In the context of aerospace engineering, morphing structures are useful in their ability to change the outer mold line (OML) while improving or maintaining certain aerodynamic performance metrics. Skin-based morphing is of particular interest in that it minimizes installation volume. Shape memory alloys (SMAs) have a high force to volume ratio that makes them a suitable choice for skin-based morphing. Because the thermomechanical properties of SMAs are coupled, strain can be generated via a temperature variation; this phenomenon is used as the actuation method. Therefore, it is necessary to determine the interaction of the system not only with aerodynamic loads, but with thermal loads as well. This paper describes the wind tunnel testing and in situ thermomechanical analysis of an SMA actuated, avian inspired morphing wing. The morphing wing is embedded with two SMA composite actuators and consists of a foam core enveloped in a fiberglass-epoxy composite. As the SMA wire is heated, the actuator contracts, morphing the wing from the original owl OML to a highly cambered, high lift OML. Configuration characteristics are analyzed in situ using simultaneous three dimensional digital image correlation (DIC) and infrared thermography, thereby coupling strain and thermal measurements. This method of testing allows for the nonintrusive, multiphysical data acquisition of each actuator separately and the system as a whole.

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Hannah R. Stroud, Pedro B. C. Leal, and Darren J. Hartl, "Experimental multiphysical characterization of an SMA driven, camber morphing owl wing section," Proc. SPIE 10599, Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XII, 105990Z (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 07, 2018; Published: 29 March 2018); https://doi.org/10.1117/12.2300913.