Articles

WOOD RESEARCH Volume 64, Number 5, 2019
Mustafa Öncel, Hasan Vurdu, Hakan Aydoğan, Osman Emre Özkan, and Alperen Kaymakci

The tensile shear strength of outdoor type plywood produced from fir, alnus, pine and poplar wood

In this study, it is aimed to determine both the tensile-shear strengths of plywood that produced by using phenol formaldehyde resin from Uludağ fir (Abies nordmanniana subsp. bornmülleriana Mattf.), alder (Alnus glutinosa L.), scots pine (Pinus sylvestris L.) and Samsun poplar (77/51 Populus deltoides Bartr.) trees rotary cut veneers combinations of poplar-pine, poplarfir, poplar-alder and poplar wood along with the effect of wood types on adhesion quality of glue. According to standards TS 3969 EN 314-1, and TS EN 314-2 adhesion class 3, the test specimens were prepared and tested for the adhesion quality. The obtained data were analyzed statistically by using SPSS 22 statistical program. As a result, the tensile-shear strength values of poplar, pinepoplar, fir- poplar and alder-poplar plywood types were found to be as averages 1.34 N. mm-2, 1.66 N. mm-2, 2.18 N. mm-2 and 2.46 N. mm-2 respectively. Also, it was found that there was no significant difference between the alder poplar and fir-poplar plywood types about tensile-shear strength. Since these all plywood combinations are satisfied the required 1 N. mm-2 strength value according to TS EN 314-2, all plywood types in this study are of suitable quality for outdoor uses.

WOOD RESEARCH Volume 64, Number 5, 2019
Xudong Zhu, Yingying Xue, Jie Shen, and Sujun Zhang

Withdrawal strength of welded dowel joints made of birch and larch wood

This study examined the mechanics and temperature during a wood dowel welding process. The test results indicated that the welded depth 40 mm showed the highest pullout resistance. Based on the mechanics and surface morphology, welded depth 30 mm was the optimal parameter. A nonlinear relation existed between pullout resistance and welded depth. The highest temperature of six test points was studied in group of welded depth 30 mm. With the increasing of depth, the highest temperature of six test points showed the decreased trend. A linear relation was found between the highest temperature of welding interface and the depth.

WOOD RESEARCH Volume 65, Number 6, 2020
IGOR NOVÁK, ANGELA KLEINOVÁ, Ivica Janigová, MATEJ MIČUŠÍK, JÁN SEDLIAČIK, Miroslav Šlouf, PAVLO BEKHTA, JÁN MATYAŠOVSKÝ, and PETER JURKOVIČ

Properties of water steam-treated maple wood (Acer pseudoplatanus L.)

The hydrothermal treatment of maple (Acer pseudoplatanus L.) wood by steam represents the modification method with the effective heat transfer, which can improve industrially significant properties of wood, i.e. its color, hydrophobicity and subsequently dimensional stability. The maple wood was modified by steam at 125°C during 8 hours, and at pressure of 0.18 MPa. The water contact angle of steam-treated maple wood increased from 44.9° (for untreated maple wood) to 55.3° (for steam-treated maple wood), and the stability of water drop on steam-treated maple wood surface increased. FTIR spectra show an increase in C=O and glycoside bonds concentration on the surface of steam-treated maple wood, but the concentration of C-O-C groups decreased. SEM micro photos confirmed the deformation and shrinking of maple wood cells due to steam treatment. XPS measurements confirmed, that the concentration of oxygen as well as C=O and C-O-O groups on the surface of steam-treated maple wood showed a slight decrease in comparison with pristine wood sample.

WOOD RESEARCH Volume 65, Number 6, 2020
Jiulong Xie, Lin Chen, Huijuan Shao, Lu He, Yongze Jiang, Dan Lu, Hui Xiao, Yuzhu Chen, Xingyan Huang, Jianfeng Hao, Lihua Tu, Tiantian Lin, Yinlong Xiao, Gang Chen, and Jinqiu Qi

Changes in physical-mechanical properties and chemical compositions of Toona sinensis wood before and after thermal treatment

Vacuum heat treatment was used to improve the dimensional stability of Toona sinensis wood in this study, the shrinking and swelling rates, the physical-mechanical properties, and the chemical compositions before and after the thermal treatment were evaluated. The results revealed that the volume shrinkage and swelling rate for the heat-treated wood samples were decreased by 45.60% and 49.95%, respectively at 220°C for 6 h indicating that thermal treatment could obviously improve the dimensional stability of Toona sinensis wood. Thermal treatment also decreased the mechanical strength. The surface color was changed by the treatment. The chemical composition results showed the decrease in density and mechanical strength was due to the partial degradation of hemicellulose during the treatment. The results of this study that vacuum heat treatment could improve the dimensional stability by sacrificing somewhat mechanical strength, the treatment conditions mainly the temperature should be properly controlled to archive an optimized improvement in dimensional stability with minimum reduction in mechanical strength.

WOOD RESEARCH Volume 65, Number 6, 2020
ZOLTAN PASZTORY, LASZLO TOLVAJ, and DENES VARGA

Effect of water leaching on photodegraded poplar wood monitored by IR spectroscopy

Poplar (Populus x euramericana cv. pannonia) samples were irradiated using ultraviolet light emitter mercury lamp. Other series of specimens were treated with the combination of UV radiation and water leaching. The total duration of UV radiation for both series of specimens was 20 days. The total duration of water leaching was 10 days. One cycle of the combined treatment consisted of 2-day UV radiation followed by one day water leaching. The IR measurement was carried out after both UV radiation and water leaching to monitor both effects separately. Lignin degradation of water leached samples was found to be greater than that of the solely UV treated samples. The guaiacyl and the syringyl lignin showed similar degradation properties. The unconjugated carbonyl groups generated by the photodegradation proved to be the most sensitive chemical components to leaching. As a consequence of photodegradation, two absorption bands of unconjugated carbonyl groups were grown up at 1715 and 1759 cm-1 wavenumbers. The band at 1759 cm-1 was much more sensitive to water leaching than the band at 1715 cm-1. Ten days of water leaching was long enough to remove all unconjugated carbonyls generated by the photodegradation. The water was able to leach out carbonyl groups (absorbing at 1745 cm-1) originally presented in poplar wood as well.

WOOD RESEARCH Volume 65, Number 6, 2020
Jan Polednik, JOZEF MARTINKA, PETER RANTUCH, Karol Balog, Jan Skrinsky, Mateusz Wnukowski, Zdenek Lacny, and Ales Bernatik

Energy potential of the Fischer-Tropsch fuel produced from spruce wood

The Fischer-Tropsch process is a chemical reaction that enables liquid hydrocarbons to be produced from coal, natural gas, or biomass (e.g. wood). The heat of combustion and effective heat of combustion are important data for fuel used to produce energy. The usefulness of a particular fuel for society is usually evaluated on the basis of the energy returned versus the energy invested (EROI) = energy recovered/energy invested. The subject of the research was the product of a Fischer-Tropsch synthesis from a synthesis gas, which was produced through the liquefaction of sawdust from spruce wood. The synthesis took place in the reactor FIX BED at a temperature of 220 to 350°C and a pressure of 2 to 3 MPa (the hydrogen to carbon monoxide ratio was approximately 2:1). The Fischer-Tropsch fuel that was produced had a heat of combustion of 27.79 M.kg-1, effective heat of combustion 25.14 M.kg-1 and an EROI coefficient of 2.39.

WOOD RESEARCH Volume 65, Number 6, 2020
Boháček Štefan, Pažitný Andrej, Halaj Michal, Balberčák Jozef, and Kuňa Vladimír

Freeze-thaw pretreatment of poplar sapwood dust

The paper is focused on the effect of freezing and cyclic freezing-thawing pretreatment of poplar sapwood (Populus alba L.). The experimental comparison was carried out by the sawdust fraction 0.7 mm as (a) water-saturated and (b) dry. Monosaccharide yields, as well as an amount of acetic acid, were measured after 6, 24, 48, 72, and 96 hours of enzymatic hydrolysis with 15% load of the enzyme measured to total cellulose content. The influence of freezing rate on total yields was observed on equally prepared samples with different weights (31 g, 25 g, 62.5 g, 125 g, 250 g, 500 g, and 1000 g) by “cubic” tests. To increase the efficiency of pretreatment, a cyclic freezing-thawing experiment at temperatures -20°C and +25°C was performed. The results show that single freezing of grounded poplar sapwood impregnated by water or dry in its matter is not a sufficient pretreatment method, so cyclic freeze-thaw is needed to enhance the yield of monosaccharides. Analysis of cubic test showed that slower freezing process has a positive effect on enzyme accessibility.

WOOD RESEARCH Volume 65, Number 6, 2020
Roman Fojtík, Lenka Kubíncová, Viktor Dubovský, and Kateřina Kozlová

Moisture at contacts of timber-concrete element

The subject of the article is to monitor the changes of moisture on the contact surface concrete and timber part of the composite timber-concrete beam. The moisture directly affects the properties of timber and causes its volume changes and degradation processes. These effects reduce of durability and load capacity of the structures. The beam was placed at the exterior. The observed contacts of the beam are often critical on real structures, as it is difficult to repair and maintenance in the case of increasing moisture or intrusion of dirt. The experiment was used to monitor and evaluate the dependence of changing moisture in contacts depending on ambient environmental conditions.

WOOD RESEARCH Volume 65, Number 6, 2020
Kang He, Yu Chen, and Jiayu Sun

Axial mechanical properties of small-diameter round timber short columns after exposure to elevated temperatures

A total of forty-eight specimens were tested, including forty short timber columns at elevated temperatures and eight short timber columns left untreated at ambient temperature. The main parameters explored in the test include column heights (135, 180, 225 and 270 mm), elevated temperature duration (10, 20, 30, 40 and 50 min) and section form. It was found that two new failure modes were generated after the specimens exposed to the elevated temperatures: splitting failure and bottom crushing, and the ultimate bearing capacity of the specimens with bottom crushing is the lowest. The ductility of circular specimens increases with the increases of column height. When the elevated temperature duration reaches 50 min, the plasticity of the specimens basically subside. The ultimate bearing capacity of the timber columns decreases with the increase of the elevated temperature duration and the maximum reduction is about 60% percent.

WOOD RESEARCH Volume 65, Number 6, 2020
Jana Hacurová, Jakub Hacura, Vladimír Gryc, Jakub Černý, and Hanuš Vavrčík

Xylogenesis and phloemogenesis of Norway spruce in different ages stands at middle altitudinal zone

This study aimed to determine the influence of the stand age and selected weather conditions on the cambial activity, xylem and phloem formation and their development. For the analysis, microcores were taken weekly from two corresponding stands of Norway spruce (Picea abies (L.) Karst.) with various ages (35- and 106-years-old) during the growing season 2012 in the Czech Republic. Young specimens were characterised by higher cambium activity; however, more considerable variation and imbalance were found there. In old trees, delayed processes during the development of the xylem and phloem at the cell level were proved. The cambium activity started in March till mid-April, and it lasted for 22 weeks in both cases. The commencement of xylogenesis was established in the first half of May. In both investigated stands, the fully lignified ring was observed at the end of October. For the creation of most xylem cells, it was required 124 and 121 days in the young and old stands, respectively. Daily increment of 0.57 (young) and 0.49 (old) cells on average was observed during the active xylem growth. The relationship between air temperature and wood cell formation for both age groups was recorded. The precipitation influenced wood development just in the case of the young trees. Phloem formation was resistant to external influence according to the Pearson correlation coefficient.

WOOD RESEARCH Volume 65, Number 6, 2020
Mariusz Reczulski

Optimization of cutting speed and clearance angle in the disc chipper

The wood chipping system in a disc chipper Carthage-Norman was studied. The study showed many operational problems related to obtaining chips of different length in the process of wood chipping. Excessive amount of fines and pin fractions were produced in the chipper. The reason for this was the too high cutting speed of the logs and the wrong clearance angle in the chipper. The actual and optimal distribution of the cutting velocity occurring on the chipper knife was determined using the Matlab/Simulink model. In addition, optimal clearance angles in the chipper were determined using the model.

WOOD RESEARCH Volume 65, Number 6, 2020
LIN YANG, Tianqi Han, and Yudong Fu

Effect of heat treatment and wax impregnation on dimensional stability of Pterocarpus macrocarpus wood

In order to improve dimensional stability and control deformation, heat treatment (HT) and wax impregnation (WI) were conducted to large size boards (LB) of Pterocarpus macrocarpus and the tangential swelling were compared in various relative humidity (RH) conditions. The results show that the tangential swelling and shrinking of control group and treated group performed differently corresponded to various relative humidity (RH). Comparing with control group, the swelling ratio of HT combined WI group was much less, and followed by 180°C-3h HT group. The maximum swelling ratio decreased by 31% and 29% in humidity chamber and indoor conditions respectively. The swelling ratio was affected by size of samples, LB showed smaller welling ratio than small sample. Wax filled in cell cavities and presented uneven distributions after impregnation. The rate of wood hygroscopicity was reduced after HT combined WI treatment which was an effective method on improvement of wood dimensional stability.

WOOD RESEARCH Volume 65, Number 6, 2020
Selçuk Demirci, Harun Diler, Ali Kasal, and Yusuf Ziya Erdil

Bending moment resistances of L-shaped furniture frame joints under tension and compression loadings

Effect of wood species, joint techniques, and adhesive type on bending moment resistances were investigated. 480 L-shaped joint specimens were tested including 2 loadings, 4 wood species, 3 joint techniques, 2 adhesives, and 10 replications. Specimens were prepared from Scotch pine, Oriental beech, oak, and chestnut. The joint techniques were dowel, half lap and open mortise and tenon, and type of adhesives were polyvinyl acetate (PVAc) and polyurethane (PU). Bending moment resistance of the joints under compression ranged from a low of 60 Nm for Scotch pine dowel joints with PVAc to oak half lap joints a high of 281 N.m w/PVAc. Bending moment resistance of the joints loaded in tension ranged from a low of 230 N.m for scotch pine dowel joints w/PVAc and to a maximum of 917 N.m for oak half lap joints w/PVAc. Highest average moment resistance was achieved with oak half lap jointed specimens w/PVAc, under both loadings.

WOOD RESEARCH Volume 65, Number 6, 2020
Quan Li, Renyuan Liu, Xiaoqian Chen, and Hui Lin

Box-Behnken design for process parameters optimalization of bamboo-based composite panel manufacturing

High performance bamboo-based composite panel taking bamboo mats, bamboo curtains and poplar veneers are used as raw material, is manufactured from the each layers slab was crisscrossed, impregnated with phenolic resin, compressed and cured. The product was optimized by Box-Behnken model design and data analysis. The results show that the best parameter conditions were hot pressing temperature of 140°C, hot pressing time of 94 s.mm-1, and hot pressing pressure of 2.5 MPa. The model was validated according to the optimal process parameters and the static bending strength (MOR), elastic modulus (MOE), thickness expansion rate of water absorbing, adhesive strength and density are 98.95 MPa, 8.81 GPa, 4.7%, 1.25 MPa, 0.89 g.cm-3, respectively. The actual value is close to the predicted value, confirming that the obtained model can accurately predict the MOR of the product using the three factors of hot pressing as variables under different conditions.

WOOD RESEARCH Volume 65, Number 6, 2020
Rudolf Petráš, Julian Mecko, Danica Krupová, and Pažitný Andrej

Aboveground biomass basic density of hardwoods tree species

The influence of tree species on basic density of wood, bark and small-wood was investigated here. Experimental material was obtained from 73 trees of 7 tree species, namely alder (Alnus glutinosa (L.) Gaertn.), beech (Fagus sylvatica L.), birch (Betula pendula Roth.), hornbeam (Carpinus betulus L.), Black locust (Robinia pseudoacacia L.), Sessile oak (Quercus petraea (Matt.) Liebl.) and Turkey oak (Quercus cerris L.) from the territory of Slovakia. Wood and bark samples were taken from discs cut from three trunk sections and from small-wood and branch parts coming from tree crowns. The volume of green samples was measured in graduated cylinders with a precision of 1 ml; a dry matter was measured with a precision of 0.01 g. The statistically significant effect has been shown in tree species, biomass fractions and locations on the tree. The average basic density of all species varies from 440 to 650 kg.m-3 for wood, for bark it is 380-670 kg.m-3 and for small-wood outside bark it reaches 490-650 kg.m-3. Alder and Black locust tree species have the lowest and highest wood density, Black locust and Turkey oak of bark and alder and Turkey oak of small-wood.

WOOD RESEARCH Volume 65, Number 6, 2020
Chenah May and Amrani Moussa

Optimisation of acid hydrolysis in ethanol production from Ampelodesmos mauritanicus (Diss)

In this work, statistical modeling and optimization of hydrolyzate from Ampelodesmos mauritanicus (Diss) using 1.5% sulfuric acid hydrolysis was carried. A central composite design (CCD) model was used to study the influence of reaction temperature (70°C to 110°C), ratio (5% to 15%, w/v), and reaction time (60 to 180 min). Reducing sugars, pH, proteins, lignin, ash content and the elements minerals composition were determined. Optimized reducing sugars yield of 0.249 g.g-1 of dry weight was obtained for reaction time of 180 min, reaction temperature of 110°C and ratio 5% (w/v). Therefore, this study tests the production of bioethanol from pure Diss hydrolyzate by the yeast Saccharomyces cerevisiae ATCC 9763. This strain showed a consumption of 67.6% of reducing sugars available (25 g.L-1), which made it possible to obtain ethanol yield per consumed sugar 0.33 g.g-1.

WOOD RESEARCH Volume 65, Number 6, 2020
Juan Miguel Barrigón Morillas, Rubén Maderuelo-Sanz, Pedro Atanasio-Moraga, Valentín Gómez Escobar, Rosendo Vílchez-Gómez, Guillermo Rey Gozalo, and David Montes González

Short note: Virgin cork, a possible environmentally friendly by-product of the cork with acoustic properties for its use inside dwellings?

This paper is a first study to evaluate the acoustical performance of virgin cork environmentally friendly by-product of the cork that can be used inside dwellings. To obtain the acoustical performance of the virgin cork, previously, it was properly treated and flattened into slabs, and later compared to commercial rock wool. The results obtained showed that this material, specially treated and added in some building system, could show good acoustic properties with a certain broadband absorption spectrum.

WOOD RESEARCH Volume 65, Number 5, 2020
Zhongxi Zhou, Chungui Du, Huilong Yu, Xiaoling Yao, and Qiuli Huang

Promotion effect of nano-SiO2 on hygroscopicity, leaching resistance and thermal stability of bamboo strips treated by nitrogen-phosphorus-boron fire retardants

Whereas hygroscopicity an leaching resistance often have a bad influence on performance of fire-retardants, in this work, nano-SiO2 sol was added to different nitrogen-phosphorus-boron fire retardants to make four new compounds to impregnate bamboo strips, named: (1) ammonium dihydrogen phosphate + disodium octaborate tetrahydrate (AD), (2) ammonium dihydrogen phosphate + disodium octaborate tetrahydrate + nano-SiO2 sol (ADS), (3) ammonium dihydrogen phosphate + boric acid (AB), and (4) ammonium dihydrogen phosphate + boric acid + nano-SiO2 sol (ABS). After that, the hygroscopicity, leaching resistance and thermal stability were studied by scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX), thermogravimetric (TG) and fourier-transform infrared spectrometer (FTIR), and the optimal compound fire retardant is ABS. The results show that the addition of nano-SiO2 sol can not only reduce the hygroscopicity of fire-retardant bamboo strips effectively, but also improve its leaching resistance. The results also indicate that compared with non-fire-retardant bamboo strips, the thermal stability of bamboo strips treated with AB and ABS was improved significantly, and there was no significant difference between AB and ABS.

WOOD RESEARCH Volume 65, Number 5, 2020
LUKÁŠ VELEBIL and Petr Kuklík

Strength and stiffness of mechanically jointed CLT panels loaded by shear in plane

This article is focused on research into the racking strength and stiffness of mechanically jointed cross laminated timber shear walls considering the influence of fasteners between the layers of boards on the stiffness of panels. The work includes an experimental analysis and analytical model. The experimental analysis included tests of the shear wall panels, tests of the specimens to determine the stiffness at the joint of the layers and material tests. The analytical model based on the component method allows the determination of the racking strength and horizontal displacement of the shear wall in dependence on the number of layers and the number of fasteners in the joint of layers, parameters of the anchorage to the substructure and applied external load. The outputs of the numerical model and the results of the experiments agree relatively well. The largest relative displacement error is 18%.

WOOD RESEARCH Volume 65, Number 5, 2020
TAWICH PULNGERN, Kasan Chanto, Waraluk Pansuwan, and Woraparn Pattaraumpornsak

Effect of lamina thickness on flexural performance and creep behavior of douglas fir glued laminated timber beam

This research presents the effects of lamina thickness on flexural and creep performances of glulam timber. Flexural test results indicated that nonlinear load-displacement curve could be defined as both exponential and power functions. Lamina thickness was not affected to nonlinear curve, especially at initial linear relationship. Slightly different of 2.92% for nonlinear function parameters was obtained. For flexural creep test due to three levels of sustained load for 1,000 hours, only secondary creep stage behaviors without delamination were observed for all glulam timbers while average relative creep was 1.66. Effect of lamina thickness was also not found for creep performance. Finally, creep models have been developed including Bailey-Norton, adjusted Pickel, simplified Pickel, and Dorn models and found that Bailey-Norton and the adjusted Pickel models gave a good correlation with experiment and were the suitable models which could be used to predict long-term flexural creep behavior for various stress levels.