冷杉木材与不同覆板材料钉连接节点的动态荷载性能研究

钉连接是木结构中重要的连接节点,在轻型木结构建筑的剪力墙中起到重要的承载作用。不论国内还是国外,结构胶合板、定向刨花板、冷杉木材都是木结构建筑中主要的建筑材料。笔者研究了不同覆板类型与冷杉木材钉连接的动态荷载性能,对不同厚度胶合板、定向刨花板、钉直径与冷杉的连接性能进行了对比(静态荷载和动态荷载)研究。结果表明,钉直径、覆板种类和厚度对动态载荷性能、破坏位移影响显著,10D钉连接冷杉和不同覆板材料时,连接性能最佳;相同厚度的定向刨花板比结构胶合板与冷杉的连接性能好;厚度为16 mm的结构胶合板具有良好的连接性能。本研究为轻型木结构的建造提供理论和实际测试依据。     

机械应力式人造板质量在线无损检测技术的研发和应用

静弯曲弹性模量(MOE)是结构用板材(如大片刨花板、定向刨花板、结构胶合板、单板层积材等)最为重要的力学指标,而静弯曲强度(MOR)则是几乎所有人造板(如胶合板、刨花板、中密度纤维板等)的最为重要的力学指标.     

面板种类和芯板厚度对结构用木质保温板力学性能的影响

以定向刨花板(OSB)或结构胶合板为面板,聚氨酯保温板为芯板,制备结构用木质保温板(SIPs),探究面板种类和芯板厚度对SIPs力学性能的影响。结果表明:不同材料面板和不同厚度芯板制备的SIPs,力学荷载值均可满足ANSI/APA PRS 610.1-2013标准要求;结构胶合板为面板的SIPs极限荷载值高于OSB面板SIPs;随着芯板厚度的增加,SIPs的极限荷载值逐渐增加;聚氨酯保温板可以替代聚苯乙烯保温板(EPS)制备SIPs。     

结构用人造板冲击荷载性能研究北大核心

结构用人造板(SWP)在冲击荷载下的承载性能是评价其能否应用于建筑结构的关键指标之一。以进口定向刨花板、国产定向刨花板、国产结构胶合板等SWP产品为对象,测试并对比了3种SWP的冲击荷载性能表现。研究结果表明,不同厚度的SWP适用的搁栅间距范围不同,产品厚度越大,搁栅结构体系适用间距亦越大;实际应用中可通过增加产品的抗弯弹性模量和降低搁栅间距来获得优异的冲击荷载性能。     

结构用人造板冲击荷载性能研究

结构用人造板(SWP)在冲击荷载下的承载性能是评价其能否应用于建筑结构的关键指标之一。以进口定向刨花板、国产定向刨花板、国产结构胶合板等SWP产品为对象,测试并对比了3种SWP的冲击荷载性能表现。研究结果表明,不同厚度的SWP适用的搁栅间距范围不同,产品厚度越大,搁栅结构体系适用间距亦越大;实际应用中可通过增加产品的抗弯弹性模量和降低搁栅间距来获得优异的冲击荷载性能。     

广西人造板业现状和发展思路

人造板是木竹加工的主导产品,是高效利用林木资源的主要方式,是林业产业中高增值、高技术含量的主要产业.人造板及其深加工产品包括纤维板(木、竹中/高密度纤维板、硬质纤维板)、胶合板(胶合板、建筑模板、竹胶合板)、刨花板(普通刨花板、均质刨花板、轻质刨花板、定向刨花板及其他刨花模压制品)、其他板(细木工板、单板层积材、定向单板成材)、强化木地板、贴面装饰板、板式家具等.     

降低刨花板生产的脲醛胶用量

全苏胶合板科研所研制了刨花板和胶合板生产用木素磺酸盐改性脲醛树脂。如果说木素磺酸盐改性脲醛树脂(木素磺酸盐用量为树脂重量的30%)已经应用于胶合板生产,那么这种改性胶粘剂用于刨花板生产还仅仅是开始。木素磺酸盐系价格低廉、数量较多的制浆造纸剩余物。苏联根据全苏规格OCT 81—79—74生产两种牌号商品:一是КБЖ,     

聚磷酸铵分层阻燃处理对杨木大片刨花板性能的影响

针对传统均混阻燃剂工艺对刨花板性能的不利影响以及刨花板燃烧由表及里发展的特点,采用“表-芯-表”分层施加阻燃剂的方法制备阻燃大片刨花板。将总质量分数为12.5%的聚磷酸铵(APP)阻燃剂引入大片刨花板中,调控大片刨花板每层阻燃剂添加量,探究分层阻燃工艺对大片刨花板内结合强度、静曲强度、弹性模量及吸水厚度膨胀率等物理性能的影响。采用锥形量热仪表征产品的燃烧特性,并对大片刨花板燃烧后残炭的组成进行了分析。结果表明：分层施加阻燃剂有效调控了大片刨花板的力学性能和吸水厚度膨胀率,弹性模量均比未添加阻燃剂板材高226 MPa以上;分层工艺中APP424内结合强度和静曲强度提升最高,与均混工艺相比,分别提升0.15和8.59 MPa;无机阻燃剂APP在表层的施加量会影响大片刨花板的静曲强度,在芯层的施加量会影响大片刨花板的内结合强度;分层施加阻燃剂对大片刨花板的阻燃性能提升明显,第2放热峰延缓了255～435 s,且火灾危险性明显下降,其中APP343(上、下表层各施加质量分数为3.75%的APP,芯层施加5%的APP)防火安全性最佳;分层施加阻燃剂有效提高了阻燃大片刨花板的气相阻燃效果,且并未明...     

基于CT技术的人造板剖面密度检测

利用CT技术无损检测槐树大片刨花板、柳杉重组木以及麦秸中密度纤维板的内部结构与密度特征。结果表明:大片刨花板与重组木的密度变异均高于麦秸板;大片刨花板剖面密度分布无明显变化规律,而重组木呈W型分布、麦秸板呈V型分布。CT技术将为深入研究木基复合材料的结构与性能产生积极影响。     

“新三板”将取代“老三板”

当前在欧美各国,人造板工业又有了新的发展。“老三板”(即胶合板、纤维板、刨花板)已逐渐被”新三板”(即组合胶合板、纤维板、刨花板)所代替。组合胶合板可以把木材利用率从生产胶合板的40％提高到75％;每生产10,000立方米的用胶量可从1,200吨降为1,000吨,降低成本15％。组合胶合板不仅保持了胶合板的原有特     

基于竹材生物学特性和材性适应性的竹大片/定向刨花板生产技术的研发

根据对云南主要材用丛生竹组织结构、主要物理力学性质和化学组份的研究和对其它材用竹材性的了解、对竹大片/定向刨花板工业生产技术一系列的实验室单因素、多因素等重复、优化试验和工业性试验直至成套生产设备的研制和生产线的建设、生产和产品应用的结果,运用人造板基本工艺原理,揭示了竹大片/定向刨花板的组成结构、生产工艺和设备技术条件对竹材特殊的生物学特性、竹材材性的适应性。以此为基础所形成的竹大片/定向刨花板工业生产成套技术因此得以达到工业生产水平。     

竹大片刨花板对竹材生物学特性的适应性

以云南四种典型材用丛生竹（龙竹、甜龙竹、黄竹和油勒竹）宏观构造、组织结构、主要物理力学性质和化学组份等竹材主要生物学特性的研究分析结果为依据,提出了竹大片刨花板的结构、制板工艺和设备与原料竹材生物学特性之间应有的适应性关系。继而,通过实验室系列化试验和工厂试生产,确定了竹大片刨花板的应有性能和最佳工艺条件包括竹大片刨花的最佳质量指标及其最佳制备条件。     

粉状酚醛树脂胶粘剂的制备与性能

探讨了粉状酚醛树脂胶粘剂的制备和性能,研究结果表明,通过适当参数下的喷雾干燥可制得性能较佳的粉状酚醛树脂胶,直接利用粉状酚醛树脂胶所制备的竹大片刨花板性能优于同等条件下液态酚醛树脂胶竹大片刨花板,且达到加拿大标准"CAN3-O437.0-M85 Waferboard and Strandboard"的要求。     

利用国产液体酚醛胶生产华夫板

本文介绍了以杨木和桦木为原材料,利用国产液体酚醛树脂胶生产华夫板的工艺技术条件,华夫板的物理力学性能,使用范围,生产成本及其广阔的前景。     

酚醛树脂竹大片刨花板工艺成本与性能质量的关系

为了给竹大片刨花板的工业化生产提供可靠的技术、经济依据,本研究探求了压缩比、胶种、用胶量和竹种等工艺 成本因素对工程结构用酚醛树脂竹大片刨花板性能质量的影响。试验结果表明,通过调节压缩比即可调节板材的性能 和生产成本,压缩比为1.0、用胶量为4％的不含防水剂的酚醛树脂竹大片刨花板的各项性能可超过同类木质板材的性 能．单独或混合以具必要竹壁厚度的材用或笋材两用竹为原料均可获得性能良好的竹大片刨花板。     

Creep in chipboard

Summary Samples of five chipboards, one waferboard, one plywood, one fibre building board and redwood timber (Pinus sylvestris) were loaded in 4-point bending under four stress levels: 30, 45, 67.5 and 75% of the short term ultimate, thereby extending earlier work at 60% stress level. Five environmental conditions were used at each stress level: 10°C 62% relative humidity (rh); 20°C 30% rh; 20 °C 65% rh; 20°C 90% rh and 30°C 68% rh. Deflections were recorded at least on a daily basis for a period of 6 months, unless failure of the sample occurred earlier. Values for the elastic, viscoelastic and viscous components of creep deflection were calculated for two time periods using the 4-element rheological model developed in an earlier paper: comparisons were made on the basis of the percentage contribution of each component. The relative proportions of the elastic, viscoelastic and viscous components making up total deflection were found to vary considerably with time, temperature, relative humidity, stress level and material. The relationships were complex with strong interactions occurring among environmental condition, stress level and material. Thus, for example, the effect of high temperature, or high relative humidity, in determining the magnitude of the viscous component was much greater at higher levels of stressing: waferboard appeared to be less sensitive to high humidity and solid timber more sensitive to high temperature than the other materials. T-tests further confirmed the complexity of the relationships. It is concluded that much of the variability in creep deflection recorded in Part 8 of this series is primarily due to changes in the percentage contribution of the viscous component.     

A comparison of three approaches to modeling leaf gas exchange in annually drought-stressed ponderosa pine forests

We tested, compared and modified three models of stomatal conductance at the leaf level in a forest ecosystem where drought stress is a major factor controlling forest productivity. The models were tested against 2 years (1999 and 2000) of leaf-level measurements on ponderosa pine (Pinus ponderosa Dougl. ex Laws.) growing in the Mediterranean climate of California, USA. The Ball, Woodrow and Berry (1987) (BWB) model was modified to account for soil water stress. Among the models, results of the modified BWB model were in the closest agreement with observations (r2 = 0.71). The Jarvis (1976) model showed systematic simulation errors related to vapor pressure deficit (r2 = 0.65). Results of the Williams, Rastetter, Fernandes et al. (1996) (SPA) model showed the poorest correlation with empirical data, but this model has only one calibration parameter (r2 = 0.60). Sensitivity analyses showed that, in all three models, predictions of stomatal conductance were most responsive to photosynthetically active radiation and soil water content. Stomatal conductance showed little sensitivity to vapor pressure deficit in the Jarvis model, whereas in both the BWB and SPA models, vapor pressure deficit (or relative humidity) was the third most important variable. Parameterization of the SPA model was in accordance with the parameterization of the modified BWB model, although the two models differ greatly. Measured and modeled results indicate that stomatal behavior is not water conservative during spring; however, during summer, when soil water content is low and vapor pressure deficit is high, stomatal conductance decreases and, according to the models, intrinsic water- use efficiency increases.     

竹木复合板与竹木复合层积材的抗弯性能

采用成熟的竹木复合集装箱底板制造工艺,根据不同的组坯方式,用竹帘及杨木单板压制成竹木复合板和竹木复合层积材。该工艺的创新点在于只将杨木单板浸胶,而竹帘直接干燥铺装,以减少人工操作对竹帘的破坏。通过研究两种板的抗弯性能,发现其顺向抗弯性能非常好,可将其分别作为集装箱底板和建筑结构用材。此外,针对竹木复合板性能不稳定的问题提出了改进方案。     

Analysis of Markov model on predicting wood composite weathering

Summary This paper evaluated the wood composite weathering over time step by Markov theory. By the null hypothesis (H₀), the panel weathering under the long-term outdoor exposure was determined to be a Markov process. The transition matrix which derived from the practical data can be calculated by program Markov and thus the future outcome of wood composite weathering can be forecasted. Also, the utility of the Markov model was successfully testified from the example of 3-year natural aging waferboard in Ottawa, Saskatoon, Fredericton areas.