WOOD RESEARCH Volume 69, Number 3, 2024
SHAOXIANG CAI, YULIANG GUO, and YANJUN LI

EFFECT OF PHENOL FORMALDEHYDE RESIN IMPREGNATION ON NANODYNAMIC VISCOELASTICITY OF PINUS MASSONIANA LAMB IN WET STATE

We evaluated the effects of phenol formaldehyde (PF) resin modification on Masson pine (Pinus massoniana Lamb.) wood cell wall in wet states. The penetration degree of PF resin into wood cell was determined using confocal laser scanning microscopy (CLSM). The micromechanical properties of PF-modified wood cell walls in wet state were analyzed by quasi-static nanoindentation and dynamic modulus mapping techniques. Results showed that the PF resin significantly affected the static viscoelasticity and nanodynamic viscoelasticity of wood cell walls in oven-dried and wet states. The cell-wall mechanics increased at a PF resin concentration due to the increased bulking effects, such as decreased crystallinity of cellulose. Furthermore, the microfibrillar angle (MFA) of cell walls was lower than that of the control wood cell wall. The cell-wall mechanics of PF resin-modified sample decreased small than control sample in wet states

WOOD RESEARCH Volume 69, Number 3, 2024
PATRIK MITRENGA, LINDA MAKOVICKÁ OSVALDOVÁ, MIROSLAVA VANDLÍČKOVÁ, and MILAN KONÁRIK

OPTIMIZING THE AMOUNT OF FLAME RETARDANT USED FOR SPRUCE WOOD

The study investigated the effect of the amount of selected retardant coatings produced and used in the Slovak Republic on the fire resistance of spruce wood samples. Experiments were conducted for two different types of flame retardants: intumescent flame retardant (IFR) and inorganic salt-based flame retardant (IS). Based on different amounts of coating applied to spruce wood samples, the important parameters as mass loss, mass loss rate and fire spread rate were determined. The experiment consisted of applying a flame source to the samples at an angle of 45° and monitoring the mass of the samples during the experiment. The findings show that when IFR is used, the protection effect of the wooden samples increases linearly with the amount of coating. However, for the samples on which an IS flame retardant was applied, a higher amount of coating had no effect on increasing the fire resistance of the wood. In this case, the average total mass loss was the same regardless of the amount of coating, yet a significant retardation effect was observed compared to the untreated samples. Samples treated with IFR showed a lower total mass loss and also a significantly lower maximum mass loss rate compared to the samples with applied IS flame retardant

WOOD RESEARCH Volume 69, Number 3, 2024
MERYEM KACMAZ UNVER, MUSTAFA ALTUNOK, and SEKIP SADIYE YASAR

THE INVESTIGATION OF NATURAL AGING BEHAVIOR OF SOME WOOD SPECIES MODIFIED WITH NATURAL PRESERVATIVES

This study evaluates the effects of 12-month outdoor weathering on Scots pine (Pinus sylvestris L.) and sessile oak (Quercus petraea L.) woods modified with tannins. Wood specimens were divided into four groups: Group A (control, natural aging (NA)), Group B (NA + 100% walnut tannin (WT)), Group C1 (NA + 50% WT and 50% pine tannin), and Group C2 (NA + 50% WT and 50% oak tannin). Group A showed density decreases of 4.3% for Scots pine and 4.7% for sessile oak, while Group B samples exhibited density increases of 2.6% and 1.6%, respectively. Group A specimens had hardness losses of 36.3% for Scots pine and 28.7% for Sessile oak, compared to reduced losses of 8.8% and 11.2% in Group B. Bending strength and modulus of elasticity also decreased significantly in Group A but were minimally affected in Group B. These results indicate that tannin treatments, particularly walnut tannin, improve wood durability and mechanical performance, offering an eco-friendly alternative to conventional treatments

WOOD RESEARCH Volume 69, Number 3, 2024
CHENYANG LI, YATING CAI, XINJIE ZHOU, RUOGU XU, HAN YU, LILI YU, HUI LI, XIAO WANG, and SHU-GUANG LI

PREPARATION PROCESS AND INTERFACE MODIFICATION ON THE MECHANICAL PROPERTIES OF BAMBOO FIBER/POLYPROPYLENE CARBONATE COMPOSITES

In this study, bamboo fiber (BF) and polypropylene carbonate (PPC) were used to prepare BF/PPC composite materials. The single factor test combined with orthogonal experiment was used to investigate the effects of different hot pressing process conditions (hot pressing temperature, hot pressing pressure and hot pressing time) on the mechanical properties of BF/PPC composites. Based on the hot pressing process results, the filler nano-calcium carbonate (Nano-CaCO3), γ-aminopropyl triethoxysilane (KH550) and maleic anhydride (MAH) were added respectively to the composites to improve the interface between BF and PPC in order to increase the mechanical properties of the composites. The results showed that the reasonable preparation conditions of BF/PPC composites with the best mechanical properties were set at 170°C, under 1.9 MPa for 10 min. Compared with PPC samples, the tensile modulus, bending modulus and impact strength of BF/PPC composites could be increased to 102%, 38.69% and 65.13%, respectively. The optimal interface modification treatments have been proved that nano-CaCO3 with 10% content could increase the tensile modulus and impact strength to 70.53% and 65.84%, while the best result for the bending modulus of BF/PPC composites was modified with MAH with 2.5% content, which could increase to 28.46%

WOOD RESEARCH Volume 69, Number 3, 2024
HİKMET YAZICI

IMPACT OF HOLLOW CORE DIAMETER AND BFRP WRAPPING ON AXIAL COMPRESSIVE STATIC PERFORMANCE OF TIMBER

This paper presents an experimental study on the axial compressive static performance of the cylindrical timber-wrapped basalt fiber reinforced polymer (BFRP). Beech and black pine woods were used as cylindrical timber material, polyurethane (PUR) adhesive was used as the adhesive agent, and BFRP was used as fiber-reinforced polymers (FRP). The stress on compression tests was applied to 70 pieces of test samples prepared. The results showed that there was found out that the highest average stress value of 51.8 MPa was achieved inthe black pine cylindrical timber- BFRP wrapping- hollow core (Ø=70 mm)- the beech cylindrical timber blocks- BFRP wrapping samples under compression loading. The lowest average value stress value of 30.78 MPa was found in the black pine cylindrical timber- none hollow core samples. On average, the stress of the black pine cylindrical timber- BFRP wrapping- hollow core (Ø=70 mm)- the beech cylindrical timber blocks- BFRP wrapping samples were68% higher than the stress of the black pine cylindrical timber- none hollow core samples. The influence of the hollow core diameter and the BFRP wrapping type were found statistically significant

WOOD RESEARCH Volume 69, Number 3, 2024
ROMAN HERDA, MILOŠ SLIVANSKÝ, JÁN BRODNIANSKY, and TOMÁŠ KLAS

DETERMINATION OF FLEXURAL STRENGTH AND YOUNG’S MODULUS OF ELASTICITY OF ACTIVELY BENT WOOD

The article focuses on the experimental verification of wooden laths with a cross-section of 10 mm x 40 mm which were selected for active bending. The laths are made of pine wood and are 2 m in length. The research includes experimental measurements to determine the limit deformations achieved by bending the wood without chemical treatment, by applying compressive force to an originally straight beam, causing it to buckle and further deform. Ten bending tests of beams were performed, and from the same pieces, 21 tests were conducted using the four-point bending test to determine the flexural strength, and 30 tests to determine the global modulus of elasticity

WOOD RESEARCH Volume 69, Number 3, 2024
THIPPAKORN UDTARANAKRON, TAWICH PULNGERN, NATTAWAT MAHASUWANCHAI, CHANNARONG SOMBATKAEW, THEERAPAT CHINNARAT, and NARONGRIT SOMBATSOMPOP

FLEXURAL STRENGTHENING OF THERMALLY MODIFIED RUBBERWOOD GLULAM BEAMS WITH FRP UNDER STATIC AND CYCLIC LOADS

The purpose of this research is to investigate the flexural properties and cyclic response of strengthened with fiber reinforced polymer (FRP) of glulam beam made from thermally modified rubberwood. The efficiency of three different FRP was assessed based on the bonding properties. The experimental results demonstrated that the glass fiber-reinforced polymer (GFRP) showed the strongest adhesion. Static and cyclic flexural tests were also carried out to study the behavior of glulam beams. The static test results indicated that double sides strengthened glulam beam enhanced their flexural strength. The strengthened glulam beams under static load demonstrated a reduced deformation rate due to increased modulus of rupture compared to non-strengthening glulam beam. The cyclic load test showed the strengthening effect on improving energy dissipation and ductility, while the impairment of strength did not affect

WOOD RESEARCH Volume 69, Number 3, 2024
ANIF JAMALUDDIN, NIDYA CHITRANINGRUM, SUBYAKTO, BERNADETA AYU WIDYANINGRUM, ARDITA SEPTIANI, SULISTYANINGSIH, WINY DESVASARY, FAJRI DARWIS, AHMAD FUDHOLI, SUDARMANTO, NUR ADI SAPUTRA, EKO WIDODO, and TOSHIMITSU HATA

THE X-BAND MICROWAVE ABSORPTION CHARACTERISTICS OF POROUS ACTIVATED CARBON FROM NATURAL RESOURCES

Porous activated carbon (PAC) from bamboo, sisal, and coconut coir fibres with two carbonization steps were prepared and the microwave absorbing characteristics in the frequency range of 8 GHz to 12 GHz were investigated. The PAC based on bamboo, sisal and coconut coir had BET surface areas of 354.79, 141.91, and 25.70 m2/g, respectively. The return loss of -27.3, -25.6 and -16.4 dB was achieved for PAC from bamboo, sisal, and coconut fiber at 10.46, 11.08 and 11.00 GHz, respectively. The microwave absorption of more than 99% for porous activated carbon of bamboo and sisal, and more than 90% for porous activated carbon of coconut coir fiber, is indicated by these return loss values. It is shown by these results that biomass resources can be considered a promising lightweight, cost-effective, and eco-friendly microwave absorber material

WOOD RESEARCH Volume 69, Number 3, 2024
ZANBIN ZHU, CHUNMEI YANG, WENJI YU, BO XUE, JIE YAN, YUCHENG LI, and TONGBIN LIU

FRACTURE MECHANISM ANALYSIS OF HIGH-DENSITY FIBREBOARD BASED ON DIGITAL IMAGE CORRELATION TECHNOLOGY

This paper analyses the scattering images of the bending deformation of high-density fibreboards based on the digital image correlation (DIC) technique, so as to study its mechanical deformation law. Three-point bending tests were carried out on fibreboards using a mechanical testing machine with a non-contact measuring system. The measured values of the displacements of the grid nodes in the region of interest (ROI) were combined with the Moving least squares (MLS) method to construct the strains of the high-density fibreboards at different loading forces, thus deriving the strain values of the fibreboards during the bending deformation process. To further analyze its force deformation mechanism, this paper used a portable electron microscope and scanning electron microscope to analyze the damage situation at the fracture damage, and at the same time, it verified that the constructed strain field model was accurate

WOOD RESEARCH Volume 69, Number 3, 2024
RUNZHONG YU, YAN LIU, ARIF CAGLAR KONUKCU, and WENGANG HU

A METHOD OF SIMULATING SEAT LOAD FOR NUMERICAL ANALYSIS OF WOOD CHAIR STRUCTURE

This study aimed to investigate the characteristic values of the human-seat interface in a normal sitting posture, and to numerically mode the load on the chair seat for the structural design of chairs. The stress distributions and the characteristic values of seat were measured under normal sitting posture by using a human body pressure distribution measurement system considering the effects of gender and body mass index (BMI). The stress distribution on the seat was then numerically modeled using three modeling methods. The observed results and the numerical analysisresults were compared. The results showed that an inverted U-shaped pressure distribution was observed in normal sitting posture. The stress was concentrated on the ischial tuberosity with a maximum value of 0.066 MPa. The ratio of the load on the seat to the gravity of the human body weight was about 65.3%. The numerical model established using the body pressure mapping method was superior to those of the uniform load method and the standard loading pad method in terms of stress distribution, maximum stress, and contact area

WOOD RESEARCH Volume 69, Number 3, 2024
SHUYU ZHAO, FU HU, LIFEN LI, YAN CAO, HUA GAO, XIAOHUI YANG, and HAILONG XU

EVALUATION OF PROPERTIES OF WOOD PLASTIC COMPOSITES MADE FROM SEVEN TYPES OF LIGNOCELLULOSIC FIBERS

This article aims to investigate the characteristics of wood plastic composites (WPC) prepared from polyethylene (PE) reinforced with lignocellulosic fibers derived from the xylem and bark of Masson pine, fir, cypress, as well as from Moso bamboo. The surface polarity and elemental composition of fibers were determined through contact angle measurements and X-ray photoelectron spectroscopy (XPS). The lignocellulosic fiber/PE composites were manufactured through hot-pressing technique, and their water absorption, mechanical properties, and mildew resistance were evaluated. The results revealed that the surface free energy of xylem fibers was higher than that of bark fibers among the three conifer species. XPS analysis showed that the O/C ratio of bark was consistently lower than that of xylem fiber. Among the three conifers, the Masson pine bark had the lowest O/C ratio (22.25%), while its xylem fibers had the highest ratio of 41.64%. WPC made with bark fibers had better water resistance. Additionally, the composites reinforced with xylem fibers showed superior static bending strength, impact strength, and mildew-resistant properties as compared to the composites reinforced with bark fibers. WPC made from bamboo fibers exhibited the best water resistance, with a water absorption rate and thickness swelling rate of 1.83% and 1.42%, respectively. They also had the highest static bending strength, elastic modulus, and impact strength, at 41.31 MPa, 3.82 GPa, and 10.24 kJ/m2, respectively. The WPC made from fir xylem fibers showed the most effective mildew resistance, with the smallest damage (0.50)

WOOD RESEARCH Volume 69, Number 3, 2024
HILAL ULAŞAN and CEVDET SÖĞÜTLÜ

THE EFFECT OF SUPPORT LAYER MATERIAL AND ADHESIVE TYPE ON COMPRESSIVE DYNAMIC BENDING AND SHEAR STRENGTH IN LAMINATED WOOD

In this study, strength properties of wood material reinforced with carbon fiber fabric, steel wire mesh and bamboo veneer were determined. Polyvinylacetate (PVAc) and polyurethane (PUR) glues (D4)were used for the lamellas obtained from Scotch pine (Pinus sylvestris L.) and eastern beech (Fagus orientalis L.). Compressive strength according to TS EN 408+A1; dynamic bending (shock) strength according toTS ISO 13061-10 and shear strength according to ASTM D 3110 were determined on 3 and 5-layers samples. According to the results, the highest compressive strength (62.8 N/mm2) was found in 5-layerseastern beech samples reinforced with carbon fiber fabric and bonded with PUR glue. The highest dynamic bending strength value (110.8 kJ/m2) was found in 5-layerseastern beech samples reinforced with carbon fiber fabric and bonded with PUR glue and the highest shear strength value (12.3 N/mm2) in 3-layered eastern beech samples reinforced with steel wire mesh and bonded with PUR glue

WOOD RESEARCH Volume 69, Number 3, 2024
SENDER ALTANGEREL, IKUMI NEZU, JYUNICHI OHSHIMA, SHINSO YOKOTA, and FUTOSHI ISHIGURI

CHANGES IN WOOD QUALITY OF BETULA ERMANII LOGS BY HEATING TREATMENT

Logs of Betula ermaniiCham. were heated at a temperature inside the logs of 80°C for different heating durations of 0, 20, 40, and 60 h using a laboratory oven. After heating treatment, several wood qualities were examined, including residual stresses, moisture content, wood color, and physical and mechanical properties. The effects of the heating treatment duration on wood quality were analyzed using linear mixed-effect modeling. The developed models revealed that heating treatment affected residual stresses and wood color but not mechanical properties. The obtained results also suggest that a heating treatment duration of 20 h is sufficient to reduce residual stresses in B. ermaniilogs without reducing the physical and mechanical properties of wood

WOOD RESEARCH Volume 69, Number 3, 2024
CHUMIN CHEN, MING LI, SAIYIN FANG, JIALONG ZHAO, XIN ZHANG, FANGYONG LU, TINGTING DENG, and BO ZHANG

STUDY OF STRESS WAVE PROPAGATION PATH AND DEPTH IDENTIFICATION IN CRACKED WOOD BASED ON ACOUSTIC EMISSION AND COMSOLSIMULATION

The propagation velocity models were built using AE sensors to capture stress wave on pine specimen surface.On the different specimens, cracks were made in different numbers and the depth was gradually increased from 0 mm to 90 mm at 10 mm intervals. AE experiment was combined with COMSOL to investigate propagation path.The results show that R-squared is 0.996 when fitting tangent of angle to propagation velocity.At smaller crack depths, stress wave is diffracted around crack tip and then continues to propagate in to sensor along a straight line.However, as the crack depth increases, the reflected wave at the end face will arrive at the detection location faster with significantly weaker diffraction.The area with dimensions of20×10 mm was identified about the crack tip by crack identification method

WOOD RESEARCH Volume 69, Number 3, 2024
YOSAFAT AJI PRANATA and BAMBANG SURYOATMONO

EXPERIMENTAL TESTS OF RED MERANTI (SHOREA SPP.) DOWEL BEARING STRENGTH AT AN ANGLE TO THE GRAIN

The angle to the grain has a significant influence on timber bearing strength. As the grain angle increases the bearing strength decreases. The aim of this research was to obtain the dowel bearing strength of the red meranti (Shorea spp.) timber at an angle to the grain. The scope of this research was as follows the specimens were made according to ASTM D143, the grain angle ranged from 0° to 12°, and the dowel bearing tests were displacement controlled in accordance with ASTM D5764. Results of this research was an empirical equation of dowel bearing strength (in MPa) in terms of an angle to grain θ (in degrees) namely Fe = 32.74 – 4.701θ + 0.2064θ2. The importance of studying the influence of the grain angle to the dowel bearing strength for timber connection design is because the direction of the timber grain is not perfectly 0°