Bandgap capability of hybrid kirigami inspired cellular structures

Periodic cellular core structures included in sandwich panels have been a crucial milestone in the Aerospace segment and has become a standard engineered material used in Automotive and Marine industries. Such structures possess good stiffness while saving weight and only lately their potential to act as passive vibration filters is increasingly being studied. By varying the core in-plane cellular topology, different bandgaps are produced. Parametric analyses of homogeneous honeycombs show how there is a shift and/or variation in range of the bandgaps as we vary a certain geometrical feature. A previous work attempted to produce, successfully, a hybrid cellular structure possessing zero in-plane Poisson's coefficient. Hybrid being a cellular core containing cells of different shapes. This was achieved using PEEK thermoplastic thin sheets and the Japanese art technique of cutting and folding paper, known as Kirigami. Whilst the static properties have already been investigated, the vibration filtering properties of hybrid patterns like the AUXHEX have not yet been covered. In this work, numerical simulations are carried out with the aim of investigating the vibration filtering properties of such structures using two different approaches. The first technique used is the Harmonic analysis with commercially available software, and the other one, which has been proved to be computationally more efficient, consists in the Wave Finite Element Method (WFEM) which still makes use of FEM packages, but instead of working with large models, it exploits the periodicity of the structure by analysing only the unit cell, thanks to the Floquet-Bloch theorem. Both techniques allow to produce graphs such as FRF plots and Dispersion Curves, which are a powerful tools used to identify the spectral bandgap signature of the structure considered.