A novel negative Poisson's ratio (NPR) foam‐filled corrugated tube, made up of a corrugated tube and NPR isotropic foam core, is established by the finite element method. The 3D NPR isotropic foam ...core is achieved by using the triaxial compression method on a cubic Voronoi model, which is created based on the Voronoi tessellation technique. The triaxial compression ratio is defined as η. The Poisson's ratio of Voronoi foam decreases sharply and then increases gradually with an increasing η. A minimum Poisson's ratio, −0.076, is obtained when η = 0.2. Moreover, the Voronoi foam‐filled corrugated tube with minimum Poisson's ratio foam core exhibits the highest energy absorption capacity, which is 10.8% higher than that of the Voronoi foam‐filled corrugated tubes with uncompressed foam core.
A novel negative Poisson's ratio (NPR) foam‐filled corrugated tube, made up of a corrugated tube and NPR isotropic foam core, is established by the finite element method. The 3D NPR isotropic foam core is achieved by using the triaxial compression method on a cubic Voronoi model, which is created based on the Voronoi tessellation technique.
We utilized molecular statics (MS) simulations to investigate the auxeticity of single layer black phosphorus (SLBP). Our simulation results show that the SLBP has a negative in‐plane Poisson's ratio ...in the zigzag direction when the applied strain along the armchair direction exceeds 0.018. We show that the interplay between bond stretching and bond rotating modes determines the in‐plane Poisson's ratio behavior. While the bond stretching mode always tends to increase the in‐plane auxeticity, the bond rotating mode might increase or decrease the in‐plane auxeticity. Furthermore, we show that graphite also exhibits an in‐plane negative Poisson's ratio at finite strains due to a similar mechanism.
The Poisson's ratios of single layer black phosphorous are investigated using atomistic simulations. A negative Poisson's ratio is observed in the zigzag direction as the material is stretched in the armchair direction. The underlying mechanism for the negative Poisson's ratio behavior, which is the interplay between the bond stretching and bond rotating modes, is presented.
Abstract
In this work, continuous fiber reinforced thermoplastic negative Poisson's ratio structures (CFNPRSs) with rotating squares are fabricated by 3D printing based on a symmetrical orthogonal ...and one‐stoke path planning method. The influences of the printing path on the Poisson's ratio, elastic modulus and energy absorption of the structures under compression are systematically researched. The distribution of continuous fiber at the hinge has a great influence on the compression behavior of the structures. As the number of cross laps of continuous fibers at the hinge increases, the negative Poisson's ratio effect decreases while the elastic modulus and energy absorption increase. The printed CFNPRSs with no cross lap have the most obvious negative Poisson's ratio effect, with an average Poisson's ratio of −0.61. A comparative study on Poisson's ratio of the 3D printed polylactic acid negative Poisson's ratio structures (PANPRSs) is carried out, and the results show that the PANPRSs cannot achieve the negative Poisson's ratio effect because the insufficient stiffness of the printed rotation units violates the rigid assumption in theoretical model. Furthermore, the printed CFNPRSs with a lower relative density of 0.18 has an even better negative Poisson's ratio effect than the existing fiber‐reinforced auxetic structures fabricated by 3D printing. This work can provide a significant reference for the preparation of lightweight functional structures using 3D printing.
Highlights
The CFNPRSs with rotating squares are prepared by 3D printing technique.
The path planning of the fiber at the hinge affects the properties of CFNPRSs.
The negative Poisson's ratio of CFNPRSs is more obvious than that of PANPRSs.
The relative density and Poisson's ratio of CFNPRSs have obvious advantages.
•The channel shear connectors are usually stiffer than the angle shear connectors in resisting the slip of concrete slab by about 30% within the elastic range.•Increasing the reinforcement ratio of ...the concrete slab from 0.18% to 0.46% increases the flexural strength of the composite beams by 7.45% and the deflection values were dropped by 23%.•Using upper steel reinforcement mesh prevented any longitudinal cracks at the top surface of the concrete slab and allowed for full plastification of the steel cross-sections.•Poisson’s ratio of the concrete slab was found constant throughout the test with a value of 0.16 and dramatically increases before failure occurs.
An experimental program is carried out to examine the effects of different factors on the slip and stress distribution of concrete slabs in composite beams. A total of ten steel–concrete composite beams with a span of 4.80 m are tested to find the effects of the type of shear connectors and the concrete slab reinforcement on the behaviour of composite beams. All beams consist of monosymmetric steel cross-sections connected to 120 cm wide concrete slabs. Welded shear connectors (angles or channels) spaced at 20 cm are used to connect the concrete slabs to the steel beams. The concrete slabs of eight beams are provided with a lower steel reinforcement only while two beams are provided with both lower and upper steel reinforcement. The results showed that the ultimate load capacity of composite beam with channel connectors is 14% higher than the counterpart beam with angle connectors and 30% stiffer in resisting the slip of the concrete slab. Moreover, composite beams with channel connectors tend to maintain strain compatibility at the interface between concrete slab and steel section better than the counterpart beams with angle connectors. It is also found that using upper steel reinforcement mesh enhances the stress distribution in the concrete slab until failure. It is found that increasing the reinforcement ratio of the concrete slab from 0.18% to 0.46% increases the flexural strength of the composite beams by 7.45%, while decreases the deflection values by 23%. Moreover, using upper steel reinforcement prevented the longitudinal cracking of the top surface of the concrete slab and allowed for full plastification of the steel cross-sections.
Metamaterials are specifically designed materials that possess unique properties that cannot be found in naturally occurring substances. These remarkable materials have the capability to bring about ...a significant transformation across a wide range of industries. Auxetic structures are a recent area of research possess a distinctive characteristic known as a negative Poisson's ratio. Unlike conventional materials that contract when stretched, auxetic structures actually expand in two dimensions. In this study, a new auxetic structure was introduced, and thermoplastic polyurethane samples were 3D printed using a fused filament fabrication method. The samples are then subjected to strains ranging from 5% to 50% and Poisson's ratios are measured both experimentally and numerically using finite element method in Ansys software. By comparing the results of the experimental research and simulation, it is evident that applying strains within this range causes the Poisson's ratio of the samples to change from −0.81 to −0.14 and it showed that the newly introduced structure is auxetic. According to the analysis of root mean square error, the hexagonal mesh with a size of 0.7 mm consistently produced the most accurate results, aligning closely with the experimental sample. Given that this is an entirely novel auxetic structure within the category of arrow‐head auxetic structures, there is potential for future research to be conducted in order to further develop and enhance this model.
This paper presents some results of a study on bituminous mixtures produced with high content of Reclaimed Asphalt Pavement (RAP), which is recycled several times. It deals with the linear ...viscoelastic (LVE) behaviour of the mixtures. This research is included in a project called IMPROVMURE, founded by the French National Research Agency (ANR). This article concerns six bituminous mixtures made in the laboratory. Among the six tested mixtures, three were hot bituminous mixtures and three were produced according to a warm process with foamed bitumen. For each one of the two processes, the reference mixture contains no RAP. The second mixture contains 70% RAP coming from the milling process. The third mixture was made with 70% of the second mixtures, aged artificially in the lab and recycled. Then, the third mixtures are made with materials recycled twice. Complex modulus E* and complex Poisson's ratio ν* were then measured for the six considered mixtures. The time-temperature superposition principle (TTSP) was verified. Experimental results were modelled using the Linear Viscoelastic (LVE) 2S2P1D (2 springs, 2 Parabolic Elements and 1 Dashpot) model in 3D. Fitted parameters of the model enable to compare the LVE behaviour of the three mixtures.
This paper presents a 12-year-long creep and shrinkage experimental campaign on cylindrical and prismatic concrete samples under uniaxial and biaxial stress, respectively. The motivation for the ...study is the need for predicting the delayed strains and the pre-stress loss of concrete containment buildings of nuclear power plants. Two subjects are central in this regard: the creep strain's long-term evolution and the creep Poisson's ratio. A greater understanding of these areas is necessary to ensure reliable predictions of the long-term behavior of the concrete containment buildings.
Long-term basic creep appears to evolve as a logarithm function of time in the range of 3 to 10years of testing. Similar trends are observed for drying creep, autogenous shrinkage, and drying shrinkage testing, which suggests that all delayed strains obtained using different loading and drying conditions originate from a common mechanism.
The creep Poisson's ratio derived from the biaxial tests is approximately constant over time for both the basic and drying creep tests (creep strains corrected by the shrinkage strain).
It is also shown that the biaxial non-drying samples undergo a significant increase in Young's modulus after 10years.
In this paper, a sinusoidal honeycomb sandwich panel structure with negative Poisson’s ratio is studied. The impact dynamic response of sandwich panel with two kinds of in-plane and out-of-plane with ...sinusoidal honeycomb structure with the same relative density and different amplitudes at different impact speeds was studied based on ANSYS finite-element software. At different speeds, the sandwich panel impact process is divided into three stages, (a) partial perforation, (b) impact limit, and (c) full perforation. In the stages (a) and (b), the sinusoidal honeycomb is superior to the conventional honeycomb sandwich panel. When reaching the stage (c), the impact reaches the limit, the amplitude increases but the energy decreases, and the energy is almost unchanged when the speed is changed. The results show that the impact resistance of the sinusoidal honeycomb structure is directly related to its amplitude and impact velocity, compared with the conventional quadrangular honeycomb structure, the negative Poisson’s ratio effect of the sinusoidal honeycomb structure can improve the energy absorption capacity of the panel and have better impact resistance, which provides a reference for the design of improving the impact resistance of the structure.
All known oxide glasses are inherently brittle, but their resistance to damage such as hardness and crack resistance varies strongly as a function of the chemical composition. The damage resistance ...is in turn related to the underlying deformation mechanism, which is at least partly related to the Poisson's ratio. That is, glasses with high Poisson's ratio tend to mostly deform through shear flow relative to densification, which leads to ductility in metallic glasses for Poisson's ratio above ~0.33. In this study, we investigate the structure and mechanical properties of a binary zinc borate glass with a relatively high Poisson's ratio (0.30), which we modify by partial substitution of ZnO with La2O3. Glass transition temperature, density, Vickers hardness and crack resistance, as well as elastic constants are studied, in addition to the short and intermediate range structure as probed by 11B solid-state NMR and Raman spectroscopy. We find that the substitution of La for Zn leads to a monotonic increase in Poisson's ratio and elastic moduli, while local maxima are recorded in the trends of glass transition temperature, hardness, and crack resistance. Correlations between the mechanical and structural properties are discussed to shed light onto the structural origin of damage resistance in oxide glasses with high Poisson's ratio.
•Glasses in the xLa2O3 – (55-x)ZnO – 45B2O3 system were studied.•Homogeneous and transparent glasses can be synthesized with up to 10 mol% La2O3.•Short and intermediate range order depend on the degree of La/Zn substitution.•The glasses become denser, harder and stiffer with increasing La2O3 content.•The resistance to radial cracking scales with the propensity to densify
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