Citation: Valle, R.; Pincheira, G.;
Tuninetti, V.; Fernandez, E.;
Uribe-Lam, E. Design and
Characterization of Asymmetric Cell
Structure of Auxetic Material for
Predictable Directional Mechanical
Response. Materials 2022, 15, 1841.
https://doi.org/10.3390/
ma15051841
Academic Editors: Ludwig Cardon
and Clemens Holzer
Received: 21 October 2021
Accepted: 7 February 2022
Published: 1 March 2022
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Article
Design and Characterization of Asymmetric Cell Structure of
Auxetic Material for Predictable Directional
Mechanical Response
Rodrigo Valle
1
, Gonzalo Pincheira
2,
* , Víctor Tuninetti
3
, Eduardo Fernandez
4
and Esmeralda Uribe-Lam
5
1
Faculty of Engineering, University of Talca, Talca 3340000, Chile; r.vallefuentes@gmail.com
2
Department of Industrial Technologies, Faculty of Engineering, University of Talca, Talca 3340000, Chile
3
Department of Mechanical Engineering, Universidad de La Frontera, Francisco Salazar 01145,
Temuco 4780000, Chile; victor.tuninetti@ufrontera.cl
4
Department of Aerospace and Mechanical Engineering, University of Liege, 4000 Liege, Belgium;
efsanchez@uliege.be
5
Tecnológico de Monterrey, Escuela de Ingeniería y Ciencias, Querétaro 76130, Mexico; euribelam@tec.mx
* Correspondence: gpincheira@utalca.cl
Abstract:
A three-dimensional auxetic structure based on a known planar configuration including a
design parameter producing asymmetry is proposed in this study. The auxetic cell is designed by
topology analysis using classical Timoshenko beam theory in order to obtain the required orthotropic
elastic properties. Samples of the structure are fabricated using the ABSplus fused filament technique
and subsequently tested under quasi-static compression to statistically determine the Poisson’s ratio
and Young’s modulus. The experimental results show good agreement with the topological analysis
and reveal that the proposed structure can adequately provide different elastic properties in its
three orthogonal directions. In addition, three point bending tests were carried out to determine the
mechanical behavior of this cellular structure. The results show that this auxetic cell influences the
macrostructure to exhibit different stiffness behavior in three working directions.
Keywords:
additive manufacturing; auxetic structures; cellular structures; mechanical characteriza-
tion
1. Introduction
In recent years, academic and industry research focusing on additive manufacturing
(AM) has had an undoubted increase, mainly due to the possibility offered by this technol-
ogy to fabricate components with complex geometries and less material waste compared
to conventional manufacturing methods [
1
]. Another benefit of AM is the possibility
of manufacturing cellular structures [
2
] or complex configurations generally formed by
interconnected nodes and struts that maintain a periodic pattern [
3
,
4
]. These structures
can present multiple attractive properties depending on the specific application, such as
light weight, high specific stiffness, and high energy absorption capacity [
5
–
9
]. Sandwich
panel fabrication is one of the most widely studied and reported in the literature [
10
–
15
].
Properties such as high impact energy absorption increase the use of cellular materials as
protective structures [
16
–
18
]. The designs of these engineered structures are often inspired
by nature, giving way to new cellular materials whose microstructure is present in nat-
ural biological configurations [
19
,
20
]. Examples are structures imitating the honeycomb
cell, one of the most studied cases in lightweight applications, which are used in sand-
wich panels in the aerospace and packaging industry due to their high stiffness and low
density [10,11,16,21,22].
The literature contains various studies of modeling and experimental characterization
of cellular structures [
23
–
29
], showing that these microstructured materials can be designed
Materials 2022, 15, 1841. https://doi.org/10.3390/ma15051841 https://www.mdpi.com/journal/materials
