多场作用下功能梯度介电晶体材料中的挠曲电效应及其机理分析

由于挠曲电效应具有强力电耦合效应、显著的尺度效应、及对环境温度无特定要求等优点，因此在传感、驱动方面呈现出的优良特性使其在结构健康监测领域具有极大应用前景。本课题针对在力-热-电场共同作用下功能梯度介电晶体材料中的挠曲电效应产生机理进行分析，揭示了材料细观结构、材料梯度分布、温度、应变梯度等因素对材料电极化的影响; 结合细观力学、应变梯度理论和热动力学理论, 建立一种能准确表征功能梯度介电晶体材料挠曲电效应的静电学与力学等宏观性能的本构模型; 在该理论框架下系统地对具有不同材料梯度分布函数材料的热传导、变形与电极化特性等问题进行具体分析，展示该材料与单一的均匀挠曲电材料或传统功能梯度材料相比具有更加独特的优越性，并通过试验测试获得试验数据与其进行比较，验证理论的正确性与有效性。

The flexoelectric effect is characterized by its powerful electromechanical coupling coefficient, remarkable size effect, environmentally friendly, the large strain gradient induced by highly asymmetry and no special requirement for operating environmental and temperature. Consequently, this type of materials will have great development potential in electromechanical conversion materials. In this work, we will conduct in-depth study of flexoelectric effect in functionally graded materials thermo-electro-mechanical field and reveals the influences of microstructure, gradient distribution, temperature and strain gradient on the polarization of flexoelectric materials. Based on the theories of micromechanics, strain gradient and thermodynamics, constitutive models which can accurately characterize the macroscopic properties of functionally gradient flexoelectric materials, such as electrostatics and mechanics properties are established. In this framework, the problems such as heat conduction, deformation and polarization of materials with various material gradient distribution functions are analyzed, systematically. And the results show that this type of functional materials possess more unique superiority than a single homogeneous flexoelectric material or a traditional functionally graded material. Meanwhile, rigorous experiments will be conducted to verify the correctness and validity of the theoretic model.