Aeroelastic Flutter Optimization Through Fiber Orientation
Guilherme Roldo1; Carlos Eduardo de Souza2; Jun Sérgio Ono Fonseca1
1 Applied Mechanics Group, Federal University of Rio Grande do Sul; 2 Mechanical Engineering Department, Federal University of Santa Maria
doi:10.20906/CPS/COB-2015-1937
Resumo
This papers discusses an aeroelastic tailoring methodology that aims the increase of flutter onset speed of flat plates using the ply orientation as design variable. The search for a very light aircraft design and the design of small unmanned aerial vehicles (UAVs) lead to the use of laminate composite material and only a few layers of material. Each ply is usually a commercial uni-directional tape or bi-directional plain weave fabric with specified thickness. Many times, the designer is left then with the choice of each ply orientation definition for aeroelastic requirements, such as flutter speed increase. The flutter solution is obtained here from a stability analysis of the aeroelastic equation of motion in its generalized form, through ZONA6 panel method for subsonic flow from commercial software ZAERO. The structural normal modes and frequencies are obtained via finite element method using an 8-node degenerated shell element code. The flutter onset speed is maximized by unconstrained sequential linear programming with fiber orientation as design variables. The sensitivity to the fiber orientation at each ply is approximated by forward finite difference. Flat plates with one and two ply orientations are studied in this work. The proposed procedure was able to increase flutter speed up to a factor of three, though, for some cases, the optimized stacking sequence found provides less than the possibly achievable flutter speed when the algorithm encounters a local maximum. A few number of optimization runs with starting orientations set at random could help finding the global maximum.
Palavras-chave: Aeroelastic tailoring; Flutter prevention; Laminated composite materials; Optimization