Phase Transition-Enabled Shape Adaptation for Aerial Platforms

 

Latha Nataraj^1^\*, Cory Knick^2^, Rob Burke^1^, Brendan Hanrahan^1^, Adam Wilson^1^, Scott Walck^1^

^1^U.S. Army Research Laboratory

^2^U.S. Army Combat Capabilities Development Command C5ISR CenterAir vehicle programs continue to strive for large span and sweep changes for high level of adaptability. Having material properties changing from pliable to rigid and vice versa or expanding and contracting on demand would enable the same vehicle to be employed for multiple roles and navigate a variety of flight situations. Such adaptability requires smart materials-based actuation technology involving materials that could transform the shape of the structure to replace conventional actuation systems which add substantial weight to the aircraft.

 

Ionic electroactive polymers (iEAP), electronic EAPs, and thermally-active polymers have demonstrated actuation for flexible components based on various driving mechanisms. Most of the iEAPs are challenged due to slow response times in the range of 0.1−10 seconds. The response time of thermally-active shape memory polymers, which are constrained by low thermal conductivity and damped viscoelasticity, is generally longer than 0.1 seconds. Electronic EAPs can respond as fast as ∼1 ms, but they have high driving voltages, usually over 1 kV, which greatly limits their applications.

 

Vanadium dioxide (VO~2~), a transition metal oxide undergoes a change in its crystallographic structure when heated above its phase transition temperature of 68⁰ C, resulting in drastic transformation of its optical, mechanical, electrical, and magnetic properties. Combining the temperature dependent thermal expansion and actuation of vanadium dioxide (VO~2~) and the excellent electrical conductivity of carbon nanotube (CNT) thin films, actuation with large amplitude, fast response of ∼10 ms, and long lifetime (more than 1,000,000 actuation cycles) has been demonstrated \[1, 2\]. We report the results from the process of VO~2~ film growth and structural and in-situ characterization of its mechanical response to thermal stimulus for application in flexible, bimorph actuators of VO~2~ and graphene laminate to enable adaptable wings for aerial platforms.

\[1\] Rafmag Cabrera, Emmanuelle Merced, And Nelson Sepúlveda, “Performance Of Electro-Thermally Driven VO2-Based MEMS Actuators,” Journal Of Microelectromechanical Systems, Vol. 23, No. 1, February 2014

 

\[2\] He Ma, Jiwei Hou, Xuewen Wang, Jin Zhang, Zhiquan Yuan, Lin Xiao, Yang Wei,, Shoushan Fan,

Kaili Jiang, and Kai Liu, “Flexible, All-Inorganic Actuators Based on Vanadium Dioxide and Carbon Nanotube Bimorphs,” Nano Lett. 2017, 17, 421−428


Phase Transition-Enabled Shape Adaptation for Aerial Platforms

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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