SYSTEMATIC STUDY OF PHYSICAL AND MECHANICAL PROPERTIES OF IMPORTANT CHINESE WOODS

In this paper,the physical and mechanical properties of important Chinese woodswere studied by using the methods of variable analysis, regression analysis,correlation analysis,principle component analysis and so on systematically.The results showed synthetical characteristicof the physical and mechanical properties of Chinese woods.Some opinions of former authors wererevised and some new laws were discovered.That is helpful to study of the physical and mechanicalproperties of woods.

Study on the Structural Characteristics and Physical and Mechanical Properties of Phoebe bournei Thinning Wood

The artificial afforestation of precious Phoebe bournei has been carried out in China.During the cultivation process,thinning wood will be produced.The properties of thinning wood might vary greatly with matured wood and require evaluation for better utilization.The objective of the present study aims to determine the wood structure,fiber morphology,and physical and mechanical properties of the Phoebe bournei thinning wood to help us understand the wood properties and improve its utility value.Three 14-year-old Phoebe bournei were cut from Jindong Forestry Farm of Hunan Province,China.The wood structure and fiber morphology were observed and analyzed with a light microscope and scanning electron microscope.The physical and mechanical properties were tested according to the Chinese national standards.The results showed as follows:(1)The Phoebe bournei thinning wood has a beautiful wood figure and fine texture,whereas the heartwood has not yet formed.(2)It is a diffuse-porous hardwood with small and less pores as well as fine wood rays.(3)The wood fiber is medium length and extremely thin wall thickness.(4)It is low in density and has excellent dimensionally stability.(5)The wood mechanical properties belong to the low to medium class and the comprehensive strength of wood belongs to the medium-strength class.It is concluded that Phoebe bournei thinning wood is suitable for wood carving,handicraft,high-end furniture,and decorative furniture parts.

COMPARATIVE STUDY OF WOOD PROPERTIES BETWEENWHITE WOOD OF DAHURIAN LARCH AND MONGOLIANSCOTCH PINE

The comparative result shows that the physical and mechanical properties of wood between white wood of Dahurian larch (Larix gmelini (Rupr.) Rupr.) and Mangolian scotch pine (Pinus cylvesthe var. mongolica) are different Some differences are very conspicuous,(e. g. compressivc strength parallel to grain, modulus of elasticity in static bending, toughness and bending strength etc. ),and others are slightly conSPicuous or not conspicuous,(e.g. shrinkage, differential shrinkage and shearing strength parallel to grain etc.). The properties of white wood of Dahurian larch are suitable weight and soft texture, median strength,median shrinkage and good in worability, while which of Mongolian scotch pine are light and soft nearly very soft,weak strength, median shrinkage are good in workability. However, the white wood of Dahuran larch is superior to the Mongolian scotch pine in Strength-to-weight ratio.It is a valuable timber tree.

Production of mahogany sawdust reinforced LDPE wood–plastic composites using statistical response surface methodology

We produced wood–plastic composite board by using sawmill wastage of mahogany（Swietenia macrophylla） wood and low density polyethylene.We used multi-response optimization to optimize the process parameters of composite board production including mixing ratio,fire retardant（%） and pressing time（min）.We investigated the effects of these three process parameters in the mechanical and physical properties of the composite board.Afterwards,Box–Behnken design was performed as response surface methodology with desirability functions to attain the optimal level of mixing ratio,fire retardant and pressing time（min）.The maximum modulus of elasticity（MOE） and modulus of rupture（MOR） were achieved at the optimal conditions of wood plastic mixing ratio of60：40,pressing time of 9 min and zero fire retardant percentage.The optimized MOR and MOE were 13.12 and1,781.0 N mm-2,respectively.

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.

Some Properties of Bamboo Composite Lumber Made of Gigantochloa pseudoarundinacea

The objective of the study was to determine the effect of bamboo-wood layer compositions on the properties of bamboo composite lumber. Laboratory scale bamboo composite lumbers （BCLs） with four different core layer materials, i.e., bamboo strips glued vertically, jabon wood plank （Anthocephalus cadamba Miq.）, manii wood plank （Maesopsis eminii Engl.） and sengon wood plank （Falcataria moluccana （Miq.） Barneby ＆ J.W. Grimes） were fabricated using Andong bamboo （Gigantochloa pseudoarundinacea （Steud.） Widjaja） strips glued horizontally as the outer layers and Andong bamboo zephyrs used as the second and the fourth layers. BCLs were manufactured using water based polymer-isocyanate （WBPI） adhesive with the glue spread of 250 g/m2, and the cold pressing time applied was 1 h. Results showed that physical and mechanical properties of BCLs were significantly affected by the layer compositions. The BCL consisted of 100% bamboo strips exhibited higher density （0.754 g/cm3） and mechanical properties （modulus of rupture （MOR） 1,162 kgf/cm2, modulus of elasticity （MOE） 173,757 kgf/cm2, compression strength 644.7 kgf/cm2 and hardness 553 kgf）, compared to BCLs, of which the core layer was made of wood plank （density 0.533 g/cm3, MOR 648 kgf/cm2, MOE 77,893 kgf/cm2, compression strength 389.7 kgf/cm2 and hardness 355 kgf, respectively）. No delamination occurred in all samples, indicating a high bonding quality. BCL made of 100% bamboo strips had strength values comparable to wood strength class I, while BCL with core layer made of wood plank of jabon, manii or sengon had strength values similar to wood strength class III. All BCLs produced are suitable for solid wood substitute.

海南椰子木维管束形态特征及其与物理力学性能的关系

维管束是椰子木组织构造的重要组成部分,作为承重单元,维管束的形态特征影响椰子木的宏观物理力学性能。以树龄40 a的海南高种椰子木(Cocos nucifera)为材料,以径向和高度方向为考察因素,分析维管束的分布密度、直径、横切面面积和总面积占比在株内的变异规律,并探究维管束总面积占比与密度、顺纹抗压强度等物理力学性能指标的相关性。结果表明:不同树株间,除了维管束总面积占比、抗弯强度有显著差异外,维管束其他形态特征和物理力学性能指标差异均不显著。在径向从内部向外部,椰子木维管束的分布密度、直径、横切面面积和总面积占比逐渐增大,与径向位置呈高度线性正相关;椰子木的密度和顺纹抗压强度等物理力学性能亦逐渐增大,与维管束总面积占比呈高度线性正相关。在高度方向从底部向上,维管束的直径和横切面面积逐渐减小,分布密度和总面积占比先增加后减少,与高度位置呈显著或高度相关。基于维管束总面积占比指标建立椰子木物理力学性能的模型,模型预测结果可为椰子木下锯方法和锯材质量分等提供依据。

香合欢木材物理力学性质研究

为给香合欢(Albizia odoratissima)木材的综合利用提供参考,以25年生香合欢木材为研究对象,对其物理和力学性质进行测定。结果表明,香合欢木材的基本、气干和全干密度均值分别为0.635、0.761和0.727 g/cm^(3)。木材的径向、弦向和体积气干干缩率均值分别为1.53%、2.06%和3.72%,差异干缩为1.35;径向、弦向和体积全干干缩率均值分别为2.92%、5.09%和8.10%,差异干缩为1.74;径向、弦向和体积干缩系数均值分别为0.114%、0.272%和0.395%。木材的端面、径面和弦面硬度均值分别为6655、4968和5218 N。木材的抗弯强度、抗弯弹性模量、顺纹抗压强度和冲击韧性均值分别为136.7 MPa、12820 MPa、70.1 MPa和100 kJ/m^(2)。木材综合品质系数为3256.3×10^(5) Pa。香合欢木材干缩均匀性中等,尺寸稳定性较好,刚性中等,有较高的密度、硬度、韧性和品质系数及抗弯和顺纹抗压强度,为优良的高档家具用材。

糠醇-环氧植物油复合改性毛白杨木材的物理力学性能

【目的】采用糠醇-环氧植物油复合改性方法,改善糠醇改性降低木材韧性的问题,促进其在建筑结构领域的应用。【方法】将环氧大豆油和环氧亚麻油2种环氧植物油以不同添加量与糠醇溶液复配制备浸渍液,采用满细胞法处理毛白杨木材,获得不同环氧植物油添加量的糠醇-环氧植物油复合改性材。利用扫描电镜(SEM)和傅里叶红外光谱(FTIR)探究糠醇、环氧植物油在木材细胞结构中的分布规律,揭示其化学反应关系。分析复合改性材的力学性能变化,优选适宜增韧剂添加量。【结果】复合改性材SEM观察并结合其增重率和密度测试结果(显著增加)证明,糠醇树脂和环氧植物油可浸渍到木材细胞结构中。FTIR分析表明,环氧植物油与糠醇发生开环反应。与糠醇改性材相比,环氧大豆油添加量为20%(质量分数,下同)时,复合改性材气干/吸水饱和的弦向和体积湿胀率降低幅度最大,分别降低36.9%、20.0%和35.9%、30.7%,且抗湿胀系数(ASE)最大;环氧亚麻油添加量为40%时,复合改性材气干/吸水饱和的弦向和体积湿胀率降低幅度最大,分别降低52.5%、65.6%和41.5%、46.0%,且ASE最大,环氧植物油加入能够显著提高糠醇改性材的尺寸稳定性。环氧大豆油和环氧亚麻油添加量为20%时,复合改性材的抗弯强度(MOR)和静态硬度提高幅度最大,与糠醇改性材相比,分别提高17.9%、25.3%和30.0%、25.1%。环氧大豆油和环氧亚麻油添加量为40%时,复合改性材的抗弯弹性模量(MOE)提高幅度最大,与糠醇改性材相比,分别提高22.7%、21.1%。与其他力学性能相比,环氧植物油对糠醇改性材的韧性提高幅度最大。环氧大豆油和环氧亚麻油添加量为40%时,复合改性材的冲击韧性分别提高88.7%、59.8%。环氧植物油添加可显著提高糠醇改性材的MOE、MOR和静态硬度,改善其韧性下降问题。【结论】环氧植物油添加量20%的复合改性材物理力学性能最优。环氧植物油与糠醇发生开环反应,其长柔性脂肪链引入糠醇树脂链中可改善糠醇改性降低木材韧性的问题,且可进一步提高其物理力学性能。

古建用落叶松木材物理力学性能预测及其影响因素

为实现对木结构古建筑的预防性保护,有必要对木构件的材质性能进行及时有效的预测和评价。采取小试样-缩尺-足尺递进的方式,将微钻阻抗仪和应力波检测等无损检测方法与实验室物理力学性能测试相结合,构建并检验了落叶松木材物理力学性能与微钻阻抗值和波阻模量关系预测模型,进而提出了古建用落叶松木材物理力学性能的现场无损检测分析方法。研究结果表明:落叶松小试件密度与微钻阻抗值呈现明显的线性正相关关系,木材密度与微钻阻抗值线性方程相关系数为0.91;落叶松小试样顺纹抗压强度、抗弯强度及抗弯弹性模量与波阻模量呈现较明显的线性正相关关系,木材顺纹抗压强度、抗弯强度、抗弯弹性模量与波阻模量线性方程相关系数分别为0.86,0.74,0.74;通过微钻阻抗仪和应力波检测可推算落叶松木材物理力学性能。利用小试件测试数据所建立的预测方程进行落叶松大试件物理力学性能推算存在一定的误差,其缩尺试件密度和顺纹抗压强度预测值与实际值平均偏差分别为12%和16%,足尺试件密度和顺纹抗压强度预测值与实际值平均偏差分别为16%和17%。现场预测应同时考虑测试路径因素,自心材至边材区域,落叶松木材密度、顺纹抗压强度、微钻阻抗值沿径向表现为增大趋势,外层微钻阻抗值比整体平均微钻阻抗值大4%~16%。在古建筑木构件强度检测评估中,应进行木构件的整体微钻检测;若条件所限无法进行整体检测时,应针对不同树种的径向变化规律进行微钻阻抗值的修正。

薄壳山核桃木材主要物理力学性质研究

为了发挥薄壳山核桃(Carya illinoinensis)树种的多功能效应,弥补我国优质木材资源不足的现状,本研究以23年生的薄壳山核桃为研究对象,分别对木材密度、干缩性、抗压强度、弯曲强度、冲击韧性等物理力学指标进行测定,并分析其各物理力学性能在轴向上的变化以及各指标之间的相关性。结果显示:气干密度、顺纹抗压强度、抗弯强度、抗弯弹性模量、顺纹抗拉强度和冲击韧性分别为0.813 g·m^(-3)、51.7 MPa、108.2 MPa、11.39 GPa、167.8Mpa和121k J·m^(-2),综合强度为159.9MPa;抗弯强度、顺纹抗压强度、顺纹抗拉强度在轴向上变化呈现先增后减趋势,抗弯弹性模量在轴向上变化增长呈上升趋势,冲击韧性在轴向上变化呈递减趋势,说明树高对薄壳山核桃木材5个力学性质方面均有一定的影响;5个力学指标除抗拉强度外彼此之间都存在极显著相关,即4项力学指标之间相互关联。对木材材性进行综合评价结果表明薄壳山核桃木材材性优良,达到国产木材的高等级水平。

低共熔溶剂预处理对表面矿化木材性能的影响

【目的】为了解决木材矿化改性渗透难、矿化位点少等问题,本研究采用低共熔溶剂(DES)预处理速生杨木、打开木材渗透通道、构建活性位点,研究低共熔溶剂预处理对表面矿化木材性能的影响。【方法】本研究使用DES预处理杨木构建矿化位点,诱导SiO_(2)在木材表面实现原位矿化,再通过热压制备表面矿化木材,分析DES预处理对表面矿化木材物理力学性能的影响作用;以较优条件制备表面矿化木材,并分析其微观结构形貌和热性能。【结果】(1)表面矿化木材的密度、质量增长率和表面硬度均随DES预处理时间的增加呈先上升后下降的趋势;预处理为2 h时,较未处理材分别提高了35.25%、16.35%和51.53%;表面矿化木材的疏水性大幅提高,预处理0.5 h时初始接触角增大了74.08%。(2)DES预处理可以显著改善表面矿化木材力学性能;当DES预处理时间为2 h时,表面矿化木材的抗弯强度和弹性模量分别提升了20.53%和214.55%。(3)表面矿化处理向木材内引入SiO2形成有机–无机杂化结构,提高木材阻燃性能;DES预处理2 h时,表面矿化木材的质量残余率相较于未处理材提高了70.81%,热释放速率降低了69.9 kW/m^(2),总热释放量降低了27.3 MJ/m^(2)。【结论】速生杨木经DES预处理和表面矿化联合改性后物理力学性能提升,热稳定性和阻燃性能良好。

黑黄檀木材物理和力学性质研究

为了解黑黄檀木材的基础材性,以云南西双版纳的黑黄檀为研究对象,进行了主要物理和力学性质的测定和分析。结果表明,黑黄檀木材属高密度等级材,全干体积干缩系数小;顺纹抗压强度、抗弯强度、冲击韧性分别为60.13 Mpa、126.4 Mpa、80.82 kJ·m^(-2),对应强度等级分别为4级、4级、2级;端面、弦面和径面的硬度分别为105.38 Mpa、85.12 Mpa和87.15 Mpa,其中端面和弦面硬度属很硬等级,为高硬度木材;木材的综合强度为186.53 Mpa,属高强度树种;木材的品质系数达277.83 MPa,属于高等级材。

山桐子木材材性研究

【目的】对山桐子木材的解剖性质、物理力学性质及抽提物进行较为系统的研究,以全面了解山桐子木材的材性状况。【方法】以四川省古蔺县35年生山桐子为研究对象,按照相关的国家标准进行试验材料采集、年轮宽度测定和木材主要物理力学性质测定,采用永久切片法和离析法进行木材解剖性质的测定与分析,利用无水乙醇和乙酸乙酯对木材进行抽提,并对抽提物成分用气相色谱与质谱联用仪(GC-MS)进行分析。【结果】山桐子木材为散孔材,平均年轮宽度3.94 mm,最大宽度可达13.0 mm,属于优质速生用材树种。山桐子纤维形态指标平均值分别为:长度1420.12μm,宽度32.51μm,腔径14.40μm,双壁厚5.57μm,长宽比43.68;导管形态指标平均值分别为:长度594.34μm,宽度89.86μm,腔径72.22μm,双壁厚7.58μm,长宽比6.96。山桐子的气干密度为0.44 g/cm 3,质地轻软,干缩率小,从气干到绝干,径向、弦向、轴向干缩率分别为1.61%,3.52%和0.44%;从湿材到绝干,径向、弦向、轴向干缩率分别为3.29%,6.91%和0.89%。山桐子木材端面、径面、弦面硬度的平均值分别为3377.39,1814.09和1903.64 N,顺纹抗压强度为35.07 MPa,抗弯强度为64.52 MPa。山桐子木材心材、过渡层、边材无水乙醇抽提物的质量分数分别为0.25%,0.75%和1.15%,其中最主要成分为2,2′-亚甲基双-(4-甲基-6-叔丁基苯酚);山桐子木材心材、过渡层、边材乙酸乙酯抽提物的质量分数分别为0.56%,1.29%和0.75%,其中主要成分为2,4-二叔丁基苯酚和γ-谷甾醇,此外还含有少量的醇类和酯类物质。【结论】山桐子木材呈黄白色-浅黄褐色,质地轻软,木材尺寸稳定性较好,易干燥,但抗压和抗弯强度较小,内含物含量较少,适用于制造纸浆或纤维板、胶合板、刨花板等人造板材,也可作为实木装饰材料,但不适宜用作承压构件和弯曲结构构件。

不同无性系刺槐生长、材性及适用性

【目的】通过对刺槐不同无性系林木之间生长、材性和适应性的研究,为刺槐建筑用材林培育选用优良无性系和刺槐优质木材的加工利用提供科学的依据。【方法】以河南省洛宁县国有吕村林场无性系试验林中的豫刺1号、豫刺2号、豫刺7号、豫刺8号、无性系3-Ⅰ共5个刺槐无性系为研究对象,分析林木生长过程,比较林木生长及材性差异并进行适用性评价。【结果】5个无性系胸径大小排序为无性系3-Ⅰ>豫刺1号>豫刺8号>豫刺7号>豫刺2号;材积大小排序为无性系3-Ⅰ>豫刺1号>豫刺7号>豫刺8号>豫刺2号。其胸径、树高均呈现前期生长迅速后生长逐渐减缓趋势。其木材气干密度、全干密度、基本密度测量范围为0.769~0.812、0.731~0.775、0.644~0.673 g·m^(-3);干缩率中气干差异干缩和全干差异干缩变化幅度分别为1.41~1.82、1.47~1.62;湿胀率中全干至气干湿胀率(径向、弦向、体积)、全干至饱水湿胀率(径向、弦向、体积)分别在2.34%~2.67%、3.23%~3.59%、5.88%~6.73%、5.1%~5.81%、8.05%~8.67%、13.77%~15.23%之间;力学性质中顺纹抗压强度、横纹全部抗压强度(径向、弦向)、抗弯强度、抗弯弹性模量测量值范围分别为53.44~58.89、12.00~15.46、14.23~18.11、107.386~122.299、9737.701~10410.325 MPa。【结论】5个无性系刺槐中最适合作为结构用材原料的是无性系3-Ⅰ;最适合作为装饰用材原料的是豫刺7号。

新疆杨木物理力学性能研究

为全面掌握新疆杨木的性质,对新疆杨木的物理性能和力学性能进行试验研究测定、分级、评价。结果表明:新疆杨木木材的基本密度、气干密度以及绝干密度分别为0.380g/cm~3、0.409g/cm~3和0.392g/cm~3;试样从常温状态至600℃、800℃、1000℃这3个温度梯度状态,体积干缩率分别为2.73%、1.58%和0.72%;属低等密度、在较高温度环境下表现为干缩性小的木材;抗弯强度、抗弯弹性模量、径向抗剪强度、弦向抗剪强度分别为41.23MPa、8.456GPa、8.81MPa、9.11MPa;木材综合强度为71.8MPa,属低级强度木材。

闽楠天然林与人工林木材物理力学性质研究

对闽楠人工林和天然林木材物理和力学性质进行了测定和比较分析,结果表明:闽楠天然林木材气干密度和全干密度分别为0.721 g.cm-3和0.680 g.cm-3,人工林木材气干密度和全干密度分别为0.572 g.cm-3和0.535 g.cm-3,闽楠天然林木材密度大于人工林且差异达到极显著水平,但人工林木材密度变异系数却小于天然林。闽楠人工林和天然林木材气干状态下体积干缩率分别为4.935%和6.439%,全干状态下分别为9.330%和11.376%,闽楠人工林木材的尺寸稳定性稍差于天然林,但从木材的差异干缩来看,闽楠天然林和人工林相近,分别为1.75和1.76。闽楠天然林木材端面、径面和弦面硬度分别为7 583 N、6 183 N和6 625 N,稍大于人工林,但差异不显著。闽楠天然林与人工林旋切板背面裂隙率分别为53%和67%,单板厚度的偏差人工林和天然林分别为0.08mm和0.09 mm。由此可知,发展闽楠人工林可以得到质量与闽楠天然林相近的板材。

人工经济林木材性质研究

对重要人工经济林树种核桃、枣木、银杏、板栗、樟树和橡胶等木材解剖、物理力学、化学性质进行研究。结果表明 :核桃、银杏、樟树生长速度较快、材质好 ,是培育经济和用材两用林的优良树种 ,枣木和板栗材质好、生长慢 ,可以选择经济林果用为主、材用为辅的培育方式 ;核桃、橡胶、樟树和银杏的密度和力学强度较大 ,板栗和枣树木材的密度和力学强度很大 ;樟树、银杏和橡胶木材的纤维素含量与杨木接近 ,木质素含量界于杨木和马尾松之间 ,且纤维形态特征符合造纸用材的要求 ,树干和加工剩余物可以用于造纸 ;人工经济林枣木基本密度、核桃木材纤维长度可以通过生长轮年龄来预测 ,且预测效果显著。

间伐强度对湿地松人工林木材质量的影响效应

湿地松 10年生人工林间伐显著地促进了林木胸径、单株材积的生长 ,有利于培育大径材 ,间伐后单位面积上蓄积量和单位面积材积总生长量 (包括间伐材 )均显著高于未间伐的林分。间伐措施对湿地松人工林木材管胞壁腔比、腔径比、S2 层微纤丝角 ,对径向和弦向干缩、体积和纵向干缩率、差异干缩、主要化学成分没有显著的影响 ,对木材管胞长度、长宽比值有显著负面影响。结合间伐后湿地松林分单位面积蓄积量及材积总生长量 ,培育纸浆材宜选用 33.3%～ 5 0 .0 %的间伐强度。 5 0 .0 %间伐强度的林分适宜培育建筑结构用材 ,其大径阶的木材比例高 ,单位面积上生长量、蓄积量也较大 ,木材晚材率、基本密度、顺纹抗压强度最大 ,抗弯性能最好。

人工林峦大杉木材的物理力学性质

对福建省引种的24年生峦大杉的木材物理力学性质进行检测,结果表明:峦大杉木材的气干密度为0.344 g/cm3、弦向全干干缩率6.020%、弦向湿胀性6.440%、吸水性237.810%、顺纹抗压强度6.004 MPa、抗弯弹性模量7 250.810 MPa、抗弯强度59.840 MPa、顺纹抗拉强度62.800 MPa;峦大杉的材质与杉木相近,应用方面可参考杉木,在木构件加工时,其安全系数可使用杉木的量值。