Hexagonal Honeycombs with Zero Poisson's Ratios and Enhanced Stiffness

Abstract

In view of their potential applications in sandwich structures, there has been increasing interest in honeycomb networks. Several different types of honeycomb systems have been proposed each exhibiting different mechanical properties. Here we propose a new hexagonal honeycomb structure composed of two different geometrical features: a re‐entrant feature which is known to generate auxetic behavior, and a non re‐entrant feature found in regular hexagonal honeycombs which leads to conventional behavior. This results in a “semi re‐entrant honeycomb” built of alternate conventional and auxetic layers. Finite element analysis and analytical modeling of these honeycombs show that they exhibit a zero Poisson ratio in one direction and a higher than normal Young's modulus in the orthogonal direction. We also show that by virtue of its zero Poisson's ratio, this honeycomb has a natural tendency to form cylindrical shaped curvatures, something which is very difficult to achieve with conventional or auxetic honeycombs.

Transverse shear modulus of SILICOMB cellular structures

“…Cellular materials with zero Poisson's ratio have also been proposed for one-dimensional spanwise morphing of wings and blades [11,12], as well as scaffolds for biomedical applications [13]. The zero m characteristics also offers the possibility to manufacture tubular structures with absence of sinclastic or anticlastic behaviour [14]. The presence of a zero m has been observed in cork [1], liquid crystalline polymers [15], but also in cellular structures such as the accordion honeycombs [12].…”

Mechanical properties in tensile loading of H13 re-entrant honeycomb auxetic structure manufactured by direct metal deposition

“…1(b). These points are at the centre of the respective unit cell in the structure as it has been suggested that the centre points on the unit cell should be selected to avoid edge effects during FEA for the measurement of Poisson's ratio [12]. Similar method has been used for estimating the Poisson's ratio during FEA of the auxetic structure [13].…”

AUXHEX – A Kirigami inspired zero Poisson’s ratio cellular structure

“…. Zero Poisson ratio (ZPR) cellular structures have no synclastic or anticlastic behavior, as Grima and co-authors show in their work [25]. With such ZPR core panels it would be possible to follow axial curvatures and build lightweight, cylindrical structures.…”