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

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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.