Shape Memory Alloy Actuated Vortex Generators: Alloy Design

Aerodynamic devices, such as vortex generators, are often used to reenergize flow and improve aerodynamic performance of aircraft control surfaces. Often the static, non-moving surfaces are designed for specific flight conditions and decrease performance, such as increasing drag and fuel consumption, at other conditions. One example is vortex generators (VGs), small vanes located throughout the aircraft surfaces. VGs are typically not required for the entire flight profile but are essential for conditions such as low speeds during take-off and landing. The static nature of standard VGs stems from the inability to adapt conventional actuators due to mass, complexity, or footprint constraints given their small size and placement on outer surfaces of the aircraft. Shape memory alloys (SMAs) present an opportunity to enable actuation of such devices with a minimal mass and dimension, while still providing high energy densities. Additionally, SMAs can be passively used as sensors if carefully "tuned" to respond to the altitude temperature differential and passively actuate without the need for heaters, active controls, or additional sensors and instrumentation. In this work, the authors report on the development of low temperature SMAs for passively actuating VGs based on temperature changes from ground to cruise altitudes.