Engineered Wood/Bamboo Laminated Composites for Outdoor Hydrophilic Platforms:Structural Design and Performance

Landscape designers increasingly prefer to use wood/bamboo-based composites for outdoor hydrophilic platforms owing to their natural surface texture,high performance,and sustainability to facilitate extensive interaction between people and water and enable the full range of ecological functions of water resources.In this study,four laminated composite(LC)structures were designed and manufactured using fluffed bamboo and wood veneers.Their surface textures,profile densities,water resistances,and mechanical properties were then evaluated.The type of fluffed veneer of the surface layer determined the texture of the LC surface.The specific structures of fluffed bamboo and wood veneer laminations were found to affect the LC profile density variability,water resistance,and mechanical properties owing to the differences in the strength and interfacial properties of bamboo and wood fibers.Finally,the water resistance and mechanical properties of all four LCs were found to be much higher than the highest level specified in GB/T 20241-2006 for“laminated veneer lumber”and GB/T 30364-2013 for“bamboo scrimber flooring”,indicating that they are promising materials for structures and flooring,particularly for outdoor hydrophilic platforms.

Effect of Extractive-Dissolving Treatment on the Characteristics of Laminated Wood Assembled from Oily Keruing Wood

Utilization of oily keruing wood for laminated wood product has not been optimal yet because of the appearance of extractive substance as oil on wood surface and hence disturbing the bonding process. A study has been conducted by manufacturing laminated wood from oily keruing wood （Dipterocarpus hasseltii） after extracting its oil by boiling the wood in the mixture of water and ethanol solution in several proportions. The assessment on the treated wood and the resulting laminated wood covered some characteristics i.e., wettability, static bending, bonding strength, ethanol-water solution can improve wetting properties significantly and delamination. The results show that boiling treatment in The extractive does not affect mechanical characteristics of the laminated wood. Increasing of water proportion in ethanol-water solution causes the decreasing of the bonding strength and increasing delamination value of the laminated wood. The result also shows that oily keruing wood after the treatment can be used as material for laminated wood.

The effect of number of joints on bending properties of laminated lumber made from poplar (Populus nigra)

Connection plays an important role in structural components and end jointing is one of the most common connections in structural applications. This study was designed to investigate some mechanical properties （MOE and MOR） of solid wood samples manufactured from poplar （Populus nigra）, joined together through end jointing. As well, we studied combinations of lumber manufactured from 10-mm veneer, using a polyvinyl acetate adhesive. The results show that non-jointed lumber （control samples） have better bending properties （MOE and MOR） than jointed specimens and lumber made from laminated layers. On the whole, side-by- side joints have a negative effect on the MOR and MOE of laminated products, which is more pronounced in the MOR. By increasing the number of joints, the properties of combination of three-ply, i.e., bending strength and modulus of elasticity, decreased.

Performance of Densified Wood Glulam as Building Bio-Material

In this research,some practical aspects of densified wood glulam were investigated.For this aim,poplar wood specimens were densified by hygro-thermo-mechanical technique.Glulam specimens were produced by finger joint technique and polyurethane glue was used as resin.Physical and mechanical properties of glulams were investigated according to ASTM D 143-09,ASTM D 905-03 and ISO 8375 standards.Based on obtained results,using this process(steam and pressurize compaction)resulted in improvement of physical and mechanical prop-erties of glulam specimens.Optical microscopic and scanning electron microscopic(SEM)pictures were proved structural changes on wood material during of applied technique.Generally,the increase of wood density and hygrothermal treatment has a positive role on the glulam properties especially its dimensional stability.This tech-nique showed a significant effect on water absorption;the steaming temperature and holding time significantly decreased water absorption but densification process increased this parameter.Also,delamination of specimens was decreased by hygrothermal treatment while densification showed negative effect on delamination.Moreover,modulus of rupture,modulus of elasticity,shear strength and compression strength parallel to grain were decreased by this technique but it is depend to treatment temperature and holding time.Higher temperature and holding time cause to higher decrease in the glulam mechanical strength.

Mechanical Analysis of Sisal Fibers to Use as a Reinforced Material in Wood Beams

Natural fibers have recently raised attention for presenting adequate mechanical characteristics for reinforcement of structural elements. The use of both natural fibers, in especial Sisal fibers, in wood laminated beams and also wood from reforestation, is in accordance with the current economic interest and ecological appeal. Specifically, the strengthening of wood laminated beams with Sisal fibers is more effective for structures that require an increase in their structural capacity without a significant increase in height of the cross section. Furthermore, it is recommended that this type of reinforcement is used in wood structural elements where the elastic modulus is at least equal to the Sisal fibers. The composition of Sisal fibers is basically of cellulose, lignin and hemicelluloses. In particular, the amount of cellulose and the angle that the micro-fibers with the axis of the fiber characterize the failure strength and the modulus of elasticity. The average mechanical characteristics of the Sisal fiber are： tensile strength 347 to 378 （MPa） and elastic modulus 15.2 （GPa） whereas these properties are lower for strips of Sisal fibers. In this context, this paper deals with the analysis and the viability of the use of Sisal fibers in wood structures as a reinforced material.

高温预处理对杨木正交胶合木剪力墙抗侧力性能的影响

[目的]研究往复荷载作用时国产速生杨木正交胶合木(CLT)剪力墙的抗侧力性能,阐明木材高温预处理和加速老化对剪力墙抗侧力性能的影响,为高温改性技术和国产速生木材在建筑结构中的高效利用提供参考。[方法]以木结构建筑常用的进口欧洲云杉规格材为对照,以相同强度等级的国产速生杨木为研究对象,选用180℃为预处理温度对杨木进行高温改性,制备5面全尺寸正交胶合木剪力墙,开展往复荷载作用时加速老化前后正交胶合木剪力墙的抗侧力性能试验。[结果]与相同层板强度等级的欧洲云杉正交胶合木剪力墙相比,往复荷载作用时未处理杨木正交胶合木剪力墙的极限承载力、弹性抗侧刚度、耗能能力分别降低5.8%、12.9%、8.0%;木材经高温预处理、墙体经加速老化或二者联合处理后,杨木正交胶合木剪力墙的抗侧力性能指标不同程度降低;与未处理杨木正交胶合木墙体相比,加速老化处理后,墙体的极限承载力、弹性抗侧刚度、耗能能力分别降低9.4%、9.7%、11.2%;木材经高温预处理后,经加速老化,墙体的极限承载力、弹性抗侧刚度、耗能能力变化较小,分别降低2.9%、2.4%、5.0%。[结论]往复荷载作用时,国产速生杨木正交胶合木剪力墙的抗侧力性能略低于相同层板强度等级的欧洲云杉正交胶合木剪力墙,水平力作用时二者具有相似破坏模式,均为抗拔连接件节点处钉子被剪断;木材经高温预处理、墙体经加速老化或二者联合处理后,杨木正交胶合木剪力墙的破坏模式均为底部墙角抗拔连接件处木材被拉断或劈裂破坏;木材高温预处理能够有效降低加速老化对剪力墙抗侧力性能的影响,具有相对较好的抗老化能力;建立正交胶合木剪力墙极限承载力计算模型,理论值与试验值误差小于10%。

竹集成材-SPF复合正交胶合木的研发及性能评估

运用相同工艺分别制备足尺垂直型竹集成材-SPF复合CLT(简称V-BWCLT)与足尺水平型竹集成材-SPF复合CLT(简称H-BWCLT)。依据国内外相关标准对两种BWCLT的胶层剪切强度、胶合耐久性、抗弯弹性模量(MOE)、抗弯强度(MOR)和层间剪切强度进行了测试,并用三维非接触式应变测量系统(DIC)对抗弯和层间抗剪试验过程中的受力变形情况进行记录。结果表明:在相同制备工艺条件下,两种BWCLT平均胶层剪切强度接近,浸渍剥离率均可达到相关标准要求。V-BWCLT的平均MOE与MOR分别为7941 MPa和56.7 MPa,而H-BWCLT的平均MOE与MOR分别为10144 MPa和54.0 MPa,H-BWCLT比V-BWCLT具有更高的弯曲刚度,但两者MOR较为接近。对比SPF-CLT,两种BWCLT的抗弯强重比均有显著提高,上述研究和分析为新型竹木复合CLT的实际工程应用提供了设计参考与理论依据。

LVL结构调控及应用研究进展

在我国木材资源紧缺、人工林材质较差、而竹材资源较为丰富的背景下,单板层积材(Laminated Veneer Lumber,LVL)作为一种生物质工程材料,具备高效利用现有资源的优势,并且以其出色的力学性能可实现标准化、系列化生产,展现出广阔的应用前景。本文结合我国人造板产业的发展现况,概述了LVL的起源和发展,着重从复合材料力学性能的角度分析了LVL的结构特点,对单板分等和LVL组坯特点进行了介绍。同时,综述了酚醛树脂浸渍和纤维材料复合两种LVL增强方式。最后,对比讨论了国内外LVL的评价标准,并针对我国木结构建筑产业的发展现状和LVL应用过程中存在的问题,提出了若干建议。

浸渍纸层压实木复合地板耐水工艺研究

采用单因子试验方法,分步探讨了薄型高密度纤维板(HDF)的吸水厚度膨胀率、面板覆贴工艺、胶合板基材结构、面板与基材热压工艺及封边工艺对浸渍纸层压实木复合地板耐水性能的影响。研究结果表明,通过优化薄型HDF的吸水厚度膨胀率、面板覆贴工艺、改进胶合板基材表层结构和面板与基材热压参数、筛选合适的封边涂饰工艺,可以显著提升浸渍纸层压实木复合地板的耐水性能,使地板的吸水厚度膨胀率降低至6%以下,有效减少地板在潮湿环境下出现鼓包的问题。

现代木结构在高层观景塔中的设计研究——以第七届全国高等学校木结构设计竞赛获奖作品为例

高层建筑与构筑物是现代木结构自21世纪以来新的应用领域,在科技、生态与人文精神并重的时代背景下,对此进行研究具有十分重要的现实意义。因此,文章从第七届全国高等学校木结构设计邀请赛获奖作品——“鱼·跃”着手,通过研究现代木结构在高层观景塔的应用,对正交胶合木(CLT)筒中筒结构体系在其中的设计全过程进行解析,初步探索了现代木结构在高层构筑物建筑设计中带来的空间和造型的新变化。

CLT发展现状与展望

在“双碳”和生态文明背景下,木质建筑材料作为一类环保型建材,具有绿色可再生、低碳、可持续发展的优势,是实现我国“双碳”目标的重要助力。本文介绍了一种典型的木结构建筑材料——正交胶合木的特点和发展现状,讨论了目前存在的问题,并对正交胶合木的未来发展进行了展望。

一起换流变压器试验故障诊断和分析

针对一起换流变压器试验故障,结合多种试验排查进行变压器故障分析与定位,通过内部检查确定了内部放电故障的位置为阀3.2引线出线层压木螺杆。根据试验现象、排查情况以及对螺杆的材质分析,确认螺杆内部异物是导致故障的根本原因。

碳纤维/层状木材陶瓷的制备与力学性能

为了提升木材陶瓷的力学性能,用液化木材、炭粉和碳纤维等制备增强型层状结构木材陶瓷。探讨了烧结温度、液化木材用量等因素对其结构和力学性能的影响。结果表明,增强型层状木材陶瓷层状结构清晰,摩擦性能良好,且在微观上部分保持了木材天然的孔隙结构特征。同时,增强碳纤维和层状结构的运用能够获得较高强度与较好韧性。当烧结温度为1100℃、炭粉与液化木材质量比为1∶0.75、胶合压力为3 MPa时,其抗弯强度、弹性模量、断裂韧性分别达到了53.90 MPa、2.58 GPa和1.69 MPa·m1/2,与普通木材陶瓷相比均有大幅度提高。

大豆基木材胶黏剂及其产业化应用

为了应对发达国家严格限制人造板甲醛释放量的法律法规,解决人造板甲醛释放量超标带来的健康危害,摆脱醛类胶对不可再生石化资源的依赖,开发了以豆粕为原料制备的环保大豆无醛胶。通过介绍豆胶的发展历程、粘接机理及改性研究进展、技术指标及应用工艺,表明豆基胶黏剂经过改性,完全可以用于胶合板、地板生产等领域,其产业化前景广阔。

胶合木设计制作与质量控制

胶合木是一种强质比高、美观、可降解的工程复合材,且被广泛应用于桥梁、建筑等工程领域。而落叶松在我国分布面广,蓄产量丰富且强度高,适合于木材的工业化加工利用。针对国内落叶松结构用胶合木制造及利用现状,结合工厂的制造试验情况,本研究从层板的选择、指接工艺、胶合工艺、组坯工艺、质量检验等方面介绍了胶合木生产工艺及其质量控制,简述了整个制造流程中的工艺参数和要求,为胶合木的工业化生产提供了依据。最后提出了胶合木制造在我国推广存在的问题及建议。

人工林杨木材性对单板层积材强度的贡献率

本文提出了衡量单板层积材强度中实木材性所占份额的贡献率概念，以揭示实木材性对单板层积材强度的贡献程度。以人工林杨木为对象，研究了实木材性对单板层积材强度的贡献率。结果表明，实木材性好或单板层积材中的单板较厚时，贡献率较高。材性较优的６９杨和材性居中的７２杨、材性较差的６３杨３个无性系杨木的平均贡献率分别为７４３４％、６７４８％、６４７２％，厚度为３５６５ｍｍ、２６１４ｍｍ、１５４５ｍｍ单板组配的单板层积材中的平均贡献率分别为７４００％、６７４８％和５８０６％。研究的６项强度性能中，杨木实木材性对抗剪强度、弹性模量和冲击韧性的贡献率较高，约为８０％。

实木家具与竹集成材家具典型结构与加工比较分析

从基材、结构、造型和工艺等方面对实木家具和竹集成材家具进行比较分析,以促进竹材资源的利用和家具的新产品的开发。竹集成材家具结构、工艺上可借鉴实木家具的特点,但因其基材本身有自己的特点,因而也有其特殊性。

竹木复合层积材结构及其性能

运用复合材料力学层合板理论对竹木复合层积材进行结构设计与试验。结果表明:以高密度竹帘胶合板为强化面层,马尾松板材为芯层,采用特殊的二次热压生产工艺,研制出的竹木复合层积材物理、力学性能良好,能够满足铁路平车地板对强度、耐候性、耐磨性、握钉力等性能的特殊要求。

集成板材加工工艺

本文介绍了利用东北9个常用树种、国产脲醛胶、聚醋酸乙烯酯乳液生产集成板材的加工工艺,并对其出材率、胶合性能进行了分析。

竹集成材家具木圆榫接合强度的研究

以福建南平建瓯所产的毛竹片和低甲醛脲醛树脂胶黏剂加工而成的竹集成材为基材,采用正交试验法研究木圆榫直径、木圆榫插入深度、木圆榫与板孔的配合过盈量对竹集成材家具木圆榫接合强度的影响。结果表明:木圆榫直径、木圆榫插入深度和木圆榫与榫孔配合过盈量3个因子对木圆榫接合强度均影响显著;增加木圆榫直径、提高木圆榫插入深度、适度加大木圆榫与榫孔配合的过盈量能显著提高木圆榫接合强度;综合考虑竹集成材家具木圆榫接合结构确定优化木圆榫接合强度因子为木圆榫直径10 mm,木圆榫插入深度19 mm,木圆榫与榫孔配合的过盈量+0.2 mm,这种木圆榫结构设计能使圆榫接合强度明显提高。