考虑应变强化效应的介电高弹体结构力电耦合非线性振动研究

Dielectric elastomer is one of the typical electro-actuated soft active materials, possessing good performances including large voltage induced deformation, fast response and high energy density, which is considered as a promising material for artificial muscle. When designed into a specific structure, dielectric elastomers usually sustain a large deformation, where strain stiffening inhered in the material plays an important role. Most of the existing work focus on the influence of strain stiffening on the quasi-static behavior of dielectric elastomeric structures including electro-mechanical instability, large deformation, phase coexistence and shape bifurcation. However, the influence of strain stiffening on the nonlinear vibration of dielectric elastomeric structures is still unclear, which limits the design and popularization of dielectric elastomeric structures in dynamic engineering applications. This project aims to conduct a systematic research on the nonlinear vibration of multiple dielectric elastomeric structures by theoretical analysis, experimental measurement and numerical calculation. The focus lies on the vibration characteristics at the equilibrium states in large deformation, which is helpful to reveal the influence of strain stiffening on the nonlinear vibration of dielectric elastomeric structures suffering homogeneous or inhomogeneous deformation. Through the completion of this project, we hope to enrich the understanding on the nonlinear vibration behavior of dielectric elastomeric structures for the colleagues in the fields of research and engineering.

介电高弹体是一类典型的电驱动智能软材料，具有电致变形量大、响应迅速、能量密度高等优异性能，被认为是制作人造肌肉的理想材料。当介电高弹体被设计为具体结构工作时，通常需要其处于大变形状态。对于介电高弹体结构的力电耦合大变形行为，材料固有的应变强化效应发挥着重要作用。现有工作大都集中在应变强化效应对于介电高弹体结构准静态行为的影响，发现并研究了如力电失稳、大变形、相共存、形状分叉等力学特性。而应变强化效应对介电高弹体结构的非线性振动有何影响尚缺乏系统深入的研究，这一现状制约着介电高弹体在动态加载下工程应用的设计和推广。本项目拟通过理论、实验和计算等不同手段，对力电耦合作用下多种介电高弹体结构的非线性振动行为展开系统研究，重点关注结构在大变形平衡位置附近的振动特性，揭示应变强化效应对介电高弹体结构在均匀和非均匀变形场下非线性振动的影响，丰富学界和工程界对介电高弹体结构非线性振动的认识。

智能软材料在外界热、电、光、化学等环境激励下能实现大变形，因其质量轻、价格低、响应迅速等优点，智能软材料在软体机器人等领域得到广泛应用。本项目围绕智能软材料的力学建模与结构设计展开以下两个方面的研究：.一、建立了基于相转换的智能材料本构模型，利用该模型预测了形状记忆聚合物（SMP）材料的形状记忆行为及SMP-弹性体双层复合结构的弯曲行为，理论预测与相应的实验结果吻合很好，为基于SMP的4D打印结构设计提供了有效指导。此外，利用该模型描述了高含水量水凝胶的脱水硬化现象，并与欧拉-伯努利梁理论结合，为大曲率（高达0.7mm^-1）高弯曲刚度（高达10^4 MPa m^3）的复杂三维结构设计提供了理论指导，有效解决了现有4D打印中无法同时实现大曲率与高承载的矛盾。.二、阐明了夹杂图案和夹杂尺寸对形状记忆聚合物-橡胶复合材料的形状固定率和形状回复率的影响。为实现可调控的SMP形状记忆特性，现有工作大多集中在发展新的打印或材料体系。针对这一问题，我们提出了一种新的图案设计策略来3D打印由热敏形状记忆聚合物和柔性弹性体构成的复合材料。实验研究表明，对于相同的材料组分，不同的材料布局会导致形状记忆特性的显著差异。同时，我们用复合材料力学建模和有限元模拟的手段定量预测了实验结果，揭示了材料布局对形状记忆特性影响的内在机理。此外，我们提出了一种基于体元设计的材料性质调控方法。通过对体元尺寸与夹杂含量的合理设计，我们实现了高达三个数量级的存储模量调控以及0~60°C范围的玻璃化转换温度调控，为数字材料的设计制造提供了指导。