scholarly journals Computational Investigation of the Effective Mechanical Behavior for 3D Pre-Buckled Auxetic Lattices

2019 ◽  
Vol 86 (11) ◽  
Author(s):  
Frederic Albertini ◽  
Justin Dirrenberger ◽  
Andrey Molotnikov ◽  
Cyrille Sollogoub
Keyword(s):  
Elastic Properties ◽  
Poisson Ratio ◽  
Periodic Boundary Conditions ◽  
Homogenization Method ◽  
Geometrical Parameters ◽  
Computational Investigation ◽  
Effective Elastic Properties ◽  
Acoustic Damping ◽  
The Past ◽  
Geometric Configurations

Abstract Negative Poisson’s ratio materials, or auxetics, have drawn attention for the past 30 years. The auxetic effect could lead to improved mechanical properties such as acoustic damping, indentation resistance, or crashworthiness. In this work, two 3D auxetic lattices are introduced. Auxeticity is achieved by design through pre-buckling of the lattice struts. The influence of geometrical parameters on the effective elastic properties is investigated using computational homogenization method with periodic boundary conditions. Effective Young’s modulus is 3D mapped to reveal anisotropy and identify spatial orientations of interest. The effective Poisson ratio is computed for various geometric configurations to characterize auxeticity. Finally, the influence of effective elastic properties on energy dissipation under compression is explored for elastoplastic lattices with different loading directions, using finite element simulations. Results suggest that loading 3D auxetic lattices along their stiffest direction maximizes their crashworthiness.

Randomly Dispersed Coated Composites Study by Statistical Approach and Numerical Homogenization Method

2021 ◽  
Vol 54 ◽  
pp. 33-42
Author(s):  
Kamel Fedaoui ◽  
Mohammed Said Boutaani ◽  
Amor Bourebbou ◽  
Laid Chaibainou ◽  
Abdelyamine Boukhobza
Keyword(s):  
Boundary Conditions ◽  
Elastic Properties ◽  
Statistical Approach ◽  
Periodic Boundary Conditions ◽  
Homogenization Method ◽  
Analytical Models ◽  
Numerical Homogenization ◽  
Effective Elastic Properties ◽  
Coated Materials ◽  
Integral Range

The aim of this work is the computation of effective elastic properties of 3D 3-phase random heterogeneous coated materials. For that, a new expression of the integral range for 3-phase random coated heterogeneous materials is used. The computation is achieved using a representative microstructure with non-overlapping inclusions. Numerical simulations is used under periodic boundary conditions (PBC) and kinematic uniform boundary conditions (KUBC) prescribed over Representative Volume Element (RVE). The obtained effective elastic properties are compared with different analytical models as Hashin and Shtrikman bounds and the n+1 phase model. Using the statistical methods, a new extension of the integral range for 3-phase coated materials is proposed.

A flexible homogenization method for the effective elastic properties of cement pastes with w/c effect

2020 ◽  
Vol 134 ◽  
pp. 106106 ◽  
Author(s):  
Tuan Nguyen-Sy ◽  
Trung-Kien Nguyen ◽  
Van-Dong Dao ◽  
Khuong Le-Nguyen ◽  
Ngoc-Minh Vu ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Homogenization Method ◽  
Cement Pastes ◽  
Effective Elastic Properties

Micromechanical modeling of 3D printable interpenetrating phase composites with tailorable effective elastic properties including negative Poisson's ratio

2017 ◽  
Vol 02 (04) ◽  
pp. 1750015 ◽  
Author(s):  
L. Ai ◽  
X.-L. Gao
Keyword(s):  
Elastic Properties ◽  
Effective Properties ◽  
Matrix Material ◽  
Micromechanical Model ◽  
Micromechanical Modeling ◽  
Tetragonal Symmetry ◽  
Geometrical Parameters ◽  
Fe Model ◽  
Effective Elastic Properties ◽  
Interpenetrating Phase Composites

3D printable two-phase interpenetrating phase composites (IPCs) are designed by embedding a 3D periodic re-entrant lattice structure (as the reinforcing phase) in a matrix phase. These IPCs display the cubic or tetragonal symmetry. A micromechanical model is developed to evaluate effective elastic properties of the IPCs. Effective Young's moduli, shear moduli and Poisson's ratios (PRs) of each IPC are determined from the effective stiffness and compliance matrices of the composite, which are obtained through a homogenization analysis using a unit cell-based finite element (FE) model incorporating periodic boundary conditions. The FE simulation results are also compared with those based on various analytical bounding techniques in micromechanics, including the Voigt–Reuss, Hashin–Shtrikman, and Tuchinskii bounds. The effective properties of the IPC can be tailored by adjusting five geometrical parameters, including two strut lengths, two re-entrant angles and one strut diameter, and elastic properties of the two constituent materials. The numerical results reveal that IPCs with a negative PR can be generated by using a compliant matrix material and large re-entrant angles. In addition, it is found that the two re-entrant angles can greatly affect other effective elastic properties of the IPC: the effective shear modulus can be enhanced, while the effective Young's modulus can be enhanced or compromised with the increase of the re-entrant angles. Furthermore, it is seen that by adjusting one of the two re-entrant angles or one of the two strut lengths, the material symmetry exhibited by the IPC can be changed from cubic to tetragonal.

First-Principles Calculations of Thermoelectric PbSe2 Compound to Predict its Elastic Properties

2019 ◽  
Vol 956 ◽  
pp. 46-54
Author(s):  
Jia Fu ◽  
Tian Hou ◽  
Jing Rui Chen
Keyword(s):  
Young’S Modulus ◽  
Elastic Properties ◽  
First Principles ◽  
Elastic Anisotropy ◽  
Young's Modulus ◽  
Poisson Ratio ◽  
Structural Parameters ◽  
Homogenization Method ◽  
Parameter Method ◽  
G Ratio

The influencing effect of pressure on structural stability and elastic properties of PbSe2 compound is mainly investigated by first-principles method and homogenization method of the Y parameter. The optimized structural parameters at zero pressure are a=b=6.446Å, c=7.887Å (GGA method) and a=b=6.316Å, c=7.651Å (LDA method), which has good agreement with the experimental and theoretical values. Our calculated lattice parameters and Se-Se bond length are in excellent agreement with experimental data. PbSe2 compound is energetically stable with a good alloying ability. The elastic constants are calculated, and then the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio and anisotropy factor are determined. Besides, Y parameter method is used to investigate changes of the Poisson ratio, Young’s and shear moduli of PbSe2 within different normal orientation crystal planes. Results show that: 1) Young’s modulus is about 48.37 GPa from GGA and 58.87 GPa from LDA by Reuss-Voigt-Hill estimation, which is averaged about 53.62 GPa; 2) The PbSe2 compound is ductile according to B/G ratio. The universal anisotropic index AU shows that PbSe2 exhibits a fairly high elastic anisotropy.

On the Mechanical Behavior of the Orthotropic Cord-Rubber Composite

1976 ◽  
Vol 4 (4) ◽  
pp. 219-232 ◽  
Author(s):  
Ö. Pósfalvi
Keyword(s):  
Mechanical Behavior ◽  
Uniaxial Tension ◽  
Elastic Properties ◽  
Large Deformations ◽  
Virtual Work ◽  
Poisson's Ratio ◽  
Principle Of Virtual Work ◽  
Effective Elastic Properties ◽  
Rubber Composite ◽  
Mooney Equation

Abstract The effective elastic properties of the cord-rubber composite are deduced from the principle of virtual work. Such a composite must be compliant in the noncord directions and therefore undergo large deformations. The Rivlin-Mooney equation is used to derive the effective Poisson's ratio and Young's modulus of the composite and as a basis for their measurement in uniaxial tension.

scholarly journals From Bend to Splay Dominated Elasticity in Nematics

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 831
Author(s):  
Davide Revignas ◽  
Alberta Ferrarini
Keyword(s):  
Liquid Crystal ◽  
Nematic Phase ◽  
Low Cost ◽  
Elastic Behavior ◽  
Computational Investigation ◽  
Apical Angle ◽  
Polar Order ◽  
The Past ◽  
Bend Angles ◽  
Analogous Effect

In the past decade, much evidence has been provided for an unusually low cost for bend deformations in the nematic phase of bent-core mesogens and bimesogens (liquid crystal dimers) having a bent shape on average. Recently, an analogous effect was observed for the splay mode of bent-core mesogens with an acute apical angle. Here, we present a systematic computational investigation of the Frank elastic constants of nematics made of V-shaped particles, with bend angles ranging from acute to obtuse. We show that by tuning this angle, the elastic behavior switches from bend dominated (K33>K11) to splay dominated (K11>K33), with anomalously low values of the splay and the bend constant, respectively. This is related to a change in the shape polarity of particles, which is associated with the emergence of polar order, longitudinal for splay and transversal for bend deformations. Crucial to this study is the use of a recently developed microscopic elastic theory, able to account for the interplay of mesogen morphology and director deformations.

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