【作者】 尚莉莉；

【导师】 江泽慧；

【作者基本信息】 中国林业科学研究院 ， 木材科学与技术， 2014， 博士

【摘要】 棕榈藤材是仅次于木材和竹材的重要非木材林产品，具有较高的经济价值。我国藤产业95%以上的原材料依赖进口。近年来，由于主要产藤国家采取严格的限制原藤出口政策，商业用藤原材料严重短缺。同时，藤产品在使用过程中常常因为气候、外力等原因产生脆裂，使得产品的使用寿命缩短。如何解决藤材在使用中的脆裂问题，使其保持良好的韧性，扩大藤产品使用范围，已成为藤加工企业亟待解决的实际问题。本论文以国产钩叶藤材为研究对象，全面分析了其解剖构造、物理力学性质和化学成分；运用线弹性断裂力学的理论对其断裂韧性的测试方法进行了探索性研究；以甲基丙烯酸甲酯（MMA）和甲基丙烯酸缩水甘油酯（GMA）为改性剂，采用加压浸渍的方法对钩叶藤材进行增强改性研究，同时以体视显微镜和扫描电镜为手段，观察改性前后试样的破坏断面，探讨钩叶藤材的断裂破坏机理；通过对改性后钩叶藤材力学性能进行综合评价，探讨其作为藤家具类框架和结构用材的可行性，以期为藤材力学研究提供基础数据，为劣质藤材优化提供切实可行的方案。论文的主要研究结论如下：（1）钩叶藤材是一种梯度材料，藤芯、藤皮的性质差异大。维管束在藤皮处排列紧密，在藤芯处排列稀疏，只含有一个韧皮部和一个后生木质部导管。维管束大小在径向由外向内增大，分布密度随藤茎高度的增加而增大。基本密度为0.27g/cm3；微纤丝角平均为31.05°，相对结晶度为23.47%。抗弯强度和模量分别为31.05MPa和1.04GPa，压缩强度和模量分别为17.87MPa和831MPa。综纤维素含量为66.51%~72.96%；木质素含量为16.73%~22.03%。（2）从藤芯处预制的裂纹能用应力强度因子K准则判断，试验测得其名义断裂韧性值为0.476MPa·m1/2；从藤皮处预制的裂纹需用能量释放率G准则进行判断，试验测得其名义断裂韧性值为0.263MPa·m1/2。（3）含水率对从藤芯处预制裂纹试样的断裂韧性有显著影响，气干状态下的断裂韧性显著高于绝干和饱水状态的断裂韧性，气干状态下的断裂韧性为0.476MPa·m1/2，饱水状态下的断裂韧性为0.189MPa·m1/2，绝干状态下的断裂韧性为0.154MPa·m1/2。（4）MMA和GMA对钩叶藤材的改性效果明显。通过力学性能的综合评价获得的最佳改性工艺为浸渍液浓度100%MMA，浸渍压力常压，固化温度60℃，浸渍时间4h。改性后抗弯模量增加了127%，抗弯强度增加了200%；压缩模量增加了146%，压缩强度增加了119%；断裂韧性增加了231%。（5）钩叶藤素材三点弯曲断裂过程中裂纹沿预制裂纹面扩展，在薄壁组织中较平整的横向扩展，遇纤维鞘阻隔后发生偏转，总体呈阶梯型断裂；改性剂的添加改变了钩叶藤材的破坏路径，改性材中裂纹沿着预制裂纹方向扩展，总体呈一字型断裂。断裂韧性与维管束分布密度呈线性正相关。更多还原

【Abstract】 Rattan is regarded as the important non-wood forestry products and has higher economicvalue. Nearly95%of rattan resources are imported from abroad. In recent years, due to theoriginal rattan export ban restrictions, shortage of raw materials has become the key issuesconstraining the development of Chinanese rattan industry. Meanwhile, the life of rattanproducts is shortened largely by brittle ruptures always caused by climate change and externalforces. How to prevent the rattan products from brittle ruptures, how to keep its highertoughness and how to enlarge its application extent has become an urgent problem to besolved.In the present work, the fundamental properties of Plectocomia kerrana Becc, a largediameter non-commercial rattan species, was thoroughly investigated, including (1)Investigating the anatomical structure, physical properties and chemical compositions;(2)Exploring the testing methods of fracture toughness based on linear elastic fracture mechanics;(3) Using methyl methacrylate (MMA) and glycidyl methacrylate (GMA) as modifier to treatthe original rattan by pressure impregnation method;(4) Comparing the fracture plane beforeand after modification by stereomicroscope and scanning electron microscope as well asexploring the possible fracture mechanisms;(5) Comprehensively evaluating the mechanicalproperties of modified products and discussing its applicability as raw materials for frameworkof rattan furniture;(6) Providing basic database for the research area of rattan mechanicalperformance and feasible plan for optimizing inferior rattan.The main conclusions are as follows:(1) Plectocomia kerrana Becc is a gradient material with large differences in the nature ofcore and cortex. Vascular bundles (Vbs) arrange tightly in cortex and sparsely in core, whichonly contain a phloem and a protoxylem vessel. The dimension of Vbs decrease from cortex tocore direction, while its distribution density increases along with the rattan altitude. The basic density of rattan is0.2746g/cm3. The microfibril angle is31.05°and the relative crystallinity is23.47%. The bending strength and bending modulus is31.05Mpa and1.04Gpa, while thecompressive strength and the compressive modulus is17.87Mpa and831Mpa, respectively.The holocellulose content ranges from66.51%~72.96%, while the lignin content ranges from16.73%~22.03%.(2) The crack prefabricated from core is determined by the stress intensity factor K, whilethe crack prefabricated from cortex is determined by energy release rate G. The value ofnominal fracture toughness is0.476MPa·m1/2and0.263MPa·m1/2, respectively.(3) The modification effect proves to be obvious when treated with MMA and GMA. Theoptimized modification process is A1B1C2D2, that is, impregnation concentration100%MMA,atmospheric pressure, curing temperature60℃, impregnation time4h. For the modifiedproducts, the bending modulus, the bending strength, the compressive modulus, compressivestrength and fracture toughness increases by127%,200%,146%,119%and231%,respectively.(4) When the rattan is bended, the crack in the rattan extends along with the crack planeprefabricated. Within the parenchymatic tissue, the crack extends transversely and changes itsdirection when the crack stretches into fiber sheath. The crack edge shows a ladder type. Afterimpregnating with modifier, the fracture route of rattan changes. The crack stretches along withthe direction of crack prefabricated. The crack edge displays a linear type. Moreover, thereexists a positive linear correlation between fracture toughness and Vbs distribution density.更多还原