多场耦合作用下的介电弹性体智能软材料及其应用器件的稳定性、宏观失效和微观破坏机理研究

To address the problems of failure and damage of dielectric elastomers and their devices which are common in their practical applications, research work will be carried out on the stability, macroscopic failure, optimization design theory as well as microscopic damage mechanisms of dielectric elastomers and their devices subjected to thermo-electro-mechanical coupling fields. The failure behavior as well as the generation and growth of cavities will be experimentally characterized for dielectric elastomers and their devices under thermo-electro-mechanical coupling loads. The basic thermodynamic theory of dielectric elastomer thermo-electro-mechanical coupling systems will be constructed and the constitutive relation will be derived. Furthermore, the stability of the dielectric elastomers and their devices will be inverstigated. In-depth discussion will be presented about effects of prestretch, elastomer chain length, strain hardening, polarization saturation and temperature on the stability of dielectric elastomers with multi-field coupling load conditions. According to previously conducted corresponding experimental investigation, this project aims to develop a mechanical model of the macroscopic failure or damage of dielectric elastomers subjected to thermo-electro-mechanical coupling fields, as well as build the optimization design theory of application devices based on this kind of materials. This project will provide the fundamental threoretical guide for future design and manufaction of high-performance devices based on dielectric elastomer. In addition, the generation and growth of inner cavities and perforation between adjacent cavities will be studied for dielectric elastomers on which mechanical force fields, electric fields and thermal fields act synergetically. The influence of surface energy will also be discussed in details. Finally, mechanisms of microscopic damage and failure will be proposed for dielectric elastomer soft materials under multi-field coupling loads.

本项目针对介电弹性体及其器件在实际应用中经常出现的失效和破坏问题，提出介电弹性体及其器件在热机电耦合场作用下的稳定性、宏观失效、优化设计理论和微观损伤破坏机理研究。实验表征介电弹性体在热机电耦合场作用下失效行为、空穴产生和增长行为。构建介电弹性体热机电耦合系统的热力学基本框架，推导其本构关系，研究弹性体及其器件的稳定性。深入探讨预拉伸、弹性体链长、应变硬化、极化饱和、温度等诸多因素对多场耦合作用下介电弹性体稳定性行为的影响。基于已进行的实验研究，发展热机电耦合场作用下介电弹性体宏观失效或破坏的力学模型，建立基于此类材料制备应用器件的优化设计理论，进一步应用此理论设计和制备高性能应用器件。进行介电弹性体在机械力场、电场和热场耦合作用下材料内部微观空穴的产生、增长和相邻空穴的贯通问题的研究，探讨表面能的影响，提出弹性体软材料在多物理场耦合作用下的微观损伤和破坏机理。

介电弹性体是一种典型的智能软活性材料，在外加电场下，可以产生大变形，具有高弹性能密度、超短反应时间和轻质量等优点，被广泛应用于人工肌肉、转换器等方面，在智能仿生、航空航天等领域具有巨大的应用潜力。本项目针对介电弹性体及其器件在实际应用中经常出现的失效和破坏问题，提出介电弹性体及其器件在热机电耦合场作用下的稳定性、宏观失效、优化设计理论和微观损伤破坏机理研究。本项目进行了介电弹性体在热力电耦合场作用下的拉伸断裂、电击穿、热击穿、失稳击穿等实验，实验表明发现在一定拉伸范围内，临界击穿电压随着预拉伸应变的增大而减，较高的温度使介电弹性体试件的力学性能降低；建立了介电弹性体在热力电耦合场下的的本构模型，研究机电稳定性和跳突稳定性，完成了电致变形电击穿理论研究。计算了高电场作用下引起的熵变化和温度变化；建立等温状态下超大变形的介电弹性体驱动器等应用器件的非线性平衡方程，考虑不同结构的介电弹性应用器件的多种失效模式，描绘器件的允许区域，提出介电弹性体应用器件的优化设计理论；建立了介电弹性体材料内部拉伸过程中空穴生长的力学模型，理论分析了温度对空穴的生成的影响，发现当温度较高时空穴更容易生成和增长。并实验观测了介电弹性体薄膜内部空穴的形成，进一步表明其对材料失效存在影响。