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  • 101.
    Bader, Thomas K.
    et al.
    Vienna University of Technology, Austria.
    Wikete, Christoph
    Jäger, Andreas
    Hofstetter, Karin
    Eberhardsteiner, Josef
    Mechanical Properties and Microstructural Characteristics of Hardwood2010In: COST Action FP 0802 Workshop: Wood Structure/Function-Relationships, 5-8 October, 2010, Hamburg, Germany, Hamburg, Germany, 2010, p. 61-Conference paper (Other academic)
  • 102. Bastani, A
    et al.
    Militz, H
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Effect of wood modification on water related properties and penetration of adhesives into Scots pine and beech2015In: Eighth European Conference on Wood Modification, October 26-27, Helsinki, Finland, Aalto University , 2015, p. 367-371Conference paper (Refereed)
  • 103.
    Bastani, Alireza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Koddenberg, Tim
    Georg-August-University Göttingen, Germany.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Study of adhesive bondlines in modified wood with fluorescence microscopy and X-ray micro-computed tomography2016In: International Journal of Adhesion and Adhesives, ISSN 0143-7496, E-ISSN 1879-0127, Vol. 68, p. 351-358Article in journal (Refereed)
    Abstract [en]

    The quantitative penetration of three coldset wood adhesives [one-component polyurethane (PU), emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc)] under hydraulic pressure into different types of modified wood was studied using fluorescence microscopy and the results were compared to these of a previous study without pressure on adjacent wood samples. The effective penetration (EP) of PU was negatively affected by furfurlylation and NMM modification when pressure was applied. For PVAc, 30% NMM treatment and heat treatment of Scots pine and beech at 210 °C had a negative effect on its EP, but against this the EP of this adhesive increased after heat treatment of beech at 195 °C. In the case of furfurylation, the depth of penetration of all adhesives was less into wood treated with higher concentration of furfuryl alcohol. PU showed a much deeper penetration into NMM-modified and heat-treated wood than the other adhesives with the exception of heat-treated beech at 195 °C. Application of pressure led to rather different results as compared to the EP data when no pressure was applied. The three-dimensional (3D) visualisation of the penetration of PU adhesive into heat-treated Scots pine was also examined by X-ray micro-computed tomography (XµCT). The 3D flow pattern of PU adhesive into heat-treated Scots pine was clearly depicted by XµCT.

  • 104.
    Bastani, Alireza
    et al.
    University of Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    University of Göttingen, Germany.
    Effect of open assembly time and equilibrium moisture content on the penetration of polyurethane adhesive into thermally modified wood2017In: The journal of adhesion, ISSN 0021-8464, E-ISSN 1563-518X, Vol. 93, no 7, p. 575-583Article in journal (Refereed)
    Abstract [en]

    The effect of wood moisture content and open assembly time on penetration of polyurethane (PU) adhesive into thermally treated Scots pine (195 and 210°C) was investigated according to effective (EP) and maximum penetration (MP) measurements using fluorescence microscopy. For samples treated at 195°C, a higher EP was noted at 8.6% equilibrium moisture content (EMC) after both assembly times (15 and 30 min) while for samples treated at 210°C, increasing wood moisture content resulted in a significant decrease in EP at 12.5% EMC after 15 min assembly time. Extending open assembly time was found to increase the EP of PU adhesive only in the case of samples treated at 195°C and with 8.6% EMC. For samples treated at both treatment temperatures and after shorter open assembly time, the highest MP observed at moderate EMC levels of 8.6 and 8.2% and the lowest at the higher EMC levels of 13.2 and 12.5%.

  • 105.
    Bastani, Alireza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Gross adhesive penetration in furfurylated, N-methylol melamine-modified and heat-treated wood examined by fluorescence microscopy2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 5, p. 635-642Article in journal (Refereed)
    Abstract [en]

    This study investigated the radial penetration of three conventional cold-set wood adhesives [emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc), one-component polyurethane (PU)] into various degrees of furfurylated and N-methylol melamine-modified (NMM) Scots pine, and heat-treated Scots pine and beech based on measurements of effective (EP) and maximum penetration (MP) from microscopic observations. EP of EPI adhesive decreased after modification with higher concentration of furfuryl alcohol while an improved penetration was recorded for PVAc into furfurylated wood. A deeper penetration was observed for all adhesives into wood treated with lower concentration of furfuryl alcohol. The EP of EPI and PU adhesives reduced after NMM treatment but it increased in the case of PVAc. In spite of reduction of EP of PU after NMM treatment, it represented a deeper penetration among all adhesives possibly due to its lower molecular weight. For Scots pine, increasing the treatment temperature improved EP of all adhesives while for beech, the EP of PU and PVAc increased largely in the case of samples treated at 195 °C. Visual analysis of fluorescence microscopy pictures provided more detailed information on modality of penetration. The results are useful for understanding the interaction among common adhesives and modified materials, and can be used in future research to explain the bonding behavior of modified wood.

  • 106.
    Bastani, Alireza
    et al.
    University of Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    University of Göttingen, Germany.
    Shear strength of furfurylated, N-methylol melamine and thermally modified wood bonded with three conventional adhesives2017In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 12, no 4, p. 236-241Article in journal (Refereed)
    Abstract [en]

    The shear strength of furfurylated, N-methylol melamine (NMM) and thermally modified wood bonded with emulsion polymer isocyanate, polyvinyl acetate (PVAc), and polyurethane (PU) adhesives was examined. Furfurylation and NMM modification of Scots pine had a significant negative effect on the bonding strength with all adhesives irrespective of the treatment intensity. The obtained low-shear strength values were related to the brittle nature of the wood after modifications rather to the failure of the bondline. PVAc showed a better bonding performance with both furfurylated and NMM modified wood while the combination of furfurylated wood and PU gave the highest reduction in bonding strength (47–51%). Shear strength also decreased significantly after thermal modification in both Scots pine (36–56%) and beech (34–48%) with all adhesives. With the exception of thermally modified beech samples bonded with PU, bondline was found to be the weakest link in thermally modified wood as it was revealed by the wood failure surfaces. Bondline thickness and effective penetration of adhesives did not relate to the shear strength of all modified wood materials. The lower shear strength of modified wood could be attributed to other factors, such as the reduced chemical bonding or mechanical interlocking of adhesives, and the reduced strength of brittle modified wood substrate.

  • 107.
    Bastani, Alireza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Water uptake and wetting behaviour of furfurylated, N-methylol melamine modified and heat-treated wood2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 5, p. 627-634Article in journal (Refereed)
    Abstract [en]

    This study reports on the water uptake (WU) and wetting properties of different modified wood materials; furfurylated and N-methylol melamine (NMM) modified Scots pine, and heat-treated (Vacu3 method) Scots pine and beech. All modifications caused a substantial reduction in WU in the longitudinal, tangential and radial directions both after short (24 h) and long contact times (168, 336 h) with a saturated sponge. The water uptake coefficient (w t ) was reduced by approximately 71–89 % in furfurylated wood, with the higher weight percent gain (WPG) providing a slightly greater reduction. The reduction in WU was not found to depend on the NMM solid content. The NMM treatment had the maximum effect on the reduction of tangential w t by 80–84 % and was much smaller in the longitudinal direction (31–68 %). The treatment temperature of 195 °C gave lower WU values than treatment at 210 °C, and the only exception was the radial direction of Scots pine. The longitudinal w t of heat-treated beech represented the highest reduction by 81–89 %, while radial w t was less affected in both species. Sessile drop apparent contact angles for water and diidomethane and corresponding surface energies on planed tangential and radial wood surfaces revealed an increased hydrophobicity and reduced polarity of modified wood. Furfurylated and NMM modified tangential surfaces had a higher increase of apparent contact angles than the radial surfaces but this was not observed in the case of heat treatment. Heat-treated wood showed reduced wetting of surfaces only with water. Apparent contact angles did neither differ with treatment temperature nor with the NMM resin load. The disperse component of surface energy was slightly increased by 20 % maximum in modified wood, while the polar components showed a dramatic decrease by −30 to −90 % with no major differences among treatments and intensities, and between surfaces. The results provide a better understanding of the hygroscopic behaviour of modified wood, which might be useful to predict its adhesion with various polymers such as glues, coatings and paints.

  • 108.
    Bastani, Alireza
    et al.
    George-August University, Germany.
    Militz, Holger
    George-August University, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Rohumaa, Anti
    Alto University School of Chemical Technology, Finland.
    Development of bonding strength of modified birch veneers during adhesive curing2016In: Wood research, ISSN 1336-4561, Vol. 61, no 2, p. 205-214Article in journal (Refereed)
    Abstract [en]

    This study investigated the bonding strength development of furfurylated, N-methylolmelamine (NMM) modified and thermally treated birch veneers glued with hot curing phenolformaldehyde (PF) adhesive in different pressing (20, 160 s) and open assembly times (20 s, 10min). For testing, the automated bonding evaluation system ABES was used with 2 N.mm-2applied pressure at 130°C. The bonding strength of both modified and unmodified samplesincreased significantly by prolongation of the pressing time from 20 to 160 s in all cases andfor both open assembly times. A deviation was observed for the samples treated at 220°C andat 20 s open assembly time. With the exception of NMM modified veneers, bonding strengthdid not change significantly by increasing the assembly time in the case of 20 s pressing forboth modified and unmodified samples. At 160 s pressing time, extension of the assembly timedeveloped a better bonding for controls, NMM modified and thermally treated veneers at 180°C.The combination of 10 min assembly time and 160 s pressing time proved as the optimal bondingcondition for controls, NMM modified and thermally treated veneers at 180°C while the highestbonding strength was noted in 20 assembly time and 160 s pressing time for furfurylated veneers.In most of the cases modification affected negatively the bonding performance of the veneers, inparticular for furfurylated and NMM modified samples.

  • 109.
    Bengtsson, Peter
    Växjö University, Faculty of Mathematics/Science/Technology.
    Development towards an efficient and sustainable biofuel drying2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The usage of biofuel as well as wood fuel has increased in Sweden and all of Europe during recent decades, and there are several reasons to believe that this increase will continue. An important reason for this increase is that the environmental and climate problems caused by fossil fuels are becoming even more evident. By replacing fossil fuel with biofuel, the problem of emissions from, among others carbon dioxide and sulphur compounds can be alleviated. However, substitution requires in many cases high quality processed biofuel. An early stage in the processing of biofuel is drying. Previous work treats the possibility of drying wood fuel in an efficient and environmentally sustainable manner.

    This thesis studies the bed drying technique, conducted both experimentally and through modeling of the drying process. The experimental work is based on continuous temperature measurements in the fuel bed and provides characteristics of the drying zone that develops in the bed during drying. The character of the drying zone is affected by both the qualities of the fuel and the operating parameters, and is decisive regarding the possibility of making the drying more efficient, i.e. optimize the usage of energy and produce a fuel with low and homogeneous moisture content.

    A mathematical simulation model has been developed to increase the understanding of bed drying. The model is based on fundamental physical principles and is made up of five differential equations that describe vapor flow, air flow, the fuel’s moisture content, and the bed’s pressure and temperature. The modeling work complements the experimental work and a simulation of the temperature distribution, pressure and the drying zone’s dispersion is in agreement with the experimental result.

    The drying of wood can signify an environmental and human health risk, since volatile organic compounds (VOC) are emitted during drying. The thesis studies these emissions with regards to type and quantity. The measurements show that the majority of the emitted compounds from Norway spruce and Scots pine are volatile monoterpenes, but also that other compounds are emitted, especially higher terpenes. Further, major differences between how the compounds are emitted and the quantities of the emitted compounds from heartwood and sapwood are shown. There are also large differences between types of wood, i.e. spruce and pine. It can be stated that both emission rate and total amount of emitted compounds increase with an increase in temperature.

    To reduce VOC emissions, the drying temperature should be maintained low. To develop an efficient bed drying process for wood biofuels, additional parameters must be analyzed further and weighed against each other. Based on the experimental method and the simulation model presented here, the drying can be optimized towards a more efficient use of thermal energy and a low and even moisture content in the dried biofuel.

  • 110.
    Bergström, M
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Blom, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Thörnqvist, Thomas
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Uttorkning av vindfällda träd2007Report (Other academic)
  • 111.
    Bergström, Mikael
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Thörnqvist, Thomas
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Dolda fel i stormskadat virke2007Report (Other academic)
  • 112.
    Bergström, Mikael
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Thörnqvist, Thomas
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Hur länge klarar sig stormfällt virke mot svamp- och insektsangrepp: Tema: Efter stormen2005Report (Other (popular science, discussion, etc.))
  • 113. Bianchi, S
    et al.
    Placencia Peña, M.I
    Ganne-Chédeville, C
    Pichelin, F
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Softwood strand-boards manufacturing without adhesive using linear friction welding technology2012In: Current and Future Trends of Thermo-Hydro-Mechanical Modification of Wood., Nancy University , 2012, p. 142-143Conference paper (Refereed)
  • 114.
    Birbilis, Dimitrios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Karastergiou, Sotirios
    Technological Educational Institute of Thessaly, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Kakavas, Konstantinos
    Technological Educational Institute of Thessaly, Greece.
    Tsioukas, Thomas
    Technological Educational Institute of Thessaly, Greece.
    Properties of black pine (Pinus nigra Arn.) wood treated with hot rape oil2014In: Wood Structure, Properties and Quality – 2014: 5th RCCWS International Symposium, Moscow State University Press, 2014, p. 30-34Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to examine oil-retention, swelling, adsorption, static bending properties and tensile strength of lap joints of black pine (Pinus nigra Arn.) wood treated with hot rape oil. Wood specimens were impregnated in a steel vessel using the empty cell process (Lowry method). Rape oil retention of black pine specimens ranged between 122 and 193 kg/m3. Total swelling of specimens was not affected by the impregnation but the rate of swelling was decreased. The impregnated specimens had an adsorption of 21%, while the untreated 75%. The oil heat-treatment process was found to affect the tensile strength of lap joints. The impregnated specimens showed a lower tensile strength of about 10% than the un-treated. The treatment did not affect the static bending strength of black pine wood as deter-mined by the modulus of rupture (MOR) values. However, wood elasticity was affected with impregnated specimens showing higher modulus of elasticity (MOE) values than the untreated.

  • 115.
    Birbilis, Dimitrios
    et al.
    Technological Educational Institute of Thessaly, Greece.
    Karastergiou, Sotirios
    Technological Educational Institute of Thessaly, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Kakavas, Konstantinos
    Technological Educational Institute of Thessaly, Greece.
    Tsioukas, Thomas
    Technological Educational Institute of Thessaly, Greece.
    Properties of pine (Pinus nigra) and beech (Fagus sylvatica) wood impregnated with hot rape oil and surface treated with turpentine2014In: New Materials and Technologies in the Function of Wooden Products: Proceedings / [ed] Ivica Grbac, Faculty of Forestry , 2014, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The objective of this study was to examine oil-retention, adsorption, swelling and tensile strength of lap joints of wood treated with hot rape oil. Wood specimens of two species (Fagus sylvatika and Pinus nigra) were impregnated in a steel vessel using the empty cell process (Lowry method). Several impregnated specimens were additionally surface treated with turpentine. Rape oil retention ranged between 124 and 189 kg/m3 for pine wood specimens and between 187 and 285 kg/m3 for beech wood specimens. For both species, the impregnated specimens had an adsorption of about 20%, while the untreated near 60%. Total swelling of specimens was not affected by the impregnation but the rate of swelling was decreased. The impregnated specimens had a little lower tensile strength mostly when glued with polyurethane (PU). Surface treatment with turpentine slightly improved tensile strength of lap joints.

  • 116.
    Björnberg, Jonatan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    A Comparison of Non-Destructive Techniques to Discover Defect Finger Joints in Furniture2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this study has been to investigate the possibilities to identify lack of glue in finger joints by checking different non-destructive techniques. Specifically, this study puts emphasis on finding a method suitable for an automated and fast industry production line of home furnishing products. The methods investigated are of three main varieties:

    • Sound/vibration
    • Thermography
    • Tomography

    The most promising method was the high-power ultrasound thermography. This method is fast and reliable, but more research is needed. It is necessary to find out if the thermography waves can penetrate deep enough. Another possible method is computed tomography. This method can take a lot of time, but the speed of scanning depends on the accuracy demanded.

  • 117.
    Blom, Åsa
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Schauerte, Tobias
    Linnaeus University, Faculty of Technology, Department of Mechanical Engineering.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Utomhuskonstruktioner i trä: några erfarenheter från byggnation i trä av flerbostadshus2017Other (Other academic)
    Abstract [sv]

    Användandet av materialet trä i produkter är ett lån från naturen som förr eller senare genom nedbrytning av vedsubstansen ska återföras till det naturliga kretsloppet. Avseende användningen av solitt trä i produkter bestäms tidsperioden innan återföringen till naturen av produktens konstruktion och trämaterialet i sig självt i relation till den omgivande miljön samt användningen och hanteringen av produkten. En produkts förmåga att motstå, eller behålla sina egenskaper trots dessa yttre påfrestningar benämns dess beständighet.

  • 118.
    Blomqvist, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Laminated Veneer Products: Shape Stability and Effect of Enhanced Formability on Bond-Line Strength2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis concerns two aspects of the manufacture of laminated veneer products (LVPs). The first aspect is related to the possible improvement of the shape stability of LVPs, and the second has its starting point in the modification of the veneer for enhanced formability as well as the question of whether and how these modifications affect the bond-line strength.

    LVPs are veneers bonded with adhesive into predetermined shapes, mostly for the production of furniture and interior fittings. Since any deviation from the intended shape is a problem for both manufacturer and customer, various studies have sought to evaluate the influence of different materials and process parameters on shape stability. Parameters studied have included wood species (beech and birch), an adhesive system based on urea formaldehyde, the adhesive distribution on the veneer, climate, moisture content and fibre orientations of the veneers, as well as the orientation of the individual veneers in a multiply.

    Manufacturers of LVPs must consider some basic facts about wood in orders adequately to provide shape-stable LVPs to customers. Wood emits and absorbs moisture in relation to the surrounding climate, and this can lead to shrinkage and swelling. Such moisture induced movements differ in the wood’s different directions, and the magnitude is specific for the species. A thorough understanding of this is the basis for achieving shape-stable LVPs.

    Symmetry is defined in this thesis such that the veneer properties are balanced in the laminate. This means that opposite veneers on either side of the centre veneer have similar characteristic. An LVP will become distorted if the veneers are asymmetrically oriented before the press. Deviation from the desired shape can be small immediately after the pressing, but it may increase significantly with moisture content (MC) variations. Asymmetry may result when veneers with different fibre orientations are included in the laminate or when the veneers are placed asymmetrically. It may also occur if veneers with different MCs are bonded together asymmetrically. One aggravating factor is that the lathe checks that are introduced when the veneers are peeled or sliced from the log affect the shape stability. In 3-ply crosswise-oriented plywood, the veneer surfaces on which the lathe checks occur should be oriented in the same way for high shape stability.

    Based on existing knowledge, the production of shape-stable LVPs requires that the veneers are conditioned to a uniform MC and sorted with regard to fibre orientation and the side with lathe checks before bonding. End-user climates should govern the MC of the veneers and the moisture added with the adhesive during the process. Straight-grain veneers and symmetry should always be the goal.

    Moulding can cause stretching, i.e. strain, of the veneers depending on the curvature of the mould. To prevent the veneers from rupture, there are various ways to strengthen the veneers particularly in the transverse direction in which the veneer is weakest. However, tests have shown that these pre-treatments of veneers for enhanced formability can prevent the adhesive from penetrating the wood surface. It is therefore important to confirm that the pre-treatment does not affect the bond-line strength. 

  • 119.
    Blomqvist, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Shape stability of laminated veneer products: a review – defining and achieving shape stability2015In: International Wood Products Journal, ISSN 2042-6445, E-ISSN 2042-6453, Vol. 6, no 2, p. 89-95Article in journal (Refereed)
    Abstract [en]

    Laminated veneer products (LVPs) consist of veneers bonded together with an adhesive into a predetermined shape. Deviation from the intended shape is a problem for both manufacturers and customers of the final products. The shape stability of LVP depends on a variety of material and process parameters, and this review identifies several important factors that influence shape stability, the purpose being to find ways of decreasing distortion and improving shape stability so that product quality can be improved.

    The review ends to the following statements:

    The fibre orientation of the veneer strongly influences the shape stability of LVP. The products can show considerable distortion (particularly twist) if the fibre orientation of the veneer is oriented in an unsuitable way in the assembly before moulding.

    The effect of fibre orientation on shape stability can be very small directly after moulding, but it can increase considerably when the moulded product is subjected to a change in moisture content (MC). In general, a change in moisture leads to distortion. Moisture changes alone, however, result in a controlled distortion.

    The orientation of the loose and tight sides of the veneers in LVP affects the shape stability.

    An asymmetrical construction, coupled with different levels of moisture in the different veneers in an assembly before moulding, will result in poor shape stability of the product.

    The choice of wood species affects shape stability. Beech shows more distortion and poorer shape stability than birch.

    Based on existing knowledge to produce shape-stable LVP, the veneers should be conditioned to uniform MC and sorted with regard to fibre orientation and loose or tight side of the veneer before bonding. End-user climates should govern the veneers’ MC and added moisture from the adhesive during the process. Straight grain veneers and symmetry should always be sought.

    This review reveals several areas that need to be further clarified in order to achieve shape-stable LVP, for example the influence of adhesive, the distribution of pressure, temperature, stresses and strains during moulding and the development of numerical methods to better predict the final shape.

  • 120.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Berg, Sven
    Luleå University of Technology, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Sweden.
    Chipless Machining: Challenges in Manufacture of Laminated Veneer Products2015In: Proceedings of the 22nd International Wood Machining Seminar, IWMS 22: Volume 1 - Oral Presentations / [ed] Roger Hernández and Claudia B. Cáceres, Quebec City, Canada: Université Laval , 2015, p. 155-164Conference paper (Refereed)
    Abstract [en]

    A laminated veneer product (LVP) consists of veneers bonded together with adhesive under pressure into a predetermined shape and, in general, under increased temperature to shorten the curing time of the adhesive. The process is commonly used in furniture design to manufacture complex forms such as thin shells. In the industrial production of LVP and when the ready-for-use components are exposed to climate variations, rejection due to distortion of the laminates is a major problem. The shape stability depends on a variety of material and process parameters, and this study has focused on the influence of fibre deviation in a single veneer. Recent research on the shape stability of LVP and how distortion is influenced by various material and production parameters is presented. A finite-element model for LVP is introduced and the use of this model is exemplified by predicting the shape of a LVP with fibre distortion in a single veneer. The results show that it is possible to improve the shape stability of LVP if knowledge of various material and process parameters is implemented in the manufacturing process, and that a simulation based on a model of the wood material can be helpful in estimating the risk of an undesired deformation of the product.

  • 121.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology. RISE Research Institutes of Sweden, Sweden.
    Berg, Sven
    Luleå University of Technology, Sweden.
    Sandberg, Dick
    Luleå University of Technology, Sweden;Czech University of Life Sciences 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.

  • 122.
    Blomqvist, Lars
    et al.
    Trätek.
    Bronsek, Anders
    Trätek.
    Oscarsson, Jan
    Trätek.
    Svensson, Nils
    Trätek.
    Säkerhet och organisation vid CNC-maskiner i träindustrin2002Report (Other academic)
  • 123.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Landscheidt, Steffen
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Nilson, Henrietta
    Linnaeus University, School of Business and Economics, Department of Organisation and Entrepreneurship.
    Resource utilization in a production cell for laminated veneer products2017In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 13, no 4, p. 142-147Article in journal (Refereed)
    Abstract [en]

    The concept of productivity is often used to determine how well resources are used in an operation, and it is usually determined as the ratio of what is consumed in the production. Laminated veneer products are considered complicated products often taking complex shapes, using a raw material with high variation, and requiring machining processes that create scrap material that needs to be handled. Therefore, maintaining high productivity in industries producing such products may become challenging. This study reports on productivity measurements in a production cell consisting of an adhesive, pressing and a processing station. The study seeks to increase the understanding of production-related problems in this industry. This research has been based on productivity measurement as well as on interactive discussions between researchers and workers. Measurement of cycle times indicated bottlenecks in the processing cell. The discussion led via cycle times, processing residues and chatter marks to an examination of the foundation and rigidity of the CNC-machine in the processing cell. The study indicated that the performance of the CNC machine did not correspond to expectations. The machine was too weak to handle the required output in an efficient manner. Thus, there is a need to determine the performance expected before a machine or machine group is purchased. An update of the existing purchasing literature and its dissemination will support the crystallization of the purchasing process as a way forward to support the industry.

  • 124.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Basic knowledge of wood properties for improved performance of laminated Veneer products2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 549-556Article in journal (Refereed)
    Abstract [en]

    To ensure success in the production of laminated veneer products, it is necessary to acquire a sound basic understanding of the behaviour of the wood, and to understand the inherent reactions of wood to adhesive, heat, moisture, strain and stress. This can ensure an efficient wood utilization and promote the development of new processes and products that take advantage of the visco-elastic nature of wood.

     

    A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. In this study, we have examined how the performance of laminated veneer products can be improved through the implementation of basic knowledge of wood in the design and production process.

     

    The results show that the material and process parameters and storage in a changing relative humidity have a clear impact on distortion. Fibre orientation of the veneers in the moulded assembly was the most critical parameter to control. Fibre deviations mainly resulted in twist of the product. A moisture content in one veneer deviating from that of the rest of the veneers in the assembly before moulding resulted in distortion of the laminated veneer products both after moulding and during use. To decrease the negative effect of fibre orientation and moisture content on shape stability, the veneer should be straight-grained and well-conditioned to a moisture level adapted to the use of the final product. Special care should also be taken to orientate the veneers during assembly before moulding.

  • 125.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Jimmy
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Contact free measurement of complex shapes in the wood industry2011In: Mechano-chemical transformations of wood during THM processing / [ed] Parviz Navi and Andreas Roth, Biel, Switzerland: Bern University of Applied Sciencs, Architecture, Wood and Civil Engineering , 2011, p. 143-144Conference paper (Refereed)
    Abstract [en]

    There is an increasing need to update and correct information about product geometry in the wood manufacturing industry. Changes in machinery or personnel can be the cause of that need. Manual measurement takes time and diff erent ways of digitizing the geometry of the products have therefore been developed.

    In this study, two methods (3D-coordinate measurement and optical scanning) have been tested together in order to determine the position of a product in relation to the processing machine, and to optically scan the product geometry. The aim was to identify and evaluate methods to digitize product geometry into a CAD-model for the wood industry. Th e seat shell measured was fitted in the CNC-machine where the processing later would be performed.

    The methodology used has made it possible to create a CAD-model from the physical model. Based on the experience from this methodology, it would be recommended to continue by creating of a tool that minimizes the need for after processing, i.e. the adjustment of certain coordinates manually.

  • 126.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Jimmy
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Improving the performance of bended laminated veneer products2011In: Mechano-chemical transformations of wood during THM processing / [ed] Parviz Navi and Andreas Roth, Biel, Switzerland: Bern University of Applied Sciencs, Architecture, Wood and Civil Engineering , 2011, p. 147-148Conference paper (Refereed)
    Abstract [en]

    Laminated bending of veneers mean that dried, thin veneers or thin wood sheets are glued together under influence of pressure and eventually increased temperature. At the same time the product is given its desired shape, most often curved. This thermo hydro mechanical process offers several benefits. For example thick bends of small radiuses of any species of wood may be formed and poor quality wood containing knots, splits and other defects may be utilised. Laminated bends can usually be set more readily and made to conform better to the shape of the form than similar bends of solid wood. Further no softening treatment is generally required before the pieces are bent. However, there are also disadvantages e.g. more technical skill and better equipment are usually required than for solid wood bending. The presence of glue may be somewhat detrimental to the machines used for the final cleaning up of the bent pieces. Further the glue lines which are usually visible on the sides may be an aesthetical unappreciated effect [1],[2].The quality of the laminated bended veneer products are obtained as an interaction between the process, the veneers and the glue [3]. In industries designing and producing these products it is of interest to obtain better understanding of how processing- and material parameters affect the product quality. With an improved understanding of the material and processing parameters it may be possible to increase the efficiency of wood utilisation and promote the development of new processes and products that manipulate the viscoelastic nature of wood. In particular the possibilities to obtain narrower radius of curvature and better possibilities of bending in more than one plane would be advantageous.This study has focused on the moisture content (MC) and the grain angle orientation in the veneers. These two specific aspects were assumed to have a great influence on spring-back and distortions of the laminated bended veneer products. Spring-back and distortions were therefore studied in separate tests where MC and the grain angle orientation was varied separately in manufactured laminated bended wood products. After manufacturing the products were exposed to variations in humidity and temperature whereupon the spring-back and distortions were measuredThree tests were performed. For the first and the second test a seat shell was selected as test product, figure 1a. To the third test another product was selected, figure 1b. This product was a small bookshelf. The company producing this shelf had experienced large problems considering distortions of this product. Further the product was very simple in shape with only one bend and therefore suitable for measurements.In the first test the influence of MC of the veneers was investigated. In the second and third test the influence of grain angle of the veneers was studied.For the study veneers of birch and beech were selected in the production. For the first and third study only birch veneers were used. The veneers were initially conditioned to equilibrium moisture contents (EMC) according to setups in different test groups. For the first study a test group was also built up from veneers taken directly out of production to study the industrial conditions. The seat shells in this test group contained veneers conditioned to EMC 4 %, except for the surface veneers that had been stored in the production hall. The humidity and temperature conditions in this room corresponded to MC 7 %.The manufacturing of the products were performed in industrial conditions. In the tests the products were built up from a number of veneers and the studied factors were varied between the veneers in a controlled manner.The results from the first test showed that the MC of the veneers influenced the spring-back and the distortions. A large moisture gradient between veneers and especially unsymmetrical placements of these in the construction were especially critical. The results from the second and third tests showed that grain angle deviation has large effect on the distortions of the products. Even a small grain angle deviation as in study two (5°) resulted in large problems with distortions. The study also showed that when crossing two or more veneers with deviating grain angles there were cases when these faults interacted and multiplied the distortions. In production grain angle deviations can be a result of inaccurate placement of the veneers during pressing, incorrect cutting of the veneers, inherent from the growth of the tree or a combination of these factors. Deviations of the grain angle were, however, shown to have only small effects on spring-back.

  • 127.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet.
    Modification of surface veneer to reduce damage in laminated veneer products during manufacturing2014In: Final Cost Action FP0904, Recent Advances in the Field of TH and THM Wood Treatment, May 19-21, Skellefteå, Sweden: Book of abstracts / [ed] Dick Sandberg and Mojgan Vaziri, Luleå: Luleå tekniska universitet, 2014, p. 50-51Conference paper (Refereed)
  • 128.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Luleå University of Technology.
    Moisture-induced distortion of laminated veneer products2014In: Forest Products Society (FPS)  68th International Convention, 2014Conference paper (Refereed)
  • 129.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Moisture-induced distortion of laminated veneer products2013In: Proceedings of the 9th meeting of the Northern European network for wood science and engineering (WSE): September 11-12, 2013, Hannover, Germany / [ed] Christian Brischke & Linda Meyer, Hannover, Germany, 2013, p. 178-183Conference paper (Refereed)
    Abstract [en]

    Laminated veneer products consist of veneers bonded together with adhesive into a predetermined shape. Since wood is a hygroscopic material and also anisotropic by nature, laminated veneer products are especially shape-sensitive to changes in moisture content. A deviation from the intended shape is a problem for both the manufacturers and users of the final products and annually such deviations cause great economic losses in the manufacturing industry.

     

    To illustrate the influence of moisture on distortion and shape stability, studies have been performed in industrial conditions and in a laboratory environment. Veneers of beech and birch and a seat shell moulded from these veneers were used in the study. Distortion, i.e. spring-back, position and twist, has been determined directly after moulding and during subsequent moisture and drying cycles.

     

    The distortion follows more or less slavishly the changes in relative humidity around the product. The distortion is generally small directly after moulding but, after the laminates have been exposed to a variation in relative humidity, the distortion increases. Some of the problems of poor shape stability that may arise later in the bending process can be reduced if attention is paid to moisture content and fibre orientation already in the production of the veneer.

     

    To achieve good shape stability of laminated veneer products in practice, the following should be followed by the manufacture industry:

    • develop      cooperation with suppliers of veneer and set requirements of veneer with regard      to deviation of the fibre orientation, and require that the veneer be dried      and conditioned to a moisture content consistent with production,
    • control      incoming veneers with respect to fibre orientation and moisture content,
    • plan warehousing      of veneers and ensure adequate conditioning, and
    • consider      the orientation of the veneers and the species.
  • 130.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Shape stability of laminated veneer products: How to decrease the negative effects of fibre deviation?2013In: Forest Products Society (FPS)  67th International Convention, Madison: Forest Products Society , 2013Conference paper (Refereed)
    Abstract [en]

    A shortcoming of the laminated bending process is that the products may become distorted after moulding and during use. Annually, significant financial losses have incurred in the furniture and interior design industries as a result of distorted products. In this study, we have examined the influence of deviation of fibre orientation of individual veneers on distortion of a moulded shell to find ways to improve shape stability of laminated veneer products.

    Ninety cross-laminated shells, consisting of 7 veneers of Birch (Betula pubescens Ehrh.) with a total thickness of 3.6 mm, were studied. The in-plane dimensions of the veneer were 400x660 mm. All the veneers were straight-grained, but to simulate deviation in fibre orientation some of the individual veneers were oriented 7 degrees relative to the main orientation of the other veneers in the laminate. Distortion was determined directly after moulding and after storage in a changing relative humidity.

    The results show the well-known fact that deviation of fibre orientation of the veneers in the laminate influences the shape stability of the product. The results from this study, however, also show how the placement of the abnormal veneers in the laminated veneer products influences the degree of distortions. From this basic knowledge some improvements for production of laminated veneer products were suggested.

  • 131.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Shape stability of THM-processed laminated veneer products glued with bio-based adhesive systems2013In: Evaluation, processing and predicting of THM treated wood behaviour by experimental and numerical methods / [ed] Carmen-Mihaela Popescu and Maria-Cristina Popescu, Iasi, Romania, 2013, p. 99-100Conference paper (Refereed)
  • 132.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Luleå University of Technology.
    Veneer modification for improved formability when moulding laminated veneer products2014In: Forest Products Society (FPS)  68th International Convention, 2014Conference paper (Refereed)
  • 133.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Nilson, Henrietta
    Linnaeus University, School of Business and Economics, Department of Organisation and Entrepreneurship.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Landscheidt, Steffen
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Downtime causes in a production cell for laminated veneer products2017In: 23rd International Wood Machining Seminar Proceedings / [ed] Marcin Zbiec and Kazimierz Orlowski, Warsaw, Poland: The Polish Chamber of Commerce of Furniture Manufacturers , 2017, p. 28-35Conference paper (Refereed)
    Abstract [en]

    Productivity is often used to determine how well resources are used for an operation. Most often, the ratio of what is produced to what is required to produce it determines productivity. Laminated veneer products are considered complicated products often with complex shapes, a raw material with high variation, and machining processes that create scrap materials that need to be handled. Therefore, keeping a high productivity in the industries producing such products may become challenging. This study reports productivity measurements in a production cell consisting of an adhesive, pressing and processing station. The study seeks to increase understanding of production-related problems in this industry. The research has been using productivity measurement as well as interactive discussions between researchers and workers.

    Measurement of downtime causes were made for 20 days, for a total of approximately 300 hours. The production cell had 1,299 minutes of stops. Of those, 450 minutes were one-time events. The rest were intermittent disturbances. Many of them could be explained by the dust-laden air and processing residues but were also related to veneer and adhesive. There is a need for determining material and processing parameters; however, the first priority is cleaning the factory.

    From a social perspective, some other issues must be added to the discussion of this paper. First and foremost, the business has gone through a transformation from a family business to a privately held firm. From the non-family employee’s view, this is a huge change. This has resulted in unclear roles and responsibilities within the company, which has also affected the productivity of the company.

  • 134.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Pfriem, Alexander
    Eberswalde University for Sustainable Development, Germany.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Temporary buildings in reusable lightweight material design2016In: Proceedings of the 2016 World Conference on Timber Engineering (WCTE), Vienna: Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    There is a growing need and market for temporary buildings for various purposes, including largeconstruction projects in the tourism and events sectors or in civil protection. This paper gives an overview about the useof reusable lightweight materials in temporary buildings. Based on a project proposal submitted to the 7th framework, anew concept of temporary buildings is proposed. This concept combines the advantages of the premanufacturing of asmall number of parts and wooden components and a flexible and modular erection of the temporary building. Thefocus is on fast establishment with a maximum of three persons. A flexible and modular extension is possible.Assembling and disassembling the individual components with novel connect systems, adapted from the furnitureindustry, is proposed.This project aims to bring these concepts into new temporary buildings with new, reusable, and flexible lightweightdesign.

  • 135.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Rowell, Roger
    University of Wisconsin-Madison.
    Bio-based adhesives at laminated veneers2012In: Proceedings of the 8th meeting of the Northern European Network for Wood Science and Engineering (WSE) / [ed] Antanas Baltrušaitis and Kristina Ukvalbergiené, Kaunas, Lithuania, 2012, p. 221-225Conference paper (Refereed)
  • 136.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Luleå University of Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Influence of veneer orientation on shape stability of plane laminated veneer products2014In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 9, no 4, p. 224-232Article in journal (Refereed)
    Abstract [en]

    One of the most important quality aspects of a laminated veneer product is its shape stability under changing relative humidity (RH). This study aimed to establish an understanding of how the orientation of individual veneers in the laminate, i.e., orientation according to fibre orientation and orientation of the loose (the side with ‘lathe checks’) or tight side of the veneer, affects the shape stability. Three-ply laminates from peeled veneers of beech (Fagus sylvatica L.) were studied. The four types of laminate were the following: loose sides of all veneers in the same direction (cross and parallel centre ply) and loose sides of the outer veneers facing inward (cross and parallel centre ply). Four replicates of each type yielded 16 samples. The samples were exposed to RH cycling at 20% and 85% RH at 20°C, and the shapes of the samples were determined. The shape stability was influenced by the veneer orientation. Laminations with the middle veneer perpendicular to the top and bottom veneer (cross-laminated) showed the best shape stability, especially when the loose sides of the veneers were oriented the same direction. In parallel-laminated veneers, the laminates with opposite directions of the loose sides in the two outermost veneers showed the best shape stability. The major explanation of the behaviour of the laminates is that the loose side expanded more than the tight side from the dry to the humid climate, which was shown by optical 3D deformation analysis (ARAMISTM). After RH cycling, the laminates with cross plies showed visible surface checks only when the tight side was facing outwards.

  • 137.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sterley, Magdalena
    SP Technical Research Institute of Sweden.
    Sandberg, Dick
    Luleå University of Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    The effect of veneer modification on the bond-line strength in laminated veneer products2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 43-49Article in journal (Refereed)
    Abstract [en]

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

  • 138.
    Blomqvist, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sterley, Magdalena
    SP Wood Technology.
    Sandberg, Dick
    Luleå tekniska universitet, Luleå University of Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    The influence of veneer modification on adhesive bond strength2014In: Proceedings of the 10th meeting of the Northern European network for wood science and engineering (WSE) / [ed] Peter Wilson, Edinburg, Scotland, 2014, p. 150-155Conference paper (Refereed)
  • 139. Blumer, Samuel
    et al.
    Niemz, Peter
    Serrano, Erik
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Gustafsson, Per Johan
    Moisture induced stresses and deformations in parquet floors: An experimental and numerical study2009In: Wood research, ISSN 1336-4561, Vol. 54, no 1, p. 89-101Article in journal (Refereed)
    Abstract [en]

    The indoor climate in buildings has changed in the last decade due to more efficient climatic systems, floor heating systems and larger open floor areas with more natural light. All this has induced increasing ranges of relative humidity between different seasons. Also with decreasing relative humidity (in the winter 30-50% RH, in the summer 70-90% RH), floor-heating systems increase the temperature in wooden parquet planks for example. Such variations can result in troublesome deformations, delamination of the surface layer and development of cracks in the parquet flooring boards. Sometimes there is only deterioration of the appearance but the durability of the flooring system can also be reduced. Many laboratory tests have to be done before reaching an optimal design of the parquet elements. Due to high coasts and time constraints of experiments, other supplementary research methods should be tested and evaluated. The articles' main objective was to increase understanding of the behaviour of parquet floors exposed to different climatic conditions using numerical calculation. The use of the finite element models provides options for design purposes of wood flooring systems. Several finite element models for adequate design have been created, tested and applied. After calibration and validation of the calculation method, parameter studies on the influence of material properties, geometry of the parquet floors and the long-term behaviour of the wood and glue line were performed. The results show a strong relation between material and geometry choice on the deformation, for example the gap opening and on the stress distribution in glue line, which can induce delamination of the surface layer and distortional effects of the parquet boards

  • 140.
    Blyberg, Louise
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Timber/Glass Adhesive Bonds for Structural Applications2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Timber with its natural appearance and glass with its transparency may be appealing material for architects and users of modern buildings. Glass is a brittle material, but it is about six times stiffer than timber. Combined appropriately, the materials could form different types of composite products, e.g. beams or shear walls, that can be included in the load-carrying structure of buildings. e knowledge on load- carrying timber/glass components is limited. e intention of this research has been to contribute to the knowledge required for the industry to be willing to produce timber/glass components for the market.

    The thesis includes experimental testing accompanied with complementary nite element simulations, which provide more details and information about the test results. Tests were performed on small-scale specimens with a bond area of 800 mm2 as well as on I-beam and shear wall prototypes. For the small-scale specimens tested in standard climate, three different adhesives were used for the bond line between timber and glass. ese specimens were tested in both tension and shear. In addition, one of the adhesives was used for small-scale shear specimens which were exposed to different humidity levels before the tests were performed. e 4 m long I-beam prototypes designed with a web of glass and wooden anges were tested in four- point bending. e shear wall prototypes were tested by applying either a vertical load, a horizontal load or a combination of these, all being applied in the plane of the shear wall.

    Of the three adhesives used in the small-scale testing, an acrylate adhesive had the largest strength, both in tension and in shear. e study on the effect of humidity was performed with this adhesive. is study indicates that the adhesive properties do not change dramatically in indoor climate. is adhesive was also used for twelve of the fourteen tested I-beams. e results from the beams show that a signi cant redundancy is obtained; the load at the nal failure was around 240 % of the load when the rst crack in the glass web appeared. e shear walls were glued using the acrylate adhesive and for a few cases a 2-component silicone based adhesive. e results from the shear wall tests showed the shear wall to behave in a much more brittle manner, without any noticeable redundancy.

  • 141.
    Bonarski, Jan T.
    et al.
    Polish Academy of Sciences, Poland.
    Kifetew, Girma
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olek, Wieslaw
    Poznań University of Life Sciences, Poland.
    Effects of cell wall ultrastructure on the transverseshrinkage anisotropy of Scots pine wood2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 4, p. 501-507Article in journal (Refereed)
    Abstract [en]

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

  • 142. Braovac, Susan
    et al.
    Fackler, Karin
    Bader, Thomas K.
    Ters, Thomas
    Chemical Composition of the Archaeological Oak Wood from the Oseberg Ship2011In: Cultural Heritage Preservation.EWCHP - 2011: Proceedings of the European Workshop on Cultural Heritage Preservation. Berlin, Germany, September 26 to 28, 2011, Fraunhofer IRB Verlag, 2011, p. 156-163Conference paper (Refereed)
  • 143.
    Briggert, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Hu, Min
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Tracheid effect scanning and evaluation of in-plane and out-of-plane fibre direction in Norway spruce using2018In: Wood and Fiber Science, ISSN 0735-6161, Vol. 50, no 4, p. 411-429Article in journal (Refereed)
    Abstract [en]

    Local fiber direction is decisive for both strength and stiffness in timber. In-plane fiber direction on surfaces of timber can be determined using the so-called tracheid effect which is frequently used in both research and industry applications. However, a similar established method does not exist for measuring the out-of-plane angle, also known as diving angle. The purposes of this article were to evaluate if the tracheid effect can also be used to determine, with reasonable accuracy, the out-of-plane angle in Norway spruce and to verify an existing mathematical model used to calculate the fiber direction in the vicinity of knots. A newly developed laboratory laser scanner was applied for assessment of fiber directions in a single Norway spruce specimen containing a knot. It was assumed that the specimen had a plane of symmetry through the center of the knot, and by splitting the specimen through this plane into two parts, it was possible to make measurements on orthogonal planes. The results showed that the out-of-plane angle could not be determined with very high accuracy and the difficulties related to this objective were analyzed. Regarding the mathematical model of fiber direction in the vicinity of a knot, fiber directions calculated on the basis of this model agreed well with experimentally obtained fiber directions, but successful application of the model requires that the geometry of the knot is known in detail.

  • 144.
    Briggert, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Three-dimensional modelling of knots and pith location in Norway spruce boards using tracheid-effect scanning2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 5, p. 725-739Article in journal (Refereed)
    Abstract [en]

    Knots and the orientation of fibres in timber are decisive for the stiffness and strength of boards. Due to large property variations between members, strength grading is necessary. High resolution information of the orientation of fibres, both on surfaces and within members, would enable development of more accurate grading methods than those available today. A step towards three-dimensional (3D) models of the fibre orientation of the entire board volume is the establishment of 3D knot models based on scanning. The light from a dot laser illuminating the surface of a softwood board will, due to the tracheid effect, spread more along the fibres than across resulting in the dot entering an elliptical shape. In this investigation both the shape of the ellipse and the direction of its major axis were used to estimate the 3D fibre orientation on board surfaces. Knot surfaces were identified where the angle between the estimated 3D fibre direction and an approximated direction of the board’s pith exceeded a threshold value. By means of algorithms based on polar coordinates, knot surfaces which belonged to the same physical knot visible on different sides of the board were identified and as a result the position, orientation and volume of each knot were determined. Based on this information, a more accurate position of the board’s pith along the board was calculated. The established models showed good agreement with physical boards. The models constitute a promising starting point for further development of strength grading methods based on tracheid-effect scanning.

  • 145.
    Carlsson, Peter
    et al.
    Mid Sweden University.
    Esping, Björn
    Mid Sweden University.
    Dahlblom, Ola
    Lund University.
    Ormarsson, Sigurdur
    Lund University.
    Söderström, Ove
    Royal Institute of Technology.
    Optimization, a tool with which to create an effective drying schedule1998In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 52, no 5, p. 530-540Article in journal (Refereed)
    Abstract [en]

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

  • 146.
    Carlsson, Staffan
    et al.
    KTH Träteknologi.
    Eskilander, Stephan
    KTH Träteknologi.
    Sandberg, Dick
    KTH, Träteknologi.
    Utvärdering av deplacementmetod med vatten för bestämning av träets torrdensitet.1996Report (Other academic)
    Abstract [en]

    Evaluation of the deplacement method with water for determination of dry wood density.

    by Staffan Carlsson, Stephan Eskilander and Dick Sandberg

    Abstract

    A new method (SP-method) for determination of wood density at 12 % moisture content has been developted at the Swedish National testing and Research Institute (SP). The method is a futher development of the deplacement method with water as. The volume of the specimens is determined with use of Archimeds principle. The specimen is immersed in water and a computer program compensate for errors in the measurement as a result of wateruptake in the specimen.

    This investigation describes the correlation between the dry density of wood, determined by the SP-method and a "traditional" method. Traditional method means that the dimensions of the specimen are measured with a slide-calliper in order to calculate the volume of the specimen. The test materials were taken from Scots pine and Norway spruce with dimension 40 x 60 x 120 mm.

    The results show a difference less than 3 % between dry density determined by the two methods. The correlation coefficient (R2) was 0.99 when linear regression was used. Repetition test showed mean deviation of 0.2 % when dry density for same specimens were determined two times with the SP-method.

  • 147.
    Cristina, Simón
    et al.
    Technical University of Madrid, Spain.
    Francisco, García Fernández
    Technical University of Madrid, Spain.
    Luis, García Esteban
    Technical University of Madrid, Spain.
    Paloma, de Palacios
    Technical University of Madrid, Spain.
    Hosseinpourpia, Reza
    University of Göttingen, Germany.
    Carsten, Mai
    University of Göttingen, Germany.
    Comparison of the saturated salt and dynamic vapor sorption methods in obtaining the sorption properties of Pinus pinea L.2017In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 75, no 6, p. 919-926Article in journal (Refereed)
    Abstract [en]

    Several methods are available for obtaining the sorption isotherms of wood. Among these, the saturated salt and dynamic vapor sorption methods are the most frequently used  ones. For the first time, the hygroscopic response of wood obtained using these two methods is compared. This is done by determining the 35 and 50°C adsorption isotherms of juvenile and mature wood of Pinus pinea L. The hygroscopic behavior of the two types of wood is different, as the mature wood has a higher moisture content than the juvenile wood in the isotherms studied. Comparison of the static saturated salt method and dynamic vapor sorption shows few significant differences between the equilibrium moisture content obtained by each method during the adsorption process, both in a point by point comparison and in the comparison of quadratic polynomial forms of the Guggenheim Anderson-de Boer model. Moreover, in both methods the point of relative humidity from which multilayer sorption predominates over monolayer sorption is similar.

  • 148.
    Dahlblom, O.
    et al.
    Lund University.
    Ormarsson, Sigurdur
    Lund University.
    Petersson, H.
    Lund University.
    Simulation of wood deformation processes in drying and other types of environmental loading1996In: Annales des Sciences Forestieres, ISSN 0003-4312, E-ISSN 1878-6545, Vol. 53, no 4, p. 857-866Article in journal (Refereed)
    Abstract [en]

    Deformation processes in wood exposed to drying and other types of environmental loading are simulated by use of the finite element method. In the material model applied, the orthotropic structure of the wood material is considered. The differences of properties in the longitudinal, radial and tangential directions for stiffness parameters as well as for moisture shrinkage parameters are taken into account. As an illustration of possible application areas, the deformation development of boards during drying is simulated. In the analyses, the influence of spiral grain and the variation of wood properties with the distance from the pith are considered. The simulation yields information about unfavourable deformations that develop during the drying process., Le processus de déformation du bois exposé au séchage et autres types de charges environnementales est simulé par la méthode des éléments finis. La structure orthotropique du bois est prise en considération sur le modèle de matériel utilisé. Les différences existant au niveau des propriétés des directions longitudinales, radiales et tangentielles sont prises en compte pour les paramètres de rigidité et de contraction par humidité. Une des possibilités du champ d'applications est illustrée par le fait que l'évolution de la déformation des planches pendant le séchage est simulée. À l'échelon des analyses, l'influence du grain spiral et la variation des propriétés du bois avec la distance depuis la moelle sont pris en compte. La simulation permet d'obtenir des informations concernant l'évolution des déformations défavorables pendant le processus de séchage.

  • 149. Dahlblom, Ola
    et al.
    Lindemann, Jonas
    Ormarsson, Sigurdur
    Software for Numerical Simulation of Drying Induced Deformation of Wooden Products2003In: 8th International IUFRO Wood Drying Conference, TRANSILVANIA University of Brasov, Faculty of Wood Industry , 2003, p. 45-50Conference paper (Refereed)
    Abstract [en]

    A previously developed computational model for 3D finite element simulations of wood during moisture changes is in the present work provided with a special-purpose graphical user interface. The software is designed to use a personal computer for the graphical user interface and to have possibility to use distributed computational resources for the simulation.

  • 150. Dahlblom, Ola
    et al.
    Ormarsson, Sigurdur
    Petersson, Hans
    Prediction of deformations by an extended two-dimensional formulation1996In: Quality wood drying through process modelling and novel technologies / [ed] Alain Cloutier, Yves Fortin, 1996, p. 69-76Conference paper (Refereed)
1234567 101 - 150 of 606
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