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The contact problem between two bodies: plate and semi-cylindrical bar is studied in this paper. The analysis concerns the contact pressure distribution along the contact region, as well as the deflection of the plate. Furthermore, the case of a composite plate covered with the auxetic layer is also considered. The influence of the Poisson's ratio of the layer on the behavior of the plate is studied. The contact pressure distribution along the contact area is analyzed using finite element analysis. [ABSTRACT FROM AUTHOR]

We propose in this paper analytical and numerical models that describe the in-plane uniaxial elastic properties (Young's moduli and Poisson's ratios) of a honeycomb structure with curved walls. We perform a parametric analysis of the mechanical performance of this honeycomb also by taking into account the different types of deformations acting inside the cell walls. The curved wall honeycomb possesses higher magnitudes of the Poisson's ratio ν12 in the auxetic configuration compared to classical center symmetric configuration with straight cell wall. The presence of the curvature also allows creating configurations with positive Poisson's ratio even for negative internal cell angles, and makes this honeycomb design attractive for mechanical tailoring. [ABSTRACT FROM AUTHOR]

An extensive investigation is carried out on the missing rib square grid structure using finite element simulations. This showed that, in the cases considered in this study, the type of deformation is primarily dependent on the ratio of the thickness of different ribs with the structure behaving like an anti-tetrachiral at particular ratios. The analysis also showed that the ability of the structure to deform predominantly through the bending of the ligament allows it to achieve much more negative values of the Poisson's ratio than previously reported. Confirmation of the numerical results is obtained through experimental methods involving the 3D printing of representative structures which are subsequently subjected to compression. [ABSTRACT FROM AUTHOR]

Auxetic cellular materials show great potential for improved properties in case of impact loading. Due to this potential, auxetic structures made from inverted tetrapods are extensively analyzed experimentally and computationally. The built samples are compressed in two orthogonal directions to determine their base mechanical properties and deformation mechanisms. The lattice computational model is developed and validated using the experimental results. A new shape optimization procedure to develop new auxetic structures with functionally graded geometry is proposed and tested in a case study. With introduction of the functionally graded geometry the response of the auxetic structure can be tailored to a particular loading condition, which is especially important in impact or ballistic performance of modern composite materials. [ABSTRACT FROM AUTHOR]

Microstructured plates, consisting of various conventional and re-entrant cells, are numerically constructed and analyzed for their effective elastic properties under in-plane deformation. The finite element numerical method is adopted. The calculated effective Poisson's ratios of the plates are found to be in the range between −1 and 1, in consistency with the theory of two-dimensional elasticity. Auxetic angles need to be greater than about 20° in order to obtain negative Poisson's ratio. Increasing the auxetic angles reduces the effective pure shear modulus. Elastically anisotropic characteristics of the homogenized plate are analyzed with the calculated effective Young's modulus, Poisson's ratio, and pure shear modulus. [ABSTRACT FROM AUTHOR]

There exist several honeycomb networks exhibiting zero Poisson's ratio (ZPR). Applications of these networks can be found in different fields. The ZPR properties of these structures have been mechanically modeled and tested. However, the underlying mechanism driving the ZPR behavior has not been paid much attention. The present work focuses on the deformation mechanism of the ZPR networks. Through the discussion and comparison of the deformation process of the ZPR, auxetic and common honeycomb networks, the strain-isolation mechanism is proposed to explain the ZPR behavior. Then, according to this mechanism, the reversed semi-re-entrant (RSRE) honeycomb is created. With experimental measurements and finite-element analysis (FEA), the ZPR properties of the RSRE can be proven. The strain-isolation mechanism can not only explain the ZPR behavior but also be used in the design of new ZPR honeycomb networks. 3D ZPR structures are also derived from the 2D honeycomb networks. Their Poisson's ratios in 3D space are also discussed based on FEA results. The model of the 3D RSRE structure showing ZPR behaviors in three orthogonal planes. [ABSTRACT FROM AUTHOR]