High Authority Airfoil Camber Control Using Shape Memory Alloys

One advanced structural concept with enormous potential is the active control of wing camber. Current wing designs are compromises at all but one optimal airspeed. The capacity to alter camber as flight conditions change will provide greater lift and maneuverability, reduced dray, increased range, lower fuel consumption, and reduced operating costs. Smart materials such as magnetostrictive Terfenol-D have important advantages such as no bearings, simple construction, low maintenance, and electric operation. Past efforts using smart materials for camber control have been limited by the low energy density of the materials used. Use of shape memory alloys (SMA) has not been explored in depth. The proposed work utilizes the SMA Nitinol because it produces greater than 3% strains while competing "giant" magnetostrictive materials are limited to .15% strain (1,500 parts per million). Large control authority is the enabling feature of the SMA camber actuator. Response of SMA actuators is typically slow because of thermal effects; however, the camber actuator need react only to slow flight regime changes. Various means of SMA camber actuation are proposed including direct drive and SMA composite materials which will be fabricated. Experiments will measure the performance of SMA camber control, and in-service feasibility will be determined.