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  • 1. 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)
  • 2.
    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.

  • 3.
    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.

  • 4.
    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.

  • 5.
    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.

  • 6.
    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)
  • 7.
    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)
  • 8.
    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.
  • 9.
    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: an experimental study of the influence on distortion of some material and process parameters2013In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 3, p. 198-211Article in journal (Refereed)
    Abstract [en]

    Laminated bending of veneers is a common used and important process for manufacture of components primarily for furniture and interior purposes. According to the use, such products are in general very sensitive to variations in the intended shape, i.e. distortion can be of great problem and more or less destroy the use of the final product. The most critical mode of distortion is twist, but also other changes in shape may be of interest to keep low. The causes to distortion of laminated bended veneer products can be of material (veneer, adhesive and the combination of these), design, processes and climate nature and there is a challenge to know which parameters which are of major importance for distortion, both directly after moulding and when the products are in use.

    In this study, the influence of type of UF-adhesive hardener, i.e. liquid or powder, water content of adhesive, adhesive distribution, variation of moisture content of glued veneers, and fibre orientation of veneers, on twist and position for a 3D-veneer construction (a chair seat shell) has been studied. Distortion, i.e. twist and position, has been determined directly after moulding and after moisture cycling. The moisture cycling was to simulate and accelerate conditions that the shells are subjected in use. The aim of the work is to study how the above mentioned material and process parameters influence the shape stability of the products.

    The results show that the climate, i.e. how a certain level of temperature and relative humidity influence the moisture content of the moulded product, has a clear impact on the distortion of the product in use. An increase in moisture content results in a significant increase in distortion and vice versa. The level to which the moulded products distort during climate variation can be controlled through controlling material, design and process parameter during moulding. Of the studied parameter mentioned above, a deviation in fibre orientation of the veneers in the moulded assembly is the most critical parameter to have under control to minimize distortion. The fibre deviation mainly results in an increase in twist. A high moisture content of a veneer vis-à-vis the rest of the veneers in the assembly before moulding, will result in increased position and twist of the moulded product in use. The difference of moisture content between veneers and the position of veneers with high moisture content in the assembly will influence the level of distortion. Other studied parameter also influences the distortion to a lesser extent and can in these cases be related to the moisture distribution in the mouldings.

  • 10.
    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.

  • 11.
    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)
  • 12.
    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)
  • 13.
    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.
    Kifetew, Girma
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    The influence of individual veneer orientation on the shape stability of planar lamination2012In: Current and Future Trends of Thermo-Hydro-Mechanical Modification of Wood. Opportunities for new markets? / [ed] Mathieu Pétrissans and Philippe Gérardin, Nancy, France, 2012, p. 160-162Conference paper (Refereed)
  • 14.
    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.

  • 15.
    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.

  • 16.
    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)
  • 17.
    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.

  • 18.
    Dvinskikh, Sergey V.
    et al.
    Royal Institute of Technology KTH, Division of Physical Chemistry and Industrial NMR Centre, SE-100 44 STOCKHOLM, .
    Furó, István
    Royal Institute of Technology KTH, Division of Physical Chemistry and Industrial NMR Centre, SE-100 44 STOCKHOLM, .
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Söderström, Ove
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Moisture content profiles and uptake kinetics in wood cladding materials evaluated by a portable nuclear magnetic resonance spectrometer2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 3, p. 119-127Article in journal (Refereed)
    Abstract [en]

    We have evaluated the capability of nuclear magnetic resonance (NMR) technology based on small portable magnets for in situ studies of the local moisture content in wood. Low field and low resolution 1H NMR with a unilateral permanent magnet was used to monitor and map the moisture content of wood cladding materials of various types in a spatially resolved manner. The results show that portable NMR equipment based on small open-access permanent magnets can be successfully used for non-invasive monitoring of the moisture content in various extended wood specimens. The moisture content was measured with a depth resolution of 0.2 mm and a maximum penetration depth of 3 mm. This makes the technique suitable for e.g. in situ local moisture content measurements beneath a coating layer in the claddings and it is also possible to relate the moisture level to specific properties of the wood material.

  • 19.
    Eliasson, Lars
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    A case-study of single-family timber housing in Sweden and its wood material processing costIn: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280Article in journal (Refereed)
  • 20.
    Eliasson, Lars
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Trähusföretag tappar fördel i slarvig tillverkning.2011In: Husbyggaren, ISSN 0018-7968, no 7, p. 24-27Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    BYGGMETODER Ska trä öka sin konkurrenskraft måste trähusföretag och virkesleverantörer bli bättre på att både ställa och uppfylla kravspecifikationer. Idag kan materialspill och felleveranser uppgå till närmare en femtedel av virkeskostnaden.

    Trähusbranschen står inför ett antal utmaningar. Avgörande är att kunna producera attraktiva bostäder till en kostnad som inte är högre än att människor har råd.

    Trähusföretagen utnyttjar inte fullt ut material och metoder som är anpassade för en effektiv produktion av hus i fabrik. I den kontexten får träets miljöfördelar en underordnad betydelse i konkurrensen med andra mindre miljömässigt uthålliga material.

  • 21. Fransson, Jonas
    et al.
    Olsson, Axel
    Witten, Thomas
    Blom, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick (red)
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Svenska barr- och lövträd: - Andvändning och anatomi2007Report (Other academic)
    Abstract [en]

    Swedish softwoods and hardwoods – use and anatomy describe properties

    and macro- and microscopic structures for the most common species in

    Sweden. The softwood species described are pine, spruce and juniper. The

    hardwoods are birch, aspen, alder, beech, oak, ash and maple. The

    physical properties are placed in order of precedence between the different

    species, so that they easily can be compared with each other. Furthermore,

    some examples are given on uses for each species. The work is based on a

    literature survey of Swedish and international literature as well as on own

    studies of wood at a microscopic level. All the species (except aspen, alder

    and maple) are presented with our own pictures taken in a microscope.

    In the first part, the structures of the trees at a macroscopic level are

    described. Macroscopic structures that are described are for example rays,

    annual rings and vessels. This part also describes different cell types and

    the anatomy and chemistry of the cell. In the next part, a collection of

    facts about each species is included. A separation of soft- and hardwood is

    made, and the hardwoods are divided in diffuse-porous, semi-ring-porous

    and ring-porous species.

  • 22.
    Hemmilä, Venla
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Trischler, Johann
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Luleå University of Technology.
    Bio-based adhesives for the wood industry: an opportunity for the future?2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 118-125Article in journal (Refereed)
    Abstract [en]

    This paper reviews the use of some of the new technologies that may be implemented in bio-based adhesives, e.g. carbohydrate polymers, proteins, tannins, lignins, and vegetable oils.

    In order to take a part of the market share, an adhesive should have low production costs, fulfil the environmental and health standards and give better properties than conventional synthetic adhesives. For large-volume wood products such as chipboard, it is essential to develop adhesives that enable the product to be cost competitive. Bio-based adhesives that are available and affordable for the wood industry suffer from three main problems: low moisture resistance, low reactivity and poor adhesive properties, and in several cases they are expensive compared to synthetic adhesives.

  • 23.
    Hemmilä, Venla
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Trischler, Johann
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Lignin: an adhesive raw material of the future or waste of research energy?2013In: Northern European Network for Wood Science and Engineering (WSE): Proceedings of the 9th meeting, September 11-12, 2013, Hannover, Germany / [ed] Brischke, Christian & Meyer, Linda, Hannover: Leibniz Universität , 2013, p. 98-103Conference paper (Refereed)
    Abstract [en]

    Lignin has been studied as an adhesive for more than 100 years, but there are only a few industrial applications. The reason for the current interest is the high availability and low price of lignin. Lignin is the main by-product of paper pulping processes and is typically burned as fuel. Being the natural glue in plants and having a phenolic nature makes lignins an attractive replacement for wood adhesives.

     

    An adhesive system for wood composites consisting mainly of lignin has yet to be developed. Lignin has less reactive sites in the aromatic ring than phenols, and the steric effects caused by the macromolecular structure further hinder its reactivity. The low reactivity leads to slow curing and causes problems in applications where the curing speed is a critical parameter. Modifications such as phenolation, methylolation, and demethylation have been shown to have a positive impact on the reactivity of lignin.

     

    This paper presents properties of particle boards produced using unmodified and oxidized Kraft lignin adhesives. The paper also describes recent research relating to lignin as a base for wood adhesive and discusses the possibilities for future research.

     

    The boards produced with unmodified and modified lignin adhesives under equivalent pressing conditions performed poorly compared to the reference board made with standard UMF adhesive. Oxidation at the correct pH level improved the adhesion of the boards compared with those based on unmodified lignin. Efforts to produce an industrially viable lignin-based adhesive system will continue, and promising combinations of modifications and alternative hardeners are being studied.

  • 24.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH.
    Diagrambilaga till Rapport KTH-Trä TRITA-TRÄ R-95-12.1995Report (Other academic)
  • 25.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH Träteknologi.
    Kvistars frekvens, form och beskaffenhet i trekantprofil av furu (Pinus silvestris L) och gran (Picea abies Karst).1995Report (Other academic)
    Abstract [en]

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

    by

    Hans

    Holmberg Dick Sandberg

    Abstract

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

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

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

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

  • 26.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH Träteknologi.
    Structure and Properties of Scandinavian Timber1997Report (Other (popular science, discussion, etc.))
  • 27.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Transportprocesser i trä.: Permeabilitet.1997Report (Other academic)
  • 28.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH, Träteknologi.
    Utvärdering av en ny ströläggningsmetod för stjärnsågad trekantprofil.1995Report (Other academic)
    Abstract [sv]

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

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

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

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

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

  • 29.
    Holmberg, Hans
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    KTH.
    Volym- och kvalitetsutbyte vid stjärnsågning.1996Report (Other academic)
    Abstract [en]

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

    by

    Hans Holmberg and Dick Sandberg

    Abstract

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

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

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

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

     

  • 30.
    Holmberg, Hans
    et al.
    KTH.
    Sandberg, Dick
    KTH.
    Volymutbyte vid tillverkning av furulimfog från stjärnsågad trekantsprofil.1997Report (Other academic)
    Abstract [da]

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

    by

    H.Holmberg

    D. Sandberg

    Abstract

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

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

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

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

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

  • 31.
    Johansson, Ingvar
    et al.
    KTH Träteknologi.
    Sandberg, Dick
    Kungliga Tekniska Högskolan (KTH), Träteknologi.
    Plastisk deformation hos trä utsatt för varierande fuktbelastning: Förstudie1994Report (Other academic)
  • 32.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Blomqvist, Lars
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Challenges using dielectric heating for THM processing of solid wood2013In: Evaluation, processing and predicting of THM treated wood behaviour by experimental and numerical methods / [ed] Carmen-Mihaela Popescu and Maria-Cristina Popescu, Iasi, Romania, 2013, p. 55-56Conference paper (Refereed)
  • 33.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Automatic sorting of sawn birch: Defect detection possibilities on sawn and planed wood surfaces2010In: Hardwood research and utilisation in Europe: New Challanges / [ed] Robert Nemeth and Alfred Teischinger, Sopron: University of West Hungary Press , 2010, p. 206-213Conference paper (Refereed)
    Abstract [en]

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

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

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

  • 34.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Improved use and production of hardwood with the PrimWood Method2010In: Broadleaved forests in southern Sweden: management for multiple goals / [ed] Magnus Löf , Jörg Brunet, Leif Mattsson och Mats Nylinder, Oxford: Wiley-Blackwell, 2010, Vol. 53, p. 51-59Chapter in book (Refereed)
  • 35.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Luleå University of Technology.
    Integrated use of product data for improved wood material utilization in the furniture and joinery production2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 321-327Article in journal (Refereed)
    Abstract [en]

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

     

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

     

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

     

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

  • 36.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Ny träteknik höjer värdet på lövskogen2008In: Ekbladet, ISSN 0283-4839, no 23, p. 24-27Article in journal (Other academic)
    Abstract [sv]

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

  • 37.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Preparation of wood with pulsed UV-laser ablation for characterisation of the wood structure2007In: Proceedings of Third International Symposium on Wood Machining, Presses polytechniques et universitaires romandes , 2007, p. 191-194Conference paper (Refereed)
    Abstract [en]

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

  • 38.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    The Concept of Value Activation II.: The PrimWood Method for improved properties of hardwood products.2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 53-59Conference paper (Refereed)
    Abstract [en]

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

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

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

  • 39.
    Johansson, Jimmy
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Volymutbyte vid tillverkning av kvistfria snickeriämnen och skivor med stående årsringar2005Report (Other academic)
    Abstract [en]

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

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

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

    Sawing, from log to dried wood             56 %

    Knot-free boards from Rectangle           75 %

    Knot-free panels from Rectangle (Panel) 52 %

    Knot-free boards from Triangle (Rhomb) 73 %

    Knot-free panels from Triangle (Prism)   53 %

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

  • 40.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Gustafsson, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Design of form stable and visually crack free edge-glued oak panels.2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 167-171Conference paper (Refereed)
    Abstract [en]

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

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

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

  • 41.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Gustafsson, Åsa
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Secondary interior wood products for manufacturing in Swedish hardwood sawmills2005In: Hardwood research and utilisation in Europe: new challanges / [ed] Bejo, L., Sopron: University of West Hungary , 2005, p. 162-166Conference paper (Refereed)
    Abstract [en]

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

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

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

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

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

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

  • 42.
    Johansson, Jimmy
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Söderström, Ove
    Sandberg, Dick
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Capillarity in hardwood: An important factor for hardwood market expansion2007In: The Beauty of Hardwood: Proceedings of third Conference on Hardwood Research and utilisation in Europe, University of West Hungary, Sopron , 2007Conference paper (Refereed)
    Abstract [en]

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

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

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

  • 43.
    Kifetew, Girma
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Nilsson, Jonaz
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Is it possible to constrain moisture movement of densified wood product mechanically?2011In: Mechano-chemical transformation of wood during THM processing / [ed] Navi, P. & Roth, A, Biel Switzerland: Bern University of Applied Sciencs, Architecture, Wood and Civil Engineering , 2011, p. 67-68Conference paper (Refereed)
    Abstract [en]

    Densification of wood in the transverse direction increases the density. One of the reasons for densifying wood is to produce high quality timber from timbers of low quality. However, densified wood shows an undesired behaviour, i.e. a tendency to return to its initial dimensions when it is subjected to heat and humidity, i.e. shape memory. There are several methods to overcome the problem of shape memory.

    This study uses a three-layered cross-laminated wood panel where one of the layers is of densified wood and the other two are of normal wood together these will mechanically restrain the shape memory of the densified layer.

    The study includes three stages:

    • Densification of clear wood in the radial direction
    • Manufacture of a three-layered cross laminated composite product with densified wood as a service layer
    • Testing of the shape stability when the composite was subjected to variations relative humidity (40-85 % RH at 20°)

    The result of this study reveals the significance of service to bottom layer thickness ratio on the shape stability of the cross laminated composite. Consequently, the performance and the shape stability of the cross laminated composite were significant when the service to bottom layer thickness ratio increases. Therefore, it appears feasible to disclose the appreciable degree of shape stability, hardness and wear resistance of the product. Accordingly, cross laminated composite can be considered as one of the promising mechanical methods for improving moisture movement of densified wood product.

  • 44.
    Kifetew, Girma
    et al.
    KTH, Träteknologi.
    Sandberg, Dick
    KTH, Träteknologi.
    A Comparsion of Dot-counting and Mercury immersion Methods for Determing Density.1996Report (Other academic)
    Abstract [en]

    This paper describes two wood density determination techniques, one using the dotcounting and the other Mercury immersion and discuses the correlation between the methods. The paper includes also a short literature survey on some other wood density determination methods.

  • 45.
    Kifetew, Girma
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Kungliga Tekniska högskolan (KTH).
    Material damage due to electron beam during testing in the environmental scanning electron microscope (ESEM).2000In: Wood and Fiber Science, ISSN 0735-6161, Vol. 32, no 1, p. 44-51Article in journal (Refereed)
    Abstract [en]

    This study describes the development of cell-wall damage, i.e., the creation of cracks across or in the vicinity of pits during the testing of twenty microtomed spruce (Picea abies karst.) samples in the Environmental Scanning Electron Microscope (ESEM). Samples were investigated both in an unloaded condition and under a constant tensile load and at different moisture levels. Regions of the moisture-cycled samples that had been exposed to an electron beam during image acquisition showed damage running through pits and their surroundings. Specimens loaded in the green condition and dried in the chamber for 2 h without beam exposure except during imaging showed no noticeable cell-wall damage. The results indicate that the electron beam may be a major source of damage initiation. Therefore, it is essential to note the circumstances of the rest when explaining the observations made in ESEM studies.

  • 46.
    Navi, Parviz
    et al.
    EPFL, École Polytechnique Fédérale de Lausanne.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    The thermo-hydro-mechanical processing of wood.2012 (ed. 1)Book (Refereed)
    Abstract [en]

    The fabrication of wood-derived products is numerous and is continuously being developed thanks to its unique advantages: widespread availability, natural renewal, favorable ecological assessment and its flexibility of implementation. Moreover, the polymeric components of wood together with its porous structure confer to it a faculty for transformation exceeding that of other materials.

    Since the dawn of civilization wood has been used in its natural state. Only recently has wood been developed to form a range of products that are increasingly functional, based on a combination of performance and sustainability requirements.

    Since the beginning of the last century, the advance of knowledge on this topic has been constant, mainly through the efforts of systematic scientific research and new types of applications.

    Around the middle of the last century the preliminary work addressing the science and technology of wood was published. The current success in the understanding of its material properties, chemistry, physics and advances obtained in materials science, together with modeling techniques, provided the means for engineers and researchers to be able to engineer wood as a material and to produce new materials and products under controlled processing conditions.

    The intention to overcome difficulties in the processing technologies, as related to wood, requires an interdisciplinary approach. A close co-operation between scientific disciplines such as the anatomy of wood, physics, chemistry and mechanics makes it possible for each to contribute a constructive and complementary part in order to evolve, together, the technologies that relate to the various wood treatments, such as, for example - conservation, drying, machining, shaping and joining, etc.

    One of the emerging eco-friendly treatment methods is the combined use of temperature, moisture and mechanical action, the so called Thermo-Hydro-Mechanical (THM) treatment.  THM processing is implemented to improve the intrinsic properties of wood, to produce new materials, and in order to acquire a form and functionality desired by engineers without changing the eco-friendly nature of the material. These processes can be divided into two major categories; Thermo-Hydro (TH) treatments and Thermo-Hydro-Mechanical (THM) treatments.

    As we pointed out above, wood consists of natural polymeric chains, connecting to each other by hydrogen bands, and in certain parts by covalent bonds. The hydrogen bond is at the origin of its properties to transformation. For example, when wood is put under thermo-hydrous conditions, allowing for the softening of its amorphous components, it can easily deform which makes it possible to consider the application of a large number of industrial processes such as molding, densification, surface densification, bending, shaping, drying at high temperature, etc. Nevertheless, the application of high temperature, however, with or without moisture can damage mechanically, and modify chemically, the polymeric components of wood.

    The intention to gather together in one book the key elements of the chemical degradation of wood constituents under TH processing, the Thermo-Hydro, the Thermo-Hydro-Mechanical behavior, as well as a selection of the principal technologies implemented in TH/THM treatments, constitutes the primary reason of this edition. This work is intended for researchers, professionals of timber construction, as well as students studying the science of materials, wood technology and processing, civil engineering and architecture. This work is not exhaustive or a reference, but intends to deliver an outline of the scientific disciplines necessary to apprehend the technologies of wood THM and its behavior during treatment, as well as during its use.

    This work consists of 11 chapters. The first chapter is devoted to the reasons for TH/THM processing.  The ancient treatments of wood by THM processing are discussed in the second chapter. It is shown that different heat treatment processes have been used to improve the performance of wood and that the use of these processes dates back many thousands of years. The description of the structure and the chemical composition of the components of wood are given in the third chapter. In the fourth chapter, the explanation and modeling of certain THM behaviors of wood is presented. In the first part, the small and large deformations of wood are described, and the constitutive equations of elastic linear, as well as elastic nonlinear behavior of wood, are derived. In the second part the viscoelastic behavior of wood under ambient temperature, constant and variable humidity is described. In the chapter five, the behavior of THM of wood under variable moisture and temperatures (as high as 200°C), is examined by considering that during the processing, at high temperatures, the components of wood undergo certain chemical modifications. In this chapter the effects of the processing parameters: temperature, moisture content and time, on the THM wood characteristics are discussed. The sixth chapter is devoted to the processing of wood densification by THM treatment. In the first part of this chapter various THM wood densification processing methods are discussed and the machines that have been developed in different countries corresponding to open, closed, and mixed processing, are illustrated. In the rest of this chapter the origin and mechanisms of the shape memory and fixation of compression-set by THM treatment are discussed. Chapters seven and eight are devoted respectively to the wood welding by friction techniques and wood surface densification techniques. In both chapters different techniques are discussed and the problems related to these different ‘open systems’ are explained.

    In the recent decades developments in the area of heat treatment have accelerated considerably. At the present time many countries have developed their own wood TH treatments. In chapter nine most of these processing methods are presented and discussed. In chapter ten different wood bending processes: bending of solid-wood, laminated wood bending and other methods like green wood bending and kerfing are presented and different techniques discussed. Also, the theory of solid wood bending is explained. This chapter gives a demonstration of solid wood bending in the laboratory and at industrial levels. Finally, a selection of technologies is presented in the eleventh chapter on the fabrication of reconstituted wood, namely: Fiberboards, Particle boards and panels made of veneers.

    For the benefit wood engineers and other people with an interest in this fascinating industry, we hope that the availability of this material as printed book will provide an understanding of all the fundamentals involved in TH and THM processing of wood.

  • 47.
    Nilsson, Jonaz
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Jimmy
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Kifetew, Girma
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sandberg, Dick
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Shape stability of modified engineering wood product (EWP) subjected to moisture variation2011In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 6, no 3, p. 132-139Article in journal (Refereed)
  • 48.
    Nilsson, Jonaz
    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.
    A new light-weight panel for interior joinery and furniture2013In: Proceeding of 9th Meeting of the Northern European Network for Wood Science and Engineering -WSE 11-12 September 2013, Hannover, Germany / [ed] Brischke, Christan & Meyer, Linda, Hannover: Leibnitz Universität Hannover , 2013, p. 184-189Conference paper (Refereed)
    Abstract [en]

    Light-weight materials based on wood for interior fittings and furniture have been of interest for at least the last fifty years, mainly for cost-reducing reasons. Today, the increasing care of the environment and the growing interest in the concept of a sustainable society provide further impulses for the development of light-weight materials. A common consequence of the reduction in weight of such materials is deterioration in the mechanical properties, e.g. strength, stiffness and shape stability, compared to those of solid wood. New solutions for e.g. connections and mountings are also needed. Today, new panel materials are required where the disadvantages of conventional light-weight materials are less prominent and with aesthetic and tactile properties close to those of natural wood.

    In this paper, a new type of light-weight panel is presented. The panel is cross-laminated in three layers and consists throughout of solid wood. The weight reduction is a consequence of the hollow middle-layer construction. The intention of the construction is to make it possible to mix species in the panel, e.g. a high-quality and high-density wood on the surface and a low-quality wood with low weight in the core, and thus to optimize the properties of the panel for a specific purpose and to keep costs down at the same time. In this first study, however, the whole panel is made of Scots pine.

    Bending tests show that the glue-line between the outer layers and the core is critical for the mechanical performance of the panel and this has to be developed further.

    This study shows that this light-weight panel can be used as a single component or in a system with other components for interior fittings and furniture. The current design of this light-weight panel has some deficiencies but, in addition to its low weight, it has the potential to provide the mechanical, aesthetic and tactile properties asked for.

  • 49.
    Nilsson, Jonaz
    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 University of Technology .
    Densified and thermally modified wood as outer layers in light-weight panels for furniture and joinery2014In: Final Cost Action FP0904 Conference : “Recent Advances in the Field of TH and THM Wood Treatment”: May 19-21, 2014, Skellefteå, Sweden : book of abstracts, Luleå: Luleå tekniska universitet, 2014, p. 79-80Conference paper (Refereed)
  • 50.
    Nilsson, Jonaz
    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.
    Densified and thermally modified wood in light-weight panels2014In: Presented at the 2014 Forest Products Society International Convention Program, Quebec City, Canada, August 10-13, 2014, 2014Conference paper (Refereed)
1234 1 - 50 of 155
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