WOOD RESEARCH Volume 61, Number 1, 2016
Bodo Caspar Kielmann, Holger Militz, and Carsten Mai

The effect of combined melamine-resin-colouring agent modification on water related properties of beech wood

Beech wood (Fagus sylvatica L.) was modified with aqueous solutions of methylated N-methylol melamine (NMM) and a metal-complex dye and the water related properties were determined. Wood blocks, treated to the highest weight percent gain (WPG), attained approximately 5 % cell wall bulking and 30 % anti-swelling efficiency (ASE) after ten cycles of water saturation and drying. The metal-complex dye was stably fixed in the resin matrix and was hardly washed out. The equilibrium moisture content of the modified samples related to the dry mass of untreated beech wood (EMCR) was not considerably reduced compared to the EMC of the control. The maximum swelling of the modified samples as a result of vapour sorption was only reduced above 65 % relative humidity compared to the control. Capillary water uptake of wood was significantly reduced by the resin modification. The results indicate the potential of the combined modification to improve the water related properties of wood.

WOOD RESEARCH Volume 61, Number 1, 2016
Katarzyna Pentoś, Deta Łuczycka, and Tobiasz Wysoczański

The use of complex impedance as a parameter for wood differentiation

Electrical and dielectric wood properties are used in many applications. Wood parameters such as resistance, conductivity, complex impedance can be used e.g. for determination fungal decay, moisture content and density or for defects detection. In this work, the complex impedance of seven wood species was measured for frequency range 10 Hz – 1 MHz. The specimens were cut from sapwood and heartwood and measurements were conducted with parallel and perpendicular orientation of the electrical field with respect to the visible grain. The impedance of various wood types differs significantly for frequencies below 2 kHz. Therefore, for wood samples classification, the complex impedance values measured in frequency 1.1 kHz were used. Three different classification methods were used for clustering. Results show that the impedance can be a useful parameter for wood differentiation and membership of each group depends on number of clusters.

WOOD RESEARCH Volume 61, Number 1, 2016
Limam Amel, Zerizer Abdellatif, and Quenard Daniel

Determination of acoustic parameters of bio-based materials distended for building: Application case to Aleppo pine wood cork and their composites

In this work, we are interested to incorporating acoustic comfort in buildings by using bio-based materials. More specifically, this work aims to determinate experimentally the sound absorption coefficient (α) and the sound reduction index (R) in three different samples. The first sample consists of Aleppo pine wood (Pinus halepensis) with two different configurations (solid wood and laminated timber wood). The second sample consists of a black agglomerated cork (suber) with two different thicknesses. The third sample consists of sandwich assemblies obtained by superimposing two wooden layers (solid or laminated timber wood) bonded with an inter layer cork. In this experimentation, we have used Kundt tube to determine sound absorption coefficient and AcouSYS V2.0 software to predict the sound reduction index. The obtained results showed that the first parameter (α) is influenced by the thickness of material. The second parameter (R) of symmetrical and asymmetrical sandwich assemblies of solid laminated timber wood with an interlayer of black agglomerated cork even shows good performances.

WOOD RESEARCH Volume 61, Number 1, 2016
Linda Makovická Osvaldová, Stanislava Gašpercová, Patrik Mitrenga, and Anton Osvald

The influence of density of test specimens on the quality assessment of retarding effects of fire retardants

Test methods evaluating wood flame retardant efficiency are comprised of a parameter which is often considered to be an evaluation criterion and its calculation includes the weight of the test specimen or takes into account the change of its weight during the test. In this case, the overall result may be affected not only by the weight of the test specimens, but also by their density. Our aim is to observe the influence of density while evaluating the efficiency of wood flame retardants.

WOOD RESEARCH Volume 61, Number 1, 2016
Hilmi Toker, Ergun Baysal, Turkay Turkoglu, Saban Kart, Faruk Sen, and Huseyin Peker

Surface characteristics of Oriental beech and Scots pine woods heat-treated above 200°C

Heat-treated of Oriental beech (Fagus orientalis L.) and Scots pine (Pinus sylvestris L.) woods were carried out by hot air in an oven for 1, 3, and 5 hours at 205, 220, and 235°C. After heat treatments, some surface properties such as color and gloss changes of both wood specimens were evaluated. Our results showed that heat treatment caused decrease in gloss values of Oriental beech and Scots pine wood specimens. Higher treatment temperature and duration resulted in higher gloss loss of wood specimens after heat treatments. Heat-treated wood became darker tonality, especially; it became more darkening after 3 and 5 hours heat treatments. Generally according to our results, Δa* and Δb* decreased after heat treatments. Oriental beech wood tended to become less reddish than Scots pine after heat treatments. Δa*, Δb* and ΔE* of heat-treated Oriental beech and Scots pine decreased with increasing treatment temperature and duration.

WOOD RESEARCH Volume 61, Number 1, 2016
Majid Kiaei, Hamid Reza Naji, Hazandy Abdul-Hamid, and Mohammad Farsi

Radial variation of fiber dimensions, annual ring width, and wood density from natural and plantation trees of Alder (Alnus glutinosa) wood

The aim of this research was to determine radial variations of some wood properties from natural and plantation trees of Alnus glutinosa. Oven-dried wood density (WD), fiber cell features, and annual ring width (ARW) were determined in radial positions of stem at breast height of tree. The results showed that the cultivation methods had significant influence on the fiber length (FL), fiber diameter (FD) and ARW. The effect of interaction between radial position and cultivation methods on anatomical features was not significant, except for cell wall thickeness (CWT). Fiber cell features and WD increased with distance from pith for both cultivations trees. The ARW decreased with increasing the cambial age in both cultivation methods. The average of FL and ARW in plantation trees was higher than those in natural trees. Widest FD was found in natural forest. There were significant relationships between ARW-WD and WD-FD for natural forest and between ARW-WD, ARW-CWT and WD-FL for plantation forest. About 67 % of WD variation in natural and plantation trees were related to FD and ARW, respectively. Due to high FL and ARW, wood from planted trees could be suitable for paper production than wood from natural trees.

WOOD RESEARCH Volume 61, Number 1, 2016
Albert Russ, Mária Fišerová, Michal Letko, and Elena Opálená

Effect of steam explosion temperature on wheat straw enzymatic hydrolysis

Wheat straw is an abundant and readily available lignocellulosic material potentially suitable for the second generation bioethanol production. Steam explosion was investigated as a suitable pretreatment method. Effect of steam explosion temperature on wheat straw enzymatic hydrolysis was investigated. Optimum steam explosion temperature at around 200°C was determined based on concentration of monosaccharides in hydrolysates, conversion of cellulose and xylan and yield of monosaccharides from wheat straw. This corresponds to creating conditions resulting in sufficient damage to the lignocellulose structure which leads to higher enzyme accessibility. Lower temperature does not enable sufficient enzyme accessibility while excessively high temperature results in significant breakdown of monosaccharides and lignin and creation of inhibitors. The amount of originated inhibitors was also determined for each studied steam explosion temperature.

WOOD RESEARCH Volume 61, Number 1, 2016
Birol Üner, Mehmet Akgül, M.Onurhan Gücüş, and Serkan Demir

The effect of oxalic acid pretreatment on alkali pulping process

The objective of this study was to determine prehydrolysis process on kraft and soda pulping process. Optimum cooking conditions were determined by different alkali concentration and cooking period. Oxalicacid was used to hydrolyzechip before cooking. Prehydrolysis proces increased the yield and viscosity of pulp. Incontrast, mechanical properties of paper were not changed significantly. Optical properties were decreased due to lignin content.

WOOD RESEARCH Volume 61, Number 1, 2016
Haiyan Yang, Zhengjun Shi, Liming Xiong, Kun Wang, and Run-Cang Sun

Ionic liquids assisted alkaline fractionation enhanced triploid poplar bioconversion for bioethanol production

In this case, [Amim]Cl, [Bmim]Cl and [Emim]Ac were used to dissolve ball-milled triploid poplar, and the cellulose-rich preparations were subsequently recovered via incubation in 5 % NaOH aqueous solution and filtration. After the stepwise pretreatments, the carbohydrate content in the cellulosic residues increased to 73.3, 73.6 and 79.0 %, respectively, from 66.1 % in that with sole alkali fractionation. In comparison, the treatment with [Emim]Ac incurred transformation of cellulose I to II, which was favorable to enhance the alkaline fractionation for lignin extraction and disruption of biomass intact structure. After reconstitution, the digestibility of the three cellulosic preparations was all improved, yielding 1.3-fold higher fermentable sugars than that without IL pretreatment (67.2 %). These results indicated that the stepwise pretreatment with ionic liquid and alkali was effective for disrupting the intact structure of plant cell wall, and improving the productivity of bioethanol from lignocellulose biomass.

WOOD RESEARCH Volume 61, Number 1, 2016
Ergün Güntekin, Tuğba Yilmaz Aydin, and Peter Niemz

Some orthotropic elastic properties of Fagus orientalis as influenced by moisture content

The aim of this study was to investigate the influence of moisture content on some orthotropic elastic properties of Oriental beech (Fagus orientalis). The elastic properties investigated include EL, ER, ET, νLR, νLT, νRL, νRT, νTL and νTR under compression. Compression strength in all orthotropic directions was also studied. Specimens were cut from sapwood of beech logs and sorted into four matched MC groups. Clear wood samples were conditioned at 20°C and 50, 65, 85, 95 % RH and subjected to compression tests. A digital image correlation technique was used to capture the strains during testing. Young modulus, Poisson ratios, and compression strength were calculated and compared for all orthotropic directions. Results indicated that Young modulus and compression strength of the samples tested were strongly affected by moisture content. Poisson rations seem to less sensitive to the MC changes.

WOOD RESEARCH Volume 61, Number 1, 2016
Sha Sha Song and Benhua Fei

The psychological effects of different types of housing environment under different weather conditions

In order to improve the quality of human being’s living and working environment, different types of wood structure building, ecological architecture and green building are advocated due to their lots of advantages. This study compared three types of houses in different weather conditions on people’s psychological and physiological indexes. The results showed that the temperature, electrocardiograph, heart rate and respiratory rate of people in different types of housing environment are different. Most of the physiological indexes in structural glued laminated and wood structure environment were better than those in steel and concrete structure environment, and most of the physiological indexes in structural glued laminated environment were better than those in the timber structure environment. It means that subjects of the test are easy to had comfortable and relaxed feeling in the glued laminated and timber structure environment. This provided theoretical support for the use of the product by scientific and efficient ways, and guidance for design and application of the construction of the wooden structure environment in the future.

WOOD RESEARCH Volume 61, Number 1, 2016
Francesco Negro, Corrado Cremonini, Roberto Zanuttini, and Marco Fringuellino

Development of framed poplar plywood for acoustic improvement

Acoustic is a fundamental topic in large environments often characterized by poor sound quality such as dining rooms or open space offices. The paper reports the development and testing of sound absorbing poplar plywood for the acoustic improvement of such spaces; prototypes were designed aiming at acoustic performance and lightness, as an alternative to other acoustic woodbased panels currently on the market. The experimentation ranged from the testing of small specimens to the validation of prototypes in end-use dimensions. Developed panels achieved high sound absorption peaks in the low frequency range (sound absorption coefficient α = 0.80 at frequency of 315 Hz). Prototypes installed on the walls of a dining room reduced significantly its reverberation time (RT60); room users, investigated by a questionnaire, perceived a high acoustic improvement. On the whole the designed products resulted effective sound absorbers; their industrialization can represent a valuable niche for poplar plywood producers.

WOOD RESEARCH Volume 61, Number 1, 2016
Jan Pošta, Petr Ptáček, Robert Jára, Monika Terebesyová, Petr Kuklík, and Jakub Dolejš

Correlations and differences between methods for non-destructive evaluation of timber elements

The aim of this paper is to compare the results of evaluation of mechanical properties of timber by visual assessment, two grading machines, three devices for measuring in-situ and destructive tests. The most important result is the comparison of static and dynamic modulus of elasticity of timber, and further comparison of strength classes obtained by different measuring methods.

WOOD RESEARCH Volume 61, Number 1, 2016
Ivan Glišović, Boško Stevanović, Marija Todorović, and Tijana Stevanović

Glulam beams externally reinforced with CFRP plates

An experimental program was undertaken to investigate the effectiveness of carbon fiber reinforced polymer (CFRP) plates as flexural reinforcement of glued laminated timber (glulam) beams. Beams with and without reinforcement were tested up to failure in a four-point bending configuration. A comparison between the flexural behaviuor of control unreinforced beams with reinforced beams is shown and discussed. The results demonstrated increase in strength, stiffness and ductility when CFRP plate is bonded at tension side of cross section. Research findings indicated that the use of proposed reinforcing solution improves utilization of the compression characteristics of timber. Based on the experimental observations, a theoretical model is developed to predict the ultimate moment capacity and bending stiffness of CFRP-reinforced glulam beams.

WOOD RESEARCH Volume 61, Number 1, 2016
Regita Bendikiene and Edmundas Pupelis

Application of surfaced cutters for machining of wood-based materials

The present paper describes results of recent research aimed to make high wear resistance cutter for machining of wood-based materials. Medium density fibreboard (MDF) was chosen for wear test because it is quite abrasive, ease blunts edges of cutters, is inhomogeneous material: contains glue and different mineral particles. It is well known that cutting particleboard results wearing out of cutter faster than machining of natural wood. Because of this, experimental cutters made by surfacing using submerged arc welding (SAW) technique and prepared material powder mixture spread on the surface of cutters blank, were introduced in this research. Suggested material powder mixture ensured obtaining the high alloyed and wear resistant surface layer on the cutting edge of cutter. The wear performance of experimental and commercial cutter was accomplished on the typical industrial thickness planer with a face milling cutterhead using MDF as workpiece. Wear of experimental cutters showed very similar performance as commercial cutter made of high speed steel HSS18.

WOOD RESEARCH Volume 61, Number 1, 2016
Milan Gaff, Monika Sarvašová Kvietková, Miroslav Gašparík, and Martin Slávik

Dependence of roughness change and crack formation on parameters of wood surface embossing

This paper deals with roughness change and crack formation after surface embossing of aspen wood. Embossing was carried out with three various shapes of embossing wedges (convex, concave and with 45° angle). The embossing was realized with two temperatures, 20 and 160°C. The surface roughness before and after embossing was evaluated on the basis of the arithmetical mean deviation of the roughness profile, Ra. Surface quality measurements were carried out in perpendicular (transversal) and parallel (longitudinal) direction in relation to wood fibers. Embossment area quality was evaluated by the mean of portion of cracks in embossment. This evaluation was based on digital image of embossed area and subsequently calculation of portion of cracks area in relation to total evaluated area. Elevated temperature has a positive effect on the quality of the surface, because of roughness decrease. However, the increase in temperature causes a growth in the proportion of cracks on the embossed surface.