Sharif Digital Repository

In this paper, the nonlinear aeroelastic behavior of functionally graded plates is studied in supersonic flow. For this purpose, the von Karman strains and piston theory have been employed to model structural nonlinearity and quasi-steady aerodynamic panel loading, respectively. The material properties of the plate are assumed to be graded continuously in the direction of thickness. The variation of the properties follows a simple power-law distribution in terms of the volume fractions of constituents. The Hamilton's principle is used to construct the coupled nonlinear partial differential equations of motion. The derived equations are transformed into a set of coupled ordinary differential... 

The aeroelastic stability of an aircraft wing modeled as an anisotropic composite thin-walled beam in an incompressible flow is investigated. The wing is built-up as a single-cell box beam whose central point is noncoincident with the mid-chord of the profile. The effects of material anisotropy, transverse shear, warping inhibition, nonuniform torsional model and rotary inertia are considered in the structural model. The unsteady incompressible aerodynamics based on Wagner's function is used to determine the aerodynamic loads. The effects of the offset between reference axis and the mid-chord ("a" parameter), fiber orientation and sweep angle on stability boundary are considered, their... 

This article investigates the free vibration of the rotating, tapered, thin-walled, composite box beam. The structural model incorporates a number of non-classical effects, such as transverse shear, warping inhibition, non-uniformtorsional model, and rotary inertia.The results obtained in this article seek to clarify the effect of flap-twist coupling, taper ratio, slenderness ratio, angular velocity, fibre orientation, and hub ratio on natural frequencies and mode shapes of the rotating thin-walled composite beams. The results are expected to offer better predictions of the vibrational behaviour of these kinds of structures in general, and in the design of rotor blades of turbo machinery, in... 

An analytical procedure for aeroservoplastic stability analysis of guided supersonic flight vehicles is developed by using slender body aerodynamic theory and modal analysis techniques. The roll channel is decoupled from pitch and yaw channels by using the linearized system of equations. Results show that divergence is the only aeroelastic instability that can occur for the nonrolling flight vehicle with no-control loop and is accurately computed using the first bending mode shape. The result of the divergence analysis demonstrates that the vehicle elasticity has a destabilizing effect on the pitch and yaw channels. The inclusion of aeroservoelasticity in the analysis can cause dynamic... 

This paper presents a novel approach for the analysis of a fourth-order parabolic equation dealing with vibration of beams by using the decomposition method. In this regard, a general approach based on the generalized Fourier series expansion is applied. The obtained analytic solution is simplified in terms of a given set of orthogonal basis functions. The result is compared with the classical modal analysis technique which is widely used in the field of structural dynamics. It is shown that the result of the decomposition method leads to an exact closed-form solution which is equivalent to the result obtained by the modal analysis method. Some examples are given to demonstrate the validity... 

The aeroelastic design of composite wings modeled as thin-walled beams is investigated through the use of curvilinear fiber. The structural model considers non-classical effects such as transverse shear, warping restraint, rotary inertia, nonuniform torsional model and also aerodynamic loads based on Wagner's function. In this paper, a linear spanwise variation of the fiber orientation resulting in a variable-stiffness structure is used to optimize the wing for maximum aeroelastic instability speed purpose, while manufacturing constraints are incorporated. Numerical results indicate improvements of aeroelastic stability of variable-stiffness wings over conventional, constant-stiffness ones