Shape Memory Alloys for High Temperature and Surface Morphing in the Aerospace Industry: Science

With air traffic expected to double by 2025, rising oil prices and increasing public awareness of the environmental impact, there is a growing demand for novel aeronautical technologies that result in more fuel efficient, lower emission, and quieter air vehicles. A cross-agency initiative, called Next Generation Air Transportation System (NextGen), is charged with transforming the air traffic management infrastructure and the industries comprising the commercial aviation sector. NextGen is a partnership of the FAA, industry, NASA and the Departments of Defense, Commerce and Homeland Security collaborating to develop and implement advanced technologies for commercial aircraft and aviation management. An interdisciplinary team of University of Kentucky faculty, industry partners and NASA researchers are developing advanced high-temperature shape memory alloys (SMAs) that will enable better, "greener," and more versatile air vehicles in support of the NextGen initiative. SMAs are a unique class of functional materials with the ability to change shape depending on applied temperature, stress or magnetic field. Due to their unique properties, such as very high actuation strain, stress, and work output through reversible phase transformation, SMAs are one of key technologies for significant reductions in drag and considerable versatility compared to today's aircraft with fixed aerodynamic surfaces/structures. NASA's Aeronautics Research Mission Directorate develops technology for all flight regimes and the proposed high temperature SMA research addresses the Fundamental Aeronautics A.2 Subsonic Fixed Wing Program. The existing partnerships between Kentucky researchers and collaborators at Glenn and Langley Research Centers are actively pursuing NASA Strategic Outcome Sub-goal 3E, "Advance knowledge in the fundamental disciplines of aeronautics, and develop technologies for safer aircraft and higher capacity airspace systems". This proposal is also strongly aligned with one of Kentucky's five research priority areas: Materials and Advanced Manufacturing. Conventional low temperature SMAs are currently being considered for use in aircraft applications as actuators, vibration dampers, and sensors since they are compact, robust, lightweight, frictionless, quiet, and environmental-friendly (no hydraulic fluids). They also have low aftermarket costs for inspection and maintenance, and high energy density. However, there is an increasing need to develop new alloys with higher transformation temperatures (>100 degrees C) and higher strength to (i) increase their operating frequencies and temperatures, (ii) prevent their premature actuation due to thermal/mechanical changes in environment, (iii) improve their dimensional and thermal stability, and (iv) prolong their fatigue life. Nickel-Titanium-Hafnium (NiTiHf)-based high-temperature SMAs (HTSMAs) will be characterized for aerospace applications, in particular, for actuation and aerodynamic surface morphing of unmanned and micro air vehicles. The primary goal of this research is to bridge the gap between the astonishing properties of this intrinsically intelligent class of materials and the challenging requirements of the aerospace industry. To achieve this goal, the proposed research outcomes are: 1) alloy development to optimize composition and thermomechanical treatments, characterize microstructure, and test cyclic response; 2) surface morphing and shape memory surface development to assess friction and drag coefficients for aerodynamics applications; 3) analytical and numerical modeling of the elastic, plastic and kinematic responses of HTSMA; and 4) further strengthening of the collaborative partnerships between UK, industry and NASA researchers. FORM NRESS-