Development and Application of PP-CNT Composite for Hummingbird Inspired MAV Flapping Wings

Micro Air Vehicles (MAVs) are small unmanned aircrafts which have a maximum size limit of 150 mm in any direction. They can be used for surveillance, reconnaissance, targeting, etc. To perform such missions, MAVs are required to hover. Hummingbirds, having excellent flight characteristics (such as hovering, ability to fly in any direction, ability to produce a reverse camber during upstroke for generating lift in both up-down strokes), have been chosen as the bio-inspiration for wing development. Wings are required to be light, strong and fatigue resistant, to be able to properly flap during flight. Therefore, wing-material becomes a crucial component. An optimization analysis, on the basis of density and fundamental frequency values obtained through Ansys, was done for selecting the wing material. Polypropylene (PP) was observed to have desired properties such as light weight, flexibility, strength, fatigue resistance, good heat and chemical resistance etc. Mixing Carbon Nano Tubes (CNTs) with PP can further increase the strength significantly, making it more suitable for large amplitude flapping. The PP-CNT composites were developed using solution casting method. The films were characterized mechanically (using UTM). The wings were characterized by their structural dynamic properties. The modal analysis of wings was done to obtain natural frequencies and mode shapes. The analysis was aimed to get the fundamental mode in the flapping range (8-15 Hz) of hummingbirds, as resonance increases efficiency. It was also done inside vacuum chamber to observe the effect of air on the natural frequency and modes. The Ansys results were compared with the experiments in vacuum for validation of experimental results. Damping coefficient of wings was also determined. In the end, bio-mimicking of hummingbird wing was also tried by doing some material and structural advancements in the wings.