
    Abstract [en]

    Quality communication from customer to supplier is crucial for the effectiveness of a value chain. In the forest products industry, a mutual understanding of quality requirements between customer and supplier in relation to material characteristics and production conditions is important if the material is to be utilized effectively.

     

    In the mechanical wood industry, hardwood has normally been quality graded manually. This has been a work-intensive operation and a problematic working environment. Automatic grading equipment based mainly on camera and laser technology is therefore gradually replacing the manual grading operation which relies on the human eye. The cross-cutting of sawn wood into shorter components with well-defined quality parameters is a process which needs to be automated. This makes it possible for the sawmill to redefine the quality grading process with e.g. more complex grading rules. To gain full benefits from the new technology, however, the grading process must be redefined in cooperation with the customers. There is also an expressed need for tools to communicate the quality of products produced by sawmills.

     

    In this study, three case studies were therefore performed where the communication of requirements between sawmills and customers was studied with regard to three different components delivered from two sawmills. In one sawmill, two products were studied; one intended for a furniture producer and one for a joinery producer. In the other sawmill, the studied product was intended for a producer of solid wood panels. The idea has been to study the need for product information expressed by both the customer and supplier through the automatic grading process and to utilise this equipment for data collection and visualisation.

     

    The requirements for a communication and data exchange tool have been derived. There is often an expressed need to measure how different raw materials affect the volume yield in a process and how different quality requirements affect the volume yield. Sharing this information between customer and supplier has been shown to yield a mutual understanding of how and why deviations occur. Visualisation possibilities are a prerequisite for a mutual understanding of quality conceptions.

  • 287.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Ny träteknik höjer värdet på lövskogen2008In: Ekbladet, ISSN 0283-4839, no 23, p. 24-27Article in journal (Other academic)
    Abstract [sv]

    Lövträ är ett uppskattat material i möbler, snickerier och inredningar samtidigt som en stor del av det svenska lövträet av olika anledningar inte utnyttjas för dessa användningsområden. Endast ca. 5 % av den totala volymen lövträ som årligen avverkas blir sågat virke. Motsvarande siffra för furu och gran är 50 %. Istället importeras den största delen av råvaran, men bakom knuten väntar nya spännande nyheter, vilka är ett  resultat av forskningen vid Växjö universitets avdelning för Skog & Trä.

  • 288.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Preparation of wood with pulsed UV-laser ablation for characterisation of the wood structure2007In: Proceedings of Third International Symposium on Wood Machining, Presses polytechniques et universitaires romandes , 2007, p. 191-194Conference paper (Refereed)
    Abstract [en]

    In contrast to mechanical techniques involving cutting with a knife, cutting with a microtome or grinding, pulsed UV-laser ablation is an irradiation technique where a so-called Excimer laser is used, and the process is adiabatic, which means that no or a very little chemical change occurs in the material being processed. Cross sections of samples of Scots pine and Norway spruce which had been exposed outdoors have been prepared with the help of an Excimer laser (wavelength 248 nm) for study in a microscope. UV-laser ablation has been found to be a suitable method of preparation for wood when it is desired to obtain thin sections with little influence on the material, and particularly when dealing with brittle materials, e.g. archaeological wood, biologically-attacked wood or, as in this case, wood which has been exposed outdoors.

  • 289.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    The Concept of Value Activation II.: The PrimWood Method for improved properties of hardwood products.2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 53-59Conference paper (Refereed)
    Abstract [en]

    The name Value activation refers to the basic understanding of wood, where at present there are properties that are not fully exploited, but with help of a new sawing pattern could be fully utilized. The basic idea lies at an industrial level producing radial sawn timber with good profitability and with lesser and mostly a controllable moisture movement. In short it implies an activation of values of timber that has not been exploited in ordinary industrial production to date.

    This paper gives one example how the basic ideas in the concept of Value activation can be implemented in the industry. A new manufacturing system, the PrimWood Method, producing radial sawn timber, well adjusted to the conditions of the Swedish hardwood sawmill industry is presented. The manufacturing system generates knot and defect-free hardwood products with vertical annual rings.

    Utilizing the proposed manufacturing system in the Swedish hardwood sawmill industry imply an increased focus on hardwood in consumer products, which gain both forestry, sawmill industry and the wood manufacturing industry.

  • 290.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Volymutbyte vid tillverkning av kvistfria snickeriämnen och skivor med stående årsringar2005Report (Other academic)
    Abstract [en]

    This report describes a new production concept for manufacturing of high quality boards, components and panels from softwoods and hardwoods. The concept, named the PrimWood Method generates knot-free boards, components and panels with vertical annual rings. The cross sections of the boards are either rectangular or triangular, called Triangle and Rectangle. These two products are further processed to components and panels.

    The PrimWood Method increases the quality of the wood, compared to wood processed with traditional methods (harder surface, increased shape stability, freedom from cracks, easier and faster processing, less waste and a more even finishing). The wood is also given new aesthetical characteristics (e.g. even texture, knot-free surfaces and decorative finger-joints). The PrimWood Method also improves the raw material utilization, with resulting positive environmental effects, since a renewable resource is utilized more efficiently.

    The volume yield when manufacturing different products from the PrimWood Method has in this report been studied, both theoretical and experimental during industrial conditions. For pine (Pinus sylvéstris L.) the volume exchange in different processing stages may be summarized as follows:

    Sawing, from log to dried wood             56 %

    Knot-free boards from Rectangle           75 %

    Knot-free panels from Rectangle (Panel) 52 %

    Knot-free boards from Triangle (Rhomb) 73 %

    Knot-free panels from Triangle (Prism)   53 %

    The volume yield for boards and panels are determined from incoming volume sawn and dried Rectangle and Triangle. The quality and the geometrical form of the raw material are crucial for the obtained volume yield from the manufacturing process. The volume yields described above are to be seen as guiding values, when processing pine from Sweden.

  • 291.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Gustafsson, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Design of form stable and visually crack free edge-glued oak panels.2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 167-171Conference paper (Refereed)
    Abstract [en]

    Edge-glued panels are a very appreciated material, for instance used in cabinet doors or worktops in the kitchen. The surrounding climate for these products is often severe, due to large seasonal variation of the relative humidity in the indoor air. Therefore problems regarding crack formation and form stability often occurs. This paper studies how annual ring orientation of lamellas, lamella width, initial different moisture content in the panels and single lamellas with deviating moisture content are affecting form stability and crack formation of edge-glued oak panels (Quercus robur).

    In the study 47 test samples with different characteristics were tested in varying climate during 182 days. The relative humidity was changed approximately every 14 days in the interval 18 to 88 % and temperature 20˚C. The panels were measured each 7 days regarding form stability factors. The crack formation was measured at the beginning and the end of the test.

    The evaluation of the results show that the annual ring orientation of the lamellas will be a significant factor regarding the form stability factors width changes and cupping of the panels and also regarding the crack formation. The lamella width is important as a significant factor regarding the surface evenness. Moisture content (initial level) will affect both the form stability and the crack formation. The effect of this factor is dependent on the relation to the climate of the surroundings.

  • 292.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Gustafsson, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Secondary interior wood products for manufacturing in Swedish hardwood sawmills2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 162-166Conference paper (Refereed)
    Abstract [en]

    The Swedish hardwood sawmill industry is today in a situation where the sawn hardwood exhibit a wide variation in quality characteristics, while the customers places strict demands. To create a profitable return for all their products the hardwood sawmill industry therefore must find new markets where other quality characteristics are valuable.

    In this study the requirements regarding logistic service and product quality characteristics for secondary wood products used as for instance indoor panelling and mouldings are identified and described. The industrial setting for the study is the Swedish retail and house building industry. The purpose of the study was to study the possibilities to increase the use of hardwoods in these products.

    The study follows a case study methodology. The studied companies consisted of in total nine companies in the southern part of Sweden. Six house-building companies were studied and three retail companies.

    A total of 15 different requirements regarding logistic service and product quality characteristics were identified. The product quality characteristics were related mainly to the aesthetic appearance of the products and to the stability of the product in service. The important logistical service requirements were related to the location and time of delivery and customer-specified orders.

    The results show that adjustment to customer requirements means that a supplier of hardwood products must adjust its organization towards a stronger customer focus. In order to do this a fundamental problem for Swedish hardwood sawmills is the current lack of an accepted quality sorting system for hardwood. It is also important for sawmills to control and adjust their production processes in order to gain increased flexibility and delivery precision.

    With the results from this study a test collection of mouldings and indoor panelling has been developed by a Swedish hardwood sawmill and is now tested by one of the retail companies within the study.

  • 293.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Söderström, Ove
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Capillarity in hardwood: An important factor for hardwood market expansion2007In: The Beauty of Hardwood: Proceedings of third Conference on Hardwood Research and utilisation in Europe, University of West Hungary, Sopron , 2007Conference paper (Refereed)
    Abstract [en]

    The Swedish hardwood sawmills are today experiencing problems of finding profitable markets for products containing for instance knots and red or brown heartwood. By using hardwood outdoors, it would be possible to expand the market of hardwood with new products that may set other requirements on the wood than the present use. In Sweden today, hardwood is normally used in furniture, joinery, floors and kitchens where esthetical requirements are dominant. When considering outdoor use, technical requirements such as durability become more important and especially the capillary characteristics of the wood are of interest. The capillarity determines the ability of the material to absorb and desorb moisture, characteristics that affect the resistance of degrading. 

    In this paper, the capillary characteristics were modelled and studied by exposing the cross section of wood to a free water surface. The study compares two Swedish hardwood species, aspen and oak with pine, a softwood species that is common in Sweden and often used outdoors.

    The results show that the capillary transport mechanism is affected by the microstructure of the wood and the natural ability of the material to close the transport paths in the structure with for instance extractives, tyloses and closed pits. Based on these factors, a characteristic capillary mean radius is introduced to describe the longitudinal capillary water absorption in the studied wood species.

  • 294.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Woxblom, Lotta
    Sveriges lantbruksuniversitet.
    Prerequisites for the Realization of the Transnational Communication Platform WoodApps.2013In: Proceeding of ISCHP2013 - International Scientific Conference on Hardwood Processing, October 7-9, Florence, Italy., 2013Conference paper (Other academic)
  • 295.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Grading of sawn timber with dynamic methods – influence of defects2009In: Proceedings of the COST E53 Workshop, Lisbon 22-23 October 2009 / [ed] José António Santos, 2009Conference paper (Other academic)
  • 296.
    Johansson, Marie
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Ormarsson, Sigurdur
    Technical University of Denmark.
    Influence of growth stresses and material properties on distortion of sawn timber – Numerical investigation.2009In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 66, no 6, article id 604Article in journal (Refereed)
  • 297.
    Johansson, Martin
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Hårdgörning av Asp2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    To make wood harder it can be densified. This can be achieved by compression, the compressed material tends to return to the original shape when it is exposed to moisture fluxations and if no form of fixation occurs. The fixation can be done mechanically in a three-layer panel construction which reduce movements in the timber. These panels have been found to be unstable and previous attempts have shown deformations in form of cupping. This study aims to evaluate the conditions for using compressed aspen wood, and to provide a basis for development of a commercial product.

    Practical tests have been conducted to study hardness, springback and density of the compressed wood. In addition, three-layer panels have been developed to test whether it is possible to have a stable construction by varying the thickness of the buttom layer. Differences in acclimatisation time and the moisture contents effect on the springback has aslo been studied.

    The results show that the hardness of aspen wood after compression is in equal levels with beech and ashes, a low moisture contet provides a low springback, compressed timber have a longer time for acclimatisation and it is possible to fixate the material in the direction across the grain in a three-layer panel construction.

  • 298.
    Jones, Grace
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Liziniewicz, Mateusz
    Swedish Forestry Research Institute, Sweden.
    Lindeberg, Johan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Nondestructive wood density testing in downy birch and silver birch genetics field trial, southern Sweden2019In: 21st International Nondestructive Testing and Evaluation of Wood Symposium,: Freiburg, Germany, 2019 / [ed] Wang, Xiping; Sauter, Udo H.; Ross, Robert J.,, U.S. Department of Agriculture (USDA) , 2019, p. 79-86Conference paper (Refereed)
    Abstract [en]

    Non-destructive testing of wood density, as is already done for Eucalyptus, can allow for earlyselection of birch trees for breeding programmes and stands for harvesting. In this work, external stemquality traits were visually assessed in a family trial of downy (Betula pendula) and silver (B.pubescens) birch in southern Sweden. A subsample of trees was measured for wood density using thePilodyn resistometer portable NDT tool. An X-ray microdensitometric analysis of the subsample oftrees was completed using the Itrax X-ray machine for increment cores taken from the south face,through the pith to the north bark at 1.3 m stem height. The Pearson’s r value for Itrax density andPilodyn density was high (0.580 for downy birch and 0.795 for silver birch), and this correlationmeans Pilodyn should provide a good estimate of average birch wood density. Neither species hadstable wood density values at age 13 and both species’ density increased over time from pith to bark.Ring width influence on stem density was minor or non-existant, and may vary between birch species

  • 299.
    Josef, Füssl
    et al.
    Technische Univerität, Austria.
    Bader, Thomas K.Linnaeus University, Faculty of Technology, Department of Building Technology.Josef, EberhardsteinerTechnische Univerität, Austria.
    CompWood 2017 - Computational Methods in Wood Mechanics - From Material Properties to Timber Structures: Programme & Book of Abstracts2017Conference proceedings (editor) (Refereed)
  • 300. Jäger, Andreas
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Eberhardsteiner, Josef
    Identification of Elastic Properties of Wood Cell Walls by Means of Nanoindentation2009In: 26th Danubia-Adria Symposium on Advances in Experimental Mechanics, Leoben, Austria, 2009, p. 83-84Conference paper (Other academic)
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