Aeroelastic instability continued to be a most important criteria in the design of aerospace structures. &nbsp;This instability induces fast growing self-excited oscillations (flutter) of the structure due to the fluid-structure interaction under supersonic stream flows. &nbsp;Thus, increase in the flight velocity of aircraft results in high-level dynamic stresses, excessive noise, fatigue and fracture of the structure. Hence, the structural material characteristics like light weight, specific stiffness, impact absorption capacity, thermal insulation, vibration, noise and acoustic damping capacity are the most desirable properties. Thus, the aerospace industry necessitates the development of advanced composite materials. From the last few decades, functionally graded (FG) materials acquired the greatest interest among the researchers due to their tailorable properties and eliminated material discontinuity in conventional laminated composites. &nbsp;In the recent times, the porous functionally graded material had been exploited in the aerospace research due to its close match of properties with the aforesaid desirable properties. Thus, it is important to explore the tailorability of porous FG properties in association with the structural dynamic behavior under aerodynamic loadings. The present work is in this direction to study the aerodynamic structural behavior of porous FG curved/ flat panels under supersonic flows.In the literature, a limited number of studies are available on the dynamic characteristics of porous FG structures. All the reported works were based on the one-dimensional porous model where the material porous grading is considered across the thickness. But this model utilization may be limited due to the three-dimensional porosity variation of most of the practical porous materials. Hence, a more practical distribution of porosity is still to be exploited for the desired dynamic behavior of structures. Also, the reported works in the literature are limited to the linear range of dynamics. But the consideration of geometric nonlinearity may be necessary for the structures under supersonic aerodynamic loading. Therefore, in the present work, the nonlinear dynamic characteristics of porous FG flat/ curved panels with one and two-dimensional porosity are explored.This work focuses mainly on the effect of porosity distribution on the critical aerodynamic pressure (CAP) (threshold of instability) and flutter amplitude of the fixed-fixed curved/flat panels. The curved/flat panel is modeled using two dimensional Sander’s nonlinear shell first-order shear deformation theory. Whereas the aerodynamic pressure due to the stream flow over the panel is modelled using first-order piston theory. The CAP is evaluated by deriving the eigen value problem whereas the nonlinear dynamic response is evaluated using Bathe’s time integration method. The results revealed that flat panel has higher CAP compared to the curved panel while it decreases with decrease in radius of curvature. For a fixed volume fraction of total porosity in flat panel, high porosity at the core and low porosity at the midspan induces higher value of CAP as well as higher value of flutter amplitude. For curved panel, the corresponding porosity distributions depends on the deepness of the panel while its corresponding flutter modes varies. The results acquired from this study may be useful for the aeroelastic analysis and flutter design of supersonic structures.

Supersonic Aerodynamic Instability Characteristics of Bidirectional Porous Functionally Graded Panel

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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