Micro air vehicles (MAV's) and small unmanned aerial vehicles (SUAV) are remotely piloted or autonomous aircraft with a take-off mass range between 50 g and few kilograms. These vehicles, as well as natural fliers such as bats and insects, utilize a variety of elastic wing structures including thin membranes. Over 1,000 bat species worldwide utilize membranes for flight surfaces. Several current wings on MAVs and SUAVs are fabricated with pliant isotropic materials, such as latex or silicone membranes, stretched over a semi-rigid frame or battens.
Stiffness properties of anisotropic bat membranes vary by region within the wing, which could give the animal overall improved flight characteristics. By developing an artificial wing-membrane design characterized by anisotropic properties, researchers will provide a method of advancing synthetic aerial vehicles toward the flight capabilities of natural filers. During the development process, the membrane's non-isotropic properties are achieved through specific material selection, fiber ratio and fiber pretension in a Spandex-fiber reinforced silicone-matrix.
A custom and practical manufacturing process was developed to produce membranes with the required characteristics. Wet layup fiber composite and casting techniques, applied to the selected materials, resulted in a non-isotropic elastic membrane with the desired mechanical characteristics. Theoretical models,
validated with tensile tests, allow for general stiffness property estimation for a given formulation of the new composite membrane. Static pressure differential and wind tunnel tests successfully demonstrated the desired correlation between membrane composition and elastic response to loading conditions. Further development of the manufacturing process for Spandex reinforced silicone membranes will provide positive results as a future MAV wing-membrane material.