The purpose of this thesis is to explore the performance of a bio-inspired plate undergoing oscillatory heave motions and active shape change. The shape change will be achieved using a panel embedded with Fluidic Flexible Matrix Composite (F2MC) tubes for actuation. A beam, or plate strip, model is presented as a means of verifying that F2MC tubes can effectively serve as a means of actuation. This model was actuated in air and water at several internal tube pressures. The static experimental deflections were compared to two beam models relying on Euler-Bernoulli and Timoshenko beam theories with concentrated tip moments and a distributed moment. It was found that the Euler-Bernoulli model with a concentrated tip moment best approximated the static experimental deflections. Following the success of the plate strip, and panel with 10 embedded F2MC tubes was manufactured. The plate panel was constructed with Dragon Skin Silicone and embedded with two rows of five F2MC tubes which provide the means of shape actuation. Experimental results from actuating the panel in static conditions showed that F2MC tubes are an effective means of prescribing a repeatable shape change to a silicone panel. Then, Classical Plate Theory and First-Order Shear Deformation Plate Theory were used with a concentrated tip moment at the free edge to provide a means of modeling the full panel. When comparing the static experimental results to the numerical models, it was found that the deflected plate shape could be most accurately predicted at lower pressures for upward deflection and higher pressures for downward deflections. When tested in unsteady conditions in a heaving experiment (0.5 Hz to 2.3 Hz), the force measured at frequencies above 1.5 Hz were up to 3.6 times greater than those measured for frequencies below 1.5 Hz. Additionally, the phase difference between the tip deflection and force with respect to the keel position decreased for force as frequency increased, while the opposite was true for the tip deflection. At 1.5 Hz, the tip deflection and force were equally out of phase with the keel. When the panel was subjected to an oscillatory heaving motion while asymmetrically actuated, it was found that faster heaving frequencies resulted in higher maximum force values for all actuation pressures, actuation directions, and depths below the free surface. However, when subjected to dual actuation by pressurizing the top and bottom tubes at the same pressure, the tip amplitude was highly dependent on specific combinations of heaving frequency, actuation pressure, and depth below the free surface. This indicates that the actuation pressure must be tuned to the depth and frequency of operation to obtain the desired tip amplitude for a given application. These findings further the knowledge of shape-changing F2MC panels operating near a free surface and lay a groundwork for developing flapping propulsors that mimic marine animals. / Master of Science / The purpose of this thesis is to explore the performance of a bio-inspired plate undergoing oscillatory (up and down) heave motions and active shape change. The active shape change is achieved using Fluidic Flexible Matrix Composite (F2MC) tubes, which act as an artificial muscles to deflect the panel. To verify that F2MC tubes are capable of prescribing a repeatable deflection, a simple beam model with two embedded tubes was manufactured and tested statically in air and water. It was found that the F2MC tubes were able to prescribe a repeatable deflection, and when comparing to two beam models, Euler-Bernoulli and Timoshenko, it was found that the Euler Bernoulli model with a concentrated tip moment best approximated the static experimental deflections. Following the success of the beam model with 2 embedded tubes, a panel was made with 10 embedded F2MC tubes, 5 along the bottom and 5 along the top, was created. This panel was tested statically and dynamically. Static results showed strong deflection repeatability. When subjected to heaving motions, it was found that the force in the system increased with increasing heaving frequency. The phase difference measured between the tip deflection and force with respect to the keel position decreased for force as frequency increased, while the opposite was true for the tip deflection. It was also observed that there exists a point where the tip deflection and force were equally out of phase with the keel. When the panel was subjected to dual actuation by pressurizing the top and bottom tubes at the same pressure, the tip amplitude was highly dependent on specific combinations of heaving frequency, actuation pressure, and depth below the free surface. This indicates that the actuation pressure must be tuned to the depth and frequency of operation to obtain the desired tip amplitude for a given application. These findings further the knowledge of shape-changing F2MC panels operating near a free surface and lay a groundwork for developing flapping propulsors that mimic marine animals.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119080 |
| Date | 23 May 2024 |
| Creators | Johansson, Oscar |
| Contributors | Aerospace and Ocean Engineering, Gilbert, Christine Marie, Philen, Michael Keith, Coutier-Delgosha, Olivier |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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