介电高弹体结构力电耦合分叉行为研究

Dielectric elastomers is one kind of soft active polymers actuated by electrostatic force. Due to the attributes in fast response, large deformation and high energy density, dielectric elastomers are promising candidates for artificial muscles. Electrical breakdown of dielectric elastomers caused by electro-mechanical bifurcation is the key factor for the failure of the structures. Therefore, understanding the bifurcation mechanism of dielectric elastomers is crucial for the design of the related functional devices. The existing researches mainly focus on the bifurcation behavior of dielectric elastomers at material level and with the assumption of homogeneous deformation. Few researches experimentally reported the bifurcation of dielectric elastomer structures with complex geometry and/or under complicated loading conditions, but the underlying mechanisms are far less clear. This project focuses on the nonlinear bifurcation of dielectric elastomers combining finite deformation theory and experimentation. The project aims to, first, establish the critical bifurcation conditions for dielectric elastomer structures undergoing inhomogeneous deformation, analyze the stability of the bifurcation branches, and elucidate the mechanism of nonlinear bifurcation. Second, propose a methodology to analyze the post-bifurcation of representative dielectric elastomer structures, reveal the mechanism of coexistent states and morphology revolutions during post-bifurcation. This project will help to enrich and further develop the multi-field coupling nonlinear theory of soft active solid materials.

介电高弹体是一类静电场驱动型的电活性聚合物，响应速度快、变形范围大、能量密度高，被称为人造肌肉的最佳候选。力电失稳导致电击穿是介电高弹体功能结构失效的首要因素，而力学设计可有效抑制力电失稳。因此，理解介电高弹体的失稳与分叉机理、掌握其分叉规律，对相关功能器件的设计具有重要意义。现有介电高弹体力电失稳理论工作主要局限于材料本身的特性，而未考虑非均匀变形和结构特征带来的影响。部分介电高弹体结构发生非均匀变形的力电失稳复杂现象有实验报道，但其物理机理远未得到很好的理解。本项目拟从多场耦合有限变形理论和实验两方面，研究介电高弹体结构的力电分叉行为，建立力电耦合条件下介电高弹体结构发生非均匀变形的分叉准则，分析各分叉分支的稳定性及影响因素，阐明其非线性分叉机理；建立典型介电高弹体结构的后分叉分析方法，揭示分叉过程中多态共存及形貌演化等规律。本研究将丰富和发展多场耦合非线性固体理论和分析方法。

介电弹性体由于具有响应速度快、变形范围大、能量密度高等优势，在软体机器人领域具有重要的应用前景。力电失稳导致电击穿是介电高弹体功能结构失效的首要因素，而力学设计可有效抑制力电失稳。本项目围绕介电高弹体力电耦合共同作用下的耦合变形机理开展了理论和实验研究，重点研究了内压与电驱动下介电弹性体球囊的异常鼓胀分叉行为、建立了力电耦合条件下介电高弹体结构发生非均匀变形的分叉准则、揭示了力电载荷作用下的面外非线性振动规律；同时研制了新型介电凝胶材料，表征刻画了其优异的力电特性，并基于此类材料设计了新型的介电驱动器和介电传感器；对近十年来国内外学者研究的各类介电弹性体构型的力电耦合大变形行为的理论与实验分析进行了详细的综述，重点分析了各类结构的力电分叉失稳以及后分叉的复杂非线性行为。以上成果在Journal of the Mechanics and Physics of Solids、Science Advances、International Journal of Solids and Structures、Extreme Mechanics Letters、International Journal of Non-Linear Mechanics等期刊发表。