人工林杉木层板分级及性能研究

对人工林杉木层板按照GB/T 50708—2012进行目测分级和机械弹性模量分级,探讨两种分级方法的适用性和科学合理性。通过测定各层板的年轮宽度、绝干密度、弹性模量和静曲强度并进行处理与分析发现:对于目测分级,各等级层板的弹性模量值其离散度非常大且没有规律性,其特征值(平均值和5%分位值)也达不到标准规定的要求,静曲强度值的离散度也很大但其特征值随层板等级的提高而增大,等外层板的弹性模量和静曲强度值反而比等内层板的要大;层板密度与其静曲强度基本上没有相关性,而层板的年轮宽度与其静曲强度有一定的负相关性;层板的弹性模量与其静曲强度有较好的正相关性,采用机械弹性模量分级,静曲强度的特征值随层板等级的提高而成比例地提高。研究表明,目前的目测分级方法不适合于人工林杉木层板的分级,目测分级层板因弹性模量达不到要求不能用于胶合木制造,而采用机械弹性模量分级法则可以制造出强度性能可靠的胶合木。     

侧压型竹层板用竹条分级研究

按照GB/T 17657—2022《人造板及饰面人造板理化性能试验方法》中的三点弯曲法,先测试竹条径向两面(近竹青面和近竹黄面)各节间和节部的抗弯弹性模量,然后将试件从宽度方向一分为二,测试其各对应位置的弦向抗弯弹性模量和静曲强度。探讨竹条节间中心位置不同方向的弹性模量相互之间及其与弦向静曲强度之间的关系,并建立相应的数学模型;分析竹节对竹条弹性模量的影响,确定侧压型竹层板用竹条的实用分级方法;按中间点径向抗弯弹性模量对竹条进行分级,并测试其弦向静曲强度,分析竹条分级的可靠性;将不同等级的竹条分别制备侧压型竹层板试件,测试其静曲强度和抗弯弹性模量,验证竹条分级的有效性。结果表明：通过测量竹条节间径向两面抗弯弹性模量并计算其平均值,可以较准确地推测其弦向抗弯弹性模量值;通过测试竹条某节间径向两面抗弯弹性模量的平均值,可以很好地预测该部位的弦向静曲强度;仅测量竹条中间点(无论是节间还是节部)的径向抗弯弹性模量就能较好地推测出整根竹条的弦向抗弯弹性模量;采用竹条中间点径向抗弯弹性模量分等可以对竹条(弦向静曲强度)进行有效分级;按竹条中间部位的径向抗弯弹性模量对竹条进行分级,其侧压型竹层板的分...     

不同老化试验方法对层板胶合木性能的影响

以层板胶合木为研究对象,比较了不同人工加速老化方法(ASTM D1037、BS EN1087—1、CAN/CSA—0188、ASTM D3434)对层板胶合木构件力学性能的影响。层板胶合木构件在4种不同人工加速老化方法的作用下,通过对静曲强度、弹性模量、剪切强度及木破率等实验指标的比较分析,发现试材的胶合剪切强度下降程度明显高于其他性能的变化程度,建议作为判定层板胶合木构件耐老化性能的重要指标;经分析认为达到相同老化效果BS EN1087—1法更节约时间,是研究层板胶合木耐老化性能较优的人工加速老化处理方法。     

胶合木构件胶接性能及耐久性研究

以层板胶合木为研究对象,采用ASTM D1037、BS EN1087-1,CAN/CSA-0188,ASTM D3434四种人工加速老化方法对单组份聚氨酯胶黏剂胶合而成的层板胶合木构件进行处理。老化处理后,试材的胶合剪切强度下降幅度在27.8%~44.9%之间,下降程度明显高于吸水厚度膨胀率、静曲强度和弹性模量,据此建议将胶合剪切强度作为判定层板胶合木构件耐老化性能的指标。BS EN1087-1老化处理后试材的性能变化情况SASTM D1037较为相似,且用时短,认为是研究层板胶合木构件耐久性较优的人工加速老化处理方法。     

落叶松结构用胶合木层板指接工艺参数对力学性能的影响

以兴安落叶松刨光锯材制作胶合木指接层板,探讨指榫参数、指接压力和不同规格尺寸对锯材指接层板抗弯性能的影响。结果表明:指榫工艺参数对指接层板抗弯弹性模量影响较小,而对抗弯强度影响较大。当选用12.7、19mm和25mm指榫长度及其相应的指接工艺参数时,层板抗弯强度平均值和5%分位值均能达到国家标准GB/T 26899-2011《结构用集成材》目测分等Ⅰ_d等级和机械分等M_E14等级规定值,对于中小截面胶合木层板,尽可能考虑选用12.7~19mm范围内较小的指榫长度进行指接加工以利节材。在指接过程中应选用合适的指接压力,指接压力过大或过小都会对指接层板抗弯性能尤其强度造成不利影响,指接层板抗弯强度的尺寸效应与非指接锯材相似。     

浅议配料比对木纤维／聚丙烯复合材料性能的影响

本文研究了配料比对木纤维／聚丙烯复合材料物理力学性能的影响,研究结果表明：随着聚丙烯用量的增加,木纤维／聚丙烯复合材料的弹性模量、静曲强度呈先上升后下降趋势。当聚丙烯用量为25％左右时,弹性模量和静曲强度均达到较大值;随着聚丙烯用量的增加,吸水厚度膨胀率呈下降趋势,而密度略呈上升趋势。     

短周期工业材层板等级区分与胶合木强度性能之关系

短周期工业材层板等级区分与胶合木强度性能之关系宋润惠郝金城高云龙（黑龙江省林产工业研究所１试验目的结构胶合木是通过合理配置不同等级的层板径胶合而成的木质材料，与天然木材相比，它具有较大的规格尺寸和较高的力学强度，尺寸稳定性好，耐久性强。根据建筑设计要...     

玻璃纤维增强结构用单板层积材热压工艺研究

通过玻璃纤维增强速生杨木制备杨木单板层积材(LVL),可提高杨木的强度等级,使其达到结构集成材层板的使用要求。采用正交实验方法,研究温度、时间、压力、偶联剂浓度、涂胶量对杨木单板层积材弹性模量、静曲强度、剪切强度的影响,其中主要研究热压工艺对力学强度的影响,得出的最优工艺参数为:热压温度130℃、时间100s/mm、压力1.2MPa。     

胶合木层板配置与其强度性能

胶合木层板配置与其强度性能郝金城（黑龙江省林产工业研究所）王世鑫李金杰（哈尔滨国营松江胶合板厂）１试验目的胶合木与天然木材的区别在于胶合木是由层板胶合而成的材料，它可以人为地配置不同层板，然后胶合成胶合木。层板配置不同，其胶合木的强度性能有较大的差异...     

灰木比对水泥刨花板力学性能的影响

对不同灰木配比的水泥刨花板力学性能进行试验研究,结果表明:在研究范围内水泥刨花板的密度、内结合强度、弹性模量和静曲强度都随灰木比的升高而增强,吸水厚度膨胀率随着灰木比的升高而降低。当灰木比为1:1时,板材的静曲强度为8.4 MPa;当灰木比为1.5:1时,板材的静曲强度为14.6 MPa;当灰木比为2:1时,板材的静曲强度为15.6 MPa水泥刨花板的力学强度在灰木比为2:1时达到最高。     

木材弹性模量自动检测的研究进展

论述了国内外木材弹性模量动态检测技术的研究现状与发展趋势．为今后国内发展木材力学性能的无损检测研究，自主研制实时木材强度分级生产线提供参考依据。     

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。     

利用振动法检测胶合板的抗弯弹性模量

通过弯曲振动试验、纵波传播试验及纵波共振试验对胶合板的抗弯弹性模量进行无损检测，并分析了三种试验方法测定结果之间的关系。结果表明：虽然不同方法测得的胶合板弹性模量值不同，但其间存在一定的内在联系。     

五种白桦木材的抗弯强度和抗弯弹性模量的研究

本研究主要对五种新培养的速生白桦木材的物理力学性质进行了测试，并根据测试结 果进行了变异分析及方差分析，分析结果表明，白桦木材的力学性质较好，物理力学性质差 异不显著，适宜作家具材。此结果表明，可根据木材物理力学性质因子选取优良树种。     

Changes in the mechanical properties of wood during a period of moisture conditioning

Changes in the modulus of elasticity (MOE), modulus of rupture (MOR), and stress relaxation in the radial direction of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by the adsorption process from a dry state and by the desorption process from a moisture content slightly below the fiber saturation point were investigated. The MOE and MOR of wood conditioned by the adsorption process showed significant increases during the later stages of conditioning when the moisture content scarcely changed. However, with the desorption process they did not increase as much during later stages of conditioning, though they increased during early stages of conditioning when the moisture content greatly decreased. The stress relaxation of wood decreased with an increase in the conditioning period with both the adsorption and desorption processes. These results suggest that wood in an unstable state, caused by the existing state of moisture differed from that in a true equilibrium state shows lower elasticity and strength and higher fluidity than wood in a true equilibrium state. Furthermore, the present study demonstrates that the unstable states of wood induced during the course of drying, desorption, and possibly adsorption of moisture are slowly modified as wood approaches a true equilibrium state.     

Characterization of major,unused, and unvalued Indonesian wood species I. Dependencies of mechanical properties in transverse direction on the changes of moisture content and/or temperature

Mechanical property changes due to the moisture content (MC) and/or temperature changes were examined for 15 Indonesian wood species. A static bending test was carried out at 20°C, 65% relative humidity (air-dry), and water-saturated at 20°C (wet-20) and 80°C (wet-80). For individual test conditions, modulus of elasticity (MOE) and modulus of rupture (MOR) increased linearly with specific gravity regardless of wood species; however, maximum deflection did not correlate with specific gravity for any MC or temperature conditions. The relative values of MOE and MOR measured in wet-20 to air-dry conditions were variously affected from slightly to strongly depending on the wood species. However, the relative values always decreased markedly when saturated in water at 80°C, regardless of wood species. The relative MOE, MOR, and maximum deflection values due to the change in MC or MC and temperature combined were independent of specific gravity but may be dependent on wood type: softwood or hardwood.     

Static bending strength performances of cross-laminated woods made with five species

Thirty types of three-ply parallel- and cross-laminated woods were prepared from five species, and their static bending strength performance were investigated. The modulus of elasticity (MOE), proportional limit stress, and modulus of rupture (MOR) perpendicular to the grain were increased by cross-laminating, and the extent of the increase increased with decreasing density of the species. The measured values of MOE parallel and perpendi-cular to the grain of parallel-laminated woods and perpendicular to the grain of face laminae of cross-laminated woods were approximately equal to those calculated from true MOEs of individual laminae. However, the MOE parallel to the grain of face laminae of cross-laminated woods was much lower than the calculated MOE owing to the effect of the deflection caused by shear force on the MOE. The percentage of deflection caused by shear force versus total deflection (Y _s) showed high values, from 16.1% (buna) to 40.5% (sugi), and it decreased linearly with increasing shear modulus in the cross section of the core. In addition, there was an extremely high positive correlation between the MOR and the measured MOE parallel to the grain of face laminae of cross-laminated woods. The MOR was also highly dependent on the shear modulus in cross section of the core.Part of this paper was presented at the 50th Annual Meeting of the Japan Wood Research Society, Kyoto, April 2000     

Physical and mechanical properties of wood after moisture conditioning

Some properties of wood (hinoki:Chamaecyparis obtusa) moisture-conditioned by an adsorption process from a dry state and by two desorption processes (from a water-saturated state and from a state with a moisture content slightly below the fiber saturation point) were investigated. The moisture contents of wood conditioned by the adsorption process and by the desorption process continued to approach to one another for the moisture-conditioning period of over 50 weeks. Accordingly, sorption hysteresis should be regarded as a transitional phenomenon that occurs during the process of approaching the true equilibrium, which requires a long time. The wood conditioned by the desorption process beginning from a water-saturated state showed slightly smaller dimensions than those conditioned by the adsorption process with the same moisture content; however, the wood conditioned by the desorption process from a moisture content below the fiber saturation point showed slightly larger dimensions than those conditioned by the adsorption process. The wood conditioned by the adsorption process from a dry state showed a higher modulus of elasticity and modulus of rupture than did the wood conditioned from a water-saturated state with the same moisture content. The mechanical properties of the wood also varied based on the states at which the desorption process was started. This is a notable characteristic of the relation between the drying condition and the mechanical properties of wood.     

竹片覆面胶合板的初步研究

本文研究了以竹片为外层材料、多层杨木单板为芯层材料的复合胶合板的结构和力学性能，分析了板坯结构形式、纵向纵片厚度、单板层数及板坯压缩率与产品机械强度之间的关系。初步研究结果表明，板坯结构形式对产品的静载荷抗弯曲性能影响显著；在试验范围内，纵向竹片厚度为３．５－５．０ｍｍ、板坯压缩率在２３％左右时，竹片覆盖面杨木胶合板的综合力学性能比较理想。     

Effective sampling method for estimating bending strength distribution of Japanese larch square-sawn timber

Information on the strength distribution of timbers and other wood products seems to have become more important for users and producers after revision of the Japan architectural standard in 1998, which emphasizes the performance requirements of structures. Because there is no way other than expensive destructive tests to collect strength data, many researchers have proposed many inspecting methods for predicting strength by nondestructive evaluation. The most popular method for structural timber is the mechanical grading method based on the relation between Young's modulus (E) and strength () with some linear regression models. On the other hand, it is well known that the proof loading test is superior for obtaining information on the lower tail of distribution. If the E distribution of the objective timbers is known approximately, selecting timbers nearest to the projected E values saves timbers for destructive tests. We examined the alternative sampling method using the reported e- data sets of Japanese larch square-sawn timber. The simulated results showed that the estimated lower tail of the bending strength distribution by the alternative method was a better approximation of the experimental distribution than that derived from the conventional linear regression model.Part of this paper was presented at the 47th Annual Meeting of the Japan Wood Research Society, Kochi, April 1997