3D Multiscale Modelling and Characterisation of the Coupled Electromechanical Behaviour of Novel Smart Piezoelectric Nanocomposites

*背景：我新提出的研究计划的目的是产生新的知识，以准确建模、表征和开发下一代用作传感器、执行器和能量采集器的轻量级智能压电纳米复合材料(SPNC)，并更好地了解控制其机电行为的基本参数。新的SPNC是用有限间距的优先排列的纳米线阵列(NWS)制备的，并被环氧树脂基质中的纳米级表面电极包裹。由于其优异的机电性能，氧化锌和氮化镓纳米晶被选中。压电系数定义了NWS和SPNC的机电行为；在小场条件下，这些系数与温度有关。*研究计划：长期目标是产生新的知识，从而产生新的SPNC设计和分析工具，需要以下短期目标：*1.通过使用新型混合分子动力学(MD)-密度泛函理论(DFT)对被环氧基质包围的NW施加恒定电场下的机械应变，确定均匀传感光纤的有效机械性能和直接压电系数。*2.使用DFT-MD计算均匀驱动纤维的有效力学性能和逆压电系数。*3.通过使用3D分层多尺度策略放大目标1中开发的有效传感器光纤的网络来确定SPNC的体机电性能。*4.使用改进的微观力学和均化方案以及新的网络识别策略，通过放大目标2中开发的有效致动器纤维的网络来计算SPNC的整体机电性能。*5.开展广泛的实验工作，包括测量支配核武和特殊核物质行为的参数，这将指导各自的原子论和连续体模型，并验证它们的预测。这些纤锌矿纳米结构的掺杂、缺陷、去极化和温度在很大程度上所起的作用将在目标1-5中进行研究。*意义：SPNC被设想为下一代民用和军事应用的构建块，其特征是适应性、多功能和自主的传感、致动和能量收集。这项研究将开创一项技术，以表征热电机械加载对压电系数的影响，克服单片压电陶瓷的众多限制，开发高度通用的智能纳米复合材料，解决现有文献中的异常和不足，培训66名HQP，并促进向加拿大工业和军方转移技术。

***BACKGROUND: The aims of my newly proposed research program are to generate new knowledge to accurately model, characterise and develop the next generation of lightweight smart piezoelectric nanocomposites (SPNCs) for use as sensors, actuators and energy harvesters, with greater understanding of the fundamental parameters that govern their electromechanical behaviour. The new SPNCs are fabricated using preferentially aligned array of nanowires (NWs) with finite interspacing and encased by nanoscopic surface electrodes in an epoxy matrix. Due to their outstanding electromechanical properties, Zinc Oxide and Gallium Nitride NWs are selected. The piezoelectric coefficients define the electromechanical behaviour of NWs and SPNCs; beyond the small field condition, these coefficients are temperature dependent. ******RESEARCH PROGRAM: The long-term aims are to generate new knowledge leading to new SPNCs' designs and analysis tools, requiring the following short term objectives:***1. Determine the effective mechanical properties and the direct piezoelectric coefficients of a homogenised sensor fiber for the direct piezoelectric effect by applying mechanical strain at constant electric field using novel hybrid molecular dynamics (MD)-density functional theory (DFT) to a NW surrounded by an epoxy matrix. ***2. Compute the effective mechanical properties and the converse piezoelectric coefficients of a homogenised actuator fiber for the converse piezoelectric effect using DFT-MD. ***3. Determine the bulk electromechanical properties of SPNCs by scaling up a network of the effective sensor fibers developed in Objective 1 using 3D hierarchical multiscale strategy. ***4. Compute the bulk electromechanical properties of SPNC by scaling up a network of the effective actuator fibers developed in Objective 2 using modified micromechanics and homogenization schemes and a new network recognition strategy. ***5. Conduct extensive experimental work that involves the measurements of the parameters that govern the behaviour of NWs and SPNCs, which will guide the respective atomistic and continuum models and validate their predictions. The largely unknown role of doping, defects, depolarisation and temperature of these wurtzite nanostructures will be examined in Objectives 1-5.******SIGNIFICANCE: SPNCs are envisioned to be the building blocks of next generation civil and military applications, characterised by adaptability, multifunctionality and autonomy for sensing, actuating, and energy harvesting. The research will pioneer a technique to characterise the effect of thermo-electro-mechanical loading on the piezoelectric coefficients, overcome the numerous limitations of monolithic piezoceramics, develop highly versatile smart nanocomposites, address anomalies and deficiencies in existing literature, train 66 HQP, and facilitate technology transfer to Canadian industry and military.