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  • 1.
    Amiandamhen, Stephen O.
    et al.
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University, Lückligs Plats 1, Växjö 35195 Sweden.
    Kumar, Anuj
    Natural Resources Institute Finland (Luke), Production Systems, Tietotie 2, Espoo 02150 Finland.
    Adamopoulos, Stergios
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University, Lückligs Plats 1, Växjö 35195 Sweden.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Faculty of Forestry and Wood Sciences, Czech University of Life sciences Prague, Kamýcká 129, 165 21 Praha 6 – Suchdol, Czech Republic.
    Nilsson, Bengt
    Department of Forestry and Wood Technology, Faculty of Technology, Linnaeus University, Lückligs Plats 1, Växjö 35195 Sweden.
    Bioenergy production and utilization in different sectors in Sweden: A state of the art review2020In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 15, no 4, p. 9834-9857Article, review/survey (Refereed)
    Abstract [en]

    In the continual desire to reduce the environmental footprints of human activities, research efforts to provide cleaner energy is increasingly becoming vital. The effect of climate change on present and future existence, sustainable processes, and utilizations of renewable resources have been active topics within international discourse. In order to reduce the greenhouse gases emissions from traditional materials and processes, there has been a shift to more environmental friendly alternatives. The conversion of biomass to bioenergy, including biofuels has been considered to contribute to the future of climate change mitigation, although there are concerns about carbon balance from forest utilization. Bioenergy accounts for more than one-third of all energy used in Sweden and biomass has provided about 60% of the fuel for district heating. Apart from heat and electricity supply, the transport sector, with about 30% of global energy use, has a significant role in a sustainable bioenergy system. This review presents the state of the art in the Swedish bioenergy sector based on literature and Swedish Energy Agency’s current statistics. The review also discusses the overall bioenergy production and utilization in different sectors in Sweden. The current potential, challenges, and environmental considerations of bioenergy production are also discussed.

  • 2.
    Bachtiar, Erik Valetine
    et al.
    Fraunhofer-Institut für Holzforschung, Wilhelm-Klauditz-Institut WKI, Braunschweig, Germany.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. ETH Zürich, Institute for Building Materials, Zürich, Switzerland; Department of Forestry and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Forestry and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Properties of adhesive films used in cultural assets2022In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, no 2, p. 147-150Article in journal (Refereed)
    Abstract [en]

    The hygroscopic nature of wood leads to large moisture fluctuations in the material that may influence the mechanical performance of glued wood products. Adhesives based on bone, fish and hide have a long tradition for the gluing of wood and can be found in wooden structures in our cultural heritage. In this study, selected sorptive and mechanical properties of animal adhesives have been compiled and compared to those of synthetic polyurethane adhesives. Bone, fish and hide adhesives show a high moisture uptake at high relative humidity, which confirms the low moisture resistance of such adhesives. The modulus of elasticity and ultimate tensile strength of the films based on animal adhesives are considerably reduced when the moisture content is increased.

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  • 3.
    Bekhta, Pavlo
    et al.
    Ukranian National Forestry University.
    Sedliacik, Jan
    Technical University in Zvolen.
    Jones, Dennis
    DJ Timber Consultancy Ltd.
    Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 2, p. 549-562Article in journal (Refereed)
    Abstract [en]

    In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 ⁰C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 minute before being adhesive applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa that was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from un-compressed veneer. The findings in this study indicated that compression of birch veneer would be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.

  • 4.
    Berg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Turesson, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ekevad, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Huber, Johannes Albert Josef
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Finite element analysis of bending stiffness for cross-laminated timber with varying board width2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 392-403Article in journal (Refereed)
    Abstract [en]

    ross laminated timber (CLT) is a wood panelling building system that is used in construction, e.g. for floors, walls and beams. Because of the increased use of CLT, it is important to have accurate simulation models. CLT systems are simulated with one-dimensional and two-dimensional (2D) methods because they are fast and deliver practical results. However, because non-edge-glued panels cannot be modelled under 2D, these results may differ from more accurate calculations in three dimensions (3D). In this investigation, CLT panels with different width-to-thickness ratios for the boards have been simulated using the finite element method. The size of the CLT-panels was 3.0 m × 3.9 m and they had three and five laminate layers oriented 0°–90°–0° and 0°–90°–0°–90°–0°. The thicknesses of the boards were 33.33, 40.0, and 46.5 mm. The CLT panel deformation was compared by using a distributed out-of-plane load. Results showed that panels with narrow boards were less stiff than wide boards for the four-sided support setup. The results also showed that 2D models underestimate the displacement when compared to 3D models. By adjusting the stiffness factor k88, the 2D model displacement became more comparable to the 3D model.

  • 5.
    Bernaczyk, Arkadiusz
    et al.
    Jowat SE, Detmold, 32758, Germany.
    Wagenführ, André
    Institute of Natural Materials Technology, Technische Universität Dresden, Dresden, 01062, Germany.
    Terfloth, Christian
    Jowat SE, Detmold, 32758, Germany.
    Lincke, Jörg
    Jowat SE, Detmold, 32758, Germany.
    Krystofiak, Tomasz
    Department of Wood Science and Thermal Techniques, Poznań University of Life Sciences, Poznan, 60-627, Poland.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Institute for Building Materials, ETH Zurich, 971 87 Luleå, Sweden.
    Investigations into the Influence of Temperature on the Tensile Shear Strength of Various Adhesives2023In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 16, no 18, article id 6173Article in journal (Refereed)
    Abstract [en]

    The temperature resistance of glued timber, which is crucial for glued wood construction, represents a significant assessment criterion. To gain insights into this aspect, this study utilized methods such as a shear strength test in accordance with EN 302-1:2013-06 under thermal loading (from 20 °C to 200 °C), and Differential Scanning Calorimetry (DSC) to determine the glass transition temperature (Tg). An increase in thermal load resulted in a decrease in shear strength and an increase in wood breakage. A hierarchy of adhesive groups was established based on strength performance and wood failure percentage (WFP) at 200 °C. Thermoset adhesives (MF: Melamine Formaldehyde, PRF: Phenol Resorcinol Formaldehyde) led the ranking, followed by elastomer adhesives (1C-PUR: One-Component Polyurethane, EPI: Emulsion Polymer Isocyanate), with thermoplastic adhesive (PVAc: Polyvinyl Acetate) last. Thermoset adhesives further cured under heat. PUR adhesives exhibited higher strength performance at 150 °C and lower temperatures.

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  • 6.
    Bernaczyk, Arkadiusz
    et al.
    Jowat SE, 32758 Detmold, Germany.
    Wagenführ, André
    Institute of Natural Materials Technology, Technische Universität Dresden, 01062 Dresden, Germany.
    Zboray, Robert
    Center for X-ray Analytics, Empa—Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
    Flisch, Alexander
    Institute of Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.
    Lüthi, Thomas
    Center for X-ray Analytics, Empa—Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland.
    Vetter, Birgit
    Institute of Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.
    Rentsch, Mario
    Institute of Materials Science, Technische Universität Dresden, 01062 Dresden, Germany.
    Terfloth, Christian
    Jowat SE, 32758 Detmold, Germany.
    Lincke, Jörg
    Jowat SE, 32758 Detmold, Germany.
    Krystofiak, Tomasz
    Department of Wood Science and Thermal Techniques, Poznań University of Life Sciences, 60-627 Poznan, Poland.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Investigations on the Characterization of Various Adhesive Joints by Means of Nanoindentation and Computer Tomography2022In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 15, no 23, p. 8604-8604Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of cured wood adhesive films were tested in a dry state by means of nanoindentation. These studies have found that the application of adhesives have an effect on the accuracy of the hardness and elastic modulus determination. The highest values of hardness among the tested adhesives at 20 °C have condensation resins: MF (0.64 GPa) and RPF (0.52 GPa). Then the decreasing EPI (0.43 GPa), PUR (0.23 GPa) and PVAc (0.14 GPa) adhesives. The values of the elastic modulus look a little bit different. The highest values among the tested adhesives at 20 °C have EPI (11.97 GPa), followed by MF (10.54 GPa), RPF (7.98 GPa), PVAc (4.71 GPa) and PUR (3.37 GPa). X-ray micro-computed tomography was used to evaluate the adhesive joint by the determination of the voids. It has been proven that this value depends on the type of adhesive, glue quantity and reactivity. The highest values of the void ratio achieve the PUR (17.26%) adhesives, then PVAc (13.97%), RRF (6.88%), MF (1.78%) and EPI (0.03%). The ratio of the gaps increases with the higher joint thickness. A too high proportion of voids may weaken the adhesive joint.

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  • 7.
    Blomqvist, Lars
    et al.
    Linnӕus University, Department of Building Technology, Växjö, Sweden. RISE, Research Institute of Sweden.
    Berg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Wood Processing and Biomaterials, Czech University of Life Sciences Prague, Prague, Czech Republic.
    Distortion in laminated veneer products exposed to relative-humidity variations: Experimental studies and finite-element modelling2019In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 14, no 2, p. 3768-3779Article in journal (Refereed)
    Abstract [en]

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

  • 8.
    Buck, Dietrich
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cross-Laminated Timber Mechanics2021Doctoral thesis, comprehensive summary (Other academic)
  • 9.
    Buck, Dietrich
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate Image Analysis Applied to Cross-Laminated Timber: Combined Hyperspectral Near-Infrared and X-ray Computed Tomography2023In: Journal of Spectroscopy, ISSN 2314-4920, E-ISSN 2314-4939, article id 3954368Article in journal (Refereed)
    Abstract [en]

    Engineered wood products, such as cross-laminated timber (CLT), are becoming more popular in the designs of modern sustainable buildings. This increased production of CLT requires more robust, yet less labour-intensive means to assess the material characteristics of whole CLT panels. In exploring ways of improving efficiency, this study explores multivariate image analysis (MIA) via partial least squares discriminant analysis (PLS-DA) machine learning as a means to classify CLT material features. CLT panels underwent nondestructive testing using near-infrared (NIR) hyperspectral imaging and X-ray computed tomography (CT) analysis. MIA was performed on these results to build predictive models for wood features, such as fibre alignment and knot type. The models showed that it was possible to classify material features on the surface of CLT using NIR alone; whilst when combined with X-ray data, it enhanced the predictive ability of material features throughout the CLT volume. These first results from such modelling have the potential to help map the chemical and physical material properties of CLT, improving the manufacturing efficiency of the product and allowing greater sustainability of engineered wood products.

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  • 10.
    Buck, Dietrich
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Wallentén, Petter
    Division of Building Physics, Department of Building and Environmental Technology, Lund University, Lund, Sweden.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Moisture- and mould-resistance: multi-modal modelling leveraging X-ray tomography in edge-sealed cross-laminated timber2023In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 230, article id 111967Article in journal (Refereed)
    Abstract [en]

    Edge-sealing, which involves treating the edges of wood products, improves water resistance. This study investigated the feasibility of edge-sealed cross-laminated timber (CLT) panels to reduce capillary water uptake, thereby resisting mould formation. The water and vapour permeabilities of ten characteristically different single-layer sealant coating systems were systematically determined. Multi-modal assessment leveraged by computed tomography (CT) scanning methodology was used to enhance detection of material characteristics beyond the standard coating permeability assessment. Moisture content was observed to change during the specimens’ absorption and desorption depending on the sealant system applied. The results revealed different characteristics of coatings during the water absorption and desorption stages. Findings from this study were used to develop recommendations regarding the water resistance of coating systems, curing time, susceptibility to mould formation, and industrial applicability. Results suggest that edge-sealed CLT could minimise the risk of mould formation, which can occur at worksites with minimal weather protection. The method developed in this study provides a basis to evaluate new coating systems and determine which use case is the best for a particular coating type. This study also incorporates insights from industry to identify future research orientations, which may pave the way for new designs and assessment techniques.

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  • 11.
    Báder, Mátyás
    et al.
    University of Sopron, Sopron, Hungary.
    Bak, Miklós
    University of Sopron, Sopron, Hungary.
    Németh, Róbert
    University of Sopron, Sopron, Hungary.
    Rademacher, Peter
    Mendel University in Brno, Brno, Czech Republic.
    Rousek, Radim
    Mendel University in Brno, Brno, Czech Republic.
    Horníček, Stanislav
    Mendel University in Brno, Brno, Czech Republic.
    Dömény, Jakub
    Mendel University in Brno, Brno, Czech Republic.
    Klímek, Petr
    Mendel University in Brno, Brno, Czech Republic.
    Kudela, Jozef
    Technical University in Zvolen, Zvolen, Slovakia.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Neyses, Benedikt
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Kutnar, Andreja
    University of Primorska, Koper, Slovenia; InnoRenew CoE, Izola, Slovenia.
    Wimmer, Rupert
    University of Natural Resources and Life Sciences, Vienna, Austria; Renewable Materials, Tulln an der Donau, Austria.
    Pfriem, Alexander
    Eberswalde University for Sustainable Development, Eberswalde, Germany.
    Wood densification processing for newly engineered materials2018In: Proceedings of the 5th International Conference on Processing Technologies for the Forest and Bio-based Products Industries (PTF BPI 2018), Freising/Münich, September 20-21 / [ed] M. C. Barbu; A. Petutschnigg; E. M. Tudor, Kuchl, 2018, p. 255-263Conference paper (Refereed)
    Abstract [en]

    Wood is a renewable, bio-based material with a mixture of different properties and qualities, used in numerous applications. Beside many species with high wood qualities several species suffer due to a number of disadvantages, where low hardness and abrasive resistance are characteristic for low-density species. This paper presents examples of on-going European research projects and industrial processes mostly related to wood densification methods. Wood densification is a classical thermohydro-mechanical (THM) wood treatment process, through which density is increased by mechanical compression of wood perpendicular to the grain, by impregnation of cell lumens or cell walls with solutions or melted substances (resins, waxes), or by a combination of both. The purpose is to produce newly designed and engineered materials and products with new property profiles, which would potentially find new markets. In general, the THM processes consist of three stages: plasticization of the wood cells, followed by the actualcompression, and finally solidification of the compressed wood in order to prevent elastic spring-back and the moisture-induced set-recovery. The wood densification process refers but is not limited to solid wood and might apply to whole wood pieces, or to local areas within given pieces only. Another THM method is the mechanical compression of wood parallel to the grain, which leads to a product with high flexibility. A European wood research network, represented by the authors of this contribution, has extended experience in many wood modification processes, as demonstrated through ongoing researches and case studies in this paper

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  • 12.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in coarse resolution CT images of logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    The use of X-ray computed tomography (CT) scanning of logs in sawmill is becoming a reality in the last few years, usually with rather costly and complex machines resembling medical scanners. However, a scanning solution has been developed that is less costly and more robust, and therefore more suited for sawmill needs. The rather coarse data from this machine has not been fully evaluated regarding possibilities to detect internal features such as knots. In this study, a knot detection algorithm developed for medical scanners was applied to images from a coarse resolution scanner, from four different logs of various species, and with different image resolution. The objective was to see if it was possible to detect knots automatically in the images. If so, the aim was to calculate the knot detection rate and the accuracy of detected knot size and position. These numbers were calculated compared to manually measured reference knots. This resulted in a knot detection rate of about 53 % overall, and a well detected knot position, but poorly detected knot size. It is possible to observe a certain difference between species and reconstruction resolution, however the material is too small to draw any definite conclusions. As a preliminary study, it provides input for further investigation on knot detection in coarse resolution X-ray CT images. Future work involves scanning more logs to get more data, and to pinpoint the resolution needed for accurate knot detection using the current algorithm.

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  • 13.
    Cool, Julie
    et al.
    University of British Columbia.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stephen, James D
    Queen’s University.
    Mabee, Warren E
    Queen’s University.
    Avramidis, Stavros
    University of British Columbia.
    Bull, Gary Q
    University of British Columbia.
    An Integrated Forest Products Cluster for Off-Grid Lumber Production Using Biomass CHP in Remote Indigenous Communities2017Conference paper (Refereed)
  • 14.
    Couceiro, José
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    X-ray computed tomography to study moisture distribution in wood2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    X-ray computed tomography (CT) has been used as an analysing tool for different features in wood research since the beginning of the1980s, but it can also be used to study wood-water interactions in different ways, such as by determining wood moisture content (MC). The determination of wood MC with CT requires two CT images: one at the unknown moisture distribution and a second one at a known reference MC level, usually at oven-dry condition. The two scans are then compared, and the MC is calculated based on the differences between the images. If the goal is to determine the MC in local regions within the wood volume, e.g. when studying moisture gradients in wood drying, wood shrinkage must be taken into account during the data processing of the images. The anisotropy of wood shrinkage creates an obstacle, however, since the shrinkage is not uniform throughout the wood specimen. The technique is thus limited in two ways: it cannot measure MC in local regions and it cannot do it in real time.

    The objective of this thesis was to study methods to overcome these two limitations. The work explores up to three different methods to estimate local MC from CT images in real time. The first method determines shrinkage for each pixel using digital image correlation (DIC) and is embedded in a broader method to estimate the MC, which verified against a reference. It involves several steps in different pieces of software, making it time-consuming and creating many sources of possible experimental errors. The determination of shrinkage within this method is further explored to enable the implementation of all steps in a unique piece of software. It is shown that it is possible to calculate MC through this method with a root mean square error of prediction of 1.4 percentage points for MC between 6 and 25%.

    The second method studied succeeds in determining the MC distribution in research applied to wood drying, but the calculation of shrinkage differs from the previous method: instead of calculating shrinkage in the radial and tangential directions, it does so by using the displacement information generated from the spatial alignment of the CT images. Results show that the algorithm can provide consistent data of internal MC distribution of wood at the pixel level that entail continuing researching wood drying processes with an improvement in the accuracy of the MC determination. It represents an improvement regarding the first method because the calculation is fast and highly automatized in a single piece of software.

    The third method studied is the application of dual energy CT (DECT) to moisture. DECT would provide means for MC calculation at the pixel level and, potentially, in real time, which would mean an important breakthrough in wood drying research. Previous research shows promising results, but its implementation in medical CT, the tool used throughout this work, has shown poor predicting ability. Nevertheless, further research is encouraged.

    The work done in this thesis proves that it is possible to measure local distribution of MC in wood using CT with accuracy and precision. It also shows that further research could potentially provide a means for MC estimation in real time.

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  • 15.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Faculty of Engineering, Norwegian University of Science and Technology, 6025 Ålesund, Norway.
    Mannes, David
    Paul Scherrer Insitute (PSI), Villigen, Switzerland.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. ETH Zürich, Institute for Building Materials, Stefano-Franscini Platz 3, 8093 Zürich, Switzerland.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Estimation of the moisture content in wood by combination of Neutron and X-ray imaging2022In: Proceedings: 22nd International Nondestructive Testing and Evaluation of Wood Symposium / [ed] Wang, X., Ross, R.J., Madison (WI), USA: United States Department of Agriculture , 2022, p. 40-47Conference paper (Other academic)
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  • 16.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Faculty of Engineering, Norwegian University of Science and Technology, 6025 Ålesund, Norway.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Ursella, Enrico
    MicroTec GmbH, Venice, Italy.
    Industrial CT scanning in wood research2022In: Proceedings: 22nd International Nondestructive Testing and Evaluation of Wood Symposium / [ed] Wang, X., Ross, R.J., Madison (WI), USA: United States Department of Agriculture , 2022, p. 17-17Conference paper (Other academic)
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  • 17.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lin, Chia-feng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Schleicher, Frank
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Svensson, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Mantanis, George I.
    Laboratory of Wood Science and Technology, Department of Forestry, Wood Sciences and Design, University of Thessaly, Karditsa, Greece.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Use of X-ray computed tomography for real-time studies of the fire progress in wood2023In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
  • 18.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Estimation of miosture content in wood using dual x-ray energies in a medical CT-scanner2016In: Process Technologies for the Forest & Biobased Products Industries: PTF BPI 2016, 2016, p. 22-Conference paper (Other academic)
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  • 19.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Lindgren, Owe
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Norwegian University of Science and Technology (NTNU), Ålesund, Norway.
    Söderström, Ove
    c Professor Emeritus of Building Materials, Stockholm, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Real-time wood moisture-content determination using dual-energy X-ray computed tomography scanning2019In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 14, no 6, p. 437-444Article in journal (Refereed)
    Abstract [en]

    The estimation of the pixel-wise distribution of the moisture content (MC) in wood using X-ray computed tomography (CT) requires two scans of the same wood specimen at different MCs, one of which is known. Image-processing algorithms are needed to compensate for the anisotropic distortion that wood undergoes as it dries. An alternative technique based on dual-energy CT (DECT) to determine MC in wood has been suggested by several authors. The purpose of the present study was to evaluate the hypothesis that DECT can be used for the determination of MC in real time. A method based on the use of the quotient between the linear attenuation coefficients (μ) at different acceleration voltages (the so-called quotient method) was used. A statistical model was created to estimate the MC in solid sapwood of Scots pine, Norway spruce and brittle willow. The results show a regression model with R2 > 0.97 that can predict the MC in these species with a RMSE of prediction of 0.07, 0.04 and 0.11 (MC in decimal format) respectively and at MC levels ranging from the green to the totally dry condition. Individual measurements of MC show an uncertainty of up to ±0.4. It is concluded that under the conditions prevailing in this study, and in studies referred to in this paper, it is not possible to measure MC with DECT.

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  • 20.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Neyses, Benedikt
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    In-situ moisture content and density measurements in surface densified wood using dual X-ray absorptiometry in medical CT-scanning2016In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium, Bio-based composites for a sustainable future., Concepción: University of Concepción , 2016, Vol. 2, p. 92-, article id NA01Conference paper (Refereed)
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  • 21.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of X-ray computed tomography in bio-composite research2016In: BIOCOMP 2016: The 13th Pacific Rim Bio-Based Composites Symposium : Bio-based composites for a sustainable future,, Conceptión: University of Concepción , 2016, p. 42-45Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography (CT), which was introduced in the medical field in the early 1970s, is also a powerful tool for the non-destructive measurement of dynamic processes in wood. For more than 20 years, medical CT has been used in wood research at Luleå University of Technology. The uniqueness of the CT equipment allowsprocesses such as drying, modification; water absorption; internal and external cracking; and material deformation to be studied in temperature- and humidity-controlled environments. The data recorded by the CT scanner during the process is converted into two or three dimensional images that, for instance, can show dynamic moisture behaviour in wood drying and crack formation. This paper provides an overview of the possibilities of using CT in bio-composite research, and shows examples of applications and results that can be particularly difficult to achieve using other methods. A specific focus is on studies on wood products that use combinations with materials such as metal and especially about how to deal with the difficulties that this entails.The practical application of the result is that CT scanning, combined with image processing, can be used for non-destructive and non-contact three-dimensional s tudies of exterior construction elements during water sorption and desorption, to study parameters such as swelling and shrinking behaviour; delamination phenomena; and crack development.

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  • 22.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    X-ray computed tomography studies of moisture-content distribution in spruce boards exposed to liquid water.2020In: Proceedings of the 2020 Society of Wood Science and Technology International Convention: “Renewable Resources for a Sustainable and Healthy Future” / [ed] Susan LeVan Green, USA: Society of Wood Science and Technology (SWST) , 2020, p. 356-357Conference paper (Refereed)
    Abstract [en]

    The use of cross-laminated timber (CLT) as a construction material for high-rise timber buildings has increased in the recent years especially in Europe and North America; a trend that is expected to continue. The CLT-elements will often be finished with an impermeable layer, whether it is walls, floors and, especially, roof. In Sweden, often no weather protection is used during the construction of the building, allowing the wood to be exposed to liquid water and relaying on later atmospheric conditions to dry the timber prior to finishing. The Swedish building regulations require a maximum surface moisture content (MC) of 18% before assembly of the elements and a maximum surface MC of 16% before the wood is covered. This could drive to high levels of MC within the CLT while the surface is already dry, which is a highly possible scenario in the case of high buildings where sun and wind create good conditions for a fast surface drying. At the same time, the regulation requires control of MC to be made with an electrical pin-type MC-meter, which is problematic because its reliability lays in part on the device reaching a certain penetration into the wood. The measurement of surface MC could thus be erroneous and the risk for mould development would be high even if the regulations are strictly followed. If a CLT with a too high moisture level are covered with an impermeable surface layer, the moisture is trapped within the CLT and may cause microbiological degradation that could be problematic to correct later on.An update in the regulation requirements is recommended, but such update must be based on a proper understanding of how moisture can be distributed in CLT and other wood-based building material during outdoor construction.

    This project aims to establish amethod to study (1) the effect of liquid-water-exposure time on the MC distribution of Spruce timber boards, but that could potentially be used in other wood-based building materials as well, and (2) the drying process under emulated outdoor conditions. The focus is set on those elements that are laid horizontally or with a very low inclination, such as floors and roofs. Sections of methacrylate are glued to the internal side of 43 x 200 mm planed spruce timber, allowing the wood to be exposed to standing water under a period of several days. CT images of different cross sections are taken periodically so that the evolution of MC profile can be monitored. The hypothesis is that the suction of liquid water will not be large and that it can dry quickly once the exposure to liquid water ends, but also that a MC gradient will develop beneath the surface which, under drying, may create regions of high MC that may be unnoticed by measuring with pin-type MC-meters.

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  • 23.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Kapillärt vattenupptag tvärs fibrerna i KL‐trä – Studier i CT: Slutrapport2021Report (Other academic)
    Abstract [en]

    The project aimed to study capillary water and moisture absorption through diffusion in spruce boards across fiber direction when exposed to liquid water for 168 h, as well as the drying after that. The study was driven by the necessity of fulfilling the HusAMA YSC.122 rule that states that the surface MC of the wood must not be above 18 % when it is built in and above 16 % if surface treatment will be done. CT scanning was used to study changing MC levels in 2.25 mm layers from the wood surface as average values for each layer. The layers are named after the deepest section of the layer i.e. layer 4.5 is between 2.25 mm and 4.5 mm.

    Water uptake: Results of the studies show that liquid water can penetrate down to 4.5 mm (MC >30%), even though in most cases it does not penetrate beyond 2.25 mm (surface layer). Local pockets or higher MC may nevertheless occur. None of the specimens shows liquid water penetration beyond the surface layer within the first 72 h of liquid water exposure. Neither density nor board side exposed (pith‐side or sapwood‐side) have an influence in the rate of liquid water/moisture absorption. Regarding the 18% limit established by HusAMA YSC.122, it can be reached within the first 24 hours of exposure, but its penetration is limited to around 6.75 mm of depth. Regarding the 16 % limit, a more heterogeneous behavior among specimens can be seen, with penetrations that go from 13.5 mm to 20.25 mm after 24 h of exposure.

    Drying: Drying took place by samples kept in room climate in the lab with no climate control or air‐velocity regulation. The conditions were equivalent to EMC of 6 %. All layers of the wood specimens are below 18 % within 48 h when water is removed after 168 h of exposure. The 16 % limit can take from 48 to up to 140 h to be reached by all layers in the atmospheric conditions of the lab, which at the moment of the experiment were extremely dry. This factor must be taken into account when interpreting results of this experiment not only during drying, but also during water uptake. 

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  • 24.
    Couceiro, José
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hansson, Lars
    Norwegian University of Science and Technology (NTNU), Department of ICT and Natural Sciences, Norway.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    CT scanning of capillary phenomena in bio-based materials2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 181-187Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive study of dynamic moisture processes in wood and other bio-based materials. In the CT facilities at Luleå University of Technology, it is possible to study wood-moisture relations such as water absorption, drying and related material deformation under a temperature- and humidity-controlled environment.An increase in the use of bio-based materials in building construction has led to an increased interest in capillary phenomena in these materials, because of an increasing number of moisture-related damage in timber and hybrid-timber buildings. This article shows some examples of how different bio-materials used in construction interact with liquid water over time. The overall purpose has been to develop the CT technique as a powerful tool for the determination and visualization of capillary flow that can be a base for modelling and an increased understanding of moisture flow in new bio-based building materials.Early-stage observation of the behaviour of different traditional and new bio-based building materials shows that CT scanning, combined with image processing, has a high potential to be used in performing non-destructive and non-contact tests that can help to increase the knowledge of water-material interactions and develop building materials with an optimized performance.

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  • 25.
    Cristescu, Carmen
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Markers of quality in self-bonded beech boards2017Conference paper (Refereed)
    Abstract [en]

    A self-bonding phenomenon takes place when five layers of beech (Fagus SylvaticaL.) veneers are pressed at temperatures higher than 200ºC. If the pressing temperature between veneer surfaces reaches at least 225ºC during pressing and if the pressure applied is optimal, water-resistant bonds are formed between veneers. This study investigates the relation of thickness reduction (marker of compression) and mass loss (marker of heat treatment intensity) to boards quality. The effect of water and water vapour on the bondings between veneer in boards pressed at 200, 225 and 250ºC is studied. The conclusion is that pressing 5 layers of 2 mm rotary-cut beech veneer parallel-fibered at 225ºC, 5 MPa and 300 s leads to a thickness reduction of 33.4 % and mass loss of 1.23 %; in such boards bondings are not resistant to liquid water but are resistant to vapour after one adsorption-desorption cycle. When pressing at 250ºC, 5 MPa and 300 seconds, the thickness reduction is 50% and the mass loss 4%; in such boards no delamination was observed when soaked in water. Boards pressed athigher temperature show lower hygroscopicity. Their equilibrium moisture content (EMC) rangedbetween 3.6 and 7%. Based on the results of this study it ishypothesised that the decay resistance of self-bonded boards will increase when increasing the severity of the hot-pressing.

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  • 26.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    A methodology for computing the relative icing degrees of logs stored in an open warehouse at ambient air temperature in winter2021In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 16, no 6, p. 421-428Article in journal (Refereed)
    Abstract [en]

    This paper describes a methodology for mathematical modeling, computing, and research of two mutually connected problems: 2D non-stationary temperature distribution in logs stored for a long time in an open warehouse at periodically changing ambient air temperature in winter and change in the icing degrees of the logs during this time. Mathematical descriptions of the periodically changing ambient air temperature and of three types of relative icing degree of the logs that result under the influence of that temperature have been presented. These descriptions are introduced in coupled 2D non-linear mathematical models of the heat distribution in logs during their freezing and defrosting. The paper presents solutions of the models with explicit form of the finite-difference method. Results from a simulative investigation of the 2D non-stationary temperature distribution, average mass temperature, and three types of icing degree of beech logs with industrial dimensions (diameter of 0.4 m and length of 0.8 m), moisture content of 0.6 kg·kg−1, and initial temperature of 0°C during their 5 days and nights alternating freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial values below −5°C and different amplitudes are graphically presented and analyzed. 

  • 27.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Dzurenda, Ladislav
    Department of Woodworking, Faculty of Wood Science and Technology, Technical University in Zvolen, Zvolen, Slovakia.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    An approach for computing the thermal balance and energy consumption of concrete pits during boiling of frozed logs for veneer production2023In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
  • 28.
    Deliiski, Nencho
    et al.
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Niemz, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Institute for Building Materials, ETH Zürich, Zürich, Switzerland.
    Vitchev, Pavlin
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Angelski, Dimitar
    Department of Furniture Production, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Tumbarkova, Natalia
    Department of Woodworking Machines, Faculty of Forest Industry, University of Forestry, Sofia, Bulgaria.
    Computing the duration of regimes for autoclave steaming of frozen wooden prisms under variable operating conditions in veneer production2022In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 17, no 6, p. 451-458Article in journal (Refereed)
  • 29.
    Duarte, Sónia
    et al.
    LEAF (Linking Landscape, Environment, Agriculture and Food) Research Centre, Instituto Superior de Agronomia, Universidade de Lisboa. Tapada da Ajuda, 1349-017 Lisboa, Portugal.
    Nunes, Lina
    LNEC, National Laboratory for Civil Engineering, Structures Department, Av. do Brasil, 101, 1700-066 Lisbon, Portugal. cE3c, Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group, University of the Azores, 9700–042 Angra do Heroísmo, Portugal.
    Kržišnik, Davor
    Biotechnical Faculty, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
    Humar, Miha
    Biotechnical Faculty, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamýcká 1176, 16521 Praha 6–Suchdol, Czech Republic.
    Influence of Zwitterionic Buffer Effects with Thermal Modification Treatments of Wood on Symbiotic Protists in Reticulitermes grassei Clément2021In: Insects, ISSN 2075-4450, E-ISSN 2075-4450, Vol. 12, no 2, article id 139Article in journal (Refereed)
    Abstract [en]

    The majority of thermal modification processes are at temperatures greater than 180 °C, resulting in a product with some properties enhanced and some diminished (e.g., mechanical properties). However, the durability of thermally modified wood to termite attack is recognised as low. Recent attempts at combining thermal modification with chemical modification, either prior to or directly after the thermal process, are promising. Buffers, although not influencing the reaction systems, may interact on exposure to certain conditions, potentially acting as promoters of biological changes. In this study, two zwitterionic buffers, bicine and tricine, chosen for their potential to form Maillard-type products with fragmented hemicelluloses/volatiles, were assessed with and without thermal modification for two wood species (spruce and beech), with subsequent evaluation of their effect against subterranean termites (Reticulitermes grassei Clément) and their symbiotic protists. The effect of the wood treatments on termites and their symbionts was visible after four weeks, especially for spruce treated with tricine and bicine and heat treatment (bicine HT), and for beech treated with bicine and bicine and heat treatment (bicine HT). The chemical behaviour of these substances should be further investigated when in contact with wood and also after heat treatment. This is the first study evaluating the effect of potential Maillard reactions with zwitterionic buffers on subterranean termite symbiotic fauna.

  • 30.
    Dvořák, Ondřej
    et al.
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Kvietková, Monika Sarvašová
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Šimůnková, Kristýna
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Machanec, Ondřej
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Pánek, Miloš
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Pastierovič, Filip
    Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    Lin, Chia-Feng
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Wood Processing and Biomaterials, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 1176, 165 00 Prague, Czech Republic.
    The Influence of the Initial Treatment of Oak Wood on Increasing the Durability of Exterior Transparent Coating Systems2023In: Polymers, E-ISSN 2073-4360, Vol. 15, no 15, article id 3251Article in journal (Refereed)
    Abstract [en]

    This study determined the impact of undertaking an initial treatment of oak wood by sealing its surface pores with epoxy resin, focusing on the durability of transparent coating systems when exposed outdoors. Throughout the exposure period, various parameters including color, gloss, surface wettability, and both macroscopic and microscopic surface evaluation were continuously monitored. The study involved two sets of samples: one set underwent the pretreatment, while the other did not. Subsequently, four coating systems were applied to the samples, comprising two solvent-based and two water-based coatings. The experiment was conducted over a period of two years, utilizing natural weathering methods within the premises of the Czech University of Life Sciences in Prague. The pretreatment with epoxy resin exhibited enhanced durability for all paint systems. The analysis showed a significant difference in gloss and color after 12 months of weathering exposure without any significant effect on surface wettability and sealing. However, after 24 months of the weathering exposure, no significant differences between the sealed and unsealed surface were observed. The most significant change in properties was noted for the water-based coatings used in coating systems number 3 and 4, and these coatings were rated as the best.

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  • 31.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Huber, Johannes A.J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Jacobsson, Peter
    Martinsons Träbroar AB.
    Mechanics of stress-laminated timber bridges with butt end joints2017Conference paper (Refereed)
    Abstract [en]

    A number of variants of single span and three-span stress-laminated timber bridge decks have been studied via finite element simulations and experiments. Glulam beams in the decks were in general shorter than the total length of span which means that there were butt end joints in the decks. The butt end of each beam in a joint was not connected to the other beam which means that each butt end joint reduced the strength and stiffness of the whole of the deck. Results for deflection and stresses were examined for the studied variants in the form of reduction factors for strength and stiffness relative to a deck without butt end joints.

    Factors are shown in diagrams as function of ratio butt end distance/beam width and also butt end distance/span width. Comparison of achieved results with existing Eurocode rules shows that Eurocode rules are not totally appropriate.

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  • 32.
    Esteves, Bruno
    et al.
    Department of Wood Engineering, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal; Centre for Natural Resources, Environment and Society-CERNAS-IPV Research Centre, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal.
    Ferreira, Helena
    Department of Environmental Engineering, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal.
    Viana, Hélder
    Department of Ecology and Sustainable Agriculture, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal; Centre for the Research and Technology of Agro-Environmental and Biological Sciences-CITAB, University of Trás-os-Montes and Alto Douro, Quinta de Prados, 5000-801 Vila Real, Portugal.
    Ferreira, José
    Department of Wood Engineering, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal; Centre for Natural Resources, Environment and Society-CERNAS-IPV Research Centre, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal.
    Domingos, Idalina
    Department of Wood Engineering, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal; Centre for Natural Resources, Environment and Society-CERNAS-IPV Research Centre, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal.
    Cruz-Lopes, Luísa
    Centre for Natural Resources, Environment and Society-CERNAS-IPV Research Centre, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal; Department of Environmental Engineering, Polytechnic Institute of Viseu, Av. Cor. José Maria Vale de Andrade, 3504-510 Viseu, Portugal.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Department of Forestry and Biomaterials, Czech University of Life Sciences, Kamýcká 1176, Praha 6, 16521 Suchdol, Czech Republic.
    Nunes, Lina
    Structures Department, LNEC, National Laboratory for Civil Engineering, Av. do Brasil, 101, 1700-066 Lisbon, Portugal; Centre for Ecology, Evolution and Environmental Changes (cE3c), Rua Capitão João d’Ávila, 9700-042 Angra do Heroísmo, Portugal; Azorean Biodiversity Group, University of Azores, Rua Capitão João d’Ávila, 9700-042 Angra do Heroísmo, Portugal.
    Termite Resistance, Chemical and Mechanical Characterization of Paulownia tomentosa Wood before and after Heat Treatment2021In: Forests, ISSN 1999-4907, E-ISSN 1999-4907, Vol. 12, no 8, article id 1114Article in journal (Refereed)
    Abstract [en]

    The introduction of new species in forest management must be undertaken with a degree of care, to help prevent the spread of invasive species. However, new species with higher profitability are needed to increase forest products value and the resilience of rural populations. Paulownia tomentosa has an extremely fast growth. The objective and novelty of this work was to study the potential use of young Paulownia trees grown in Portugal by using heat treatment to improve its properties, thereby allowing higher value applications of the wood. The average chemical composition of untreated and heat-treated wood was determined. The extractive content was determined by successive Soxhlet extraction with dichloromethane (DCM), ethanol and water as solvents. The composition of lipophilic extracts was performed by injection in GC-MS with mass detection. Insoluble and soluble lignin, holocellulose and α-cellulose were also determined. Physical (density and water absorption and dimensional stability) and mechanical properties (bending strength and bending stiffness) and termite resistance was also determined. Results showed that extractive content increased in all solvents, lignin and α-cellulose also increased and hemicelluloses decreased. Compounds derived from the thermal degradation of lignin were found in heat-treated wood extractions. Dimensional stability improved but there was a decrease in mechanical properties. Resistance against termites was better for untreated wood than for heat-treated wood, possibly due to the thermal degradation of some toxic extractives.

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  • 33.
    Fašalek, Andrej
    et al.
    Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
    Straže, Aleš
    Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
    Šega, Bogdan
    Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
    Huber, Johannes Albert Josef
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Šernek, Milan
    Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
    Bonding Performance of Melamine–Urea–Formaldehyde and Polyurethane Adhesives for Laminated Hybrid Beams and Their Selected Mechanical Properties2023In: Buildings, E-ISSN 2075-5309, Vol. 13, no 8, article id 2087Article in journal (Refereed)
    Abstract [en]

    Beech (Fagus Sylvatica L.) is a prevalent tree species in Slovenia and is suitable for manufacturing glulam beams. However, beech wood has certain limitations that can potentially be mitigated by combining it with Norway spruce (Picea abies (L.) Karst.) wood to create hybrid beams. This study aimed to determine the bonding performance of commonly used melamine–urea–formaldehyde and polyurethane adhesives for these hybrid beams. Moreover, how varying the proportion of beech wood in a hybrid beam affects its mechanical properties was examined. Shear and delamination tests (method B) were conducted, and EN 14080:2013 requirements were met in all cases. The four-point bending tests of the beams showed that hybrid beams containing 20% of beech wood in the cross-sectional height on each side of the neutral axis exhibited a similar modulus of elasticity values as pure beech beams, but their strength was not equally improved. Hybrid beams with 11% of beech wood did not show any improvement in bending stiffness or strength compared to pure spruce beams. It was noted that the presence of beech wood in a hybrid beam can influence its failure mode. Furthermore, analytical calculations showed that a symmetrical lay-up is preferable to an asymmetrical one to increase the effective modulus of elasticity.

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  • 34.
    Florisson, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Applied Mechanics, Uppsala University, Uppsala, Sweden.
    Hansson, Lars
    Ocean Operations and Civil Engineering, Norwegian University of Science and Technology, Ålesund, Norway.
    Couceiro, José
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Macroscopic X-ray computed tomography aided numerical modelling of moisture flow in sawn timber2022In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 80, no 6, p. 1351-1365Article in journal (Refereed)
    Abstract [en]

    Mathematical models are essential for the development of schedules for the air-circulation drying of timber in Swedish sawmills, but earlier models have been shown to be conservative leading to longer drying times than necessary. In the current study, macroscopic (macro) X-ray computed tomography (CT) has been used in both the development and validation of a finite element (FE) model, to enable the macro-CT aided FE modelling of the nonlinear transient moisture flow in wood. The model uses more advanced theory than has previously been used in Swedish sawmills, by incorporating a surface emission coefficient to simulate the surface resistance to moisture flow. A single piece of Norway spruce [Picea abies (L.) Karst.] timber was subjected to that part of a traditional kiln-drying schedule, which is associated with diffusion-driven moisture transport. The incorporation of macro-CT data into the FE model resulted in a more realistic representation of the board’s geometry, the initial moisture state, and the definition of material parameters. It also led to a better simulation of flow speed and moisture gradient, especially the asymmetric MC development within the cross section throughout the drying process.

  • 35.
    Florisson, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Vessby, Johan
    Department of Engineering and Chemical Science, Karlstad University, Karlstad, Sweden.
    Ormarsson, Sigurdur
    Department of Building Technology, Linnaeus University, Växjö, Sweden.
    A three-dimensional numerical analysis of moisture flow in wood and of the wood's hygro-mechanical and visco-elastic behaviour2021In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 55, no 5, p. 1269-1304Article in journal (Refereed)
    Abstract [en]

    A three-dimensional numerical model was employed in simulating nonlinear transient moisture flow in wood and the wood's hygro-mechanical and visco-elastic behaviour under such conditions. The model was developed using the finite element software Abaqus FEA, while taking account of the fibre orientation of the wood. The purpose of the study was to assess the ability of the model to simulate the response of wood beams to bending and to the climate of northern Europe. Four-point bending tests of small and clear wood specimens exposed to a constant temperature and to systematic changes in relative humidity were conducted to calibrate the numerical model. A validation of the model was then performed on the basis of a four-point bending test of solid timber beams subjected to natural climatic conditions but sheltered from the direct effects of rain, wind and sunlight. The three-dimensional character of the model enabled a full analysis of the effects of changes in moisture content and in fibre orientation on stress developments in the wood. The results obtained showed a clear distinction between the effects of moisture on the stress developments caused by mechanical loads and the stress developments caused solely by changes in climate. The changes in moisture that occurred were found to have the strongest effect on the stress state that developed in areas in which the tangential direction of the material was aligned with the exchange surface of the beams. Such areas were found to be exposed to high-tension stress during drying and to stress reversal brought about by the uneven drying and shrinkage differences that developed between the outer surface and the inner sections of the beams.

  • 36.
    Florisson, Sara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Vessby, Johan
    Department of Engineering and Chemical Science, Karlstad University, Karlstad, Sweden.
    Ormarsson, Sigurdur
    Department of Building Technology, Linnaeus University, Växjö, Sweden.
    Numerical analysis of wood subjected to bending and northern European climate2021Conference paper (Other academic)
    Abstract [en]

    Due to the natural process of sorption, wood constantly interacts with the surrounding climate to establish an equilibrium moisture content, even without the direct influence of rain, solar radiation or wind. However, when wood is subjected to a combination of a change in moisture content and a state of stress brought on by e.g. mechanical load, differential shrinkage or swelling, or differences in material properties, a continuous change in the level of stress and the occurrence of deformations and fracture can be the result.

    The techniques available for in-situ monitoring of changes in moisture content and hygro-mechanical and viscoelastic behaviour can only be employed in specific locations in or around the wood. Whereas, modern techniques employed in laboratories, such as digital image correlation and computed tomography are laborious and time consuming. With recent developments in three-dimensional modelling, endless predictions can be made both of moisture flow and of the hygro-mechanical and visco-elastic behaviour of wood in three-dimensional space, requiring experimental data only to calibrate and validate the model.

    A three-dimensional numerical model was created in finite element software Abaqus FEA® to simulate both the transient nonlinear moisture flow and the moisture-dependent distortion and stress, while account is being taken of the fibre orientation (annual ring pattern, conical shape and spiral grain). A nonlinear single-Fickian model in connection with a nonlinear Neumann boundary condition is used to describe the moisture flow. For a moisture-sensitive and visco-elastic material such as wood, it is common to describe the total strain rate as a summation of the elastic, hygro-expansion, visco-elastic creep and mechano-sorptive strain rates.

    The aim was to determine whether the model was able to simulate in an adequate way the beam bending that occurs under northern European climate conditions. To accomplish this, the following steps were taken: 1) on the basis of experimental data available in literature, a set of expressions was created to describe the moisture- and temperature-dependent diffusion coefficient and surface emission coefficient, 2) experimental results obtained for small beams tested under constant temperature and systematic relative humidity (controlled climatic) conditions were used to calibrate the numerical model, account being taken of the spiral grain that applied and the annual ring curvature, and 3) test results for solid beams tested in northern European (natural) climatic conditions were used to validate the numerical model, account being taken of the fibre orientation.

    The results obtained showed a clear distinction between the effect of moisture on the stress development caused by mechanical load and the stress development caused solely by changes in climate. The changes in moisture that occurred were found to have the strongest effect on the stress state that developed in areas in which the tangential direction of the material was aligned with the exchange surface of the beams. Such areas were found to be exposed to high-tension stress during drying and to a stress overturn brought about by wetting. The material orientation showed to have a strong effect on the estimated deflection, calibrated material parameters and normative stress states.

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  • 37.
    Forghani, Kamran
    et al.
    Uppsala universitet.
    Carlsson, Mats
    Rise.
    Flener, Pierre
    Uppsala universitet.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Pearson, Justin
    Uppsala universitet.
    Yuan, Di
    Uppsala universitet.
    Maximizing Value Yield in Wood Industry through Flexible Sawing and Product Grading Based on Wane and Log ShapeIn: Computers and Electronics in Agriculture, ISSN 0168-1699, E-ISSN 1872-7107Article in journal (Refereed)
  • 38.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Information Technology and Data-Driven Decision Making in Swedish Sawmills2023In: Proceedings of the 25th International Wood Machining Seminar / [ed] Gary S. Schajer, 2023, article id 18Conference paper (Refereed)
  • 39.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Predicting strength of Norway spruce and Scots pine sawn timber using discrete X-ray log scanning, optical board scanning, traceability, and partial least squares regression2024In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 19, no 1, p. 1777-1788Article in journal (Refereed)
    Abstract [en]

    Recently developed technology in sawmills such as advanced log scanning and traceability concepts enable new ways of grading logs and boards. When it comes to strength grading, this is often done on sawn boards using automatic scanning systems. However, if board scanners were to be augmented with data from log scanners by using traceability, more information on the wood propertiesis available. In this study, the main objective was to compare the strength prediction capability of board scanning alone, to board scanning augmented with X-ray and 3D data from log scanning, for Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.). In that case, data from three different scanning systems  was combined, two for logs and one for boards. A further objective was to investigate whether pre-sorting logs for strength grading can be done using either 3D log data alone, or 3D log data augmented with X-ray data. The results show an improved strength prediction when adding log data to board data, and that 3D log data alone is not enough to pre-sort logs for strength, while adding X-ray log data makes it possible. Strength  prediction on Scots pine performed somewhat better than prediction on Norway spruce.

  • 40.
    Fredriksson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Using a Gaussian filter to reduce the effect of positioning errors when optimizing sawing of CT scanned Scots pine and Norway spruce logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    Computed tomography (CT) scanning of logs is being introduced in sawmills, so there is reason to study how log positioning can be controlled using information from CT. However, positioning errors affect this positioning optimization in a negative way. To reduce this effect, a method was developed using sawing simulation, where logs were sawn in a large number of positions, varying rotation and centering. This resulted in three-dimensional surfaces, with the sawn timber value, rotation and centering on the axes. The surfaces were filtered with a Gaussian filter using a distribution corresponding to that of the positioning error. The filtered values were used for optimization, choosing the global maximum. This resulted in a value recovery that was about two percent higher compared to a simpler optimization without filtering, for a normally distributed rotational error of 5 – 15° standard deviation and a ditto centering error of 3.5 – 10.5 mm standard deviation. This was tested using sawing simulation, using the optimal log position for the two methods, with an added positioning error. Furthermore, the robust method has been tested on a smaller number of rotational positions, starting from horns down, to reduce the number of necessary calculations. The result of this was that at least ± 60 ° in the rotational direction should be evaluated for the robust method to result in a higher recovery than the simpler optimization. The robust method was better than sawing horns down and centered, no matter the positioning error, using only 65 evaluated positions per log.

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  • 41.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Factors Affecting Volume Yield in a Forestry-Wood Value Chain: A Simulation Study Based on CT Scanning2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 540-548Article in journal (Refereed)
    Abstract [en]

    The paper presents the results of a simulation study, where log models based on CT scanned logs of Scots pine (Pinus sylvestris L.) was used as input material to a computer simulation model of a generic value chain involving sawing, drying, crosscutting and finger jointing. The aim was to investigate which factors that affect the volume yield in the value chain, be it forestal, log-, process- or quality-related factors. The results show that factors related to growth conditions and log size have a large impact on the volume yield in the studied value chain, together with quality requirements on knots. Factors such as sawing positioning and log quality had a much smaller impact. It can be concluded that it is possible to model a forestry-wood value chain, while assessing which input variables affect the result in terms of volume yield, using CT scanning of logs and subsequent computer simulation of the production processes.

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  • 42.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Use of CT-Scanning Technology in Wood Value-Chain Research and in Wood Industry: A State of The Art2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 533-539Article in journal (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) is a powerful tool for the non-destructive  measurement  of  dynamic  processes in wood. After more than 25 years of research at Luleå University of Technology in the field of CT-scanning of wood material, the first industrial CT-scanners are now installed in sawmill production for the in-situ measurement of internal  log features to steer of the sawmill process with the help of this information.This  paper  provides  an  overview  of  the  potential  of  CT-scanning in wood-material  research  and  how  this data can be used for the modelling and simulation of the wood value chain. A database of CT-images of trees  is  used  to  create  a  log  model  including  the  outer  shape  of  the  logs  and  their  internal  knot  structure.  Simulation software is used to saw these virtual logs in different positions relative to the sawblade, and also for the crosscutting of the sawn timber to components. The output is dimensions and grades of sawn timber, volume yield as well as an economic result based on real economic conditions. A specially designed climate chamber  for  CT  studies  of  the  drying  of  sawn  timber  is  used  to  increase  the  knowledge  of  how  the  drying  affects the response from the sawn timber during seasoning.

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  • 43.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Brännström, Mattias
    Renewinn AB, Bengtsgårdsvägen 32, Sågmyra, 790 22, Sweden; Setra Group AB, Gårdsvägen 18, Solna, 169 70, Sweden .
    Technical solutions to increase competitiveness of cross-laminated timber from the Nordic countries: an overview2018In: WCTE 2018 - World Conference on Timber Engineering, World Conference on Timber Engineering (WCTE) , 2018Conference paper (Refereed)
    Abstract [en]

    In order to increase the competitiveness of cross-laminated timber (CLT) produced in northern Europe, several methods are presented in this paper. One deals with increasing the strength and stiffness properties of CLT panels, something that has a potential to decrease material use. This is achieved by changing the alteration angle of transverse CLT panel layers to 45° instead of 90°. Two other methods focus on increasing the volume yield of CLT panel production, utilizing the natural taper of the log when edging flitches. One is a trapeze edging method, following the taper closely, while the other is a more conventional crosscutting and straight edging method. Both are based on live sawing of small diameter logs. The result is a yield increase of 10-17 percentage points, compared to more conventional cant sawing.

  • 44.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cool, Julie
    University of British Columbia.
    Avramidis, Stavros
    University of British Columbia.
    Knot detection in computed tomography images of partially dried Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs2017In: International Wood Machining Seminar (IWMS-23), 2017Conference paper (Refereed)
    Abstract [en]

    X-ray computed tomography (CT) of logs means possibilities for optimizing breakdown in sawmills. This depends on accurate detection of knots to assess internal quality. However, as logs are stored in the log yard they dry to a certain extent, and this drying affects the density variation in the log, and therefore the X-ray images. For this reason, it is hypothetically difficult to detect log features in partially dried logs using X-ray CT. The objective of this research was to investigate the effect of drying on knot detection in Jack pine (Pinus banksiana Lamb.) and white spruce (Picea glauca (Moench) Voss) logs from New Brunswick, Canada. An automatic knot detection algorithm was compared to manual measurements for this purpose, and the results show that knot detection was clearly affected by partial drying. Because dried heartwood and sapwood have similar densities, the algorithm had difficulties detecting the heartwood-sapwood border. Based on how well the heartwood-sapwood border was detected, it was statistically possible to sort logs into two groups: 1) Low knot detection rate, and 2) High knot detection rate. In that way, a decision can be made whether or not to trust the knot models obtained from CT scanning. Therefore, logs that are partially dried out and fall in the low knot detection rate should be handled cautiously because the optimization results based on CT knot detection cannot be fully trusted. Sawing of these logs could be optimized using only their outer shape, ignoring internal quality. Similarly, only logs having a regular heartwood shape should be used when scanning logs for research purposes or in databases of CT scanned logs. Finally, a larger knot detection rate was obtained for Jack pine. This could have been facilitated by the fact that pine trees usually have larger but less numerous knots than spruce trees.

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  • 45.
    Gaff, Milan
    et al.
    Czech University of Life Sciences Prague (CULS).
    Babiak, Marián
    Czech University of Life Sciences Prague (CULS).
    Kačík, František
    Czech University of Life Sciences Prague (CULS), Technical University in Zvolen.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Turčan, Marek
    Czech University of Life Sciences Prague (CULS).
    Hanzlíka, Peter
    Czech University of Life Sciences Prague (CULS).
    Vondrová, Veronika
    Czech University of Life Sciences Prague (CULS).
    Plasticity properties of thermally modified timber in bending: the effect of chemical changes during modification of European oak and Norway spruce.2019In: Composites Part B: Engineering, ISSN 1359-8368, E-ISSN 1879-1069, Vol. 165, p. 613-625Article in journal (Refereed)
    Abstract [en]

    The plasticity of thermally modified European oak (Quercus robur L.) and f thermally modified Norway spruce (Picea abies Karst. (L.)) timber was evaluated in bending, and the plastic properties were related to the changes in chemical composition of the wood after modification. The objective was to gain new knowledge about the properties of materials in the plastic region of the force-deformation diagram in bending. A new software was developed (MATESS) and used to identify important characteristics of the material. This software eliminates shortcomings in current standards, such as simplifications in the evaluation of data when sufficiently sensitive measuring equipment is not available. The characteristics studied were: modulus of rupture (MOR), plastic potential (PP) chord modulus (CHM), the moduli of plasticity (EE), and the moduli of plasticity (EMV, EP). Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed chemically to reveal the patterns that occur during the loading of the specimens. Thermal modification has different effects on the mechanical properties of oak and spruce, especially on CHM, EMV and EP, due to their different contents and structures of their chemical components. A strong correlation (r > 0.90) between hemicellulose content and MOR and Pp values was found for both species. The coefficients of determination indicated a very low dependence (r2 < 0.1) of MOR, PP, CHM, EE, EMV and EP, on the average density.

  • 46.
    Garskaite, Edita
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Balciunas, Giedrius
    Laboratory of Thermal Insulating Materials and Acoustics, Institute of Building Materials, Vilnius Gediminas Technical University, Linkmenu g. 28, Vilnius LT-08217, Lithuania.
    Drienovsky, Marian
    Institute of Materials Science, Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, Ulica Jana Bottu 2781/25, 91724 Trnava, Slovakia.
    Sokol, Denis
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko 24, Vilnius LT-03225, Lithuania.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Bastos, Alexandre C.
    Department of Materials and Ceramics Engineering and CICECO – Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
    Salak, Andrei N.
    Department of Materials and Ceramics Engineering and CICECO – Aveiro Institute of Materials, University of Aveiro, 3810-193 Aveiro, Portugal.
    Brushite mineralised Scots pine (Pinus sylvestris L.) sapwood – revealing mineral crystallization withina wood matrix by in situ XRD2023In: RSC Advances, E-ISSN 2046-2069, Vol. 13, p. 5813-5825Article in journal (Refereed)
    Abstract [en]

    Dicalcium phosphate dihydrate (CaHPO4·2H2O, DCPD, brushite) crystals were synthesised within Scots pine sapwood via a wet-chemistry route from aqueous solutions of Ca(CH3COO)2 and NH4H2PO4 salts. SEM/EDS analysis was used to assess the saturation of the wood cell lumina and cell wall as well as morphological features and elemental composition of the co-precipitated mineral. Brushite mineral crystallization and crystallite growth within the wood matrix was studied by in situ XRD. The chemical composition of the mineral before and after the dissolution was evaluated using FTIR spectroscopy. The overall impact of brushite on the thermal behaviour of wood was studied by TGA/DSC and TGA/DTA/MS analysis under oxidative and pyrolytic conditions. Bending and compression strength perpendicular and parallel to the fibre directions as well as bending strengths in longitudinal and transverse directions of the mineralised wood were also evaluated. Results indicate the viability of the wet-chemistry processing route for wood reinforcement with crystalline calcium phosphate (CaP)-based minerals, and imply a potential in producing hybrid bio-based materials that could be attractive in the construction sector as an environmentally friendly building material.

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  • 47.
    Garskaite, Edita
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Karlsson, Olov
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stankeviciute, Zivile
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius, Lithuania.
    Aivaras, Kareiva
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius, Lithuania.
    Jones, Dennis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Surface hardness and flammability of Na2SiO3 and nano-TiO2 reinforced wood composites2019In: RSC Advances, E-ISSN 2046-2069, Vol. 9, no 48, p. 27973-27986Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to explore an effect of the combined inorganic materials on the wood hardness and flame-retardancy properties in a concept of sustainable material management. Herein, the reinforcement of Scots pine (Pinus sylvestris L.) sapwood with sodium silicate and TiO2 nanoparticles via vacuum-pressure technique is reported. Pyrolysis of modified wood was studied by TG-FTIR analysis; the results showed that maximum weight loss for the modified wood was obtained at 40–50 °C lower temperatures compared to the reference untreated wood. The Gram–Schmidt profiles and spectra extracted at maxima absorption from Gram–Schmidt plots indicated chemical changes in wood–inorganic composites. SEM/EDS analysis revealed the presence of Na–O–Si solid gel within the wood-cell lumen and showed that TiO2 was homogeneously distributed within the amorphous Na–O–Si glass-forming phase to form a thin surface coating. EDS mapping further revealed the higher diffusivity of sodium into the cell wall compared to the silicon compound. The presence of amorphous sodium silicate and nano-TiO2 was additionally confirmed by XRD analysis. FTIR spectra confirmed the chemical changes in Scots pine sapwood induced by alkalization. Brinell hardness test showed that the hardness of the modified wood increased with the highest value (44% increase in hardness) obtained for 10% Na2SiO3–nTiO2 modified wood. The results showed good correlation between TG and flammability test; limiting oxygen index (LOI) values for the wood–inorganic composites increased by 9–14% compared to the untreated wood.

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  • 48.
    Garskaite, Edita
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Stoll, Sarah L.
    Chemistry Department, Georgetown University, Washington, D.C. 20057, United States.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Lycksam, Henrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Stankeviciute, Zivile
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius LT- 03225, Lithuania.
    Kareiva, Aivaras
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Vilnius LT-03225, Lithuania.
    Quintana, Alberto
    Physics Department, Georgetown University, Washington, D.C. 20057, United States.
    Jensen, Christopher J.
    Physics Department, Georgetown University, Washington, D.C. 20057, United States.
    Liu, Kai
    Physics Department, Georgetown University, Washington, D.C. 20057, United States.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The Accessibility of the Cell Wall in Scots Pine (Pinus sylvestris L.) Sapwood to Colloidal Fe3O4 Nanoparticles2021In: ACS Omega, E-ISSN 2470-1343, Vol. 6, no 33, p. 21719-21729Article in journal (Refereed)
    Abstract [en]

    This work presents a rapid and facile way to access the cell wall of wood with magnetic nanoparticles (NPs), providing insights into a method of wood modification to prepare hybrid bio-based functional materials. Diffusion-driven infiltration into Scots pine (Pinus sylvestris L.) sapwood was achieved using colloidal Fe3O4 nanoparticles. Optical microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy, transmission electron microscopy, and X-ray powder diffraction analyses were used to detect and assess the accessibility of the cell wall to Fe3O4. The structural changes, filling of tracheids (cell lumina), and NP infiltration depth were further evaluated by performing X-ray microcomputed tomography analysis. Fourier transform infrared spectroscopy was used to assess the chemical changes in Scots pine induced by the interaction of the wood with the solvent. The thermal stability of Fe3O4-modified wood was studied by thermogravimetric analysis. Successful infiltration of the Fe3O4 NPs was confirmed by measuring the magnetic properties of cross-sectioned layers of the modified wood. The results indicate the feasibility of creating multiple functionalities that may lead to many future applications, including structural nanomaterials with desirable thermal properties, magnetic devices, and sensors. 

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  • 49.
    Glavonjić, Branko
    et al.
    Faculty of Forestry, University of Belgrade, Serbia.
    Kitek Kuzman, Manja
    Wood Science and Technology, University of Ljubljana, Slovenia.
    Sandberg, Dick
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Kompozitni proizvodi od drveta – Drvo kao  materijal u građevinarstvu i arhitekturi.2022 (ed. 1)Book (Refereed)
    Abstract [en]

    No material has filtered into our lives for as long and in as many ways as wood in its many shapes. Engineered Wood Products (EWPs)  present the bridge between wood science, structural engineering, architecture and design. This book explores and illustrates the uses of various contemporary EWPs and introduces some new wood-based materials. Each page spread describes and presents information, about a specific EWP and the EWP is illustrated with inspiring images showing applications of the EWP in architecture, building construction and interiors.

    The present work grew out of the interdisciplinary collaboration and different experiences of three wood scientists from Slovenia, Sweden and the Serbia with different backgrounds - the wood engineers with experience and knowledge of technological needs, the architect with a deep knowledge of culture-based needs and wood scientists experienced in environmental science and forestry.

  • 50.
    Golubevas, Ricardas
    et al.
    Vilnius University, Lithuania.
    Stankeviciute, Zivile
    Vilnius University, Lithuania.
    Zarkov, Aleksej
    Vilnius University, Lithuania.
    Golubevas, Raimundas
    Private Dental Clinic RG Clinic, Kalvarijų 137D-5, Vilnius LT-08221, Lithuania .
    Hansson, Lars
    Department of Ocean Operations and Civil Engineering, Faculty of Engineering, Norwegian University of Science and Technology, Larsgårdsvegen 2, 6025 Ålesund, Norway .
    Raudonis, Rimantas
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko 24, Vilnius LT-03225, Lithuania .
    Kareiva, Aivaras
    Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko 24, Vilnius LT-03225, Lithuania .
    Garskaite, Edita
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Acrylate–gelatin–carbonated hydroxyapatite (cHAP) composites for dental bone-tissue applications2020In: Materials Advances, E-ISSN 2633-5409, Vol. 1, no 6, p. 1675-1684Article in journal (Refereed)
    Abstract [en]

    Various types of scaffolds made of synthetic polymers have been widely studied for bone-tissue applications due to their mechanical strength, biocompatibility and biodegradability, but the hydrophobic nature of synthetic polymers and frequent absence of pores within the scaffolds inhibit cellular attachment, infiltration, and tissue ingrowth. In this study, multi-composite scaffolds composed of dipentaerythritol hexa-acrylate (DPHA), ethylene glycol dimethacrylate (EGDMA), gelatin, and carbonated hydroxyapatite (cHAP) have been made. Percentage ratio of polymer matrix to gelatin was varied 50/50, 75/25, and 95/5 to change the porosity of the resultant scaffolds. The structure, crystallinity, and phase composition of the cHAP were confirmed by FTIR, Raman, XRD and Rietveld analyses, TG/DSC was used to evaluate the distribution of ceramics within the polymer matrix, and FTIR-ATR was used to confirm the molecular structure of composites. SEM/EDS analysis of the scaffolds revealed cavities and irregularities in the surface, and that cHAP was indistinctly exposed on the composite surface, computed tomography (CT) was used to estimate the density and homogeneity of the scaffolds, and the cHAP distribution within the scaffolds was evaluated by conventional radiography. The hydrophilicity of the multi-composite scaffolds was investigated using an aqueous solution of methylene blue dye which showed that the acrylate(75%)–gelatin(25%)–cHAP composite had the highest hydrophilicity. The results suggest that acrylate–gelatin–cHAP scaffolds have a potential for bone-tissue engineering. 

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