【作者】 董旭峰；

【导师】 欧进萍； 关新春；

【作者基本信息】 哈尔滨工业大学 ， 防灾减灾工程及防护工程， 2008， 博士

【摘要】 树脂粘结Terfenol-D颗粒形成的树脂基超磁致伸缩复合材料与Terfenol-D相比具有涡流损耗低,使用频率宽,抗拉强度高,可加工性好,成本低等优点。本文主要从性能理论预测、制备工艺改进、不同工艺因素作用机理分析、性能影响因素实验分析、在土木工程中的应用等五个方面对树脂基磁致伸缩复合材料展开研究。首先,在考虑退磁场效应的前提下,采用复合材料细观力学等效夹杂理论,建立磁致伸缩复合材料的理论模型,研究颗粒形状、含量及基体弹性模量对磁致伸缩复合材料磁致伸缩性能及弹性模量的影响,以及磁致伸缩系数及弹性模量与磁场强度的关系。结果表明,磁致伸缩复合材料的饱和磁致伸缩应变随颗粒含量、纵横比的增大而增大,随基体弹模的增大而减小;弹性模量随颗粒含量、颗粒纵横比、基体弹模的增大而增大;饱和磁场强度随颗粒含量减小或颗粒纵横比减小而增大;颗粒含量越大、纵横比越大,磁致伸缩应变随磁场强度的变化越快;弹性模量随磁场强度的增大而增大,其影响程度在颗粒体积含量和颗粒纵横比较大时尤为显著。其次,针对树脂基磁致伸缩复合材料已有制备工艺中的问题,根据不饱和聚酯树脂低粘度的特性,对已有工艺进行了改进,即先采用超声振荡法使颗粒均匀分散在基体材料中,然后在混合体系树脂凝胶过程中通过电磁场系统施加可调节的强磁场,待凝胶后再将复合体系置于高温条件下固化。实验对比证明,采用改进工艺制备的不饱和聚酯树脂基磁致伸缩复合材料具有颗粒分散均匀、磁致伸缩性能高等优点。继而,对制备工艺流程中影响最终树脂基磁致伸缩复合材料性能的因素进行了讨论。结果表明,制备过程中颗粒分散方法,凝胶过程中取向磁场强度,最后的固化温度等对树脂基磁致伸缩复合材料的性能具有显著的影响。接着,通过实验对取向磁场强度、颗粒含量、颗粒粒度分布、固化温度、基体种类以及掺杂其它颗粒对磁致伸缩复合材料各性能参数的影响进行了讨论分析。结果表明,磁致伸缩复合材料磁致伸缩性能、磁机械耦合系数以及弹性模量、抗压强度等性能参数均随凝胶过程中取向磁场强度的增加而提高,对不同颗粒含量的复合材料存在着不同的取向磁场强度的临界值;磁致伸缩复合材料动静态磁致伸缩系数、磁导率及弹性模量随颗粒含量增大而提高;采用窄分布颗粒制备的磁致伸缩复合材料,其动静态磁致伸缩系数随颗粒平均粒径增大而先增大后减小,而采用宽分布的颗粒所制备的试样其磁致伸缩系数大于所有采用窄分布颗粒所制备的试样;在固化温度小于临界固化温度时,磁致伸缩复合材料的磁致伸缩性能随固化温度的升高而升高,当固化温度超过临界温度时,磁致伸缩复合材料的性能开始下降;相同条件下制备的不饱和聚酯树脂基磁致伸缩复合材料与环氧基磁致伸缩复合材料相比,各性能参数均略有下降;掺杂羰基铁粉在提高磁致伸缩复合材料磁导率的同时降低了其磁致伸缩性能,而掺杂纳米SiO2可以提高树脂基磁致伸缩复合材料的力学性能及低磁场下的磁致伸缩性能。此外,本文还通过实验研究了磁流变弹性体(MRE)的磁致伸缩性能。结果表明,由于羰基铁粉颗粒与硅橡胶基体的相互作用,MRE也具有一定的磁致伸缩效应,其磁致伸缩系数随颗粒含量的增大而增大;在粒子含量相同时,MRE的饱和磁致伸缩量随垂直于磁场方向的颗粒所占比重的增大而增大;实验中测得的最大饱和磁致伸缩量与压电陶瓷材料的压电变形量相当,较Terfenol-D的磁致伸缩效应小1个数量级;MRE的磁致伸缩性能不稳定,其饱和磁致伸缩系数及残余磁致应变随加卸磁场次数增加而逐次减小。最后,设计了一款基于环氧基磁致伸缩复合材料的半主动摩擦阻尼器。小尺寸实验研究表明,以磁致伸缩复合材料棒材为驱动材料的阻尼器耗能性能良好,且性价比较其它材料高。用其对1:16的斜拉索模型进行振动控制实验,结果表明,该阻尼器能够有效减小斜拉索振动,而半主动控制效果更优。更多还原

【Abstract】 Magnetostrictive composites containing Terfenol-D particles dispersed within a polymer matrix presents high advantages when compared to the monolithic Terfenol-D. The higher frequency response of magnetostrictive composites increases power density and widens the design space for employing magnetostrictive materials. This dissertation focuses on the performance prediction, improvement of manufacturing craft, influential factors on its performance and applications in civil engineering of magnetostrictive composites.Firstly, consider the shape of the magnetostrictive particles in magnetostrictive composites was ellipsoid, which can be described by aspect, the relationship between effective magnetic field and applied magnetic field was established based on demagnetization effect. Combined with the relationship between magnetostriction of magnetostrictive particulate and effective field, the relationship between the magnetostriction of single particle to the applied field was also built up. Then treating the magnetostriction of particulate as an eigenstrain, the average magnetostriction of the composites under any applied field as well as saturation magnetostriction was calculated based on Eshelby equivalent inclusion and Mori-Tanaka method. The calculation results indicated that the saturation magnetostriction of magnetostrictive composites increases with increasing particle aspect, particle volume fraction and decreasing Young’modulus of matrix, and the influence of applied field on magnetostriction of the composites becomes more significant with larger particle volume fraction or particle aspect.Secondly, an improved method was developed to overcome the shortcomings of traditional craft of preparing magnetostrictive composites. Magnetostrictive particulates was evenly mixed with liquid resin system by ultrasonic, then large orientation field was applied by an electrical magnetic field system until the resin become gel and the mixture system was supposed to be stable. Then, the mixture was placed in an oven and cured at high temperature for several hours. Test on magnetostriction of polyester resin-bonded Terfenol-D composites prepared by traditional method and improved method indicated the new craft could promote the magnetostrictive properties of magnetostrictive composites. Besides, the mechanism of the influence of dispersion method, orientation field and cure temperature on properties of magnetostrictive composites was discussed.Thirdly, the effects of orientation field, particle volume fraction, particle size distribution, cure temperature, polymer matrix and blending with other particles on properties of magnetostrictive composites were studied by experiment. The study on orientation field indicated that the saturation magnetostriction, the peak dynamic strain coefficient, the magnetomechanical coupling coefficient and the Young’s modulus increase with an increasing orientation field. An optimal orientation field exists, the value of which depends on particle volume fraction, and no obvious improvement of the properties could be expected for an orientation field larger than the optimal value. The study on particle volume fraction indicated the magnetostriction increase dramatically with particle fraction at low particle volume fraction, but slightly at large levels. Both permeability and Young’s modulus increase with increasing particle fraction. The composite with 30% particle volume fraction presents the largest compression strength. The study on particle size distribution indicated that the magnetostrictive properties increase with increasing particle size at small particle size level, but decrease at large size level. Magnetostrictive composite fabricated with polydispersed distribution particles presents the largest magnetostrictive properties. The study on cure temperature indicated that when the operating temperature was a constant, at the same magnetic field level, the magnetostrictive properties, such as magnetostriction, piezo-magnetic coefficient and relative permeability, increase with increasing cure temperature. The study on polymer matrix indicated that magnetostrictive composites fabricated with epoxy resin shows better performance than those fabricated with unsaturated polyester resin. The study on blending with carbonyl iron particles indicated that with the increase of the percentage of soft magnetic powder is the increase of magnetic permeability and decline of magnetostrictive properties. The study on blending with nano-SiO2 indicated the mechanical properties and magnetostrictive properties of magnetostrictive composites at low field can be promoted by blended with nano-particles.Additionally, this dissertation studied the magnetostrictive properties of magnetorheological elastomer (MRE), another kind of magnetostrictive composites which have not been sufficiently studied. Due to the interaction between silicon rubber matrix and carbonyl iron particulates, MRE exhibits large magnetostriction effect. The particles volume fraction is one of the important factors, which have great influence on the performance of MRE. At low-volume fraction levels, magnetostriction effect of MRE increases with increasing particle volume fraction. The increase of percentage of particles, which are aligned in the transverse direction during cure time, is beneficial to the improvement of saturation magnetostriction. The largest magnetostriction observed in tests was 184ppm, which was as large as piezoelectric ceramic, but was an order less than Terfenol-D. The performance of composites lacked repeatability resulted from the hysteresis effect and remnant strain after switching off the applied field; therefore, the magnetostriction of MRE was unstable.Finally, a semi-active friction damper was designed based on the properties of epoxy-bonded Terfenol-D composites with 53% particle volume fraction. Energy dissipation capacity under different magnetic field was tested and compared with the dampers actuated by Terfenol-D and PZT, which indicated the smart friction damper actuated by magnetostrictive composites presented both large tunable damping force and less cost. Then vibration control experimental was done on a model of stay cable by smart friction damper actuated by magnetostrictive composites. The results indicated that this kind of smart friction damper can decrease the vibration of stay cable effectively, especially by semi-active control method.更多还原