Free and random-vibration characteristics of sandwich panels featuring orthogonal accordion cores

Abstract

The 3D orthogonal accordion core, formed by orthogonal combination of two 2D accordion honeycomb structure, exhibits a multi-directional zero Poisson’s ratio effect and exceptional deformation resistance. To effectively analyze the random-vibration characteristics of the sandwich panel with this type of core, a 2D equivalent Reissner–Mindlin model (2D-ERM) is developed using the variational asymptotic method. The precision of the 2D-ERM in free vibration analysis were validated using free modal vibration test of 3D printed specimens. Its precision in random vibration analysis was confirmed through comparison with 3D Finite Element (FE) simulations, including PSD/RMS responses. Modal analysis indicated that the relative error of 2D-ERM in predicting the first six eigenfrequencies remains below 2%, with the modal clouds demonstrating high reliability. Under base acceleration excitation, the displacement-PSD, velocity-PSD, and acceleration-PSD curves, along with RMS values obtained from 2D-ERM agree well with those from 3D-FEM for various boundary conditions, with the maximum error less than 5%. The length-to-thickness ratio of the extending strut significantly influences the equivalent stiffness, while the re-entrant angle and length-to-thickness ratio of the inclined strut exert the greatest impact on the eigenfrequency and displacement-PSD peak. Compared to SP-3D-XYAS, the equivalent density of SP-3D-OAC is reduced by up to 20%, while still achieving a low displacement-PSD peak. This balance, combined with the absence of coupling effects, makes SP-3D-OAC especially well-suited for applications in precision equipment supports and vibration isolation materials.