Design of a Hybrid Honeycomb Unit Cell with Enhanced In-Plane Mechanical Properties

Abstract

Sandwich structures with honeycomb core are widely used in the lightweight design and impact energy absorption applications in automotive, sporting, and aerospace industries. Recently, the auxetic honeycombs with negative Poisson's ratio attract a substantial attention for different engineering products. In this study, we implement Additive Manufacturing technology, experimental testing, and Finite Element Analysis (FEA) to design and investigate the mechanical behavior of a novel unit cell for sandwich structure core. The new core model contains the conventional and auxetic honeycomb cells beside each other to create a Hybrid Honeycomb (HHC) for the sandwich structure. The different designs of unit cells with the same volume fraction of 15% are 3D-printed using Fused Deposition Modeling technique, and the comparative study on the mechanical behavior of conventional honeycomb, auxetic honeycomb, and HHC structures is conducted. The quasi-static uniaxial compression tests are performed on the printed samples to investigate the mechanical behavior of the printed structures. The deformation and failure modes of the different designs are studied at the cell level utilizing FEA of the compression test and experimental observation. The compressive strength of the different design is measured using three experimental tests. The new HHC unit cell design shows significantly higher mechanical properties than the auxetic and the conventional designs. Modifying the design variables of hybrid cellular core structure allows us to tailor the mechanical properties and deformation pattern in macro level to achieve the desired mechanical properties in sandwich structures.

Re‐entrant auxetic structures fabricated by fused deposition modeling: An experimental study of influence of process parameters under compressive loading

“…In absence of such yield point, stress at 10% is considered as compressive strength of the structure. [39] Compressive stiffness (i.e. modulus of compression) is calculated by the ratio of stress to strain in elastic region.…”

Numerical and experimental investigation of FDM fabricated re-entrant auxetic structures of ABS and PLA materials under compressive loading

“…Compressive strength is stress value at a yield point if yield takes place before 10% strain. In nonappearance of such a yield point, stress at 10% is considered as the compressive strength of the material (Raeisi et al , 2019). Compressive stiffness (Modulus of compression) is the ratio of stress to strain in an elastic region of a material when it is compressed.…”

“…ABS and PLA). The thickness of cell wall of the auxetic structure is calculated for constant relative density by rearranging the terms in equation (1) (Gibson and Ashby, 1999; Raeisi et al , 2019). In a linear elastic regime, apparent Young’s modulus of the meta-material sample is related to relative density as given by equation (2) (Surjadi et al , 2019).…”

“…It was found that ANN models perform best, followed by GP and RSM. Raeisi et al (2019) compared the compressive performance of regular, auxetic and hybrid honeycomb structures. These structures were compared for mechanical properties with the same relative density.…”

Auxetic structures fabricated by material extrusion: an experimental investigation of gradient parameters

“…Relative density is an important factor for cellular solid. It is calculated using equation (2) (Gibson and Ashby, 1999; Raeisi et al , 2019). where ρ*= density of auxetic structure,…”