界面层和弱界面对多铁性层合板、柱断裂行为的影响研究

Layered multiferroic devices have a broad application prospect in modern high-tech fields such as intelligent control and tests, information transmission and storage, and etc. Due to the brittleness of multiferroic ceramics, fracture is the most common failure mode of these devices, which has been a hot spot in the research field of smart composites. Therefore, fracture investigation is significant to the performance optimal design and safety assessment of multiferroic structures. Based on our earlier work, the present project aims at performing theoretical analyses, numerical simulations and experimental tests on layered multiferroic plates and cylinders containing interfacial layers and/or weak interfaces. Theoretical research is focused on the following key problems: (1) the improvement of the current algorithm of non-homogeneous element to enhance the simulation precision inside the element; (2) the problem of a non-homogeneous interfacial layer with different material properties complying with different distribution laws; (3) the coupling problem of magneto-electro-mechanical damages and the frictional slippage problem of a weak interface. The purpose of the present project is to reveal the effects of some key factors, such as the non-homogeneous distributions of the properties of interfacial layers, the coupled magneto-electro-mechanical damages and the frictional slippage of weak interfaces, on the fracture behavior of layered multiferroic plates and cylinders. The theoretical models of the project are established by considering the practical problems in the manufacture and applications of layered multiferroic structures. Therefore, the research findings can provide theoretical references to the anti-fracture optimal design of this kind of smart devices.

层状多铁性器件在智能控制与测试、信息传输与存储等高技术领域具有广阔应用前景。断裂是其常见失效形式，也是该领域备受关注的热点问题。断裂力学研究对于该类智能器件的性能优化设计和安全评估具有重要意义。本项目拓展和深化前期工作，针对多铁性层合板、柱这两类典型结构中存在的非均匀界面层和弱界面问题，以理论分析和数值模拟为主、实验测试为辅开展断裂研究。在理论上重点研究如下关键问题：（1）改进现有非均匀单元算法、提高非均匀界面层模拟精度的问题；（2）非均匀界面层不同物性参数服从不同分布规律的问题；（3）弱界面力、电、磁损伤耦合问题与摩擦滑动问题。在认识上重点阐明界面层物性参数的非均匀分布、弱界面的力电磁损伤耦合和摩擦滑动等关键因素对多铁性层合板、柱断裂行为的影响规律与机理。本项目的研究对象和理论模型均抽象自层状多铁性器件制造和应用的实际，因而相关研究成果可为该类智能器件的抗断裂优化设计提供理论依据和参考。

随着智能器件的多功能化和小型化，作为其核心材料的多铁性复合材料成为学术界关注的焦点。多铁性器件常在力电磁载荷下工作，其内在的脆性使其难免发生开裂。因此，断裂研究成为该领域的一项重要任务。对多铁性层合材料而言，界面是关键部位。实际工程中，制造过程的高温高压可使结构产生非均匀界面层，应用过程的苛刻工况则可使银胶产生老化损伤而形成弱界面。因此，在多铁性层合材料的断裂研究中，十分有必要探索非均匀界面层和弱界面的影响。. 本项目以多铁性层合板、柱两类典型结构为对象，通过开展理论建模分析、数值模拟和实验研究，揭示了其断裂行为特征与机理，取得了若干研究成果：(1)建立了多铁性层合材料的耦合弱界面模型，研究了弱界面的损伤耦合对多铁性层合板、圆柱、圆柱壳等典型结构断裂行为的影响规律；(2)建立了裂纹和损伤界面的“共轴”与“非共轴”两种分布位错模型，基于不同分布位错之间的相互作用规律，阐明了含损伤耦合界面的多铁性层合材料断裂行为的广义位错机理；(3)建立了多铁性层合材料的损伤耦合滑动界面模型，提出了局部阻滑/促滑的概念，揭示了含滑动界面的多铁性层合材料断裂行为的局部阻滑/促滑机制；(4)分别建立了多铁性层合材料均匀和非均匀两种磁电弹界面层的理论模型，研究了界面层对断裂行为的调控特性；(5)提出了磁电弹非均匀单元改进算法，开发了相应的有限元程序，推导了计算裂纹闭合积分的新公式，并对多铁性层合材料开展了有限元模拟计算，阐明了不同材料参数服从不同分布规律条件下多铁性层合材料的断裂行为特征；(6)开展了必要的铁电/铁磁双材料断裂力学实验研究。本项目在国际期刊发表论文12篇，全部被SCI检索，相关研究成果可为多铁性层合材料的防断裂优化设计提供理论参考。