Comparison of flexoelectric and piezoelectric dynamic signal responses on flexible rings

Abstract

Piezoelectric materials have been widely used for structural sensing due to the linear electromechanical coupling effect. Flexoelectricity, generally existing in all dielectrics, describes the linear inhomogeneous electromechanical coupling phenomena. Previous studies have shown that the direct flexoelectric effect is sensitive to the bending deformation. This study focuses on comparison and differences between two sensing mechanisms, that is, the flexoelectric and the piezoelectric effects, and explores their distinctive characteristics and potential applications. Based on the direct flexoelectric/piezoelectric effects, flexoelectric/piezoelectric materials treated as flexoelectric/piezoelectric sensors are applied to two ring models with identical dimensions. The mathematical models of thin elastic rings laminated with flexoelectric/piezoelectric sensors are established. Open-circuit sensing signals are derived for further evaluation and comparison. Sensing capabilities of these two materials and mechanisms are compared with respect to ring thickness, sensor thickness, and ring radius in case studies. Results show that the piezoelectric sensing signal appears to be sensitive for both bending-dominant and membrane-dominant vibrations, while the flexoelectric signal is much more prominent than the piezoelectric one for sensing of bending-dominant vibrations. For a flexible structure performing transverse vibration, the bending behavior is usually dominant. Thus, the flexoelectric effect could provide an effective alternative for structural sensing.

Comparison of flexoelectric and piezoelectric ring energy harvester

“…Based on the direct flexoelectric effect, the polarization is induced by the strain gradient. Therefore, the transverse electric displacement D 3 is 10 where μ 12 is the flexoelectric constant; ɛ 33 is the dielectric permittivity constant and subscript f denotes the flexoelectric energy harvester in order to differ with the piezoelectric energy harvester discussed in the next section; E 3 is the transverse electric field. The electric displacement is only related to the strain gradient across the transverse direction, which is bending strains.…”

“…7,8 Sensing signals and energy harvesting of non-shell and shell structures, such as beams, circular rings and cylindrical shells, have been initially evaluated. 9–11 However, they only focused on the open-circuit signals and spatial signal distributions for shell modes. Based on the closed-circuit condition, flexoelectric energy harvesting based on different shells are discussed.…”

Flexoelectric control of beams with atomic force microscope probe excitation

“…13–16 Distributed sensing signal based on the double-curvature shell structures had been studied, which can be simplified to beams, cylindrical shells, circular rings and conical shell. 17–20 When considering the external resistance of the external devices, flexoelectric energy harvesters are designed to harvest the vibration energy and closed-loop circuit and flexoelectric energy harvesting theory are studied. 21–24 Since the flexoelectric effect is significant in nanoscale, flexoelectric energy harvester with surface effect in nanoscale is also studied.…”

Distributed flexoelectric modal signals on circular cylindrical shells

“…In contrast, the signals of the flexoelectric sensors on thin shells consists of only two bending components. 23,24 This study investigates the direct flexoelectric electromechanical coupling behavior and evaluates the distributed modal flexoelectric signals of the flexoelectric sensor segments laminated on the circular cylindrical shells. Mathematical modeling of the circular cylindrical shells laminated with flexoelectric patches is presented first, followed by signal analysis of the natural modes of shells.…”