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Forests
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Wood Quality and Wood Processing
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Wood Quality and Wood Processing

A special issue of Forests (ISSN 1999-4907). This special issue belongs to the section "Wood Science and Forest Products".

Deadline for manuscript submissions: closed (15 April 2024) | Viewed by 13753

Special Issue Editor

Dr. Sofia Knapic

E-Mail Website
Guest Editor
1. SERQ—Centro de Inovação e Competências da Floresta (Innovation and Competence Forest Centre), 6100-711 Sertã, Portugal
2. ISISE (Institute for Sustainability and Innovation in Structural Engineering)—University of Coimbra, 3030-788 Coimbra, Portugal
Interests: timber products; timber properties; wood based products
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In the current forest scenario, where the quantity and quality of wood are scarce and climate change is a reality, contributing greatly to an ever-increasing risk of forest fires and an increase in pests and diseases, valuing all resources is critical. It is therefore imperative to learn to do more with less; for that, it is necessary to increase productivity and add value to natural resources, consuming less raw material and thus being in perfect alignment with the objectives of the circular economy.

The use of wood for the development of construction products adds value to the original raw material by promoting a use that will contribute to an increase in carbon retention.

This Special Issue plans to give an overview of the most recent advances in the field of Wood Quality and Wood Processing.

Potential topics include, but are not limited to:

  • Wood quality;
  • Wood natural durability;
  • Wood industrial processing;
  • Wood drying and densification;
  • Wood-based products.

Dr. Sofia Knapic
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Forests is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • wood
  • wood-based products
  • industry 4.0

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Published Papers (11 papers)

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Research

19 pages, 8273 KiB  
Article
An Efficient and Accurate Surface Defect Detection Method for Wood Based on Improved YOLOv8
by Rijun Wang, Fulong Liang, Bo Wang, Guanghao Zhang, Yesheng Chen and Xiangwei Mou
Forests 2024, 15(7), 1176; https://doi.org/10.3390/f15071176 - 6 Jul 2024
Viewed by 889
Abstract
Accurate detection of wood surface defects plays a pivotal role in enhancing wood grade sorting precision, maintaining high standards in wood processing quality, and safeguarding forest resources. This paper introduces an efficient and precise approach to detecting wood surface defects, building upon enhancements [...] Read more.
Accurate detection of wood surface defects plays a pivotal role in enhancing wood grade sorting precision, maintaining high standards in wood processing quality, and safeguarding forest resources. This paper introduces an efficient and precise approach to detecting wood surface defects, building upon enhancements to the YOLOv8 model, which demonstrates significant performance enhancements in handling multi-scale and small-target defects commonly found in wood. The proposed method incorporates the dilation-wise residual (DWR) module in the trunk and the deformable large kernel attention (DLKA) module in the neck of the YOLOv8 architecture to enhance the network’s capability in extracting and fusing multi-scale defective features. To further improve the detection accuracy of small-target defects, the model replaces all the detector heads of YOLOv8 with dynamic heads and adds an additional small-target dynamic detector head in the shallower layers. Additionally, to facilitate faster and more-efficient regression, the original complete intersection over union (CIoU) loss function of YOLOv8 is replaced with the IoU with minimum points distance (MPDIoU) loss function. Experimental results indicate that compared with the YOLOv8n baseline model, the proposed method improves the mean average precision (mAP) by 5.5%, with enhanced detection accuracy across all seven defect types tested. These findings suggest that the proposed model exhibits a superior ability to detect wood surface defects accurately. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
►▼ Show Figures

Figure 1

Figure 1
<p>Examples of enhanced images of the wood surface defect dataset.</p> Full article ">Figure 2
<p>Structure of YOLOv8 algorithm.</p> Full article ">Figure 3
<p>Structure of DWR module.</p> Full article ">Figure 4
<p>C2f-DWR module structure.</p> Full article ">Figure 5
<p>Structure of D-LKA attention.</p> Full article ">Figure 6
<p>C2f-DLKA structure.</p> Full article ">Figure 7
<p>Structure of the dynamic-head detection head.</p> Full article ">Figure 8
<p>The improved YOLOv8 algorithm structure.</p> Full article ">Figure 9
<p>Precision–recall (P-R) curves.</p> Full article ">Figure 10
<p>Comparison of detection results.</p> Full article ">Figure 10 Cont.
<p>Comparison of detection results.</p> Full article ">Figure 10 Cont.
<p>Comparison of detection results.</p> Full article ">Figure 11
<p>Grad-CAM comparison results.</p> Full article ">Figure 11 Cont.
<p>Grad-CAM comparison results.</p> Full article ">
16 pages, 4397 KiB  
Article
BPN-YOLO: A Novel Method for Wood Defect Detection Based on YOLOv7
by Rijun Wang, Yesheng Chen, Fulong Liang, Bo Wang, Xiangwei Mou and Guanghao Zhang
Forests 2024, 15(7), 1096; https://doi.org/10.3390/f15071096 - 25 Jun 2024
Viewed by 949
Abstract
The detection of wood defect is a crucial step in wood processing and manufacturing, determining the quality and reliability of wood products. To achieve accurate wood defect detection, a novel method named BPN-YOLO is proposed. The ordinary convolution in the ELAN module of [...] Read more.
The detection of wood defect is a crucial step in wood processing and manufacturing, determining the quality and reliability of wood products. To achieve accurate wood defect detection, a novel method named BPN-YOLO is proposed. The ordinary convolution in the ELAN module of the YOLOv7 backbone network is replaced with Pconv partial convolution, resulting in the P-ELAN module. Wood defect detection performance is improved by this modification while unnecessary redundant computations and memory accesses are reduced. Additionally, the Biformer attention mechanism is introduced to achieve more flexible computation allocation and content awareness. The IOU loss function is replaced with the NWD loss function, addressing the sensitivity of the IOU loss function to small defect location fluctuations. The BPN-YOLO model has been rigorously evaluated using an optimized wood defect dataset, and ablation and comparison experiments have been performed. The experimental results show that the mean average precision (mAP) of BPN-YOLO is improved by 7.4% relative to the original algorithm, which can better meet the need to accurately detecting surface defects on wood. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
►▼ Show Figures

Figure 1

Figure 1
<p>Wood defects [<a href="#B28-forests-15-01096" class="html-bibr">28</a>]: (<b>A</b>) Live_Knot, (<b>B</b>) Dead_Knot, (<b>C</b>) Quartzity, (<b>D</b>) Knot_with_crack, (<b>E</b>) Knot_missing, (<b>F</b>) Crack, (<b>G</b>) Overgrown, (<b>H</b>) Resin (Resin pocket), (<b>I</b>) Marrow (Pith), (<b>J</b>) Blue_stain.</p> Full article ">Figure 2
<p>YOLOv7 network structure.</p> Full article ">Figure 3
<p>BPN-YOLO network structure.</p> Full article ">Figure 4
<p>P-ELAN Module.</p> Full article ">Figure 5
<p>Structure of Biformer attention mechanism [<a href="#B37-forests-15-01096" class="html-bibr">37</a>].</p> Full article ">Figure 6
<p>Precision-recall (P–R) curves: (<b>a</b>) YOLOv5; (<b>b</b>) YOLOv7; (<b>c</b>) YOLOv8; (<b>d</b>) YOLOv9; (<b>e</b>) RT-DETR; (<b>f</b>) BPN-YOLO.</p> Full article ">Figure 7
<p>Comparison of detection results.</p> Full article ">Figure 8
<p>Gradient-weighted class activation map (Grad-CAM).</p> Full article ">
14 pages, 2693 KiB  
Article
Effect of the Vacuum Impregnation Process on Water Absorption and Nail-Holding Power of Silica Sol-Modified Chinese Fir
by Mengxue Tao, Xia Liu and Wei Xu
Forests 2024, 15(2), 270; https://doi.org/10.3390/f15020270 - 30 Jan 2024
Cited by 3 | Viewed by 869
Abstract
The application of fast-growing Chinese fir (Cunninghamia lanceolata) is limited due to low dimensional stability and weak mechanical strength. Silica sol can effectively improve fast-growing fir wood’s physical and mechanical properties. In order to clarify the influence of impregnation process parameters [...] Read more.
The application of fast-growing Chinese fir (Cunninghamia lanceolata) is limited due to low dimensional stability and weak mechanical strength. Silica sol can effectively improve fast-growing fir wood’s physical and mechanical properties. In order to clarify the influence of impregnation process parameters on the modification effect, the effect of the vacuum impregnation variants (e.g., pre-vacuum time, pre-vacuum pressure, pressurization time, and pressurization pressure) was discussed using the orthogonal test approach. The optimal modification process was determined by comparing the water absorption and nail-holding power under different modification processes. The range analysis and variance analysis methods were used to study the correlation between process factors and the performance of the modified wood. The results showed that the water absorption and nail-holding power of fast-growing fir wood were significantly improved via vacuum impregnating with silica sol. The optimum process parameters for water absorption and nail-holding power of fast-growing fir as the pre-vacuum time was 30 min, the pre-vacuum pressure was −0.08 MPa, the pressurization time was 3 h, and the pressurization pressure was 1.2 MPa. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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Figure 1
<p>Impregnation process of Chinese fir.</p> Full article ">Figure 2
<p>Specimen for nail-holding power.</p> Full article ">Figure 3
<p>Nail-holding power tests using the mechanical testing machine.</p> Full article ">Figure 4
<p>The weight percent gain of modified Chinese fir.</p> Full article ">Figure 5
<p>Water absorption curve analysis of untreated and modified Chinese fir.</p> Full article ">Figure 6
<p>The nail-holding power of untreated and modified Chinese fir.</p> Full article ">
13 pages, 4942 KiB  
Article
Synergistic Effects of Heating Platens’ Temperature and Compression Ratio on the Periodic Hot-Press Drying of Chinese Fir Lumber
by Xiang Weng, Xingying Zhang, Chengjian Huang, Shipeng Wang and Junfeng Hou
Forests 2024, 15(1), 203; https://doi.org/10.3390/f15010203 - 19 Jan 2024
Viewed by 766
Abstract
The effects of periodic hot-press drying on drying behavior and mechanical damage to Chinese fir lumber were investigated by taking the heating platens’ temperature (TP) and compression ratio (Rc) as experimental factors. The temperature and pressure inside [...] Read more.
The effects of periodic hot-press drying on drying behavior and mechanical damage to Chinese fir lumber were investigated by taking the heating platens’ temperature (TP) and compression ratio (Rc) as experimental factors. The temperature and pressure inside lumber were analyzed during drying process. The results were as follows. The drying rate of lumber was significantly increased with increasing TP and Rc. Scanning electron microscope (SEM) micrographs showed that bordered pit membranes, cross-field pits, middle lamella between adjacent cells, and tracheid walls were damaged after drying, and the damage became more severe with higher TP and Rc. Detachments between ray parenchyma cells and tracheids were observed at 170 °C. Nitrogen-adsorption measurement results demonstrated that more cell wall pores in the 2.5~6.2 nm pore diameter range were generated at higher TP, resulting in an enlarged specific surface area and pore volume of cell walls. These structural changes contributed to accelerating moisture migration and decreasing the drying time. Furthermore, fluctuating pressure inside lumber was the main driving force leading to moisture migration and cell tissue damage in lumber during drying. The influence of TP on internal temperature (TM) and pressure (PM) was greater than Rc. With the increase in TP from 130 to 170 °C at the Rc of 10%, the maximum TM and PM were increased by 30.90% and 39.84%, respectively. However, TP should not be too high to prevent the formation of macro-cracks caused by high pressure, which may significantly affect wood’s mechanical properties. These results provide theoretical support for periodic hot-press drying processes’ improvement and high-value utilization of Chinese fir. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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Figure 1

Figure 1
<p>Connection and test method for the online monitoring system of temperature and pressure.</p> Full article ">Figure 2
<p>Drying curves (<b>a</b>) and average drying rate (<b>b</b>) of dried lumber.</p> Full article ">Figure 3
<p>SEM micrographs of bordered pits inside lumber after drying under different conditions: (<b>a</b>) Control, (<b>b</b>) 130 °C-10%, (<b>c</b>) 130 °C-30%, (<b>d</b>) 170 °C-10%.</p> Full article ">Figure 4
<p>SEM micrographs of cross-field pits inside lumber after drying under different conditions: (<b>a</b>) Control, (<b>b</b>) 130 °C-10%, (<b>c</b>) 130 °C-30%, (<b>d</b>) 170 °C-10%.</p> Full article ">Figure 5
<p>SEM micrographs of tangential section of lumber after drying under different conditions: (<b>a</b>) Control, (<b>b</b>) 130 °C-10%, (<b>c</b>) 130 °C-30%, (<b>d</b>) 170 °C-10%.</p> Full article ">Figure 6
<p>Relationship between cumulative pore volume and pore diameter of the wood’s cell walls after drying.</p> Full article ">Figure 7
<p>Relationship between pore volume and pore diameter of wood cell wall after drying under different conditions: (<b>a</b>) 130 °C-10%, (<b>b</b>) 130 °C-30%, (<b>c</b>) 170 °C-10%, (<b>d</b>) 170 °C-30%.</p> Full article ">Figure 8
<p>Curves of temperature in Chinese fir lumber as a function of time.</p> Full article ">Figure 9
<p>Internal pressure (<b>a</b>) and peak pressure (<b>b</b>) curves of dried lumber.</p> Full article ">Figure 10
<p>Pressure drop value curves of dried lumber.</p> Full article ">
15 pages, 3985 KiB  
Article
Characterization and Yield of Eucalyptus regnans F. Muell Logs for Lumber Production
by Carlos Rozas, Barbara Zapata, Fernando Muñoz, Virna Ortiz-Araya and Oswaldo Erazo
Forests 2023, 14(12), 2359; https://doi.org/10.3390/f14122359 - 30 Nov 2023
Viewed by 1058
Abstract
The yield of Eucalyptus regnans logs for lumber production was evaluated. Crack width and length at each log end were measured. Two log-cutting plans were used to obtain sawn lumber. The first plan (PA) considered logs with diameters varying from 28 to 40 [...] Read more.
The yield of Eucalyptus regnans logs for lumber production was evaluated. Crack width and length at each log end were measured. Two log-cutting plans were used to obtain sawn lumber. The first plan (PA) considered logs with diameters varying from 28 to 40 cm, and in the second plan (PB), the log diameters ranged from 42 to 56 cm (PB). Lumber yield was determined using two log volume methods: the Japanese Agricultural Standards (JAS) and Smalian’s equation. The deformations of E. regnans lumber were measured. The Australian and Chilean standards were used to classify sawn lumber. The results showed that logs had radial cracks at both log ends. Cracks were classified into two groups, considering the crack length. Regarding the lumber deformations, most boards exhibited level B bows and crooks in both cutting plans. Levels A and B twists were prevalent in PA, whereas in PB, level A significantly outnumbered level B. The lumber yield of E. regnans in PB was higher than in PA. The lumber yield determined by Smalian’s equation was higher than that determined by the JAS method. This research provides insight into the characterization of E. regnans for lumber production, highlighting its relevance in the forestry industry. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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Figure 1

Figure 1
<p>Measurements of radial cracks. Small-end diameter (E1) and large-end diameter (E2) of the log. L = log.</p> Full article ">Figure 2
<p>Number of logs with radial cracks at both ends. Radial cracks measured in E1 and E2. Lgr &lt; rt: crack length is smaller than the log’s radius. Lgr = rt: length of the crack is equal to the log’s radius.</p> Full article ">Figure 3
<p>Number of logs with radial cracks at both ends. (<b>a</b>): Length of crack smaller than the log’s radius; (<b>b</b>) length of crack equal to the log’s radius. E1: small-end diameter; E2: large-end diameter.</p> Full article ">Figure 4
<p>Relationship between the width and length of cracks. The green points represent each log.</p> Full article ">Figure 5
<p>Total and losses of boards by cutting plan and thickness. PA: log-cutting plan 28–40 cm log diameters); PB: log-cutting plan (42–56 cm log diameters); gb: green board (ungraded board dimensions); Egb: expected green board (planned and classified board dimensions).</p> Full article ">Figure 6
<p>Number of boards graded by sawmill-based quality and cutting plan. PA: log-cutting plan (28–40 cm log diameters); PB: log-cutting plan (42–56 cm log diameters); gb: green board (ungraded board dimensions); Egb: expected green board (planned and classified board dimensions).</p> Full article ">Figure 7
<p>Number of boards by cutting plan and types of wood cuts. PA: log-cutting plan (28–40 cm log diameters); PB: log-cutting plan (42–56 cm log diameters); gb: green board (ungraded board dimensions); Egb: expected green board (planned and classified board dimensions).</p> Full article ">Figure 8
<p>Lumber yield for cutting plans using (<b>a</b>) Smalian equation and (<b>b</b>) JAS standard. GV = green lumber volume; TV = trimmed (without cracks) green lumber volume; EV = expected green lumber volume; CV = commercial lumber volume; BV = billing lumber volume.</p> Full article ">Figure 9
<p>Relationship between log size and lumber yield, according to JAS (<b>a</b>,<b>c</b>,<b>e</b>,<b>g</b>,<b>i</b>) and Smalian (<b>b</b>,<b>d</b>,<b>f</b>,<b>h</b>,<b>j</b>). GV = green lumber volume; TV = trimmed (without cracks) green lumber volume; EV = expected green lumber volume; CV = commercial lumber volume; BV = billing lumber volume.</p> Full article ">
19 pages, 8308 KiB  
Article
Combining Artificial Neural Network and Response Surface Methodology to Optimize the Drilling Operating Parameters of MDF Panels
by Bogdan Bedelean, Mihai Ispas and Sergiu Răcășan
Forests 2023, 14(11), 2254; https://doi.org/10.3390/f14112254 - 16 Nov 2023
Cited by 2 | Viewed by 1133
Abstract
Most of the parts of furniture made of medium density fiberboards (MDF) require at least one hole to be assembled. The drilling technological parameters influence the quality of holes. Factors such as tip angle of the drill bit, feed rate, type and diameter [...] Read more.
Most of the parts of furniture made of medium density fiberboards (MDF) require at least one hole to be assembled. The drilling technological parameters influence the quality of holes. Factors such as tip angle of the drill bit, feed rate, type and diameter of the drill bit, and spindle rotational speed could affect the drilling process. Therefore, the right choosing of drilling parameters is a mandatory condition to improve the drilling efficiency that is expressed through tool durability, cost, and quality of the drilling. Thus, in this work, we are proposed an approach that consists in combining two modelling techniques, which were successfully applied in various fields, namely artificial neural network (ANN) and response surface methodology (RSM), to analyze and optimize the drilling process of MDF boards. Four artificial neural network models with a reasonable accuracy were developed to predict the analyzed responses, namely delamination factor at inlet, delamination factor at outlet, thrust force, and drilling torque. These models were used to complete the experimental design that was requested by the RSM. The optimum values of the selected factors and their influence on the drilling process of the MDF boards were revealed. A part of optimum combinations among analyzed factors could be used both during the drilling of the MDF boards and prelaminated wood particleboards. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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Figure 1

Figure 1
<p>The drill bits used for drilling of MDF boards: (<b>a</b>) flat drills; (<b>b</b>) helical drills.</p> Full article ">Figure 2
<p>MDF samples used for drilling experiments: (<b>a</b>) shape and dimensions; (<b>b</b>) processed sample; and (<b>c</b>) the approach used to measure the diameters in order to calculate the delamination factor.</p> Full article ">Figure 3
<p>The machine tool and the measuring device: (<b>a</b>) ISEL GFV/GFY CNC processing centre; (<b>b</b>) the forces measuring device.</p> Full article ">Figure 4
<p>The equipment used for the measurements (<b>left</b>) and the connection diagram (<b>right</b>).</p> Full article ">Figure 5
<p>Graphical interface of the DAQ software v. 1.5.5.0.</p> Full article ">Figure 6
<p>Variation in the active power P<sub>T</sub> (blue line) and the thrust force F<sub>T</sub> (pink line).</p> Full article ">Figure 7
<p>The representation of a face central composite design and the analyzed combinations among factors (−1 is the low level of factor; +1 is the high level of factor; 0—is the middle value of factor; and ±α is the axial or star points).</p> Full article ">Figure 8
<p>The architecture of ANN models, which were designed to predict the delamination factor at the inlet (Y<sub>1</sub>); delamination factor at the outlet (Y<sub>2</sub>); thrust force (Y<sub>3</sub>); and drilling torque (Y<sub>4</sub>).</p> Full article ">Figure 9
<p>A comparison between the predicted and experimental responses: (<b>a</b>) delamination factor at the inlet; (<b>b</b>) delamination factor at the outlet; (<b>c</b>) thrust force; and (<b>d</b>) drilling torque.</p> Full article ">Figure 10
<p>The influence of the drill tip angle and tooth bite on the delamination factor at the inlet: flat drill (<b>a</b>) and helical drill (<b>b</b>).</p> Full article ">Figure 11
<p>The influence of the drill tip angle and tooth bite on the delamination factor at the outlet: flat drill (<b>a</b>) and helical drill (<b>b</b>).</p> Full article ">Figure 12
<p>The influence of the drill tip angle and tooth bite on the thrust force: flat drill (<b>a</b>) and helical drill (<b>b</b>).</p> Full article ">Figure 13
<p>The influence of the drill tip angle and tooth bite on the drilling torque: flat drill (<b>a</b>) and helical drill (<b>b</b>).</p> Full article ">
11 pages, 2642 KiB  
Article
Thermal, Mechanical and Morphological Properties of Cellulose/Lignin Nanocomposites
by Mustafa Zor, Ferhat Şen, Hikmet Yazıcı and Zeki Candan
Forests 2023, 14(9), 1715; https://doi.org/10.3390/f14091715 - 25 Aug 2023
Cited by 1 | Viewed by 1263
Abstract
Lignin, a lignocellulosic polymer material, is an important active ingredient for the high-value use of renewable resources. Thus, policies for the recovery and high value-added use of renewable lignocellulosic biomass are a realistic engineering approach to address concerns such as the climate and [...] Read more.
Lignin, a lignocellulosic polymer material, is an important active ingredient for the high-value use of renewable resources. Thus, policies for the recovery and high value-added use of renewable lignocellulosic biomass are a realistic engineering approach to address concerns such as the climate and energy crisis. In this work, the mechanical properties, thermal stability and morphology of cellulose/lignin nanocomposites were studied. Nanocomposite films containing different proportions of lignin (2.5%, 5%, 10% and 20%) were prepared. Thermal properties were assessed via thermogravimetric analysis and differential scanning calorimetry, mechanical properties via tensile test and morphological properties via scanning electron microscopy techniques. It was observed that nanolignin and nanocellulose structures are compatible with each other and depending on the main degradation temperature, the thermal stability of 2.5% lignin-containing nanocomposites is higher than that of other composites. From the results obtained, it was determined that the nanocomposite film containing 2.5% nanolignin had high thermal stability, mechanical strength and suitable morphological structure compared to other samples. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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<p>Schematic view of nanocomposite films.</p> Full article ">Figure 2
<p>TGA and DTG of nanocomposite films.</p> Full article ">Figure 3
<p>DSC curves of nanocomposite films.</p> Full article ">Figure 4
<p>SEM images of the nanocomposite films.</p> Full article ">
14 pages, 6012 KiB  
Article
Maturation Stress and Wood Properties of Poplar (Populus × euramericana cv. ‘Zhonglin46’) Tension Wood
by Yamei Liu, Xiao Wu, Jingliang Zhang, Shengquan Liu, Katherine Semple and Chunping Dai
Forests 2023, 14(7), 1505; https://doi.org/10.3390/f14071505 - 23 Jul 2023
Cited by 1 | Viewed by 1418
Abstract
Understanding the maturation stress and wood properties of poplar tension wood is critical for improving lumber yields and utilization ratio. In this study, the released longitudinal maturation strains (RLMS), anatomical features, physical and mechanical properties, and nano-mechanical properties of the cell wall were [...] Read more.
Understanding the maturation stress and wood properties of poplar tension wood is critical for improving lumber yields and utilization ratio. In this study, the released longitudinal maturation strains (RLMS), anatomical features, physical and mechanical properties, and nano-mechanical properties of the cell wall were analyzed at different peripheral positions and heights in nine artificially inclined, 12-year-old poplar (Populus × euramericana cv. ‘Zhonglin46’) trees. The correlations between the RLMS and the wood properties were determined. The results showed that there were mixed effects of inclination on wood quality and properties. The upper sides of inclined stems had higher RLMS, proportion of G-layer, bending modulus of elasticity, and indentation modulus of the cell wall but a lower microfibril angle than the lower sides. At heights between 0.7 m and 2.2 m, only the double-wall thickness increased with height; the RLMS and other wood properties such as fiber length and basic density fluctuated or changed little with height. The RLMS were good indicators of wood properties in the tension wood area and at heights between 0.7 m and 1.5 m. The results of this study present opportunities to better understand the interactions and effects of these two phenomena, which both occur quite frequently in poplar stands and can influence the wood quality of valuable assortments. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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<p>Image of sampled trees. (<b>a</b>) Measuring points at three different heights of tree 5; (<b>b</b>) maturation strains released by strain gauges of tree 6.</p> Full article ">Figure 2
<p>Schematic of measurement positions. TW: tension wood area (0°, 50°, and −60°); LW: lateral wood area (100° and −110°); OW: opposite wood area (150° and −160°).</p> Full article ">Figure 3
<p>Light microscope view of anatomical sections of poplar tension wood. (<b>a</b>) TW area; (<b>b</b>) LW area; (<b>c</b>) OW area.</p> Full article ">Figure 4
<p>Distributions of RLMS with peripheral positions (<b>a</b>) and heights (<b>b</b>). Different letters indicate significant differences according to Duncan’s means comparison tests in <span class="html-italic">p</span> &lt; 0.05. RLMS: released longitudinal maturation strains.</p> Full article ">Figure 5
<p>Distributions of anatomical measured parameters with peripheral positions (<b>a</b>) and heights (<b>b</b>). Different letters indicate significant differences according to Duncan’s means comparison tests in <span class="html-italic">p</span> &lt; 0.05. FL: fiber length; 2WT: double-wall thickness; MFA: microfibril angle; PG: proportion of G-layer.</p> Full article ">Figure 6
<p>Distributions of physical and mechanical properties with peripheral positions (<b>a</b>) and heights (<b>b</b>). Different letters indicate significant differences according to Duncan’s means comparison tests in <span class="html-italic">p</span> &lt; 0.05. BD: basic density; MOE: bending modulus of elasticity; MOR: bending modulus of rupture; CS: compressive strength.</p> Full article ">Figure 7
<p>Indentation modulus of cell-wall layer in DMT mode. (<b>a</b>) TW area, (<b>b</b>) LW area, (<b>c</b>) OW area.</p> Full article ">Figure 8
<p>Indentation modulus of cell-wall layer in DMT mode. (<b>a</b>) 0.7 m, (<b>b</b>) 1.5 m, (<b>c</b>) 2.2 m.</p> Full article ">Figure 9
<p>(<b>a</b>) Relationship of RLMS to lean angle in inclined trees, regression coefficients were not significant (<span class="html-italic">p</span> = 0.53). Mean lean angle and SD = 17.9° ± 5.11. (<b>b</b>) Relationship of RLMS to eccentricity in leaning trees, regression coefficients were significant (<span class="html-italic">p</span> = 0.01). Mean eccentricity and SD = 16.3% ± 6.90.</p> Full article ">
11 pages, 2763 KiB  
Article
Effect of Samples Length on the Characteristics of Moisture Transfer and Shrinkage of Eucalyptus urophylla Wood during Conventional Drying
by Honghai Liu, Mengqing Ke, Ting Zhou and Xinlu Sun
Forests 2023, 14(6), 1218; https://doi.org/10.3390/f14061218 - 12 Jun 2023
Cited by 3 | Viewed by 957
Abstract
Moisture transfer influences wood deformation and moisture content (MC) distribution during conventional drying of Eucalyptus urophylla wood. This study aims to investigate the effect of sample length (30, 100, and 200 mm) on moisture distribution and transfer in different directions and locations and [...] Read more.
Moisture transfer influences wood deformation and moisture content (MC) distribution during conventional drying of Eucalyptus urophylla wood. This study aims to investigate the effect of sample length (30, 100, and 200 mm) on moisture distribution and transfer in different directions and locations and on deformation of wood. The results showed that when the MC was above the fiber saturated point (FSP), the drying rate decreases exponentially with an increase of sample length; however, below the FSP, there was no obvious relationship between the drying rate and sample length and above the FSP, the moisture distribution was non-uniform along tangential, radial, and longitudinal directions and became even below the FSP, which was more significant in the middle location of wood. The greatest MC differences occurred between the surface and sub-central layers along the tangential and radial direction, which were between the end and sub-middle locations along the longitudinal direction. The effect of sample length on the MC distribution and MC differences along wood in the three directions depended on locations and the MC stage of wood; most of the free water and bound water transferred from the wood central to the ends along the longitudinal direction for three sets of samples. Bound water diffusion significantly slowed as the sample length exceeded 200 mm; sample length affects wood collapse and its recovery, but the drying rate has a lesser effect on collapse for samples with a length below 200 mm. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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<p>Schematic of samples preparation. Slices marked with A, B and I; C and D, E and F, G and H were used for the determination of the MC of the lumber.</p> Full article ">Figure 2
<p>Drying curves of the samples and the temperature and humidity in the chamber against drying time.</p> Full article ">Figure 3
<p>Drying rate against sample length above FSP.</p> Full article ">Figure 4
<p>Moisture content distribution along the tangential direction: (<b>a</b>) middle location; (<b>b</b>) end location and radial direction; (<b>c</b>) middle location; (<b>d</b>) end location. Closed and open symbols refer to 100 and 200 mm samples, respectively.</p> Full article ">Figure 5
<p>Moisture content distribution along the longitudinal direction: (<b>a</b>) average of the central, sub-central and surface, (<b>b</b>) central, (<b>c</b>) sub-central, (<b>d</b>) surface. The horizontal axis (dimensionless length) indicates the relative distance of the end, sub-middle, and middle locations to the half of 200 mm samples. Closed and open symbols refer to 100 and 200 mm samples, respectively.</p> Full article ">Figure 6
<p>Drying rate against ratio of side areas to total of samples (<b>a</b>) above the FSP, (<b>b</b>) below the FSP.</p> Full article ">Figure 7
<p>Transversal shrinkage versus MC of 30, 100, and 200 mm samples during drying.</p> Full article ">
21 pages, 820 KiB  
Article
Impacts of Foreign Trade on the Economy of Wood-Based Sectors Generating Different Levels of Value Added in the Slovak and Czech Republics
by Andrea Janáková Sujová, Katarína Marcineková and Václav Kupčák
Forests 2023, 14(5), 1029; https://doi.org/10.3390/f14051029 - 17 May 2023
Cited by 2 | Viewed by 1467
Abstract
Foreign trade belongs among the main sources of economic growth as classical theories of international trade affirm. The aim of the paper is to evaluate the impact of trade balance flows on sectors generating different value-added in the wood-based industries (WBI) of the [...] Read more.
Foreign trade belongs among the main sources of economic growth as classical theories of international trade affirm. The aim of the paper is to evaluate the impact of trade balance flows on sectors generating different value-added in the wood-based industries (WBI) of the Czech and Slovak Republics. The multivariate regression method (MLR) was applied to identify the relationship between foreign trade and economic indicators and also specific indicators assessing impacts of foreign trade on the economy of wood-based industries. The results showed that the performance of high value-added production is only slightly affected by foreign trade. It means that both monitored countries do not utilize raw wood so intensively that the positive effects of foreign trade are manifested. Growth in net exports represents a positive influence on the economy of the sector regardless of the value-added rate only if the increase in imports is smaller than in exports. The contribution of the study to existing knowledge is in using specific indicators evaluating trade impacts on the industry’s economy. The article provides new empirical insights into the influence of foreign trade balance flows on the economy of wood-based sectors with a different value-added rate. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
12 pages, 4738 KiB  
Article
Effects of the Surface Roughness of Six Wood Species for Furniture Production on the Wettability and Bonding Quality of Coating
by Qinglin Yu, Xi Pan, Zhong Yang, Li Zhang and Jingyun Cao
Forests 2023, 14(5), 996; https://doi.org/10.3390/f14050996 - 11 May 2023
Cited by 7 | Viewed by 1784
Abstract
Wood surface roughness, surface free energy (SFE), wettability, and bonding quality for water-based acrylic coatings were investigated. The samples tested in this study included Pinus radiata, Pinus sylvestris, Larch, Hemp oak, Catalpa tree, and Camphor. Sandpaper with grits of 180, 240, [...] Read more.
Wood surface roughness, surface free energy (SFE), wettability, and bonding quality for water-based acrylic coatings were investigated. The samples tested in this study included Pinus radiata, Pinus sylvestris, Larch, Hemp oak, Catalpa tree, and Camphor. Sandpaper with grits of 180, 240, 320, 400, and 500 was utilized to sand wood surfaces. The van OSS-Chaudhury-Good equation (vOCG) was used to calculate the SFE values. The modified model (M-D) was used to calculate the wettability based on the contact angle change rate (K value). The higher the K value, the faster the contact angle approaches equilibrium. A cross-cut test was used to evaluate the coating’s bonding quality. The anatomical structure of wood has an impact on the roughness of hardwood. The equilibrium contact angle is influenced by the wood species and sandpaper grit size. Sanding can make the surface of wood more wettable. Radiata pine that had been sanded to 180 grit had the highest SFE value. After finishing with waterborne acrylic, hardwood had a slightly better coating adhesion than softwood. Hemp oak wood had the lowest coating adhesion (0.6) and the highest K value (0.82). The best bonding quality (0.4) was supplied by the camphor wood with the lowest K value (0.13). Wettability in terms of K values was a good indication of determining the bonding quality of the water-based acrylic coatings. Full article
(This article belongs to the Special Issue Wood Quality and Wood Processing)
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<p>Determination of the equilibrium contact angle (<span class="html-italic">θ</span><sub>e</sub>) from a plot of the contact angle as a function of time by M-D model.</p> Full article ">Figure 2
<p>Surface topography and roughness of Catalpa (<b>a</b>) sanded P400, (<b>b</b>) sanded P500.</p> Full article ">Figure 3
<p>Surface topography and roughness of larch wood P320, P400, and P500 sanded.</p> Full article ">Figure 4
<p>Progress of contact angle and wetting time for water-based acrylic on six wood surfaces.</p> Full article ">
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