Foam structures with a negative poisson's ratio
27 Feb 1987-Science (American Association for the Advancement of Science)-Vol. 235, Iss: 4792, pp 1038-1040
TL;DR: A novel foam structure is presented, which exhibits a negative Poisson's ratio, and such a material expands laterally when stretched, in contrast to ordinary materials.
Abstract: A novel foam structure is presented, which exhibits a negative Poisson's ratio. Such a material expands laterally when stretched, in contrast to ordinary materials.
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TL;DR: The scalable self-assembly of randomly oriented graphene sheets into additive-free, essentially homogenous graphene sponge materials that provide a combination of both cork-like and rubber-like properties and display Poisson's ratios in all directions that are near-zero.
Abstract: The incorporation of the desirable properties of graphene into three-dimensional materials remains challenging. Here, the authors report the scalable self-assembly of graphene sheets into spongy materials with very low densities, and near-zero and largely strain-independent Poisson's ratios in all directions.
484 citations
TL;DR: In this paper, the authors summarized research work related to materials with zero, or negative Poisson's ratio, referred to as auxetic materials, and predicted that future research will be in the direction of disordered microstructures utilizing the homogenization method.
483 citations
TL;DR: The models presented provide not only quantitative information about the mechanical properties of SLGS, but also insight into the equivalent mechanical deformation mechanisms when the SLGS undergoes small strain uniaxial and pure shear loading.
Abstract: The elastic moduli of single layer graphene sheet (SLGS) have been a subject of intensive research in recent years. Calculations of these effective properties range from molecular dynamic simulations to use of structural mechanical models. On the basis of mathematical models and calculation methods, several different results have been obtained and these are available in the literature. Existing mechanical models employ Euler-Bernoulli beams rigidly jointed to the lattice atoms. In this paper we propose truss-type analytical models and an approach based on cellular material mechanics theory to describe the in-plane linear elastic properties of the single layer graphene sheets. In the cellular material model, the C-C bonds are represented by equivalent mechanical beams having full stretching, hinging, bending and deep shear beam deformation mechanisms. Closed form expressions for Young's modulus, the shear modulus and Poisson's ratio for the graphene sheets are derived in terms of the equivalent mechanical C-C bond properties. The models presented provide not only quantitative information about the mechanical properties of SLGS, but also insight into the equivalent mechanical deformation mechanisms when the SLGS undergoes small strain uniaxial and pure shear loading. The analytical and numerical results from finite element simulations show good agreement with existing numerical values in the open literature. A peculiar marked auxetic behaviour for the C-C bonds is identified for single graphene sheets under pure shear loading.
481 citations
TL;DR: In this article, the problem of finding the simplest possible microstructure with the prescribed elastic properties was formulated as an inverse homogenization problem, and was solved by an optimality criteria method.
467 citations
TL;DR: In this article, the authors describe some of the consequences of negative Poisson's ratio and some routes for making polymers with this property and potential applications for these materials are reviewed.
464 citations
References
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TL;DR: The mechanical properties (elastic, plastic, creep, and fracture) of cellular solids or foams are related to the properties of the cell wall material and to the cell geometry.
Abstract: The mechanical properties (elastic, plastic, creep, and fracture) of cellular solids or foams are related to the properties of the cell wall material and to the cell geometry The properties are well described by simple formulae Such materials occur widely in nature and have many potential engineering applications
909 citations
TL;DR: In these studies, encystation of Giardia lamblia in vitro was demonstrated by morphologic, immunologic, and biochemical criteria and will aid in understanding the differentiation of an important protozoan pathogen.
Abstract: The cyst form of Giardia lamblia is responsible for transmission of giardiasis, a common waterborne intestinal disease. In these studies, encystation of Giardia lamblia in vitro was demonstrated by morphologic, immunologic, and biochemical criteria. In the suckling mouse model, the jejunum was shown to be a major site of encystation of the parasite. Small intestinal factors were therefore tested as stimuli of encystation. An antiserum that reacted with cysts, but not with cultured trophozoites was raised in rabbits and used as a sensitive probe for differentiation in vitro. Cultured trophozoites that were exposed to bile salts showed a more than 20-fold increase in the number of oval, refractile cells that reacted strongly with anticyst antibodies, and in the expression of major cyst antigens. Exposure to primary bile salts resulted in higher levels of encystation than exposure to secondary bile salts. These studies will aid in understanding the differentiation of an important protozoan pathogen.
157 citations
TL;DR: In this paper, a method of calculating the anisotropy of Poisson's ratio is applied to trigonal and tetragonal crystals in the literature, and the method of calculation is extended to hexagonal crystals.
Abstract: A method of calculating the anisotropy of Poisson's ratio is applied to trigonal and tetragonal crystals in the literature. The method of calculation is extended to hexagonal crystals. The results are illustrated by reference to Tl and Cd.
96 citations