Articles

WOOD RESEARCH Volume 64, Number 6, 2019
Zhigang Wu, Sicheng Chen, Meifen Tian, LIFEN LI, Liping Yu, Xuedong Xi, Jiankun Liang, Bengang Zhang, Hong Lei, Jun Zhang, and Taian Chen

Effects of heat-treatment on bonding performance of Betula alnoides

Heat-treatment woods of Betula alnoides were prepared by using vapor as the heat-conducting medium. Effects of heat-treatment time and heat-treatment temperature on equilibrium moisture content, density, pH value, contact angle and bonding performance of Betula alnoides were discussed in this paper. The results indicated that: (1) With the increase of heat-treatment temperature, the equilibrium moisture content, density and pH value of Betula alnoides decreased gradually. (2) With the increase of heat-treatment temperature, the contact angle of Betula alnoides increased from 70.08° to about 100°, resulting in the reduction of bonding strength gradually. Bonding strength of Betula alnoides after heat-treatment was related with the used adhesive. Bonding strength of different adhesives decreased to different extents. The bonding strength of Betula alnoides wood with polyvinyl acetate (PVAC) resin was generally higher than that of melamine-urea-formaldehyde (MUF) resin. The former were 6.35-4.56 MPa, and the latter were 5.60-3.00 MPa. (3) Heat-treatment time influenced equilibrium moisture content, density, contact angle, pH value and bonding strength of Betula alnoides less than heat-treatment temperature. (4) Heat-treatment could affect strength and surface performance of Betula alnoides greatly and the processing medium should be extended.

WOOD RESEARCH Volume 64, Number 6, 2019
Hamad A. Al-Mefarrej and Nurul Iman Suansa

Trait-based ecology using conduits comparison approach

This study conducted to quantify and compare the variation among root, stem, and branch wood of Acacia salicina and Albizia lebbeck. Results of this study revealed that the proportion of wood elements is quite similar. The wood cells decrease in length and width (diameter) in the acropetal direction. These traits indicate the principles of the hydraulic architecture of a tree as a perfect adaptation for maintaining the pressure gradient. A. lebbeck has the higher hydraulic conductivity and non-lumen fraction value. It indicates that A. lebbeck has a higher photosynthetic capacity and specific gravity. Thereafter, all of the vulnerability indexes are greater than 3, so both of examined species categorise as mesomorphy species. However, in arid circumstance, A. salicina is potentially much stronger to withstand drought-prone than A. lebbeck.

WOOD RESEARCH Volume 64, Number 6, 2019
Zhu Yuehua, Pan Biao, and Zhang Yaoli

Veneer warpage deformation measurement based on 3D laser scanning technology

In this paper, the warpage of the Taxodium hybrid ‘zhongshanshan’ veneer was measured by 3D laser scanning technology. The results showed that, the deformation of this veneer was mainly due to the warpage phenomenon along the cross striation of the wood. Air-drying shrinkage clearly enlarged the length in the direction of cross striation compared to the direction of parallel grain. The air-dried veneer would incline 7-12° along the direction of the parallel axis. When peeling the wood of the Taxodium hybrid ‘zhong shan shan’, the diameter decreased, and the warpage degree of veneer increased. The average veneer warpage degree of sapwood was 21.18%, the intermediate wood was 28.20%, and the heartwood near piths was 40.88%. High resolution 3D laser scanning technology accurately, intuitively, and rapidly obtained the deformation of the veneer.

WOOD RESEARCH Volume 64, Number 6, 2019
MARIJA TODOROVIĆ, IVAN GLIŠOVIĆ, and Boško Stevanović

Experimental investigation of cracked end-notched glulam beams repaired with GFRP bars

In this paper, an experimental research on bending behaviour of end-notched glulam beams and their bending behaviour after repairing with glass fibre reinforced polymer (GFRP) bars is presented. Altogether five glulam beams (100 x 220 x 4000 mm) made of spruce timber classified in the strength class C22 were tested. Experiment showed that originally, the beams failed in a brittle manner due to crack opening and its propagation. Cracks in the notch details were a result of excessive tensile stresses perpendicular to grain and shear stresses. Repairing the beams with GFRP bars after their failure completely restored and notably improved their load carrying capacity (average increase of 194%). Failure mechanism after repair changed from the original brittle tensile failure to more ductile failure in bending for most beams, proving the successfulness of the intervention. This study gives an insight in rehabilitation and repair possibilities of existing structures using advanced materials like GFRP bars.

WOOD RESEARCH Volume 64, Number 6, 2019
Nurdan Cetin Yerlikaya

Investigation of the differences between the glass-fiber fabric band and the edge bands in case-type furniture

This study was carried out to compare to the effects of glass-fiber fabric, which might be a new alternative edge band, to PVC and wood veneer edge bands which is used commonly in today’s furniture in wood-based materials melamine impregnated paper coated medium-density fiberboard and melamine impregnated paper coated particleboard on strength of corner joints. For this purpose, the 0.4 mm wood veneer, 0.4 mm PVC, 4 mm PVC, and fabric edge band were used as the edge bands. It was prepared 13 different configurations. The prepared test samples were subjected to the tension and compression tests. The data from the experiments was evaluated by means of multiple variance analysis. This study showed that the joint with the fabric edge band was 34% and 30% higher than 2 mm PVC band, 26% and 23% 0.4 mm PVC band, 22% and 22% 0.4 mm wood veneer band, and 16% and 23% higher than control (for tension and compression, respectively). In addition to, it is to be understood that the fabric may be used like as commercially available edge bands.

WOOD RESEARCH Volume 64, Number 6, 2019
Anouar El Moustaphaoui, Abdelkarim Chouaf, Khadija Kimakh, and M’hamed Chergui

Characterization of ceiba plywood delamination in mode i using an energetic criterion

To characterize the delamination process of Ceiba plywood, an energy approach was used. This approach considers that crack propagation is a phenomenon of energy dissipation. The fundamental parameter of this approach is the energy release rate (G). To determine this parameter in pure mode I (GI), a Double Cantilever Beam test (DCB) was deployed. The critical energy release rate in pure mode I (GIC) is determined using four approaches, namely Beam Theory, Berry compliance law, Modified Beam Theory and the Compliance Calibration method. Then, a resistance curve of Ceiba plywood was determined according to each approach. Finally, a fracture surfaces analysis was discussed to understand the nature and types of fracture.

WOOD RESEARCH Volume 64, Number 5, 2019
Widyanto Dwi Nugroho, Rini Pujiarti, and Novena Puteri Tiyasa

Wood anatomical characteristics of agarwood-producing species (Aquilaria sp.)

Aquilaria sp. is one of the tree species that produce agarwood. Agarwood is a kind of wood that has high content of fragrant resin and high economic values. Sufficient information about wood anatomical characteristic of agarwood-producing species is essential in agarwood trading, especially for identification and verification of wood. Therefore, this research aims to observe wood anatomical features of Aquilaria sp. and to observe its cell morphology. Five trees and five seedlings of Aquilaria sp. were used for the experiment. The results showed that the wood of Aquilaria sp. can be determined according to IAWA List of Hardwood for Identification with anatomical features nos. 2, 5, 10, 13, 22, 24, 29, 30, 40, 48, 49, 52, 58, 62, 66, 68, 71, 79, 92, 97, 105/104, 112, 115 and 134. Furthermore, seedling and trees of Aquilaria sp. have similar anatomical features but they have some differences on the cells morphology.

WOOD RESEARCH Volume 64, Number 5, 2019
Tiago Capobianco Morando, André Luis Christoforo, Vinicius Borges De Moura Aquino, Francisco Antonio Rocco Lahr, Greyce Bernardes De Mello Rezende, and Raul Tadeu Lobato Ferreira

Characterization of the wood species Qualea albiflora for structural purposes

The present article aimed to characterize the wood specie Qualea albiflora (Mandioqueira), in order to enable its use for structural purposes. The tests to obtain the physical and mechanical characteristics were carried out according to the Brazilian standard ABNT NBR 7190, allowing the classification of the Qualea albiflora in the strength class C60, a wood species suitable for use in heavy constructions. After the characterization, it was verified with the aid of regression models (linear, logarithmic, exponential and geometric), that it is not possible to make use of the apparent density in the estimation of the other physical and mechanical characteristics, obtaining a bad adjustment in all the cases (R² < 50.00%) and the non-representativeness of the models adopted (P-Value> 0.05).

WOOD RESEARCH Volume 64, Number 5, 2019
Wenbo Che, Zefang Xiao, and Yanjun Xie

Modification of radiata pine wood with low molecular weight modifying agents and large molecular weight styrene/acrylic acid copolymer dispersion

Our previous study revealed that treatment with aqueous styrene/acrylic acid copolymer (SA) is a cell-lumen filling process, and the treated wood exhibited negative values for cell wall bulking efficiency (BE) and anti-swelling efficiency (ASE). In this study, three low-molecular-weight agents (LMWAs), 1, 3-dimethylol-4, 5-dihydroxyethyleneurea (DM, 10%), glutaraldehyde (GA, 10%), and n-methylol acrylamide (NMA, 10%), were separately combined with SA (5, 10, 15, or 20%) and used to modify radiata pine wood at the levels of cell walls and cell lumens. The combinative treatments caused positive BE and ASE values, indicating restrained wood deformation, likely due to the diffusion and reaction of LMWAs in the wood cell walls. Infrared spectroscopy and dynamic mechanical analysis showed that LMWAs exhibit little reaction with SA, and the SA copolymer retains thermoplasticity in the wood cell lumen. The combinative treatments resulted in considerable improvement in bending modulus, bending strength, and compression strength of wood of 36, 36, and 124%, respectively, but there was little effect on impact strength. These findings confirm that LMWAs can act as cell wall modifying agents to synergistically improve wood properties, especially the dimensionally stability, when used together with SA.

WOOD RESEARCH Volume 64, Number 5, 2019
Ondřej Schönfelder, Aleš Zeidler, Vlastimil Borůvka, and Lukáš Bílek

Impact of silvicultural measures on the quality of scots pine wood Part II. Effect of site

This study deals with the variability of wood density, compression strength and the impact bending strength within the trunk of Scots pine (Pinus sylvestris L.). The impact of the site on the examined properties was also evaluated. The tree samplers come from four different sites that are representative for Scots pine growth in the Czech Republic. From the samplers the sections representing a basal part of the trunk and a middle part of the tree were cut. The most significant influence of the site was confirmed for wood density; on the other hand, the influence of the site is ambiguous in terms of the examined strength characteristics. A decrease in the wood properties with increasing trunk height was proven for all tested properties. The highest impact of the position was observed for wood density, while the results of vertical variability in mechanical properties are not always significant (compression strength: basal 47.1 MPa and middle 45.8 MPa). A close correlation between mechanical properties and wood density was also proven.

WOOD RESEARCH Volume 64, Number 5, 2019
Bailing Sun, Yubo Chai, Junliang Liu, and HOLGER MILITZ

Acetylation of plantation softwood without catalysts or solvents

This study explored acetylation of wood of Larix kaempferi (Lamb.) Carr. and Pinus sylvestris var. mongolica Litv. without catalysts or solvents. Both wood samples were impregnated with acetic anhydride and subsequently heated to 120°C for different reaction durations (0.5-8 h) in the esterification reagent. The extent of acetylation was measured by weight percent gain (WPG), which varied from 12.0% to 21.7% and 13.6% to 22.3% for both wood species. The cell wall bulking and anti-shrink efficiency (ASE) started to increase faster and then increase slower with increasing reaction time. As the WPG reached 19.2% and 17.8% or more separately, ASE of both acetylated wood were above 50% in any RH conditions. FTIR, CP/MAS 13C NMR, and XPS studies produced evidences for acetylation of both wood species. The degree of acetylation of wood cell wall polymers increased with increasing WPG, but during the process degradation of lignin and acid hydrolysis of carbohydrates occurred.

WOOD RESEARCH Volume 64, Number 5, 2019
EDINA PREKLET, LASZLO TOLVAJ, Endre A. Banadics, Tibor Alpar, and DENES VARGA

Colour modification and homogenisation of larch wood by steaming

Larch (Larix decidua L.) wood samples were steamed applying broad range of steaming time (0-20 days) at 90°C and 110°C steaming temperatures. The colour change was monitored by objective colour measurement using the CIE Lab colour system. The initial colour of earlywood and latewood within sapwood and heartwood has highly different values for larch wood. Wide range of colours was created by steaming between the initial colour and brown colour depending on the steaming time and temperature. The steaming produced excellent colour homogenisation and resulted in an increase of saturation. The redness showed the greatest homogenisation effect. The redness value difference among the tissues was seven times smaller after 9 days of steaming at 110°C than the initial redness difference. The yellowness values increased and moved toward each other during steaming. The results showed that the best visualisation effect of homogenisation can be presented on the a*-b* plane. The colour saturation of the examined tissues increased considerably and showed homogenisation effect as well. Because of the colour homogenization, it was difficult to differentiate sapwood and heartwood at the end of the steaming process at 110°C. The effective steaming time for colour homogenisation was 5 and 2 days at 90°C and 110°C, respectively.

WOOD RESEARCH Volume 64, Number 5, 2019
Ying Guan, Hui Gao, Wenqi Li, Jun Rao, and Yuqi Zhang

Preparation and characterization of antibacterial films from bamboo

The aim of this research was to prepare lignocellulose films reinforced with chitosan (CS), nano-ZnO (NZO), or nano-TiO2 (NTD) by casting method. The chemical structures of the films were characterized with FT-IR, which showed no chemical bonds formed but certain interactions among the hydrogen bonds. X-ray diffraction confirmed that the main structure of blend films was unchanged comparing to lignocellulose film. Derivative thermogravimetry (DTG) presented that the residual masses of lignocellulose/chitosan (LCCS) film, lignocellulose/TiO2 (LCTD) film, and lignocellulose/ZnO (LCZO) film were 23.43%, 19.27%, 27.68% at 700°C, respectively. Ultimate tensile strength and strain to break of all blend films were decreased with addition of CS, NZO, and NTD, respectively. LCCS film was more effective against Escherichia coli and Staphylococcus aureus than LCTD film and LCZO film. Potential antimicrobial applications in the orthopedic field and perspectives regarding future studies in this field were also considered.

WOOD RESEARCH Volume 64, Number 5, 2019
Ignacio Javier Diaz-Maroto and Sylvain Tahir

Test of wood properties in oak species (Quercus robur L., Quercus petraea (Matts) Liebl. and Quercus pyrenaica willd.) for wine aging. Part III: Porosity versus void ratio

The study on wood physical properties of Quercus robur L., Quercus petraea (Matts) Liebl., and Quercus pyrenaica Willd., to use in wine aging was also founded on the relationship between porosity and void ratio to assess its variation in the oak species under study. A total of 45 oak trees were chosen in 15 oak stands of the Lugo and Ourense provinces (Galicia, northwestern Iberian Peninsula). Altogether, were obtained forty-five fine slices of wood at 60 cm tall on the trunk, and 194 wood test specimens’ parallelepipeds of 20 × 20 × 40 mm ± 1mm. On average, oak species in Galicia have lower porosity than oaks of the French regions of Limousin and Vosges. With a width of growth ring and age similar, Quercus pyrenaica has porosity slightly lower than Q. robur and Q. petraea. Our objective is to carry out a complete description on the wood physical properties of the studied species for its possible use in the cooperage industry and wine aging. For that, the aim of this work was to estimate the porosity versus the void ratio.

WOOD RESEARCH Volume 64, Number 5, 2019
Jun Zhang, Lihong Xiong, Xiaojian Zhou, Guanben Du, Jiangkun Liang, and Xuedong Xi

Development of mimosa tannin-based adhesive cross-linked by furfuryl alcohol-formaldehyde and epoxy resins

A furfuryl alcohol-formaldehyde resin was synthesized as a crosslinker in our laboratory to develop a mimosa tannin-based adhesive with good water resistance. 13C nuclear magnetic resonance and matrix-assisted laser desorption ionization time-of-flight mass spectroscopy indicated that furfuryl alcohol reacted with formaldehyde under acidic conditions and that–CH (–OH) – groups to be the ones involved in the crosslinking of mimosa tannin-furfuryl alcoholformaldehyde adhesive (TFF). The wet shear strength of TFF-bonded plywood suggested that the cured TFF adhesive was better than mimosa tannin-furfuryl alcohol (TF) adhesive. The water resistance of TFF adhesive cross-linked with 9% epoxy resin was also higher than those of TFF and TF adhesives.

WOOD RESEARCH Volume 64, Number 5, 2019
Denisa Valachova and Iveta Skotnicova

Using the finite element method to predict heat dissipation in a timber frame building construction

This article focuses on thermal engineering assessment of light building envelope structures using Finite Element Method (FEM). The research was carried out for a particular composition of a lightweight perimeter wall in winter, for which continuous experimental measurements are also carried out. In the preparation of calculation models for numerical simulation, the marginal conditions, which were obtained by experimental measurement, were used. Thus, for simulation purposes, the construction was loaded under the same boundary conditions as the actual structure being monitored within which experimental measurements were performed. The results of the experimental measurement made it possible to compare the actual measured data with the results of the numerical simulation. The difference between calculated and experimentally determined temperatures was in the range from 0.1°C to 1.3°C. This study demonstrated, that with the help of suitable simulation programs, it is possible to predict the thermal-technical behavior of lightweight perimeter constructions.

WOOD RESEARCH Volume 64, Number 5, 2019
Han Que, Yuguo Dong, Haoquan Guo, Xinyu Lu, Xiaojun Zhu, Yimeng Zhang, and Xiaoli Gu

Pyrolytic kinetics of steam exploded lignin by TG/DTG analysis

Steam exploded lignin (SEL) thermal decomposition was investigated by thermogravimetric technique (TG/DTG) within the temperature range from room temperature to 920°C under different heating rates (10, 20, 30, 40, and 50°C. min-1). Little differences in the mass losses with heating rates were observed from TG analysis. It was established that SEL pyrolysis consisted of three main stages: water evaporation (< 200°C); devolatilization of organic volatiles (200-600°C); and char formation (> 600°C). The kinetic processing of non-isothermal TG/DTG data was performed by model-free methods proposed by Flynn-Wall-Ozawa (FWO) and Kissing-Akahira-Sunose (KAS). The average activation energies calculated from FWO and KAS methods are 74.2 kJ. mol-1 and 173.2 kJ. mol-1, respectively. Experimental results showed that values of kinetic parameters from both methods were analogous and could be successfully applied to understand the complex degradation mechanism of SEL. It is also helpful to achieve a better understanding of the devolatilization process of different type of biomass.

WOOD RESEARCH Volume 64, Number 5, 2019
Zdeněk Kopecký, Luďka Hlásková, Aleš Solař, and Petr Nesázal

Cutting forces in quasi-orthogonal CNC milling

The paper is focused on the analysis of cutting forces in milling of MDF on the CNC machine (SCM Tech 99 L, SCM Group, Italy). The measurement of the forces was realized by a three-axis piezoelectric dynamometer Kistler 9257B (Kistler Holding AG, Switzerland). The forces were examined and analysed during quasi-orthogonal milling with a single-edged blade. The resulting forces were compared to each other depending on the conventional and climb milling of the edge of the MDF at changing feed speeds from 1.5 to 4.5 m∙min-1 with steps of 0.75 m∙min-1. The experimental values of cutting forces were also used for the first assessment of the fracture toughness and shear yield strength, main parameters of computational model based on Ernst-Merchant theory and on fracture mechanics. These values were input data for the calculation of the specific cutting resistance for CNC machining. The experimental data confirmed that the cutting force increases and the specific cutting resistance decreases with the increasing chip thickness.

WOOD RESEARCH Volume 64, Number 5, 2019
Yan Yan and Fei Benhua

Axial compression properties of bamboo/wood composite column constrained with sliced bamboo veneer

The purpose of this study was to investigate the enhancement effect of composite column on axial compression. Four full-scale composite columns and one Chinese fir (Cunninghamia lanceolata) column were fabricated and tested under axial compression load to study the enhancement effect of composite column. The compressive, bending properties of bamboo (Phyllostachys edulis) rod and Chinese fir were tested respectively. The ultimate axial load capacity, midpoint lateral displacement, failure mode of composite column and Chinese fir column were also investigated. The test results indicated that the harmonious coordination between bamboo rods and Chinese fir was shown under the axial load process, and the axial compressive strength 26.21 MPa and compressive modulus of elasticity 9.46 GPa of the composite column were increased significantly meanwhile the lateral displacement at the midpoint of composite columns was reduced by 9.61 mm compared with that of Chinese fir column, and the failure patterns of two types of columns were different. The results will provide a theoretical basis for the popularization and application of bamboo and Chinese fir composite columns.

WOOD RESEARCH Volume 64, Number 5, 2019
Tatiana Vilkovská, Ivan Klement, and Igor Čunderlík

Longitudinal contraction of reaction and opposite wood during drying process

Reaction beech wood has different anatomical and also chemical characteristics than normal (opposite) wood. The difference in density is conditioned by percentage of G–layer. Fibers cells in reaction beech wood have a different cell wall structure and a different chemical composition, as well. Longitudinal contraction was noticeable in reaction (tension) samples, where it was several times higher, what could be expected considering the physical properties of reaction beech wood. Our measurements confirmed that drying time has remarkable effect on longitudinal contraction. Higher longitudinal contraction was measured in temperature 60°C and 120°C, which had almost identical drying time. The issue of variability initial moistures did not affect the drying process and samples reached approximately equal final moisture content. Reaction beech wood is a very serious problem in nowadays wood production.