The high-precision 18-degree-of-freedom triangular plate-bending finite element is used to study the effects of composite filament angle, orthotropic modulus ratio, sweep angle, and aspect ratio on the vibration and flutter/divergence characteristics of cantilever plates in subsonic flow. The element stiffness and mass matrices are generated according to the classical lamination theory. Unsteady airload acting on the plate is evaluated by the use of lifting surface theory, which is solved numerically by the doublet-lattice method. To facilitate flutter analysis, interpolation using a surface spline is employed to interconnect the structural nodal and aerodynamic control points. The flutter/divergence tradeoff of aeroelastic tailoring is found, in a more involved manner, for the present plate-like low-aspect-ratio wings as compared to that associated with the beam model first discovered by Weisshaar. Effective enhancement on flutter/divergence performance can be attained by varying the orthotropic modulus ratio while as appropriate fiber orientation is selected. Also, as discovered previously, the present numerical results confirm that the structural tailoring can provide a harmonious balance to the sweep angle effect upon the aeroelastic stability characteristics of a wing. From the numerical examinations performed, it is concluded that substantial improvement upon flutter/divergence characteristics can be achieved by using composite materials. Nevertheless, the benefit can be gained only through a thorough parametric investigation because the aeroelastic stabilities are also complicated by the directional stiffness of composites, in particular for the cases of low-aspect-ratio wings.

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In this paper, a high accuracy linear positioning system with a linear force actuator and magnetic levitation is proposed. By locating a permanently magnetized rod inside a current-carrying.solenoid, the axial force is achieved by the boundary effect of magnet poles and utilized to power the linear motion, while