| 1. |
- Gaff, Milan, et al.
(författare)
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The effect of chemical changes during thermal modification of European oak and Norway spruce on elasticity properties
- 2019
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Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 220, s. 529-538
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Tidskriftsartikel (refereegranskat)abstract
- The elasticity in bending of European oak (Quercus robur L.) and Norway spruce (Picea abies (L.) Karst.) timber was evaluated before and after thermal modificationand related to the changes in chemical composition of the wood as a result of the modification. A new software was developed (MATESS) and used to identify characteristic points on the force-deformation diagram. The modulus of elasticity(MOE), stress at the limit of proportionality (LOP) and elastic potential (PE) were used to describe the wood properties. Extractives, lignin, cellulose, holocellulose, and hemicelluloses were analysed to reveal the patterns that occur during the loading of the specimens. Thermal modification lowers the mechanical properties (MOE, LOP and PE) of oak and spruce wood, and the reduction increases with increasing modification temperature. Changes in chemical composition of thermally modified wood show a strong relationship to the reduction in elasticity properties for bot species.
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| 2. |
- Bachtiar, Erik Valetine, et al.
(författare)
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Properties of adhesive films used in cultural assets
- 2022
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 17:2, s. 147-150
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Tidskriftsartikel (refereegranskat)abstract
- The hygroscopic nature of wood leads to large moisture fluctuations in the material that may influence the mechanical performance of glued wood products. Adhesives based on bone, fish and hide have a long tradition for the gluing of wood and can be found in wooden structures in our cultural heritage. In this study, selected sorptive and mechanical properties of animal adhesives have been compiled and compared to those of synthetic polyurethane adhesives. Bone, fish and hide adhesives show a high moisture uptake at high relative humidity, which confirms the low moisture resistance of such adhesives. The modulus of elasticity and ultimate tensile strength of the films based on animal adhesives are considerably reduced when the moisture content is increased.
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| 3. |
- Bernaczyk, Arkadiusz, et al.
(författare)
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Investigations into the Influence of Temperature on the Tensile Shear Strength of Various Adhesives
- 2023
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Ingår i: Materials. - : Multidisciplinary Digital Publishing Institute (MDPI). - 1996-1944. ; 16:18
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Tidskriftsartikel (refereegranskat)abstract
- The temperature resistance of glued timber, which is crucial for glued wood construction, represents a significant assessment criterion. To gain insights into this aspect, this study utilized methods such as a shear strength test in accordance with EN 302-1:2013-06 under thermal loading (from 20 °C to 200 °C), and Differential Scanning Calorimetry (DSC) to determine the glass transition temperature (Tg). An increase in thermal load resulted in a decrease in shear strength and an increase in wood breakage. A hierarchy of adhesive groups was established based on strength performance and wood failure percentage (WFP) at 200 °C. Thermoset adhesives (MF: Melamine Formaldehyde, PRF: Phenol Resorcinol Formaldehyde) led the ranking, followed by elastomer adhesives (1C-PUR: One-Component Polyurethane, EPI: Emulsion Polymer Isocyanate), with thermoplastic adhesive (PVAc: Polyvinyl Acetate) last. Thermoset adhesives further cured under heat. PUR adhesives exhibited higher strength performance at 150 °C and lower temperatures.
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| 4. |
- Bernaczyk, Arkadiusz, et al.
(författare)
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Investigations on the Characterization of Various Adhesive Joints by Means of Nanoindentation and Computer Tomography
- 2022
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Ingår i: Materials. - : MDPI. - 1996-1944. ; 15:23, s. 8604-8604
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical properties of cured wood adhesive films were tested in a dry state by means of nanoindentation. These studies have found that the application of adhesives have an effect on the accuracy of the hardness and elastic modulus determination. The highest values of hardness among the tested adhesives at 20 °C have condensation resins: MF (0.64 GPa) and RPF (0.52 GPa). Then the decreasing EPI (0.43 GPa), PUR (0.23 GPa) and PVAc (0.14 GPa) adhesives. The values of the elastic modulus look a little bit different. The highest values among the tested adhesives at 20 °C have EPI (11.97 GPa), followed by MF (10.54 GPa), RPF (7.98 GPa), PVAc (4.71 GPa) and PUR (3.37 GPa). X-ray micro-computed tomography was used to evaluate the adhesive joint by the determination of the voids. It has been proven that this value depends on the type of adhesive, glue quantity and reactivity. The highest values of the void ratio achieve the PUR (17.26%) adhesives, then PVAc (13.97%), RRF (6.88%), MF (1.78%) and EPI (0.03%). The ratio of the gaps increases with the higher joint thickness. A too high proportion of voids may weaken the adhesive joint.
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| 5. |
- Bjurhager, Ingela, et al.
(författare)
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Mechanical performance of yew (Taxus baccata L.) from a longbow perspective
- 2013
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 67:7, s. 763-770
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Tidskriftsartikel (refereegranskat)abstract
- Yew (Taxus baccata L.) longbow was the preferred weapon in the Middle Ages until the emergence of guns. In this study, the tensile, compression, and bending properties of yew were investigated. The advantage of yew over the other species in the study was also confirmed by a simple beam model. The superior toughness of yew has the effect that a yew longbow has a higher range compared with bows made from other species. Unexpectedly, the mechanical performance of a bow made from yew is influenced by the juvenile-to-mature wood ratio rather than by the heartwood-to-sapwood ratio. A yew bow is predicted to have maximized performance at a juvenile wood content of 30-50%, and located at the concave side (the compressive side facing the bowyer). Here, the stiffness and yield stress in compression should be as high as possible.
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| 6. |
- Blomqvist, Lars, 1962-
(författare)
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Laminated Veneer Products : Shape Stability and Effect of Enhanced Formability on Bond-Line Strength
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns two aspects of the manufacture of laminated veneer products (LVPs). The first aspect is related to the possible improvement of the shape stability of LVPs, and the second has its starting point in the modification of the veneer for enhanced formability as well as the question of whether and how these modifications affect the bond-line strength.LVPs are veneers bonded with adhesive into predetermined shapes, mostly for the production of furniture and interior fittings. Since any deviation from the intended shape is a problem for both manufacturer and customer, various studies have sought to evaluate the influence of different materials and process parameters on shape stability. Parameters studied have included wood species (beech and birch), an adhesive system based on urea formaldehyde, the adhesive distribution on the veneer, climate, moisture content and fibre orientations of the veneers, as well as the orientation of the individual veneers in a multiply.Manufacturers of LVPs must consider some basic facts about wood in orders adequately to provide shape-stable LVPs to customers. Wood emits and absorbs moisture in relation to the surrounding climate, and this can lead to shrinkage and swelling. Such moisture induced movements differ in the wood’s different directions, and the magnitude is specific for the species. A thorough understanding of this is the basis for achieving shape-stable LVPs.Symmetry is defined in this thesis such that the veneer properties are balanced in the laminate. This means that opposite veneers on either side of the centre veneer have similar characteristic. An LVP will become distorted if the veneers are asymmetrically oriented before the press. Deviation from the desired shape can be small immediately after the pressing, but it may increase significantly with moisture content (MC) variations. Asymmetry may result when veneers with different fibre orientations are included in the laminate or when the veneers are placed asymmetrically. It may also occur if veneers with different MCs are bonded together asymmetrically. One aggravating factor is that the lathe checks that are introduced when the veneers are peeled or sliced from the log affect the shape stability. In 3-ply crosswise-oriented plywood, the veneer surfaces on which the lathe checks occur should be oriented in the same way for high shape stability.Based on existing knowledge, the production of shape-stable LVPs requires that the veneers are conditioned to a uniform MC and sorted with regard to fibre orientation and the side with lathe checks before bonding. End-user climates should govern the MC of the veneers and the moisture added with the adhesive during the process. Straight-grain veneers and symmetry should always be the goal.Moulding can cause stretching, i.e. strain, of the veneers depending on the curvature of the mould. To prevent the veneers from rupture, there are various ways to strengthen the veneers particularly in the transverse direction in which the veneer is weakest. However, tests have shown that these pre-treatments of veneers for enhanced formability can prevent the adhesive from penetrating the wood surface. It is therefore important to confirm that the pre-treatment does not affect the bond-line strength.
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| 7. |
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| 8. |
- Blumer, Samuel, et al.
(författare)
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Moisture induced stresses and deformations in parquet floors : An experimental and numerical study
- 2009
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Ingår i: Wood research. - Slovakia : State Forest Products Research Inst. - 1336-4561. ; 54:1, s. 89-101
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Tidskriftsartikel (refereegranskat)abstract
- The indoor climate in buildings has changed in the last decade due to more efficient climatic systems, floor heating systems and larger open floor areas with more natural light. All this has induced increasing ranges of relative humidity between different seasons. Also with decreasing relative humidity (in the winter 30-50% RH, in the summer 70-90% RH), floor-heating systems increase the temperature in wooden parquet planks for example. Such variations can result in troublesome deformations, delamination of the surface layer and development of cracks in the parquet flooring boards. Sometimes there is only deterioration of the appearance but the durability of the flooring system can also be reduced. Many laboratory tests have to be done before reaching an optimal design of the parquet elements. Due to high coasts and time constraints of experiments, other supplementary research methods should be tested and evaluated. The articles' main objective was to increase understanding of the behaviour of parquet floors exposed to different climatic conditions using numerical calculation. The use of the finite element models provides options for design purposes of wood flooring systems. Several finite element models for adequate design have been created, tested and applied. After calibration and validation of the calculation method, parameter studies on the influence of material properties, geometry of the parquet floors and the long-term behaviour of the wood and glue line were performed. The results show a strong relation between material and geometry choice on the deformation, for example the gap opening and on the stress distribution in glue line, which can induce delamination of the surface layer and distortional effects of the parquet boards
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Deliiski, Nencho, et al.
(författare)
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A methodology for computing the relative icing degrees of logs stored in an open warehouse at ambient air temperature in winter
- 2021
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 16:6, s. 421-428
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a methodology for mathematical modeling, computing, and research of two mutually connected problems: 2D non-stationary temperature distribution in logs stored for a long time in an open warehouse at periodically changing ambient air temperature in winter and change in the icing degrees of the logs during this time. Mathematical descriptions of the periodically changing ambient air temperature and of three types of relative icing degree of the logs that result under the influence of that temperature have been presented. These descriptions are introduced in coupled 2D non-linear mathematical models of the heat distribution in logs during their freezing and defrosting. The paper presents solutions of the models with explicit form of the finite-difference method. Results from a simulative investigation of the 2D non-stationary temperature distribution, average mass temperature, and three types of icing degree of beech logs with industrial dimensions (diameter of 0.4 m and length of 0.8 m), moisture content of 0.6 kg·kg−1, and initial temperature of 0°C during their 5 days and nights alternating freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial values below −5°C and different amplitudes are graphically presented and analyzed.
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| 13. |
- Deliiski, Nencho, et al.
(författare)
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A Simulation Study Of The Heat Balance Of Concrete Pits During Boiling Of Non-Frozen Logs
- 2023
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Ingår i: Bulletin of the Transilvania University of Brasov, Series II: Forestry, Wood Industry, Agricultural Food Engineering. - : Transilvania University Press. - 2065-2135 .- 2971-9372. ; 16(65):3 Special Issue, s. 67-82
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents an approach for computing the heat balance of boiling pits during plasticising of non-frozen logs intended for the production of peeled veneer. With the help of our own non-stationary model, the heating times of beech logs with a diameter of 0.4 m, an initial temperature of 10°C, and a moisture content of 0.6 kg∙kg-1 were determined at water temperatures in the pit equal to 70, 80, and 90°C. Using the determined logs’ boiling durations and the mentioned approach, the change in the total energy required to carry out the entire boiling process and that required for each of the individual components of the heat balance was calculated. Computer simulations were conducted for a concrete pit with overall dimensions of 8.0 × 2.6 x 2.5 m, working volume of 20 m3, and a degree of filling with logs equal to 45, 60, and 75%. It was found that the increase in the water temperature from 70 to 90°C causes an increase in the total specific energy, as well as in the energy for the heating of the logs themselves, the construction and the water of the pit. At the same time, the energy required to cover the heat losses of the pit decreases and the energy for heating the metal heater/radiator itself does not change. A decrease in the degree of filling of the pit with logs from 75 to 45% causes an increase in both the total energy and all its components except the energy for heating the logs, which remains unchanged.
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| 14. |
- Deliiski, Nencho, et al.
(författare)
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An approach for computing the specific heat capacities of logs stored for a long time in an open warehouse
- 2022
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 17:5, s. 376-385
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes an approach for computing the specific heat capacities of logs stored for long in an open warehouse. It includes the heat capacities of the wood of non-frozen and frozen zones in the logs and of both the frozen free and bound water in these zones, also the capacities formed by the release of the latent heat of both the free and bound water during their crystallization, as well as the effective specific heat capacities of logs stored in an open warehouse at periodically changing air temperature. The approach is based on the solutions of 2D models of the temperature distribution in logs during their alternating heating and cooling. Results from a simulative study of 2D unsteady temperature distribution and all types of the specific heat capacities of beech logs with a diameter of 0.4 m, length of 0.8 m, moisture content of 60%, and initial temperature of 0°C and 20°C during their 5 days and nights continous alternating heating, cooling, freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial and different amplitudes in the range from –25°C to 40°C are graphically presented and analyzed.
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| 15. |
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| 16. |
- Deliiski, Nencho, et al.
(författare)
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An engineering approach for calculating the energy required for defrosting and subsequent heating of frozen wood during thermal treatment
- 2024
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 19:3, s. 811-820
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Tidskriftsartikel (refereegranskat)abstract
- An approach for calculating the energy required for defrosting and subsequent heating of frozen wood during thermal treatment in the production of veneer has been presented. Using two own unsteady models the duration of regimes for steaming of prisms in an autoclave and for boiling of logs in a pit, and also the average mass temperature of the prisms and logs and the energy accumulated by them at the end of heat carrier introduction in these regimes was determined. The obtained values of average temperature were introduced in third own model for engineering calculation of the energy considered in the approach. Computer simulations were carried out for beech prisms with a cross section of 0.4 × 0.4 m and beech logs with a diameter of 0.4 m at an initial wood temperature of −10°C, −20°C, and −30°C and moisture content of 0.6 kg·kg−1. The operating temperature of the prism steaming regimes was equal to 130°C, and that of the log boiling regimes was 80°C. The approach can be applied using Excel for computing the energy and its components needed for defrosting and heating of different frozen capillary-porous materials subjected to multiple types of thermal treatment.
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| 17. |
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| 18. |
- Deliiski, Nencho, et al.
(författare)
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Computing the Thermal Efficiency of Autoclaves during Steaming of Frozen Prisms for Veneer Production at Changing Operational Conditions
- 2023
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Ingår i: Processes. - : MDPI. - 2227-9717. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for the computation of the thermal energy efficiency of modes for the heat treatment of frozen wooden prisms in an autoclave with saturated water vapor at changing operational conditions has been proposed. The methodology includes computer simulations with two own-coupled unsteady models: one to calculate the 2D temperature distribution in the cross-section of prismatic wood materials during their heat treatment, and the second to determine the heat balance of industrial autoclaves for such wood treatment. Simulations were carried out in order to determine the duration, energy consumption, and thermal efficiency of different modes, caused by changed operational conditions, for the autoclave steaming of frozen beech prisms with industrial parameters in the absence and presence of dispatcher intervention. The influence of nine combinations between the time of dispatcher intervention and the degree of reduction of the constant maximum temperature from the 130 °C of the basic mode on the thermal efficiency of the autoclave was investigated. The results show that all studied dispatching interventions cause an increase in both the duration and the thermal efficiency of the modes. This efficiency in the modes at changing operational conditions has values between 68.7% and 74.6%, while the efficiency in the basic steaming mode is equal to 68.0%.
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| 19. |
- Deliiski, Nencho, et al.
(författare)
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Influence of selected factors on the energy consumption of frozen logs subjected to thermal treatment in veneer production
- 2024
-
Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280.
-
Tidskriftsartikel (refereegranskat)abstract
- This study puts forward an approach for calculating the specific energy consumption and its components required for heating of frozen logs for veneer production, depending on the logs’ initial temperature and moisture content. The approach is based on the use of two personal models: unsteady model of the temperature distribution along the radius of frozen logs during their thermal treatment and stationary model of the energy consumption of logs subjected to such treatment as a function of its four multifactorial components. The influence of all combinations between five values of the initial temperature of frozen logs from −1 oC to −40 oC and three values of their moisture content from 0.4 kg·kg−1–0.8 kg·kg−1 on the specific energy required to heat and placticize beech logs with a diameter of 0.4 m at operating temperature of the steaming or boiling medium of 80 oC was investigated. The obtained results show that this energy changes in the range from 46 kWh·m−3 (at −1 oC and 0.4 kg·kg−1) to 114 kWh·m−3 (at −40 oC and 0.8 kg·kg−1) The approach could be applied to calculate the energy and its components required for carrying out of the thermal treatment of various frozen capillary-porous materials.
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| 20. |
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| 21. |
- Deliiski, Nencho, et al.
(författare)
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Research on the simultaneous steaming in an autoclave of non-frozen beech prisms with different thicknesses intended for production of veneer
- 2022
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Ingår i: Acta facultatis xylologiae Zvolen. - : Technická univerzita vo Zvolene. - 1336-3824. ; 64:1, s. 69-80
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Tidskriftsartikel (refereegranskat)abstract
- An approach to mathematical modeling and research on the 2D non-stationary temperature distribution in non-frozen wooden prisms with different thicknesses during their simultaneous autoclave steaming at limited heat power of the steam generator and during the subsequent air conditioning before the cutting of veneer is described in the paper. Mathematical descriptions of the changing processing medium temperature in an autoclave and near the steamed prisms out of the autoclave were introduced as boundary conditions in our own 2D non-linear mathematical model of the 2D temperature distribution in non-frozen prisms during their heating and cooling. Numerical solutions of the model in the calculation environment of Visual FORTRAN Professional are given as an application of the suggested approach. Simulative investigation of 2D non-stationary temperature distribution in non-frozen beech (Fagus Sylvatica L.) prisms with an initial temperature of 0 °C, cross-section dimensions of 0.3 × 0.3 m, 0.4 × 0.4 m, and 0.5 × 0.5 m, moisture content of 0.4, 0.6, and 0.8 kg·kg-1, during their autoclave steaming and subsequent conditioning was carried out. The simultaneous steaming of all prisms was simulated according to regimes for prisms with cross-section dimensions of 0.5 × 0.5 m in an autoclave with a diameter of 2.4 m, length of 9.0 m and loading levels of 40, 50, and 60% at a limited heat power of the steam generator, equal to 500 kW. It was found that good quality veneer could be obtained after simultaneous steaming of prisms of the same wood species with differences between their thicknesses up to 100 mm. It is necessary to carry out the steaming according to the regime that applies to the prisms with the largest thickness in a given batch. Then the effect of the wood moisture content and loading level of the autoclave on the plasticization degree of the prisms and the veneer quality is practically negligible. The suggested approach can be used for the computation and model based automatic realization of energy-efficient optimized regimes for autoclave steaming of different wood materials.
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| 22. |
- Gereke, Thomas, et al.
(författare)
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Experimental and numerical determination of the hygroscopic warping of cross-laminated solid wood panels
- 2009
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Ingår i: Holzforschung. - 1437-434X. ; 63:3, s. 340-347
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Tidskriftsartikel (refereegranskat)abstract
- The moisture-induced warping of three-layered cross-laminated solid wood panels made of Norway spruce was studied. The panels were exposed to different climate conditions at 65% and 100% relative humidity at the two panel faces. The results showed increasing cup deformation with an increasing relative thickness of the outer layers. The annual growth ring orientation was found to have a significant influence on the magnitude of the cup deformation. Measurements and numerical simulations of the moisture distribution within the panel were made in order to provide data for numerical simulations of the warping. A distinctive moisture profile with a conspicuous influence of the adhesive bond lines was found. The coefficient of diffusion of the adhesive bond lines was determined from the measurements and simulations. The mechanical material model used for the warping simulations takes into account elastic strain, moisture-induced swelling, and mechano-sorptive strain. The simulations showed good agreement with the warping test results. The most important material parameters for the cup deformation, which were identified in a parametric study of a panel with vertically oriented annual rings, are the moduli of elasticity and the swelling coefficients in the longitudinal and radial direction. Furthermore, the mechano-sorptive coefficient in radial direction was found to have a significant influence on warp.
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| 23. |
- Ghorbanian Far, Mohammad, et al.
(författare)
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Physical and mechanical properties of different beech wood species grown at various climate conditions: a review
- 2024
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 78:7, s. 377-386
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Forskningsöversikt (refereegranskat)abstract
- Beech wood, renowned for its diverse applications spanning construction, flooring, furniture, veneer, and plywood, holds a paramount position among industrial wood species. Nevertheless, the myriad of beech species worldwide, coupled with the dynamic impact of climate change, have produced structural variations within beech trees. Extensive research has scrutinized the physical and mechanical attributes of beech wood species across the globe. Findings reveal distinguishable mechanical strength, yet increased density leads to notable rates of shrinkage and swelling, somewhat constraining its utility in select domains. Identifying research gaps can create new efforts aimed at exploiting the potential of these wood resources. This paper outperforms a mere exploration of beech wood properties over the past two decades; it delves into the ramifications of climatic fluctuations, temperature shifts, wind dynamics, and soil composition. Given the lack of a comprehensive compendium documenting the full range of physical, mechanical, and microscopic attributes of the Fagus genus, this paper aims to compile information that integrates this multifaceted information.
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| 24. |
- Hänsel, Andreas, et al.
(författare)
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Influence of surface treatment on the bonding quality of wood for load-bearing purposes
- 2023
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 18:6, s. 2128-2139
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the influence of different machining processes on the tensile shear strength of glued lumber, focusing on optimizing the tool geometry of face milling. The data obtained were analyzed using statistical methods. The roughness of the surface produced by the machining process and the damage to the microstructure under the cutting edge are identified as important factors influencing the quality of the bond. The results show that the optimized process (low roughness and microstructure damage) leads to more effective gluing.
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| 25. |
- Hänsel, Andreas, et al.
(författare)
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Selected previous findings on the factors influencing the gluing quality of solid wood products in timber construction and possible developments: A review
- 2022
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 17:3, s. 230-241
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Forskningsöversikt (refereegranskat)abstract
- Various factors affect the bonding quality of elements used for timber construction. This review includes literature studies and personal experiences related to relevant technological variables defining glue bond performance in glue-laminated timber elements during their service life. The gluing of hardwood species receives special focus as it is considered by the industry to be the most challenging process for implementation. In particular, the effects of wood species, type of adhesive, glued-wood surface quality, physical and/or chemical modification of the wood, technological solutions for gluing, and varying climatic conditions during the use phase (relative humidity, temperature, air circulation, etc.) are considered. In addition, overlapping of individual influencing factors often leads to problems with bonding, thus requiring strongly integrating measurement methods (e.g. NIR spectroscopy). The causes of variations in the results when glued wood is tested using different standardized methods are discussed. A list of open research questions is provided, and problem solutions are recommended based on systematized cutting-edge knowledge. The aim of the work is to systematize the state of knowledge of wood gluing to create a basis for controlled and stable manufacturing processes. The progress of the work will be reported in further publications.
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| 26. |
- Källander, Björn
(författare)
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Drying and thermal modification of wood - studies on influence of sample size, batch size, and climate on wood response
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research on wood drying and wood modification is primarily done in laboratories, using clear wood specimens treated under well-defined conditions in laboratory cabinets. Laboratory tests differ from industrial treatment both regarding the size and homogeneity of the material treated, and the size of the batch and kiln used.Knowledge about how the size of the material treated and the size of the batch or kiln influence the results is limited, which makes it difficult to utilize results from laboratory research in development of industrial processes. A better understanding of the influence of size can also improve the possibilities to design laboratory studies so that the results are easier to implement industrially.The studies presented in this thesis focus on how the size of the batches treated and the size of the individual wood samples treated influence the process and resulting properties of the wood. The aim of the studies, the so called researchquestion in the context of a PhD-thesis, is to help transfer knowledge gained from testing small wooden samples in laboratories to industrial treatment of full size timber.This thesis describes studies on vacuum drying, high temperature (HT) drying, and thermal modification of wood according to the Thermowood© process. Drying and thermal modification of wood have been studied under industrial andlaboratory conditions. Kiln climates and wood response have been determined during vacuum drying, conventional drying, high temperature drying, and thermal modification.The results show that both the size of the material treated and the size of the kiln or batch strongly influence the processes and the resulting wood properties.The results show that the sample size influences different material properties in different ways. Equilibrium moisture content is reduced less during thermal treatment of small clear wood specimens than during treatment of dimensionaltimber. Mass loss on the other hand is higher in small samples. Reduction in impact bending strength, mass loss, and reduction in EMC after thermal treatment of dimensional timber do not seem to be correlated.Laboratory treatment of small clear wood specimens show considerably stronger influence on the wood properties than treatment of similar samples together with industrial production.
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| 27. |
- Mai, Carsten, et al.
(författare)
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A brief overview on the development of wood research
- 2022
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 76:2, s. 102-119
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Tidskriftsartikel (refereegranskat)abstract
- Wood science covers in particular the areas of the formation and composition as well as the chemical, biological and physical-mechanical properties of wood. First comprehensive studies have already been published in the last century. Detailed knowledge of wood is required for the processing of wood, the production of wood-based materials, and the utilization of wood and wood-based materials as buildings and various other products such as furniture. This review gives a brief overview on the progress in wood chemistry, wood biology (including photosynthesis and biodeterioration), and physical-mechanical properties of wood and wood-based materials. These fundamentals are also essential for understanding technological processes and product development.
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| 28. |
- Moanda, Destin Bamokina, et al.
(författare)
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Investigation of the Impact of Micro-Structuring on the Bonding Performance of Beechwood (Fagus Sylvatica L.)
- 2022
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Ingår i: Forests. - : MDPI. - 1999-4907. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Although glueing softwood is well mastered by the industry, predicting and controlling bond quality for hardwood is still challenging after years of research. Parameters such as the adhesive type, resin–hardener ratio, and the penetration behaviour of the wood are determinants for the bond quality. The aim of this work was to assess to what extent the glueing behaviour of beechwood can be improved by using structural planing. The different surfacing methods were characterised by their roughness. The bond strength of the micro-structured surfaces was determined according to EN 302-1, and the delamination resistance was tested as indicated by EN 302-2 for type I adhesives. Micro-structured surfaces were compared with different surfaces (generated by surfacing methods such as dull/sharp planing and sanding). In dry test conditions, all surfacing methods gave satisfying results. In the wet stage, the bond strength on the finer micro-structured surface slightly outperformed the coarse structure surface. For the delamination resistance, a clear improvement could be observed for melamine-formaldehyde-bonded specimens since, when using the recommended amount of adhesive, micro-structured surfaces fulfilled the requirements. Nevertheless, structural planing cannot lead to a reduction in the applied grammage since no sample with a smaller amount fulfilled EN 302-2 requirements even by observing the recommended closed assembly waiting time. Adhesion area enlargement of the micro-structuring is minor. The good delamination performance without waiting time (CAT) is not caused by surface enlargement, since finer micro-structured surface with negligible area increase and delivered even better delamination resistance. Subsurface analysis should be carried out to thoroughly investigate this phenomenon.
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| 29. |
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| 30. |
- Niemz, Peter, et al.
(författare)
-
Creep Behaviour of Wood and Wood-Based Materials: Recent Advances in the State-Of-The-Art and Open Questions.
- 2023
-
Ingår i: Pro Ligno. - : Transilvania University Press Brasov. - 1841-4737 .- 2069-7430. ; 19:4, s. 38-48
-
Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of wood and wood-based materials are becoming increasingly important both in timber construction, and in furniture and interior design. The topic has already been intensively researched in the 1970s and 1980s. In the context of work on modelling stresses and deformations, and the development of new engineered wood products (EWPs), investigations in this topic have been intensified in recent years. Several projects are ongoing, mostly concerning basic research on the rheological properties on solid wood. The objective of this study was to give an update on the state-of-the-art on creep behaviour of wood and wood-based materials, and to present some research questions relevant for the further development of the field. Characteristic values for Kdef, i.e. correction factors to be taken into account due to creep of the material according to Eurocode 5, are usually used as a characteristic value in the timber construction. Because of the following reasons, basic studies on rheological properties of wood and woodbased materials are still largely lacking:● the development of new EWPs, especially from hardwoods, ● the use of new adhesive systems and the related change in adhesive properties,● the reduction of formaldehyde content in adhesives for particleboard and medium-density fibreboard (MDF), and● the increased use of waste wood and recycled wood in particleboard production (up to 100% particles may be based on waste wood or recycled wood).
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| 31. |
- Niemz, Peter, et al.
(författare)
-
Critical wood-particle properties in the production of particleboard
- 2022
-
Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 17:5, s. 386-387
-
Tidskriftsartikel (refereegranskat)abstract
- Particleboard is an important base-material in furniture and building applications and its annual production capacity worldwide is over 100 million m3. Wood is the main raw material used, although the feasibility of non-wood alternatives exists. This technical note summarises information about how wood-particle geometry affects the bulk density and mat density, two important parameters in the particleboard production.
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| 32. |
- Niemz, Peter, et al.
(författare)
-
Important Data
- 2023
-
Ingår i: Springer Handbook of Wood Science and Technology. - : Springer Science and Business Media Deutschland GmbH. - 9783030813147 - 9783030813154 ; , s. 1977-2003
-
Bokkapitel (refereegranskat)abstract
- This chapter is an Appendix that provides information on material and process parameters. The data may constitute a basis for a first approximation in calculations of material characteristics and production capacities, etc. The presentation is in tabular form, sometimes with indications of the variation range. Data are presented for solid wood of different species and from different parts of the world, modified wood, and wood-based materials. Information on natural fibers, adhesives, and coating materials is also provided. For some selected processes, values for material and energy consumption during the production of materials such as sawn timber, wood-based materials, paper pulp, and paper are also presented. The chapter also contains an overview of standardization in different regions of the world, and a compilation of useful books in the field of wood science and technology.
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| 33. |
- Niemz, Peter, et al.
(författare)
-
Investigations on the sorption behaviour of selected wood species from Cameroon
- 2022
-
Ingår i: MADERAS. - : Universidad del Bío-Bío. - 0717-3644 .- 0718-221X. ; 24
-
Tidskriftsartikel (refereegranskat)abstract
- The sorption isotherms during adsorption and desorption of 25 wood species from Cameroon (included 3 species from plantation in Togo) were determined. In addition, the chemical compositions of these wood species were tested. The equilibrium moisture contents in a normal climate varied between 10,55 % and 15,6 %. A clear influence of the proportion of extractives can be seen. The maximum differences between adsorption and desorption varied between 2,3 % and 3,6 %.
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| 34. |
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| 35. |
- Niemz, Peter, et al.
(författare)
-
Preface
- 2023
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Ingår i: Springer Handbook of Wood Science and Technology. - : Springer Nature. ; , s. vii-viii
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 36. |
- Niemz, Peter, et al.
(författare)
-
Selected mechanical and physical properties of cherry and walnut wood
- 2022
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Ingår i: 10th Hardwood Conference Proceedings. - : University of Sopron Press. ; , s. 54-61
-
Konferensbidrag (refereegranskat)abstract
- Comprehensive work is in progress to preserve wood cultural assets in, for example, museums. Numerical simulation, namely finite element method (FEM), is performed to model the impact of climate change to avoid unnecessary damage in the objects. Material parameters for adhesives and coating materials, and mechanical properties along the three main axes (longitudinal, radial and tangential) of wood are then required for the modelling. In the present work, the modulus of elasticity, shear modulus, Poisson’s ratio and ultimate strengths, in the three main directions and in various moisture conditions were experimentally estimated for cherry (Prunus avium L.) and walnut (Juglans regia L.) wood, which are common species used in cultural assets and furniture. Characteristic values for Norway spruce (Picea abies L.) were also listed for comparison. Based on these data, orthotropic elastic deformation bodies were calculated. Furthermore, the sorption behaviour, the swelling and the diffusion resistance (dry and wet cup method) were also determined.
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| 37. |
- Niemz, Peter, 1950-, et al.
(författare)
-
Springer Handbook of Wood Science and Technology.
- 2023
-
Bok (refereegranskat)abstract
- This handbook provides an overview on wood science and technology of unparalleled comprehensiveness and international validity.It describes the fundamental wood biology, chemistry and physics, as well as structure-property relations of wood and wood-based materials. The different aspects and steps of wood processing are presented in detail from both a fundamental technological perspective and their realisation in industrial contexts. The discussed industrial processes extend beyond sawmilling and the manufacturing of adhesively bonded wood products to the processing of the various wood-based materials, including pulp and paper, natural fibre materials and aspects of bio-refinery. Core concepts of wood applications, quality and life cycle assessment of this important natural resource are presented. The book concludes with a useful compilation of fundamental material parameters and data as well as a glossary of terms in accordance with the most important industry standards.Written and edited by a truly international team of experts from academia, research institutes and industry, thoroughly reviewed by external colleagues, this handbook is well-attuned to educational demands, as well as providing a summary of state-of-the-art research trends and industrial requirements. It is an invaluable resource for all professionals in research and development, and engineers in practise in the field of wood science and technology.
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| 38. |
- Niemz, Peter, et al.
(författare)
-
Strength Properties of Wood and Wood-Based Materials
- 2023
-
Ingår i: Springer Handbook of Wood Science and Technology. - 2522-8706 .- 2522-8692. ; , s. 441-505
-
Bokkapitel (refereegranskat)abstract
- Knowledge of the strength of wood and wood-based materials is an important basis for the calculation and dimensioning of wooden products. This chapter describes the basics of the strength properties, test methods, important influencing parameters (e.g., moisture content, load direction, type of load, duration of load, speed of loading). Phenomenological aspects of failure on various structural levels, fracture mechanical properties as well as essential test methods such as tension, compression, shear strength, bending, torsion, and cleavage are also described. An overview is given of test specifications, strength properties of wood, and wood-based materials depending on the type of load and the direction of loading. Hardness, wear resistance, and other methods are also described. In addition to static load in short-term tests, impact resistance and fatigue as well as the influence of load duration in the static long-term test are described. In addition, selected results of the first studies to determine the properties of the molecular structure are briefly described.
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| 39. |
- Rezaei, Fatemeh, et al.
(författare)
-
Anatomical and morphological characteristics of beech wood after CO2-laser cutting
- 2022
-
Ingår i: Wood Material Science & Engineering. - : Taylor & Francis Group. - 1748-0272 .- 1748-0280. ; 17:6, s. 459-468
-
Tidskriftsartikel (refereegranskat)abstract
- This study aimed to characterize the surface quality of beech wood (Fagus sylvatica L.) cut by a CO2-laser. Boards were conditioned to a low (about 8% moisture content), 12% and a high, (about 18% moisture content). Laser cutting was performed at varying processing parameters, i.e. cutting speed, gas pressure and focal-point position. A confocal microscope was used to determine the average surface roughness perpendicular to the grain. The anatomical structures of the laser-cut surfaces were examined with scanning electron microscope. The result showed that smoother surfaces were obtained at the low moisture content when processed at a gas pressure of 21 bar. Focal-point positioning did only have an effect on the surface roughness at 12% moisture content whereas the value was substantially lower for focal-point positioned on the surface. The surfaces cut at 18% moisture content, and at a cutting speed of 3.5 m/min generated a rougher surface than cut at low moisture content and at a lower speed. Laser cutting produced a rougher surface as compared to sawn surface (circular saw). The structural integrity of the laser-cut surface was more intact when the wood was having high moisture content and processed at a high cutting speed.
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| 40. |
- Rezaei, Fatemeh, et al.
(författare)
-
The Characteristics of Glued Tensile Shear Strength Constituted of Wood Cut by CO2 Laser
- 2023
-
Ingår i: Journal of Renewable Materials. - : Tech Science Press. - 2164-6325 .- 2164-6341. ; 11:8, s. 3277-3296
-
Tidskriftsartikel (refereegranskat)abstract
- The performance of engineered wood products is highly associated with proper bonding and an efficient cutting method. This paper investigates the influence of CO2 laser cutting on the wetting properties, the modified chemical component of the laser-cut surface, and the strength and adhesive penetration near the bondline. Beechwood is cut by the laser with varying processing parameters, cutting speeds, gas pressures, and focal point positions. The laser-cut samples were divided into two groups, sanded and non-sanded samples. Polyvinyl acetate adhesive (PVAc) was used to bond the groups of laser-cut samples. After assembly with cold pressing, the tensile shear test was carried out. Numerical modelling was carried out to determine the partial elongation and shear strain of the glue line. Based on this, the shear modulus and linear elasticity of the glue line were estimated. Scanning electron microscopy was used to assess the adhesive penetration into the porosity structure of the laser-cut samples, and the depth of the heat-affected zone. The laser-cut surface was analysed by Fourier transform infrared spectroscopy. The wetting properties of the laser-cut surface were investigated by using a contact angle goniometer. The numerical model of the strain-stress curve confirmed the experimental model. The highest modulus of the linear elasticity of the glue in the numerical calculation belongs to the joint containing laser-cut samples at a gas pressure of 21 (bar). The penetration depth of PVAc adhesive into the porosity structure of the laser-cut samples was similar to that of sawn samples. The deepest heat-affected zone in the laser-cut samples was 150 µm. A PVAc drop disappeared immediately on the laser-cut surface without sanding, but gradually on the sanded surface. In contrast, the drop on the sawn surface remained with an angle of 32°–48°. The degradation of hemicellulose and lignin was proven by the lower intensity of the C=O and C-O Bonds, compared to the sawn surface.
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| 41. |
- Rezaei, Fatemeh, et al.
(författare)
-
Water uptake and permeability in sapwood and heartwood of hydro-thermally proceed Turkey oak
- 2024
-
Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 19:3, s. 803-810
-
Tidskriftsartikel (refereegranskat)abstract
- This study aimed to investigate the combined effect of steaming and heating on the equilibrium moisture content (EMC) of Turkey oak (Quercus cerris L.) wood over a nine-year period. The study also aimed to determine the impact of steaming on water absorption and water permeability, crucial for the durability of the species against environmental factors. The specimens underwent thermal modification with and without steaming, then were stored under laboratory conditions for ten years. The mass of the specimens was monitored throughout the ten-year period. To measure the water uptake capacity, the specimens were soaked in water for 120 hours. The water permeability of the specimens was assessed using a pressurised chamber. The results showed that the moisture content of thermally-modified oak was constant under laboratory conditions after nine years, further improved by steam treatment. The research also revealed that the steamed wood absorbed more water during water submersion compared to the unmodified wood. When the steaming treatment was applied, there was a significant increase in permeability in the sapwood compared to the heartwood, due to anatomical variations. Despite this, statistical noise, and material variability, alongside tylosis presence, underline the need for examining more specimens in future studies.
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| 42. |
- Sandak, Jakub, et al.
(författare)
-
Feasibility of portable NIR spectrometer for quality assurance in glue-laminated timber production
- 2021
-
Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 308
-
Tidskriftsartikel (refereegranskat)abstract
- The feasibility of a portable NIR sensor for off-line determination of diverse wood quality aspects relevant in the production of glue-laminated timber was demonstrated. The best performance was noticed for assessing wood moisture content, with a lower capacity to estimate wood density and mechanical properties. NIR spectroscopy was modestly capable of predicting surface roughness. However, the traceability of the raw resources and the automatic classification of diverse wood defects were successfully demonstrated. The developed chemometric model could predict the total delamination and detailed delamination length. Finally, recommendations regarding further system development were provided with the aim of implementation and integration of the NIR measurement into glue-laminated timber production plants.
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| 43. |
- Sandberg, Dick, et al.
(författare)
-
Advanced Engineered Wood-Material Concepts
- 2023
-
Ingår i: Springer Handbook of Wood Science and Technology. - : Springer Science and Business Media Deutschland GmbH. - 9783030813147 - 9783030813154 ; , s. 1835-1888
-
Bokkapitel (refereegranskat)abstract
- The variety of wood-based products is huge; some are produced and marketed in large volumes while others are for a very specific use and therefore also often only produced in small volumes. This chapter introduces a group of new materials, existing mainly only in laboratories or in production at pilot scale. These materials often go under the name bioinspired materials and smart wood-based materials. The second part of the chapter presents engineered wood products (EWPs) with other or additional functions than only the load-bearing capacity related not only to properties such as acoustic, heat transfer, light-weight, and extraordinary shape stability, but also to functions such as hybrid functions, improved possibility to form to a given shape, installation solutions, and esthetic and tactile performance. These materials are already on the market since many years and are in this chapter briefly introduced.
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| 44. |
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| 45. |
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| 46. |
- Teischinger, Alfred, et al.
(författare)
-
Glossary of Wood Science and Technology Terms
- 2023
-
Ingår i: Springer Handbook of Wood Science and Technology. - : Springer Science and Business Media Deutschland GmbH. - 9783030813147 - 9783030813154 ; , s. 2005-2026
-
Bokkapitel (refereegranskat)
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| 47. |
- Thybring, Emil Engelund, et al.
(författare)
-
Wood and Moisture
- 2023
-
Ingår i: Springer Handbook of Wood Science and Technology. - 9783030813147 - 9783030813154 ; , s. 355-397
-
Bokkapitel (refereegranskat)abstract
- Wood is a porous, hygroscopic material that can take up water both within cell walls (cell-wall water) and in the macrovoid structure (capillary water). Therefore, moisture transport in wood occurs through multiple pathways and phases of water, that is, both cell-wall water, liquid water, and water vapor can be transported through the material structure. The amount of water in wood is quantified by the moisture content (mass of water in relation to the dry mass), which changes with the surrounding environmental conditions (relative humidity and temperature). This relation is commonly depicted in sorption isotherms that plot the equilibrium moisture content as function of relative humidity for specific, constant temperatures. How water is taken up by wood changes over the relative humidity range. In the hygroscopic range (0% to 97–98% relative humidity), water is predominantly taken up in cell walls, whereas capillary condensation of liquid water in the macrovoid structure becomes dominant in the over-hygroscopic range (>98% relative humidity). The equilibrium illustrated in sorption isotherms for specific environmental conditions is not singular, but depends on the sorption history; this phenomenon is known as sorption hysteresis. Sorption isotherms are generally modeled using mathematical expressions that are fitted to data in the hygroscopic range. Some of these models include quantities describing the physical reality of wood-water interactions; however, these quantities rarely match up to the experimentally determined reality for wood. The same can be said of the mathematical models describing the kinetics of water uptake in wood cell walls.One of the most well-known concepts concerning water in wood is the fiber saturation point (FSP). It can be found as the threshold moisture content above which physical wood properties do not change significantly with moisture content. The FSP is, however, lower than the maximum moisture content of wood cell walls which occurs in the fully water saturated state. A change in moisture content below the FSP is accompanied by dimensional changes, that is, shrinkage and swelling, which reflect changes in the amount of water within cell walls. While this phenomenon originates at the nanoscale, it is observed on all length scales of wood. Such dimensional changes as well as other physical wood properties and fundamental wood-water interactions can be altered by chemical modification of wood. How these relations are affected depends on the chemical nature of the modification. At the end of this chapter, a broad overview is given of experimental methods for characterizing moisture in wood, including determination of moisture content, sorption isotherms, moisture state and location, and moisture transport in wood.
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| 48. |
- Vaziri, Mojgan, et al.
(författare)
-
Parameter estimation and model selection for water vapour sorption of welded bond-line of European beech and Scots pine
- 2023
-
Ingår i: Holzforschung. - : Walter De Gruyter. - 0018-3830 .- 1437-434X. ; 77:7, s. 515-526
-
Tidskriftsartikel (refereegranskat)abstract
- The single exponential kinetics (SEK) and parallel exponential kinetics (PEK) models were fitted to kinetic sorption data of welded and unwelded Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.). Furthermore, diffusion coefficients of water vapour in wood were determined using two different Fickian diffusion solutions. The objective was to identify how well these models could represent the moisture contents of the specimens and to characterize differences between the sorption behaviour of welded and unwelded wood. This knowledge can be used to enhance the moisture resistance of welded wood, develop drying schedules, and improve the quality of timbers. The PEK and SEK models provided the most precise and the second most precise fits to the sorption kinetic data, respectively. The two Fickian models are equivalent when both the infinite series are truncated at n = 10. The Fickian models also exhibited the highest discrepancy with the experimental data. Nevertheless, the Fickian models fit relatively better to the sorption data of the welded wood than to that of the unwelded wood. This behaviour may be due to the rigid and less-swelling structure of the welded bond line.
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| 49. |
- Vaziri, Mojgan, et al.
(författare)
-
Water-vapour sorption of welded bond-line of European beech and Scots pine
- 2023
-
Ingår i: Holzforschung. - : De Gruyter. - 1437-434X. ; 77:7, s. 500-514
-
Tidskriftsartikel (refereegranskat)abstract
- The wood–water interactions of welded bond-lines of European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.) were in this paper studied for the first time with dynamic vapour sorption equipment. The aim of this study was to characterize the water sorption in the welded bond-line and to define to which extent it deviates from water sorption of the unwelded wood. The objective was to provide deepened knowledge about water sorption of the welded bond-line, which could be used to improve the moisture resistance of welded wood in the future. The welded wood generally had lower equilibrium moisture contents than the unwelded wood. The welded bond-lines of beech and pine showed greater hysteresis than the unwelded wood from 0 to 55 % relative humidity. All specimens showed faster adsorption than desorption. However, the welded wood showed slower adsorption but faster desorption than unwelded wood. The time to complete half of the fractional change in moisture content (E(t) = 0.5) increased as the moisture content increased. The adsorption diffusion coefficients of beech and welded beech were higher than those of pine and welded pine up to 50 % and 40 % RH, respectively. In desorption, pine had a higher diffusion coefficient than beech in the whole range of 85–0 % RH. Analogously, welded pine had a higher diffusion coefficient than welded beech in the range of 85–5 % RH. In contrast to the desorption, the welded wood always had lower adsorption diffusion coefficients than the corresponding unwelded wood. The diffusion coefficients showed irregular patterns in some ranges of the RH. Therefore, it was hard to make a clear conclusion about the water-sorption behaviour of the specimens based on the defined diffusion coefficients.
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| 50. |
- Wang, Alice, et al.
(författare)
-
Effect of Low Temperatures on the Block Shear Strength of Norway Spruce Glulam Joints
- 2016
-
Ingår i: BioResources. - USA : North Carolina State University, Department of Wood & Paper Science. - 1930-2126. ; 11:4, s. 9638-9648
-
Tidskriftsartikel (refereegranskat)abstract
- The block shear strength of Norway spruce (Picea abies (L.) Karst.) glulam joints was tested under low temperature. Glulam samples were glued with the three of the most common outdoor structural adhesives. The cold temperatures tested were 20, −20, −30, −40, -50 and −60 °C. Within the temperature test range, the block shear strength of the glulam joints was resistant to the effect of temperature. As the temperature decreased, the joints’ block shear strength did not show any significant change. In most cases, phenol-resorcinol-formaldehyde (PRF) adhesive yielded the strongest block shear strength, while melamine-formaldehyde (MF) adhesive yielded the weakest block shear strength. Melamine-urea-formaldehyde (MUF) adhesive yielded similar results to those of MF adhesives for all temperatures tested. The block shear strengths of the glulam joints with PRF, MUF and MF adhesives were not sensitive to temperature change. The results indicated that PRF, MUF and MF adhesives are stable for outdoor structural engineered wood construction in cold climate. The results also suggest that the SS-EN 14080 (2013) standard for the block shear method may not be the proper standard for testing differences in shear strength at different temperatures. The EN 302-1 (2011) standard could be more suitable for this purpose.
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