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AbstractAuxetics have emerged recently as an exciting class of mechanical metamaterials that are identified by negative Poisson’s ratio. The mechanical properties of rationally designed auxetic metamaterials are mostly influenced by their topological characteristics rather than the material properties of their constituent material. The goal of this paper is to use optimization algorithms to achieve the desired target mechanical properties for reentrant auxetic metamaterials. The GEKKO optimization package in Python is used for optimizing the geometry of auxetic lattice structures. Several mechanical properties including Poisson’s ratio, relative Young’s modulus, relative yield stress, and relative energy absorption capability, as well as the noted properties normalized with respect to relative density and relative Young’s modulus are chosen for being minimized or maximized. ANSYS finite element package is also implemented for validation of the results obtained from the optimization algorithm. According to the results, to achieve the maximum magnitude of Poisson’s ratio (positive and negative), the size of the unit cell in the lateral direction must be selected to be maximum and the thickness must become minimum. Moreover, to achieve the maximum value of the relative Young’s modulus or energy absorption in any direction, the size of the unit cell in that direction must be maximized. Also, to achieve the maximum amount of relative yield stress in both directions, the unit cell must have a maximum thickness and an internal angle close to zero. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents an analysis of a sandwich structure featuring an auxetic core, manufactured through Vacuum Assisted Resin Transfer Molding (VARTM) using carbon-aramid hybrid fibers. The core was 3D printed with polylactic acid (PLA). Experimental testing of the structure provided results for validating a cost-effective numerical model. The response surface methodology identified results for different sandwich panel configurations, revealing that auxetic behavior depends on the core’s adopted configuration. Increasing the fiber-core contact area induces auxetic behaviors. The structure underwent optimization using the Lichtenberg algorithm, yielding models with 40.32% higher failure load, 36.36% higher natural frequency, and over 20% mass reduction. [ABSTRACT FROM AUTHOR]

The paper "Buckling of stretched strips" [1] , published in the year 2000, seemed to deal with a rather specific problem of buckling of thin structures. Nevertheless, it aroused quite broad interest and prompted a considerable series of further treatments. Deeper theoretical considerations and advanced applications have been published. Various specific aspects of this type of problem have been addressed in these papers. However, a general and systematic consideration of how and to what extent the Poisson's ratio affects the critical stretch of strips of different length to width ratios, L / B , was lacking. Accomplishing this task is the focus of this paper. Given the increasing use of auxetics, strips made from such materials are also being investigated. In addition, the occurrence of previously undiscovered mode transitions is shown. All results are presented in dimensionless form, which allows for fairly general usage. • Influence of Poisson ratio on buckling of stretched strips quantified and discussed. • So far unknown mode transition detected and explained. • Buckling of stretched strips made of auxetic materials – diagrams for buckling factor in dependence of Poisson ratio. [ABSTRACT FROM AUTHOR]