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Geometric Analysis and Experimental Studies of Hexachiral Structures
Julian Plewa1, Małgorzata Płońska1, Kamil Feliksik1
1Faculty of Science and Technology, Institute of Materials Engineering, University of Silesia in Katowice, 75 Pułku Piechoty Str., 41-500 Chorzów, Poland.
Materials (Basel, Switzerland)
|September 27, 2025
Summary
Chiral metamaterials with hexachiral structures show auxetic behavior, contracting under compression. Their negative Poisson
Area of Science:
- Metamaterials Science
- Materials Physics
- Mechanical Engineering
Background:
- Chiral metamaterials possess inherent asymmetry, preventing overlap with their mirror images.
- Hexachiral structures, composed of nodes and ligaments, are a type of chiral metamaterial.
- Auxetic materials exhibit a negative Poisson's ratio, expanding when stretched and contracting when compressed.
Purpose of the Study:
- To investigate the auxetic properties of hexachiral metamaterial structures.
- To determine the Poisson's ratio of these structures under various compression conditions.
- To explore the relationship between structure geometry and auxetic performance.
Main Methods:
- Theoretical analysis and geometric calculations of hexachiral structures.
- Experimental fabrication of metamaterial structures using 3D printed nodes and ligaments.
- Uniaxial and multi-directional compression testing of the fabricated structures.
Main Results:
- Hexachiral structures demonstrated a negative Poisson's ratio approaching -1 under compression.
- The Poisson's ratio was found to be independent of compression degree for uniaxial loading.
- Structure deformation varied across different parts during uniaxial compression.
- Multi-directional compression also resulted in a negative Poisson's ratio near -1, dependent on compression degree.
Conclusions:
- Hexachiral metamaterials exhibit significant auxetic properties with a Poisson's ratio close to -1.
- The number of unit cells influences the Poisson's ratio, approaching theoretical values in larger structures.
- These structures can function as elastic energy reservoirs, showing auxetic behavior under multi-directional stress.
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