pair of wires (upper and lower) aligned in a "v"-pattern orientation about the stress relief hole borrowed  more heavily from the design experience of the device of Figure 4.  Figure 4. Pre-prototype benchtop demonstrator tab arrangements, SMA wires mounted on  offset studs in chordwise orientation.  Several base tab materials were evaluated for use, including spring steel, aluminum sheet, and various  plastics. Based upon earlier discussions with Boeing engineers about the desire to remove metals from  rotating components on aircraft to reduce aircraft signatures, it was felt that the tab design could best  support U.S. Army interests if it were made of non-metallic material. Lexan plastic (polycarbonate) was  found to have sufficient robustness to effects of temperature and UV radiation that it became the default  base material for subsequent actuator design concepts. In addition, aluminum was ruled out when it was  determined that the anticipated stresses built up in the outer layers of the base tab material could  experience fatigue failure after many pop-through cycles of the tab actuator.  Since further development called for testing of the tab assembly on a full-size rotor system, most likely  provided from an aircraft manufacturer or helicopter operator, bonding of the tabs to helicopter blades was  required to be a reversible process. Several adhesives and solvents, along with manual installation and  removal techniques, were evaluated for their capability to provide sufficient strength in both shear (to  counter centrifugal loads) and peel (to maintain bond strength during pop-through and under aerodynamic  loading). Tab coupons were manufactured and bonded to aluminum plate and the trailing edge of a  composite CH-47 blade section, in order to evaluate shear and peel strength of the combined tablbonding  agentblade system. Shear tests were instrumented using an in-line load cell, and peel strength was  checked manually. Many bonding agents exhibited good shear strength but poor peel performance. Some  bonding materials showed good strength in both directions, but poor resistance to applied heat. Ultimately,  an epoxy was identified that showed excellent bond strength, and acceptable solvent-based removal  performance, for both metal and composite skin blades; this material was used in all subsequent tests  performed on combined blades and active tab assemblies.  Two-Dimensional (2D) Section Testing  Two separate 20 tests were performed using the active tab assembly. The first was using CDl's 30-cm x  30-cm low turbulence wind tunnel to assess anticipated aerodynamic drag effects of the tab on rotorblade  performance. The second was a high dynamic pressure test, to check the two-position tab's potential to  pop-through under loading when the section is generating significant lift. This latter experiment used a  novel mounting arrangement in order to perform hydrodynamic testing from the side of a small power boat  in the Delaware River. Each is described below.  CDl's low turbulence wind tunnel was used to conduct tests on two-dimensional airfoil sections to  determine the effectiveness of proposed actuation concepts. The 30-cm x 30-cm tunnel can generate up  to 36 mls flows, which, although not representative of the anticipated aerodynamic environment for the  actuators, was suitable for providing a "first look" at aerodynamic drag effects generated by the addition of  trailing edge treatments on the airfoil sections.