| 1. |
- Beyer, Gunilla, et al.
(författare)
-
Limning av pallförband och pallar
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Spikade förband i lastpallar utgör i vissa sammanhang ett problem från skade- och återvinningssynpunkt. Spikkrypning kan orsaka godsskador och spikar kan även orsaka problem från återvinningssynpunkt. Under senare år har det skett en stor utveckling på limsidan och marknaden för lim och limmade produkter ökar. Limning är därför ett intressant alternativ till spikning. Vad som söktes var ett lim som kan användas på sågade ytor, har fogfyllande egenskaper, ger en elstisk fog, är lätt att hantera och applicera, inte kräver höga presstryck, höga temperaturer eller lång tid att härda, tål klimatpåkänningar, är acceptabelt från miljösynpunkt och inte orsakar problem vid återvinning. I den här rapporten redovisas utprovning av några limtyper.
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| 2. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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Formstabilitet i underlägg för dukning
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this study, a coaster intended for table setting has been investigated regarding shape stability in relation to the surrounding climate. The coaster was made up of paper, some of which was printed, and a fibreboard that was bonded together.Symmetry in a construction is desirable for high shape stability, which is known since before. The fact that the surfaces have a similar moisture absorption contributes to the symmetry. Boards that have a harder surface than the opposite should be sanded so that both surfaces of the board have a similar moisture absorption. The orientation of the components in a laminate can reduce or increase the asymmetry if the surfaces have different moisture absorption capacity. Symmetrical construction as well as symmetrical moisture absorption are beneficial for high shape stability.
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| 3. |
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| 4. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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Influence of different pressing parameters on urea-formaldehyde adhesive-bond strength in laminated veneer products
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the present study was to investigate the relationships between contact pressure, temperature, hardener content and pressing time fixed at different levels and the strength of the UF adhesive bond, in order to develop a model to predicting the bonding strength. Bond strength was measured with the Adhesive Bonding Evaluation System, and a linear model for predicting adhesive bond strength using four independent variables was developed (R2 = 0.75). The strongest parameter was pressing time, followed by hardener content and temperature, all of which explained variation in bond strength at the same level. Pressure had no significant influence on the bond strength.
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| 5. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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Influence of pressure on bond-line shear strength in laminated veneer products
- 2022
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Ingår i: Wood Material Science & Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 17:6, s. 1020-
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the bond-line strength of different bonding pressure of veneers in dry (9% moisturecontent) and wet (immersed in water) conditions was investigated. The results show that peeledEuropean beech veneers need approximately 0.5– 1.2 MPa pressure to achieve a proper bond-linewhen a urea-formaldehyde adhesive was used. The pressure variation within this range did notsignificantly affect the strength of the dry veneer, but the strength of the wet veneers decreasedas the bonding pressure increased. The type of failure varied, especially for the wet veneers. Athigh pressure, the wood were stronger than the cohesive strength of the adhesive and thestrength of the adhesion between the adhesive and the wood. High pressure, however, caused acompression of the bond-line and resulted in a lack of adhesion.
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| 6. |
- Blomqvist, Lars, 1962-
(författare)
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Shape stability of laminated veneer products
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is about the shape stability of laminated veneer products.Laminated veneer products consist of veneers bonded together with adhesive into a predetermined shape. Such products are used in several contexts but especially in furniture manufacture. Deviation from the intended shape is a problem for both manufacturers and customers of the final products. The shape stability of laminated veneer products depends on a variety of material and process parameters, and this thesis identifies several important factors that influence shape stability. The purpose of this thesis is to find ways to decrease distortion and improve shape stability so that product quality can be improved.Different ways of measuring shape stability, both in an industrial environment and in a more research-based context, are presented in this thesis. Various studies have been conducted to evaluate the influence of different material and process parameters on shape stability. The parameters studied were species (beech and birch), adhesive system (bio-based adhesives, adhesive systems based on urea formaldehyde), adhesive distribution on the veneer, climate, moisture content and fibre orientations of the veneers, as well as orientation of the individual veneers in an assembly.The results clearly show that the fibre orientation of the veneer strongly influences the shape stability of a laminated veneer product. This means that products can show considerable distortion (particularly twist) if the fibre orientation of the veneer is orientated in an unsuitable way in the assembly before moulding. The effect of fibre orientation on shape stability can be very small directly after moulding, but it increases considerably when the moulded product is subjected to a change in moisture content. In general, a change in moisture content leads to distortion. Moisture change alone, however, results in a controlled distortion.An asymmetrical construction coupled with different moisture contents of the veneers in an assembly before moulding will result in poor shape stability of the product. Other studied parameters had a low impact on shape stability, although beech resulted in more distortion and poorer shape stability than birch.In order to produce shape-stable laminated veneer products, the veneers should be conditioned to a uniform moisture content and sorted with regard to fibre orientation before bonding. The orientation of the veneers is highly important regarding both fibre orientation and the loose or tight side of the veneer. If shape stability is the main target, the loose sides of peeled and sliced veneers should be oriented in the same manner.
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| 7. |
- Blomqvist, Lars, et al.
(författare)
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The effect of veneer-modifcation on the bond-strength in laminated veneer products
- 2015
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Ingår i: Pro Ligno. - 1841-4737 .- 2069-7430. ; 11:4, s. 43-49
-
Tidskriftsartikel (refereegranskat)abstract
- A major problem in the manufacture of three-dimensional laminated veneer products (LVP) is damage due to stretching and/or buckling of the veneer. To reduce or eliminate this problem, veneer densification or adding a strengthening layer to the veneer can be an alternative. To study how veneer modification influences the veneer-to-adhesive bond strength, three methods of modification were studied in relation to an unmodified reference veneer: (1) densified veneer, (2) veneer pre-bonded with paper 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 and polyvinyl acetate (PVAc) adhesive, and (c) with a PVAc adhesive. Densification, pre-bonding with paper, and NW with UF/PVAc adhesive mixture resulted in no or only a slight decrease in strength of the bond-line compared to the reference. NW glued with UF or PVAc adhesive showed a considerable reduction in the strength of the bond-line. The climatic cycling had no significant influence on the bond strength.
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| 8. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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The effect of veneer modification on the bond-line strength in laminated veneer products
- 2015
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Ingår i: Pro Ligno. - Brasov, Romania : Transilvania University. - 1841-4737 .- 2069-7430. ; 11:4, s. 43-49
-
Tidskriftsartikel (refereegranskat)abstract
- A major problem in the manufacture of three-dimensional laminated veneer products (LVP) is damage due to stretching and/or buckling of the veneer. To reduce or eliminate this problem, veneer densification or adding a strengthening layer to the veneer can be an alternative. To study how veneer modification influences the veneer-to-adhesive bond strength, three methods of modification were studied in relation to an unmodified reference veneer: (1) densified veneer, (2) veneer pre-bonded with paper 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 and polyvinyl acetate (PVAc) adhesive, and (c) with a PVAc adhesive. Densification, pre-bonding with paper, and NW with UF/PVAc adhesive mixture resulted in no or only a slight decrease in strength of the bond-line compared to the reference. NW glued with UF or PVAc adhesive showed a considerable reduction in the strength of the bond-line. The climatic cycling had no significant influence on the bond strength.
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| 9. |
- Blomqvist, Lars, 1962-, et al.
(författare)
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The influence of veneer modification on adhesive bond strength
- 2014
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Ingår i: Proceedings of 10th Meeting of the Northern European Network for Wood Science & Engineering (WSE). - Edinburgh : Edinburgh Napier University.. ; , s. 150-155
-
Konferensbidrag (refereegranskat)
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| 10. |
- Blyberg, Louise, et al.
(författare)
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Adhesive joints for structural timber/glass applications : Experimental testing and evaluation methods
- 2012
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier BV. - 0143-7496 .- 1879-0127. ; 35, s. 76-87
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Tidskriftsartikel (refereegranskat)abstract
- A study of three different adhesives, silicone, acrylate and polyurethane, intended for adhesive joints in structural timber/glass applications is presented in this paper. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with a bond area of 800 mm2. Special fixtures were designed both for gluing and testing the specimens. The results include strength and failure type of the adhesive bond as well as deformation of the bond lines, measured with LVDTs and a non-contact optical 3D-deformation measuring system used in combination with finite element modelling in order to obtain detailed information about the behaviour.Of the tested adhesives, the acrylate (SikaFast 5215) provided the largest strength, both in tension and shear. The mean strength obtained for this adhesive bond was 3.0 MPa in tension and 4.5 MPa in shear.Further, it is demonstrated how rotations in the specimen during the test can be detected with the optical measuring system and how finite element modelling can be used to study the stress distribution internally in the adhesive bond. One conclusion obtained from the combination of results from the optical measuring system and finite element modelling is that the behaviour of the silicone adhesive is highly influenced by its near incompressible behaviour.
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| 11. |
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| 12. |
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| 13. |
- Blyberg, Louise, 1983-, et al.
(författare)
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Timber/Glass Adhesive Bonds : Experimental testing and evaluation methods
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Both timber and glass are materials that have aesthetically pleasing properties. An appealing idea is to combine them to overcome the drawbacks and utilise the beneficial mechanical properties. Adhesive bonding with an appropriate adhesive could provide a uniform stress distribution at the transition between the materials.This report presents a study of three different adhesives, silicone, acrylate and polyurethane. Intentionally, adhesives with a wide range of properties were chosen. The adhesive bonds between timber and glass were tested both in tension and in shear with rather small bonds, 800 mm2. Special fixtures were designed both for gluing and testing of the adhesive bond specimens studied. The results presented include a traditional study of strength, failure type and relative displacement measured with LVDT’s, but also an extended study with a non-contact optical 3D-deformation measuring system and finite element modelling.Of the adhesives tested, the acrylate (SikaFast 5215) performed best, both in tension and shear. The mean strength obtained for this adhesive was 3.0 MPa in tension and 4.5 MPa in shear. Even if an important factor when gluing glass is the load distribution ability, the flexible silicone adhesive has too low stiffness and strength for use in structural components, where structural refers to the ability of a component to carry loads other than its own weight.
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| 14. |
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| 15. |
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| 16. |
- Hameury, Stéphane, et al.
(författare)
-
Magnetic resonance imaging of moisture distribution in Pinus sylvestris L. exposed to daily indoor relative humidity fluctuations
- 2006
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Ingår i: Wood Material Science & Engineering. - : Informa UK Limited. - 1748-0272 .- 1748-0280. ; 1:3-4, s. 116-126
-
Tidskriftsartikel (refereegranskat)abstract
- n contact with indoor air, wood materials have a high potential passively to reduce the indoor humidity fluctuations resulting from internal moisture loads and outdoor humidity fluctuations. This ability, characterized by the moisture buffering capacity of building materials, has attracted increasing attention within building physics, but a suitable method to appraise and quantify this phenomenon is still sought. In this study, a non-invasive spectroscopic method of accessing information about the interaction between indoor air and Scots pine was investigated. A comprehensive account is given of spatially resolved moisture absorption (desorption) into (from) Scots pine by proton magnetic resonance imaging ([1H]MRI) based on an effective single-point imaging (SPI) sequence. SPI images of bound-water distribution in Scots pine with a spatial resolution on a sub-millimetre scale were acquired when one of the orthotropic directions of the wood material was exposed to typical indoor day-to-day moisture fluctuations. The nuclear magnetic resonance imaging measurements presented in this study clearly show the potential of the method to provide accurate spatial information about the wood-water interaction below the fibre saturation point and hence to characterize the moisture buffering capacity of wood materials.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
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| 23. |
- Mäger, K. N., et al.
(författare)
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Influence of adhesives on fire resistance of wooden i-joists
- 2021
-
Ingår i: World Conference on Timber Engineering 2021, WCTE 2021. - : World Conference on Timber Engineering (WCTE).
-
Konferensbidrag (refereegranskat)abstract
- FIRENWOOD is an Era-NET cofund Forest Value project (2019-2022) dealing with the fire resistance testing and design methods of engineered wood products at elevated temperatures and fire. As one part of the project, various adhesives, allowed for load bearing timber structures, are tested in finger joints in small scale and medium scale fire tests. The paper will provide a description of these tests and an overview and analysis of the results. Based on the test data of both types, a good agreement regarding the adhesive performance between the tests can be shown. The design model for wooden I-joists is described and values for the depth of the zero-strength layer are proposed for different adhesive performance levels in finger joints.
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| 24. |
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| 25. |
- Olofsson, Robert, et al.
(författare)
-
Loaded fire tests with I-joists
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the tests was to evaluate the potential reduction of the moment capacity of I-joists caused by bondline integrity of the finger joints. Each I-joist was made with 11 different adhesives in the finger joints in tension flange. All the adhesives were from Firenwood selection. Finger joints in tension may show a lower load-bearing capacity in the fire situation depending of the bond line integrity in fire. I-joists were loaded in bending with the tension flange being closer to the fire. I-joists were protected with gypsum plasterboard during the entire fire test. Cavities of the test assembly were filled with stone wool.
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| 26. |
- Olofsson, Robert, et al.
(författare)
-
Model scale fire tests with cross-laminated timber
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the fire tests presented in this report was to measure the mass loss and the charring depth of CLT (cross-laminated timber) elements with different types of adhesives when exposed to fire from below. CLT elements may heat delaminate when exposed to heat. If this occurs, it depends, among other things, on the temperature of the adhesive and on the adhesive’s ability to retain its adhesive properties. Eleven adhesives are used in FIRENWOOD project in order to compare properties in fire. Adhesives originate from four different chemical backgrounds and represent the state of the art of adhesives used in timber structures. Adhesives are manufactured by 4 leading European adhesive manufacturers, and all 11 adhesives have passed requirements in European standards for load-bearing timber structures. Adhesives are marked with numbers 1 to 12 (adhesive no 10 is not included in this Work Package). Not all adhesives were tested for this method and is therefore not presented in the results.However, some additional adhesives were used in the tests presented in this report and are marked 21, 22, 23 and 24. The same numbers are used for all adhesives in all tests throughout FIRENWOOD project.
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| 27. |
- Ong, Chee Beng, et al.
(författare)
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Bench-scale fire tests of Dark Red Meranti and Spruce finger joints in tension
- 2018
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 168, s. 257-265
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the secondary failure of Malaysian Dark Red Meranti (Shorea spp.) and Spruce (Picea abies) finger joints in a glulam beam in a fire test using a bench-scale test set-up. Secondary failure is the occurrence of failure of the bond lines due to fire and the falling off of the outermost tension layers, exposing the uncharred inner layers to a sudden increase of fire intensity. The lack of published work and the difficulties in describing the behaviour of the finger joints after the secondary failure in a full-scale fire test has identified the need for a simple bench-scale method, incorporating the conditions of the standard fire test. This paper focusses on the performance of the finger joints which together with other defects such as knots and splits are generally the weakest component in the glulam beam. The finger joints were bonded with structural adhesives, specifically phenol resorcinol formaldehyde (PRF) and polyurethane (PUR). They were tested in tension to imitate the failure of finger joints on the tension side of a standard fire test of a glulam beam. Constant heat flux was introduced to the finger-jointed specimens to replicate the secondary failure of a glulam beam in the standard fire test. The results of this study indicate a relationship between the charring rate and density of the specimens, with higher density Dark Red Meranti showing lower charring rate compared to the lower density Spruce specimens. Factors such as constant heat flux as opposed to the time-increasing heat flux exposure and specimen size influenced the charring rate of the specimens. The char rate was measured at the early stages of the fire test, which is known to have higher values since the build-up of the charred layers was not sufficiently substantial to protect the inner unburnt wood. Overall, the bench-scale fire test set-up was able to differentiate the fire performance of the adhesives, with PRF showing better fire performance compared to the specimens finger-jointed with PUR adhesive. In addition, tensile tests at ambient temperature showed no significant difference in tensile strength between finger joints bonded with different adhesives for the same wood species. The tensile strengths of the finger joints bonded with different adhesives were influenced by the temperature profile through the joint. The proposed bench-scale fire test was used to compare the quality of the adhesives in a fire situation, specifically with respect to secondary failure. The PRF was selected as the reference adhesive.
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| 28. |
- Petersson, Hans, et al.
(författare)
-
Högre värdeutbyte genom våt- och torrlimning av sågade sidobrädor till egenskapsoptimerade träprodukter för byggmarknaden
- 2009
-
Rapport (populärvet., debatt m.m.)abstract
- The purpose of this project was to investigate the possibilities to manufacture wet-glued laminated beams for load bearing applications from Norway spruce side board lamellae and by that achieve products that are difficult to obtain from the centre yield of a log and also contribute to increased profitability in the sawmill industry. Properties such as shape stability, strength and stiffness of wet glued beams with crosssectional dimensions 50×300 mm2 and lengths 4850 and 5200 mm were analysed and compared with corresponding dry glued products. The results obtained are very promising. espite the fact that the beams were produced from a batch of unsorted boards, the performed tests showed that the product has the necessary qualities to be competitive in relation to both glued laminated timber of grade L40 and structural strength graded timber of grade C35. Requirements concerning limitations for geometrical characteristics as expressed in a proposal for a new harmonised glulam standard are also met. The bond line of the wet glued beams was analysed regarding mechanical properties such as fracture energy, local strength and wood failure percentage after cyclic boiling and drying treatments. The results showed that the bonds are able to comply with requirements concerning bond lines to be used in indoor as well as outdoor constructions for structural pplications. To be able to improve the quality of boards for use as lamellae in wet glued beams, a method for scanning the slope of grain and disturbance of grain on board surfaces was also further developed and implemented.
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| 29. |
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| 30. |
- Sandberg, Karin, et al.
(författare)
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Separating Norway spruce heartwood and sapwood in dried condition with near-infrared spectroscopy and multivariate data analysis
- 2009
-
Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 128:5, s. 475-481
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Tidskriftsartikel (refereegranskat)abstract
- Norway spruce [Picea abies (L.) Karst.] heartwood and sapwood have differing wood properties, but are similar in appearance. An investigation was made to see whether near-infrared spectroscopy (NIRS) could be used with multivariate statistics for separation between heartwood and sapwood in dry state on tangential longitudinal surfaces. For classification of wood into sapwood and heartwood, partial least square (PLS) regression was used. Orthogonal signal correction (OSC) filtering was used on the spectra. This study shows that a separation of sapwood and heartwood of spruce is possible with NIR spectra measured in a laboratory environment. The visible-wavelength spectra have significant influence on the predictive power of separation models between sapwood and heartwood of spruce. All 44 specimens in the calibration set were correctly classified into heartwood and sapwood. Validation of the model was done with a prediction set of 16 specimens, of which one was classified incorrectly.
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| 31. |
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| 32. |
- Serrano, Erik, 1968-, et al.
(författare)
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Green-glued laminated beams : High performance and added value
- 2010
-
Ingår i: World Conference on Timber Engineering.
-
Konferensbidrag (refereegranskat)abstract
- The work presented in this paper deals with the use of green gluing (also known as wet gluing) as a mean to overcome the difficulties in making use of side boards for structural applications. By manufacturing laminated beams from unseasoned side boards several advantages are obtained. Beams were manufactured from side boards of approximately 25 mm thickness. The board width was 120 mm. The boards were glued together with a 1-component polyurethane adhesive to form a beam cross-section of approximately 120×315 mm2. After curing, the beams were split into two halves, each approximately 55 mm wide. These 55×315 mm2 beams were then dried in a conventional kiln dryer. Finally, the beams were planed to target size, 50×300 mm2. Tests performed included beam bending tests for strength and stiffness, tests of the shape stability of the beams, tests of the integrity of the adhesive bond lines (delamination) and tests on the strength and fracture energy of the adhesive bond lines. The main results obtained show that there is a potential for the production of green-glued laminated beams with good technical performance.
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| 33. |
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| 34. |
- Serrano, Erik, et al.
(författare)
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Green-Glued Products for Structural Applications
- 2014
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Ingår i: Materials and Joints in Timber Structures. - Dordrecht : Springer. - 9789400778108 ; 9, s. 45-55
-
Konferensbidrag (refereegranskat)abstract
- The results from bending tests on 107 laminated, green-glued, beams manufactured from Norway spruce side boards are presented. The beams were made by face gluing 21-25 mm thick boards using a commercial one-component moisture curing polyurethane adhesive. In addition to the bending test results, results from shape stability measurements after climatic cycling and bond line strength and durability test results are also presented. The results from the bending tests show that, by applying very simple grading rules, it is possible to obtain beams with high bending strength (with a 5%-percentile characteristic value of 40,1 MPa) and substantial stiffness (mean value of 14360 MPa). Also the shape stability of the beams and the strength and the durability of the interlaminar bonds were found to be satisfactory.
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| 35. |
- Serrano, Erik, 1968-, et al.
(författare)
-
Wet glued laminated beams using side boards of Norway spruce
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In a previous research project, carried out during the years 2006-2008, the possibility to manufacture wet glued laminated beams using ungraded laminations of Norway spruce side boards was investigated with very promising results.In the project presented in this report, the performance of the wet glued beams has been further investigated and developed as regards grading of side board laminations, bond line properties and lamination finger jointing. The possibility to use scanning equipment for measurement of fibre angles and prediction of strength and stiffness of boards and beams has been studied and the procedures for technical approval and CE marking have been probed into. Studies concerning market and economy for the beams and layouts for a pilot plant and a full capacity plant, respectively, for production of such beams have also been carried out.The possibility to grade side boards in the wet state using axial dynamic excitation was investigated with a positive result. From such excitation, a board’s stiffness (modulus of elasticity) could be determined. Accordingly, grading criteria regarding axial stiffness, and knot size, was applied to grade side board laminations into two classes; outer and inner laminations. Strength and stiffness tests of beams manufactured from such graded laminations showed that the beams actually could challenge first rate glulam and LVL products available on the market.Regarding beam shape and shape stability, cross section cupping may need further attention. Even if this deformation was small, it was still visible to the naked eye. The problem could probably be overcome if the beams are dried to a moisture content of 12-14% before planing.Results of shear tests show that green glued bond lines can fulfil strength requirements for glulam. However, delamination requirements for service class 3 (outdoors) were not fully met. From small scale tensile testing of glued bonds it was concluded that green glued bonds with high density wood have the same tensile strength and fracture energy as dry glued bonds. For bonds with low density wood and/or small amount of adhesive, the tensile strength could be lower than for dry glued bonds, whereas the fracture energy was on a similar level.Strength testing of wet and dry glued finger joints demonstrated that joints glued from high density wood was significantly stronger than low density joints and that there was no significant difference between the strength of green glued joints and joints glued after drying. From X-ray measurement it was shown that the glue penetration into the wood fibres is much deeper in a green glued joint than in a joint that is glued in the dried state.From scanning algorithms developed within the scope of this project it is possible to obtain reasonably accurate predictions of grain-angle distributions on board surfaces as well as rather accurate descriptions of knot locations and of fibre-angle disturbances around knots. From scanning of board ends, cross section characteristics with respect to radial and tangential directions and of annual ring widths could also be determined. Finally, both board and beam stiffness were predicted from this data, with an accuracy that is comparable with the one obtained from well-reputed commercial grading systems.
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| 36. |
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| 37. |
- Sterley, Magdalena
(författare)
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Adhesive systems for green gluing
- 2005
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Ingår i: Green gluing of wood-process-products-market. - : SP.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 38. |
- Sterley, Magdalena, et al.
(författare)
-
Adhesives for green gluing.
- 2008
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Ingår i: Bonding of timber: core document of the COST Action E34. - : Univ. für Bodenkultur Wien , 2008.
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 39. |
- Sterley, Magdalena, 1959-
(författare)
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Characterisation of green-glued wood adhesive bonds
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The gluing of unseasoned wood, called green gluing, is a relatively new sawmill process, implying a radically changed order of material flow in the production of value-added wood-based products. It facilitates the enhancement of raw material recovery and value yield by integrating defect elimination and gluing already before kiln drying. The present study evaluates green glued adhesive bonds in flatwise glued beams and finger joints. The main part of this work deals with green gluing using a moisture curing polyurethane adhesive (PUR). Standardised test methods and specially designed, small scale, specimens were used for the determination of the strength, fracture energy and the ductility of both dry- and green glued bonds in tension and in shear. Using the small scale specimens it was possible to capture the complete stress versus deformation curves, including also their unloading part. An optical system for deformation measurement was used for the analysis of bond behaviour. The influence of moisture content during curing and temperature after curing on the adhesive chemical composition and on the mechanical properties was investigated. Furthermore, the moisture transport through the adhesive bond during curing was tested. Finally, microscopy studies were performed for analysis of bond morphology and fracture. The results show that two significant factors influence the shear strength of green glued bonds: wood density and adhesive spread rate. Bonds which fulfil the requirements according to EN 386 could be obtained within a wide range of process parameters. The small specimen tests showed that green glued PUR bonds can reach the same strength and fracture energy, both in shear and in tension, as dry glued bonds with the same adhesive amount. The local material properties of the bonds could be determined, thanks to the failure in the tests taking place within the adhesive bond itself and not in the wood. Following process factors were shown to cause lower bond strength: a) a low adhesive spread rate, b) high pressure and c) short pressing time in combination with low wood density and high moisture content. Moreover, the heat treatment of the cured PUR adhesive during drying influenced the chemical composition of the adhesive, providing for higher strength, stiffness and Tg of the adhesive, caused by an increased amount of highly ordered bidentate urea.
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| 40. |
- Sterley, Magdalena, 1959-, et al.
(författare)
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Edge and face gluing of green timber using a one-component polyurethane adhesive
- 2004
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Ingår i: European Journal of Wood and Wood Products. - : Springer Berlin/Heidelberg. - 0018-3768 .- 1436-736X. ; 62:6, s. 479-482
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Tidskriftsartikel (refereegranskat)abstract
- The edge and face gluing of green timber using a one-component polyurethane adhesive was investigated. Knot free and straight grained lamellae of dimensions were prepared for this purpose. The relationship between final shear strength and wood failure percentage after kiln drying of the edge green glued specimens was shown. A slight increase of the shear strength was obtained for specimens tested 24 hour pressing compared with directly pressing.
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| 41. |
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| 42. |
- Sterley, Magdalena, 1959-, et al.
(författare)
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Finger jointing of freshly sawn Norway Spruce side boards : a comparative study of fracture properties of joints glued with phenol-resorcinol and one-component polyurethane adhesive
- 2014
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Ingår i: Materials and Joints in Timber Structures. - Dordrecht : Springer. - 9789400778108 ; 9, s. 325-339
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Finger jointing of unseasoned Norway Spruce was studied with respect to tensile strength, adhesive penetration and durability. Finger joints were manufactured with 1) unseasoned wood and one component polyurethane (PUR) adhesive, 2) dried wood and PUR adhesive and 3) dried wood and phenol resorcinol formaldehyde (PRF) adhesive. Two levels of wood density were used. The tensile strength of the finger joints was determined and the deformations within the joint were studied with an optical measurement system (ARAMIS). The penetration of the adhesive was studied with x-ray microtomography. The durability of the joints was determined according to the standard ASTM D 4688. The results show that the tensile strength and the durability of green glued finger joints are on the same level as that of dry glued PUR joints. The penetration of the PUR adhesive is high in the unseasoned wood and cavities within the bonds seem to be smaller than in dry glued PUR joints. The tensile strength of the finger joints is dependent on density, independent on the adhesive system used. The strength of the green glued PUR adhesive bonds in finger joints measured with small scale specimens did not differ from the strength of the dry glued PUR bonds.
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| 43. |
- Sterley, Magdalena, 1959-, et al.
(författare)
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Finger jointing of green Scots pine
- 2005
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Ingår i: Green gluing of wood- process – products – market : International conference / workshop, Borås, April 7-8, 2005. - Borås. - 9185533319 ; , s. 55-65
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Konferensbidrag (refereegranskat)abstract
- Finger jointing of green timber enables the wood industry to produce value-added products by using a new efficient process. Green finger jointing has gradually accelerated in New Zealand, USAand Canada, but is still relatively unknown in Europe. This study evaluates three green adhesive systems used with green Scots Pine timber: 1) a modified Phenol Resorcinol Formaldehyde (PRF) known as Greenweld®, 2) a one-component polyurethane adhesive and 3) a soy protein and PRF (soy/PRF) adhesive. Green adhesives have been compared with a conventional exterior PRF-Reference adhesive used with kiln-dried timber. The evaluation of mechanical performance was carried out with 4-point bending, according to EN 408. The warp of dried finger-jointed timber was measured in the form of bow, spring and twist and microscopy studies of glue lines were performed. The moisture durability of the adhesives was tested according to ASTM-D 4688-95. The tensile strength, WFP (Wood Failure Percentage) and failure modes were determined. Results showed that bending strength did not differ either between green adhesive systems and PRF-Reference dry system, or among green adhesives themselves. The warp of dried timber was on the same level for green glued finger joints and for conventional finger joints. The durability test showed that the PUR adhesive used in the green process had highest dry tensile strength compared to the other tested adhesives. The wet tensile strength after accelerated aging of all four adhesives did not differ significantly. The dry WFP without any treatment was high for all three adhesives used for green gluing and did not differ from the PRF-Reference. However, the wet WFP after cyclic boiling treatment of the green adhesive systems turned out to be lower than the wet WFP of the PRF-Reference adhesive. The results of the failure mode also illustrate that the green adhesives glue line of the wet specimens failed more often in the interface between wood and the adhesive than those with the PRF-Reference adhesive. Additionally, microscopy studies of the glue lines revealed that the penetration of polyurethane adhesive was deepest, Greenweld’s penetration was similar to PRF-Reference and sapwood glue lines of green adhesives had more cavities than heartwood glue lines.
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| 44. |
- Sterley, Magdalena
(författare)
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Finger jointing of green Scots Pine
- 2005
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Ingår i: Proceedings COST E34 Conference Green gluing of wood..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 45. |
- Sterley, Magdalena, 1959-, et al.
(författare)
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Flat wise green gluing of Norway spruce for structural application
- 2009
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Ingår i: International Conference on Wood Adhesives 2009. - Madison : Forest Products Society. - 9781892529572 - 9781617389863 ; , s. 325-334
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Konferensbidrag (refereegranskat)abstract
- Unseasoned (green) Spruce timber planks with dimensions25 x 150 x 5400 mm3 were flat-wise glued with a one-componentPUR adhesive, forming laminated beams with 150 x 300 mm2 crosssection.After curing, each beam was divided in two halves and subsequentlydried. The final cross-section of the beams was thus 50 x 300mm2. The evaluation of the beams included bending stiffness andbending strength in 4-point bending and the mechanical properties ofthe adhesive bonds. The adhesive bonds were tested according toEuropean standards for glued-laminated timber (EN 392, EN 391) andaccording to ASTM D 905, but also with a special small-scale specimenfor testing the fracture properties of the adhesive bond in Mode I.The complete force vs. deformation curve, including both the ascendingand the descending parts could be obtained. The deformationswere measured with a contact-free technique, based on two camerasand white light. The equipment made it possible to register the strainin the bond line and in the adjacent wood with a high spatial resolution(0,2 mm). The strength of the bond line and the fracture energywas calculated. Results show that both the stiffness and the strength ofthe beams can comply with the requirements for glued-laminated timberclass L40. The adhesive bonds fulfill the requirements of glulam instandard EN 386. The tensile strength and fracture energy measuredwith the small specimens of green-glued bond lines is on the samelevel as of conventionally glued bond lines.
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| 46. |
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| 47. |
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| 48. |
- Sterley, Magdalena, 1959-, et al.
(författare)
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Fracture characterisation of green glued-polyurethane adhesive bonds in Mode I
- 2013
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Ingår i: Materials and Structures. - : Springer Science and Business Media LLC. - 1359-5997 .- 1871-6873. ; 46:3, s. 421-434
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Tidskriftsartikel (refereegranskat)abstract
- Unseasoned (green) spruce timber side boards of size 25 × 120 × 600 mm were flatwise-glued with a one-component PUR adhesive. Glued pairs of boards were then kiln-dried to 12 % moisture content. A special small-scale specimen for testing the fracture properties of the adhesive bond in Mode I was developed in order to evaluate the adhesive bond properties. The complete force versus deformation curve, including both the ascending and the descending parts, could be obtained with these small-scale specimens, enabling the strength and fracture energy of the bond line to be calculated. In addition, the fractured specimens were examined by scanning electron microscope. Results show that both the tensile strength and the fracture energy of the green glued PUR adhesive bonds were equal to those of the dry glued bonds. The methodology developed and used in the present study gives new possibilities for analysis of the mechanical behaviour of wood adhesive bonds, and particularly of their brittleness and its correlation with the type of fracture path. This is in sharp contrast to the use of standardised test methods (e.g. EN 302, ASTM D905) with specimens having relatively large glued areas. Using such types of specimens, it is not possible to obtain the complete force versus deformation response of the bond. In addition, when using such test methods, failure takes place in the wood or in the fibres near the bond, thus making it impossible to obtain detailed information about the bond line characteristics.
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| 49. |
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| 50. |
- Sterley, Magdalena
(författare)
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Green gluing of wood
- 2004
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)
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