|M.Sc Thesis||Department of Mechanical Engineering|
|Supervisor:||Assoc. Prof. Abramovich Haim|
|Full Thesis text - in Hebrew|
The conventional design approach of airborne vehicles such as missiles, UAV’s and Micro UAV’s includes movable control surfaces attached by hinges and actuated by either electromechanical, pneumatic or hydraulic actuators. As the requirements for airborne vehicles efficiency become higher, the need for more efficient control methods is required. In recent years the study of smart materials such as piezoceramic and shape memory alloys have achieved high performance products motivated mainly by the requirements of aerospace industry. By using smart materials to change the shape of airborne vehicle lift surface we can achieve a light weight control surface with minimum drag and maximum aerodynamic efficiency.
This research presents a new design concept for a smart control fin. The design includes a morphing airfoil skin made of passive composite materials combined with active layers of piezoceramic Macro fiber Composite (MFC) actuators.
One of the challenges was to find the optimal design configuration that would achieve high actuation twist angles from one hand and be enough rigid to withstand aerodynamics loads with minimum deflection on the other hand.
The airfoil twist deformation can be achieved by several lamination and electrical field polarity configurations; three actuation methods are suggested:
Shear actuation- the piezoceramic layers are oriented at +45° and -45° to the wing axis, by applying an opposite electrical field a shear strain is achieved.
Skew bending- A unidirectional electrical field is applied on the actuators couple and a diagonal curvature radius (kxy) is created in the skin, twisting the fin along its axis. Single active layer- this method is a combination of the two previous methods creating a combined strain deformation field created by single piezoelectric layer.
Analytical formulation of wing twist actuation methods was developed based on the classical lamination theory with active layers. In addition a FEM (finite elements method) shells model was built to calculate the deformation of the wing. A parametric investigation was performed including the major key parameters of the airfoil: span, cord, thick and the structural parameters such as material, lamination, and the actuator size, location and orientation.
A lab test prototype was designed and manufactured, and a series of several static and dynamic tests were conducted. The tests demonstrated the design concept and verified the FEM and analytical model.
This research shows the feasibility of an alternative design for an efficient smart fin control surface to be implemented in modern air vehicles design.