【作者】 吕丽；

【导师】 肖加余； 白书欣；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2006， 博士

【摘要】 橡胶是一种重要的粘弹类阻尼材料,已广泛应用于航空、航天、交通、机械、建筑等领域。但是,橡胶力学性能较差,很难单独作为结构材料直接使用。为了在不损失橡胶阻尼性能的同时提高其力学性能,实现结构-功能一体化,根据复合材料力学理论和阻尼机理,设计了一种由玻璃纤维(GF)、铅(Pb)和橡胶(R)组成的新型阻尼复合材料——玻璃纤维芯铅网(丝)增强橡胶复合材料(GF/Pb/R)。本课题对四种增强方式的复合材料依次进行了系统研究,它们是:GF/Pb网横向增强橡胶复合材料(H-GF/Pb/R)、GF/Pb网纵向增强橡胶复合材料(V-GF/Pb/R)、短GF/Pb丝增强橡胶复合材料(S-GF/Pb/R)和连续GF/Pb丝增强橡胶复合材料(T-GF/Pb/R)。采用力滞回线法和振动法考察了复合材料在承受压缩载荷和剪切载荷时的力学性能和阻尼性能,分析了复合材料中存在的阻尼机制。结果表明:使用GF/Pb网(丝)作为增强相能够有效地提高复合材料的压缩力学性能和阻尼性能,但对剪切性能提高效果不明显。复合材料阻尼是多种阻尼机制共同作用的结果,包括材料阻尼、界面微滑移阻尼、Pb的微观塑性变形阻尼。各种阻尼机制对复合材料阻尼性能的贡献与界面面积、界面结合强度等因素有关。本课题还分别研究了频率、复合结构、GF/Pb网(丝)体积分数、GF/Pb网铺层位置和相邻铺层间夹角、组元性能和使用条件等因素对四种复合材料力学性能和阻尼性能的影响,并根据实验结果确定了制备各种复合材料的最佳参数,以及发挥GF/Pb网增强作用的最佳复合结构。不同GF/Pb网(丝)用量对复合材料性能影响的研究结果表明:H-GF/Pb/R和V-GF/Pb/R的压缩刚度和阻尼性能随着GF/Pb网体积分数的增加而提高,其剪切性能受GF/Pb网体积分数的影响不明显;T-GF/Pb/R的动刚度随着GF/Pb丝体积分数的增加而提高,其损耗因子却随GF/Pb丝体积分数增大略为降低。不同铺层结构对GF/Pb网增强橡胶复合材料性能影响的研究结果表明:H-GF/Pb/R的压缩动刚度和阻尼性能随着铺层结构的改变略有差别,当GF/Pb网位于样品中部时,H-GF/Pb/R的综合性能最佳。GF/Pb网铺层间夹角对V-GF/Pb/R的压缩力学性能和阻尼性能影响较小,其中以铺层间夹角为0°、GF/Pb网均匀铺层的复合材料性能最高。GF/Pb丝与橡胶间的界面结合强度对复合材料性能影响的研究结果表明:载荷作用前后的界面状态随界面结合强度的强弱而改变,故GF/Pb丝与橡胶间的界面结合强度成为影响复合材料性能的重要因素。界面结合较弱时,界面处的脱粘区域在受到循环载荷作用后迅速扩展;界面结合较强时,GF/Pb丝与橡胶在受力作用后仍然能够保持紧密结合状态。界面状态的差别导致了复合材料性能的差别,H-GF/Pb/R和V-GF/Pb/R的压缩力学性能随着界面结合强度的提高而提高,而损耗因子的变化较复杂。H-GF/Pb/R的阻尼性能按照界面弱结合、强结合、中等强度结合的顺序提高;V-GF/Pb/R的阻尼性能按照界面中等强度结合、强结合、弱结合的顺序提高。研究了金属组元和直径不同的GF/Pb丝的物理性能及它们所增强的复合材料力学性能和阻尼性能,结果发现:纯Pb比PbSn合金更容易发生微观塑性变形,形成较多的变形能耗,因此,用金属组元为纯Pb的GF/Pb丝制备的的复合材料阻尼性能较高。复合材料中的界面面积、GF/Pb丝分布状态随着GF/Pb丝直径的改变而变化,从而,复合材料的力学性能和阻尼性能也随之改变。GF/Pb网铺层数量相同时,H-GF/Pb/R和V-GF/Pb/R的力学性能和阻尼性能均随GF/Pb丝直径的增大而提高;GF/Pb丝体积分数相同时,GF/Pb丝直径对S-GF/Pb/R力学性能和阻尼性能影响不大,T-GF/Pb/R力学性能随着GF/Pb丝直径的增加而降低,而阻尼性能呈非线性变化。研究了四种复合材料在不同测试条件下的性能,考察了它们在不同使用环境中的减振效果。结果表明:H-GF/Pb/R和V-GF/Pb/R的压缩动刚度和阻尼性能随着预压缩量的增大而提高,随着振幅的增大而降低。复合材料动刚度随着频率的提高而提高。当f<8Hz时,阻尼性能随着频率的提高而提高;8Hz时达到峰值;之后,损耗因子随着频率提高而减小。比较了四种复合材料的力学性能和阻尼性能增强效果,结果表明:H-GF/Pb/R和V-GF/Pb/R的力学性能增强作用较高,V-GF/Pb/R的阻尼增强效果最好。在3~20Hz范围内,GF/Pb网(丝)体积分数为4%时,H-GF/Pb/R样品和V-GF/Pb/R样品的动刚度提高率相当,分别为53%~57%、48%~50%;V-GF/Pb/R的阻尼性能提高率可达到24%~47%。GF/Pb网增强橡胶复合材料的纵向压缩性能比横向压缩性能高,且横向剪切性能比纵向剪切性能高。当压缩载荷作用于V-GF/Pb/R时,复合材料良好的纵向压缩性能和横向剪切性能将同时发挥作用,使其表现出比H-GF/Pb/R更加优异的力学性能和阻尼性能。因此,GF/Pb网纵向增强橡胶复合材料比GF/Pb网横向增强橡胶复合材料更加有利于发挥GF/Pb网的增强作用。借助于有限元软件ANSYS,建立了由橡胶层与GF/Pb网增强橡胶薄层交替铺层构成的简化复合材料有限元模型和GF/Pb丝增强橡胶“单元胞”模型。根据能量法,利用有限元分析所得到的单元应变能预测了复合材料的力学性能和阻尼性能,所得结果与实验值比较吻合。同时分析了界面层的厚度、模量和阻尼性能对复合材料阻尼性能的影响,结果表明:只有当界面相模量高于1.25×108Pa时,复合材料阻尼性能才有可能提高,且界面层的阻尼性能比界面层的模量和厚度对复合材料阻尼性能影响更加明显。最后,为了考察GF/Pb网(丝)增强橡胶复合材料的工程减振效果,按照四种复合方式的优化结构参数和材料参数制备了复合样品,并模拟复合材料的实际应用环境进行了振动测试。结果表明:在3-20Hz范围内,H-GF/Pb/R的动刚度提高率可达到165%~198%,V-GF/Pb/R损耗因子提高率可达到42%~68%。使用复合材料的系统振动传递率仅是使用橡胶系统的一半,显示出了优良的减振效果。另外,将GF/Pb网复合材料应用于某铁道轨枕垫产品中,不仅解决了使用天然橡胶所引起的产品刚度和绝缘性能无法同时满足要求的问题,满足了工程应用要求,而且降低了生产成本。更多还原

【Abstract】 Rubber is an important kind of damping material because of its viscoelastic property, which has been applied in the field of aviation, aerospace, transportation, mechanical engineering and construction industry. However, its mechanical property is so poor that it is very difficult to be used as structural materials independently. In order to get a structural and functional material, a new damping composite was designed and studied in the dissertation based on the theory of composite and damping mechanisms. The ternary composite composed of glass fiber (GF), lead (Pb) and rubber (R) is named as glass-fiber–cored lead-wire(GF/Pb-wire) or woven GF/Pb-wire(GF/Pb-net) reinforced rubber composite (GF/Pb/R).The properties of four kinds of composites with different structures were studied systematically in the dissertation. They were horizontally layered GF/Pb-net reinforced rubber composite (H-GF/Pb/R), vertically layered GF/Pb-net reinforced rubber composite (V-GF/Pb/R), short GF/Pb-wire reinforced rubber composite (S-GF/Pb/R) and continuous GF/Pb-wire reinforced rubber composite (T-GF/Pb/R).The mechanical properties and damping properties of the composites under compressional loading and shear loading were studied by measuring their mechanical hysteresis loops and vibration transmissibility. And the damping mechanism of the composites was analyzed. The experimental results show that the compresssional properties (including mechanical property and damping property under compressional loading) of rubber are improved together by using GF/Pb-wire (or GF/Pb-net) as the reinforcement. But the shear properties don’t change obviously. The improvement of the damping property of GF/Pb/R dues to varied damping mechanisms, including material damping, interfacial micro-slippage damping and microscopic plastic deformation damping of Pb. And their contribution to the damping property of the composite is affected by many factors, such as interface area, interface bond strength and the distribution of stress in the composite, and so on.Furthermore, it was also studied that the influences of frequency, structural parameters, component properties and application conditions to the mechanical properties and damping properties of H-GF/Pb/R, V-GF/Pb/R, S-GF/Pb/R and T-GF/Pb/R.By studying the influence of the volume fraction of GF/Pb-wire (or GF/Pb-net)(VGF/Pb) on the mechanical properties and damping properties of the composites, it tells that the compressional properties of H-GF/Pb/R and V-GF/Pb/R improve with increasing the volume fraction of the GF/Pb-net. However, their shear properties change little. The dynamic stiffness of T-GF/Pb/R increases and its loss factor decreases a little when the volume fraction of GF/Pb-wire increases..By studying the influence of composite structure on the composite properties, it is concluded as follows: the compressional stiffness and loss factor of H-GF/Pb/R change a little with the change of GF/Pb-net layer position in the composite, while those of V-GF/Pb/R change little with the variation of the angle between the neighbouring GF/Pb-net layers. The combination property of H-GF/Pb/R is the best when the GF/Pb-net lies at the middle of the composite. And the property of V-GF/Pb/R is perfect when the angle between layers is 0°and the GF/Pb-nets are laid uniformly.By studying the influence of the interfacial bond strength between GF/Pb-wire and rubber on the properties of composites,it tells that the interface properties are important factors to influence the properties of GF/Pb/R because the changes of interface status after vibration are different for composites with varied interfacial bond strength. The small gaps at the interface enlarged immediately under the cyclic loading when the interface bond strength was weak. However, GF/Pb-wire and rubber still combined tightly after vibration when the interface was bonded strongly. Thus, the energy dissipations were different in composites with varied interface bond strength that their properties differ obviously. The compressional mechanical properties of H-GF/Pb/R and V-GF/Pb/R improve with the improvement of the interfacial bond strength, while their loss factors change irregularly. The loss factor of H-GF/Pb/R is the maximum when the interface bond strength is medium, while that of V-GF/Pb/R is the maximum when the interface is bonded weakly.By studying the physical properties of GF/Pb-wires with different ingredient and different diameter and analyzing the composite properties composed of those GF/Pb-wires, it is concluded that plastic deformation is easier to take place in Pb than in PbSn, therefore more energy dissipation comes into being in the former. So GF/Pb/R prepared with Pb has higher damping properties. Because the interface area and the distribution of GF/Pb-wire (GF/Pb-net) vary with the change of GF/Pb-wire diameter in the composite, the mechanical property and damping property of GF/Pb/R change accordingly. When the volume fraction of GF/Pb-wire or GF/Pb-net is fixed, the mechanical properties and the damping properties of H-GF/Pb/R and V-GF/Pb/R improve with the increase of GF/Pb-wire diameter. And the properties of S-GF/Pb/R change little. While the mechanical property decreases and the damping property changes irregularly for T-GF/Pb/R.By testing the properties of composites under different loading and different vibration amplitude, their vibration control effects were studied. It reveals that the compressional stiffness and loss factor increase while increasing the precompression and decrease while increasing the vibration amplitude. The dynamic stiffness of the composites increases with increasing the frequency. The loss factor increases when the frequency is lower than 8Hz and reaches the peak value at 8Hz, and then it decreases.By comparing the properties of H-GF/Pb/R, V-GF/Pb/R, S-GF/Pb/R and T-GF/Pb/R with 4% volume fraction of GF/Pb-wire or GF/Pb-net within the range of 3~20Hz under the same condition, it is concluded that the compressional mechanical properties of H-GF/Pb/R and V-GF/Pb/R improve more than the others, and their stiffness increase by 53%~57% and 48%~50% respectively. The improvement of the damping property of V-GF/Pb/R is the most distict among the four composites, and its loss factor increases by 24%~47%.In addition, on the basis of energy method, two finite element models composed of rubber lamina and GF/Pb-net reinforced rubber lamina were developed to predict the mechanical properties and the damping properties of H-GF/Pb/R and V-GF/Pb/R in virtue of software ANSYS, respectively. Another finite element model composed of rubber and two orthogonal GF/Pb-wires was also developed to analyze the effect of the loss factor, the modulus and the thickness of the interface on the damping properties of the composite theoretically. The finite element models were proven valid because the predicted results agree with the experimental results well. It is found that the damping properties of GF/Pb/R cannot be improved unless the interface modulus is over 1.25×108Pa. And the damping property of the interface has greater effect on the damping property of GF/Pb/R than its modulus and thickness.At last, four composites with the optimized structure parameters were prepared to discuss their vibration control effect in engineering application. The stiffness of H-GF/Pb/R improves by 165%~198%, and the loss factor of V-GF/Pb/R increases by 42%~68% within the range of 3~20Hz. Vibration test shows that the vibration transmissibility of the system with composites is only half of that of the system with rubber. That’s to say, the composite has greater vibration reducing capability. GF/Pb-nets reinforced rubber can meet the demands of stiffness and insulation for railroad damping cushions while the pure rubber can not. What is more, the producing cost is also reduced.更多还原