介电弹性材料电致动变形及失效规律实验研究

介电弹性功能材料(简称DE)是一种新型智能材料,可在电压驱动下产生厚度与面积变形。为了掌握其在电场作用下的变形以及失效规律,本文通过实验方法研究了在不同的预拉伸量、电极特性、电压频率等条件下,DE材料在电场作用下产生变形的最小电压以及发生电击穿时的失效电压的规律,并对实验现象进行了分析和解释,给出了DE材料维持正常工作的条件,为DE材料的工程应用提供了相应的准则。     

HTS电力技术应用中的液氮高电压绝缘特性研究

针对超导电力装置的低温高电压绝缘问题,通过低温高电压实验装置系统地研究了液氮的绝缘与击穿特性,重点研究了电极形状、电极间距和液体压力等因素对液氮击穿特性的影响规律。结果表明:电极间距越大击穿电压越高;击穿电压随气体压力线性增加;电极形状对室温液氮的击穿电压影响显著,电极间隙的电场越均匀击穿电压越高;电极距离的增大引发电极间隙电场均匀性变差,单位长度的耐压强度随长度的增加而降低;液体压力的增高,不同电极的耐压能力都有不同程度的改善。     

介电弹性体致动器及其应变响应研究

用介电弹性体制作的致动器,具有变形量大、能驱动较大的负载、可塑性很好的特点.给出了一种使用介电弹性体制作基本致动器的方法,对电极、预应变等对该方法制作的致动器的影响进行了实验研究.结果表明,电极的柔软度必须与材料的性质匹配.太硬的电极会使应变变小,而太柔的电极会使薄膜易于击穿.预应变虽减弱了单位电压下的变形量,但却能提高致动器的最大应变量.     

微秒脉冲下两电极开关的低真空击穿特性研究

针对巴申曲线在低真空范围击穿特性尚无详细研究,且只适用于均匀电场的情况,本文研究了10-3～10 Pa低真空范围微秒脉冲下两电极开关击穿特性,在真空击穿试件内进行不同球电极间隙距离的真空击穿实验,探索并总结了其击穿规律。首先,对不同电极间距下放电腔场强分布进行了仿真,结果显示场分布为稍不均匀场,场强最大值集中在电极球面顶点之间。然后采用光学显微镜观察实验后电极表面状态,分析了击穿场强以及离散度随真空度和电极间隙的变化规律。结果表明：阴极烧蚀比阳极更为明显,小间隙下真空击穿主要为阴极引发;击穿场强随气压不断降低而迅速增大,上升斜率先增后减,击穿场强趋于稳定,该现象与真空击穿规律相符合;真空击穿场强离散度也随真空度变大,证明真空击穿的随机性和分散性较大。     

电场活化聚合物的实验研究

通过定量试验研究绝缘弹性体类电场活化聚合物的面积变化率与电压、预拉伸量、中心电极面积与窗口面积之比例、电极厚度之间的关系,首先测定单个因素对变形率的影响,继而运用二次正交回归试验方法分析四个因素对变形率的综合影响,以求获得最大变形率,为后期的器件制作奠定基础。     

HTS电力技术应用中低温氮气的绝缘特性研究

针对超导电力装置的低温高电压绝缘问题,通过低温高电压实验装置,系统地研究了液氮液面以上低温氮气的绝缘与击穿特性,重点研究了高压电极的形状、电极之间的间距和气体压力等因素对低温氮气击穿特性的影响规律。结果表明:在液氮液面以上固定的位置(确保低温氮气的温度一致),电极间距越大击穿电压越高;击穿电压随气体压力近似线性增加;电极形状对低温氮气的击穿电压影响显著,电极间隙的电场越均匀,击穿电压越高。     

空气中微波击穿电场的计算

本文采用扩散控制的微波击穿模型,计算了低气压空气的微波击穿电场.为获得简单而直观的计算方法,利用了直流场中的气体放电基本参量,给出了微波击穿电场的计算过程.通过合理的数学处理,推导出计算微波击穿电场的简单公式.计算结果显示,微波击穿电场与气压的关系呈现出典型的帕邢曲线,即在某个气压时击穿电场最小.最低击穿电场及其对应的气压,也以简单公式的形式在文中给出.用简单公式计算出的击穿电场与文献的实验结果基本符合,表明简单公式是正确的.在此基础上,探讨了影响击穿电场的因素.结果表明,等效直流电场和电子平均温度均与微波频率无关,它们均是气压与特征扩散长度乘积的函数.微波击穿电场并不是气压与特征扩散长度乘积的函数,而是分别受气压、微波频率、特征扩散长度的影响.频率越高,击穿电场越大.特征扩散长度越大,击穿场强越小.     

电极表面状态对像增强器耐压性能的影响

像增强器(简称像管)的耐压性能是影响其增益,背景噪声和分辨力的一个重要因素。引起像管电击穿的原因很多,其中,电极的表面形态在其击穿的起始阶段发挥着重要的作用。本文针对像管特有的高场强微间隙电场结构,通过对不同电极进行耐压测试实验,研究其对像管耐压性能的影响。运用表面形貌测试仪对电极表面进行3D形貌测试,结果表明电极表面微凸起形状和尺寸的不同对像管耐压性能的影响差异显著,提高材料表面光洁度对于提高像管耐压性能有着重要的促进作用,最终为突破高场强微间隙像管工艺制作技术提供理论依据。     

管状介电弹性体驱动器电致应变特性分析

介电弹性体是电场型电活性聚合物的一种,在直流电场作用下,有良好的电致应变特性,去掉外加电场,可迅速恢复到原始尺寸,通过控制电压的大小,可以精确控制变形。本文基于NeoHookean应变能模型,采用ABAQUS有限元软件,开展了材质为丙烯酸聚合物管状介电弹性体驱动器在机电载荷作用下的力学性能有限元模拟,另外,考虑机械预拉伸的影响,开展了管状介电弹性体驱动器机电耦合特性的有限元仿真分析,为管状介电弹性体驱动器的力电特性、变形失效、稳定性的进一步研究提供了一定的理论依据。     

失超引起的气泡对超导体绝缘特性的影响

综述了超导设备在失超情况下液氦中气泡的形成,以及气泡对超导设备的绝缘特性的影响,分析了在均匀和不均匀电场中热传导率、压强及电极表面状况对击穿特性的影响,并探讨了提高失超情况下液氦击穿电压的方法.     

Influence of frequency and prestrain on the mechanical efficiency of dielectric electroactive polymer actuators

The effect of frequency and bidirectional static prestrain on the results of dynamic mechanical measurements of loss tangent for acrylic elastomer films is investigated. These prestrained elastomer films are used in electroactive polymer actuators, sometimes referred to as artificial muscles, where the loss tangent determines the mechanical efficiency of the actuator. It is found that mechanical efficiency of the actuator increases with increased bidirectional prestrain, and decreases with increased frequency.     

Synthesis, structure and properties of a novel hybrid bimodal network elastomer with inorganic cross-links: The case of silicone–nanocrystalline titania

We describe an innovative concept of synthesizing a novel hybrid bimodal network elastomer with high strength–high ductility combination involving utilization of functionalized nanocrystalline titania as short-chain cross-links between neighboring elastomer chains. This subject is germane both fundamentally and from an application viewpoint. Silicone rubber is selected as the model elastomer. The short-chain cross-links are acrylic acid functionalized nanocrystalline titania that are an integral component of bimodal network structure of the elastomer. To delineate and separate the effects of functionalization from nanoparticle effects, a relative comparison is made between silicone rubber–titania nanocomposite (i.e. containing dispersion of titania as a reinforcement filler) and silicone rubber–titania hybrid network elastomer (i.e. titania as short chain cross-links). An important finding is that the effect of functionalized titania present as short chain cross-links is far more significant than non-functionalized titania present as reinforcement filler, on mechanical behavior. This is presently ascribed to the double bonds introduced to nanocrystalline titania via functionalization with acrylic acid that provide active sites for the cross-linking reaction resulting in inorganic bridging chains. The basic physical mechanisms that govern elastic recovery in hybrid bimodal network elastomer with short chain cross-links of functionalized nanocrystalline inorganic particles are discussed. The hypothesis of the study described here is that the hybrid bimodal network elastomer with short chain cross-links of functionalized nanocrystalline inorganic particles modifies the unimodal long chain network elastomer with consequent increase in modulus and high strength–ductility combination.     

相容剂对长玻纤增强热塑性聚氨酯弹性体/聚乳酸复合材料性能的影响

采用熔体浸渍工艺制备长玻纤增强热塑性聚氨酯弹性体(TPU)/聚乳酸(PLA)复合材料;以苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯(SAG)作为相容剂,热塑性弹性体聚氨酯作为增韧剂,聚乳酸为基体树脂,考察苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯用量对长玻璃纤维增强聚TPU/PLA复合材料性能的影响。结果表明,加入苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯能改善长玻璃纤维增强聚TPU/PLA复合材料的相容性;长玻璃纤维增强聚TPU/PLA复合材料的拉伸强度、缺口冲击强度、弯曲强度和模量等力学性能及储能模量随着苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯用量的增加呈先增加后降低的趋势,而长玻璃纤维增强聚TPU/PLA复合材料的损耗因子则随苯乙烯-丙烯腈接枝甲基丙烯酸缩水甘油酯含量的增加呈现降低后增加的趋势;通过复合材料的形态分析表明,加入相容剂的复合材料中玻璃纤维与基体树脂界面强度增加,且玻璃纤维表面有一层包覆的树脂基体;通过分析得出,当相容剂添加量为6%时,长玻璃纤维增强聚TPU/PLA复合材料的拉伸强度、弯曲强度和模量、缺口冲击强度等力学性能最优。     

Dielectric elastomers – numerical modeling of nonlinear visco‐electroelasticity

Dielectric elastomer actuators that can directly turn electrical energy into mechanical energy belong to the group of electroactive polymers. This type of electroelastic material exhibits large displacement characteristics and is able to change its mechanical behavior in response to the application of an electric field. Dielectric actuators are made out of elastomers which in general show viscoelastic behavior. To take this time dependent effect into account, the deformation gradient is multiplicatively decomposed. The paper is focused on the numerical modeling of soft dielectric elastomers. The theoretical foundation and the consistent finite element implementation is outlined based on the laws of electricity and elasticity. Furthermore, numerical examples of the nonlinear visco‐electroelasticity model are shown. Copyright © 2012 John Wiley & Sons, Ltd.     

2-Methyl oxazoline-grafted carbon nanofibers: preparation, characterization and their role in elastomeric actuators

Convex surface modification of carbon nanofibers (CNFs) through covalent functionalization plays a pivotal role in the world of polymeric nanocomposites. The free radical ‘grafting from’ technique was successfully applied for the first time for synthesis of 2-methyl oxazoline-grafted carbon nanofibers (Oxa-g-CNF). The resulting Oxa-g-CNF was characterized by infrared spectroscopy, thermogravimetric analysis and wide angle X-ray studies. Moreover, the synthesised Oxa-g-CNF was utilized for the preparation of acrylic elastomer-based nanocomposite targeted for model elastomeric actuators by solution casting technique. The nanocomposite showed excellent increase in relative permittivity proportional to actuation pressure, when compared with pristine acrylic elastomer and commercial materials. The improvement of properties was ascribed to excellent interaction between modified carbon nanofibers and polar group of acrylic elastomer. This technique adopted promises to open up a new avenue for facile preparation of acrylic elastomeric actuators.     

共混型热塑性弹性体的形变机理

热塑性弹性体的性能与其相形态密切相关。文中简要综述了与共混型热塑性弹性体相形态相关的几个参数,包括两相相容性、橡胶相的粒径、塑料相的结晶度。重点介绍了共混型热塑性弹性体形变机理的几种模型,包括不均匀变形、有限元模型、微孔模型等。最后对其发展进行了展望。     

Electromechanically driven variable-focus lens based on transparent dielectric elastomer

Dielectric elastomers with low elastic stiffness and high dielectric constant are smart materials that produce large strains (up to 300%) and belong to the group of electroactive polymers. Dielectric elastomer actuators are made from films of dielectric elastomers coated on both sides with compliant electrode material. Poly(3,4-ethylenedioxythiophene) (PEDOT), which is known as a transparent conducting polymer, has been widely used as an interfacial layer or polymer electrode in polymer electronic devices. In this study, we propose the transparent dielectric elastomer as a material of actuator driving variable-focus lens system using PEDOT as a transparent electrode. The variable-focus lens module has light transmittance up to 70% and maximum displacement up to 450. When voltage is applied to the fabricated lens module, optical focal length is changed. We anticipate our research to be a starting point for new model of variable-focus lens system. This system could find applications in portable devices, such as digital cameras, camcorder, and cell phones.     

非线性电活性绝缘弹胶物DE的应变能模型材料常数

应用Mooney-Rivlin、Yeoh和Ogden应变能模型研究DE材料驱动建模。首先根据单轴拉伸实验数据,分析文献中的材料常数和本文DE材料的适合程度,发现文献中的材料常数均不适合本试验中的绝缘弹胶物(DE)材料变形特性;进一步根据试验数据及理论模型回归分析求出适合本试验变形范围内的DE材料的材料常数。结果表明,Mooney-Rivlin模型不能很好地反映非线性特征,Yeoh和4参数及6参数的Ogden模型均能反映DE材料的非线性特征。     

Reversible mechanical actuation of elastomeric nanopores

Mechanical resizing of individual nanopores in a thermoplastic polyurethane elastomer has been characterized. Specimen nanopores were conical, with smaller hole dimensions of the order of tens to hundreds of nanometres. Electrophoretic current measurements show that the estimated nanopore radius can be reversibly actuated over an order of magnitude by stretching and relaxing the elastomer. Within a working range of stretching, current is proportional to specimen extension to the power of a constant, n, which ranges from 0.9 to 2.3 for different specimens. The data indicate that scaling of the effective pore radius is super-affine. At strains below the working range, the pore size is relatively unresponsive to stretching. Macroscopic elastomer extension has been related to local radial strain (50-250?μm from the pore) using optical microscopy. Scanning electron microscopy and atomic force microscopy have been used to observe membrane surface features.