功能梯度材料与结构中的挠曲电效应及其表征

Flexoelectricity is a universal electromechanical coupling effect in all dielectrics. It can dramatically enhance the electromechanical coupling of nanoscale materials; therefore, it can serve in a wide range of applications such as power energy, micro- and nano-electronics and national defense. Functionally graded materials and structures can increase the lifetime and reliability of devices. The development of functionally graded materials and structures with nanotechnology brings on many new problems; one key for the electromechanical coupling of functionally graded materials and structures is the effect of flexoelectricity. This project focus on the flexoelectricity in functionally graded materials and structures. The governing equations and corresponding boundary conditions will be derived based on the variational principle. Then the effect of flexoelectricity will be studied, qualitatively. Further, corresponding numerical method will be employed and applied to study the electromechanical coupling behaviors of functionally graded materials and structures with consideration of the flexoelectricity. The critical characteristic length scale of flexoelectricity and the character parameters for functionally graded materials and structures will be obtained numerically. The effect of flexoelectricity and the characteristic parameters will be obtained and discussed. The aim of this project is to capture the size-dependent electromechanical coupling behaviors of functionally graded materials and structures. It is also aim to understand the electromechanical coupling mechanism, so that the results obtained in this project will serve as fundamental theoretical works for design and optimization of functionally graded materials and electronic devices.

挠曲电效应广泛存在于电介质材料中，它能极大地提高纳米材料的力电转换能力，因而其在能源、微纳电子、国防等领域具有重要的应用价值。功能梯度材料具有优异的物理性能并逐渐与纳米技术相结合，如何正确考虑功能梯度材料结构中的挠曲电效应是其力电耦合问题的关键之一。本项目拟发展功能梯度材料与结构的力电耦合理论，分析材料梯度性质、挠曲电效应对功能梯度材料与结构力电耦合行为的影响；借助有效的数值方法，模拟功能梯度材料与结构中的挠曲电效应，获得挠曲电效应的临界特征尺寸与无量纲表征，研究力电耦合行为随材料与结构尺寸的变化规律；采用合理的实验方法，测量功能梯度材料的挠曲电系数。通过理论分析，数值模拟和实验测量相结合来揭示材料性质、频率、温度、尺寸等关键因素对功能梯度材料与结构中挠曲电效应的影响。实施本项目将探讨利用挠曲电效应提高器件性能的途径，并为材料与结构的一体化设计提供理论依据。

力电转换材料在能源、微纳电子、国防等领域具有重要的应用价值，挠曲电效应指应变梯度引起的电极化，它是一种广泛存在于电介质中的力电耦合行为，且能极大的提高纳米材料的力电转换能力。功能梯度材料能够调控材料和结构的物理性能并逐渐与纳米技术相结合，如何正确考虑功能梯度材料中的挠曲电效应是理解其力电耦合问题的关键之一。本项目发展了功能梯度材料和结构的力电耦合理论，分析了材料梯度、挠曲电效应对功能梯度材料和结构的力电耦合行为的影响；借助有效的数值方法，模拟了功能梯度材料和结构中的挠曲电效应，获得了挠曲电效应的临界特征尺寸，研究了力电耦合行为随材料、结构尺寸的变化规律；搭建了实验平台，测量了聚合物材料的挠曲电系数和温度依赖特性，为实验表征功能梯度材料挠曲电效应提供了实验基础。通过本项目的实施，探讨了利用挠曲电效应提高器件性能、通过非压电材料制备具有压电响应的复合材料的途径，并为材料与结构的一体化设计提供了理论基础和实验数据。