尾巨桉/金属板复合材料层间正应力分布特征的有限元解析

利用三层尾巨桉单板之间嵌入与两张性能相同的金属薄板组成五层尾巨桉单板/金属网层积复合材,并采用预实验优化的热压工艺参数压制成板。采用大型通用有限元分析软件ANSYS10.0构建了尾巨桉/金属网复合材料的有限元数值分析模型,模拟了尾巨桉/金属复合材料界面自由边附近与板材内部界面应力的分布规律,解明了最可能引起分层破坏的正应力的分布规律。主要结果与发现如下:(1)复合材料四层界面处三个正应力的二维应力场分布云图表明自由边附近出现奇异应力的分布特征,自由边处正应力σx的值最大,其最大值为99.72 MPa;(2)复合材料四层界面处三个正应力的三维应力场分布云图表明在四层界面处正应力的应力σx集中现象都最为明显,最大应力集中值可达280.0 MPa。     

生产工艺对巨尾桉/聚乙烯膜复合材料质量的影响

采用巨尾桉基材、胶合剂聚乙烯膜制备三层木塑复合材料,分析热压温度、热压时间、热压压力、施胶量这四个因素对复合材料胶合强度的影响。结果表明：在热压温度160℃、热压时间50s/mm、热压压力0.7MPa、施胶量为119g/m2的工艺条件下,巨尾桉/聚乙烯膜复合材料的胶合性能最优,能够达到II类胶合板标准。     

桉树木材旋切单板质量以及制造胶合板工艺的研究

对福建省主要桉树木材材性及其旋切单板厚度偏差、背面裂隙率进行检测分析,探讨木材旋切单板的适应性和制造胶合板的工艺并采用正交法优选最佳工艺参数。结果表明:尾叶桉单板背面裂隙率和单板厚度变动系数比尾巨桉小,尾叶桉用于旋切1.5 mm厚度单板质量较佳。尾叶桉木材制造胶合板较佳工艺参数:热压温度为130℃、单位压力为1.4 MPa、热压时间为1.35 min·mm-1、涂胶量为320 g·m-2。工艺条件对板材性能均有影响,桉树木材龄级对板材性能影响显著,随着桉树龄级的增大,板材性能有较大幅度提高,特别是静曲强度、弹性模量影响最为明显。     

不同树种木粉/PVC复合材料天然耐腐性对比研究

选用5种不同树种木粉与PVC制备木塑复合材料,通过人工模拟加速试验对比研究不同组别复合材料对采绒革盖菌和绵腐卧孔菌的天然耐腐性差异,采用扫描电镜(SEM)和水分吸附测试深入分析腐朽菌对复合材料微观形貌及界面结合的影响,结果表明:不同组别复合材料对彩绒革盖菌耐腐性排序为:杉木/PVC马尾松/PVC白千层/PVC枫香/PVC尾巨桉/PVC复合材料;对绵腐卧孔菌耐腐性排序为:杉木/PVC尾巨桉/PVC、白千层/PVC、马尾松/PVC枫香/PVC复合材料。腐朽菌菌丝可通过木粉和PVC树脂界面结合空隙处进入试样内部进行侵蚀,从而降低复合材料间的界面结合,使其水分吸附率明显增加。     

尾巨桉人工林林下植被多样性研究

对尾巨桉(3年生)与杉木(8年生)林下植被的调查表明:尾巨桉的林下植被29科49属53种,多于杉木林分,林下植被生物量与杉木持平.尾巨桉林的植物分布类型组成 与地带性植被亚热带常绿阔叶林相近;群落外貌体现了亚热带常绿阔叶林特征,群落各层次物种多样性表现为灌木层＞草木层＞藤本层＞乔木层.     

澜沧短周期巨尾桉工业原料人工林与其原生林林下植物多样性的比较

在云南省普洱市澜沧县选取7块3年生短周期巨尾桉工业原料人工林样地和7块其原生林对照样地,对其林下灌木层和草本层进行了调查,依此对其多样性指标进行了比较分析,结果表明,短周期巨尾桉工业原料人工林林下,共有植物94种,隶属46科,主要以一些阳性和半阳性植物为主,其中菊科和禾本科植物较为普遍。对照样地所反映的原生林林下,共有植物167种,隶属49科。短周期巨尾桉工业原料人工林林下生长的植物在其原生林林下几乎都有分布,但不是优势种。短周期巨尾桉工业原料人工林林下的Simpson指数和Shannon-Weiner指数及均匀度指数3个多样性指数均低于其原生林。短周期巨尾桉工业原料人工林林下各植物物种个体数量分布不均匀,优势物种较突出,而原生林林下各物种株数分布比较均匀,优势物种并不突出。     

尾细桉等5种桉树无性系生物量和能量的比较研究

对广东廉江石岭林场尾细桉等5种7.5年生桉树无性系的生物量和能量进行了研究。结果表明:不同无性系各组分生物量的分布规律均以干的最大、叶的最小,枝、根、皮介于中间;5种桉树无性系各组分的生物量排序为:赤桉、尾细桉、巨尾桉为干根枝皮叶,雷林1号桉为干根皮枝叶,尾叶桉为干枝根皮叶。人工林生物量现存量的排列顺序为尾细桉(161.60 t.hm-2)巨尾桉(127.96 t.hm-2)尾叶桉(112.60 t.hm-2)赤桉(83.81 t.hm-2)雷林1号桉(71.36 t.hm-2)。各组分的灰分含量各不相同,以叶最高(4.08%~6.88%),干最低(0.17%~0.43%)。不同组分的干质量热值介于17.94~21.06 kJ.g-1间,去灰分热值介于18.57~22.12 kJ.g-1间,均以叶的值最高。植株体的平均干质量热值和去灰分热值分别为19.02~19.32、19.49~19.85 kJ.g-1,平均干质量热值的排序为雷林1号桉尾叶桉尾细桉赤桉巨尾桉,平均去灰分热值的排序为雷林1号桉赤桉尾叶桉尾细桉巨尾桉。5种桉树无性系林的能量现存量为1 360.73~3 067.47G J.hm-2,大小顺序为尾细桉巨尾桉尾叶桉赤桉雷林1号桉。综合生物量和能量现存量分析,尾细桉选作能源树种最为理想,巨尾桉和尾叶桉次之,赤桉与雷林1号桉最差。     

不同林龄尾巨桉林植被碳储量分配格局

基于对5个林龄尾巨桉林分不同层次植被生物量和碳含量的测定,本文研究了5个不同林龄尾巨桉林分植被碳储量的分配格局.结果表明:5个不同林龄尾巨桉林分中乔木层、林下灌木层、林下草本层和凋落物层碳含量均值分别为47.64%、50.59%、44.41%和48.92%,碳储量为7.17~145.15 t·hm-2,随林龄增加而增大.乔木层碳储量所占比例最大,随林龄增加乔木层碳储量所占比例也逐渐增大.     

3种整地方式下尾巨桉林分生物量动态及其与土壤水分的关系

对3种整地方式下的尾巨桉林分生长和林地土壤水分进行了监测,通过分析各林地的林分单株平均生物量及林地土壤水分的变化,探讨二者的相互关系,以期为合理评估整地对尾巨桉林分生长和水分利用效率的影响提供科学依据。研究结果表明：随着林龄的增长,3种整地方式下尾巨桉林分单株总生物量和各器官生物量均呈增加趋势,其树干和树根所占比例逐渐增加,而树枝和树叶所占比例呈减小趋势。在幼龄期(16个月之前),全垦条件下的尾巨桉林分生长量最大,18个月后带垦的林分生长量最大;3种整地方式下的尾巨桉林地土壤水分的季节变化格局相似,与天然降水分布基本保持一致。3种整地方式中穴垦尾巨桉林地土壤有较高含水率且显著大于全垦和带垦的(P<0.05),全垦与带垦之间差异不显著;3种整地方式下尾巨桉林分单株平均生物量与耗水量之间均呈显著正相关,利用3块林分单株平均生长量及对应时间的耗水量得到了尾巨桉林分单株生长量与林分耗水量的拟合方程。     

基于ANSYS的硅酸盐/杨木胶合试件的拉伸受力分析

为预测和评价硅酸盐胶黏剂与杨木之间的胶合性能及界面作用力,利用有限元软件ANSYS模拟了胶合强度测试试件在拉伸载荷状态下的力学行为,分析在加载过程中试件的位移形变、剪切应力和应变分布情况,以及在胶层中心、垂直胶层和胶层界面方向上应力应变的分布规律,分析了胶黏剂类型、胶层厚度对胶合试件和胶层应力应变云图和曲线的影响,所得结果对胶合木制品的界面力学研究和胶合强度预测具有指导意义。     

竹胶合板——混凝土模板的构造与应用的研究

竹胶合板是我国最近开发的一种轻质、高强的代木材料。它的种类很多,其中用经纬编席坯板作胶合板的奇数间板,以帘吊内簧坯板作填层组合热压而成的毛竹经帘交压层积板,可以制作混凝土工程面板,以代替木材面板、钢面板以及其他材质面板。它既可与木材、钢材、工程塑料组成多种规格的模板体系;也可制成全竹胶普通模板。竹胶模板适应各种类型建筑工程的施工使用,安全轻便,装拆劳动强度小、工效高,施工经济效益好。     

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。     

响应面法在桉木LVL生产中的应用

采用响应面法（RSM）,研究了单板厚度和涂胶量对桉木单板层积材（L、几）力学性能的影响。结果表明：单板厚度和涂胶量对桉木LVL的垂直加载和平行加载条件下的静曲强度（MOR┷、MOR／／）和弹性模量（MOE┷、／dOE／／）有显著影响。实验值与预测值的决定系数为0．72,0．79,0．59,0．69。本研究所获最佳工艺条件为：单板厚度2．0啪,涂胶量233g·m＾-2在此工艺条件下压制的桉木单板层积材垂直加载条件下的静曲强度（MORJ和弹性模量（MOE上）分别为85MPa与15118MPa,平行加载条件下的静曲强度（MOR／／）和弹性模量（MOE／／）分别为87MPa与15288MPa,回归模型的预测值与实验值的相对误差最大为9％,最小为3％。实验产品的MOR和MOE分别达到结构用单板层积材国家标准的优等品和140E级别。     

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     

桉木基复合材料研究进展

桉树作为我国主要的人工林树种之一,具有品种多、生长速度快等优点,在缓解我国木材供 需矛盾上发挥了重要作用。由于桉木存在高生长应力、节疤、易变形开裂等劣势,目前工业上主要用作 纸浆、纤维板或胶合板和单板层积材的芯板,其利用方式单一,附加值较低。近年来研究者们以桉木与 塑料、竹材等材料为原料制备复合材料,展现出良好的尺寸稳定性、力学性能、阻燃性、抗菌性等性能, 有效地提高了桉木的利用价值,拓宽了桉木在人造板、集装箱等领域的应用。文章分别介绍了桉木 / 塑 料、桉木 / 竹、桉木 / 水泥、桉木 / 无机物 4 种复合材料,并对其制备工艺、性能等方面的研究进展进行 综述。     

Manufacturing of LVL using cost-effective resin impregnation and layup technologies

The purpose of this study was to develop a cost-effective method to manufacture high-performance laminated veneer lumber (LVL) from mountain pine beetle (MPB)-affected veneers through partial resin impregnation and optimum board layup. Dry MPB-affected veneer sheets were segregated into two stress grades based on dynamic modulus of elasticity (MOE). A new phenol formaldehyde resin with a 30% solids content was formulated for resin impregnation. To reduce resin consumption, only veneer sheets used as outer layers were dipped in the resin for 5?min and then dried to manufacture 13-ply LVL. The bending properties, shear strength and dimensional stability of these LVL billets were examined and compared to those from the controls made from entirely untreated veneers. The results demonstrated that high-grade (E1) MPB-affected veneers had lower resin solids uptake than low-grade (E2) counterparts based on a 5?min dipping. Compared with the controls, the LVL billets made from resin-impregnated veneers for outer layers yielded increased surface hardness, significantly improved dimensional stability, shear strength and modulus of rupture on both edgewise and flatwise as well as better appearance with no cosmetic concerns. However, the improvement in LVL bending MOE was dependent on initial veneer stress grade. For high-grade (or density) E1 veneers, the use of impregnated veneers resulted in insignificant improvement in bending MOE. The optimum product layup was to place one ply of impregnated E1 grade veneer each for product face and back. By contrast, for low-grade (or density) E2 veneers, the use of impregnated veneers yielded a significantly higher flatwise bending MOE compared to the controls. The recommended product layup was the placement of two plies of impregnated E2 grade veneer sheets each for product face and back.     

电工层压木中如何提高单板出板率

电工层压木板是一种新型绝缘材料,并早已被大规模用于变压器、互感器等电气制造业;它具有与变压器油相容性好、介损低、变形小等优点。本文主要介绍了在电工层压木板生产中单板出板率是一个重要经济指标并较详细地分析了其提高单板出板率的原理及工艺流程。     

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。     

Shear behaviour of laminated Douglas fir veneer

The rolling shear and longitudinal shear behaviour of laminated Douglas fir veneers was studied using specimens with 15 layers of 2.5 mm veneers. The rolling shear specimens were constructed such that the 3 central veneers were cross-plies with grain angle oriented perpendicular to the long axis of the specimen. The other layers were orthogonal to the cross-plies. The longitudinal shear specimens had a LVL lay-up with the exception of a reinforcement layer of fiber-glass attached to the bottom face veneer. The fiber-glass layer prevented specimens from failing in bending/tension mode and ensured longitudinal shear failures. Specimens were subjected to static and cyclic loads in a “flatwise” three point bending configuration. It was found that the rolling shear failure mode exhibited a higher fatigue resistance than the longitudinal shear failure mode. A damage model that took the stress history into account was calibrated to the experimental data of each specimen type. Good agreement between model predictions and experimental results were obtained for both failure modes. Received 5 November 1997