Static Aeroelastic Control Using Strain Actuated Adaptive Structures

Abstract

In this study, the feasibility of using representative box wing adaptive structures for static aeroelastic control is examined. A deformable typical section is uti lized to derive the optimal and suboptimal relations for induced strain actuated adaptive wings, and the relations developed are used to design representative adaptive lifting sur faces which are assessed in trade studies. The optimal relations developed showed that op timal adaptive airfoil designs are possible for some realistic configurations, and effective sub-optimal designs can be achieved for others. In addition, the important parameters associated with inducing curvature and twist, thereby altering the lifting forces on the air foil, are determined. The most important of which were found to be the airfoil thickness ratio, the actuation strain produced by the induced strain actuators, and the relative stiff ness ratio of the actuator to the wing skin for both camber and twist control. The stiffness coupling parameter and the wing aspect ratio were also found to be important for twist control. The potential benefits of using adaptive airfoils for aeroelastic control, rather than conventional articulated control surfaces, is demonstrated in trade studies. It was found that greater control authority along with a lower weight penalty is achievable using adap tive aeroelastic structures for a variety of wing designs. Thus, strain actuated adaptive wings may be used rather than conventional lifting surfaces to increase performance while reducing weight, decreasing loads in critical areas, improving the radar cross section, and maximizing the lift-to-drag ratio for many flight conditions.