Free vibration analysis of rotating sandwich panels with carbon nanotubes reinforced face sheets and honeycomb core in thermal environments using finite element method

The present work investigates the free vibration response of rotating sandwich panels comprising nanoparticle-reinforced face sheets and a metallic honeycomb core using the finite element method (FEM). The honeycomb core is either re-entrant or non-re-entrant, while the composite face sheets are made of poly-methyl methacrylate (PMMA) matrix reinforced by carbon nanotubes (CNTs). The deformations of the sandwich panel are modelled using a higher-order shear deformation theory (HSDT), considering seven degrees of freedom at each node. The effective properties of the CNTs reinforced face sheets depend on the working temperature and CNTs grading pattern and are evaluated with the help of the extended rule of mixture (EROM). The titanium alloy-based metallic honeycomb core properties depend on the inclination angle and rib-thickness ratio. The work considers the influence of crucial parameters like inclined angle, rib-thickness ratio, pre-twist angle, panel aspect ratio, core-to-face sheet thickness ratio, rotational speed and hub radius. A decrease in the natural frequency is observed with an increase in the honeycomb angle, while the reverse trend occurs with an increase in the rib-thickness ratio of the honeycomb core. An increase in the rotational speed and hub radius increases the natural frequencies irrespective of the CNTs distribution pattern. Also, the analysis involves plotting the mode shapes at different honeycomb angles. The first mode shape indicates the first bending for higher values of the auxetic angles, while it is the first twist mode at lower values.