Georgia Institute of Technology, USA
Date(s) : 10/06/2020 iCal
15 h 00 min - 16 h 00 min
This talk reviews our efforts over the past decade on bio-inspired piezoelectric actuation and hydrodynamic thrust generation for aquatic locomotion using fiber-based piezoelectric structures with interdigitated electrodes, namely Macro-Fiber Composite (MFC) structures. Most piezoelectric materials offer large actuation force but small deformation, requiring additional mechanisms for motion amplification. However, MFCs inherently strike a balance between the actuation force and deformation capabilities, offering high performance, ease of fabrication, geometric scalability, robustness, and silent operation. We describe three generations of our relevant research, starting with resonant mean thrust characterization for a bimorph MFC fin in a quiescent water for the first bending mode, enabled by out-of-phase actuation of two vacuum-bonded MFC laminates. The effect of a passive fin extension on the thrust resultant is also discussed over a wide frequency range covering the resonant dynamics. The second generation efforts include the first untethered piezoelectric swimmer in the literature, with thrust levels similar to those of biological fish with similar dimensions. Distributed-parameter electromechanical model of the piezoelectric fin is coupled with semi-empirical hydrodynamic loads from Morison’s equation for fins with different length-to-width aspect ratios, to identify inertia and drag coefficients. Vibration response is coupled with Lighthill’s equation for simple estimates of the mean thrust, confirmed with experimental measurements. The third generation concept contains a streamlined untethered swimmer with 3D printed components, tested both in a quiescent water and under imposed flow. Our early efforts toward actuation with multiple MFCs for 3D thrust vectoring are also discussed. Since piezoelectricity is reversible, the multifunctional concept of using the swimmer as an energy harvester is summarized to generate electricity from underwater base excitation and vortex-induced vibrations. Modeling and analysis of nonlinear structural dynamics of MFC fins under large deformations due to counteracting geometric and material nonlinearities are briefly addressed.
Prof. Dr. Alper Erturk, Georgia Institute of Technology, USA
Woodruff Professor of Mechanical Engineering // Smart Structures and Dynamical Systems Laboratory // G. W. Woodruff School of Mechanical Engineering