| 1. |
- Adamopoulos, Stergios, et al.
(författare)
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Adhesive bonding of beech wood modified with a phenol formaldehyde compound
- 2012
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 70:6, s. 897-901
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Tidskriftsartikel (refereegranskat)abstract
- Untreated (controls) and phenol–formaldehyde (PF)-modified beech wood (10 and 25 % solid content) were glued with phenol resorcinol formaldehyde (PRF) and polyvinyl acetate (PVAc). Shear strength of PRF-bonded specimens was higher than that of PVAc-bonded ones under dry and wet conditions irrespective of the pre-treatment. Under dry conditions, only PVAc-bonded specimens exhibited reduction in shear strength due to PF-modification with 25 % PF concentration as compared to the controls. PF treated wood provided inferior bonding under wet conditions with the exception of 25 % PF concentration specimens glued with PRF adhesive. Modification with PF resulted in a decrease of adhesive penetration into the porous network of interconnected cells, especially at 25 % PF concentration.
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| 2. |
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| 3. |
- Adamopoulos, Stergios, et al.
(författare)
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Relationship of the toughness and the modulus of elasticity in static bending of small clear spruce wood specimens
- 2010
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 68:1, s. 109-111
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Tidskriftsartikel (refereegranskat)abstract
- Unlike static bending, toughness is a mechanical property less commonly measured in clear wood. The paper presents results on the relationship of toughness and modulus of elasticity in static bending based on DIN standard tests on small, clear specimens of spruce, 2×2 cm2 in cross section.
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| 4. |
- Ahmed, Sheikh Ali, et al.
(författare)
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Development of a new rapid method for mould testing in a climate chamber : preliminary tests
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:4, s. 451-461
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12–14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.
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| 5. |
- Alfredsen, Gry, et al.
(författare)
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Thermogravimetric analysis for wood decay characterisation
- 2012
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 70:4, s. 527-530
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Tidskriftsartikel (refereegranskat)abstract
- The paper focuses on the use of thermogravimetric analysis (TGA) as a fast method for estimating the change of lignocellulosic materials during fungal degradation in laboratory trials. Traditionally, evaluations of durability tests are based on mass loss. However, to gain more knowledge of the reasons for differences in durability and strength between wooden materials, information on the chemical changes is needed. Pinus sylvestris sapwood was incubated with the brown rot fungusGloeophyllum trabeum and the white rot fungus Trametes versicolor. The TGA approach used was found to be reproducible between laboratories. The TGA method did not prove useful for wood deteriorated by white rot, but the TGA showed to be a convenient tool for fast estimation of lignocellulosic components both in sound wood and wood decayed by brown rot.
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| 6. |
- Berglund, Anders, et al.
(författare)
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Value optimized log rotation for strength graded boards using computed tomography
- 2014
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 72:5, s. 635-642
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Tidskriftsartikel (refereegranskat)abstract
- A possible application for an industrial computed tomography scanner in a sawmill is finding an optimal rotational position of logs with respect to knots and outer shape. Since a computed tomography scanner is a great investment, it is important to investigate potential profitability of such an investment for different production strategies. The objective of this study was to investigate the potential value increase of the sawn timber of Norway spruce (Picea abies (L.) Karst.) by rotating logs to their optimum position prior to sawing compared with sawing all logs in horns down position. The production strategy evaluated by log breakdown simulation in this case study was to produce strength graded timber of the center boards, while the side boards were appearance graded. This case study showed an average value increase with respect to the value of center boards, side boards and chips of 11 %.
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| 7. |
- Butylina, Svetlana, et al.
(författare)
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Weathering of wood-polypropylene composites containing pigments
- 2012
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 70:5, s. 719-726
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Tidskriftsartikel (refereegranskat)abstract
- Outdoor applications of composites have raised questions about their durability. In this study, the effects of outdoor weathering on the properties of wood-polypropylene composites with and without pigments were examined. The composites were placed outdoors for one year, and their colour changes were evaluated after 1, 3, 6, 9 and 12 months of weathering. The durability of the composites was assessed by testing flexural strength and density. Scanning electron microscopy was applied to evaluate the surface degradation of the composites. The weathering resulted in considerable colour fading of the composites. The composites containing darker colour pigments had better colour stability. After weathering, the general trend was a decrease of the flexural strength and density of the composites. The decrease in flexural strength was found to be lower for the composites having higher density.
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| 8. |
- Danielsson, Henrik, et al.
(författare)
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A probabilistic fracture mechanics method and strength analysis of glulam beams with holes
- 2011
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 69:3, s. 407-419
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Tidskriftsartikel (refereegranskat)abstract
- A probabilistic fracture mechanics method is presented and applied to glulam beams with holes. The method is based on a combination of Weibull weakest link theory and a mean stress method which is a generalization of linear elastic fracture mechanics. Combining these two methods means that the global strength will be governed by both fracture energy and material strength and also that the stochastic nature of the material properties are taken into account. The probabilistic fracture mechanics method is evaluated by comparison to experimental test results. The method shows good ability to predict strength, with the exception of very small beams where the capacity is overestimated. The comparison to experimental tests deals also with other methods for strength analysis including code design methods.
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| 9. |
- Ekevad, Mats, et al.
(författare)
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Geometry of kerf when curve sawing with a circular rip-saw
- 2014
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 72:6, s. 809-814
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Tidskriftsartikel (refereegranskat)abstract
- Rip-sawing following the curvature of a crooked log means advantages for yield. However, the possibility to saw in a narrow curve with a circular saw blade is limited because of the inherently flat geometry of circular saw blades. For a double arbour circular saw the situation is even more problematic because the two blades have a certain overlap and thus, the two arbours are not positioned in the same horizontal position. In this study, a theoretical geometrical study of the creation of a kerf with a single circular saw blade and with a double arbour circular saw with two saw blades was examined. Results for stiff saw blades show that the kerfs become in general curved and inclined (tilted) in the vertical direction and also that the width of the kerfs for double arbour saws becomes wider at the top and bottom of the cant than in the middle. Additionally, the sawn boards obtain varying thickness along their width because of the varying kerf width. A comparison with experimental thickness data from four test sawings at a sawmill indicates that the theoretical results are valid and that curve sawn boards become thinner than straight sawn boards.
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| 10. |
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| 11. |
- Fredriksson, Maria, et al.
(författare)
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Small resistive wood moisture sensors: a method for moisture content determination in wood structures
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 71:4, s. 515-524
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Tidskriftsartikel (refereegranskat)abstract
- The wood moisture content influences the service life of wood structures since wood is susceptible to decay by rot fungi if it is exposed to high moisture contents during long periods of time. In rain exposed structures, the moisture content close to end grain surfaces and joints can be significantly higher than the average moisture content, but moisture content determinations at such locations require small moisture content sensors. This paper presents small resistive moisture content sensors fastened by electrically conductive adhesive. The relationship between moisture content and electrical resistance was determined for Norway spruce (Picea abies (L.) Karst.) for a wide range of moisture conditions achieved both by equilibrating specimens over saturated salt solutions and by the pressure plate method. The error, i.e. the difference between the gravimetric moisture content and the moisture content from the regression equation, increased with increasing moisture content. Neither the wood type (heartwood/sapwood) nor the growth rate (southern or northern Sweden) influenced the resistance-moisture content relationship.
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| 12. |
- Gustafsson, Per-Johan, et al.
(författare)
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Perpendicular to grain stiffness of timber cross sections as affected by growth ring pattern, size and shape
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 71:1, s. 111-119
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Tidskriftsartikel (refereegranskat)abstract
- A finite element plane stress parameter study of the global perpendicular to grain stiffness of timber structural elements such as beams and cross ties is presented. This stiffness is affected by the size and shape of the cross section, the growth ring pattern, the stiffness properties of the wood and the boundary conditions. Various rectangular sections with concentric circular growth rings with systematic variation of pith location were studied for elastic orthotropic wood properties corresponding to a softwood species and a hardwood species. Two conventional and two periodic boundary conditions were considered. The results are presented in diagrams. Growth ring pattern and cross section size were found to be of great importance for the stiffness, in particular for softwood elements. Global stiffness for material properties representing Norway spruce differed with a factor 7 between stiffest and weakest growth ring pattern. The influence of boundary conditions appears in comparison to be small.
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| 13. |
- Hu, Min, et al.
(författare)
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Local variation of modulus of elasticity in timber determined on the basis of non-contact deformation measurement and scanned fibre orientation
- 2014
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 73:1, s. 17-27
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, the utilization of non-contact deformation measurement systems based on digital image correlation (DIC) has increased in wood related research. By measuring deformations with DIC systems, surface strain fields can be calculated. The first aim of this study concerns the possibility to detect detailed strain fields along the entire length of a wooden board subjected to pure bending and the potential of using such strain fields to determine a bending modulus of elasticity (MOE) profile along a board. Displacements were measured over 12 subareas along a flat surface of the board. For each such area, a separate local coordinate system was defined. After the transformation of locally measured coordinates to a global system, high resolution strain fields and a corresponding bending MOE profile were calculated. A second method in establishing bending MOE profiles is to use fibre angle information obtained from laser scanning and a calculation model based on integration of bending stiffness over board cross sections. Such profiles have recently been utilized for accurate strength grading. A second aim of this study was to investigate the accuracy of the bending MOE profiles determined using the latter method involving fibre angle information. Bending MOE profiles determined using the two described methods agree rather well. However, for some patterns of knot clusters, the local bending MOE, calculated on the basis of fibre angles and integration of bending stiffness, is overestimated. Hence, this research adds knowledge that may be utilized to improve the newly suggested strength grading method.
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| 14. |
- Häglund, Martin
(författare)
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Parameter influence on moisture induced eigen-stresses in timber
- 2010
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 68:4, s. 397-406
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Tidskriftsartikel (refereegranskat)abstract
- Moisture induced stress in timber is dependant on many factors. The driving force behind is the moisture variation in the surrounding air which causes induced stress due to restraint of hygro-expansion within timber elements (this can to some extent be seen analogous to thermally induced stress in steel). Today's computational power together with advanced constitutive models offers aaEuro-aEuro-valuable tool towards understanding and determining moisture actions on timber. However, it seems that the issue concerning uncertainties of the input parameters is seldom addressed. This paper presents results on how various factors affect the resulting moisture induced stress by aaEuro-aEuro-parametric study of the input values. A small numerical change of one parameter may possibly result in aaEuro-aEuro-major change of calculated stress levels. It is for example, shown that coating (paint) and cross-sectional dimensions play an important role for spatial stress distribution.
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| 15. |
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| 16. |
- Johansson, Pernilla, et al.
(författare)
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Mould growth on kiln-dried and air-dried timber
- 2013
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Ingår i: European Journal of Wood & Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 71:4, s. 473-481
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Tidskriftsartikel (refereegranskat)abstract
- The problem with discoloration, due to fungal growth, of wooden outdoor constructions seems to have increased in recent years. One reason for this increase might be an impact of new drying methods of timber. Modern kiln drying methods use high temperatures in an effort to shorten the drying process, which leads to fast capillary water transport and subsequently redistribution and accumulation of dissolved substances at the surface. These can then be used as nutrients by fungi. In this study, wood was dried according to different simulated drying schedules. The mould resistance of the timber was then tested. Wood dried at room temperature was used as a reference. No differences could be confirmed at the end of the test; mould growth was extensive on all the samples. However, mould growth started earlier on the kiln-dried samples than on air-dried timber. As for the discolouring fungus, there was a clear difference between wood dried at room temperature and kiln-dried wood, though no difference could be established between the two artificial methods.
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| 17. |
- Jonsson, Maria
(författare)
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Wet storage for discolouration protection during roundwood storage of three Swedish hardwoods
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 71, s. 219-225
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Tidskriftsartikel (refereegranskat)abstract
- Discolouration progressing from the end surfaces is a wood quality problem that arises when storing hardwood logs during summer. Wet storage (water sprinkling) is used for protecting stored softwood logs, but experience of wet storing hardwoods is limited. To test the benefit of wet storing hardwoods, logs of Betula pendula/pubescens, Alnus incana/glutinosa, and Populus tremula were wet and dry-stored during 12 summer weeks in southern Sweden to compare the development of discolouration. The discolouration was measured visually during storage in split logs. Wet storage was found to significantly reduce discolouration in the stored logs of all species, with the reduction being most pronounced for birch.
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| 18. |
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| 19. |
- Olsson, Anders, 1973-, et al.
(författare)
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Prediction of timber bending strength and in-member cross-sectional stiffness vartiation on basis of local wood fibre orientation
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer. - 0018-3768 .- 1436-736X. ; 71:3, s. 319-333
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Tidskriftsartikel (refereegranskat)abstract
- Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3600 mm, a coefficient of determination as high as 0.68-0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.
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| 20. |
- Parida, Gabriela, et al.
(författare)
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Prefabricated timber walls anchored with glued-in rod connections : racking tests and preliminary design
- 2013
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 71:5, s. 635-646
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Tidskriftsartikel (refereegranskat)abstract
- A new beam and post system for multi-storey timber buildings is being developed in Sweden. The stabilising walls are constructed from two Kerto-Q LVL boards glued and screwed onto a glulam skeleton. The walls are prefabricated off-site and connected to the foundation using either glued-in rods or nail plates.An introductory racking test of a full scale stabilising wall anchored with glued-in rods was performed. The paper presents the results of the experimental test and evaluates them using the transformed section method. To evaluate the strength of the glued-in rods, two newly proposed models were employed. A theoretical examination was conducted to investigate the role of the sheathing in the racking load carrying capacity. An analysis was also performed to quantify the contribution of the axial force on the racking capacity of the wall, which was conservatively ignored in the experiment. Generally, the stabilising wall panels tested in this experimental programme showed high strength and stiffness. The anchoring joints with glued-in rods demonstrated a high load-carrying capacity, however, with a large scatter and a brittle failure mode characterized by pull-out from the timber member. The transformed section method is recommended as a method for designing stabilising walls anchored with glued-in rods.
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| 21. |
- Straze, A., et al.
(författare)
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The influence of material properties on the amount of twist of spruce wood during kiln drying
- 2011
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Ingår i: European Journal of Wood and Wood Products/Holz als Roh - und Werkstoff. - : Springer Science and Business Media LLC. - 1436-736X .- 0018-3768. ; 69:2, s. 239-246
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Tidskriftsartikel (refereegranskat)abstract
- The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20A degrees/m in the case of boards close to the pith, and decreased to less than 4A degrees/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage.
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| 22. |
- Ulvcrona, Thomas
(författare)
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Effects of lateral wood zone on brown rot resistance of untreated and linseed oil-impregnated Scots pine wood
- 2012
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Ingår i: European Journal of Wood and Wood Products. - : Springer Science and Business Media LLC. - 0018-3768 .- 1436-736X. ; 70, s. 771-773
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Tidskriftsartikel (refereegranskat)abstract
- Various oils can be used to lower the equilibrium moisture content and increase the service life of Scots pine wood products. The aim of this study was to investigate effects of the lateral wood zone on the brown rot resistance of untreated and linseed oil-impregnated Scots pine wood in a laboratory test (EN 113). Significant differences were found in the mean mass losses of treated and untreated specimens taken from three lateral heartwood zones, but not between specimens taken from sapwood. The treatment had no significant effect on sapwood, although it seems to have some positive effect on the durability of heartwood, apparently due to interactive effects with the high extractives contents of heartwood.
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