Discipline: Technology and Engineering
Room: Marriott Balcony A
George Barton - Parkland College
Co-Author(s): Co-authors: Logan Mckee1 and Balaji Iyengar2 1 University of Illinois at Urbana Champaign 2 Parkland Community College
This research focus on an unmanned flapping wing unmanned aerial vehicle, referred to as an ornithopter. Compared to birds, current ornithopters are highly inefficient, especially when it comes to power consumption. An ornithopter’s power efficiency can be improved through augmenting the wing kinematics such that the wing area is reduced during the upstroke and extended during the downstroke. Reducing the wing surface area can reduce drag and improves power consumption. This difference in the wing kinematic is referred to as an asymmetric wing gait. During this research, a variable stiffness hinge was attached to the leading-edge spar to achieve an asymmetric gait. This hinge is made using an 3D printer and using polylactic acid (PLA) and TPU-95A for the materials. PLA is a stiff plastic, which was used to create the mount and locking mechanisms for the hinge. TPU-95A is a flexible rubber-like, which was used for the compliant part of the hinge. When combining flexible and hard materials, it is critical to investigate the interface between both materials because the interface is the location at which failure occurs in most instances. Testing the interfaces between PLA and TPU-95A was performed for various types of interfaces namely, Straight, Teethed, T, and Pincer. The interfaces were tested in two directions, perpendicular and longitudinal. In each direction, a sample containing both materials and a given interface was clamped down on one end and a weight was attached to the other end. This weight applied was increased from 100g, 200g, 500g, 1000g and finally to 2000g. The focus of the tests is to determine the strength of each interface, given that the asymmetric hinge will need to stay together under significant and cyclic aerodynamic forces. Failure in the interface is designated as significant delamination of the PLA and TPU-95A. Results show that, in the longitudinal direction, all samples did not delaminate. Conversely, when tested in the perpendicular direction, the Teeth and T interfaces failed at 2000g, while the Straight and Pincer interfaces failed at 1000g. These results indicate that as the surface area increases between PLA and TPU the more resistant the interface is to failure. Results also indicate that the interlocking geometry between both materials helps resist delamination. Given the results of the interface experiments, two interface designs were used in the asymmetric hinge design namely, Teeth and T. These interfaces allowed the asymmetric hinge to hold together during testing, where the ornithopter flapped its wings at frequencies up-to 5 Hz. Future work includes using a more flexible thermoplastic in the hinge design, such that the weight and size of the hinge can be reduced without affecting the wing kinematics. In addition, an exploration in how these geometries compare is suggested. Standardizing the area of contact in testing samples and a determining a metric to quantify the delamination during strain are needed.
Funder Acknowledgement(s): This work was supported by the National Science Foundation Research Experience and Mentoring site of EFRI NewLAW #1741565
Faculty Advisor: Aimy Wissa, firstname.lastname@example.org
Role: My main focus was productions of an asymmetric hinge. This production includes testing strength between thermoplastics, assisting in hinge design, maintaining a 3D printer and over seeing physical printing.