Research

23 pages, 20084 KiB

Open AccessArticle

Analysis of Mechanical Behavior through Digital Image Correlation and Reliability of Pinus halepensis Mill.

by Alberto Villarino, Jorge López-Rebollo and Natividad Antón

Forests 2020, 11(11), 1232; https://doi.org/10.3390/f11111232 - 23 Nov 2020

Cited by 7 | Viewed by 2245

The mechanical behavior of test pieces extracted from two specimens of Pinus halepensis Mill., from the same geographical area and close to each other, was examined in this study. Using a methodology based on Digital Image Correlation (DIC) and implemented during compression strength [...] Read more.

The mechanical behavior of test pieces extracted from two specimens of Pinus halepensis Mill., from the same geographical area and close to each other, was examined in this study. Using a methodology based on Digital Image Correlation (DIC) and implemented during compression strength testing, the modulus of elasticity in compression parallel to the grain (MOE_c) was obtained. In addition, the value of compressive strength (MOR_c) was obtained for this type of wood. The research was complemented with a reliability study, determined using the Weibull modulus, from the MOR_c values. A microstructural and behavioral study of the most representative pieces after failure was also conducted to correlate breakage with the behavior of the pieces during the tests monitored by DIC, to link both studies. DIC was shown to be an ideal and low-cost technique for the determination of the studied properties, and obtained average values of MOE_c of 50.72 MPa and MOR_c of 9693 MPa. These values represent fundamental data for design and calculations of wooden structures. A reliability value of between 11 and 12 was obtained using the Weibull modulus for this type of wood. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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15 pages, 1534 KiB

Open AccessArticle

Geographic Variations of the Wood Density and Fiber Dimensions of the Persian Oak Wood

by Noorollah Nazari, Mohsen Bahmani, Saleh Kahyani, Miha Humar and Gerald Koch

Forests 2020, 11(9), 1003; https://doi.org/10.3390/f11091003 - 17 Sep 2020

Cited by 17 | Viewed by 2500

Abstract

Persian oak (Quercus brantii Lindl.) is a valuable native species in Iranian forests with very limited availability of data on its wood properties. The objective of the current study was to determine the influence of altitude and slope on physical properties and [...] Read more.

Persian oak (Quercus brantii Lindl.) is a valuable native species in Iranian forests with very limited availability of data on its wood properties. The objective of the current study was to determine the influence of altitude and slope on physical properties and fiber dimensions of Persian oak wood. In addition, the relationship among wood properties, site conditions (temperature and rainfall) and growth traits of trees (tree height, DBH, basal area, age, crown diameter, crown basal area, volume and annual diameter increment) were studied by principal component analysis (PCA). Three altitude levels (1730, 1980 and 2250 m) and three slope classes (<30%, 30–45% and >45%) were considered in the current study. It was determined that trees growing in the intermediate altitude (1980 m) showed the highest oven-dry density values, and those in the lowest altitude (1730 m) revealed the lowest ones. The results also indicate significant statistical differences between altitude levels and slope classes on the fiber length, fiber diameter and volumetric swelling at the 99% confidence interval while no significant differences were found between average values of oven-dry density among different altitudes and slopes. PCA analysis indicated that altitude and temperature are the most important factors affecting the wood properties. Knowledge of the relationship between wood properties and environmental factors are essential in terms of both forestry management and wood applications. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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11 pages, 3251 KiB

Open AccessArticle

The Effect of Contact-Drying on Physical Properties of European Beech (Fagus sylvatica L.)

by Ivan Klement, Peter Vilkovský and Tatiana Vilkovská

Forests 2020, 11(8), 890; https://doi.org/10.3390/f11080890 - 16 Aug 2020

Cited by 2 | Viewed by 2310

Abstract

Beech wood is mainly used for furniture, plywood, decorative veneer manufacturing or packaging. Timber or lumber is traditionally dried in kilns by processes often taking several weeks. This research deals with more rapid process called contact-drying process. Drying was performed using the heating [...] Read more.

Beech wood is mainly used for furniture, plywood, decorative veneer manufacturing or packaging. Timber or lumber is traditionally dried in kilns by processes often taking several weeks. This research deals with more rapid process called contact-drying process. Drying was performed using the heating plates with a temperature of 160 °C and pressures of 1.0 MPa, 1.4 MPa and 1.8 MPa. The results were compared to conventional warm-air drying. The warm-air drying mode was divided into two phases, with and without free water and bound water in the dried wood. The density of the samples increased remarkably during the contact-drying. The effect of the pressure of the heating plates was substantial. The difference in the average density between the pressure of 1.0 MPa and 1.8 MPa was more than 22 kg·m⁻³. The pressure of the heating plates affected the process and the resulting change in the sample thickness. The change in the sample thickness was more considerable in the case of the tangential samples. The thickness did not increase significantly after air conditioning. During contact-drying, the hygroscopicity and absorptivity of wood reduced on average by 21.24% and 25%, respectively, compared to warm-air drying. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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17 pages, 4949 KiB

Open AccessArticle

Anatomical Features and Its Radial Variations among Different Catalpa bungei Clones

by Yamei Liu, Liang Zhou, Yingqi Zhu and Shengquan Liu

Forests 2020, 11(8), 824; https://doi.org/10.3390/f11080824 - 29 Jul 2020

Cited by 13 | Viewed by 2658

Abstract

Research highlights: Annual wood anatomy (xylem) aids our understanding of mature wood formation and the growth strategies of trees. Background and Objectives: Catalpa bungei is an important native species in China that produces excellent quality wood. Herein, we clarified the effects of the [...] Read more.

Research highlights: Annual wood anatomy (xylem) aids our understanding of mature wood formation and the growth strategies of trees. Background and Objectives: Catalpa bungei is an important native species in China that produces excellent quality wood. Herein, we clarified the effects of the genetic origin and cambial age on the anatomical characteristics of C. bungei wood. Materials and Methods: Six new 13-year-old C. bungei clones: ‘1-1’ (n trees = 3), ‘1-3’ (n trees = 3), ‘2-7’ (n trees = 3), ‘2-8’ (n trees = 3), ‘8-1’ (n trees = 4), and ‘9-1’ (n trees = 3) were removed for study from a plantation in Tianshui City, Gansu province, China. Xylem features were observed and the anatomical variables were manually measured via image analysis on (macro- micro-, and ultra-) features cut from radial increments of earlywood and latewood sampled at breast height. Results: Between the age of 1 and 2 years, wood was diffuse-porous; between the age of 3 and 9 years, wood was semi-ring-porous; and between the age of 10 and 13 years, wood was ring-porous. The effect of clones on anatomical characteristics was significant except for the microfibril angle in latewood and ring width. The transition between juvenile and mature wood was between 7 and 8 years based on patterns of radial variation in fiber length (earlywood) and microfibril angle. From the pith to the bark, fiber length, double wall thickness, fiber wall: lumen ratio, vessel diameter in earlywood, proportion of vessel in earlywood, and axial parenchyma in latewood increased significantly, whereas ring width, earlywood vessels, and the proportion of fiber decreased significantly. In addition, other features, such as vessel length, microfibril angle, and ray proportion, did not differ significantly from the pith to the bark. Conclusions: Breeding program must consider both clone and cambial age to improve the economic profitability of wood production. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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11 pages, 4744 KiB

Open AccessArticle

A Comparison of the Loading Direction for Bending Strength with Different Wood Measurement Surfaces Using Near-Infrared Spectroscopy

by Yohei Kurata

Forests 2020, 11(6), 644; https://doi.org/10.3390/f11060644 - 05 Jun 2020

Cited by 4 | Viewed by 2254

Abstract

Wood is widely used throughout society for building resources and paper. To further expand wood’s use in the wood industry, we tested the bending strength properties of wood and certified its internal quality by using near-infrared spectroscopy (NIRS). In this study, the relationship [...] Read more.

Wood is widely used throughout society for building resources and paper. To further expand wood’s use in the wood industry, we tested the bending strength properties of wood and certified its internal quality by using near-infrared spectroscopy (NIRS). In this study, the relationship between bending strength and loading direction was compared by changing the light acquisition point of wood surfaces to elucidate the anisotropy of the wood using NIRS. The two loading directions were defined by using a bending test as the radial section and the tangential section. Two light acquisition points with NIRS were also defined by a bending test as the loading position (the compression surface) and the opposite surface (the tensile surface), and a comparison was made between the prediction accuracy of the wood’s mechanical strength properties obtained via a bending test using two pieces of light acquisition data. The strength properties of the wood bending tests were the elastic modulus in bending (E_b), the bending strength (F_b) and density (DEN). Cryptomeria japonica was prepared and cut into a final size of 20 mm × 20 mm × 320 mm. Near-infrared (NIR) spectra were obtained from the compression force side and the tensile force side (calculating these averages), and a partial-least-squares regression (PLSR) was performed for the regression analysis. In the NIR measurement position, the best calibration results of the PLSR were the averaged data between the side undergoing the compression force and that undergoing the tensile force. Comparing the two loading directions, the result for the radial section was slightly superior to that of the tangential section. The radial section showed a good relationship between the spectra acquisition position and the arrangement of the wood’s structure. The estimation accuracy of bending strength properties differed depending on the location where the NIR spectra acquisition was performed. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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21 pages, 9744 KiB

Open AccessArticle

Representative Hardwood and Softwood Green Tissue-Microstructure Transitions per Age Group and Their Inherent Relationships with Physical–Mechanical Properties and Potential Applications

by Oswaldo Mauricio González, Anahí Velín, Andrés García, Carlos R. Arroyo, Hua Lun Barrigas, Karla Vizuete and Alexis Debut

Forests 2020, 11(5), 569; https://doi.org/10.3390/f11050569 - 19 May 2020

Cited by 9 | Viewed by 3740

Abstract

A better understanding of wood form–structure–function relationships and potentialities can lead to an enormous pool of fascinating solutions and inventions. In this research advances from both the anatomical and the mechanical points of view, the principles, fundamentals and concept generators derived from the [...] Read more.

A better understanding of wood form–structure–function relationships and potentialities can lead to an enormous pool of fascinating solutions and inventions. In this research advances from both the anatomical and the mechanical points of view, the principles, fundamentals and concept generators derived from the inherent relationship between green tissue-microstructure and physical–mechanical properties of two representative woody species. Specifically, a total of 120 small-clear samples cut from six (e.g., three per wood species) Eucalyptus globulus (i.e., hardwood) and Cupressus macrocarpa (i.e., softwood) trees were sampled and tested to determine the tissue transitions per age group (e.g., juvenile, mature and senile) in terms of density, area, roundness and sphericity of vessel elements, longitudinal tracheids and longitudinal/ray parenchyma cells. Moreover, the studied green tissue-microstructure transitions were compared and analysed with the corresponding physical–mechanical properties [i.e., green density, moisture content, modulus of rupture (MOR) and modulus of elasticity (MOE)] of each species, which in turn were acquired from 159 tests carried out according to the German Deutsches Institut für Normung (DIN standards). The results herein show mature and senile wood tissues are more rigid and mechanically resistant than juvenile ones, which is partially influenced by the progressive increment in cell-wall thickness as the wood-tissue ages, and this process is of greater magnitude for the eucalyptus species. Indeed, this representative hardwood species was found superior in terms of mechanical resistance to the progression of stresses due to a complex porous vascular system that becomes stronger as the tissue-microstructure ages. The design principles underlying the natural architectures of both studied green tissues provide concept generators for potential biomimetic and engineering applications, e.g., eucalyptus species are suitable for structural applications, whereas the superior flexibility found in the cypress species could be well bio-mimicked into composite panels, where the balance between strength and rigidity is of high relevance. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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15 pages, 2934 KiB

Open AccessArticle

Within-Site Variability of Liana Wood Anatomical Traits: A Case Study in Laussat, French Guiana

by Félicien Meunier, Sruthi M. Krishna Moorthy, Hannes P. T. De Deurwaerder, Robin Kreus, Jan Van den Bulcke, Romain Lehnebach and Hans Verbeeck

Forests 2020, 11(5), 523; https://doi.org/10.3390/f11050523 - 07 May 2020

Cited by 9 | Viewed by 2562

Abstract

Research Highlights: We investigated the variability of vessel diameter distributions within the liana growth form among liana individuals originating from a single site in Laussat, French Guiana. Background and Objectives: Lianas (woody vines) are key components of tropical forests. Lianas are believed to [...] Read more.

Research Highlights: We investigated the variability of vessel diameter distributions within the liana growth form among liana individuals originating from a single site in Laussat, French Guiana. Background and Objectives: Lianas (woody vines) are key components of tropical forests. Lianas are believed to be strong competitors for water, thanks to their presumed efficient vascular systems. However, unlike tropical trees, lianas are overlooked in field data collection. As a result, lianas are often referred to as a homogeneous growth form while little is known about the hydraulic architecture variation among liana individuals. Materials and Methods: We measured several wood hydraulic and structural traits (e.g., basic specific gravity, vessel area, and vessel diameter distribution) of 22 liana individuals in a single sandy site in Laussat, French Guiana. We compared the liana variability of these wood traits and the correlations among them with an existing liana pantropical dataset and two published datasets of trees originating from different, but species-rich, tropical sites. Results: Liana vessel diameter distribution and density were heterogeneous among individuals: there were two orders of magnitude difference between the smallest (4 µm) and the largest (494 µm) vessel diameters, a 50-fold difference existed between extreme vessel densities ranging from 1.8 to 89.3 vessels mm⁻², the mean vessel diameter varied between 26 µm and 271 µm, and the individual theoretical stem hydraulic conductivity estimates ranged between 28 and 1041 kg m⁻¹ s⁻¹ MPa⁻¹. Basic specific gravity varied between 0.26 and 0.61. Consequently, liana wood trait variability, even within a small sample, was comparable in magnitude with tree surveys from other tropical sites and the pantropical liana dataset. Conclusions: This study illustrates that even controlling for site and soil type, liana traits are heterogeneous and cannot be considered as a homogeneous growth form. Our results show that the liana hydraulic architecture heterogeneity across and within sites warrants further investigation in order to categorize lianas into functional groups in the same way as trees Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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18 pages, 3522 KiB

Open AccessArticle

Heat Treatment of Pine Wood: Possible Effect of Impregnation with Silver Nanosuspension

by Hamid R. Taghiyari, Siavash Bayani, Holger Militz and Antonios N. Papadopoulos

Forests 2020, 11(4), 466; https://doi.org/10.3390/f11040466 - 20 Apr 2020

Cited by 25 | Viewed by 3582

Abstract

The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat [...] Read more.

The scope of the present work was to study the effects of heat treatment (at different mild temperatures) on the physicomechanical properties of pine wood, and to find out if impregnation with nanosilver may have any potential influence on the impact of heat treatment. Impregnation of wood with a 400-ppm silver nanosuspension was carried out under an initial vacuum pressure of 0.07 MPa, followed by a pressure of 0.25 MPa for thirty minutes, before heat treatment. Heat treatment was carried out under hot air at three relatively mild temperatures, 145, 165, and 185 °C. Results showed improvement of some properties in heat-treated wood at 145 °C. This was indicative of the improving impact caused by hornification and irreversible hydrogen bonding in the course of water movements due to heat treatment; significant fluctuations in the intensities of FTIR spectra bands at 1750–1500 cm⁻¹ were corroborating evidence of chemical alterations in hemicellulose polymer. The high mass loss at temperature 185 °C, and the extreme thermal degradation thereof, overcame the improving effects of hornification and formation of irreversible hydrogen bonds, consequently mechanical properties decreased significantly. Interaction of different elements involved made it hard to predict properties in specimens modified at 165 °C. Impregnation of specimens with nanosilver suspension resulted in significant increase of mass loss in specimens heat-treated at 185 °C, and significant fluctuations in properties of specimens heat-treated at 145 °C. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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14 pages, 4449 KiB

Open AccessArticle

Density Distribution in Wood of European Birch (Betula pendula Roth.)

by Ewa Dobrowolska, Paulina Wroniszewska and Agnieszka Jankowska

Forests 2020, 11(4), 445; https://doi.org/10.3390/f11040445 - 15 Apr 2020

Cited by 15 | Viewed by 3594

Abstract

The aim of the presented research is to perform a comprehensive analysis of wood density variability on the longitudinal and transverse cross-section of log trees at the age of 70 to 72 years of Betula pendula Roth. and the creation of density distribution [...] Read more.

The aim of the presented research is to perform a comprehensive analysis of wood density variability on the longitudinal and transverse cross-section of log trees at the age of 70 to 72 years of Betula pendula Roth. and the creation of density distribution maps. Furthermore, the determination proportion of juvenile and mature wood was done. Wood density was determined with a non-destructive method using an isotopic densimeter. It was found that the wood location, both in cross-section and longitudinal section of the trunk, had a statistically significant effect on the average density of birch wood. The average density of whole logs was significantly higher than the average density at the breast height. On the cross-section, the distribution of average densities determined at the breast height, as well as on ¼ of the log height, properly depicted the distribution of average densities on the cross-section determined for the whole logs. The geographical direction (north–south) did not have a statistically significant effect on the distribution of average densities on the cross-section of the tested birch logs. Full article

(This article belongs to the Special Issue Wood Structure and Properties)

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