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1.
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   

2.
The orientation of oriented strand board (OSB) mats has been practically measured on a commercial factory production line to demonstrate the practical capabilities of the filtered image analysis (FIA) technique. Samples have been cut from OSB panels at a range of angles to the panel axis and these samples have been tested in bending. The factory data and the experimental data have been compared in order to investigate the relationship between the practical condition of fiber orientation in the factory and the bending properties as a function of orientation. The following conclusions can be drawn. Fiber orientation in the production line is good and stable irrespective of position across the width of the production line, time of day and changing line speed. The average value for the orientation angle of the forming mat on the production line is approximately 25°. The general shape of the fiber orientation distribution is similar to a normal distribution, however, at the centre of the fiber mat the sharpness of the distribution is greater than a normal distribution. The average orientations of fibers in commercial board lie at 25° and 60° to the longitudinal and perpendicular directions, respectively. The results suggest that there is potential to improve the mean fiber orientation angle of commercial OSB to improve longitudinal values of MOR and MOE, especially where perpendicular properties are not critical. Received 31 March 2000  相似文献   

3.
Cross-laminated timber (CLT) panels consist of several layers of lumber stacked crosswise and glued together on their faces. Prototype sugi CLT floor panels were manufactured and bending tests were carried out under the different parameters of lumber modulus of elasticity (MOE), number of layers, thickness of lumber and thickness of CLT panels. On the basis of above tests, bending stiffness and moment carrying capacity were predicted by Monte Carlo method. MOE of lumber was measured by using grading machine and tensile strength of lumber was assumed to be 60 % of bending strength based on the obtained bending test. Bending stiffness EI of CLT panels could be estimated by adopting composite theory and equivalent section area. Experimental moment carrying capacity showed 12 % higher value than the calculated moment carrying capacity by average lumber failure method, and also showed 45 % higher value than the calculated moment carrying capacity by minimum lumber failure method due to the reinforcement of the outer layer by the neighboring cross layer.  相似文献   

4.
A model is presented to determine the horizontal density distribution (HDD) and vertical density profile (VDP) of oriented strand board (OSB) panels produced by batch pressing. The HDD is simulated using input distributions of flake dimensions and orientation from plant measurements. Many previous HDD models rely on assumed distributions, which may not accurately characterize current manufacturing processes. The model predicts the VDP based on the compression behaviour of cellular materials in combination with temperature and moisture profiles calculated using a previously published heat and mass transport model. A novel empirical approach is applied rather than the time–temperature–moisture superposition method commonly used. The model predictions compare favourably with plant data and exhibit trends similar to previously reported experimental results. This work is the first of a two-part publication. The second part is concerned with stiffness property prediction and an optimization of the OSB manufacturing process. This work is novel in that no comprehensive model including HDD, VDP, stiffness property prediction and optimization has been reported in the literature.  相似文献   

5.
In this study, the effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood was investigated. Organo-modified montmorillonite (MMT) at four levels (0, 1, 3 and 5?%) was added to urea formaldehyde (UF) resin. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value and hot and cold water solubility), mechanical [modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, screw and nail withdrawal strengths], physical (water absorption and thickness swelling) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels complied with the general-purpose OSB minimum property requirements of European Norm. With increasing 5?% nanoclay to UF resin, mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels satisfied the thickness swelling and water absorption requirement. The results of X-ray diffraction and transmission electron microscope analysis confirmed the good dispersion of nanoclay in the resulting OSBs. Using paulownia as a fast-growing underutilized species not only can sustain the forests but also can supply raw material to countries facing shortage of wood.  相似文献   

6.
The technique of image analysis has been used to assess the quality of model oriented strand board panels by investigating the relationships between shape and size of strands, the distribution of strands and bending properties. A batch of commercial strands was analysed by image analysis and the distribution of the shape and size of strands was quantified. The strands were categorised into five strand types as a function of size and aspect ratio. In general, strand shapes were observed to be mostly rectangular and there was also a wide variation in strand dimensions in commercial material. Bigger area strands had low aspect ratios and small strands had high aspect ratios. Half of the commercial strands were longer than 100 mm.Model OSB panels were manufactured in the laboratory by hot pressing strand mats formed from each of the five strand types. Strands were laid up by hand into the forming mat and following pressing the orientation and shape of strands was evaluated by image analysis and the panels were tested in a three point bending. Large area (type 3) strands with high aspect ratios produced model panels with optimum strand orientation and mechanical properties.Type 3 panels were also fabricated from strands dropped through a slotted forming device in order to simulate the delivery of strands to the forming line under factory conditions. As the height of strand delivery increased from 0 to 100 to 200 mm the disorientation of strands in the pressed panels progressively increased and as a result mechanical properties in bending were reduced.Image analysis is therefore a powerful tool for evaluating the distribution of commercial strand shapes and the relationship between strand geometry, strand orientation and the mechanical properties of oriented strand board.  相似文献   

7.
竹木复合定向刨花板强度性能研究   总被引：1，自引：0，他引：1  
本文论述了竹材、意大利杨复合定向刨花板的强度性能,就胶种、刨花厚度、竹材所占比率、板密度、板坯结构、施胶量等诸因子对板材强度性能的影响进行了探讨。结果表明:(1)胶种对竹木复合定向刨花板的强度影响不大;(2)降低刨花厚度或提高板密度均可使板材强度提高;(3)单层结构的复合定向刨花板强度最高;(4)提高板材中竹材的比率可使板子强度明显改善;但竹材比率过高时,板材强重比反而下降,呈开口向下的抛物线型变化;(5)酚醛树脂定向刨花板的强度随原料酸性增大而降低。  相似文献   

8.
The static strength, stiffness and fatigue life of MDF, OSB and chipboard have been measured in a 65%RH environment and a 85%RH environment. Chipboard is commonly utilised as a flooring material and OSB is also used in structural applications, for example floor decking and webs of I-beams. The mean static strengths of MDF, OSB and chipboard at 65%RH were 47.9 MPa, 27.9 MPa and 21.0Mpa, respectively, compared with 34.59 MPa, 21.70 MPa and 10.61 MPa at 85%RH. However, MDF has mostly been used in non-structural applications, such as furniture, so its resistance to fatigue loads as a structural panel is of considerable interest. In a 65%RH environment dynamic modulus values showed that whilst MDF and chipboard exhibit similar stiffness values (4 GPa), OSB is approximately 50% stiffer. However, at 85%RH MDF was the stiffest of the three materials, followed by OSB and chipboard. The fatigue life performance of all three panel products was markedly lower at 85%RH compared with 65%RH. Overall, the high RH environment had a noticeably detrimental effect on the MOE (modulus of elasticity), MOR (modulus of rupture) and fatigue lives of OSB and chipboard. This is attributed to these panels retaining more of the original characteristics of the original wood, i.e. larger particle sizes (flakes/chips) compared with the homogeneous fibrous composition of MDF. Received 5 November 1999  相似文献   

9.
The objective of this study was to investigate the physical and mechanical performance of flakeboard reinforced with bamboo strips. The study investigated three different bamboo strip alignment patterns and an experimental control. All panels were tested in static bending both along parallel and perpendicular to the lengths of the bamboo strips. Internal bond strength (IB), thickness swelling (TS), linear expansion (LE), and water absorption (WA) were also examined. As expected, modulus of rupture (MOR) and modulus of elasticity (MOE) were substantially greater for all three experimental panel types as compared to the control group. LE was also improved for all three experimental panel groups. The bamboo strip alignment patterns had no significant effect on TS, WA and IB. The sample means for MOR, MOE and LE tested perpendicular to the bamboo strip lengths yielded slightly lower mean values than corresponding samples tested parallel to the bamboo strips lengths. This difference in mechanical properties is largely attributed to low panel density in the failure zones.  相似文献   

10.
 The objective of this paper is to evaluate the arrangement of wood strands at the surface of oriented strand board (OSB) by image analysis. Two-dimensional image analysis enables the number of strands and the area of each strand to be computed. In addition, the fiber direction of each strand may be measured manually by recording the acute angle between the fiber direction and the longitudinal axis of the specimen. The image analysis results suggest the following: the average strand area is proportional to the reciprocal of the number of strands. Samples containing many smaller strands exhibit a larger variation in strand size. The average strand area does not correlate with the distribution of the strand area represented by the coefficient of variation. However, there is a reasonable correlation between the number of smaller strands in the range 0 to 1 cm2 and the coefficient of variation of strand area. At low average fiber orientations, i.e. better orientation with the principal panel axis, there is smaller variability in orientation. The upper side and lower side of OSB exhibit a different relationship between average fiber orientation and strand area. The upper side of the specimens contains larger strands and exhibits better fiber orientation than the lower side. This is thought to be a function of the production process. The lower side strands fall on a smooth moving substrate, whereas the upper side strands fall on a stable substrate of strands. The number of strands is lower on the upper side of the OSB panel because small size strands tend to migrate to the lower side of the OSB during production. The small particles tend to be vibrated through the strand mat to the lower face before pressing. Received 29 March 1999  相似文献   

11.
国外结构人造板研究现状与发展趋势   总被引：8，自引：3，他引：8  
本文介绍了国外新型结构人造板的研发现状，重点介绍了胶合层积木、单板层积材等主要结构人造板的工艺过程、基本性能和相关标准。  相似文献   

12.
卢晓宁  易痒华 《木材工业》1999,13(1):6-8,12
采用正交异性的挠度方程计算四边筒支定向刨花板的中心点挠度，并在实验基础上对此进行验证，从而得到满足实际生产的定向刨花板挠度值计算公式，并对６ｍｍ，１０ｍｍ定向刨花板进行蠕变测试，找出持荷时间与挠度之间关系，进一步分析终挠度值与初挠度值之比，静曲强度和弹性模量损失量。  相似文献   

13.
Oriented strand boards (OSB) were made using sugi wood strand with different lengths at different free fall distance conditions. Strand alignment and mechanical properties of sugi OSB were evaluated. Results obtained can be summarized as follows. The alignment angle distribution was greatly affected by both free fall distance and strand length. It was found that the standard deviation of the angles can be a measure for predicting the distribution when employing the von Mises distribution function with concentration parameter. The Monte Carlo simulation showed an agreement between the theoretical considerations and the experimental results on the strand alignment. The mechanical properties as affected by both strand length and layer structure were determined. Bending properties could be equal in both directions at 25% face layer ratio. Young's modulus obtained by the in-plane vibration method showed almost linear relation to the face layer ratio. No significant differences or only a slight difference was observed for the internal bond strength, plate-shear modulus, and nail resistance properties. Further studies are necessary.  相似文献   

14.
Randomly oriented strand boards with both uniform and conventional vertical density profiles (VDP) were manufactured, and their properties were evaluated and compared. The bending modulus of elasticity (MOE) of conventional strand boards was predicted using the laminated beam theory and the MOE-density regression equation from the uniform strand boards. The results showed that the predicted MOE of conventional strand boards was close to the measured MOE with a difference of less than 10%. The internal bond strength values of uniform strand boards were found to be higher than conventional strand boards while no significant difference was found in water-related properties. Compared with uniform strand boards, MOE values of conventional strand boards were improved only at higher density level. About 10% of improvement in MOE can be obtained for the strand boards investigated by manipulating the VDP. Steeper VDPs were predicted to be required for thinner boards than for thick boards in order to achieve the same improvement in MOE.  相似文献   

15.
Summary Laboratory scale cement-bonded particleboards were made from mixed particles of three tropical hardwoods. Boards were three-layered comprising of 2 mm thick sawdust face and 4 mm thick core layers made from flakes of three lengths-12.5 mm, 25.0 mm and 37.5 mm and two thicknesses of 0.25 mm and 0.50 mm. The panels were fabricated at three density levels of 1,050 kg/m3, 1,125 kg/m3 and 1,200 kg/m3. From the statistical factorial analysis carried out, flake length, flake thickness and board density had significant effects at 1% level of propability on the properties of the tested panels. Mean MOR ranged from 5.22 to 11.15 N/mm2; MOE-2,420 to 4,820 N/mm2; water absorption and thickness swelling following 144 hours soak in water, 32.95 to 46.00% and 0.35 to 5.47% respectively. The longer and thinner the flakes, the stronger, stiffer and more dimensionally stable the experimental cement-bonded particleboards. Similarly, the higher density panels generally exhibited higher strength values in terms of MOR and MOE and were more dimensionally stable. MOR, MOE, water absorption and thickness swelling were found to be highly correlated with flake length, flake thickness and panel density. Correlation coefficients (R) for these relationships were 0.888 to 0.986 for the combined variables; and 0.574 to 0.992 for the individual factors. In all the cases tested, the regression relationships were linear.  相似文献   

16.
Wood-based panels are viscoelastic so when a load (stress) is applied to them there is a time lag before a deflection (strain) is produced, which results in hysteresis (a loss of energy). The capture of stress versus strain hysteresis loops is a non-interruptive method of monitoring the damage produced during fatigue testing. Hysteresis loops were captured throughout the flexural fatigue testing of OSB, chipboard and MDF in four-point bending allowing the development of fatigue damage to be followed. The MDF tested had a greater mean bending strength than the OSB and chipboard. When stresses were applied to the materials as a percentage of their bending strengths, the stresses applied to the MDF samples were larger than those applied to the OSB and chipboard samples. As a result the microstrains were greater for MDF than for the chipboard and OSB. The OSB was stiffer than the chipboard and MDF, which were both of similar stiffness. The information gained from the hysteresis loops indicates that the OSB, chipboard and MDF all had fatigue limits just below 20% of their bending strengths. The fatigue limit for the MDF is likely to be slightly lower than for the chipboard and the OSB.  相似文献   

17.
The purpose of this study was to evaluate compression and swelling characteristics of individual furnish elements sampled through the thickness of lab panels pressed without resin. Commercial southern pine OSB furnish was used to press resinless mats so individual flakes could be removed from the panel after pressing and evaluated for compression behavior. 19 flake sets, each set consisting of 15 southern pine flakes with 0.65% wax, were marked and measured for thickness and mass. One set of marked flakes was randomly distributed in one layer of a mat which consisted of 19 total layers; each of the 19 layers had 15 marked flakes randomly distributed in the layer. After hot pressing each marked flake was removed from the mat. After achieving equilibrium at 35%, 65% and 98% relative humidity, each flake was again remeasured for thickness and mass. Experimental results include flake compaction ratio and its distribution through the mat thickness, flake thickness swelling under different RH environments, compaction ratio-thickness swelling relationship as well as individual flake compaction ratio and thickness swelling variations. Comparison is made to adsorption/desorption behavior of pressed flakes. Flakes from surface layers exhibited compression of 25 to 37%, about double that of flakes in core layers. As expected, flakes from surface layers showed much greater thickness swell than core flakes and the response was accentuated with higher EMC conditions. Received April 26 1999  相似文献   

18.
Several wood-based sandwich panels with low-density fiberboard core were developed for structural insulated walls and floors, with different face material, panel thickness, and core density. The elastic moduli with and without shear effect (E L, E 0) and shear modulus (Gb) were evaluated in four-point bending. Generally, the stiffer face, thicker panel, and higher core density were advantageous in flexural and shear rigidity for structural use, but the weight control was critical for insulation. Therefore, optimum designs of some virtual sandwich structures were analyzed for bending stiffness in relation to weight for fixed core densities, considering the manufactured-panel designs. As a result, the plywood-faced sandwich panel with a panel thickness of 95 mm (PSW-T100), with insulation performance that had been previously confirmed, was most advantageous at a panel density of 430 kg/m3, showing the highest flexural rigidity (E L I = 13 × 10−6 GNm2) among these panels, where E L, E 0, and G b were 3.5, 5.5, and 0.038 GN/m2, respectively. The panel was found to be closest to the optimum design, which meant that its core and face thickness were optimum for stiffness with minimum density. The panel also provided enough internal bond strength and an excellent dimensional stability. The panel was the most feasible for structural insulation use with the weight-saving structure.  相似文献   

19.
Abstract

The objective of the study was to compare the properties of oriented strand boards (OSBs) made from the following mixtures: European beech and poplar, beech and pine, poplar and pine and 100% pine (i.e. the conventional raw material for OSB in Europe). Panels with 50–50% of beech-poplar/beech-pine/poplar-pine at two density levels of 650 kg/m3 and 720 kg/m3 were made with 5% pMDI (poly methylene di-isocyanate) as binder at 180°C and 240s as press conditions. Results showed that panels comprising a mixture of European beech and poplar have higher mechanical properties compared to panels made with mixtures of pine-beech or pine-poplar. In addition, for all panels, when density is increased from 650 kg/m3 to 720 kg/m3, mechanical properties increased. Internal bond values for all designs were in the same range, especially at higher density (720 kg/m3). The pure pine panels showed lower values between different designs. Thickness swelling, an important physical property of OSB, improved when face and core layers consisted of a mixture of beech and poplar strands.  相似文献   

20.
ABSTRACT

Wood structural panels are commonly subjected to short-term accelerated weathering (AW) procedures to determine relative moisture durability for quality control and product development purposes. The panel edges contribute heavily to moisture uptake since edges represent the least resistant pathway for moisture intrusion. In full-size panels, the edge area to total surface area ratio is small, and moisture intrusion is primarily limited to panel faces. When small specimens are used, such as those in AW procedures, the ratio of edge area to total surface area increases and moisture intrusion at the edges may dominate, which is referred to as the edge effect. The purpose of this study was to determine if physical and mechanical properties of oriented strand board (OSB) and plywood after AW are influenced by specimen size. Specimen width was varied while thickness and length remained constant to understand if edge effects were present in small specimens with different edge area to total surface area ratios. Three AW procedures were evaluated to determine if the effect of specimen size depends on weathering method. No clear effect of specimen size on physical and mechanical properties of either composite type was found. Differences in flexural properties between specimen widths were observed for unweathered OSB, but similar property retention between specimen widths after AW indicated the same trend as the unweathered control. Plywood results were influenced by natural defects, resulting in high variability and absence of statistically significant differences. Lateral nail resistance connection properties of both OSB and plywood were highly variable for all treatment groups and were unaffected by weathering.  相似文献   

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