Free vibration analysis of composite sandwich panels with hierarchical honeycomb sandwich core

The vibration characteristics of sandwich panels with a hierarchical composite honeycomb sandwich core were investigated in this study. An orthotropic constitutive model of the hierarchical composite honeycomb sandwich core was used to propose an equivalent model (two-dimensional model). Two-dimensional (2D) and the three-dimensional (3D) finite element models as well as modal tests were used to predict the natural frequencies and mode shapes of the sandwich panels. The prediction results obtained using the equivalent model were consistent with the experimental and 3D finite element analysis results. Subsequently, a redesigned sandwich panel, with a hierarchical cross-honeycomb sandwich core, was manufactured to implement the multifunctional characteristics such as fluid flow and installation of microelectronic devices. To compare the vibration characteristics of the panel with a hierarchical cross-honeycomb sandwich core with those of a panel with a hierarchical square-honeycomb sandwich core, a dimensionless frequency parameter, ω₁/ω, was proposed. The frequency parameter had different sensitivities to the geometric parameters, i.e., the face-sheet thickness ratio, wall-sheet thickness ratio, and relative density of the filling foam.