【作者】 陈复明；

【导师】 江泽慧；

【作者基本信息】 中国林业科学研究院 ， 木基复合材料科学与工程， 2014， 博士

【摘要】 本研究源自于林业公益性行业科研专项重大项目“大跨度竹质工程构件制造关键技术研究与示范”（201204701）。研究目标为：利用我国丰富而低廉的小径级丛生竹材资源，通过突破强度、刚度、耐久性以及设计和连接等关键技术难题，开发大跨度竹质层积材双拼梁构件，应用于房屋的建造。研究内容为：采用竹束单板整张化、板坯预压密实化和间歇压机连续热压工艺，通过解决预固化和接长问题，制造具有连续长度的竹束单板层积工程材料，开展大尺寸竹质工程构件的设计、制造和性能评价。借助于有限元分析软件，模拟不同层积结构板材的物理力学性能，降低密度、优化结构设计，为制造轻质高强的竹质工程材料提供技术基础和理论依据。本论文的主要研究工作与成果总结如下：（1）完成了竹束纤维疏解、单板整张化工艺，利用Box-Behnken Design设计法，建立了竹束单板接长工艺的响应面力学模型，该模型具有较好的精度，并利用遗传算法对响应面模型进行多目标优化，得到17个竹束单板接长工艺的Pareto解。（2）建立了竹束吸胶量与浸渍时间、浸渍比参数的数学模型，得到了较优的预压密实化工艺为：预压温度：5060℃，浸渍比：1:61:10，预压时间：15min30min。利用Fick’secod law和Sheldon吸水厚度模型对不同浸渍比板材的厚度膨胀系数Ksr、扩散系数D、厚度膨胀活化能E和表观活化能Ea进行了定量表征；建立了剩余弹性模量与水煮老化温度、吸水增重率的关系模型；当湿热老化温度越高、吸水增重越大时，弹性模量越小。板材弹性模量随时间的衰减规律与负指数函数趋势一致，静曲强度衰减率与吸水增重率呈线性关系；且吸水增重率的变化对静曲强度衰减程度的影响比弹性模量要大。（3）利用间歇式热压工艺制造出了连续长度竹束单板层积材，并采用Malthus模型对间歇式接头处的传热规律进行了定量表征，适当降低热压温度并适时通入冷却水能降低间歇式接头处的预固化程度。间歇式接头处的弹性模量和静曲强度在16GPa、150MPa以上，能达到结构单板层积材160E优等品的标准，具有良好的力学性能；水煮老化后，间歇式接头处的模量降级和强度衰减程度较相邻处要大；经28h煮-干-煮实验后，间歇式热压接头处的力学性能仍能达到结构单板层积材100E优等品的标准。（4）设计了八种竹束单板/杨木单板层积结构，并采用SNK法将不同层积结构的物理力学性能归类为不同的均值子集，同一子集内性能指标可相互替换；垂直加载时各层积结构板材的弹性模量、静曲强度略大于水平加载，而剪切强度值表现为水平加载略大于垂直加载；从比强度和比刚度的角度来看：层积结构(BBPBPBB)具有较优的综合性能，其中B表示竹束单板，P为杨木单板；当刚度较大的竹束单元位于层积结构的上、下表层时，板材具有有更好的强度和刚度；（5）利用有限元建立了八种层积预测模型，对其弹性范围和极限载荷下的不同层积结构板材的挠度、应力分布、层间应力梯度变化和冯米斯（VonMises）应力进行了模拟计算。层积预测模型具有较好的精度，计算值与实验结果及均值子集分类趋势一致；沿厚度方向上，（7B）和（7P）层积结构的应力分布呈线性，竹木复合层积结构为曲线变化。（6）利用连续成板工艺，制造出了竹质层积材双拼梁构件，并比较了五类双拼梁（竹束单板层积材、竹蔑层积材、竹木复合材和木质单板层积材）的抗弯性能。双拼梁的设计值是由截面刚度控制；木质双拼梁构件为跨中脆性破坏，竹质双拼梁构件为结构失稳，卸去载荷试样形状恢复，具有较好的延性。竹质双拼梁构件的截面抗弯刚度最高，竹木复合双拼梁其次，木质双拼梁最低。双拼梁横截面在高度上应变值呈线性变化，符合平面假设。更多还原

【Abstract】 This study originated from the National Forestry Public Welfare Scientific ResearchProgram (201204701), entitled “Key manufacturing technology research and demonstration ofLarge-Span bamboo engineering components”. The research object was as follows. Large-spanbamboo-based coupled beam was exploited for the application of housing construction, whichwas based on the resource advantages of small-diameter sympodial bamboo in China and somebreak-through in technological problem concerning strength, stiffness, durability, design andconnection. The research contents were as follows. The issues of precuring and lengtheningwere solved by the use of one-piece veneer formation, veneer preprocessing densification andintermittent hotpressing technology, and the engineering material was manufactured withcontinuous laminated bamboo-bundle veneer. In addition, the design, manufacture andperformance evaluation of large-span bamboo-based engineering components was conducted.The physical and mechanical properties of boards of different laminated structures weresimulated by finite element analysis software for the optimization of structural design andboard density decrease, which contributed to the manufacture of bamboo-based engineeringcomponents with high ratio of strength to weight.The main research work and corresponding results of this paper are summarized asfollows.(1) The process of bamboo-bundle brooming and one-piece veneer formation wasaccomplished. Through Box-Behnken Design method, the response surface model of BambooBundle Laminated Veneer Lumber was established towards different lengthening process,which showed good precision. In addition, the response surface model was undermulti-objective optimization by genetic algorithm, and17Pareto solutions were obtained.(2) The mathematic model of resin absorption was established between resin absorptionamount of bamboo-bundle, immersion time and PF/PVAC resin mass ratio, and the optimized veneer preprocessing densification process was obtained: preprocessing temperature50-60°C,PF/PVAC resin mass ratio1:6-1:10, preprocessing time15-30min. The parameters of boardswith different resin mass ratio were characterized quantificationally by Fick’s second law andSheldon’s thickness swelling model, including swelling rate parameter KSR, diffusioncoefficient D, swelling activation energy E and diffusion activation energies Ea. The3-Dmodel was established between boiling temperature, water absorption weight gain rate andresidual elastic modulus, which indicated that the higher boiling temperature and weight gainrate, the lower elasticity modulus was obtained. The attenuation law of elasticity modulus vs.time was consistent with the trend of negative exponential function, while the attenuation rateof modulus of rupture was related linearly with weight gain rate.(3) The continuous bamboo-bundle laminated veneer lumber was manufactured byinterval hotpressing technology, and the heat transmission law of intermittent joints wascharacterized quantificationally by Malthus model. The results indicated that appropriatelowering hot-pressing temperature and using cooling water contributed to the decrease ofprecuring degree of intermittent joints. The MOE and MOR of intermittent joints were above16GPa and150MPa, respectively, exhibiting sound mechanical properties. After boiling aging,the degradation and intensity attenuation degree of intermittent joints were larger than that ofthe adjacent ones, and much larger as the immersion temperature increased. There was distinctbrightness variation in CT images of intermittent joints, which indicated the presence offilamentous crack.(4) The bamboo-based laminated coupled beam components were manufactured and thebending properties were compared between bamboo-bundle laminated veneer lumber,bamboo-strips laminated lumber, bamboo-wooden composite and laminated veneer lumber.The design value of coupled beam component was controlled by rigidity of section. Woodencoupled beam components were under brittle failure in midspan when loading, whilebamboo-based coupled beam components under structure displacement. The latter restoredafter the removal of loads, which exhibited great ductility. Bamboo-based coupled beam components performed the highest bending strength, followed by bamboo-wooden coupledbeam components and wooden ones. The strain value of coupled beam components showedlinear variation in section height, which complied with hypothesis of plane mechanism.(5) Eight bamboo-bundle veneer/poplar veneer laminated structures were designed, andthe physical and mechanical properties were sorted into different subsets by SNK method thatperformance index was interchangeable in the same subset. The MOE and MOR were slightlylarger under vertical load than that under parallel load, and the opposite for shearing strength.The laminated structures showed better intensity and rigidity when the bamboo-bundles withconsiderable rigidity acted as surface layers. Results indicated that the laminated structureBBPBPBB had the best overall performance in this study.(6) The laminated prediction model was established by finite element method, and someparameters of boards of different laminated structures were under analog computation withinelastic range and ultimate load, which included deflection, stress distribution, interlaminarstress gradient change and VonMises stress. Laminated prediction model had good precisionthat the trend of calculated value, experimental data and mean subset classification wasconsistent with each other. The stress distribution was linear along thickness direction forlaminated structure of7B and7P, while curved for bamboo-wooden laminated structure.更多还原