Interpretation of static and dynamic Young’s moduli and Poisson’s ratio of granular assemblies under shearing

2022 ◽  
Vol 142 ◽  
pp. 104560
Author(s):  
Yang Li ◽  
Masahide Otsubo ◽  
Reiko Kuwano
Keyword(s):  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Young’S Moduli ◽  
Granular Assemblies

Biomimetic composites inspired by venous leaf

2017 ◽  
Vol 52 (3) ◽  
pp. 361-372 ◽  
Author(s):  
Gongdai Liu ◽  
R Ghosh ◽  
A Vaziri ◽  
A Hossieni ◽  
D Mousanezhad ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Yield Stress ◽  
Poisson’S Ratio ◽  
Composite Structures ◽  
Volume Fraction ◽  
Matrix Material ◽  
Poisson's Ratio ◽  
Fiber Volume ◽  
Young’S Moduli

A typical plant leaf can be idealized as a composite having three principal fibers: the central mid-fiber corresponding to the mid-rib, straight parallel secondary fibers attached to the mid-fiber representing the secondary veins, and then another set of parallel fibers emanating from the secondary fibers mimicking the tertiary fibers embedded in a matrix material. This paper introduces a biomimetic composite design inspired by the morphology of venous leafs and investigates the effects of venation morphologies on the in-plane mechanical properties of the biomimetic composites using finite element method. The mechanical properties such as Young’s moduli, Poisson’s ratio, and yield stress under uniaxial loading of the resultant composite structures was studied and the effect of different fiber architectures on these properties was investigated. To this end, two broad types of architectures were used both having similar central main fiber but differing in either having only secondary fibers or additional tertiary fibers. The fiber and matrix volume fractions were kept constant and a comparative parametric study was carried out by varying the inclination of the secondary fibers. The results show that the elastic modulus of composite in the direction of main fiber increases linearly with increasing the angle of the secondary fibers. Furthermore, the elastic modulus is enhanced if the secondary fibers are closed, which mimics composites with closed cellular fibers. In contrast, the elastic modulus of composites normal to the main fiber ( x direction) exponentially decreases with the increase of the angle of the secondary fibers and it is little affected by having secondary fibers closed. Similar results were obtained for the yield stress of the composites. The results also indicate that Poisson’s ratio linearly increases with the secondary fiber angle. The results also show that for a constant fiber volume fraction, addition of various tertiary fibers may not significantly enhance the mechanical properties of the composites. The mechanical properties of the composites are mainly dominated by the secondary fibers. Finally, a simple model was proposed to predict these behaviors.

Poisson's ratio of plywood measured by tension test

Holzforschung ◽  
2009 ◽  
Vol 63 (5) ◽  
Author(s):  
Hiroshi Yoshihara
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Poisson’S Ratio ◽  
Tension Test ◽  
Experimental Results ◽  
Poisson's Ratio ◽  
Element Analysis ◽  
Young’S Moduli ◽  
Tension Tests ◽  
Finite Element Calculations

Abstract In this research, Poisson's ratio of plywood as obtained by a tension test was examined by varying the width of the specimen. The tension tests were conducted on five-plywood of lauan (Shorea sp.) with various widths, and Young's moduli and Poisson's ratios of the specimens were measured. Finite element calculations were independently conducted. A comparison of the experimental results with those of finite element analysis revealed that Young's modulus could be obtained properly when the width of the plywood strip varied. In contrast, the width of the plywood strip should be large enough to determine Poisson's ratio properly.

Dependence of Poisson’s ratio and Young’s modulus on microfibril angle (MFA) in wood

Holzforschung ◽  
2018 ◽  
Vol 72 (4) ◽  
pp. 321-327
Author(s):  
Kosei Ando ◽  
Mayu Mizutani ◽  
Keisuke Toba ◽  
Hiroyuki Yamamoto
Keyword(s):  
Cell Wall ◽  
Poisson’S Ratio ◽  
Microfibril Angle ◽  
Japanese Cedar ◽  
Poisson's Ratio ◽  
Japanese Cypress ◽  
Underlying Assumption ◽  
Orthotropic Elasticity ◽  
Young’S Moduli

AbstractMicrofibril angle (MFA) is a major structural variable that describes the fine structure of the cell wall in wood. In this study, the relationships between the MFA of the S2 layer and the Poisson’s ratios and Young’s moduli (modulus of elasticity, MOE) of five wood species (agathis, larch, Japanese cedar, Japanese cypress and ginkgo) were determined by analyzing both their normal and compression woods. It was found that both the longitudinal MOE (MOEL) and MOE of the cell-wall substance (MOEW) decreased with increasing MFA, while the peaks values of Poisson’s ratio (νLT) were obtained at MFAs of ≈25°. In particular, at MFAs lower than 25°, theνLTincreased with increasing MFA, and the opposite relationship was observed at MFA values exceeding 25°. This trend is in good agreement with the estimates obtained based on the theory of orthotropic elasticity with the underlying assumption that the orthotropic elasticity of materials is MFA-dependent. Hence, the MFA parameter incorporated into the orthotropic elasticity theory is useful for determination of the Poisson’s ratio.

Micromechanical Aspects of Isotropic Granular Assemblies With Linear Contact Interactions

1988 ◽  
Vol 55 (1) ◽  
pp. 17-23 ◽  
Author(s):  
R. J. Bathurst ◽  
L. Rothenburg
Keyword(s):  
Numerical Simulations ◽  
Contact Force ◽  
Elastic Constants ◽  
Poisson’S Ratio ◽  
Three Dimensional ◽  
Poisson's Ratio ◽  
Spherical Particles ◽  
Two Dimensional ◽  
Normal Contact ◽  
Granular Assemblies

The paper presents a micromechanical analysis of plane granular assemblies of discs with a range of diameters, and interacting according to linear contact force-interparticle compliance relationships. Contacts are assumed to be fixed and indestructible. Macroscopically, the system is described in terms of a two-dimensional analogue of generalized Hooke’s law. Explicit expressions for elastic constants in terms of microstructure are derived for dense isotropic assemblies. It is shown that Poisson’s ratio for dense systems depends on the ratio of tangential to normal contact stiffnesses. The derived expression for Poisson’s ratio is verified by numerically simulating plane assemblies comprising 1000 particles. The effect of density on Poisson’s ratio is investigated using numerical simulations. The theory of dense plane systems is extended to dense three-dimensional systems comprising spheres. Finally, it is shown that Poisson’s result ν=1/4 is recovered for spherical particles with central interactions.

scholarly journals Effect of Compressive Strain Rate on Auxetic Foam

2021 ◽  
Vol 11 (3) ◽  
pp. 1207
Author(s):  
Olly Duncan ◽  
Nicolas Bailly ◽  
Tom Allen ◽  
Yvan Petit ◽  
Eric Wagnac ◽  
...  
Keyword(s):  
Strain Rate ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Strain Rates ◽  
Open Cell ◽  
Young’S Moduli ◽  
Closed Cell ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
Cell Foam

Auxetic foams have previously been shown to have benefits including higher indentation resistance than their conventional counterparts, due to their negative Poisson’s ratio, making them better at resisting penetration by concentrated loads. The Poisson’s ratio and Young’s modulus of auxetic open cell foams have rarely been measured at the high compressive strain rates typical during impacts of energy absorbing material in sporting protective equipment. Auxetic closed cell foams are less common than their open cell counterparts, and only their quasi-static characteristics have been previously reported. It is, therefore, unclear how the Poisson’s ratio of auxetic foam, and associated benefits such as increased indentation resistance shown at low strain rates, would transfer to the high strain rates expected under impact. The aim of this study was to measure the effect of strain rate on the stiffness and Poisson’s ratio of auxetic and conventional foam. Auxetic open cell and closed cell polymer foams were fabricated, then compression tested to ~80% strain at applied rates up to 200 s−1, with Poisson’s ratios obtained from optical full-field strain mapping. Open cell foam quasi-static Poisson’s ratios ranged from −2.0 to 0.4, with a narrower range of −0.1 to 0.3 for closed cell foam. Poisson’s ratios of auxetic foams approximately halved in magnitude between the minimum and maximum strain rates. Open cell foam quasi-static Young’s moduli were between 0.02 and 0.09 MPa, whereas closed cell foams Young’s moduli were ~1 MPa, which is like foam in protective equipment. The Young’s moduli of the auxetic foams approximately doubled at the highest applied strain rate of 200 s−1.

The Model for Calculating Elastic Modulus and Poisson's Ratio of Coal Body

2013 ◽  
Vol 6 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Ai Chi ◽  
Li Yuwei
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Fractured Rock ◽  
Rock Block ◽  
Poisson's Ratio ◽  
Linear Elastic ◽  
Study Results ◽  
The Face ◽  
Block Face ◽  
Coal Rock

Coal body is a type of fractured rock mass in which lots of cleat fractures developed. Its mechanical properties vary with the parametric variation of coal rock block, face cleat and butt cleat. Based on the linear elastic theory and displacement equivalent principle and simplifying the face cleat and butt cleat as multi-bank penetrating and intermittent cracks, the model was established to calculate the elastic modulus and Poisson's ratio of coal body combined with cleat. By analyzing the model, it also obtained the influence of the parameter variation of coal rock block, face cleat and butt cleat on the elastic modulus and Poisson's ratio of the coal body. Study results showed that the connectivity rate of butt cleat and the distance between face cleats had a weak influence on elastic modulus of coal body. When the inclination of face cleat was 90°, the elastic modulus of coal body reached the maximal value and it equaled to the elastic modulus of coal rock block. When the inclination of face cleat was 0°, the elastic modulus of coal body was exclusively dependent on the elastic modulus of coal rock block, the normal stiffness of face cleat and the distance between them. When the distance between butt cleats or the connectivity rate of butt cleat was fixed, the Poisson's ratio of the coal body initially increased and then decreased with increasing of the face cleat inclination.

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