Hierarchical modeling and optimization of camber morphing airfoil

A variable camber morphing airfoil with compliant ribs and flexible composite skins is studied in a hierarchical modeling framework. The key requirements of a variable camber morphing airfoil are the flexible skin, compliant internal structure and a lightweightactuation system. A biologically inspired, internal structure is adapted to produce continuous camber morphing. The conflicting requirements of the morphing skin, namely low in-plane stiffness and high out-of-plane bending stiffness, are metby designing the composite with curvilinear fiber paths. A coupled aeroelastic simulation and optimization of the proposed 2-D morphing airfoil is computationally complex. Hierarchical computational models of the morphing airfoil are used to decouple the complaint ribs and airfoil skin. In the first level of hierarchy, a fluid-structure interaction is performed with the homogenizedbeam model of the compliant rib structure and 2-D panel method. In the second level, a finite element model of the camber morphing skin is developed with representative boundary conditions. A multi-objective optimization framework is developed to find the optimal curvilinear fiber paths of the morphing skin to meet the airfoil geometric shape and actuation requirements of the first level. The optimal results show that a significant camber variation and significant changes in aerodynamic properties can be achieved with the compliant skin and airfoil structure considered in this study. The hierarchical modeling framework of the camber morphing airfoil discussed in this paper enhances theoretical understanding of each sub-system and reduces the computational costs.