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.

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。

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。

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。

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。

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。

桢楠木材的物理力学性质

对94年生桢楠木材的物理力学性质进行了测定和分析,结果表明,木材基本密度在0.5 g.cm-3以上,60～80 a间达到最大值0.54 g.cm-3。40年生的桢楠木材基本密度、顺纹抗压强度、抗弯强度、冲击韧性、端面硬度属中等;随着树木年龄增加,顺纹抗压强度、冲击韧性、抗劈力、顺纹抗剪强度、端面硬度随着树木年龄增大而增加;在80年生时木材冲击韧性属高等,端面硬度很硬。如果兼顾其它指标,在桢楠栽培经营中,木材利用成熟期初步确定60～80 a。

23年生大叶栎木材物理力学性质的初步研究

对广西平果县海明林场23年生大叶栎木材的主要物理力学性质进行了测定和分析。结果表明:大叶栎木材的气干密度(含水率为12%)、基本密度和全干密度分别为0.583 g.cm-3、0.462 g.cm-3和0.507 g.cm-3,气干密度属于国产木材的中等级水平;径向、弦向和体积干缩系数分别为0.099%、0.183%、0.296%,湿胀率依次为4.106%、7.958%和12.627%,差异干缩为1.5-1.9,其尺寸稳定性较好;冲击韧性为52.12 kJ.m-2,端面、径面和弦面硬度分别为41.53 MPa、31.41 MPa和35.51 MPa,顺纹抗压强度为44.50 MPa,抗弯弹性模量和抗弯强度分别为12.63 GPa和127.31 MPa,径面和弦面顺纹抗剪强度分别为8.76 MPa和10.54MPa,抗劈强度依次为124.3 N.mm-1和138.6 N.mm-1。除冲击韧性和硬度较低外,大叶栎木材的主要力学强度均属于国产木材的中等级水平。

炭化木物理力学性能的研究

以速生杉木为原料制备炭化木,主要研究了炭化工艺条件对炭化木(又称热处理木)物理力学性能的影响。研究表明:当热处理温度由常温增加至220℃时,炭化木材色逐渐变深,含水率逐渐降低,由13.40%降至4.89%,吸水性能较大幅度降低,由未处理素材的1.616%降至0.879%,同时密度由未处理素材的0.368g/cm^3减小至0.326 g/cm^3,静曲强度下降约25%左右,弹性模量先增加后减小,减小量约4%左右,冲击韧性也先增加后减小,减小量约42%左右,受热处理条件影响程度较大,而且木材干缩和湿胀系数明显下降,较大程度提高了木材的尺寸稳定性。

高光谱成像技术及其在木材无损检测中的研究进展

开展木材无损检测是提高木材利用率,优化木材资源的重要手段。高光谱成像技术作为一种先进的无损检测技术,能同时获取待测物的光谱与图像信息,具有图谱合一的优点。介绍了高光谱成像技术的原理、装置以及数据处理方法,并首次详细介绍了该技术在木材及木制品的缺陷识别、重要物理力学性质检测以及化学性质预测等方面的研究进展。通过综合分析已有的研究,表明高光谱成像技术在木材及木制品品质无损检测中具有良好的应用前景。

处理温度对高温热改性橡胶木物理力学性能的影响

以过热蒸汽为介质常压高温热改性人工林橡胶树木材,处理温度为170、185、200和215℃,处理时间均为3 h。分析了处理温度对热改性橡胶木物理力学性能的影响,结果表明:提高热处理温度,橡胶木的平衡含水率显著降低,降幅为34.33%～62.97%;干缩率显著降低,降幅为3.1%～51.75%(弦向)和2.72%～48.57%(径向);湿胀率显著降低,降幅为37.80%～69.85%(弦向)和28.04%～68.57%(径向);吸水率轻微下降,但不显著;热改性后,橡胶木的尺寸稳定性明显提高。气干密度、全干密度仅在215℃处理时明显下降,其余处理温度变化不显著;弦面硬度先略微增加,后急剧降低,整体呈下降态势;弦、径向局部横纹抗压强度先升高后下降,整体呈增加态势;抗弯强度显著降低,降幅为9.26%～37.52%;抗弯弹性模量有增加,但不显著。