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1.
Summary Two types of particleboards bonded with an isocyanate resin, one with uniform vertical density profile (homo-profile), and
the other with conventional U-shaped profile, were fabricated to various density levels using lauan (Shorea spp.) particles. The fundamental relationships between the density profile and the board properties were determined, and
the results are summarized as follows:
1. In homo-profile boards, the moduli of rupture (MOR) and elasticity (MOE), internal bond (IB) strength, and screw withdrawal
resistance (SWR), are highly correlated to the board mean density.
2. The bottom limit of the board density is estimated to be ca. 0.25 g/cm3, based on the correlation regressions between mechanical properties and mean density.
3. At equal mean density level, the MOR and MOE of the conventional particleboards are higher than the homo-profile boards,
due to the higher density near the faces. However, the reverse is true for IB, owing to the presence of the low density core
in the former.
4. The net impact of peak density on MOR and MOE is greater at higher mean density level while raising the core density results
in more pronounced improvement in IB at lower density.
5. In addition to the compaction ratio, the dimensional stability of the board is also affected by the peak area and mat moisture
content.
Received 9 January 1997 相似文献
2.
Effects of strand length and layer structure on some properties of strandboard made from bamboo 总被引:1,自引:0,他引:1
Strandboard panels were experimentally produced from moso bamboo (Phyllostachys pubescens) using various strand lengths and layer structures to evaluate the effects of manufacturing parameters on panel properties.
The strandboard was fabricated in a laboratory using diphenylmethane diisocyanate (MDI) resin and laboratory-made strands
of four lengths and four different structures. Strand alignment distributions and concentration parameter (k) values were greatly affected by strand length. A linear correlation was found between the value of k and the modulus of rupture (MOR), with correlation coefficients of 0.81 and 0.93 for unidirectional boards and three-layer
boards, respectively. This correlation may be used to predict the strength properties of boards. Bending properties were significantly
affected by both the strand length and the layer structure of the bamboo strandboard tested. Elasticity data from unidirectional
boards and random boards can be used to predict the elastic properties of three-layer boards. The linear expansion (LE) of
the random boards increased with decreasing strand length. The difficulty in mat forming and resin distribution for longer
strands could cause deviation in modulus of elasticity (MOE) and LE, especially in strand lengths around 80 mm. 相似文献
3.
Abstract Binderless boards were prepared from kenaf core under various manufacturing conditions and their water resistance
properties were evaluated. The board properties evaluated were retention ratios of modulus of rupture (MOR) and modulus of
elasticity (MOE), internal bonding strength after water treatment (IB), thickness swelling (TS), water absorption (WA), and
linear expansion (LE). These values were then compared with those of boards bonded with urea-formaldehyde (UF), urea melamine
formaldehyde (UMF), and phenol-formaldehyde (PF) resins, and their water resistance properties were assessed. We found that
pressing temperature was one of the most important conditions for the improvement of water resistance properties. The retention
ratios of MOR, MOE, and IB of kenaf core chip binderless boards (pressing temperature 200°C, target density 0.8g/cm3, and the three-step pressing of 6MPa for 10min, then 4MPa for 3min, and 2MPa for 3min) were 37.1%, 49.9%, and 55.7%, respectively,
compared with values for UMF-bonded boards of 22.5%, 27.1%, and 40.7%, and values for PF-bonded boards of 42.8%, 41.8%, and
54.1%, respectively. The results showed that the water resistance properties of binderless boards were higher than those of
UMF-bonded boards and almost as high as those of PF-bonded boards.
Part of this article was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, March 2003 相似文献
4.
This study investigated the effects of mild steam treatment (0.1 MPa for 2 h) of natural bio-based fibers and orientation
(0° and 90°) of those fibers in various fiberboards. Ramie bast, pineapple leaf, and sansevieria fiber bundles were used as
materials. The composite fiberboards were prepared using phenol-formaldehyde (PF) resin. To investigate the effect of mild
steam treatment on wettability, contact angles of PF resin to the fiber were measured. The mechanical properties of the boards
were examined as well as their dimensional stability. The contact angle data showed that mild steam treatment was effective
in improving the wettability of fibers. Unioriented steam-treated boards showed better performance of internal bond (IB),
moduli of rupture (MOR) and elasticity (MOE), thickness swelling (TS), and water absorption (WA) than other boards. Unioriented
steam-treated sansevieria board with longitudinal fiber direction showed higher average values of MOR (403 MPa), MOE (39.2
GPa), and IB (1.33 MPa) and lower values of TS (5.15%) and WA (8.68%) than other boards. The differences in the mechanical
properties and dimensional stability of boards were found mainly due to the differences in the ratios of fiber fraction of
the boards to the density of the fiber bundles. 相似文献
5.
6.
Ajaye Babatunde 《林业研究》2011,21(1):111-115
Cement-bonded particleboards of 6 mm in thickness were manufactured using maize stalk (Zea mays) particles of uniform sizes at three levels of board density and additive concentrations respectively. The bending strength and dimensional properties were assessed. Increase in board density and additive concentration caused increase in Modulus of rupture (MOR), Modulus of elasticity (MOE), and decrease in Thickness swelling (TS) and Water absorption (WA). The MOR, MOE and TS of the boards were significantly affected by board density except for WA, but additive concentration affected all the boards’ properties examined at p ≥ 0.05. Strong and dimensional stable cement-bonded boards could be manufactured from maize stalk particles with Portland cement as the binder after hot water treatment. Although the dimensional stability and mechanical strength properties of the boards were affected by the board density and additive concentration, the study revealed that cement-bonded particleboards could be manufactured from maize stalk (Zea mays) particles. However, the increase in board density and additive concentration could cause the increase in MOR and MOE, and cause the decrease in TS and WA of boards. 相似文献
7.
Mohammad Derikvand Nathan Kotlarewski Michael Lee Hui Jiao Gregory Nolan 《Wood material science & engineering》2020,15(3):172-181
ABSTRACTThe main goal of this study was to investigate the visual characteristics, recovery rate, and flexural properties of sawn boards from a fibre-managed plantation Eucalyptus globulus resource as a potential raw material for structural building applications. The impacts of the visual characteristics, strength-reducing features, and variation in basic density and moisture content on the bending modulus of elasticity (MOE) and modulus of rupture (MOR) of the boards were investigated. The reliabilities of different non-destructive methods in predicting MOE and MOR of the boards were evaluated, including log acoustic wave velocity measurement and numerical modellings. The MOE and MOR of the boards were significantly affected by the slope of grain, percentage of clear wood, and total number of knots in the loading zone of the boards. The normal variation in basic density significantly influenced the MOE of the boards while its effect on the MOR was insignificant. The numerical models developed using the artificial neural network (ANN) showed better accuracies in predicting the MOE and MOR of the boards than traditional multi-regression modelling and log acoustic wave velocity measurement. The ANN models developed in this study showed more than 78.5% and 79.9% success in predicting the adjusted MOE and MOR of the boards, respectively. 相似文献
8.
Kiyohiko Fujimoto Yasushi Hiramatsu Atsushi Miyatake Kenta Shindo Masahiko Karube Masaki Harada Seiichiro Ukyo 《Journal of Wood Science》2010,56(6):444-451
The object of this study was to investigate the strength properties of edge-glued laminae and to propose a suitable grading
method based on the lamina modulus of elasticity (MOE). Edge-glued laminae composed of lumber with similar MOEs (uniform laminae)
and edge-glued laminae produced by randomly gluing lumber independent of MOE (random laminae) were made from karamatsu (Larix kaempferi) lumber having the same thickness and length, but various widths. For both the uniform and random laminae, there was a strong
correlation between MOE values measured using the longitudinal vibration technique, the static bending test, and a grading
machine. The average values of bending, tensile, and compressive strengths of the uniform laminae were similar to those of
the random laminae. On the other hand, the average strength of laminae without end joints was significantly higher than that
of finger-jointed laminae for both uniform and random laminae. Finger-joints and knots played a significant role in the failure
of specimens, but the edge-gluing and the difference in MOE within an edge-glued lamina did not appear to affect the strength
properties. The bending, tensile, and compressive strengths of edge-glued laminae were strongly correlated to the lamina MOE. 相似文献
9.
10.
This study examined the effects of density and layer structure on the mechanical properties and dimensional stability of strandboard
manufactured from moso bamboo (Phyllostachys pubescens). The strandboard was fabricated in a laboratory at five densities and three different structures including a randomly oriented
homogenous board, a unidirectionally oriented homogenous board, and a three-layered board with a cross-oriented core layer
(BOSB). Bamboo strand alignment distribution could be predicted using the von Mises distribution function. Bending properties
increased with increasing density and were affected by layer structure. The modulus of rupture (MOR) of the threelayered board
in the parallel direction increased remarkably compared with the random board MOR; in the perpendicular direction, it exhibited
less strength reduction. Elastic properties of the three-layered board could be predicted using elastic constants of the unidirectional
board. Internal bond strength (IB) was greatly affected by density, but the layer structure effect did not appear in IB. Linear
expansion per unit moisture change ranged from 0.017 to 0.022 for random and three-layered boards; these values are comparable
with or lower than values for commercial board. 相似文献
11.
A model to predict the bending modulus of elasticity (MOE) of oriented strand board (OSB) panels produced by batch processing
is presented. The approach developed herein is unique in its comprehensiveness since the MOE is determined from information
on the panel structure, temperature and moisture profiles and vertical density profiles obtained from the mat formation and
compression models presented in Part 1. Comparison of predicted MOE values with those measured from 24 commercially produced
panels shows good agreement considering some of the uncertainties involved. Simulations show that the MOE can be increased
by any of the following changes: reduced fines content, increased panel density, better flake alignment in each of the three
layers within a panel, increased flake length and a larger difference between the density of the face and core layers. The
model was also used in a genetic algorithm to carry out an optimization study of batch OSB manufacturing. This analysis showed
that by combining the appropriate reduction in the amount of flakes used, increase in fines content, improvement in flake
alignment within each of the face and core layers and shortening of the batch time, a significant theoretical profit increase
from the base case scenario can be obtained. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(1):88-96
The aim of the study was to investigate the possibility of strength grading Norway spruce [Picea abies (L.) Karst.] saw logs on the basis of simulated X-ray LogScanner measurements and to evaluate the potential accuracy of X-ray LogScanner measurements of green heartwood density and percentage of heartwood. The study was based on 272 logs for strength grading and 29 logs for measurements of green heartwood density and percentage of heartwood. The logs were scanned using computed tomography (CT). After sawing, the modulus of elasticity (MOE) of the centre boards was measured using a strength-grading machine. The CT images were used for simulations of an X-ray LogScanner, resulting in simulated measurements of different variables such as diameter, taper, percentage of heartwood, density and density variations. Multivariate models for prediction of MOE were then calibrated using partial least squares (PLS) regression. The MOE of a log was defined as the mean value of the MOE of the two centre boards. The study showed that the simulated X-ray LogScanner measured the percentage of heartwood and green heartwood density with relatively high accuracy (R 2 = 0.94 and R 2 = 0.73, respectively, after removing two outliers) and that these and other variables measured by the simulated X-ray LogScanner could be used to predict the stiffness of the centre boards. These predictions were used to sort the logs according to the predicted MOE. When sorting out 50% of the logs (''high-strength'' logs), the percentage of C30 boards increased from 73% (all logs in the study) to 100% (only ''high-strength'' logs). The rest of the logs could then be divided into two groups, one of them with 100% C24 and C30 boards. 相似文献
13.
Hideaki Korai Kimihiro Uemura Takuji Esashi Masaharu Suzuki 《Journal of Wood Science》1999,45(5):402-410
The purpose of this study was to reveal the effects of various levels of mat-moisture content (m.m.c.) and the closed-press system for making single- or three-layer particleboard on the density profile, thickness swelling, specific moduli of elasticity (MOE) and rupture (MOR) and internal bond strength. Internal gas pressure was measured in an enclosed frame; and the larger the m.m.c., the higher the internal gas pressure became. When rising water vapor (steam) struck particles, it plasticized them and cured the adhesive, resulting in improved interparticle contact. The vertical density gradient in the three-layer board was larger than that in the single-layer board. As for thickness swelling by cold-water soaking, the single-layer boards were less affected than the three-layer boards and showed good dimensional stability with increased m.m.c. The open-system boards swelled more than the closed-system boards. The closed-system single-layer board made at high m.m.c. returned nearly to the prime thickness by air-drying after cold-water soaking. Specific MOE and MOR were larger at 15% or 10% m.m.c. than those at other m.m.c. Considerable reductions of specific MOR and MOE of the closed-system three-layer board were observed at 20% or 25% m.m.c.Part of this report was presented at the 45th annual meeting of the Japan Wood Research Society, Tokyo, April 1995 and at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998 相似文献
14.
An outdoor exposure test was conducted on kenaf core binderless boards (pressing temperatures 200°, 180°, and 160°C; pressing
pressure 3.0 MPa, time 10 min, target board thickness 5 mm, target board density 0.8 g/cm3) to estimate their bond durability. Modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding strength (IB),
thickness change, weight loss, Fourier transform infrared (FTIR) spectra, and color difference (ΔE*) by the CIE L*a*b* system were measured at various outdoor exposure periods up to 19 months. These values were then compared with those of a
commercial medium-density fiberboard (MDF; melamine-urea-formaldehyde resin; thickness 9.0 mm, density 0.75 g/cm3). Generally, dimensional stability and the retention ratios of MOR, MOE, and IB after the outdoor exposure test increased
with increased pressing temperature of binderless boards. The MOR retention ratio of the kenaf core binderless boards with
a pressing temperature of 200°C was 59.5% after 12 months of outdoor exposure, which was slightly lower than that of the MDF
(75.6% after 11 months of outdoor exposure). Despite this, the bond durability of the kenaf core binderless boards should
be viewed as favorable, especially when considering the fact that the retention ratio of 59.5% was achieved without binder
and without obvious element loss.
Part of this report was presented at the International Symposium on Wood Science and Technology, IAWPS2005, November 27-30,
2005, Yokohama, Japan 相似文献
15.
Jun Tanabe Akira Tamura Jyunichi Ohshima Kazuya Iizuka Shinso Yokota 《Scandinavian Journal of Forest Research》2017,32(1):39-44
With emphasis on tree breeding for wood quality in Picea jezoensis, we aimed to evaluate radial and between-family variations in the microfibril angle (MFA) of the S2 layer in the latewood tracheids in 10 open-pollinated families of 43-year-old P. jezoensis trees. In addition, the relationships between MFA/wood density with the modulus of elasticity (MOE) or modulus of rupture (MOR) were investigated. Significant differences in MFA between families were found from the pith toward the bark. MFA showed higher values around the pith area, although some families showed relatively lower values than others around this area. In addition, due to a larger coefficient of variations of MFA near the pith, the potential for juvenile wood MFA improvement may be greater compared with mature wood. MOE was correlated with MFA in juvenile wood and with wood density in mature wood, whereas MOR was mainly correlated with wood density at radial positions in both woods. Therefore, to improve the MOE and MOR of P. jezoensis wood, both MFA and wood density would be factors to consider in both juvenile and mature woods. On the other hand, there are indications that, only wood density would be an important criterion for improving mature wood properties. 相似文献
16.
Fauzi Febrianto Sahroni Wahyu Hidayat Edi Suhaimi Bakar Gu-Joong Kwon Jin-Heon Kwon Soon-Il Hong Nam-Hun Kim 《Wood Science and Technology》2012,46(1-3):53-62
Bamboo has gained increasing attention as an alternative raw material for use in the manufacture of composite boards. Three-layer OSBs were made using Betung bamboo (Dendrocalamus asper (Schultes.f) Backer ex Heyne) strands to evaluate the effects of strand length and pre-treatment techniques on the physical, mechanical, and durability properties. Three different strand lengths, namely 50, 60, and 70?mm, were prepared. Prior to the manufacture into OSB, the strands were immersed in cold water for 24?h and in 6% acetic anhydrides solution for 48?h. The OSBs were fabricated using 5% MDI resin based on the strand dry weight. The results indicated that MOR and MOE values in perpendicular to the grain direction were much influenced by strand length. The dimensional stability of OSB was slightly improved by immersing the strands in acetic anhydride solution. Immersing strands in cold water and acetic anhydride solution improved the resistance of OSB against subterranean termite (Macrotermes gylvus) attack under the adopted experimental condition. All OSB parameters manufactured in this experiment were better than the minimum requirement of CSA 0437.0 (Grade O–2) standard. 相似文献
17.
《湖北林业科技》2012,(6)
对江汉平原水杉、池杉、落羽杉人工林物理力学性能进行了研究,结果表明:落羽杉的密度和硬度最大;落羽杉、水杉、池杉的抗弯强度差异不大;水杉的弹性模量最大,约为落羽杉的2.3倍,落羽杉的弹性模量与池杉的比较接近。南北方向对水杉、池杉、落羽杉的密度、顺纹抗压强度在5%水平上差异均不显著,对池杉、水杉抗弯强度在5%水平上差异不显著,对落羽杉抗弯强度在1%水平上差异显著,对落羽杉、池杉的弹性模量在1%水平上差异显著,对水杉的弹性模量在5%水平上差异不显著。三杉南北面近树皮处木材的密度、抗弯强度、弹性模量、顺纹抗压强度均大于髓心处。对水杉、池杉、落羽杉物理力学性能比较研究,旨在为其培育及合理利用提供依据。 相似文献
18.
人工林杉木和杨树木材物理力学性质的株内变异研究 总被引:4,自引:0,他引:4
按照中国国家标准研究杉木和I-214杨树木材的抗弯弹性模量、抗弯强度、顺纹抗压强度和密度,同时按照日本国家标准研究2个树种的顺纹抗剪强度.结果表明:杉木的抗弯强度、顺纹抗压强度和密度由胸高直径处向上呈波浪形增加,抗弯弹性模量则稳定降低,但不同高度间杉木的物理力学性质没有显著差异;近树皮处木材的物理力学性质高于近髓心处木材,并有极显著差异.对于I-214杨树,只有抗弯弹性模量从髓心到树皮逐渐增加,其他的物理力学性质,最小值在从髓心到树皮的过渡区,最大值在近树皮处,从髓心到树皮,杨树的物理力学性质有极显著的差异.杉木和杨树的径面顺纹抗剪强度从髓心到树皮有极显著差异,并且近树皮的高于近髓心的木材,而弦面顺纹抗剪强度从髓心到树皮没有显著差异.木材密度与力学性质有很好的线性相关关系,木材密度是一个很好的力学强度的预测手段. 相似文献
19.
Geir I. Vestøl Carolin Fischer Olav Høibø Audun Øvrum 《Scandinavian Journal of Forest Research》2016,31(8):758-765
This study provides an analysis on the variability of structural timber of Norway spruce (Picea abies) grown in Norway. Density, modulus of elasticity (MOE) and bending strength were measured on 1188 boards from 205 trees, sampled from 14 sites throughout Southern Norway, Eastern Norway and Trøndelag. The area represents the procurement area for the majority of Norwegian sawmills. The variability of the timber properties was analysed in a linear mixed model where the random variance was divided into variance due to site, variance due to trees and within-tree variance. Models describing variance due to site based on site index, altitude and latitude were developed, and combined with data from the Norwegian National Forest Inventory to estimate mean values and variability of the timber properties. The results showed that major parts of the variance due to site are explained by altitude and site index, and for density also by latitude. Major parts of the variance due to site and the variance due to trees in bending strength and MOE were explained by density. 相似文献
20.
Thirty Norway spruce trees (Picea abies (L.) Karst.) from the forest district of the ETH Zurich were tested for bending MOR, static MOE of bending and dynamic MOE
(calculated from eigenfrequency and sound velocity). The specimens were clear and were sampled from the whole of the stem.
Their correlations to density, annual ring width, height in the tree, distribution over the stem diameter and the percentage
of compression wood were statistically analysed. All three elasticity modules and the maximal stress can be very well predicted
from a linear function of the sample density with a common gradient across the compression wood values but with different
intercepts that decrease with increasing compression wood content. The other variables have highly significant impacts on
the response variables too, however, this is largely irrelevant for the goodness of fit. Further, a clear increase of density,
of MOE and of bending MOR was measured from pith to bark and similarly with decreasing annual ring width. Concerning the height
of the stem, no distinct trend for the mechanical properties could be found. 相似文献