PSI - Issue 46

Branko Nečemer et al. / Procedia Structural Integrity 46 (2023) 68 – 73 Branko Ne č emer et al. / Structural Integrity Procedia 00 (2019) 000–000

70

3

The analysed auxetic honeycombs presented in Fig. 1 have the same struts thickness of 1.6 mm and almost the same relative porosity of about 70 %. The difference between the analysed auxetic honeycombs is in Poisson's ratio, defined as the mechanical strain in the x-direction divided by the mechanical strain in the y-direction. In this study, the Poisson’s ratio of the analysed auxetic honeycomb was calculated from the mechanical strain obtained in the elastoplastic computational analysis. The relationship between the Poisson’s ratio versus strain along the loading direction is presented in Fig. 2. It is clear that the lowest (negative) Poisson’s ratio was observed for the chiral structure, while the highest Poisson’s ratio was obtained for the S-shaped auxetic honeycombs.

2. Computational analyses

The computational analyses were performed using ANSYS software, where a multilinear plastic-kinematic model was applied as a material model. The elastic part was described by young’s modulus E = 68,656 MPa and Poisson’s ratio ν = 0.33, while the plastic part was modelled by defining the plastic data pairs (see Table 1) obtained from the cyclic stress-strain curve (Ne č emer et a. (2020)).

Table 1. Plastic data pairs Data pair  pl [  ]

 [MPa]

1. 2. 3. 4. 5. 6. 7.

0

270 280 290 300 310 320 330

0.001 0.002 0.005 0.013 0.030 0.071

Uepdpgeer

S tsatrr-us chtaupreed

Re-entrant structure Chiral structure

S-shaped structure

Double arrow head structure

Leodwg ee r

Fig. 3. Boundary conditions

In the computational analysis, five different auxetic honeycombs were analysed (see Fig.1). The boundary conditions prescribed in the computational model are presented in Fig. 3. In the computational model, the restrained movement in y-direction was applied on the lower edge of the specimen. At the same time, displacement was