Auxetic and Hybrid Honeycomb Structures for Energy Absorption Applications: Design and In-plane Dynamic Crushing Behaviors

Abstract

Honeycomb structures have been used in various impact energy absorbing applications because of high performance and low density properties. Recent studies have shown that auxetic honeycombs (with negative angle θ) display lateral expansion when stretched and densification when compressed because of their negative Poisson’s ratio (NPR). These structures have been extensively studied due to unique mechanical properties and excellent energy absorption ability that can be implemented in various engineering applications such as aeronautics, biomedical engineering, automobile industry, military affairs etc. In this study we present a new design of auxetic-strut structure and hybrid of auxetic-strut and honeycomb structure for inplane performance improvement. A comparative study of, design and in-plane dynamic crushing behavior of regular honeycomb, re-entrant auxetic, auxetic-strut and two hybrid structures of combining regular honeycomb and auxetic-strut structures was carried out. Finite element modelling is carried out to compare the in-plane dynamic crushing behavior of these structures at different impact velocities. Deformation mechanism of these structures was studied, that gave an insight on how to control the deformation of a structure and tailor the properties. The honeycomb and re-entrant auxetic structures deform and collapse side-ways, and the auxetic-strut structure along with hybrid structures collapse within it-self making them denser as they deform. The amount of energy absorbed by all the structures was found out. The energy absorbed by auxetic- strut and hybrid structures was half when compared with honeycomb and re-entrant auxetic structures at lower strain levels. But at higher strain levels it was twice as that of the later. These results are valuable to provide new fundamental understanding of structure-property relationship for new auxetic-strut and their hybrid honeycomb core structures.