Showing papers by "Jack R. Vinson published in 2003"

On the design of piezoelectric smart fins for flight vehicles

Abstract: A systematic approach for the design of active piezoelectric fins developed for a small-scale flight vehicle is presented. The proposed design approach uses analytical and computational tools that are based on the high-order theory and provides a graphical representation of the response spectrum of the active fin. In addition, it enables the coupling of the structural and aerodynamic analyses and provides a frame in which the results of the two types of analysis are adjoined. A numerical design study of a twist-actuated smart fin is presented and discussed. The results reveal the sensitivity of the structure to a broad range of geometrical, mechanical, and electromechanical design variables and provide guidelines for the optimization of the active structure. A set of normalized design master curves that can be scaled to fit various geometrical layouts of the structure investigated are also presented and discussed.

Smart Fins: Analytical Modeling and Basic Design Concepts

Abstract: The objective of this paper is to examine the feasibility of using monolithic, directed, or fibrous piezoelectric smart materials to control the shape of a subsonic projectile fin during flight. To achieve this goal, an analytical model for composite laminated plates of general layup with either isotropic or anisotropic active layers is derived. The mathematical formulation uses the variational principle of virtual work along with the classical plate and lamination theories and the anisotropic piezoelectric constitutive equations. A solution procedure that adopts the concepts of the extended Kantorovich method and imposes them on the variational ("weak") form of the active plate problem is derived. The results of the proposed model are compared with those of other classical approximated solutions, as well as results of finite element analysis. Finally, the derived model is used for the quantitative examination of four basic design concepts for twist actuation and shape control of the investigated fin. The...

High-Order Analysis of Unidirectional Sandwich Panels with Piezolaminated Face Sheets and Soft Core

Abstract: The bending behavior of unidirectional sandwich panels (wide or narrow beams) with a compressible soft core and piezoelectric active face sheets is investigated. The panels studied consist of composite face sheets with embedded active piezoelectric layers and a compressible core. The mathematical formulation adopts the principles of the high-order sandwich panel theory. The field equations and the boundary and continuity conditions are derived through the variational principle of virtual work, and the electromechanical effect is introduced using the linear piezoelectric constitutive equations. Higher-order effects due to flexibility of the core are incorporated in the analysis as a result of the solution of the field equations and are not presumed a priori. Numerical results are presented for typical cases of active sandwich panels and the effectiveness of various electrical actuation schemes is investigated. The effects associated with using piecewise continuous active layers are also investigated and discussed. The results reveal the capabilities of the proposed model and highlight some of the problems involved with the analysis and design of active sandwich panels.

Theory for Midplane Asymmetric Sandwich Cylindrical Shells

Abstract: In shells, bending stresses in addition to the membrane stresses exist near each structural discontinuity (such as at edge supports, rings, stringers, holes, etc.) and each load discontinuity. This region is the “bending boundary layer”. In sandwich shells, mid-plane asymmetry can be employed to minimize these bending stresses. Governing equations for mid-plane asymmetric sandwich cylindrical shell subjected to axially symmetric loads are derived herein and solved. The solution involves a mid-plane asymmetry factor ϕ, defined herein such that for any asymmetric sandwich construction, -1 < ϕ < 1. Therefore, perturbation solutions are easily obtained using the solutions for the midplane symmetric cylindrical shell.

Asymptotic analysis for the curved/straight sandwich panel junctions

Abstract: Cylindrical bending of a sandwich panel assembly consisting of straight and curved sections is considered. The sandwich assembly is statically determinate, loaded by a uniform pressure and possibly by forces and moments at its edges. The influence of the change of geometry upon the stresses and displacements at the transition zone between the different panel sections is investigated. An exact asymptotic mathematical model based on a number of small parameters is derived. The model assumes the faces of the sandwich panels to be thin elastic beams obeying the Kirchhoff-Love assumptions, while the isotropic core is treated as a 2-D elastic medium. An asymptotic expansion technique is exploited to derive analytical estimate formulae for calculating the deformation and stress distribution characteristics at the critical sections of the assembly. A numerical example illustrates the applicability of the derived formulae, and the validity of the proposed approach is demonstrated through comparison with FEM calcul...