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  • 551.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Nilsson, Jonaz
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Reed canary grass as light-weight core in particleboards2013In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 9, no 4, p. 469-476Article in journal (Refereed)
    Abstract [en]

     Particle boards are an important material for furniture production. In this sector, two tasks have had priority during recent years: to reduce the weight of the panels and to reduce the formaldehyde emission. As the production methods have been more or less the same for decades, these tasks have to be tackled by reducing or replacing the raw material in the board production.

     

    In this study, the possibility of replacing wood with reed canary grass (Phalaris arundinacea L.) to obtain a light-weight particle board has been studied. The boards studied were three-layered with a core of wood/reed canary grass particles and a surface of 100 % wood particles. A protein-based adhesive was tested as an alternative to a UMF adhesive to reduce the formaldehyde emission. Different combinations of densities between 250 and 450 kg/m3 were included in the study and no additional treatments were made to the raw materials.

     

    The results showed poor mechanical and swelling properties of all the tested boards regardless of the design. The main explanation of the poor properties is the poor wetting of the reed canary grass surface by the adhesives. A pre-treatment of the reed canary grass particles with steam, lipase enzyme or alkali is suggested to increase the wettability.

  • 552.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå University of Technology, Sweden.
    Monocotyledons in Particleboard Production: Adhesives, Additives, and Surface Modification of Reed Canary Grass2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 3, p. 3919-3938Article in journal (Refereed)
    Abstract [en]

    As a supplier to the furniture industry, the particleboard industry is searching for opportunities to reduce costs, weight, and formaldehyde emissions. One such opportunity is to use monocotyledons such as straw and hemp, as well as grasses like reed canary grass. A major problem when using reed canary grass or other monocotyledons in combination with wood is the difference in their surface properties, leading to poor reactivity and wettability with adhesives such as melamine urea formaldehyde. To this end, either the surface of the particles must be modified in some way, or different adhesives must be used. The purpose of this paper is to present adhesives, surfactants, coupling agents, and pre-treatment methods that can be used in combination with monocotyledons to improve compatibility with wood. Some of the methods have been tested on reed canary grass. The results show a wide range of strength values for the joint between wood and untreated or pre-treated reed canary grass glued with different adhesives, with and without a surfactant and a coupling agent. Isocyanate-based adhesives provided relatively strong bonds, and polyvinyl acetate, acryl, and epoxy adhesives were also effective. The most effective method was pre-treatment followed by adhesives in combination with a coupling agent.

  • 553.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå University of Technology.
    Wheat protein as adhesive for wood products for interior use2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 246-252Article in journal (Refereed)
    Abstract [en]

    Protein is one of the most researched and widely used natural adhesives. Before the break through of synthetic adhesives in the wood industry, proteins were commonly used in furniture production. Today, proteins in the form of industrial by-products e.g. soy protein, blood and wheat protein are on the market, and these proteins can in general be used as a base for wood-products adhesives. Proteins are in general denatured by a change in pH, heat or organic solvents before they can be used as adhesives. In this study, a cold-dissolution of wheat protein (gluten) was tested with regard to its usability for the production of particleboards and laminated veneer products. The bonding was evaluated by testing the internal bond strength, thickness swelling, tensile strength and tensile shear strength. The results showed that the strength of the bond-line was in some cases as high as the strength of the wood material, but also that there were in some cases problems with the penetration of the adhesive into the wood and this lowered the bond-line strength considerably. The main conclusion is that cold-dissolved gluten adhesives are a good alternative to commercial synthetic adhesives for interior use, but that there are still challenges with the poor moisture resistance of the adhesive. 

  • 554.
    Trischler, Johann
    et al.
    Luleå University of Technology.
    Sandberg, Dick
    Luleå University of Technology.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Effect of temperature during vital gluten adhesive preparation and application on shear-bond strength2018In: Journal of Adhesion Science and Technology, ISSN 0169-4243, E-ISSN 1568-5616, Vol. 32, no 4, p. 448-455Article in journal (Refereed)
    Abstract [en]

    If protein-based adhesives are to become a competitive bio-based alternative to synthetic adhesives, the preparation and application methods have to be considerable improved to reduce process time and thereby improve the economy of the adhesive system. The purpose of this study was to investigate the impact of the temperature during preparation and application on the shear-bond strength of an adhesive based on vital gluten for use in wood applications. Vital gluten was used in its natural form and mixed with water of different temperatures (preparation temperature 0 °C or 20 °C), and applied on beech veneer at different temperature (application temperature –10, 20, 60 and 100 °C). Tensile shear-bond strength samples were prepared and tested according to EN 205. The results showed that an increase in veneer temperature during application of the adhesive led to a decrease in the shear-bond strength, but that the preparation temperature of the adhesive had no influence on the strength.

  • 555.
    Trischler, Johann
    et al.
    Luleå University of Technology, Sweden.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology. Luleå University of Technology, Sweden.
    Dorn, Michael
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Vital gluten for particleboard production: effect of wood-particle moisture on board properties2018In: Forest products journal, ISSN 0015-7473, Vol. 68, no 2, p. 127-131Article in journal (Refereed)
    Abstract [en]

    The growing environmental awareness is leading to an increased interest in the use of bio-based adhesives and proteins such as vital gluten. The purpose of this study was to investigate the influence of the wood-particle moisture content, water application and press time on the internal bond strength, thickness expansion and thickness swelling of particleboards glued with vital gluten. Green and dried wood particles with similar moisture contents were achieved through drying or water addition and were blended with vital gluten powder and pressed for 1 to 3 minutes. The results show that not only the pressing time and moisture content, but also the way of achieving the moisture content has a strong impact on the performance of the boards. At comparable moisture content, never-dried (green) particles with high moisture content in combination with a dry adhesive application produced boards which performed better than boards made of dry particles with water addition to simulate liquid adhesive application.

  • 556.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå University of Technology.
    Nuszkowski, Kalle
    Linnaeus University, Faculty of Arts and Humanities, Department of Design.
    The use of gluten adhesive and removable surface finishes in rebyblable furniture panels2015In: Pro Ligno, ISSN 1841-4737, E-ISSN 2069-7430, Vol. 11, no 4, p. 613-618Article in journal (Refereed)
    Abstract [en]

    A general problem in the recycling of furniture is that different materials and components are included within a single piece of furniture. Not only is the furniture built of components such as wood, leather, textiles, foams, steel and others but the wood component is also very often a composite made of wood, adhesives and functional additives such as water repellents or chemical substances as surface treatments. Sometimes these additives make cost-effective recycling of the composite wood difficult because of problems related to the separation of the components. The purpose of this study was to present an alternative product design for wood-based panels i.e. particleboards, which reduces or avoids many of the problems in the recycling of wood-based panels used in furniture. The results show that it is possible to produce wood-based panels in a way that facilitates the recycling of these panels although there are still some challenges which have to be dealt with. The concept as such seems to be promising. 

  • 557.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    An approach to estimate the productivity of various species on sites in Sweden by choosing individual climate and productivity values and the MIAMI-model with modifications.2013Conference paper (Other academic)
    Abstract [en]

    The literature contains a large variety of bioclimate, climate, biometric models for estimating the production of different species or stands under specific conditions for a defined site, or general models giving a worldwide overview of a single species. Depending on the model used, the amount of input-data varies considerable and is often related to a large investment in time and money.

    The purpose of this study was to create a model to estimate the productivity of various species of interest for biomass production using only easy available input data defining the site conditions. Further, if the site-specific input-data is the same for all species, the model allows a comparison of different species on a single site. For this approach, the MIAMI-model of Lieth et al. was used as basic model with some modifications.

    This modified model differs from recently developed models regarding the combination of species-unspecific site data and the species-specific productivity data. As the site data change with geographical location, easy handling data are profitable. The species-specific data require more extensive investigation, but once established as a database they can be used for all sites without changes. Mean annual temperature and mean annual precipitation were chosen as site-defining data and the mean annual temperature of the native distribution area of each species in combination with the highest biomass production found in the literature were chosen as the species-specific data. This combination makes this model very efficient to estimate the productivity of various species on different sites once the database is established.

    This first version of the model is restricted to sites in Sweden where changes in soil and groundwater level are relatively small. Vegetation is then mainly controlled by energy input expressed for example as temperature or irradiation. As the maximum biomass production is estimated, lower nutrient and water supplies in the soil lead primary to a decrease in biomass production, but this negative impact can be influenced by culture and treatment such as fertilising which is common in conventional agriculture. When extended to other regions with a more Mediterranean climate, for example, the impact of soil, water-storage and distribution of precipitation has to be evaluated first and if necessary included in the model formulation.

    A validation of this model with data from the literature on the one hand and data estimated by another model on the other hand showed that it seems to be possible to use the model for purposed suggested here.

  • 558.
    Trischler, Johann
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Sandberg, Dick
    Luleå Univeristy of Technology, Sweden.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Evaluating the Competition of Lignocellulose Raw Materials for their Use in Particleboard Production, Thermal Energy Recovery, and Pulp- and Papermaking2014In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, no 4, p. 6591-6613Article in journal (Refereed)
    Abstract [en]

    There is increasing competition for raw materials between particleboard production, thermal energy recovery, and pulp-and papermaking. According to different scenarios, the consumption of lignocellulosic raw materials is increasing, which means that the competition is increasing. The primary production of lignocellulosic raw material in some regions may therefore reach the limit of sustainability; i.e., the lignocellulosic raw material must be used more efficiently to reduce the risk of a shortage. The physical and chemical properties of the lignocellulosic raw material of selected species have therefore been surveyed, and the raw material properties that are important for each of the three competitors have been defined. The aim of the study is to characterise the lignocellulosic raw materials according to the three competing users and to show whether they are high or low in competition. As methods, a relative ranking of the species regarding their raw material properties and regarding the requirements of the competitors as well as cluster analysis were chosen. The results show that the most favourable raw materials are from coniferous species, while monocotyledon species show an opposite trend.

  • 559.
    Umoru, Joseph Adejo
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Characteristics assessment of aspen logs used in the production of matches2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Aspen (Populus tremula L.) accounts for about 2% of the total wood stock in Sweden. Sawmills use only a small part (about 5,000 m³fub) of round wood aspen per year. Since there are no Swedish gradings and design values for aspen, no aspen is used for structural purposes. This also applies to other hardwood trees in Sweden. Aspen is mainly used for pulp and paper with a mass consumption of 800,000 m³fub per year of which about 50% is imported. Most imported aspen is from Russia and the Baltics. The other major use of aspen is in match industries. Consumption for matches amounts to approximately 30,000 m³fub per year in Sweden.

    The aim of the research work was to increase knowledge on the wood quality of aspen used in the production of matches. Aspen (Populus tremula L.) logs were collected from two different sites in Sweden and a non-destructive tools weas used to estimate the modulus of elasticity in logs. To measure the dynamic modulus of elasticity (MOEdyn), Fakopp resonance log grader used. Other properties like density and moisture content were measure and were correlated with the MOEdyn values in order to identify the site that has a better log quality. Besides, horizontal and vertical variation of different wood properties were measured and compared within and between trees from two different sites in order to justify the variation of log quality. A total of 20 trees from Askaremåla and Vimmerby, Sweden were felled and used in this study. From each tree, 3 m long logs were sampled from each base, middle and top. After that, non-destructive evaluations were performed in those logs. Besides, 5 cm thick discs were collected in every tree height (base, middle and top) to measure horizontal and vertical variations.

    This study shows that there were differences in MOEdyn between and within trees. It was evident that trees collected from Vimmerby had a better log property than that in Askaremåla. Using non-destructive tools, it is possible to sort out quality logs for the production of Swedish matches.

  • 560.
    van Blokland, Joran
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Bending properties and strain fields around knots in thermally modified timber2018In: / [ed] Jos Creemers, Thomas Houben, Bôke Tjeerdsma, Holger Militz and Brigitte Junge, 2018Conference paper (Refereed)
    Abstract [en]

    Thirty-two (32) boards of Norway spruce with cross-sectional dimensions of 145×45 mm2 were first tested non-destructively in a four-point static bending test, were then thermally modified according to the ThermoWood® process, and were finally tested destructively in the mentioned test set up. For one of these boards, the 2D strain fields occurring due to pure bending were recorded, both before and after thermal modification, over the surface of a knotty part of the board using a non-contact optical deformation measurement system. The objectives were to get more insight into the static bending behaviour of thermally modified timber (TMT), specifically with regard to the local and global modulus of elasticity (MOE) and their respective relationship to bending strength, and the strain development around a cluster of knots. The bending strength was significantly reduced by thermal treatment, whereas the effect on the MOEs was limited. Linear regression analyses demonstrated that bending strength of TMT can be predicted by employing stiffness as indicating property. Strain field measurements showed that at the examined levels of loading the quantity and distribution of strains in a knotty area were not influenced by thermal modification. It was therefore suggested that the influence of thermal modification on global stiffness, as well as on local stiffness around knots, is limited.

  • 561.
    van Blokland, Joran
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Källander, Björn
    Swedish Wood, Sweden.
    Evaluation of non-destructive test methods to predict bending properties of thermally modified timber2018In: 2018 World Conference on Timber Engineering (WCTE), August 20-23, 2018, Seoul, Republic of Korea, World Conference on Timber Engineering (WCTE) , 2018, p. 8-Conference paper (Refereed)
    Abstract [en]

    Thermally modified wood is available through a number of manufacturers in Europe on today’s market for interior and exterior building products. Thermal modification of wood allows for improvement of dimensional stability and durability, but a considerable decrease in strength properties occurs. Despite this loss in strength, thermally modified wood shows potential to be further exploited in structures exposed to loading. For such applications, accurate prediction of its static bending behaviour is essential. This paper studies the applicability of two different non-destructive test (NDT) techniques in estimating the bending properties of thermally modified timber (TMT). The study was done on 100 Norway spruce logs. One hundred (100) boards (i.e. one from each log) were thermally modified and the mirrored 100 boards were used as controls. After modification, resonance-based and time-of-flight measurements of axial wave velocity were carried out. Subsequently, all 200 boards were bent to failure following European standard EN408. This study shows that although TMT has a lower bending strength than unmodified timber, predictions of bending strength and stiffness using the NDT techniques are possible and with sufficient accuracy. The resonance-based method gave better predictions of the bending properties of TMT in respect to time-of-flight method.

  • 562.
    van Blokland, Joran
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Prediction of bending strength of thermally modified timber using high-resolution scanning of fibre direction2019In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 77, no 3, p. 327-340Article in journal (Refereed)
    Abstract [en]

    The market share of thermally modified wood (TMW) has increased in Europe during the past few years as an environmentally friendly and durable building product. However, TMW products of today are not permitted for use in structural applications, because the reduction in strength that is caused by thermal treatment cannot be accounted for. The purpose of this paper was to investigate the bending properties of thermally modified timber (TMT) of Norway spruce, and to explore possibilities to predict the bending properties of TMT. A sample of 100 boards from a 2X-log sawing pattern of 100 logs was thermally modified according to the ThermoWood® process, while the mirror 100 boards served as an unmodified control sample. Two non-destructive methods were employed: (1) a novel method based on scanning of fibre directions to obtain the lowest edgewise bending modulus of elasticity (MOE) along a board, and (2) a conventional excitation method to determine the first axial resonance frequency used to calculate the axial dynamic MOE. Finally, the boards were bent to failure according to European standard EN 408. Despite the fact that bending strength was reduced by 42% due to thermal treatment, the type and location of failure in TMT remained related to the presence of knots. Prediction of bending strength based on local fibre direction and axial dynamic MOE, gave coefficients of determination of 0.51 for the thermally modified boards and 0.69 for the control boards, whereas axial dynamic MOE alone gave 0.46 and 0.57, respectively. These results indicate that although Norway spruce TMT has lower bending strength compared to unmodified timber, predictions of the bending strength can be made with good accuracy.

  • 563. Varshoee, Ali
    et al.
    Hosseinpourpia, Reza
    Soltani, Mojtaba
    Talaeipoor, Mohammad
    The Effect of Coupling Agent on Water Absorption Property of Natural Fiber-Cement Nanocomposites2011In: Iranian Journal of Sciences and Techniques in Natural Resources, Vol. 6, no 2, p. 127-137Article in journal (Refereed)
    Abstract [fa]

    این تحقیق به منظور بررسی تاٌثیر ماده جفت کننده بر خصوصیات میکروسکوپی و جذب آب در نانو کامپوزیتهاي ساخته شده از الیاف دورریز خمیر کاغذ سولفیت و سیمان انجام گرفته است. در این پژوهش هشت تیمار شامل تاٌثیر دو سطح ماده جفتکننده بر پایه آمینو سیلان (0 و6 درصد وزنی الیاف) و چهار سطح نانو سیلیس (0 ،5/0 ،1 و 3 درصد جایگزینی وزنی سیمان) به عنوان عوامل متغیر و میزان الیاف و آب به ترتیب در سطح 10 درصد و نسبت یک به یک وزنی سیمان ثابت، بر خصوصیت جذب آب نمونه هاي ساخته شده مورد بررسی قرار گرفت. کلیه نمونه ها مطابق با استاندارد Part: 1881 BS 5 1983-122 در سه مرحله جامد، مایع و اختلاط نهایی ساخته و مورد آزمایش قرار گرفتند. تصاویر میکروسکوپی SEM جهت بررسی خواص ریز ساختاري کامپوزیتها از نمونه ها تهیه شد. نتایج به دست آمده نشان داد که با افزایش مقدار نانو ذرات سیلیس، جذب آب در مقایسه با نمونه شاهد کاهش یافت، همچنین افزودن ماده جفت کننده موجب افزایش جذب آب گردید. از طرفی اثر متقابل نانوذرات سیلیس و ماده جفت کننده در مقایسه با نمونههاي شاهد که حاوي مقدار 10 درصد الیاف آزبست بودهاند، نشان دهنده کاهش میزان جذب آب بوده است. نمونههاي حاوي 3 درصد نانو ذرات سیلیس و 6 درصد ماده جفتکننده داراي کمترین میزان جذب آب بوده اند. همچنین تصاویر SEM حاکی از بهبود ریزساختاري نانوکامپوزیتها با افزودن ماده جفت کننده بود.

  • 564.
    Vessby, Johan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Florisson, Sara
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Habite, Tadios
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Numerical simulation of moisture driven fracture in mechanical timber connection using XFEM2017In: CompWood 2017 ECCOMAS Thematic Conference on Computational Methods in Wood Mechanics – from Material Properties to Timber Structures, Vienna, Austria, June 7-9, 2017, TuVerlag , 2017, p. 25-25Conference paper (Refereed)
    Abstract [en]

    Structural timber and glulam elements are an appealing alternative when it comes to choosing between structural elements as load bearing parts in e.g. halls, arenas and residential buildings. The wooden material is relatively strong in respect to its weight and its stiffness is sufficient enough to allow its use in a wide range of applications. However, there are also challenges associated with handling the material, one of which is the dimensional instability associated with moisture changes. The effect of climate variations on moisture induced deformations, stresses and failure in timber structures has already been addressed by several researchers, see e.g. [1] and [2]. A numerical model developed in the finite element package Abaqus is proposed herein to simulate crack propagation caused by variation in climate. In mechanical connections moisture induced strains in combination with boundary conditions that introduces constraints can lead to crack development and in turn weakening of wooden structures. Previous application of fracture mechanics typically focused on crack development caused by pure mechanical loading, see e.g. [3] for methods summarized and typical applications. Within the scope of the current work a numerical model is presented to simulate moisture driven crack growth within the beam/column dowel group connection shown in Figure 1. The model consists of two dimensional hygro-mechanical plane stress and XFEM analysis coupled to a nonlinear transient moisture flow analysis. A visualization of the considered problem is given in Figure 1. This figure shows a beam to column connection, which is exposed to natural climate variation (a). A schematic description of the problem is shown in Figure 1 (b). Figure 1 (c) shows simulated moisture content gradient and significant cracked beam because of the deformation constraints imposed by the dowels. The transient non-linear moisture flow was modelled using Fick’s law of orthotropic diffusion, using different diffusion coefficient in the two main directions, the length direction of the beam (assumed parallel to the fibers) and the direction perpendicular to that. The moisture transport in parallel direction was taken to be dominant. The shrinkage coefficients experience different values in perpendicular and parallel direction, αperp and αpar, respectively. For the fracture model, the critical energy release rate, GIC, is set to 300 J/m2, the strength in the perpendicular direction, ft,perp, to 2.5 MPa and the stiffness perpendicular and parallel to the length directions of the fibres are Eperp= 500 MPa and Epar= 10 000 MPa respectively.

  • 565. Voulgaridis, E
    et al.
    Karastergiou, S
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Passialis, C
    Kortsalioudakis, N
    Koutsianitis, D
    Foti, D
    Voulgaridou, E
    Effect of laser drilling on the mechanical properties and impregnation of fir and spruce wood2015Conference paper (Refereed)
  • 566. Voulgaridis, E
    et al.
    Passialis, C
    Adamopoulos, Stergios
    Wood quality characterization in black locust of different origin2000In: 3rd Workshop of COST Action E10: Wood properties for Industrial Use “Measuring of wood properties, grades and qualities in the conversion chains and global wood optimization”, 19-21 June, Espoo, Finland, 2000, p. 147-162Conference paper (Other academic)
  • 567. Voulgaridis, Elias
    et al.
    Adamopoulos, Stergios
    Karastergiou, Sotirios
    Passialis, Costas
    Koutsianitis, Dimitrios
    Kortsalioudakis, Nathanail
    Petrakis, Panagiotis
    Moustaizis, Stavros
    Effects of laser drilling on mechanical properties and impregnability of fir and spruce wood2015In: Innovation in Woodworking Industry and Engineering Design, ISSN 2367-6663, no 1, p. 14-22Article in journal (Refereed)
    Abstract [en]

    Fir (Abies borisii regis) and spruce (Picea excelsa) wood specimens, 2 × 2 cm in cross section and 34 cm long, were prepared with true radial and tangential surfaces. All lateral surfaces of the specimens were drilled by laser to a depth of 4 mm (1/5 of specimen thickness) with two drilling patterns (distance between holes 1 × 1 cm and 1 × 2 cm). ). After drilling, the mechanical strength of wood (MOE, MOR, axial compression, toughness) was determined and compared with non-drilled controls. MOE was not affected by the laser drilling, MOR was significantly increased, axial compression was increased and toughness was decreased but not significantly. The overall results imply that strength properties do not decline by the laser drilling. Furthermore, wood specimens were impregnated with rape oil and CCB preservatives by applying vacuum (0.6 mmHg) and pressure (1,5 bars) for 15 minutes and 30 minutes, respectively. The results showed that both drilling patterns improved the retention and penetration of preservatives in fir and spruce wood specimens and, thus, are encouraging for further evaluating the drilling effects on the liquid permeability of these refractory to impregnation species. This effect was more pronounced in fir than in spruce wood.

  • 568.
    Voulgaridis, Elias
    et al.
    Aristotle University of Thessaloniki, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Foti, Dafni
    Aristotle University of Thessaloniki, Greece.
    Voulgaridou, Eleni
    Aristotle University of Thessaloniki, Greece.
    Properties of gypsum bonded solid bricks manufactured with recovered wood and rubber2013In: Annual Meeting Prosylva Europe and 16th Panhellenic Forestry Conference , 6-9 October 2013, Thessaloniki, Greece, 2013Conference paper (Refereed)
    Abstract [en]

    Utilization of recovered wood fromparticleboard production residues and rubber from waste tires in the manufacture of solid bricks was investigated, using gypsum as bonding media. The manufacturing parameters were: small and large rubber and wood particles, different gypsum/wood/rubber ratios for each fraction (small, large), and different gypsum/water ratios. Cylindrical samples, produced by pouring the mixtures into cylindrical molds, were used for testing compressive strength, thermal conductivity and sound absorption according to standard methods.Compressive strength of all gypsum bonded wood and rubber samples was much lower than the controls, e.g. pure gypsum samples. It was found that the wood samplesand the larger fractions (both rubber and wood) were superior in strength than the rubber samples and small fractions, respectively. A maximum proportion25% of wood or rubber as well the use of reclaimed fibrous materials in the manufacture of samples would probably ensure an acceptable compressive strength. No differences were found among the wood/rubber typesfor thermal conductivity, while particle size and proportion of the materials had no effect. Samples with small wood and rubber particles at the lower proportion (25%) were similar in their sound absorption behaviour.

  • 569.
    Voulgaridis, Elias
    et al.
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Larissa, Greece.
    ΑΝΑΓΝΩΡΙΣΗ ΞΥΛΙΝΩΝ ΕΥΡΗΜΑΤΩΝ ΑΠΟ TON ΤΑΦΙΚΟ ΤΥΜΒΟ ΤΗΣ ΜΙΚΡΗΣ ΔΟΞΙΠΑΡΑΣ-ΖΩΝΗΣ: Identification of the wooden finds from the Tumulus of Mikri Doxipara-Zoni2010In: ΑΛΟΓΑ ΚΑΙ ΑΜΑΞΕΣ ΣΤΟΝ ΑΡΧΑΙΟ ΚΟΣΜΟ: ΠΡΑΚΤΙΚΑ ΕΠΙΣΤΗΜΟΝΙΚΗΣ ΣΥΝΑΝΤΗΣΗΣ ΟΡΕΣΤΙΑΔΑ 30 ΣΕΠΤΕΜΒΡΙΟΥ 2006: Horses and Wagons in the Ancient World: Proceedings of One Day Scientific Meeting, Orestiada-Greece September 30, 2006 / [ed] Diamantis Triantafyllos, Domna Terzopoulou, Νομαρχία Έβρου , 2010, p. 151-173Conference paper (Other academic)
  • 570.
    Voulgaridis, Elias
    et al.
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Foti, Dafni
    Aristotle University, Greece.
    Voulgaridou, Eleni
    Aristotle University, Greece.
    ΠΑΡΑΓΩΓΗ ΚΑΙ ΙΔΙΟΤΗΤΕΣ ΠΕΙΡΑΜΑΤΙΚΩΝ ΠΛΙΝΘΩΝ ΕΣΩΤΕΡΙΚΗΣ ΤΟΙΧΟΠΟΙΙΑΣ ΑΠΟ ΓΥΨΟ ΚΑΙ ΑΝΑΚΥΚΛΟΥΜΕΝΑ ΥΛΙΚΑ ΞΥΛΟΥ ΚΑΙ ΕΛΑΣΤΙΚΩΝ ΟΧΗΜΑΤΩΝ: [ Production and properties of experimental bricks for interior walls from gypsum and recycled materials of wood and rubber ]2017In: ΠΡΑȀΤǿȀΑ : 18ου Πανελλήνιου Δασολογικού Συνεδρίου : “Η Ελληνική Δασοπονία μπροστά σε σημαντικές προκλήσεις: αειφορική διαχείριση δασών, δασικοί χάρτες, περιβαλλοντικές τεχνολογίες – δικτύωση και προστασία φυσικού περιβάλλοντος”: & International Workshop : “Information Technology, Sustainable Development, Scientific Network & Nature Protection” : 8-11 Οκτωβρίου 2017, ΕΔΕΣΣΑ ΠΕȁȁΑΣ, Περιοχή Βαρόσι, Hellenic Forestry Society , 2017, p. 315-323Conference paper (Refereed)
    Abstract [en]

    Τhe manufacturing and testing of gypsum bonded solid bricks with wood chips from particleboard production residues and rubber and textile fibers from waste tires was investigated. The recovered rubber and wood materials were mixed in gypsum/water solutions for the fabrication of standard solid bricks with six holes by using appropriate molds. After drying, the compressive strength, the thermal conductivity, the air-flow resistance, the sound absorption coefficient and the emissions of volatile organic compounds (VOC) of the bricks were determined. The compressive strength of solid bricks was much greater than that required in interior walls. The bricks showed a better thermal insulation than both the extruded and pressed house bricks but lower than the insulating bricks. Emissions of volatile organic compounds of bricks were at acceptable levels according to regulations for construction products. The sound absorption coefficient of the solid bricks was 0,72 for the frequency of 1 kHz and decreased with increasing frequency. In addition, information on the raw materials and production cost are given.

  • 571. Voulgaridis, Elias
    et al.
    Passialis, Costas
    Adamopoulos, Stergios
    Triantafyllos, D
    Identification of wood and charcoal specimens from the ancient tomb of Mikri Doxipara-Zoni, Evros Prefecture2008In: National Archaeological Conference, March 13-15, Thessaloniki, Greece, 2008Conference paper (Other academic)
  • 572.
    Voulgaridis, Elias
    et al.
    Aristotle University of Thessaloniki, Greece.
    Passialis, Costas
    Aristotle University of Thessaloniki, Greece.
    Karastergiou, Sotirios
    Technological Educational Institute of Thessaly, Greece.
    Adamopoulos, Stergios
    Technological Educational Institute of Thessaly, Greece.
    Kakaras, Ioannis
    Technological Educational Institute of Thessaly, Greece.
    Foti, Dafni
    Aristotle University of Thessaloniki, Greece.
    Koutsianitis, Dimitrios
    Aristotle University of Thessaloniki, Greece.
    Voulgaridou, Eleni
    Aristotle University of Thessaloniki, Greece.
    Effect of laser drilling on impregnability of fir (Abies borisii regis) and spruce (Picea excelsa) wood2014In: Wood Structure, Properties and Quality – 2014: 5th RCCWS International Symposium, Moscow State University Press, 2014, p. 51-56Conference paper (Refereed)
    Abstract [en]

    Fir and spruce wood specimens, 2×2 cm in cross section and 34 cm long, were pre-pared with true radial and tangential surfaces. All lateral surfaces of the wood specimens were drilled by laser beams to a depth of 0,4 cm (1/5 of specimen thickness) with two drilling patterns (distance between holes 1×1 cm and 1×2 cm) in order to improve the wood permea-bility of these refractory to impregnation species. After drilling and assessing the drilling ef-fect on mechanical properties of wood, wood specimens, 10 cm long, were impregnated with oil and CCB preservatives by using vacuum (0,6 mmHg) and pressure (1,5 bar) for 15 minutes and 30 minutes, respectively. The effects of the two laser drilling patterns on impreg-nability of fir and spruce wood specimens were measured and assessed. The results showed that both drilling patterns created by laser beams on all lateral surfaces of fir and spruce wood specimens at 0,4 mm depth improved the retention and penetration of preservatives in fir and spruce wood specimens. This effect was more pronounced in fir than in spruce. Between the two drilling patterns, the pattern with distances between holes 1×1 cm was more effective than that with distances 1×2 cm, in both species tested.

  • 573.
    Voulgaridis, Elias
    et al.
    Aristotle Univ Thessaloniki, Greece.
    Passialis, Costas
    Aristotle Univ Thessaloniki, Greece.
    Negri, Martino
    Ivalsa Cnr, Trees & Timber Inst, Italy.
    Adamopoulos, Stergios
    Technol Educ Inst Larissa, Greece.
    Shear bond strength of black locust wood glued with three adhesive systems2012In: Wood research, ISSN 1336-4561, Vol. 57, no 3, p. 489-496Article in journal (Refereed)
    Abstract [en]

    Black locust wood was bonded with three commercial adhesives (PVAc, PU, epoxy) and tested for its shear bond strength against process (treatments I and II) and surface parameters (radial, tangential, roughness). For treatment I (applied pressure 8 bar, press time 1.5 h, curing time 24 h), the mean shear bondstrength was found to be 6.95 N.mm(-2), 5.54 N.mm(-2) and 10.53 N.mm(-2) corresponding to the three adhesives tested, respectively. Increase in press and curing time in treatment II (press time 3 h, curing time 7 days) significantly improved the gluing performance of adhesives, 9.58 N.mm(-2) for PVAc, 13.32 N.mm(-2) for PU and 15.03 N.mm(-2) for epoxy. Surface of gluing (radial, tangential) did not affect the shear bond strength significantly. Failure within wood was found to be up to 40 % for treatment I (PVAc, epoxy) and up to 85 % for treatment II (epoxy). Positive linear regressions were calculated between shearbond strength and wood failure only for PU and epoxy adhesives. Shear bond strength was not related to surface roughness for any adhesive.

  • 574.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Almkvist, Gunnar
    Swedish University of Agricultural Sciences .
    Bader, Thomas K.
    Linnaeus University, Faculty of Technology, Department of Building Technology. Vienna University of Technology, Austria.
    Bjurhager, Ingela
    Uppsala University.
    Rautkari, Lauri
    Aalto University, Finland.
    Gamstedt, E. Kristofer
    Uppsala University.
    The influence of chemical degradation and polyethylene glycol on moisture-dependent cell wall properties of archeological wooden objects: a case study of the Vasa shipwreck2016In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 50, no 6, p. 1103-1123Article in journal (Refereed)
    Abstract [en]

    Cell wall measures allow for direct assessment of wood modification without the adverse effect of varying density and microstructure. In this study, cell wall properties of recent and archeological oak wood from the Vasa shipwreck were investigated for cell wall stiffness, hardness and creep with respect to effects of chemical degradation, impregnation with a preservation agent, namely polyethylene glycol, and moisture. For this purpose, nanoindentation tests were performed at varying relative humidity, leading to different moisture contents in the wood samples. Concurrently, microstructural and chemical characterization of the mate- rial was conducted. Impregnated and untreated recent oak wood showed a softening effect of both moisture and preservation agent at the wood cell wall level. On the contrary, increased stiffness was found for non-impregnated Vasa oak, which can be explained by aging-related modifications in cell wall components. These effects were counteracted by the softening effect of polyethylene glycol in the impregnated Vasa material, where a lower overall stiffness was measured. The reverse effect of the preservation agent and moisture, namely increased indentation creep of the cell wall material, was revealed. The loss of acetyl groups in the hemicelluloses explained the decreased hygroscopicity of the Vasa oak. In the impregnated Vasa oak, this effect seemed to be partly counteracted by the presence of low-molecular polyethylene glycol contributing to higher hygroscopicity of the cell wall. Thus, the higher overall sorptive capacity of the impregnated Vasa material, with respect to the non-impregnated material, was detected, which has resulted in a sorptive behavior similar to that of recent oak wood. The proposed approach requires only small amounts of material, making it especially suitable for application to precious historical wooden artifacts. 

  • 575. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Cell Wall Properties of Archaelogical Oak Wood from the Vasa Shipwreck: A Nanoindentation Study2015In: 32nd Danubia-Adria-Symposium (DAS 32), Zilina, Slovakia, 2015, p. 162-163Conference paper (Other academic)
  • 576.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Auty, David
    Université Laval, Canada.
    de Borst, Karin
    University of Glasgow, UK.
    Control Parameters for Within-Tree Variability of Wood Stiffness at Different Length Scales: Multiscale Modeling and Experimental Investigations2012In: COST Action FP0802 - Experimental and Computational Micro-Characterization Techniques in Wood Mechanics, Edinburgh, UK, 2012, p. 72-73Conference paper (Other academic)
  • 577.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Auty, David
    University of Aberdeen, UK.
    de Borst, Karin
    University of Glasgow, UK.
    Key parameters controlling stiffness variability within trees: a multiscale experimental–numerical approach2012In: Trees, ISSN 0931-1890, E-ISSN 1432-2285, Vol. 27, no 1, p. 321-336Article in journal (Refereed)
    Abstract [en]

    Microstructural properties of wood vary considerably within a tree. Knowledge of these properties and a better understanding of their relationship to the macroscopic mechanical performance of wood are crucial to optimize the yield and economic value of forest stocks. This holds particularly for the end-use requirements in engineering applications. In this study the microstructure–stiffness relationships of Scots pine are examined with a focus on the effects of the microstructural variability on the elastic properties of wood at different length scales. For this purpose, we have augmented microstructural data acquired using SilviScan-3™ (namely wood density, cell dimensions, earlywood and latewood proportion, microfibril angle) with local measurements of these quantities and of the chemical composition derived from wide-angle X-ray scattering, light microscopy, and thermogravimetric analysis, respectively. The stiffness properties were determined by means of ultrasonic tests at the clear wood scale and by means of nanoindentation at the cell wall scale. In addition, micro-mechanical modeling was applied to assess the causal relations between structural and mechanical properties and to complement the experimental investigations. Typical variability profiles of microstructural and mechanical properties are shown from pith to bark, across a single growth ring and from earlywood to latewood. The clear increase of the longitudinal stiffness as well as the rather constant transverse stiffness from pith to bark could be explained by the variation in microfibril angle and wood density over the entire radial distance. The dependence of local cell wall stiffness on the local microfibril angle was also demonstrated. However, the local properties did not necessarily follow the trends observed at the macroscopic scale and exhibited only a weak relationship with the macroscopic mechanical properties. While the relationship between silvicultural practice and wood microstructure remains to be modeled using statistical techniques, the influence of microstructural properties on the macroscopic mechanical behavior of wood can now be described by a physical model. The knowledge gained by these investigations and the availability of a new micromechanical model, which allows transferring these findings to non-tested material, will be valuable for wood quality assessment and optimization in timber engineering.

  • 578. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Mechanical Properties of Scots Pine (Pinus sylvestris L.) Cell Walls After Fungal Degradation: Multiscale Micromechanical Modeling and Experimental Validation2012Conference paper (Other academic)
  • 579.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Micromechanical Modelling of Degration Processes in Wood2014In: 11th. World Congress on Computational Mechanics (WCCM XI), 5th. European Conference on Computational Mechanics (ECCM V), 6th. European Conference on Computational Fluid Dynamics (ECFD VI), July 20 - 25, 2014, Barcelona, Spain, Barcelona, Spain, 2014Conference paper (Other academic)
  • 580. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Nanoindentation of Wood Cell Walls: Effects of Different Sample Preparation Methods2013Conference paper (Other academic)
  • 581.
    Wagner, Leopold
    et al.
    University of Technology, Austira.
    Bader, Thomas K.
    University of Technology, Austira.
    de Borst, Karin
    University of Glasgow, UK.
    Nanoindentation of wood cell walls: effects of sample preparation and indentation protocol2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 1, p. 94-102Article in journal (Refereed)
    Abstract [en]

    Nanoindentation has become a valuable tool in wood science. It enables to examine the mechanical properties of the wood cell walls, which are polymeric, multi-layered structures with typical thicknesses of a few micrometers. Despite the intensive use of the method for the characterization of wood cell walls, it is not entirely clear yet how the measurement results may be affected by the way the sample is prepared and the indentation is carried out. This manuscript contributes to clarify these issues, by presenting indentation data for a variety of sample preparation techniques and indentation protocols, and by critically evaluating the observed differences of the obtained indentation moduli and hardnesses. Investigations covered the effect of different embedding materials, including testing of non-embedded cell walls, and of repeated exposure to high temperatures during harsh drying before the indentation test. Moreover, potential edge effects were studied when the indentation size approaches the width of the individual cell wall layers. Using different embedding materials as well as testing non-embedded cell walls did not lead to significant changes in the measured properties. Due to damage during the sample preparation, non-embedded cell walls tend to show substantially higher experimental scatter. Repeated drying prior to embedding had no significant effect on the resulting moduli and hardnesses. Finally, it was found that reasonable mechanical properties can be extracted from the cell corner middle lamella (CCML), even when the size of the indent approaches the diameter of the CCML.

  • 582. Wagner, Leopold
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    Eberhardsteiner, Josef
    Nanoindentation to Study Within-Tree Variability of Wood Cell Wall Stiffness2012In: 29th DANUBIA-ADRIA SYMPOSIUM on Advances in Experimental Mechanics, September 26-29, Belgrade, Serbia, Belgrade, Serbia, 2012, p. 8-9Conference paper (Other academic)
  • 583.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    Cell wall properties of softwood deteriorated by fungi: combined chemical analyses, FT-IR spectroscopy, nanoindentation and micromechanical modelling2013In: Proceedings IRG Annual Meeting, Stockholm: The International Research Group on Wood Protection , 2013Conference paper (Other academic)
    Abstract [en]

    Mechanical properties of wood are determined by its inherent hierarchical microstructure, starting at the nanometer scale, where the elementary components cellulose, hemicelluloses, and lignin build up the wood cell wall material. Fungi cause degradation and decomposition of these components and, thus, alter the mechanical properties of wood. The aim of this study is to gain new insight into these relationships at the cell wall level, particularly at early stages of degradation, characterized by a mass loss of less than 10 %. Early detection of deterioration is essential during monitoring of timber structures as it may help avoiding subsequent larger scale damages. This contribution presents results of an ambitious experimental programme covering the determination of earlywood/latewood specific compositional data with consistent microstructural and micromechanical properties. Scots pine (Pinus sylvestris L.) sapwood was studied in reference condition and after degradation by brown rot (Gloeophyllum trabeum) and white rot (Trametes versicolor), respectively. Ultrastructural and compositional data were acquired by means of FT-IR spectroscopy and wet chemical analyses. Micro-structural features, such as the microfibril angle, were determined by X-ray diffraction. Mechanical properties of sound and degraded wood cell walls were determined using nanoindentation, yielding the (anisotropic) indentation modulus of the S2 cell wall layer and the cell corner middle lamella of Scots pine tracheids. Aiming at the identification of relationships between ultrastructural and micromechanical characteristics, two different approaches were followed. On the one hand, multivariate data analysis was applied. On the other hand, a multiscale micromechanical model was used to derive causal relationships between structure and (mechanical) function for deteriorated wood. Anisotropic indentation theory allows calculating model predictions for the indentation modulus of the S2 cell wall layer based on measured chemical compositions resulting from the degradation process. Comparing these predictions with the experimental results enables to test hypotheses on possible scenarios of wood cell wall deterioration during fungal attack. Identified relationships between ultrastructural, microstructural, and micromechanical characteristics will be discussed as well as the potential of micromechanical modelling in the analysis of fungal degradation strategies and their effect on the mechanical behaviour. 

  • 584.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Consequences of Microbial Decay on Mechanical Properties of Wood Cell Walls2015Conference paper (Other academic)
    Abstract [en]

    As a natural material, wood is susceptible to degradation processes, preserving equilibrium between buildup and breakdown of biomass. Microorganisms, such as fungi or bacteria, play a major role in the degradation processes in wood. Their activity depends on the environmental conditions: in ambient conditions fungal degradation is dominant while in waterlogged conditions mainly bacterial degradation occurs. Wood exhibits a hierarchical organization. Thus, mechanical properties of a piece of solid wood depend on its inherent heterogeneous microstructure. Starting from the annual rings, individual wood cells and their cell wall layers can be identified as hierarchical levels. The so-called S2 cell wall layer and the middle lamella between individual wood cells dominate the macroscopic behaviour of wood. Thus the properties of these two layers are of particular interest. Their mechanical properties can be assessed by means of nanoindentation. During nanoindentation, a probe is pushed into a flat sample surface and from the subsequent unloading behavior, material properties, such as the indentation modulus and the indentation hardness, can be determined. In contrast to findings at the macroscopic scale, no stiffness losses were detected in degraded cell wall layers. Even slightly increased stiffness of the S2 layer and the middle lamella were measured in material degraded either by fungi or bacteria. Concurrently, microstructural and chemical analyses of the degraded material were conducted. Both multivariate data analysis as well as micromechanical modeling enables establishing structure-function relationships also for degraded wood cell walls.

  • 585.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Fungal degradation of softwood cell walls: Enhanced insight through micromechanical modeling2014In: International Biodeterioration & Biodegradation, ISSN 0964-8305, E-ISSN 1879-0208, Vol. 93, p. 223-234Article in journal (Refereed)
    Abstract [en]

    Abstract Fungal degradation is among the greatest hazards for standing trees as well as timber constructions. Herein we aim at gaining more detailed insight into the degradation strategies of wood destroying fungi and the consequences on the mechanical performance of wood. At the macroscale, the occurring losses of mass and of mass density mask effects of altered chemical composition and microstructure. Thus, it is necessary to step down the hierarchical organization of wood to the cell wall scale in order to resolve these changes and their mechanical impact. We present a multiscale micromechanical model which is used to estimate the stiffnesses of the S2 cell wall layer and the compound middle lamella of fungal degraded wood. Data from a detailed chemical, microstructural and micromechanical characterization of white rot and brown rot degraded Scots pine sapwood is analyzed. Comparing predicted cell wall stiffnesses with measured ones confirms the suitability of the approach. The model enables to establish structure–stiffness relationships for fungal degraded wood cell walls and to test hypotheses on yet unknown effects of fungal decay. The latter include the evolution of porosity, modifications of the cell wall polymers resulting in changes of their stiffnesses, as well as increasing cell wall crystallinity. The model predictions in general showed good agreement with the predictions not considering pores in the cell wall. However, this finding does not rule out the formation of porosity. Other degradation related effects like modifications of the cell wall polymers as well as increased crystallinity have the potential to account for stiffness decreases upon the formation of pores.

  • 586.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Nanoindentation and Micromechanical Modeling to Explore the Mechanical Performance of Deteriorated Softwood2011In: COST Action FP0802 - Experimental and Computational Micro-Characterization Techniques in Wood Mechanics, Helsinki, Finland, 2011, p. 61-62Conference paper (Other academic)
  • 587.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Ters, Thomas
    Vienna University of Technology, Austria.
    Fackler, Karin
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    A combined view on composition, molecular structure, and micromechanics of fungal degraded softwood2015In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 69, no 4, p. 471-482Article in journal (Refereed)
    Abstract [en]

    Fungal decay alters the composition, microstructure, and mechanical properties of wood cell walls. To understand better the structure-function relationships during fungal decay, selected annual rings of fungal deteriorated Scots pine sapwood were analyzed in terms of their composition, microstructure, and micromechanical properties. The datasets were acquired separately for earlywood and latewood concerning the S2 cell wall layer and the cell corner middle lamella (CCML) and analyzed by means of principal component analysis and partial least squares regression analysis. Links between cell wall stiffness and hardness and the composition and microstructure could be established. Increased mechanical properties in the CCML, as obtained by nanoindentation, were correlated to the degradation of pectins. In the S2 layer, the altered data were related to the degradation of hemicelluloses and lignin modification during fungal decay.

  • 588.
    Wagner, Leopold
    et al.
    Vienna University of Technology, Austria.
    Bos, Clemence
    Vienna University of Technology, Austria ; Institute for applied materials, Germany.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    de Borst, Karin
    University of Glasgow, UK.
    Effect of Water on the Mechanical Properties of Wood Cell Walls: Results of a Nanoindentation Study2015In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 10, no 3Article in journal (Refereed)
    Abstract [en]

    The paper presents a nanoindentation study on five different wood species in which the elastic and creep properties of the S2 cell wall layer and the middle lamella were determined. Measurements were carried out at relative humidities (RH) ranging from 10 to 80% as well as underwater. Indentation moduli were found to decrease by about a third in the S2 layer and by about half in the middle lamella between RH of 10 and 80%. Hardness dropped by 50 to 60% in this humidity range in both the S2 layer and the middle lamella. Creep parameters were almost constant up to a relative humidity of 40%, but they increased considerably at higher RH. The most pronounced change of reduced moduli and creep properties occurred between 60 and 80% RH, which is consistent with the expected softening of hemicellulose and amorphous parts of cellulose in this humidity region. Immersion into water resulted in a further decrease of the reduced moduli to about 20 to 30% of their values at 10% RH and to only about 10 to 20% for the hardness. This can be explained by additional softening of the less ordered regions of cellulose.

  • 589. Wagner, Leopold
    et al.
    Bos, Clemence
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Moisture-Dependent Mechanical Properties of Softwood and Hardwood Cell walls: A Nanoindentation Study2014In: 16th International Conference on Experimental Mechanics (ICEM16), July 7-11, 2014, Cambridge, Cambridge, UK, 2014Conference paper (Other academic)
    Abstract [en]

    Wood is a hygroscopic material. Increasing moisture decreases the macroscopic mechanical properties of wood. Investigations of the mechanical behaviour of the solid wood substance at the cell wall scale may contribute to an enhanced insight into moisture-mechanics relationships. Wood cells walls are composed of several different layers, of which the S2 layer and the middle lamella (ML) are mechanically most important. Their mechanical properties can be assessed by nanoindentation. Wood of two hardwood species and three softwood species is investigated. Mechanical properties of the S2 layer as well as of the ML are determined at different relative humidity (RH), i.e. at different wood moisture contents (MC).

  • 590. Wagner, Leopold
    et al.
    Bos, Clemence
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Eberhardsteiner, Josef
    Moisture-Dependent Mechanical Properties of Softwood and Hardwood Cell Walls: A Nanoindentation Study2014In: 31st Danubia-Adria Symposium on Advances in Experimental Mechanics, September 24-27, 2014, Kempten, 2014, p. 151-152Conference paper (Other academic)
  • 591. Wagner, Leopold
    et al.
    Fackler, Karin
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Ters, Thomas
    de Borst, Karin
    Fungal Degradation of Scots Pine (Pinus sylvestris L.) Wood: Micromechanical and Microstructural Characterization at the Cell Wall Level2012In: 7th International Plant Biomechanics Conference, August 20-24, 2012, Clermont-Ferrand, France, Clermont-Ferrand, France, 2012Conference paper (Other academic)
  • 592.
    Walford, Brian
    et al.
    Wood Quality and Solid Wood Products Forest Research.
    Ormarsson, Sigurdur
    Prediction of Twist in Poles that Contain Spiral Grain2003In: IAWPS2003 International Conference on Forest Products, 2003Conference paper (Refereed)
  • 593.
    Wang, X. A.
    et al.
    Luleå University of Technology.
    Hagman, O.
    Luleå University of Technology.
    Sundqvist, B.
    SP Technical Research Institute of Sweden ; SP Sustainable Built Environment.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wan, H.
    Mississippi State University, USA.
    Niemz, P.
    ETH, Switzerland.
    Impact of cold temperatures on the shear strength of Norway spruce & scots pine joints with different glues2016In: WCTE 2016 - World Conference on Timber Engineering, Vienna University of Technology , 2016Conference paper (Refereed)
    Abstract [en]

    As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, the impact of cold temperatures on the shear strength of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) joints (150 mm x 20 mm x 10 mm) bonded with seven commercially available adhesives was studied. The cold temperatures investigated were: 20, -20, -30, -40, -50, and -60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints for both species. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. But different adhesives responded differently with Norway spruce and Scots pine.

  • 594.
    Wang, Xiaodong Alice
    et al.
    Luleå University of Technology.
    Björnberg, Jonathan
    Luleå University of Technology.
    Hagman, Olle
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    Swiss Federal Institute of Technology in Zurich, Switzerland.
    Effect of Low Temperatures on the Block Shear Strength of Norway Spruce Glulam Joints2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 4, p. 9638-9648Article in journal (Refereed)
    Abstract [en]

    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.

  • 595.
    Wang, Xiaodong (Alice)
    et al.
    Luleå University of Technology, Sweden.
    Hagman, Olle
    Luleå University of Technology, Sweden.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden, Sweden.
    Ormarsson, Sigurdur
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    ETH Zurich, Switzerland.
    Shear Strength of Scots Pine Wood and Glued Joints in a Cold Climate2016In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 11, no 1, p. 944-956Article in journal (Refereed)
    Abstract [en]

    The impact of cold temperatures on the shear strength of Scots pine (Pinus sylvestris) joints glued with seven commercially available adhesives was studied in this work. The cold temperatures investigated were: 20, -20, -30, -40, and -50 degrees C. Generally, within the temperature test range, the shear strength of Scots pine solid wood and wood joints were more resistant to the effect of temperature than those of Norway spruce. As the temperature decreased, only some of the joints' shear strength significantly decreased. In most cases, PUR adhesive yielded the strongest shear strength and MUF adhesive yielded the weakest shear strength. MF adhesive responded to temperature changes in a similar manner to that of PUR and PVAc adhesives. The shear strengths of wood joints with PRF and EPI adhesives were more sensitive to temperature change. For dynamic tests of shear strength, the values for 12-h and 6-day tests under temperature cycles (-20 and 0 degrees C) were compared. The values for 6-day tests were lower than those for 12-h tests. Therefore, the duration of the samples subjected to the same temperature had a significant impact on shear strength. Our results indicate that PUR adhesive is the most stable; whereas the stability of MUF and PRF adhesives decreased significantly.

  • 596.
    Wang, Xiaodong
    et al.
    Luleå University of Technology.
    Hagman, Olle
    Luleå University of Technology.
    Sundqvist, Bror
    SP Technical Research Institute of Sweden.
    Ormarsson, Sigurdur
    Technical University of Denmark, Denmark.
    Wan, Hui
    Mississippi State University, USA.
    Niemz, Peter
    ETH Zurich.
    Impact of cold temperatures on the shear strength of Norway spruce joints glued with different adhesives2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 2, p. 225-233Article in journal (Refereed)
    Abstract [en]

    As wood construction increasingly uses engineered wood products worldwide, concerns arise about the integrity of the wood and adhesives used. Bondline strength is a crucial issue for engineered wood applications, especially in cold climates. In this study, Norway spruce (Picea abies) joints (150 mm × 20 mm × 10 mm) were bonded with seven commercially available adhesives: polyurethane (PUR), polyvinyl acetate (PVAc), emulsion-polymer-isocyanate (EPI), melamine-formaldehyde (MF), phenol-resorcinol-formaldehyde (PRF), melamine-urea-formaldehyde1 (MUF1), and melamine-urea-formaldehyde2 (MUF2). Each adhesive was tested at six temperatures: 20, −20, −30, −40, −50 and −60 °C. Generally, within the temperature test range, temperature changes significantly affected the shear strength of solid wood and wood joints. As the temperature decreased, the shear strength decreased. PUR adhesive in most cases resulted in the strongest shear strength and MUF adhesive resulted in the weakest. MF and PRF adhesives responded to temperature changes in a similar manner to that of the PUR adhesive. The shear strengths of wood joints with PVAc and EPI adhesives were more sensitive to temperature change. At low temperatures, the variability of shear strengths increased with all adhesives. Percent wood failures of joints bonded with different adhesives in most cases were not sensitive to temperature changes.

  • 597. Wikete, Christoph
    et al.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Jäger, Andreas
    Hofstetter, Karin
    Eberhardsteiner, Josef
    Mechanical Properties and Microstructural Characteristics of Hardwood2010In: 27th Danubia-Adria Symposium on Advances in Experimental Mechanics : September 22nd - 25th, 2010, Wrocław University of Technology, Wrocław, Poland / [ed] Romuald Be̜dziński, Wroclaw, Poland: Wrocław University of Technology , 2010, p. 237-238Conference paper (Other academic)
  • 598.
    Wiklund, Martin
    et al.
    KTH.
    Sandberg, Dick
    KTH, .
    The Concept of Value Activation - Wood Properties at Different Annual Ring Orientation in Pine (Pinus Silvestris L).1998In: Timber and Wood Composites for the Next Century / [ed] Song-Yung Wang and Min-Chyuan Yeh, 1998Conference paper (Refereed)
    Abstract [en]

    An integrated R&D program called "Value Activation" has been carried out for the past eight years at the Royal Institute of Technology, Div. of Wood Technology and Processing (KTH-Trä). The concept of Value Activation is focused on the basic understanding of wood, and the fact that there are properties that are not fully exploited in conventional wood manufacturing systems to date. The strategy is to activate these inherent properties by a better understanding of the fundamental behaviour of wood, combined with new applied process technology and the development of the required manufacturing systems.

    The Value Activation program has so far shown that there are great possibilities of utilizing the properties of wood in a better way than our conventional wood production concept can achieve. New wood products with desirable properties can be developed. Most of these products are expected to give a greater added value to the wood. The R&D program will continue with the further development of improved products and also with the development of cost-efficient production systems for implementing the ideas from our R&D in profitable production units.

    Within the Value Activation program the following properties, which were judged to be the most important ones for future wood products were chosen:

    • Aesthetic and tactile factors
    • Controlled moisture movements
    • Accuracy in size and geometry
    • No checks and splits
    • Strength and hardness

    These properties are all strongly influenced by the annual ring orientation in the cross section of the sawn timber. This paper describes the influence of the annual ring orientation on these properties and how they can be improved by using a new sawing pattern.

  • 599.
    Wimmer, Rupert
    et al.
    Univ Bodenkultur Wien BOKU.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Effects of Reaction Wood on the Performance of Wood and Wood-Based Products2014In: The Biology of Reaction Wood / [ed] Gardiner, B., Barnett, J., Saranpää, P., Gril, J., Springer, 2014, 1, p. 225-248Chapter in book (Refereed)
    Abstract [en]

    Compression wood in softwoods and tension wood in hardwoods have properties, which adversely affect its usefulness for wood products. This chapter shows that reaction wood can be associated with many unsuitable wood properties. The results vary due to the fact that definitions about occurrence and severity of reaction wood are scarcely documented. A few properties seem to be even benefitting from the presence of reaction wood: the higher smoothness of compression wood surfaces, better shear strength of compression wood, higher toughness and impact resistance when tension wood is present, lower water uptake and swelling in fibreboards containing compression wood, and higher durability against fungi of compression wood. However, these are outweighed by disadvantages, which is the reason why reaction wood has a bad reputation in industry. The problem with reaction wood is that it is in most cases mixed with normal wood, which leads to non-uniform and more variable properties. This may lead to non-uniform swelling and shrinking, causing distortions, with additional problems of reduced strength and unfavourable surface properties. Wood-based materials such as particle boards or fibreboards are generally less prone to problems associated with reaction wood than solid wood products. With knowledge-based production methods the utilization of different wood types, including reaction wood, might be feasible.

  • 600.
    Xiao, Zefang
    et al.
    Georg-August-University of Gottingen, Germany.
    Xie, Yanjun
    Northeast Forestry University, Kina.
    Adamopoulos, Stergios
    Georg-August-University of Gottingen, Germany.
    Mai, Carsten
    Georg-August-University of Gottingen, Germany.
    Effects of chemical modification with glutaraldehyde on the weathering performance of Scots pine sapwood2012In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 46, no 4, p. 749-767Article in journal (Refereed)
    Abstract [en]

    Scots pine sapwood was treated with glutaraldehyde (GA) in aqueous solution using magnesium chloride as a catalyst in order to evaluate the durability towards weathering. Infrared spectroscopy suggested that GA treatment increased the photo-stability of lignin during artificial weathering of micro-veneers in a QUV over 168 h; photo-protection increased with increasing GA concentration. In comparison with the unmodified controls, GA-modified pine micro-veneer strips exhibited a lower tensile strength loss measured in a zero-span mode in the course of weathering. During 18 months of outdoor exposure, GA-modified pine wood boards exhibited a lower moisture content and water uptake than the unmodified ones. GA treatment also clearly restricted the penetration of blue stain fungi into deeper layers of wood. On the macroscopic scale, the surface of the GA-modified boards was significantly smoother due to less erosion, cracking and minor peeling of tracheids. Scanning electron microscopy further revealed that individual tracheids were detached from the cell compound and then washed away from the unmodified wood surface, whereas tracheids on surfaces of GA-modified wood remained in the tissue compound but displayed many axial and transversal cracks.

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