Damping analysis of stiffened laminated composite plates in thermal environment

High-strength and lightweight composites used in high-speed vehicles and aircraft experience increased temperature owing to aerodynamic friction. Because of the rise in temperature, the elastic moduli of the composites are degraded and inherent viscous damping is increased to the glass transition temperature. In this work, the damping performance of unstiffened and stiffened polyetheretherketone (PEEK) based intermediate modulus (IM7) carbon fiber laminated composite plates is evaluated at various temperatures using displacement-and energy-based approaches. In the displacement-based approach, the logarithmic decrement of the damped vibration is determined to investigate the effect of lamina sequences, stiffener orientation, and stiffener depth at different temperatures. A first-order shear deformation theory considering the viscoelastic property of the composite lamina is implemented to simulate the damped dynamic response of the laminated composite plates in a thermal environment. The best suitable damping model, among Rayleigh damping and modal expansion damping, has been identified to evaluate the damping matrix. Furthermore, the energy-based damping analysis appeared to be a robust approach to evaluate the damping performance as compared to the displacement-based analysis. It is concluded that stiffened plates effectively suppress the dynamic response at elevated temperature, whereas the unstiffened plates show relatively better damping performance at lower temperature.