Chinese Fir Wood Research Articles

Comparison analysis of moisture-dependent orthotropic elasticity between earlywood and latewood in Chinese fir using digital image correlation

Given its orthotropic and hygroscopic nature, Chinese fir exhibits varying mechanical behaviors in earlywood and latewood due to its naturally inhomogeneous structure when exposed to changes in loading direction and given moisture content (MC) range from 7.9 % to 16.1 %. In this study, we combined micro-tensile testing and the digital image correlation (DIC) technique to derive the moisture -dependent orthotropic elastic constants, i.e., Young’s modulus (E), Poisson’s ratio (ν) and shear modulus (G) for both earlywood and latewood in Chinese fir. The findings revealed that when loading in the parallel direction, the restraining effect caused by latewood on earlywood resulted in a difference compared with loading in series. Interestingly, the loading direction impacted the restraining effect more significantly than MC. Additionally, both Young’s modulus and shear modulus exhibited decreases with increasing MC within above range for both earlywood and latewood. Notably, the Young’s modulus of earlywood showed a higher sensitivity to MC variations compared to latewood. However, Poisson’s ratio did not consistently correlate with MC within above range in all orthotropic directions. A three-dimensional coordinate system visualization of the compliance parameters highlighted the differing sensitivities of earlywood and latewood to moisture. The independent moisture-dependent elastic components of earlywood and latewood derived in this study extended the moisture-dependent mechanical model of wood, offering theoretical guidance for the practical application of Chinese fir and other wood species.

Gluing parameters optimization and failure mechanism of cross-laminated timber prepared with Chinese fir

Cross-laminated timber (CLT) has become a popular engineered wood product, mainly prepared from imported wood in China. More extensive research is needed to improve the local production of cross-laminated timber with fast-growing coniferous wood species. Chinese fir (Cunninghamia lanceolata) and one component polyurethane (1C-PUR) adhesive were selected to prepare CLT under different process parameters. International standard methods, scanning electron microscopy (SEM), optical microscopy (LM), confocal laser scanning microscopy (CLSM), and nanoindentation (NI) were applied. The bonding performance and failure mechanism of Chinese fir CLT were investigated and clarified. The results showed that the optimal gluing parameters for preparing CLT from Chinese fir wood were 160 g/m2 of glue, 0.9 MPa of pressure, and 180 minutes of pressing time. Failure of CLT made from Chinese fir lumber was mainly due to the shear failure of the vertical layer board. Cracks often appeared in the earlywood cells near the boundary between earlywood and latewood. The impact of adhesive penetration on the mechanical properties of the wood cell wall showed that adhesive penetration increased the elastic modulus of the cell wall at earlywood and latewood cells.

Enhancing heat modification efficiency of Chinese fir wood through fly ash impregnation: A comprehensive evaluation using time-temperature superposition and cluster analysis

Catalytic degradation via fly ash impregnation (Im) has proven effective in reducing the heat modification (HM) temperature required for wood. To accurately gauge the intensity of HM on wood following Im, the physiomechanical properties of Im-HM treated wood were investigated across various treatment conditions (temperature: 80–140°C, duration: 1–4 h, and fly ash concentration: 2–8%), and compared them to conventional HM (CoHM) wood. Two mathematical methods (time-temperature superposition and cluster analysis) were employed to elucidate the relationships between treatment conditions and resulting properties. Results indicated that Im-HM treated wood exhibited comparable dimensional stability and visual appearance to CoHM wood, while retaining superior mechanical properties. The acid-catalyzed effect of Im-HM demonstrated significant dependence on treatment temperature, duration, and concentration, providing an avenue to regulate catalytic intensity. Employing the time-temperature superposition principle, master curves for weight percentage loss (WPL), modulus of elasticity (MOE) and anti-swelling efficiency (ASE) were constructed under a reference condition (80°C and 2% concentration), covering processing duration up to 20 hours. These master curves facilitated understanding the relationship between temperature, duration and concentration when evaluating catalytic intensity. Cluster analysis, based on the physiomechanical properties of Im-HM and CoHM wood, offered a clear interpretation of HM intensity. Notably, Im-HM treatment at 140°C for 4 hours with an 8% concentration exhibited HM intensity similar to CoHM treatment at 200°C. Through the integration of time-temperature superposition and cluster analysis, this study assesses Im-HM intensity, providing a valuable reference for the industrial application of Im-HM treatment.

Effect of grain orientation on the energy absorption performance of Chinese fir wood under quasi-static compression

ABSTRACT The compressive response and energy absorption of Chinese fir wood with different grain orientations along the longitudinal (L) and radial (or tangential) directions were studied through uniaxial quasi-static compression tests. The results indicated that the wood compressive behavior changed from out-of-plane to in-plane, similar to honeycomb materials when the grain orientation was changed from longitudinal to transverse. The initial peak stress (σp ) and plateau stress (σpl ) decreased upon increasing the grain angle (θ), especially below 45°, and more slowly above 45°. The wood compressive failure modes and energy absorption ability were also strongly dependent on the grain orientation, and the energy absorption per unit volume and energy absorption efficiency decreased as θ increased. Energy absorption diagrams and mathematical models were established to evaluate the optimum energy absorption point to guide the selection of energy-absorbing wood.

Research on the hot densification mechanism of biomass wastes based on molecular dynamics simulation and components adjustment method

The hot densification process can be used to prepare the biofuel pellets and diversified densification materials with suitable mechanical strength to overcome the natural defects of low energy density and loose structure of biomass wastes and achieve the high value utilization of the renewable resources. In this study, the two typical biomass wastes, cotton stalk (CS) and Chinese fir wood sawdust (WS) are used for the hot densification investigation (85 °C), and the microscopic evolution behavior of the biomass components during the hot densification process is explored through the combination of the component adjustment method and molecular dynamics simulation. The results show that cellulose is the key component to the mechanical strength of biomass pellet, which plays the crucial role of skeleton support in the densification process, and the strength of pellet is positively correlated with the increasing addition ratio of cellulose. Furthermore, crystalline cellulose exhibits the strongest bonding properties in the hot densification process due to the formation of rich hydrogen bonds and the increasing intermolecular attraction force. Lignin has the poorest capability for hydrogen bond formation, and its addition increases the van der Waals repulsive forces, resulting in the poorest densification performance. Hemicellulose shows the better adhesion capability than lignin due to its glassy transition (83.34 °C) and the suitable addition can greatly improve the mechanical property of the pellet, up to 14.26 MPa. There exists the strongest synergistic effect between cellulose and hemicellulose, which is beneficial to the bonding performance between particles to different extent. Hot densification process can promote the formation of hydrogen bond connections between molecules/atoms and the increase of the van der Waals repulsive force in the further compression. The densification performance of biomass is the combined effect of the physical forces, including electrostatic force and van der Waals force.

Investigation into the Performance Enhancement of Calcium Phosphate Mineralization-Compacted Chinese Fir

The utilization of wood as a construction material offers inherent advantages, including its renewability, good process property, wide availability, and carbon sequestration. However, its susceptibility to combustion and limited mechanical properties also constrain its applications. In this work, calcium phosphate was in situ deposited in dignified Chinese fir wood, followed by hot-pressed densification. Thermogravimetric analysis (TG) reveals that mineralization and densification alleviate the thermal decomposition and combustion behavior of wood, which greatly promotes the formation of the dense char layer during wood combustion. Therefore, the maximum heat release rate (HRR), total heat release rate (THR), and total smoke production rate (TSP) of the as-prepared mineralized dense wood were significantly reduced by 37%, 32%, and 56% compared with the control one. Further, the mineralized dense wood showed a remarkable enhancement in flexural strength and flexural modulus of elasticity, 203% and 220% higher than the natural wood, respectively. This study demonstrated a straightforward and eco-friendly approach to fabricating structural wood possessing exceptional flame retardancy and mechanical characterization, which holds immense potential for application in energy-efficient green buildings.

Effect of temperature on the dynamic wettability of Chinese fir wood: integrative consideration of surface spreading, penetration and evaporation

Abstract Wood wettability, the process of liquid interaction with wood surfaces, is influenced by wood surface chemistry, structure, ambient conditions, and temperature. Understanding how temperature impacts wood wettability is crucial for high-temperature manufacturing processes. In this study, the sessile drop method was employed to explore the dynamic wettability of Chinese fir wood using three different liquids (water, glycerol and polyvinyl acetate (PVAc)) across a range of temperatures (25, 40, 60 and 80 °C). By considering spreading, penetration and evaporation, we revealed that the dynamic wettability of Chinese fir was strongly dependent on temperature and the type of liquid. Temperature elevation enhances wettability, leading to reduced contact angles and increased penetration ratios. Water exhibited the highest wettability, followed by glycerol, with PVAc being the least wetting agent. Notably, after 180 s of wetting at 80 °C, the measured contact angles were 0° for water, 45° for glycerol, and 120° for PVAc. When accounting for evaporation, the penetration of water decreased from 57 % to 47 % (25 °C) and 100 % to 62 % (80 °C). The activation energies for the penetration of water and PVAc into Chinese fir exhibited variations, with values of 35.3 and 158.3 kJ/mol, respectively. These comprehensive wetting results, covering spreading, penetration and evaporation, provide valuable insights into wood–water and wood–adhesive interactions, particularly when exposed to high-temperature conditions.

Effects of tannin acid impregnated pretreatment on dimensional stability and chemical composition of heat-treated Chinese fir

Abstract Thermal treatment is an effective method for improving the dimensional stability of wood; however, it typically requires high temperatures. To achieve low-temperature heat treatment, this study employed wood samples impregnated with 10 % tannin acid (TA) and examined their changes in dimensional stability and chemical components after heat treatment at various initial moisture content levels. The results revealed that the TA-10 %-HT group exhibited enhanced dimensional stability. Specifically, both the tangential and radial moisture swelling decreased by 21.7 % and 11.8 %, respectively. FTIR and XRD analysis indicated that the presence of tannin acid catalytically facilitated the degradation of hemicellulose. Moreover, an increase in moisture content resulted in the ionization of TA, amplifying acidity and further affecting cellulose degradation. TGA demonstrated that TA impacted the thermal stability of heat-treated materials by lowering the initial decomposition temperature of wood components and increasing the residual weight of wood. Overall, pretreatment with TA impregnation and moisture content significantly improved the dimensional stability of Chinese fir wood and altered its chemical composition. This approach holds considerable potential for enhancing wood properties through a low-energy consumption method during the heat treatment process, expanding the practical application of wood.

Inorganic-accelerated aging method: An efficient and simple strategy to obtain antique Chinese fir wood for the restoration of ancient wooden architecture

Ancient wooden architectures, the precious material cultural heritages of mankind, were faced with huge potential safety hazards because of the excessive aging and natural disaster. Replacing failed wood structure with antique wood is a proper and sustainable method for the repairment and reinforcement, however restricted by the lack of antique wood and mature wood antique technology. In this work, an inorganic-accelerated aging method was put forward to simulate the aging of Chinese fir wood. The as prepared antique wood exhibited a very similar surface color to that of the ancient wood, with a small chromatic aberration of only 4.4. The change of chemical compositions after inorganic-accelerated aging was also explored that hemicellulose was degraded greatly accompanied by the partly degradation of lignin and amorphous cellulose, which were similar to the nature aging process and resulted in an increase of wood crystallinity. Besides the as obtained a-W exhibited satisfactory mechanical strength, of which the bending modulus, static bending strength and compressive strength was 97.7 %, 93.4 % and 93.6 % of the ancient wood, respectively. This work provides a promising strategy for the preparing of antique wood, which is of great significance for the restoration of ancient wood architectures.

Infusing phytate-based biomass flame retardants into the cellulose lumens of Chinese fir wood attains superior flame retardant efficacy

To be suitable for certain construction and furniture applications, wood must be treated with a flame retardant and impregnating flame retardants into the cellulose lumens of wood is an effective flame retardant method. Phytic acid, the main storage form of phosphorus in various plant tissues, is an inexpensive, and non-toxic biomaterial that shows potential applications as an environmentally friendly bio-based flame retardant. In this study, phytic acid and zinc phytate were used to impregnate delignified wood under vacuum and pressure, which greatly enhanced the flame retardancy and smoke suppression properties of Chinese fir, while still maintaining its original texture. Phytic acid and zinc phytate were hydrogen-bonded to cellulose in wood. Phytic acid and zinc phytate were hydrogen-bonded to cellulose in wood. The results showed that the total heat release (THR) of Chinese fir treated with zinc phytate decreased from 55.66 MJ/m2 to 5.90 MJ/m2, and a compact carbonized protective layer was quickly formed on the surface of Chinese fir after ignition. Thermogravimetric analysis (TGA) showed that the char yield of Chinese fir treated by the flame retardant was 177.6 % higher than that of untreated wood. This study provides an efficient, sustainable, and economical method to prepare Chinese fir with excellent flame retardancy and thermal insulation performance.

Heat Modification of Chinese Fir Wood Catalyzed by Fly Ash under Mild Temperature

Heat Modification of Chinese Fir Wood Catalyzed by Fly Ash under Mild Temperature

Leachability of Fast-Growing Wood Impregnated with Low Concentrations of Furfuryl Alcohol

Furfurylation can effectively improve the quality of fast-growing wood, but its leachability is unclear. In this study, fast-growing poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) were impregnated with low concentrations of 5%–20% furfuryl alcohol (FA), and the chemical and microscopic changes during leaching tests were analyzed by UV spectra and confocal laser scanning microscopy (CLSM). The results show that FA impregnation can regulate the weight percentage gain, but its effectiveness in regulating the cell wall bulking coefficient decreased as the impregnation concentration was increased. Impregnation with 15% and 20% FA showed no significant difference in the effect on volume swelling efficiency. The inverse relationship between the concentration of FA and the leaching rate was demonstrated by leaching tests, UV spectra, and CLSM. Notably, the leaching rate of poplar and Chinese fir wood was more than 30% when impregnated with 5% FA. Although the entirety of the furfuryl alcohol was deposited in the cell wall when impregnated with low concentrations of FA, the binding was not stable. The weight percentage gain of furfurylated Chinese fir was greater than that of poplar, but its leaching rate was lower, indicating that the cured furfuryl alcohol resin in poplar was not as stable as that in Chinese fir. Therefore, differences in tree species should be considered in low-concentration FA impregnation, as the improvement effect of concentrations below 10% on the properties of fast-growing wood is weak and the leaching rate of FA is significant.

An Algorithm Based on DAF-Net++ Model for Wood Annual Rings Segmentation

The semantic segmentation of annual rings is a research topic of interest in wood chronology. To solve the problem of wood annual rings being difficult to segment in dense areas and being greatly affected by defects such as cracks and wormholes, this paper builds a DAF-Net++ model which is based on U-Net whose backbone network is VGG16 and filled with dense jump links, CBAM and DCAM. In this model, VGG16 is used to enhance the extraction ability of image features, dense jump links are used to fuse semantic information of different levels, DCAM provides weighting guidance for shallow features, and CBAM solves the loss of down-sampling information. Taking a Chinese fir wood as the experimental object, 1700 CT images of wood transverse section were obtained by medical CT equipment and 120 of them were randomly selected as the dataset, which was expanded by cropping and rotation, among others. DAF-Net++ was used for training the model and segmentation of the annual rings, and finally the performance of the model was evaluated. The training method is freeze training followed by thaw training, and takes Focal Loss as the loss function, ReLU as the activation function, and Adam as the optimizer. The experimental results show that, in the segmentation of CT images of Chinese fir annual rings, the MIoU of DAF-Net++ is 93.67%, the MPA is 96.76%, the PA is 96.63%, and the Recall is 96.76%. Compared with other semantic segmentation models such as U-Net, U-Net++, DeepLabv3+, etc., DAF-Net++ has better segmentation performance.

Exploring the effect of lignin on the chemical structure and microstructure of Chinese fir wood by segmental delignification

Exploring the effect of lignin on the chemical structure and microstructure of Chinese fir wood by segmental delignification

High-voltage electric field-induced decreased absorption efficiency of phenol formaldehyde adhesive in different sections of Chinese fir wood

High-voltage electric field-induced decreased absorption efficiency of phenol formaldehyde adhesive in different sections of Chinese fir wood

Effect of Impregnation with Natural Shellac Polymer on the Mechanical Properties of Fast-Growing Chinese Fir.

Fast-growing Chinese fir wood has shortfalls such as loose structure and low strength because it grows faster than natural trees. Resin impregnation is a great way to increase the strength of fast-growing fir. However, the resin used for impregnation is a kind of urea-formaldehyde resin, phenolic formaldehyde resin, melamine formaldehyde resin, and the like, which introduce harmful substances such as formaldehyde or phenolic into the wood. In this paper, Chinese fir wood was impregnated with natural shellac polymer, and the effects of impregnation variables on the mechanical properties of the wood were examined. The increase in strength in compression perpendicular to grain (SCPG) of wood samples impregnated with 15% shellac solution achieved a maximum value of 39.01%, but the modulus of rupture (MOR) was slightly reduced. The effects of the impregnation pressure, time, and their interaction were investigated by the response surface method (RSM). ANOVA analysis revealed that the impregnation pressure and time and the interaction between the two seemed to have a significant effect on ∆SCPG. Based on the response face model, the corresponding optimal parameters obtained are 1.0 MPa and 16.0 min for impregnation pressure and time, respectively. By impregnating fir wood with the above optimal conditions, the SCPG increased by 85.78%, whereas the MOR decreased by the least amount.

EVALUATION OF THE DECAY LEVELS OF WOODEN COMPONENTS IN ARCADE BUILDINGS IN THE ANCIENT TOWN CHIKAN VIA POLARIZED LIGHT, FLUORESCENCE AND FTIR SPECTRA

In order to classify the decay levels of Chinese fir (Cunninghamia lanceolata) wood components in arcade buildings in the ancient town Chikan and to provide basic data for future protection measures, the extent of decay of the samples was determined via polarized light, fluorescence, and Fourier-transform infrared spectroscopy. The results were as follows: (1)Thetotal birefringence brightness of crystalline cellulose and the green fluorescence brightness of the lignins were reducedto different degreesin almost all samples. (2)Theabsorption peaks at 1731 cm-1representing hemicellulose and at 891 cm-1representing cellulose in all samples disappeared. The absorption peak heights at 1370 cm-1, 1159 cm-1and 1058 cm-1which represents holocellulose,and at 1508 cm-1, 1424 cm-1, and 1262 cm-1which represents lignin decreased to varying degrees. (3)From the analysis, the decay level of wooden components in arcade buildings was divided into three classes, i.e., Level I (severe decay), Level II (moderate decay), and Level III (mild decay).

Effect of Impregnation with a Low-Concentration Furfuryl Alcohol Aqueous Solution on Hygroscopic Properties of Chinese Fir and Poplar Wood

Furfurylation with a low concentration of furfuryl alcohol (FA) promotes the improvement of the properties and the effectiveness of FA on cell–wall action without darkening the furfurylated wood to the point that it affects its applications. In this paper, the effects of furfurylation on the hygroscopicity and water uptake dimensional stability of poplar (Populus sp.) and Chinese fir (Cunninghamia lanceolata) were analyzed. Meanwhile, the distribution of FA resin, the relationship between wood and water, the change in pore size distribution, and the weight percentage gain and cell wall bulking coefficient of wood were also investigated. The results were as follows: (1) A low concentration of FA could better enter the cell walls of the Chinese fir than the poplar, as FA resin was almost cured in the secondary walls, cell corners, and compound middle lamellae when a 10% concentration of FA was applied to the Chinese fir and poplar. When the FA concentration was increased to 30%, there were no significant increases in the amount of FA entering the cell walls and the amounts of FA cured in the cell lumen of the poplar were greater than those of the Chinese fir. Meanwhile, the modification of cell walls was more suitable in poplar than in Chinese fir. (2) The pointed ends of the pit chambers and the pit apertures (800–1000 nm) in the poplar and the small pores of the pit membranes and the pit apertures (1–6 μm) in the Chinese fir were partially deposited by the FA resin, which formed new pores in the size ranges of 80–600 nm and 15–100 nm, respectively. The porosity of the poplar was greater than that of the Chinese fir, and the bulk density of the poplar was less than that of the Chinese fir before and after modification. (3) Furfurylation with a low concentration of FA was able to better reduce the equilibrium moisture content, improve the anti-swelling efficiency, and enhance the dimensional stability of the poplar wood compared to the Chinese fir. Furfurylation effectively reduced water uptake due to the hydrophobic property of the FA resin. The water uptake of the Chinese fir increased by 17%–19% in second cyclic water soaking when treated with FA with various concentrations, which indicated the loss and leaching of FA resin during the test. Low-field NMR was used to demonstrate that the furfurylation not only reduced the amount of water but also affected the combination state of bound and free water with wood. Thus, furfurylation at a low concentration is a feasible method by which to extend applications of furfurylated wood.

Effect of hydrothermal and hydrothermal oxidation pretreatment on the physicochemical properties of biofuel pellet

The effects of hydrothermal pretreatment with and without H2O2 addition on the properties of the resulted biofuel pellets prepared from cotton stalk (CS) and Chinese fir wood sawdust (WS) were mainly studied in the paper. Based on the changes of three main components (hemicellulose, cellulose and lignin) of biomass during the pretreatment process, the relaxation density, compressive strength, heating values (HVs), and combustion characteristics of the resulted pellets were analyzed to evaluate the feasibility of the utilization as biofuel pellets. The results indicate that the hydrothermal pretreatments with and without H2O2 addition are beneficial to the quality of the resulted biofuel pellets. Particularly, the hydrothermal pretreatment with H2O2 addition, namely the hydrothermal oxidation pretreatment can significantly alleviate the pretreatment severity of the high-strength biofuel pellet preparation. H2O2 addition promotes the decomposition of hemicellulose and cellulose during the pretreatment. Compared with CS, WS is more sensitive to the pretreatment, especially hydrothermal oxidation pretreatment. The crystallinity index and the cellulose content of the biomass sample both increase firstly and then decrease with the increasing pretreatment temperature. In the study, the pretreatment temperature for the biofuel pellets with the best mechanical properties is 230 °C for the hydrothermal process and 200 °C for the hydrothermal oxidation process, respectively. The HVs of the resulted biofuel pellet increases with the increasing pretreatment intensity and the suitable pretreatment can improve the combustion characteristics of the resulted biomass. The mechanical properties of the pretreated biofuel pellets were positively correlated with the crystallinity and the content of the cellulose. HVs of WS pellets is higher than CS pellets, with the better mechanical properties. The cellulose is more favorable for the improvement of the combustion properties of the biomass sample than the hemicellulose and lignin. In addition, HVs and the compressive strength of all the biofuel pellets prepared from the pretreated biomasses meet the Sweden Standard (SS18 7120) and the Ministry of Agriculture of China standard (NY/T1878–2010), respectively.

Temperature and time dependence of orthotropic viscoelastic properties of moist wood determined in tensile mode

Temperature and time dependence of orthotropic viscoelastic properties for Chinese fir wood (Cunninghamia lanceolata) were investigated in tensile mode. The storage modulus (E′) and loss modulus (E″) of the longitudinal (L), radial (R) and tangential (T) specimens with adsorbed water were determined during temperature increasing period ranging from 30°C to 103°C and at a constant temperature of 103°C for 480 min. The desorption of adsorbed water provided space for the rearrangement of hydrogen bonds (RHB) within the polymer networks and caused mechano-sorptive (MS) effect. During the temperature increasing period, the MS effect increased first and following decreased for all specimens, except for the T specimens with 7.2% moisture content. In a constant temperature process, elevated stiffness and decreased damping were observed in all orthotropic directions, which suggested that the RHB effect was prominent than the dual effects of the MS and heating. Compared to the L specimens, the multi-effects of the heating, RHB and MS exerted more influence on the R and T specimens. Meanwhile, the unstable state within wood cell walls in the R and T specimens was more pronounced than that in the L specimens. Furthermore, the transverse specimens were affected by temperature to a higher degree than that of the L specimens.