The Science Behind Stronger, Smarter Materials

The Science Behind Stronger, Smarter Materials


Abstract and 1. Introduction

1.1 A Polyethylene-based metamaterial for acoustic control

2 Relaxed micromorphic modelling of finite-size metamaterials

2.1 Tetragonal Symmetry / Shape of elastic tensors (in Voigt notation)

3 Dispersion curves

4 New considerations on the relaxed micromorphic parameters

4.1 Consistency of the relaxed micromorphic model with respect to a change in the unit cell’s bulk material properties

4.2 Consistency of the relaxed micromorphic model with respect to a change in the unit cell’s size

4.3 Relaxed micromorphic cut-offs

5 Fitting of the relaxed micromorphic parameters: the particular case of vanishing curvature (without Curl P and Curl P˙)

5.1 Asymptotes

5.2 Fitting

5.3 Discussion

6 Fitting of the relaxed micromorphic parameters with curvature (with Curl P)

6.1 Asymptotes and 6.2 Fitting

6.3 Discussion

7 Fitting of the relaxed micromorphic parameters with enhanced kinetic energy (with Curl P˙) and 7.1 Asymptotes

7.2 Fitting

7.3 Discussion

8 Summary of the obtained results

9 Conclusion and perspectives, Acknowledgements, and References

A Most general 4th order tensor belonging to the tetragonal symmetry class

B Coefficients for the dispersion curves without Curl P

C Coefficients for the dispersion curves with P

D Coefficients for the dispersion curves with P◦

7.1 Asymptotes

Again, the cut-offs are independent on the coefficients with higher order of k and thus they do not change with respect to the two previous cases. For the asymptotes we only consider the terms with the highest order of k available and compute

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We have again three asymptotes (the roots of a third order polynomial) which in general causes the analytical expressions to be impractical rather quickly. However, in this case it is possible to find one root by hand

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7.2 Fitting

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7.3 Discussion

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Figure 6: Dispersion curves ω(k) for 0 degrees (left) and 45 degrees (right) with pressure curves colored in yellow and shear in blue. The dots are the points computed with Comsol Multiphysics® while the smooth curves show the analytical expression of the dispersion curves for the relaxed micromorphic model. The value of the curve’s horizontal asymptotes are also shown with dashed lines.

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This paper is available on arxiv under CC BY 4.0 DEED license.

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Authors:

(1) Jendrik Voss, Institute for Structural Mechanics and Dynamics, Technical University Dortmund and a Corresponding Author (jendrik.voss@tu-dortmund.de);

(2) Gianluca Rizzi, Institute for Structural Mechanics and Dynamics, Technical University Dortmund;

(3) Patrizio Neff, Chair for Nonlinear Analysis and Modeling, Faculty of Mathematics, University of Duisburg-Essen;

(4) Angela Madeo, Institute for Structural Mechanics and Dynamics, Technical University Dortmund.

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