Abstract

A finite element method is presented for predicting the flutter response of laminated composite panels subjected to moisture concentration and temperature. The analysis accounts for material properties at elevated temperature and moisture concentration. The analysis is based on the first-order approximation to the linear piston theory and laminated plate theory that includes shear deformation. Both rectangular and skew panels are considered. Stability boundaries at moisture concentrations and temperatures for various lamination schemes and boundary conditions are discussed.

Highlights

  • The external skin panels of modern high speed flight vehicles traveling through the atmosphere at supersonic speed are susceptible to flutter (Bisplinghoff and Ashely, 1962)_ The panel flutter leads to fatigue failure and has become a significant structural design problem

  • The analysis described in the previous section is applicable to the determination of stability boundaries of laminated rectangular and skew panels exposed to moisture and temperature through the volume of the plate

  • For isotropic panels the nondimensional frequency is expressed as n = wa2(PmtID)o.5 and the nondimensional dynamic pressure is defined as A = A(a3ID)

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Summary

INTRODUCTION

The external skin panels of modern high speed flight vehicles traveling through the atmosphere at supersonic speed are susceptible to flutter (Bisplinghoff and Ashely, 1962)_ The panel flutter leads to fatigue failure and has become a significant structural design problem. Yang (1976) studied the effects of temperature rise on stability boundaries using FEM. The flutter response of composite panels was investigated in the past by Rosettos and Tong (1974), Gray and Mei (1993), and Liaw and Yang (1993) with the objective of assessing the influence of fiber orientation and lamination schemes on the critical flutter parameter of thin laminates. Moisture and temperature affect the matrix-dominated stiffness properties of the composite, and have significant effects on the structural behavior of laminated plates (Pipes et ai., 1976; Whitney and Ashton, 1971; Sai Ram and Sinha, 1992). The emphasis in this study is on the investigation of the effect of moisture concentration and temperature on flutter characteristics of laminated thin rectangular and skew panels. The reduced lamina material properties at elevated moisture concentration and temperature were used in the computation of numerical results

GOVERNING EQUATIONS
Air flow
FINITE ELEMENT FORMULATION
ELEMENT INITIAL STRESS STIFFNESS MATRIX
The work done by the aerodynamic forces is given by
IMPOSITION OF SKEW BOUNDARY CONDITIONS
SOLUTION PROCESS
RESULTS AND DISCUSSION
Effect of Moisture and Temperature
No flutter
CONCLUSION
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