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Title: Electromechanical response of bulk PZT 95/5 and associated polymers across temperature and strain rate
Author: Khan, Amnah Sehar
ISNI:       0000 0004 6347 0448
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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Piezoelectricity is the ability of certain, non-conductive, materials to generate an electrical charge when pressure is applied to them. The voltage produced is directly proportional to the applied stress. The amount of charge generated can depend on, for example, the applied strain rate or the temperature. Due to this ability, piezoceramics, such as PZT ceramics, find use in many different applications, primarily as sensors or actuators. Sensors work by detecting pressure, mechanically deforming and thus producing a voltage. Actuators, on the other hand, mechanically deform upon application of an electric field. To develop a better understanding of the piezoelectric ceramic lead zirconate titanate (PZT) 95/5, a range of studies including varying temperatures, porosities, and strain rates have been conducted. The effects on the voltage output and failure of poled PZT samples of different porosities have been investigated using different compressive strain rates (10^-4 – 10^4 s^-1), reached with quasi-static loading equipment, drop-weight towers, and Split Hopkinson Pressure Bars (SHPBs). The main cylindrical specimens were of 4.4 mm diameter, thickness 0.8 - 4.4 mm, and density 7.3 - 8.3 g cm^-3. The temperature range of -20°C to +80°C was achieved using purpose-built environmental chambers. The resulting stress-strain relationships are compared; all the samples ultimately displaying a brittle response at failure [1]. To support this work, ideal geometric specimen sizes were identified for the different types of loading experiment, by carrying out a range of strain-rate compression experiments on well-studied materials such as aluminium and copper. In addition, different experimental platforms were successfully developed in order to reach non-ambient temperatures in the Split Hopkinson Pressure Bar experiments. Finally, as piezoceramics, when used in real world applications, are often coated in protective layers of polymer, several different types of industrial polymer have been characterised across the full range of strain rates and temperatures.
Supervisor: Proud, William Sponsor: AWE (Firm)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral