Compression Strength Parallel Research Articles

Biodegradation and Micro- Scale Treatability Pattern of Loblolly Pine Heartwood Bioincised by Bacillus Subtilis and Physisporinus Vitreus

One strategy for improving the treatability of refractory wood species is biological incising, and its efficiency depends on how the microorganisms modify the porous structure of the wood. Evaluation of the bioincised wood treatability on a micro-scale can thus help to better understand the treatability enhancing mechanisms. In the present study, the biodegradation pattern and micro-scale treatability of Loblolly pine (Pinus taeda L.) heartwood were determined after bioincising with the white-rot fungus Physisporinus vitreus (Pers.: Fr.) P. Karsten isolate 136 and bacterium Bacillus subtilis UTB22. Oven-dried specimens with dimensions of 50 mm × 25 mm × 15 mm (L × T × R) were incubated with the microorganisms at (23±2) °C and (65±5) % relative humidity for six weeks. The control and exposed wood blocks were then pressure treated by 1 % fluorescent dye (fluorescein)-containing water to study the treatability pattern under a fluorescence microscope. The longitudinal and tangential air permeability and compression strength parallel to the grain of the specimens were also determined at the end of the incubation period. Scanning electron microscopic (SEM) studies showed that degradation by B. subtilis UTB22 was limited to the pit membranes, but the cell walls were also degraded to some extent by P. vitreus. The fungus caused a higher mass loss compared to the bacterium, whereas the permeability enhancing ability of the bacterium was more pronounced. The fluorescent dye tracer also showed that higher treatability with more uniformity was obtained by B. subtilis UTB22. The improvement in treatability by both microorganisms was mainly due to the degradation of the earlywood tracheids.

Effect of Glue Spreads on the Structural Properties of Laminated Veneer Lumber from Spindleless Rotary Veneers Recovered from Short Rotation Hevea Plantation Logs.

Unproductive young rubber trees (15 years old) with smaller diameters (15 to 18 cm) compared to conventional rubber logs, harvested at the age of 25 years old, were selected for the production of laminated panels. Spindleless rotary veneer peeling was applied to logs from short-rotation rubber forest plantations to produce veneers for structural purposes. This raises questions about the utilization of these small-diameter logs with respect to its effect on the quality of veneer and laminated panels produced. This study examines the effect of the glue spread rates on the physical and mechanical properties of rubberwood laminated veneer lumber (LVL). Analysis of variance shows that the application of a 280 g/m2 glue spread rate significantly improved the density, water absorption and dimensional stability of rubberwood LVL. The mechanical properties of rubberwood LVL produced with a 200 g/m2 glue spread rate met the minimum requirement for the 2.1E-3100F stress class; 91.05 MPa for the modulus of rupture in the flatwise direction and 50.23 MPa for compressive strength parallel to the longitudinal axis. The modulus of elasticity in the flatwise direction of 11,189.55 MPa reached the minimum requirement for the 1.5E-2250F stress class.

Modeling of radial variations of wood properties in naturally regenerated trees of Betula platyphylla grown in Selenge, Mongolia

Wood properties, such as annual ring width, wood fiber length, vessel element length, basic density, air-dry density, dynamic Young’s modulus, modulus of elasticity (MOE), modulus of rupture (MOR), absorbed energy in impact bending, compressive strength parallel to grain, and shearing strength, were investigated for wood from 10 naturally regenerated trees of Betula platyphylla Sukaczev in Mandal, Selenge, Mongolia. Mixed-effects models were used to evaluate the radial variations in the wood properties. The mean values of wood properties obtained in the present study were in almost the same range, with a few exceptions, as those reported by other researchers for other Betula species. The radial variations of wood properties in B. platyphylla were well-fitted to a nonlinear mixed-effects model (logarithmic formula); all examined wood properties increased from the pith and then became constant toward the bark side. The wood properties significantly differed between the core and outer wood. Basic density, air-dry density, and dynamic Young’s modulus were significantly correlated with MOE, MOR, and compressive strength. It is concluded that when the wood of B. platyphylla is utilized as raw materials for solid wood products, the differences between the core wood and outer wood should be considered. In addition, the selection of wood with higher strength properties can be achieved using the wood density and dynamic Young’s modulus as indicators.

Comparative studies on the mechanical properties and microstructures of outerwood and corewood in Pinus radiata D. Don

Twenty-year-old Pinus radiata trees imported from New Zealand were investigated, and a comparison was made between the outerwood (rings 16–20) and corewood (rings 4–6) in terms of mechanical properties, anatomical characteristics, microfibril angle (MFA), relative crystallinity, crystallite size and lignin content to determine the relationship between their mechanical properties and microstructures. The results demonstrated that the mechanical properties of the Pinus radiata outerwood were significantly better than those of the corewood. The outerwood had a modulus of rupture (MOR) of 106 MPa, a modulus of elasticity (MOE) of 11.4 GPa, and compressive strength parallel to the grain of 38.7 MPa, and the MOR, MOE and compressive strength parallel to the grain of the corewood were 78.9 MPa, 7.12 GPa and 29.3 MPa, respectively. The observed microstructures of the Pinus radiata outerwood and corewood were different, mainly due to differences in cell wall thickness, MFA, and relative crystallinity. The double wall thickness of the tracheid cells of the corewood and outerwood were 3.65 and 5.02 µm, respectively. The MFA data indicated that the average MFA of the outerwood was 14.0°, which was smaller than that of the corewood (22.3°). With X-ray diffraction, the relative crystallinity of the corewood was determined to be 35.7%, while that of the outerwood was 40.2%. However, the crystallite size of the outerwood cell wall shows no obvious difference from that of the corewood. Imaging FTIR spectroscopy showed a slightly higher relative content of lignin in the cell wall of the outerwood. The correlation between the microstructures and mechanical properties showed that the corewood with a thin cell wall, large MFA and low relative crystallinity had poor mechanical properties, while the outerwood with a thicker tracheid, smaller MFA and higher relative crystallinity had better mechanical properties. This means that the MFA, relative crystallinity and cell wall thickness synergically affect the mechanical properties of Pinus radiata in different radial locations.

Vermiculite Filler Modified with Casein, Chitosan, and Potato Protein as a Flame Retardant for Polyurethane Foams.

In this study, polyurethane (PU) composite foams were modified with 2 wt.% of vermiculite fillers, which were themselves modified with casein, chitosan, and potato protein. The impact of the fillers on selected properties of the obtained composites, including their rheological (foaming behavior, dynamic viscosity), thermal (temperature of thermal decomposition stages), flame-retardant (e.g., limiting oxygen index, ignition time, heat peak release), and mechanical properties (toughness, compressive strength (parallel and perpendicular), flexural strength) were investigated. Among all the modified polyurethane composites, the greatest improvement was noticed in the PU foams filled with vermiculite modified with casein and chitosan. For example, after the addition of modified vermiculite fillers, the foams’ compressive strength was enhanced by ~6–18%, their flexural strength by ~2–10%, and their toughness by ~1–5%. Most importantly, the polyurethane composites filled with vermiculite filler and modified vermiculite fillers exhibited improved flame resistance characteristics (the value of total smoke release was reduced by ~34%, the value of peak heat release was reduced by ~25%).

Prediction of Mechanical Properties of Hardwood Species Using the Longitudinal Vibration Acoustic Method

Abstract Acoustic test methods such as longitudinal vibration have been developed to predict the elastic properties of wood. However, attention has not been shifted to using this method to predict other mechanical properties, especially on Nigeria's preferred, and lesser-used wood species. Thus, we further investigate relationships among mechanical and acoustic properties of selected hardwood species with a view of predicting the mechanical properties of wood from acoustic parameters. Clear wood samples (324) of 20 by 20 by 20 mm3 were collected axially from Albizia adianthifolia, Gmelina arborea, Delonix regia, and Boscia anguistifolia trees, and conditioned before testing. The longitudinal vibration method was adopted to test for the dynamic (acoustic) parameters and properties (fundamental frequency, damping factor, dynamic modulus of elasticity, sound velocity, specific elastic modulus, radiation coefficient, acoustic conversion efficiency, acoustic impedance) while the universal testing machine was used to test for the mechanical properties (static modulus of elasticity, modulus of rupture, maximum compression strength parallel to grain). The damping factor, dynamic modulus of elasticity, and acoustic impedance were the best acoustic parameters that significantly correlated with the static modulus of elasticity (−0.57, 0.81, 0.76), modulus of rupture −0.64, 0.82, 0.85) and maximum compression strength parallel to grain (−0.52, 0.78, 0.84), respectively. There was a significant difference in the mechanical properties with respect to species, thus A. adianthifolia and G. arborea were mechanically better than D. regia and B. anguistifolia for construction or structural purposes. This study revealed that additional new acoustic measures are suitable for inferring mechanical wood properties.

Sifat fisik dan mekanik balok lamina dari batang kelapa sawit berdasarkan jumlah lapisan [ The physical and mechanical properties of laminated lumber from oil palm trunk based on the number of layers

The total area of oil palm plantations in 2019 is 14.2 million hectares. Every 25 years, there is always oil palm plantations replanting that produced oil palm trunks. The potential of oil palm trunks used as raw material for laminated lumber is about 52.5% of the total of oil palm biomass. Oil palm trunks have a very low density, so that it needs special processing before it could be applied as building material or other uses. The purpose of this study is to analyze the physical and mechanical properties of laminated lumber from oil palm trunks at the end position based on the number of layers. The method used in this research was the utilization of oil palm trunks lamination using PVAc (polyvinyl acetate) adhesive with variations of 1, 2, 3, and 4 layers. The results showed that oil palm trunks could be used as raw material for laminated lumber. The characteristics of laminated lumber made from 1, 2, 3, and 4 layers range between: moisture content (12.16 – 13.6) %, density (1.281 – 0.331) g/cm 3 , MoR (65.46 – 116.54) kg/cm 2 , and compressive strength parallel to its fibers (43.31 – 114,66) kg/cm 2 . The physical properties of the oil palm trunks laminated lumber with the increasing number of layers tends to increase the density and reduce the moisture content, rather than oil palm trunks laminated lumber with a smaller number of layers. The increasing number of oil palm trunks layers lamination increase the value of laminated lumber mechanical properties.

Evaluation of the Performance of Bio-Based Rigid Polyurethane Foam with High Amounts of Sunflower Press Cake Particles.

In the current study, rigid polyurethane foam (PUR) was modified with 10–30 wt.% sunflower press cake (SFP) filler, and its effect on performance characteristics—i.e., rheology, characteristic foaming times, apparent density, thermal conductivity, compressive strength parallel and perpendicular to the foaming directions, tensile strength, and short-term water absorption by partial immersion—was evaluated. Microstructural and statistical analyses were implemented as well. During the study, it was determined that 10–20 wt.% SFP filler showed the greatest positive impact. For instance, the thermal conductivity value improved by 9% and 17%, respectively, while mechanical performance, i.e., compressive strength, increased by 11% and 28% in the perpendicular direction and by 43% and 67% in the parallel direction. Moreover, tensile strength showed 49% and 61% increments, respectively, at 10 wt.% and 20 wt.% SFP filler. Most importantly, SFP filler-modified PUR foams were characterised by two times lower water absorption values and improved microstructures with a reduced average cell size and increased content in closed cells.

Vacuum-Based Impregnation of Liquid Glass into Sunflower Press Cake Particles and Their Use in Bio-Based Rigid Polyurethane Foam.

The study analyses rigid polyurethane (PUR) foam modified with 10–30 wt.% sunflower press cake (SFP) and liquid glass-impregnated sunflower press cake (LG-SFP) particles and their impact on performance characteristics of PUR foams—foaming behaviour, rheology, thermal conductivity, compressive strength parallel and perpendicular to the foaming directions, tensile strength, dimensional stability, short-term water absorption by partial immersion, and thermal stability. Even though the dynamic viscosity and apparent density were increased for SFP and LG-SFP formulations, thermal conductivity values improved by 17% and 10%, respectively, when 30 wt.% of particles were incorporated. The addition of SFP and LG-SFP particles resulted in the formation of more structurally and dimensionally stable PUR foams with a smaller average cell size and a greater content of closed cells. At 30 wt.% of SFP and LG-SFP particles, compressive strength increased by 114% and 46% in the perpendicular direction, respectively, and by 71% and 67% in the parallel direction, respectively, while tensile strength showed an 89% and 85% higher performance at 30 wt.% SFP and LG-SFP particles loading. Furthermore, short-term water absorption for all SFP and LG-SFP modified PUR foam formulations was almost two times lower compared to the control foam. SFP particles reduced the thermal stability of modified PUR foams, but LG-SFP particles shifted the thermal decomposition temperatures towards higher ones.

Effects of impregnation and heat treatment on density, bending and compression properties of black pine (Pinus nigra Arnold) wood

ABSTRACT This study aims to study the improvement in the properties of heat-treated wood material by impregnation. For this purpose, black pine (Pinus nigra Arnold) wood specimens were modified in two stages: impregnation with 1%, 3% and 5% of diammonium phosphate (DAP) and sodium carbonate (SC) compounds followed by heat treatment at four different temperatures. Test specimens were pre-treated with solutions of different pH values of either DAP or SC solutions according to the immersion method and they were exposed to heat treatments at 150°C, 170°C, 190°C and 210°C for 3 h. Some physical and mechanical properties were determined in combined treated specimens with air-dried density, compression strength parallel to grain (CS) and bending strength (MOR). The test results indicated that, as regards the effect of the heat treatment, the mechanical strength decreased due to the increase in temperature, while the losses in the CS were fewer than those of the MOR. In addition, generally combined treatments increased the mechanical properties of the specimens, especially at lower and moderate heat treatment temperatures. Moreover, the SC compound showed more favorable results against the reducing effect of the heat treatment on mechanical strengths.

Assessing the density and mechanical properties of ancient timber members based on the active infrared thermography

The objective of this study was to assess the density and mechanical properties of ancient timber members based on the active infrared thermography (IRT). Based on the unsteady heat transfer theory, the cooling constant (Ve) was proposed and the relationship between Ve and density as well as the mechanical properties of timber was analyzed. The cooling tests were conducted on 50 small clear specimens of ancient timber members to obtain the Ve and the cooling law of specimens. In addition, the effect of heating on the dynamic modulus of elasticity (Eus) and color of ancient timber members was investigated. At the same time, static mechanical tests and density measurement test were carried out to analyze the relationship between Ve and density as well as mechanical properties. The results indicated that there was unobservable influence on Eus and color parameters (L*, a* and b*) of specimens with its heating process in evaluation of the density and mechanical properties based on active IRT. Meanwhile, the initial excess temperature θ0 and initial temperature T0 had no influence on the cooling constant Ve as well as the relationship between τ and θ in the cooling process of specimens. Moreover, Ve had a strong negative correlation with density, modulus of elasticity (MOE), modulus of rigidity (MOR) and compressive strength parallel to grain (CSPG) of specimens (R2 = 0.9768, 0.8493, 0.8714 and 0.8865). In addition, the validation test result show that there is satisfactory predictive ability for density, MOE, MOR and CSPG of ancient timber members based on the prediction models established.

Compressive strength parallel to grain of earlywood and latewood of yellow pine

The compressive strength parallel to grain of earlywood and latewood from the yellow pine sapwood and heartwood areas was examined in the study. The structure of the basic structural elements of wood - tracheids, which conduct water and/or perform the mechanical function - was also characterized. The compressive strength parallel to grain of latewood in the sapwood area was found to be twice as high as the compressive strength parallel to grain of earlywood. The compressive strength parallel to grain of latewood in the heartwood area, on the other hand, was found to be 2,5 times higher than the compressive strength parallel to grain of earlywood. This was due to the density of particular areas of wood and the dimensions of structural elements - tracheids. In the sapwood area, the density of latewood was ca. twice as high as the density of earlywood. Similar relationships were found for heartwood. The thickness of latewood tracheids was found to be 1,5 times greater than the thickness of earlywood tracheids. These relationships were observed in sapwood and heartwood. The diameter of earlywood tracheids in radial direction was twice as large as the diameter of latewood tracheids. These relationships were observed in yellow pine sapwood and heartwood

Effect of compression ratio and original wood density on pressing characteristics and physical and mechanical properties of thermally compressed coconut wood

This experimental study aims to improve the engineering properties of coconut wood by using a thermal compression method (TM). The effects of original wood density and compression ratio on the pressing characteristic as well as physical and mechanical properties of thermally densified coconut wood were evaluated. Coconut wood boards obtained from the plantation located in Nakhon Si Thammarat province, Thailand, were sorted into low-density (359 ± 36 kg/m3) and medium-density (532 ± 35 kg/m3) groups. They were compressed by 25%, 40%, 55%, and 70% of their original thicknesses under a clamping pressure of 19.6 MPa (pressure gauge), at a temperature of 140 °C for 15 min. The physical and mechanical properties of the densified specimens were measured and compared with the control group specimens. Low-density specimens could be compressed with a higher degree of densification without shape distortion. Thermal compression improved bending strength, modulus of elasticity, compressive strength parallel to grain, and perpendicular-to-grain shear strength up to 125%, 54%, 112%, and 129%, respectively, for low-density wood and 47%, 13%, 41%, and 58%, respectively, for medium density wood. However, the densification did not improve parallel-to-grain shear strength. When the low-density and medium-density wood were compressed to the same density, the densified specimens manufactured from the medium-density group showed more improved dimensional stability, shear strength, and bending properties than those manufactured from the low-density group, while their parallel-to-grain compressive strength properties were not significantly different. However, at the same density level, the natural wood mechanically outperformed the densified wood except for the perpendicular-to-grain shear strength, parallel-to-grain compressive strength, and bending strength perspectives. Thus, the experimental results indicate that the densified coconut wood can be used for structural applications where parallel-to-grain compressive strength or perpendicular-to-grain shear strength is critical.

A COMPARATIVE STUDY ON THE PHYSICAL AND MECHANICAL PROPERTIES OF DAHURIAN LARCH AND JAPANESE LARCH GROWN IN KOREA

To compare the wood quality of Dahurian larch and Japanese larch growing in Korea, the physical and mechanical properties were examined using the Korean standards. The proportion of heartwood was 82% and 72% in Dahurian and Japanese larch, respectively. The percentage of latewood was 42% in Dahurian larch and 35% in Japanese larch. The growth ring width of Dahurian larch was narrower than that of Japanese larch. Dahurian larch showed about 20% higher green moisture content compare to Japanese larch wood. Density and shrinkage of Dahurian larch were higher than Japanese larch. Axial compression strength, young`s modulus in compression, and shearing strength in heartwood of Dahurian larch were 11 MPa, 686 MPa, and 2.3 MPa, respectively, showing higher value than Japanese larch. The hardness was in the range of 13.8–38.7 MPa in Dahurian larch and 17.7–48.4 MPa in Japanese larch. The compression strength parallel to the grain and shearing strength in both species were significantly correlated with oven-dried density. Besides, the hardness in Dahurian larch was significantly correlated with latewood percentage and oven-dried density. In conclusion, the differences in the properties of both species were revealed and the results can be used for quality indices of both wood species.

Case Study of Anatomy, Physical and Mechanical Properties of the Sapwood and Heartwood of Random Tree Platycladus orientalis (L.) Franco from South-Eastern Poland

Oriental arborvitae is not fully characterized in terms of its microscopic structure or physical or mechanical properties. Moreover, there is a lot of contradictory information in the literature about oriental arborvitae, especially in terms of microscopic structure. Therefore, the sapwood (S) and heartwood (H) of Platycladus orientalis (L.) Franco from Central Europe were subjected to examinations. The presence of helical thickenings was found in earlywood tracheids (E). Latewood tracheids (L) were characterized by a similar thickness of radial and tangential walls and a similar diameter in the tangential direction in the sapwood and heartwood zones. In the case of earlywood tracheids, such a similarity was found only in the thickness of the tangential walls. The volume swelling (VS) of sapwood and heartwood after reaching maximum moisture content (MMC) was 12.8% (±0.5%) and 11.2% (±0.5%), respectively. The average velocity of ultrasonic waves along the fibers (υ) for a frequency of 40 kHz was about 6% lower in the heartwood zone than in the sapwood zone. The dynamic modulus of elasticity (MOED) was about 8% lower in the heartwood zone than in the sapwood zone. These differences, both in the case of υ and MOED, were statistically significant. However, no statistically significant differences were found for the static bending strength (MOR, approx. 90 MPa), modulus of elasticity at static bending (MOE, approx. 4800 MPa), or compression strength parallel to the grain (CS, approx. 47 MPa) in relation to the wood zone (sapwood, heartwood).

Compression and flexural properties of plantation-grown Eucalyptus pellita in Borneo, Malaysia. Potential for structural timber end use

ABSTRACT Plantation-grown Eucalyptus pellita in Sabah, Malaysia, was analysed for compression and flexural properties to assess the potential for solid-timber and engineered wood product end uses. It is necessary to consider not only the volume of wood produced in a plantation but also the wood quality, particularly those aspects important for end-product performance. Tree volume is readily measured from height and diameter at breast height using appropriate form factors. This paper discusses the compression, strength and stiffness of E. pellita compared with tropical hardwood species, and variation within trees and at different ages (7–23 years). Small clearwood test samples obtained from radial positions within log heights were subjected to analysis of compression parallel to grain and three-point bending according to ISO 13061-4, 2014. Results indicate that plantation-grown E. pellita in the tropics has potential for structural-use applications. The average basic density across the trials was 658 kg m−3, while the bending strength for all trials was in the range of 11.7–15.5 GPa for modulus of elasticity and 96.3−120.1 MPa for modulus of rupture, and the compression strength parallel to grain ranged from 52.3 to 67.8 MPa. Mean mechanical strength increased from pith to bark and from the butt log to the top log. Because the wood-processing sector in Malaysia is transitioning from reliance on a harvest of mixed tropical hardwood towards plantation-grown species, these results indicate that plantation-grown E. pellita meets the structural requirements of strength and stiffness.

Genetic Evaluation and Combined Selection for the Simultaneous Improvement of Growth and Wood Properties in Catalpa bungei Clones

Catalpa bungei is an important timber tree. Improvements in growth and wood quality are important goals of C. bungei breeding, and it is necessary to understand the genetic parameters of specific target traits and genetic correlation between growth traits and wood properties for tree breeding. In this study, the genetic parameters of height, diameter at breast height (DBH) and wood properties were estimated and genetic and phenotypic correlations between growth traits and wood properties were evaluated in C. bungei. Finally, different selection scenarios were used to evaluate and select optimal clones. The results showed that there were significant differences in growth and wood properties among clones. The wood hardness (0.66–0.79), basic density (0.89), air-dried density (0.89) and compression strength parallel to the grain of wood (CSP) (0.84) had high repeatability. The variance component proportions indicated that the variation in wood properties came mainly from different genotypes (clones) rather than from different individuals of the same clone. The DBH showed a significant negative genetic correlation with the hardness of radial section (HRS) (−643), basic density (−0.531) and air-dry density (−0.495). This unfavorable relationship makes it difficult to improve growth and wood quality simultaneously in C. bungei. We selected the optimal clones under different scenarios, and we obtained 7.75–9.06% genetic gains for growth in the scenario in which height and DBH were the target traits. Genetic gains of 7.43–14.94% were obtained for wood properties by selecting optimal clones in the scenario in which wood properties were the target traits. Approximately 5% and 4% genetic gains were obtained for growth and wood properties, respectively, for the combined selection. This study provides new insights into the genetic improvement of wood quality in C. bungei.

Modelling some physical and mechanical properties of heat-treated Scotch pine using artificial neural network

In this study, some physical and mechanical properties of yellow pine wood (Pinus sylvestris), which is used extensively in furniture industry, were tested after heat treatment. The findings obtained were modelled by artificial neural network (ANN) and interval values related to temperature and time variations were tried to be estimated. This study, which makes it easier to reach intermediate values, aims to save the relevant researchers from trial load all of the heating parameters during the furniture design/production stages. In the study scotch pine samples were heat-treated at 150, 160, 170, 180, 190 and 200 °C for 2, 4 and 6 hours, under normal atmosphere conditions. Color changes, weight losses and compression strength parallel to grain values of heat-treated samples were determined. After experimental study, modelling procedure was performed by ANN using two different learning algorithm- Levenberg-Marquardt (LM) and Scaled Conjugate Gradient (SCG) algorithm- 15 different hidden neurons. The best model was obtained from 2-7-6 structure using LM learning algorithm. Mean absolute percentage error (MAPE) of the best model was found below 8.0% for estimated color parameters. The weight loss and compression strength parallel to grain were 5.79% and 1.50%, respectively. It was concluded that ANN can be used successfully to predict all studied parameters of heat-treated wood samples.

Main mechanical properties of new Chinese fir clones and their rapid prediction by near-infrared spectroscopy

Owing to its rapidity and accuracy, near-infrared (NIR) spectroscopy is a powerful tool to establish appropriate prediction models with an innovative method to evaluate wood properties. To reveal the mechanical qualities of clonal Chinese fir woods and to determine sound prediction models of mechanical properties, four main mechanical properties of six Chinese fir clones (Yang 020, Yang 061, Kaihua 3, Kaihua 13, Daba 8, Kailin 24) were evaluated by NIR spectroscopy. The clones Kaihua 13, Kailin 24, and Yang 020 showed good mechanical properties. To estimate mechanical properties with NIR spectroscopy, different methods should be adopted for different properties. The average spectra of radial and tangential sections combined with multiple scattering correction (MSC) and Savitzky–Golay (S–G) smoothing methods were used to predict the modulus of rupture and modulus of elasticity. By adopting cross section spectra and taking MSC and S–G smoothing methods for pretreatment, the models of compressive strength parallel to grain could deliver the best results. For wood hardness, the models established with average spectra of three sections and first-derivative method were preferred. The correlation coefficients of the prediction models were between 0.84 and 0.90, and those of the calibration models were between 0.75 and 0.96.

Experimental study on partial compression parallel to grain of solid timber

This paper describes results and analysis of experimental testing of entire and partial compression strength and stiffness parallel to the grain of solid timber (Japanese cedar). To investigate the spreading effects, the size effect of strength and stiffness, and the mechanism of the damage zone located close to the loading plates, tests on 90 specimens were performed. As a result, it was observed that damage zones existed near the loading plates. The observed spreading effects in the compression parallel to the grain were very small which justifies neglecting them regarding strength and stiffness. Although a presence of a size effect of the compression strength parallel to the grain of glulam specimens with knots was reported, the compression strength parallel to the grain of solid wood specimens without knots does not have a size effect. The height and width of the cross-section of the specimens have an influence on the damage zones and, hence, on the effective modulus of elasticity of the full height of the specimens. The compression strength has a correlation with the density of the timber and the width of the annual rings.