Flutter behavior of quadrilateral auxetic core sandwich plate with bio-inspired three-phase composite facings numerical analysis and experimental verification

Flutter characteristics of auxetic core quadrilateral sandwich plates with three-phase bio-inspired laminated composite facings are presented. The core is made of aluminum, while the facings are made of graphene nanoplatelets dispersed in bio-inspired glass fiber/epoxy laminates. The equations of motion are obtained using Reissner-Mindlin plate theory and Hamilton's approach and then solved with the help of differential quadrature method. Experimental verification of free vibration is done for isotropic and hexagonal honeycomb core sandwich panels. Influences of core parameters (aspect ratio, inclined angle, and thickness-to-width ratio), mass fraction of graphene nanoplatelets and fibers, various graphene nanoplatelet distribution patterns, the geometry and aspect ratio of the plate, and bio-inspired layup scheme of laminated facings on the flutter characteristic are explored. The critical aerodynamic pressure is not sensitive to the core parameters and the dispersion pattern of graphene nanoplatelets. Critical aerodynamic pressure of the panel increases significantly with increase in the mass fractions of fiber and graphene nanoplatelet. Furthermore, the increase in the plate angles results in reduced critical aerodynamic pressure. Facing laminate made of helicoidal type bio-inspired lay-up scheme with lower rotation angle enhances the critical aerodynamic pressure compared to the conventional uni-directional, cross-ply, and quasi-isotropic lay-ups.