EFFECTS OF SHOCK LOCATION ON AEROTHERMOELASTIC STABILITY OF VISCOELASTIC PANEL

In recent years, new composite materials have been widely used in the structural design of supersonic vehicle panels, and these new materials generally have viscoelastic properties. Focusing on the aeroelastic stability of a heated viscoelastic panel in shock-dominated flows with an arbitrary shock impingement location condition, a systematic theoretical analysis model is established. According to the Kelvin-Voigt type viscoelastic damping model and von Kármán large deflection theory, the aerothermoelastic equations are established with thermal effect based on quasi-steady thermal stress theory. Local first-order piston theory is employed in the region before and after shock waves. The Lyapunov indirect method is employed to analyze the stability of the nonlinear aeroelastic system, and then aeroelastic stability boundaries can be obtained by using Routh-Hurwitz criterion. Based on the theoretical analysis model, the effects of shock location on the aerothermoelastic stability of the viscoelastic panel are studied. To verify the correctness of theoretical results, nonlinear flutter equations are solved by the fourth-order Runge-Kutta numerical integration method to obtain the time history of panel response. The results show that the shock impingement location has a significant effect on the aerothermoelastic stability of the viscoelastic panel. As the shock wave impact point moves from one endpoint of the panel to another endpoint, the critical flutter dynamic pressure of the viscoelastic panel exhibits nonlinear and nonmonotonic variations. With the moving of the shock wave in the direction of flow, the critical flutter dynamic pressure of the viscoelastic panel exhibits different variations when the oblique shock wave impacts at different locations on the panel. Specifically, near the endpoint of the panel in the upstream region, the critical flutter dynamic pressure continuously decreases; in the mid-area of the panel, the critical flutter dynamic pressure increases monotonically and significantly; near the endpoint of the panel in the downstream region, the critical flutter dynamic pressure fluctuates, and the fluctuation increases with the increase of shock wave strength. The most dangerous position for an oblique shock wave impinging on the viscoelastic panel is approximately at the location x_i/l = 0.17 , which will move upstream of the panel as the viscoelastic damping and the strength of the shock wave increase.