The overall goal of this research is to develop design optimization methodologies for compliant mechanisms that will provide passive shape change. We aim to understand the structural mechanics and to demonstrate feasibility of novel passively morphing mechanical bird (ornithopter) wings. These passively morphing ornithopter wings require no additional power demands but can be tailored to provide more lift for takeoff or more thrust for forward flapping flight. A passively morphing wing will be designed to mitigate the detrimental impact of increased drag on the upstroke from a rigid wing by allowing the outer-most section of the wing to deflect downward, while maintaining the thrust performance of a rigid wing during the flapping downstroke cycle.
First, a single degree of freedom mechanism, the Compliant Spine (CS), allowed large deformations during upstroke via a thin compliant hinge while only allowing small deformations during downstroke due to surface contact. Then, the compliant hinge was rotated, which allowed the new Bend and Sweep Compliant Element (BSCE) to be tailored for deflections in the sweep direction. The Twist Compliant Element (TCE) allowed large rotations about its central axis in one direction while only allowing small deflections in the other direction via surface contact. We are currently using a novel Bend-Twist-and-Sweep Compliant Mechanism (BTSCM) which incorporates all three degrees of freedom into a single compliant mechanism.
Image adapted from Morpheus Lab
The BTSCMs, or, more generally, contact-aided compliant mechansisms, can be inserted into the wing structure to improve flight dynamics and agility.
Example of a BTSCM 
An example of the optimization algorithm running. The top left plot shows the design criteria, the bottom left shows the convergence metric. The two right plots show the Finite Element Analysis results of each design. Marker size is the relative mass of each design, and color is the peak stress in the mechanism. 
These mechanisms have been optimized for deflections. Each optimization problem has maximized deflections for “upstroke,” minimized deflections for “downstroke,” and minimizes stress and mass for both cases. We set a cutoff stress, then a Pareto front of optimal designs is available for a designer to choose from. However, to be more accurate for flight conditions and optimize using a flight metric, our next step is to have a full spar and furthermore full wing model. Throughout the modeling process, we using experimental data from our collaborators from The University of Maryland as model verification.
Dr. Mary Frecker, Pennsylvania State University
Dr. James E. Hubbard Jr., University of Maryland
Joseph Calogero, Pennsylvania State University
Dr. Zohab Hasnain, University of Maryland
Air Force Office of Scientific Research (AFOSR)
 Calogero, J., Frecker, M., Hasnain, Z., and Hubbard Jr., J. E., 2016, “A Dynamic Spar Numerical Model for Passive Shape Change,” accepted for publication in Smart Materials and Structures.
 Calogero, J., Frecker, M., Hasnain, Z., and Hubbard Jr., J. E., 2015, “A Dynamic Spar Numerical Model for Passive Shape Change,” SMASIS, ASME, Colorado Springs, CO, USA.
 Calogero, J., Frecker, M., Wissa, A., and Hubbard Jr., J. E., 2014, “Optimization of a Bend-Twist-and-Sweep Compliant Mechanism,” SMASIS, ASME, Newport, RI, USA.