Strength Of Wood Research Articles

Decay resistance and mechanical strength of poplar wood treated after injection treatment to living trees using ammoniacal copper quaternary/carbon dots

ABSTRACT As a cutting-edge wood preservation technology, injection treatment to living trees has gained traction to prevent fungal infestation. Wood preservatives are injected into the lower part of the trunk and subsequently transported with xylem sap through transpiration. In this experiment, the waterborne wood preservative was synthesized by Ammoniacal Copper Quaternary (ACQ) and carbon dots (CDs), and its characteristics were determined. The distribution, loading capacity, and decay resistance of ACQ/CDs at different heights of the living poplar trees after the treatment were examined. Meanwhile, the effects of three methods, i.e. injection treatment, immersion treatment, and pressure treatment on the decay resistance and mechanical properties of the treated wood were explored. The results showed that the wood preservative penetrated well into the xylem after the injection treatment. The wood at different heights after the injection treatment had good decay resistance. The decay resistance diminished with the rise in tree height, attributable to variations in the timing of the preservative reaching different levels within the tree. When compared with the immersion and pressure treatments, the injection treatment can effectively reduce the influence of long-term preservative soaking and pressure application on the mechanical properties of the treated wood, while upholding commendable decay resistance.

Muscle supercompensation inspired high-strength partially dissolved-regenerated cellulose biochar as the matrix of phase change materials for thermal storage

Balsa wood is widely planted as a light wood and easily available. However, the low strength of balsa wood limits its application scenarios. Based on the concept of muscle supercompensation, we reported cellulose partial dissolution and regeneration methods of wood to synthesize high strength matrix for preparation of efficient shape-stable phase change materials (ss-PCMs). Notably, part of the cellulose of the balsa wood was deconstructed, and a nano-scale entangled regenerated cellulose structure was formed in ethanol. The obtained carbonized cellulose regeneration wood (CRW) shows a hierarchically porous network with high mechanical strength and the specific surface area of CRW was around 17 times higher than that of natural balsa wood. The CRW exhibited high adsorption capacity for tetradecanoic acid (TA), and the maximum content of TA adsorbed in CRW was calculated to be 90.3%. Moreover, the CRW based ss-PCMs (CRPs), prepared by using CRW as carrier and TA as core material, can effectively improve the photo-thermal conversion efficiency of CRPs to 83.6%. This “wood supercompensation” strategy has the merits of simple and degradability, which provides a new approach for the recycle of lignocellulose and a promising way for the production of ss-PCM with high strength and excellent energy storage capacity.

EFFECTS OF DIFFERENT CLIMATE TYPES ON COLOR CHANGE OF WOOD MATERIAL USED OUTDOOR

Field tests are important for evaluating how wood performs in real-world conditions and making informed choices for material selection. These tests help assess wood's durability, strength, decay processes, and resistance against harmful organisms. Furthermore, it helps users make more informed decisions about the color of wood and understand the importance of color changes depending on the place and time of use. Because weather conditions are asignificant factor that influences the color of wood. Wood that is exposed to prolonged sunlight, moisture, and rain may experience fading, darkening, or staining in its color. In this study, heartwood, sapwood, and CCB impregnated sapwood samples of Scotchpine, spruce, beech and alder were exposed to the soil contact (hazard class 4) according to EN252 for 3years in Trabzon, Muğla, Çanakkale, and Elazığ provinces of Turkey with completely different climatic conditions from each other. Color parameters and color change values were evaluatedusing L*, a*, b*and ∆E* of the samples collected from test sites. The most significant color change was observed at Scotchpine in Çanakkale province. Greater color changes were observed in theheartwood of coniferous species.Impregnated samples showed the least color change.

Combined effect of rays and vessels to achieve high strength and toughness in balsa wood

Balsa wood, as one of the lightest woods available, presents superior mechanical properties, and thus it is one of the most appealing core materials particularly for marine and aerospace applications. However, the strengthening and toughening mechanisms in balsa wood are still poorly understood. The present work indicates that the samples exhibit higher strength and toughness concurrently, provided the loading direction is perpendicular to rays; in this case, vessels with strong walls can provide mechanical support, blunt cracking and stop horizontal cracking, and rays can arrest axial cracking. The present research findings are expected to provide fundamental insight into the design of high-performance bionic materials with a highly fibrous and porous structure.

The Effects of Seawater Treatment on Selected Coniferous Wood Types.

The mechanical strength of wood from Scots pine (Pinus sylvestris), European larch (Larix decidua), and Norway spruce (Picea abies) was studied using static compression tests. The material was exposed under constant soaking in water with salinity of 7‱. The liquid mix was prepared according to a value roughly equivalent to the average salinity along the entire length of the Baltic Sea. The mechanical strength and quality of the raw material were determined using a sea salt saturation test, which determined the adhesion of the raw material to the extrusion process (permissible stress). An investigation was conducted to determine the physicochemical parameters of the material that was tested. It was investigated how much mineral compounds were absorbed over four cycles lasting a total of six weeks during the test. According to the statistical analysis, the chemical composition of wood and the presence of salts and mineral compounds correlated with its mechanical strength. An important part of the study focused on examining the factors affecting the construction of coniferous wood structures. The preparation of the raw material correctly can provide information on how the material can be protected during exposure to specific environmental conditions for longer.

Constructing a rigid-flexible grid structure for simultaneously strengthening and toughening bamboo flour/plastic composites through the introduction of continuous carbon fabric meshes via multi-layer co-extrusion

The defects of low strength, brittle fracture, and creep deformation of traditional wood–plastic composites (WPCs) significantly limit their applications as high-value-added products. This study aimed to develop advanced WPCs with high strength, toughness, and creep resistance via a structural design. A continuous rigid-flexible grid structure, sandwiched by carbon fabric mesh prepreg (CFMP) and casting film (MSF) with high toughness, was introduced into bamboo flour/high-density polyethylene composites (BPCs) via a multi-layer co-extrusion technology. The sandwiched grid structure was in-situ cured in the near-surface layers of BPCs to form a multi-layer composite (BPC-CFMP-F) during co-extrusion. The tensile strength, flexible strength, and impact strength of BPC-CFMP-F were 68.4 MPa, 89.0 MPa, and 22.5 kJ m−2, which are 138.3%, 96.4%, and 87.6% higher than those of BPCs, respectively, and the thermal expansion and 1000-hr creep strain of BPC-CFMP-F decreased by 45.8% and 61.7%, respectively. The simultaneous strengthening and toughening of BPCs were attributable to the rigid-flexible grid structure and the strong interfacial bonding between CFMP and BPCs and the surface- and core-layer BPCs through the grid of CFMP. Owing to these unique features, BPC-CFMP-F is a promising advanced composite with high strength, toughness, excellent creep resistance, and thermal stability for high value-added applications.

Fully bio-based adhesive designed through lignin-cellulose combination and interfacial bonding reinforcement

Herein, lignin was functionalized to obtain quinonoid lignin (QL) and epoxidized lignin (EL), and cellulose was modified to be aminated cellulose (AC). A novel fully bio-based adhesive of QL-AC-EL with multiple cross-linked networks was designed based on Schiff base and addition reaction. Furthermore, the natural wood interface was activated by brushing aqueous solution of 3-aminopropyltriethoxysilane (APTES) to obtain a functional interface with many -NH2 groups. Finally, the created QL-AC-EL was used as a specific adhesive to glue wood interface with abundant -NH2 groups. The bonding performance was evaluated that the dry strength of the plywood specimens made from activated wood interface was 3.2 MPa, which increased by 123.8% than that of natural wood interface. It is amazing that the wet strength of plywood by using activated wood interface was 1.73 MPa, whereas wet bonding strength of natural wood was zero. The significantly improvement of the bonding properties should be caused by the covalent crosslinking between adhesive and activated wood interface, which plays an important role in the enhanced water resistance of the interfacial bonding stability. This work provided a new inspiration for the design of bio-based adhesives with excellent performance and water resistance from the interfacial chemical bonding perspective.

Сравнительная оценка физико-механических свойств древесины различных климатипов сосны обыкновенной

It is important to comprehend the physical and mechanical properties of Scots pine wood from various geographical origins in order to use it effectively and rationally in production. The purpose of the study is to determine the physical and mechanical properties of Scots pine wood from 17 climatic ecotypes and to conduct a comparative analysis of the received indicators for the studied climatypes separately and for subspecies, which were grouped according to the classification of L.F. Pravdin. The physical properties that were chosen for the investigation were wood density in an absolutely dry state and at 12 % moisture content. The mechanical characteristics were the tensile strength of the wood along the fibers and the tensile strength in static bending. The range of geographic origins of the seed harvesting locations was from 47 to 62 °N and 22 to 85 °E. The investigation was conducted using contemporary universal testing equipment, MTS Insight 100. It was found that the density of the wood varied from 370 kg/m3 (Kursk climatype) to 524 kg/m3 (Volgograd climatype) under absolutely dry conditions and from 397 kg/m3 (Kursk climatype) to 550 kg/m3 (Volgograd climatype) at 12 % moisture content. The tensile strength of wood along the fibers ranged from 32 MPa (Kursk climatype) to 54 MPa (Volgograd climatype), while the tensile strength in static bending was from 55 to 92 MPa for the Vologda and Ulyanovsk climatypes, respectively. The maximum wood density at 12 % moisture content was 497±8 kg/m3, which is typical for European subspecies. The minimum value of this indicator was 423±30 kg/m3. The medium values had Lapland subspecies and Steppe subspecies 483±16 kg/m3 and 464±12 kg/m3, respectively. The tensile strength of wood along the fibers in the studied subspecies ranged from 47±1 MPa (European subspecies) to 33±4 MPa (Siberian subspecies). For Lapland subspecies, it was 44±2 MPa and slightly lower for Steppe subspecies, which was 42±2 MPa. The maximum value of the tensile strength in static bending for European subspecies was 78±4 MPa. The minimum value for the Siberian subspecies was 61±14 MPa. This indicator was equal for Steppe subspecies and Lapland subspecies, which was 72±4 MPa. For citation: Rabko S.U., Melnik P.G., Kozel A.V., Paplauskaya L.F., Tupik P.V., Nosnikau V.V. Comparison of Physical and Mechanical Properties of Scots Pine Wood Grown in Different Climatypes. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 4, pp. 26–40. (In Russ.). https://doi.org/10.37482/0536-1036-2023-4-26-40

Hybrid Wood Composites with Improved Mechanical Strength and Fire Retardance Due to a Delignification–Mineralization–Densification Strategy

The shortage of wood resources and the policy of logging restrictions have hindered the development of the wood industry. The development of fast-growing wood can effectively solve the problem of wood shortages and the discrepancy between supply and demand; however, the softness and poor strength of fast-growing wood make it difficult to use directly and restrict its applications. Meanwhile, the inflammability of wood is also a crucial hindrance to its application. In this work, hybrid wood composites with high strength and excellent fire retardance were developed by using a combined strategy of “delignification–mineralization–densification”. Delignification promoted the deposition of minerals inside the wood, and the mineralization process was able to significantly increase the fire retardance performance of the hybrid wood. The densification treatment made the wood and minerals closely packed, which was conducive to the improvement of the strength and fire retardance performance of the hybrid wood. The resulting hybrid wood composites showed enhanced mechanical strength (the tensile strength, flexural strength, and compressive strength were 180.6 MPa, 159.8 MPa, and 86.5 MPa, respectively) and outstanding fire retardance, and this strategy provided a feasible pathway towards the high-value application of fast-growing wood.

Experimental Study of Glued Laminated Timber (Glulam) from Jackfruit Wood and Coconut Wood for Timber Beams of Level Houses in East Nusa Tenggara

Wood is a construction material that is familiar to the wider community. Wood can be used in construction. The purpose of this study was to determine the specifications of the physical properties, mechanical properties, tensile strength and flexural strength of laminated wood (glulam), in jackfruit and coconut wood beams originating from the East Nusa Tenggara region in multi-storey house buildings. The tests carried out included testing the water content, testing the tensile strength and bending strength, testing the tensile strength and bending strength on glulam beams using epoxy glue adhesives. The results of this study showed that jackfruit wood and coconut wood aged 15 years and 20 years had an average moisture content of 15 years, namely 15% and 26%, the average specific gravity was 0.54 (tons/m3) and 0.46 (tons/m3). Meanwhile, the average water content for 20 years is 15% and 32%, the average specific gravity is 0.58 (Ton/m3) and 0.45 (Ton/m3). The tensile strength of intact and glulam wood of jackfruit and coconut wood was obtained from laboratory results on SNI 7973-2013 calculations, the average tensile strength of intact jackfruit and coconut wood was 84.40 MPa and 80.73 MPa. The flexural strength of intact beams and glulam of jackfruit and coconut wood aged 15 years was obtained from laboratory results on SNI 7973-2013 calculations of the flexural strength of intact beams for 15 years, the average being 71.81 MPa and 26.07 MPa. At 15 years of age, the flexural strength of glulam beams was the highest variation 1 and variation 2 (Jackfruit, Coconut, Jackfruit) mean 76.00 MPa and 41.85 MPa. The flexural strength of intact beams and gulam of jackfruit and coconut wood aged 20 years was obtained by laboratory results on SNI 7973-2013 calculations of flexural strength of intact beams, which were 80.27 MPa and 29.73 MPa respectively. At the age of 20 years, the highest flexural strength of glulam beams were variations 1 and 2 (Coconut, Jackfruit, Coconut) with an average of 80.40 MPa and 48.76 Mpa.

The impact of resin harvest history on properties of Scots pine wood tissue

This study was conducted in Central Europe (Poland) in pine forests that were subjected to the process of resin harvesting in the 1970s. Forty trees were designated for the study, which had one or two resin blazes. The objectives of the experiment were to determine the effect of resin tapping on the changes in annual growth, wood density, and mechanical strength of wood in the damaged trees. Resin tapping affected the development dynamics, especially in trees with a single resin blaze. In addition, bark cutting affected wood density over the cross-section. However, no significant variation was found in terms of the mechanical properties of wood, which may support the theory of adaptive tree growth and optimization of tree’s structure to its functions.

Effects of Growth Ring Width, Height from Tree Base, and Loading Direction on Transverse Compression of Plantation Japanese Larch Wood

This study aimed to investigate the effects of growth ring width, height from the tree base, and loading direction on the transverse compressive strength of Japanese larch wood, which is commonly used in wood structures in China. Plantation wood is often used to replace natural forest woods for reconstruction purposes, despite significant differences in properties (e.g., growth rings, density, strength) between them. The ends of transversely compressed wood members in such structures are prone to damage by breaking or crushing. A transverse compressive test was conducted following Chinese national standards, which revealed the following key findings. (1) There was a significant difference in the transverse compressive strength of wood with different growth ring widths (p < 0.05). The radial and slant compressive strength of wood increases with growth ring width, while the tangential compressive strength decreases as growth ring width increases. (2) The transverse compressive strength of wood decreases as the height from the tree base increases. The radial, tangential, and slant compressive strength at a lower height were 18.39%, 22.58%, and 18% higher than those at a greater height in the stem, respectively, with significant differences at the 0.05 level. (3) The load–displacement curve of Japanese larch wood under radial and slant compression follows a “three-segment” form. In contrast, the load–displacement curve of tangential compression is a continuous curve that drops sharply upon reaching its highest point. (4) There is a significant difference in the transverse compressive strength of Japanese larch wood in different loading directions when growth ring width and height from the tree base are constant (p < 0.05), which fall into order as tangential > radial > slant.

The effect of growth-ring orientation on the compressive performance of Douglas fir

ABSTRACT The effect of angle between growth-ring orientation and loading force on mechanical performance such as compressive strength, deformation and compression set-recovery of wood has not been fully understood. The specimens, with growth-ring orientations of 0° (G-0°, parallel to tangential direction), 15° (G-15°, angle between growth-ring and tangential direction) and 40° (G-40°), were compressed using a universal testing machine; meanwhile, strain distribution was recorded using digital image correlation (DIC). One specimen from each growth-ring orientation was scanned with X-ray computed tomography (X-ray CT) before and after compression test. Their micro-structure after compression test was imaged using a scanning electron microscope (SEM). The results show that compressive strength decreases and compression set-recovery increases as increasing the growth-ring orientation. In G-0° specimens, strain is easily accumulated in small regions in earlywood, resulting in structural compaction and collapse. The effect of latewood on compressive strength is small, resulting in a poor correlation between strain distribution and density profile. For G-40° specimens, strain is almost homogenously distributed in every layer of earlywood. Both earlywood and latewood restrain the specimen from deformation and failure. Hence, strain accumulates according to the ‘layers’ of earlywood. Strain distribution and structural changes in G-15° specimens were in between of G-0° and G-40° specimens.

ЩОДО УДОСКОНАЛЕННЯ ДІЮЧИХ НОРМАТИВНИХ ДОКУМЕНТІВ ДЛЯ РОЗРАХУНКУ ЗГИНАЛЬНИХ ДЕРЕВ’ЯНИХ ЕЛЕМЕНТІВ ТА КОНСТРУКЦІЙ

The most common use of wood in construction is for bending elements. The calculation of bending members made of glued laminated timber requires the use of the section modulus of this member and the calculated values of the bending strength of the timber. The design bending strength of wood is determined based on the characteristic values obtained from the laws of elastic material under load. However, this statement completely contradicts the anisotropy of wood in its tensile and compressive behavior. If it is known that wood works 90-95% to failure in longitudinal tension, it is then it can be assumed that it is elastic at all. However, in longitudinal deformation, there is non-linear behavior with increasing elastic and plastic strains. Furthermore, the longitudinal tensile strength of wood is almost twice that of longitudinal compression. Therefore, even if the relative deformations in the wood are the same different compressive and tensile stresses arise in the bending element, i.e. . Many authors who have carried out experimental and theoretical studies on the performance of timber beams have pointed out that the neutral force line in the cross-section of the element in direct transverse bending, with increasing levels of single load, shifts towards the tensile zone. Therefore, using the moment of resistance of the cross section in the wooden element to determine the section modulus is incorrect. The moment of resistance of a section of a timber member is only determined if the centre of gravity of the section coincides with the centre of force line. Usually, the failure of long wooden beams ( ) in transverse bending usually occurs due to the fracture of the most stressed outer layers of wood in the of the tensile area and is brittle in nature. It is on such elements that the the temporary bending strength. It is on such elements that the bending strength is crucial. However, the values of , usually determined in the outermost wood layers of the tensile zone, based on the condition, only reach values of 70-75% of the longitudinal tensile strength of wood . It is not possible to determine the tensile strength of wood at this stress level. Therefore, the results of determining the bending strength of wood using the moment of resistance of the cross-section of a timber element determined in the limiting condition are erroneous due to the impossibility of establishing values

Interactions of hydrophilic birch wood (Betula pendulaRoth) extractives with adhesives for load-bearing timber structures

This study investigated how water-soluble extractives of silver birch (Betula pendulaRoth) wood interact with the most common adhesives used for producing engineered wood products (EWPs), i.e., melamine-urea-formaldehyde (MUF) and one-component polyurethanes (PUR). Therefore, the extractives were characterized via various chromatographic techniques and mass spectrometry. The effects of extractives on the curing kinetics were investigated using rheometry. The impact of extractives on the chemical and mechanical properties of the cured adhesives was investigated with FTIR spectrophotometry and tensile stress-strain measurements, respectively. Moreover, a comparative study on the shear strength of birch wood with and without extractives was performed.The organic fraction of the water extractives of birch mainly consisted of phenolic glycosides, carboxylic (fatty) acids, and saccharides. The extractives decelerated the curing process of MUF, as observed in a rheological small-angle oscillatory shear experiment using wood substrates as the lower plate. This was indicated by a reduced gel time from 5 to 3.8 h on pristine vs. extracted wood. When measuring MUF on extracted wood, this deceleration was also reached by adding ∼1% (W/W) of the isolated extractives into the MUF resin. Similar experiments with PUR showed a slight acceleration when dispersing extract into the adhesive, indicated by a reduction of vitrification time of −0.9 ± 0.3 h per percent of extractives added. However, measurements with pure PUR on pristine and extracted wood showed no significant difference in curing kinetics due to the extractives’ limited mobility and solubility in PUR. Both PUR and MUF cured adhesive films showed a reduced stiffness, elastic stress limit and tensile strength in uniaxial tensile stress-strain measurements of adhesive films upon increasing the amount of hydrophilic birch extractives concentration. Comparative standard tensile shear strength measurements on pristine and extracted wood indicate a 7–19% strength increase due to extraction when bonding with MUF, while the bond strength of PUR bond lines was less affected by the extraction procedure.

Effects of Plasma Treatment on the Surface Characteristics and Bonding Performance of Pinus massoniana Wood

Rosin has a great influence on the bonding of Pinus massoniana wood, and surface modification is an important way to solve this problem. In this study, Pinus massoniana wood was treated by plasma, and the effects of plasma treatment on the bonding performance and surface characteristics were investigated. The results showed the following: (1) After plasma treatment, the contact angle of Pinus massoniana wood was significantly reduced and the surface energy was significantly increased from 28.42 × 10−7 to 74.75 × 10−7 J·cm−2, and the surface wettability was also greatly improved. (2) Plasma high-energy particles experience simultaneous physical and chemical effects on the surface of Pinus massoniana wood. The former formed a micro-etched roughness on the wood surface and led to the increase in surface dispersion force, while the latter increased the aggregation and activity of polar groups on the wood surface and the degradation of some wood components and rosin, resulting in the increase in surface polar force and the enhancement of wettability. (3) After plasma treatment, the reactivity of wood was enhanced, and the cross-linking degree with adhesive and the heat release were increased. The bonding strength of Pinus massoniana wood could be improved: dry bonding from 5.08 to 5.38 MPa, boiling-water bonding strength from 4.12 to 4.53 MPa, cold-water bonding strength from 3.84 to 4.51 MPa, and the bonding stability and reliability of glued specimens were also improved.

Parametric study of wood sheathed cold formed steel shear wall panels using OPENSEES

CFS members are widely used in transmission towers, bridges, and building structures. They are lightweight, stiff, and robust materials suitable for low-rise constructions. However, their lateral load capacity is limited, and to overcome this challenge, SWPs are employed in CFS structures to resist lateral forces. SWPs consist of CFS studs and tracks attached to sheathings, which can be made of metal or wood. This study aims to evaluate the lateral strength of wood sheathed SWPs. These panels can effectively dissipate energy under lateral loading due to the combined inelastic behaviour of their components: Frames, Sheathing, and screw connections. A precise material model is required to simulate this inelastic behaviour accurately under quasi-static or dynamic loading. Therefore, this study develops an algorithm to accurately model the linear behaviour of wood-sheathed SWPs. OPENSEES software is used for nonlinear behaviour, employing zero-length elements, the pinching4 material model, and the EEEP rule. The proposed analytical method is applied to analyse the lateral strength of wood-sheathed SWPs. Nonlinear static analysis, including cyclic and monotonic push tests, is performed using the proposed method for OPENSEES. Moreover, the study investigates various physical parameters that affect the nonlinear behaviour of wood-sheathed SWPs, such as screw spacing, sheathing thickness, screw diameter, and aspect ratio. Finally, a sensitivity study is conducted to evaluate the cyclic response of wood-sheathed SWPs by analysing the key physical parameters.

Adding gaseous ammonia with heat treatment to improve the mechanical properties of spruce wood

Abstract Degradation of the mechanical properties of heat-treated wood is a significant problem that needs to be addressed. This study aimed to stabilize the mechanical strength of heat-treated spruce wood by adding gaseous ammonia during the heat treatment. Gaseous ammonia penetrates rapidly into wood and is expected to form ammonium hydroxide when combined with water in the wood. This modification strategy neutralizes the acids produced by the degradation of hemicelluloses and reduces the degradation of the wood polymer composition and cell-wall structure. The preservation of wood polymer composition and cell-wall structure increases the indentation modulus of the wood cell walls. This increases the strength of the wood cell walls, resulting in an improvement in the mechanical properties of the heat-treated wood. The heat-treated wood’s dimensional stability and equilibrium moisture content are only slightly affected by the weak alkalinity modification.

Wood as a hydrothermally stimulated shape-memory material: mechanisms of shape-memory effect and molecular assembly structure networks

Abstract This study aimed to evaluate the shape-memory effect (SME) of wood (Populus x beijingensis W. Y. Hsu) and identify the net-points and switches in its molecular and morphological structures. During several cycles of deformation and subsequent recovery, a high shape recovery rate and ratio were maintained. The transverse compression tests of wet and dry wood reveal that the hydrothermal coupling stimulation can considerably reduce the strength of wood. The X-ray diffraction characterization of wood under hydrothermal stimulation shows that the role of network nodes in the SME of wood is influenced by temperature. The wavenumber shifting and changes in the intensity ratio of the characteristic Fourier transform infrared peaks showed that hydrogen bonds acted as switches for the water-stimulated shape-memory behavior. By taking into account viscoelastic relaxation, a kinetic model derived from nonequilibrium thermodynamic fluctuation theory was used to describe the shape recovery process. The effects of hydration on recovery kinetics, activation, and dynamic mechanical behaviors were also studied. To explain the shape-memory mechanism of wood under hydrothermal stimulation, a hybrid-structure network model based on a single three-dimensional switch network was proposed in this study.

Effect of Seawater with Average Salinity on the Moisture Content, Ash Content and Tensile Strength of Some Coniferous Wood.

In this paper, the differences in mechanical strength tested during the static tensile and compression test of Scots pine (Pinus sylvestris L.), European larch (Larix decidua) and Norway spruce (Picea abies) wood exposed to continuous soaking in water with a salinity of 7‱ were determined. The value of salinity corresponded to the average salinity on the Polish Baltic coast. This paper also aimed to examine the content of mineral compounds absorbed during four cycles of two weeks each. The essence of the statistical research was to identify the effect of the mineral range compounds and salts depending on the mechanical strength of the wood. Based on the results of the experiments, it can be concluded that the medium used has a specific effect on the wood species' structure. The effects of soaking on the wood parameters depend obviously on the type of wood. A tensile strength test of pine, as well as the tensile strength other species, was enhanced by incubating it in seawater. A native sample's initial mean tensile strength was 82.5 MPa, which increased to 94.8 MPa in the last cycle. It was found that the larch wood had the lowest tensile strength difference (9 MPa) of the woods studied in the current study. Four to six weeks of soaking was necessary to notice an increase in tensile strength.