Mechanical Properties Of Wood Research Articles

Compression test and size effect study of defective wood

ABSTRACT Wood, as a natural material, inevitably contains initial defects such as knots, cracks, and decay, which are important factors affecting its mechanical properties and cannot be ignored. In order to investigate the influence of initial defects on the compressive mechanical properties of wood, Norway spruce was selected as the research object. Wood specimens without and with initial defects were prepared, and uniaxial compression tests were conducted. Combined with Digital Image Correlation (DIC) and finite element analysis, the compressive mechanical properties of defective wood were studied. The results showed that compared to defect-free specimens, specimens with defects exhibited a shortened elastic stage in the load-displacement curve, and the rate of decrease in load after reaching the peak was lower than that of defect-free specimens. For specimens of the same size, the compressive strength of specimens with defects was lower than that of defect-free specimens. The established finite element model could effectively simulate the compressive failure process of wood with initial defects, validating the effectiveness of numerical simulation. Bažant's size effect theory can be used for size effect analysis of the compressive strength of wood with initial defects in the longitudinal direction.

Rosin reinforcement and protection of the unearthed outer coffin from the tomb of Marquis Yi of Zeng in Hubei, China

The tomb of Marquis Yi of Zeng was unearthed in 1978 at Leiguudun in Suizhou City, Hubei Province, China. This is the largest wooden coffin in rock pit and vertical cave in the Warring States period in China. The large wooden coffin components provide reliable material data for the study of the feudal burial system in the pre-Qin period and have high value. In this paper, the wooden coffin excavated from the tomb of Marquis Yi of Zeng was studied. By understanding the composition of wood, studying the weight gain rate, shrinkage rate, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and compression resistance, the wood reinforced by rosin and epoxy resin was compared, and the reinforcement effect and principle of the two reinforcement methods were discussed. The study found that the wood properties of rosin reinforced group were better than those of epoxy reinforced group in the aspects of compressive strength, weight gain rate and volume shrinkage rate, and the mechanical properties of wood were significantly improved. In addition, methanol or ethanol can be used to dissolve the rosin shellac in this strengthening process, which can achieve reversible strengthening treatment. The results provide valuable examples and research ideas for the selection of different conservation techniques of large wooden cultural relics unearthed in the middle and lower reaches of the Yangtze River during the Warring States Period.

Physical and Mechanical Properties of Juvenile Wood of Anadenanthera peregrina (L.) Speg. from Thinning

Reducing the rotation period through thinning and changing planting spacing can influence the technological properties of wood, with little attention paid to the effects of these variables on the raw material, which limits its processing in the wood sector. This work aimed to evaluate the physical and mechanical properties of wood from Anadenanthera peregrina juveniles thinned in three planting spacings (3 m × 3 m, 4 m × 4 m, and 5 m × 5 m). The physical properties in the base––top and pith––shell directions and the mechanical properties of the samples were evaluated. The results indicate better technological properties for wood withwith larger spacings. The physical properties showed decreasing trends in the base––top direction and increasing trends in the pith––bark direction, with a distinct trend in the degree of collapse. The average basic density of the different planting spacings varied between 0.47 g cm−3 and 0.63 g cm−3. The mechanical properties obtained for the 4 m × 4 m spacing were superior to those of the other spacings. Wood from young A. peregrina is an alternative for industrial processing, as wood from higher planting densities is more suitable for purposes that require resistance and rigidity.

Quality of Steam-Treated Bayur (Pterospermum javanicum) and Udu (Litsea accedontoides) Wood

Steam treatment is one of the thermall modification methods that used to improve the quality of wood, especially wood properties related to the presence of water. This study aims to evaluate quality of 2 types of trade wood in the West Nusa Tenggara region, namely bayur wood (Pterospermum javanicum) and udu (Litsea accedontoides) after steam treatment. Steam treatment was carried out at 126 ◦C for 1 hour using an autoclap device. The parameters tested included the physical properties of wood consisting of density, moisture content, volumetric swelling and Anti Swelling Efficiency (ASE). The mechanical properties of wood tested included Modulus of elasticity (MOE) and Modulus of Rupture (MOR). The results showed that steam treatment did not change the density but reduction in moisture content of bayur and udu wood. Based on the Anti Swelling Efficiency value, steam treatment effectively increased the dimensional stability of udu wood with a value of 88.81%. For mechanical property parameters, steam treatment graphically increased the MOE and MOR values of bayur and udu wood. However, according to SNI 03-3527-1194 there was no increase in the strength class of the two types of wood, and both types of wood were included in strength class III.

Quality of Steam-Treated Bayur (Pterospermum javanicum) and Udu (Litsea accedontoides) Wood

Steam treatment is one of the thermall modification methods that used to improve the quality of wood, especially wood properties related to the presence of water. This study aims to evaluate quality of 2 types of trade wood in the West Nusa Tenggara region, namely bayur wood (Pterospermum javanicum) and udu (Litsea accedontoides) after steam treatment. Steam treatment was carried out at 126 ◦C for 1 hour using an autoclap device. The parameters tested included the physical properties of wood consisting of density, moisture content, volumetric swelling and Anti Swelling Efficiency (ASE). The mechanical properties of wood tested included Modulus of elasticity (MOE) and Modulus of Rupture (MOR). The results showed that steam treatment did not change the density but reduction in moisture content of bayur and udu wood. Based on the Anti Swelling Efficiency value, steam treatment effectively increased the dimensional stability of udu wood with a value of 88.81%. For mechanical property parameters, steam treatment graphically increased the MOE and MOR values of bayur and udu wood. However, according to SNI 03-3527-1194 there was no increase in the strength class of the two types of wood, and both types of wood were included in strength class III.

Incipient decay in beech (Fagus sylvatica L.) and linden (Tilia cordata Mill.): An interspecific static and dynamic material analysis

With increasing awareness of the ecological value of trees in urban areas, there is a growing need to preserve mature specimens often colonised by wood-decay fungi. Nonetheless, cases of stem collapse or uprooting of such trees under adverse weather conditions remain a significant issue requiring further investigation. Depending on the decay type and the wood structure of the host tree, different combinations of wood-decaying fungi and host species can have varying impacts on the mechanical and vibroacoustic properties of green wood. This study compares the physical and mechanical properties of green European beech (Fagus sylvatica L.) and small-leaved linden (Tilia cordata Mill.) artificially exposed to Fomes fomentarius (L.) Fr. and Kretzschmaria deusta (Hoff.) P.M.D. Martin after different exposure periods. Mass loss (ML) caused by both fungi differed according to the wood species. A statistically significant difference between the two fungal species was observed in beech wood, but not in linden. Significant differences in the modulus of rupture (MOR) and dynamic bending modulus of elasticity (MOED) were observed among the fungus-wood combinations, also depending on the exposure time. The relationships between ML and MOR varied according to the fungal species, where at the same ML values, K. deusta caused a higher MOR loss in both wood species. Strong relationships between MOED and MOR were demonstrated for all fungus-wood combinations, without significant differences related to the decay type. The MOED is a reliable parameter for predicting MOR loss even at incipient degradation stages, irrespective of the type of decay. The presented results can lead to better prediction of the impact of fungal colonization on standing trees and improve non-destructive methods used for tree stability assessment.

Influence of thermal treatment on mechanical properties of pine wood with regard to prime cost

Influence of thermal treatment on mechanical properties of pine wood with regard to prime cost

Green bio-derived epoxidized linseed-oil plasticizer improves the toughness, strength, and dimensional stability of furfuryl alcohol-modified wood

Furfuryl alcohol (FA) modification represents a sustainable approach to wood modification; however, it significantly reduces the toughness of the wood, limiting its practical applications. This study introduced epoxidized linseed oil (ELO) as an environmentally friendly and bio-derived plasticizer to enhance the toughness and mechanical properties of FA-modified wood. Microstructural analyses confirmed the integration of FA and ELO into the cellular structure of the wood. The chemical interactions between the epoxy groups of ELO and hydroxyl groups of FA were characterized using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, illustrating that a ring-opening reaction occurred that grafted the long flexible aliphatic chains of ELO onto the FA chains, thereby enhancing the chain mobility and flexibility. This interaction significantly decreased the crosslinking density, thereby achieving toughening. FA–ELO modification resulted in significantly enhanced dimensional stability and mechanical properties. Specifically, the anti-swelling efficiency exceeded 80 %, while the modulus of elasticity, modulus of rupture, and along-grain compressive strength increased by up to 35.0 %, 36.8 %, and 45.7 %, respectively. Additionally, significant enhancements in the elongation at break and impact strength were achieved, at 369.1 % and 72.4 %, respectively. The loss factor also increased. The optimal ELO content was 20 wt%. This study effectively demonstrated how ELO mitigates the brittleness of FA-modified wood and supports its application in high-value fields such as construction.

Influence of polyethylene glycol and various carboxylic acids on the physical and mechanical properties of beech wood (Fagus sylvatica) and Scots pine wood (Pinus sylvestris)

ABSTRACT The goal of this study was to investigate the influence on physical and mechanical properties of beech wood (Fagus sylvatica) and Scots pine wood (Pinus sylvestris) modified with polyethylene glycol (PEG) 400 as an alcohol and various carboxylic acids (citric acid, malic acid and 1,2,3,4-butanetetracarboxylic acid). PEG 400, chosen for its large and flexible structure, was expected to minimize the negative effects on mechanical properties. However, contrary to expectations, tensile and impact bending strength decreased – similar to other modifications. Tensile strength decreased (beech: 36.0% to 46.3%), while the modulus of rupture did not show a strong decrease (beech: 2.4% to 15.2%). The modulus of elasticity (beech: 1.6% to 14.7%), compression strength (beech: 11.7% to 40.6%) and hardness (beech: 6.0% to 17.1%) increased. Impact bending strength was reduced (beech: 43.0% to 69.3%). Modifying agents, fixed inside the wood, demonstrated high anti-swelling efficiency during leaching cycles (beech: 27.1% to 45.9%). Equilibrium moisture content was reduced between 20.8% and 39.1% for beech at a relative humidity of 65%.

Effect of slope of grain on mechanical properties of some tropical wood species

ABSTRACT The aim of this work was to study the relationship between the mechanical properties of Cameroonian tropical woods and the slope of grain. The forests of the Cameroonian part of the Congo Basin abound in species that are highly solicited for structural applications. However, little information is available on the influence of the slope of a grain of these wood species. Clear wood specimens of ayous (Triplochiton scleroxylon), azobe (Lophira alata), fraké (Terminalia superbe), okan (Cylicodiscus gabunensis), padouk (Pterocarpus soyauxii), and sapelli (Entandrophragma cylindricum) were prepared. The specimens have a cross section of 20 × 30 mm and a length of 300 mm. These specimens were subjected to a four-point bending test and a double cantilever beam test. Modulus of elasticity (MOE), modulus of rupture (MOR), work at maximum load (WML) and fracture toughness (GIC) were determined. These mechanical properties were calculated for specimens with slopes of grain 0°,15°, 30°,45°,60°, 75° and 90°. The results showed that the slope of grain had significant effects on all the mechanical properties measured on clear wood specimens. MOE, MOR, WML, and GIC decreased with increasing grain slope. On the other hand, azobe and okan absorb much more of the energy that causes microcracking than the other species.

Estimation of the earlywood and latewood ratio with different particle size of dry and wet milled Japanese cedar wood flour by using hyperspectral imaging

Mechanical properties of wood–plastic composites are influenced by a particle size and surface morphology of wood flour. Generally various sizes of wood flour are produced from single solid wood even if the single process is used. If the different particle size of wood flour is produced from different wood tissue such as earlywood (EW) and latewood (LW), not only particle size but also density and chemical composition of wood flour might influence the mechanical property of final products. This study aims to investigate the relationship between particle size and their origin; EW and LW. EW and LW were separately milled to produce the EW and LW flour by dry and wet milling. Hyperspectral images ranging 400–1000 nm for each wood flour were used as training data. Discriminant model of EW and LW flour developed by PLS-DA showed over 0.77 of accuracy. Then the EW and LW were dry and wet milled together and screened by three different sieve openings to obtain different particle size wood flour. Discriminant model was applied for the hyperspectral images of each size of wood flour to estimate the EW and LW ratio. The result showed that increasing sieve opening resulted in the increasing ratio of LW for dry milled wood flours. The results suggest that the EW was easily pulverized than LW.

Enhancing weatherability and mechanical properties of tung oil wood finishes through natural rubber modification via the Diels-Alder reaction

Tung oil is commonly utilized for coating protection in wooden products, often attracting attention for its appearance, antimicrobial capabilities, and insect-resistant coatings. However, its poor mechanical properties and poor weather resistance stem from excessive self-crosslinking of surplus conjugated double bonds and molecular chains, resulting in poor film wrinkling. Therefore, this study introduces natural rubber via the Diels-Alder reaction to consume the residual double bonds in tung oil, resulting in tung oil/natural rubber composite coatings (NRTO) with excellent mechanical properties and weather resistance. The results indicate that NRTO exhibits excellent mechanical properties, including high elongation (32 %) and strong adhesion (4.55 MPa). Furthermore, NRTO demonstrates outstanding acid resistance and UV aging resistance. Given its many benefits, NRTO film emerges as a promising candidate for substantially protecting wood surfaces in demanding environments.

Response relationships between the color parameters and chemical compositions of heat-treated wood

Abstract The magnitudes of the color changes in heat-treated wood are closely related to the chemical composition of the wood, and changes in the chemical composition are the essential reasons for changes in the mechanical properties of heat-treated wood. The response relationships among the color parameters of heat-treated wood and the chemical composition were constructed to provide a scientific basis for regulating the mechanical properties with the color. The effects and linear correlations of the lightness indicators (L*) for poplar (Populus tomentosa Carr.) and spruce (Picea asperata Mast.) after heat treatment were related to the chemical compositions of the heat-treated woods by constructing relationships between the L* values. The relative content of cellulose in the heat-treated poplar downward trend and was significantly positively correlated with the L* value; however, the correlation with the L* value for the heat-treated spruce was insignificant. The L* value of the heat-treated wood was significantly positively correlated with the relative contents of hemicellulose, and was significantly negatively correlated with lignin. The L* value of the heat-treated wood had a superior response relationship with the crystallite sizes. Therefore, the constructed response relationship provides a theoretical basis for accurate and nondestructive testing of the mechanical properties of heat-treated wood by using the color parameters as rapid detection indicators.

Evaluation of Mechanical Wood Properties of Silver Birch (Betula pendula L. Roth.) of Half-Sib Genetic Families

Silver birch, a widely distributed deciduous tree native to Europe, is valued for its wood applications in construction, furniture making, and paper production. In Lithuania, silver birch ranks as the third most common forest-tree species, comprising 22% of the forested areas, and is an important species for tree breeding due to its potential and adaptability. This study was focused on assessing the mechanical properties of wood (sample and log hardness, wood density, dynamic modulus of elasticity (MOEdyn), static modulus of elasticity (MOE) and bending strength (MOR)) in silver birch (Betula pendula L. Roth.) trees from different half-sibling families. Two experimental plantations of the progenies of Lithuanian populations (half-sib families) of silver birch from different regions were analysed. From these plantations, four genetic families were selected for mechanical properties evaluation. The study findings revealed significant variability in various wood properties among different genetic families, although the static modulus of elasticity did not exhibit significant differences between the chosen genetic families. All measured wood properties decreased from the bottom to the top of the model trees. Wood hardness displayed a moderately negative correlation for wood density and weak correlations for MOE and MOR. Given the weak correlations between wood hardness and other wood mechanical properties, it is suggested that MOEdyn would be a more suitable trait for genetic studies.

Effects of oil heat treatment on poplar wood properties: A pilot scale study

Pilot-scale oil heat treatment was conducted to enhance the quality of poplar wood obtained from a fast-growing plantation. Three target temperatures, namely 180, 190, and 200 ˚C, were chosen for the oil heat treatment process. Clear, small specimens were cut from the lumber, following the prescribed standards for assessing wood quality. Light microscopy revealed the ruptures and deformation of the wood cell wall as the treatment temperature increased. The volumetric swelling of the treated specimen decreased proportionally with the increase in treatment temperature. The impact of oil heat treatment on the mechanical properties of wood varied depending on the specific type of mechanical strength and processing temperature. The modulus of rupture, toughness, and hardness of the treated specimens drastically decreased at 200°C. However, the specimens treated at 200°C exhibited much lower mass loss during the fungal decay test. The results of the analytical test showed an increase in the crystalline cellulose content and thermal stability of the treated wood, due to the thermal degradation of hemicelluloses and amorphous regions of cellulose. Overall, it is concluded that oil heat treatment of poplar wood in the optimal temperature is an efficient approach to upgrade its quality with minimal reduction in mechanical strength.

The influence of road traffic and industrial plant-induced air pollution on the physical, mechanical, chemical and morphological properties of the black pine wood

Road traffic pollution and industrial plant-induced pollution affect negatively the development of forest trees. How forest trees are affected by their growing environment is important for sustainable environment. The study aimed to investigate the physical, mechanical, chemical, and morphological properties of the Pinus nigra (black pine) tree which grows under different conditions. Tree samples were chosen from three different lands where were inside the forest (O), near the roadside (Y), and near the factory (F). It was studied whether there were any significant differences among the “O”, “Y” and “F” in terms of their wood properties such as physical, mechanical, chemical, and morphological. As a result, the “O” samples demonstrated more regular annual ring structure. On the other hand, it was observed that the “Y” samples had longer and wider tracheid cells. In addition, “Y” samples had better mechanical strength than “O” and “F”. Environmental pollution caused the presence of some different elements (chlorine and iron) in “Y” and “F”. As a result, it was determined that the trees growing near the roadside or near industrial plants have significant differences from forest trees which are far away from pollutions. It is possible to say that Pinus nigra (black pine) is resistant to environmental stress. For this reason, it can be recommended to use it as a barrier to reduce air pollution on the roadsides.

Mechanical properties of jabon (Neolamarckia cadamba (Roxb.) Bosser) wood 13 years old and its potential utilization as a structural material

Jabon (Neolamarckia cadamba (Roxb.) Bosser) is a type of fast-growing tree that is expected to meet the national demand for wood because it has fast-growing properties. This study’s objective was to examine the mechanical properties of 13 years old jabon wood based on its position in the stem. The preparation of mechanical properties test samples and their tests refer to the British Standard (BS) 373 Methods of testing small clear specimens of timber and the American Society for Testing and Materials (ASTM) D143 Standard test method for small clear specimens of timber. Based on the results of the study, the stem parts (bottom, middle, and top) had no significant effect on the mechanical properties of wood except for the compressive strength parallel to the grain and hardness. In general, the mechanical properties showed an increase from the bottom to the top of the stem and from the pith toward the bark, although there were some differences. The mechanical properties of jabon wood obtained from this study generally showed higher values than jabon wood used in other studies with younger ages, although in general, it did not change the category of jabon wood from strength class III-IV. However, its use as a structural material would be more profitable than using a younger age of jabon wood, as it is usually harvested so far.

EVALUATION OF DYNAMIC AND STATIC MODULI OF ELASTICITY OF HYBRID EUCALYPTUS WOOD FROM DIFFERENT LOCATIONS IN GHANA

This study explores the mechanical properties of hybrid eucalyptus wood, with a focus on dynamic and static moduli of elasticity (MOE), which is crucial for understanding the stiffness behaviour of wood. The research employs acoustic and static measurements on samples prepared from six trees sourced from Winneba and Amantia in Ghana. The results reveal significant variations in static and dynamic MOE, with higher static MOE observed in both Amantia and Winneba samples. However, Winneba and Amantia samples at the tree level were found to be insignificant statistically. The densities of the samples from the two locations, Winneba and Amantia, were found to be significantly different. Correlation studies revealed strong relationships between wood density and static MOE, as well as static and dynamic MOE, providing valuable insights into the comprehensive characterization of the eucalyptus globulus species grown in Ghana.

Impact of Wood-Boring Larvae of Xylotrechus arvicola (Coleoptera: Cerambycidae) on Mechanical Properties of Vitis vinifera Plants

Xylotrechus arvicola represents a significant insect pest impacting Vitis vinifera within the principal wine-producing territories of the Iberian Peninsula. The larvae of this species bore into grapevine wood, resulting in significant structural and biomechanical deterioration to the plant. Compressive and flexural tests were conducted to assess the mechanical properties of wood affected by X. arvicola. Compressive and flexural strength exhibited a decline with the escalation of the Total Damaged Surface Area (TDSA) of the samples, ranging from 0.31% to 0.73% in trunks and from 0.04 to 0.76% in branches, irrespective of the wood moisture content (fresh and dry). The most significant reduction in resistance occurred in affected dry trunks and branches. Notably, the deflection at break for dry samples was lower compared to fresh samples (65.00 and 97.85 mm, respectively). Moreover, the deflection at break for affected fresh samples (164.37 mm) significantly surpassed that of unaffected fresh samples (72.58 mm) and affected dry samples (37.50 mm). It is noteworthy that a higher percentage of TDSA coincided with diminished wood resistance. The percentage of fungal growth symptoms observed in affected wood samples was 66.66% for dry trunks, 75.00% for fresh branches, and 60.00% for dry branches. The damage inflicted by larvae facilitated the spread of grapevine diseases via emergence of holes created by insects upon exiting the wood and through the larval galleries connected to them. This damage also altered the mechanical properties of grapevine plants, with fresh branches exhibiting the most pronounced effects.

Effect of the Hole Diameter in Mechanical Properties of Wood: Experimental and Numerical Approaches

Introducing openings or holes into wooden structures is a common practice for providing utility services. However, this practice leads to stress concentration, resulting in a reduction in stiffness and load-carrying capacity. Therefore, understanding the effects of holes on beam properties is important for design considerations. This study investigates the mechanical behavior of a wooden beam made from juvenile Pinus elliottii containing open cylindrical holes with three different diameters: 4, 8, and 12 mm. The mechanical properties were evaluated for compression parallel to the fibers, quasi-static bending, and tension perpendicular to the fibers. Numerical simulations were conducted using a finite element (FE) model, considering the orthotropic elastic properties determined from experimental tests and elastic ratios reported in the literature. The experimental results indicated that the influence of hole diameter was not significant on the compressive properties; however, longitudinal crack failures began to form for holes with diameters of 8–12 mm. Regardless of hole size, the compressive and bending characteristics revealed that hole location did not affect the stiffness, strength, or damage mechanisms.