【作者】 于子绚；

【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， 2012， 博士

【摘要】 竹材是一种优质的天然生物质梯度复合材料，具备高强度、高韧性、可持续发展等诸多性能与资源优势。但在材料应用方面，尚存在加工出材率低、性能变异较大等不足。因而提高竹材的加工利用效率及其产品稳定性，是提高竹基复合材料附加值的有效途径之一，也是促进竹基复合材料进一步发展和利用的必然趋势。生物质材料富含丰富的纤维素，易成为菌类、昆虫等多种生物体侵害的目标，与其它材料形式相比更容易遭受环境作用的影响，尤其在高温、高湿、强风暴等热带地区的极端环境下生物质材料的性能衰减将表现得更为严重，因而对竹基复合材料进行多方面的性能评价，研究其在热带湿热环境下的性能演变规律、损伤机理和天然抵抗能力，对于充分认识竹基复合材料对环境作用的响应机制、提升竹基复合材料的发展空间、指导并充分发挥其应用性能具有重要的意义。本文以梁山慈竹（Dendrocalamus farinosus）为研究对象，通过深入研究竹材的材性特征，确立了自主研发的竹材帚化机的加工原理和工艺路线，获得了横向交织、纵向连续的平整型竹束单板并以此为原料生产了竹束单板层积材。以高温、高湿、强风暴的热带环境为研究背景，针对生物质材料在热带地区应用时易发生尺寸稳定性变化、性能衰减、虫蛀侵害等不良现象，较为系统地研究了竹束单板层积材的耐湿热耦合性能、抗冲击性能、抗均布载荷性能以及抗白蚁性能及改性工艺，从设备研发、工艺评价、生物特性与环境作用的响应、机理分析与模拟等方面阐述了竹束单板层积材的制造工艺与环境适用性，揭示了竹束单板层积材的湿热老化特性、吸能机制和均布载荷作用下的形变特征。本论文的主要研究结果归纳如下：(1)确立了自主研发竹材帚化机的加工原理和帚化工艺，引入光学影像鉴别技术对单板帚化状态进行快速、定量的监测评价，优选出竹束单板并建立了其拉伸性能衰减的预测模型，通过对竹束单板进行规则化的层积复合，生产出质量稳定、密度均匀的竹束单板层积材；经6次帚化后压制的竹束单板层积材（1.0g·cm-3）其弯曲强度、拉伸强度和剪切强度分别达到245.8、203.0、和21.2MPa，室内、外吸水厚度膨胀率分别为4.8%和7.8%，相同密度下的基本性能优于传统重组竹。(2)湿热环境对竹束单板层积材的吸湿行为有明显影响，应用菲克定律和厚度膨胀模型在一定程度上能够较好地预测板材的吸湿特性，厚度膨胀模型的拟合优度大于0.88；湿热耦合作用降低了竹束单板层积材的力学性能，温度从21上升至60℃（RH99%），弯曲强度保持率降低至60%，压缩强度保持率降低至50%。(3)竹束单板层积材的抗冲击性能受单板质量、铺装方式、板坯层数、板材密度等多因素的影响。竹/木复合重组材和竹束单板层积材的总吸收能分别为105.1J和66.39J，二者的破坏模式分别为分层与沿纤维方向的劈裂。竹束单板层积材的吸能机制以面内吸能和面外吸能为主，竹/木复合重组材(纵横组坯)的面内强度较差，具有一定的分层吸能特性。(4)竹束单板层积材的弯曲挠度（mm）变化随着密度的增加而降低；将密度作为因数变量引入挠曲线方程，可在一定程度上预测竹束单板层积材的均布载荷中心点挠度随密度的变化规律。竹束单板材层积材的均布载荷性能存在支承方向、跨数及尺寸效应。竹材纤维方向与支承方向一致时容易引起板材背面的拉伸破坏，单跨支承时的挠度变化随板材规格的减小而降低。(5)研究了白蚁对竹束单板层积材的基本侵害规律和侵害机理，认为白蚁的侵害具有选择性，其侵害优先级为：纤维素＞其余成分，低硬度＞高硬度；竹材的薄壁组织首先遭受白蚁攻击，侵害路径沿维管束的边缘顺纤维方向延伸，毛竹精刨竹条的失重率为42.43%；竹束单板层积材的破坏形貌均沿着纤维方向，失重率为10.04%；改性竹束单板层积材具有良好的抗白蚁性能。更多还原

【Abstract】 As a kind of natural biomass gradient composite material, bamboo has advantages ofresurces and performance such as high strength,high toughness,sustainable development and soon. However, it has defects of a lower processing rate, large variability at the same time.Therefore, improving bamboo processing efficiency and the stability of the related products isone of the effective ways to increase the added value of the composite material and also theinevitable trend of the further development and utilization to promote bamboo/woodcomposites. Biomass materials are rich in cellulose, so they are violation targets of fungi,insects and many other kinds of biology. Compared with other materials, biomass materials arevulnerable to the destruction of the environment effect, especially in high temperature, highhumidity, strong storms, and extreme growing conditions. To understand the materialproperties of the environmental effect, the development space of the material, and to give fullplay to its use properties, various performance evaluation for bamboo and composite materialsshould be performed, and the performance evolution laws and natural resistance abilitiesunder the hot and humid environment should be understand too.Dendrocalamus farinosus is taken as the research object. Through debugging and testingof the bamboo brooming device researched by our laboratory independently, the transverseintertwined, and vertical continuous flat veneer were got, which is used as raw material toproduce the Laminated bamboo-bundle veneer lumber(LBVL). The south regionalenvironment with high temperature, high humidity, and strong storms is taken as the researchbackground. Performance and modification technology of termite resistance of Laminatedbamboo-bundle veneer lumber are studied, and the hydrothermal aging characteristics, theabsorbing mechanism and the action of deformation characteristics under uniform load arerevealed, through tests of termite resistance modification, hydrothermal aging, concussion ofdropping hammer, and performance test under uniformly distributed load. The main research results of this paper are summarized as follows:(1)A complete set of processing technology of bamboo brooming is designed, and theoptical image identification is introduced to monitor and evaluate the broom state. The targetbamboo-bunble veneers were optimized and the prediction model between brooming frenquecyand tensile strength decline ratio was got. Laminated bamboo-bundle veneer lumber of stablequality and even density is produced through regular lamination and composition ofbamboo-bundle veneers. and the MOR, MOE and tensile strength of the board with a broomingfrequency of six times is245.8,203.0and21.2MPa, while the thickness swelling rate ofindoor and outdoor is4.8%and7.8%, respectively.The basic performance is superior tobamboo scrimber.(2)The properties of LBVL were significantly influenced by hydrothermal condition.Thehydrothermal aging characteristics of laminated bamboo-bundle veneer lumber can bedescribed according to the Fick’s law and thickness expansion model, and the goodness-of-fitof the thickness expansion behavior is greater than0.9. mechanical properties are reduceded bythe hot and humid coupling effect. The retention ratio of the bending strength and thecompression strength are60%and50%at21to60℃(RH99%).(3)Properties of the impact resistance of laminated bamboo-bundle veneer lumber isaffected by the quality of bamboo-bundle veneer, way of the paving, number of layers, densityof the board, the influence of. The total absorption energy of the bamboo/wood compositematerial and laminated bamboo-bundle veneer lumber are105.1J and66.39J, respectively.and the failure modes are mainly layered damage and damage along the fiber direction,respectively. For laminated bamboo-bundle veneer lumber, the energy absorption mechanismare in-plane and out of plane. In-plane strength of bamboo/wood composite restructuringmaterial is poor, and it has a property of layer absorption.(4)Performance under uniformly distributed load of laminated bamboo-bundle veneerlumber is affected by the density, and the deflection(mm) change decreases with the increaseof density. In test conditions of this experiment, the deflection of change of laminated bamboo-bundle veneer lumber of different densities under uniform loading can be preliminaryestimated according to a formula deformation which is introduced the density parameter.Support direction and size effect exist in the performance under uniform load of laminatedbamboo-bundle veneer lumber. The tensile failure on the back of the board easily happen whenthe bamboo fiber direction and the support direction are consistent. The deflection of changedecreased with the board dimensions decreases when single span supporting is adopted.(5)The destroying laws of the termites to laminated bamboo-bundle veneer lumber aresummarized. Termites damage are selective and relevant to cellulose content and surfacehardness level. The more soft basic organization such as bamboo parenchyma cells firstlysuffers termites attack, and the attack path is along the edge of the vascular bundle along thefiber direction. The weight loss rate of moso bamboo is about42.43%. All the damagemorphologies of the samples are along the fiber direction. The weight loss rate of LBVL isabout10.04%. and the modification for laminated bamboo-bundle veneer lumber has goodeffect on termite resistance.更多还原