Study on sheet material made from zephyr strands V: Properties of zephyr strand board and zephyr strand lumber using the veneer of fast-growing species such as poplar

Zephyr strand board (ZSB) and zephyr strand lumber (ZSL) were produced using zephyr made from poplar veneer to investigate the greater utilization of low-density poplar as a structural material. These materials were then compared to ordinary plywood, laminated veneer lumber (LVL) from poplar veneer, lauan plywood, and particleboard. The bending properties (moduli of rupture and elasticity) of ZSB proved superior to those of poplar plywood: and ZSL produced from poplar veneer zephyr had bending properties greater than ordinary LVL from poplar veneer. Apparently, the conversion of the poplar veneer into zephyr material had a positive effect on bending properties. Additionally, poplar ZSB had bending properties superior to those of lauan particleboard and equal to those of lauan plywood. The internal bond strength of poplar veneer ZSB was nearly two times greater than that of lauan particleboard.Parts of this report were presented at the international symposium on the utilization of fast-growing trees, Nanjing, China, October 1994. Report IV appeared inMokuzai Kogyo 49:599, 1994     

Mechanical evaluation for laminated bamboo lumber along two eccentric compression directions

To evaluate the mechanical performance under two eccentric compression directions, 80 laminated bamboo lumber (LBL) column specimens were tested and analysed. Mechanical properties along two directions were compared. Bamboo nodes and drill hole are two main failure reasons for the specimens under two eccentric directions. More crack layers appeared for radial eccentric direction group specimens due to the layer structure. No matter which eccentric directions they are, the lateral deflection curves are close to the sine line, and the strain across the cross section of the LBL column for each specimen is basically linear throughout the loading process, following standard normal section bending theory. The mechanical properties for two directions are similar with each other and could follow the same design rules. Although the mechanical properties are similar for both LBL columns and parallel bamboo strand lumber (PBSL) columns as a whole, there are still some clear performance differences between the two kinds of materials. Combined all the test data under two eccentric directions, an equation for calculating the radial eccentricity influencing coefficient \( \varphi_{\text{e}} \) of LBL columns is proposed. The calculation results obtained from the equations give a good agreement with the test results.     

竹板增强单板层积材组合梁受弯性能

单板层积材加工成梁构件应用于建筑结构材时,由于材料本身的强度和刚度不足,其结构构件不能满足现代多、高层以及大跨度建筑的需求。竹集成材是原竹经过切削成竹片、低温干燥、碳化、涂胶,再同方向平面或侧面组坯、热压胶合而成的竹基复合材料,其力学性能与稳定性优于木材。将集成竹材作为增强材料用于加固单板层积材梁是一种简单有效的提高梁极限承载力的方法。通过进行竹板增强单板层积材组合梁四点弯曲试验,研究了集成竹板对单板层积材受弯性能的增强效果。结果表明,在单板层积材受弯构件上下部粘贴集成竹板可提高构件极限承载力10%～50%。同时,考虑单板层积材和集成竹材料的非线性,推导出了适用于组合梁的极限承载力计算公式,计算结果与试验结果吻合良好。     

Development of structural composite products made from bamboo I: fundamental properties of bamboo zephyr board

A study was conducted to determine the suitability of zephyr strand from moso bamboo (Pyllostachys pubescens Mazel) for structural composite board manufacture. Thirty-two 1.8×40×40cm bamboo zephyr boards (BZB) were produced using four diameters of zephyr strand (9.5, 4.7, 2.8, and 1.5mm) and four target densities (0.6, 0.7, 0.8, and 0.9g/cm³). Results indicate that BZB exhibits superior strength properties compared to the commercial products. The size of the zephyr strand and the level of target density had a significant effect on the moduli of elasticity and rupture, internal bond strength, water absorption, and thickness swelling, but they did not have a significant effect on linear expansion. With regard to the physical properties, BZB exhibited less thickness swelling and exhibited good dimensional stability under dry-wet conditioning cycles.Part of this research was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 1998; it was reported at the 4th Pacific Rim Bio-Based Composite Symposium, Bogor, Indonesia, November 1998     

单板厚度对小径柚木单板层积材力学性能的影响

采用3.00、4.50、6.00mm厚度小径柚木单板制备单板层积材(LVL),研究单板厚度对单板层积材力学性能的影响。结果表明:单板厚度对于层积材静曲强度和弹性模量有显著影响,随着单板厚度增加,静曲强度与弹性模量减小;强度均达到GB/T20241—2006《单板层积材》中不同等级要求。生产相同厚度单板层积材时应根据耗胶量与所需力学强度选择合适单板厚度,寻求成本与质量的平衡。     

不同因素对竹/木复合强化单板层积材MOE、MOR的影响

以杨木单板和竹帘为原料,采用低分子量水溶性酚醛树脂浸渍处理,通过干燥、组坯、热压等工艺制备竹木复合强化单板层积材。探讨了组坯方式、压缩率、热压温度、热压时间4个因素对竹木复合强化单板层积材弹性模量(MOE)和静曲强度(MOR)的影响。结果表明:表层为一层竹帘的竹木复合强化单板层积材的MOE和MOR较大,分别是13．43GPa、148．13MPa,与表层为杨木单板次表层为竹帘组坯方式相比分别增加了33．63％、56．16％。确定了竹木复合强化单板层积材较合理的制造工艺参数。     

竹木复合单板层积材制备工艺

以浸渍酚醛树脂的杨木单板和竹帘为原料制备竹木复合单板层积材, 探讨制造工艺对复合材料性能的影响.结果表明,竹木复合材料的MOE及MOR均达到或超过了日本JAS标准的相关规定,尺寸稳定性良好; 单板厚度、树脂浓度、压缩率对MOE和MOR有显著影响;组坏方式对MOR影响显著;而吸水厚度膨胀率的影响作用比较复杂.     

Outdoor exposure tests of structural laminated veneer lumber (II): evaluation of the strength properties after nine years

To investigate the durability of structural laminated veneer lumber (LVL), outdoor exposure tests have been conducted since 1990 at a field-testing site at the Forestry and Forest Products Research Institute. This article is the second interim report on the results after 9 years of exposure. Seven kinds of structural LVL with no preservative treatment were subjected to the tests. Almost all the exposed specimens were decayed by a kind of brown rot fungi (Pseudomerulius aureus (Fr.) Julich). The degree of decay varied with wood species; grand fir and western hemlock LVL in particular showed weak resistance against the decay. All the specimens were stored for more than 1 year in a testing room conditioned at 20°C and 65% relative humidity. We then measured the ultrasonic velocity of the specimens by the Pundit method, penetration depth by the Pilodyn method, and bending strength by a conventional bending test. Correlation between nondestructive measurement factors and the density was strong even on LVL with many adhesive layers. The nondestructive testing method was found to be applicable to LVL as well as solid lumber. After the nondestructive measurements, each LVL was cut into three types of specimen (top: T, middle: M, and bottom: B) for the bending tests. The bending strength varied with the type of specimens. Correlation between modulus of elasticity and modulus of rupture was strong even in the decayed specimens.     

Dimensional stabilization of compressed laminated veneer lumber by hot pressing in an airtight frame

Abstract

The purpose of this study was to evaluate the dimensional stability and strength properties of compressed laminated veneer lumber (LVL) produced using a closed hot pressing system. LVL specimens were produced with varying number of veneers using either diphenylmethane diisocyanate (MDI) or a water-soluble phenol formaldehyde (PF) resin at varying temperatures (160–200°C), pressures (0.5–3 MPa) and hot-pressing times (2–16 min). Results show that the heating process decreases the recovery of compressive deformation in the veneers when subjected to cyclic moisture and heat conditions. Thickness swelling was approximately 5% after a drying, wetting and boiling cyclic test for LVL using the MDI resin and hot pressed at 200°C for 8 min. Modulus of elasticity and rupture increased for samples produced in both an open press and the closed press with an increase in the number of veneers and density, as did the absorbed energy in impact bending.     

大跨度竹质方梁的制备与抗弯性能研究

为了探究木质材料在大型建筑应用的可行性,以竹材为原料,利用层积热压组坯的方式制备长度为3 m和6 m的竹质方梁,对其进行四点抗弯测试,观察其在测试过程中的弯曲变形及破坏特征,分析弹性模量、静曲强度,根据其破坏形式分析竹质方梁结构及组坯方式对其抗弯性能的影响。结果表明:6 m竹质方梁弹性模量达10261.24 MPa,跨中竖向位移至86.97 mm而不破坏;3 m竹质方梁静曲强度达85.51 MPa。竹质方梁破坏均出现在弯曲的受拉面,且裂纹通过竹节处、胶合界面以及竹纤维排布方向蔓延,这与竹材本身结构特性有关。通过对3 m和6 m竹质方梁抗弯实验及分析,以期为竹质方梁在大跨度下的应用提供数据支撑。     

Development of LVL frame structures using glued metal plate joints I: bond quality and joint performance of LVL-metal joints using epoxy resins

Bond quality and joint performance between laminated veneer lumber (LVL) and metal plates were investigated. Commercially fabricated LVL made of Douglas fir veneer and bonded with phenol-formaldehyde resin as well as three types of epoxy adhesives were used. Various surface preparations and treatments were applied to ordinary steel, stainless steel, and aluminum plates to remove the weak boundary layer that is incompatible with the resin and form a stable adherend layer that is chemically and mechanically compatible with the resin. Small specimens were tested in shear to search the most suitable metal surface for bonding with LVL. Generally, shear strength obtained for the specimens bonded with aluminum plates was lower than those bonded with ordinary steel plates. Among them chemically treated (ChT) and roughened (R) surfaces have demonstrated superior performance. To investigate strength performance and bond quality, LVL beams jointed with metal plates were tested while bending. The best results were obtained for specimens bonded with zinccoated metal plates, though good results were obtained also for ChT and R plates. However, the fracture proved to be fragile when no drift pins were used, even for high-performance surface treatments. The usage of drift pins was necessary to add toughness and avoid the brittle status of the fracture.     

三种典型竹质工程材料纵向弹性模量评价

以重组竹、竹束单板层积材（BLVL）、竹集成材为代表的竹质工程材料受到越来越多的关注和应用。文中采用超声波法、自由横向振动法和力学法分别对上述3种典型竹质工程材料的纵向动态弹性模量（MOE）进行评价比较,结果表明,横向自由振动法能较为快速、准确和无损地评价出竹质工程材料的MOE,MOE的变异系数与其自身铺装结构有关;重组竹、BLVL和竹集成材的一阶共振频率分别为455.73、380.41和487.62 Hz;超声波在竹集成材的纵向上传播速度最快,重组竹其次,BLVL最慢;三点弯曲力学测试发现3种竹质工程材料的断裂模式不同,全顺向的重组竹为竹纤维拉断和界面剪切破坏,纵横组坯的BLVL为横向竹束拉断以及竹/木复合界面分层,而更多体现实竹性能的竹集成材为底层竹材维管束拉断和拔出破坏,其断裂载荷为重组竹> BLVL >竹集成材,而断裂位移为竹集成材> BLVL >重组竹。     

国外结构人造板研究现状与发展趋势

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。     

密实型杨木强化单板层积材制造工艺及应用前景分析

介绍了杨木强化单板层积材的制造工艺。杨木强化单板层积材的压缩率约为15％～40％，其硬度、抗弯强度、耐水性、尺寸稳定性等指标远高于普通单板层积材，可作建筑用木梁、立柱、水泥模板、家具、门窗、地板、车厢板、集装箱板等多种材料。它是一种很好的结构用材，市场前景十分看好。     

Finger joint performance of structural laminated bamboo member

The structural performance of finger-jointed laminated bamboo was investigated for two bamboo species by considering the finger length, profile orientation, lamination direction, culm growth height, and mechanical properties of bamboo materials. Based on the growth height variation and bamboo species, the best finger-jointed laminated bamboo was found for the lamina processed from the middle growth height of a moso bamboo culm with the finger profile shown on the width face of the beam. It was 38.7% higher in bending strength than the lowest group, with the lamina from the lower ma bamboo culm showing the finger profile on the thickness face of the beam. When considering the finger length and lamination orientation, the strongest finger-jointed laminated bamboo joined with an 18-mm finger, showing the finger profile on the width face of a vertically laminated beam was 50.1% higher in bending strength than the lowest group having a 12-mm finger showing the finger profile on the thickness face of a vertically laminated beam. The laminated ma bamboo showed higher finger-joint efficiency, 11.6%, than moso bamboo, and the members showing the finger profile on the width surface was 12.3% better in joint efficiency than that showing on the thickness surface of the beam.     

Properties of red maple laminated veneer lumber impregnated with waterborne micronized and two soluble copper formulations

ABSTRACT

Certain important quality parameters of red maple (Acer rubrum) laminated veneer lumber (LVL) impregnated with three waterborne formulations: copper azole (CA-B), micronized copper azole (MicroCA or MCA) and alkaline copper quaternary (ACQ-D) bonded with phenol formaldehyde or cross-linked polyvinyl acetate (XPVAc) adhesives were evaluated. Pre-dipping of veneers before LVL production and two post-manufacturing procedures, viz., vacuum-pressure and post-dipping of LVL, were applied. Maximum copper retention in pre-dip-treated, vacuum-pressure and post-dip-treated LVL was 1.4, 9.7 and 1.7?kg/m³, respectively. Copper retention in MCA-treated LVL was relatively lower than soluble formulations. Various physical, mechanical and bonding properties of treated LVL such as density, water absorption, swelling, flexural properties, hardness, tensile shear strength, delamination and wood failure (%) were studied and compared with untreated LVL. Little to negligible deleterious effect was observed on properties of LVL due to these chemical treatments. Analysis of variance results showed that most of properties of red maple LVL were not significantly different compared with those of untreated LVL. Therefore, vacuum-pressure impregnation process can be used to treat the red maple LVL with novel micronized copper formulations for increasing the service life of such products against biodegradation without affecting techno-mechanical quality parameters.     

Resistance of bamboo scrimber against white-rot and brown-rot fungi

ABSTRACT

Bamboo scrimber is one of the most emerging structural materials for future building applications and it possesses properties comparable to other natural wood-based engineered materials such as glulam, laminated veneer lumber and cross-laminated timber. The goal of this work was to study the decay resistance of bamboo scrimber against white-rot (Trametes versicolor) and brown-rot fungi (Serpula lacrymans). Bamboo scrimber samples were incubated in petri dishes with the wood-decaying fungi and the weight loss after 12 weeks was measured. The surface morphology of fungal-degraded bamboo scrimber was evaluated using optical microscopy. Based on the percentage weight loss, bamboo scrimber could be classified as highly resistant against bio-deterioration by white and brown-rot fungi.     

单板层积材喷蒸热压的初步探讨

探讨了喷蒸热压制作杉木单板层积材的工艺。研究了热压温度、热压时间、喷蒸时间和涂胶量对单板层积材性能 的影响。结果表明,喷蒸热压可有效缩短杉木单板层积材的热压时间,且制品性能较好。     

Comparative study on physical and mechanical properties of laminated veneer lumber and plywood panels made of wood from fast-growing <Emphasis Type="Italic">Gmelina arborea</Emphasis> trees

Laminated products, such as laminated veneer lumber (LVL) or plywood (PW), have become important recently. The objective of this study was to determine and compare properties of panels fabricated with veneers of Gmelina arborea trees in a fast-growth plantation and glued with phenol formaldehyde resin. The results showed that LVL and PW physical and mechanical properties are comparable to those of solid wood with a specify gravity of 0.60. Moreover, these panels can be cataloged into group 2 of PS 1–95 of the Voluntary Products Standard of the United States. The difference in physical properties was not statistically significant between LVL and PW panels, except for water absorption. Some mechanical properties, such as hardness and glue-line shear, modulus of rupture in perpendicular flexure, nail and screw withdrawal parallel, and perpendicular strength, were statistically different between LVL and PW. However, no differences were established for the modulus of elasticity, tensile strength parallel to the surface, or tensile strength perpendicular to the surface. The differences were attributed to the venners’ orientation in the panels studied.     

Properties of parallel strand lumber from Calcutta bamboo (<Emphasis Type="Italic">Dendrocalamus strictus)</Emphasis>

The objectives of this work were to analyze the physical and mechanical properties of parallel strand lumber (PSL) made from Calcutta bamboo. Based on the surface characteristics (Ahmad and Kamke 2003) and physical and mechanical properties (Ahmad and Kamke 2005) observed in previous work, a prototype PSL from Calcutta bamboo was manufactured and tested in the laboratory. Physical properties determined were dimensional stability and water absorption. The mechanical tests carried out were in compression and bending. Ultimate stress, stress at proportional limit, and modulus of elasticity were determined and compared to structural composite lumber (SCL) from several timber species produced by other researchers and manufacturers in the United States. The PSL produced was also exposed to accelerated aging process in order to assess its durability under extreme condition. PSL produced in the laboratory was stable in dimension. The mechanical characteristics compare favorably to SCL produced in other studies and SCL products available in the United States. The accelerated aging process was found to reduce the bending strength but no significant difference was detected in bending stiffness, and compression strength and stiffness. This is a promising indication of the suitability of Calcutta bamboo as raw material for structural composite products.