Ideal isotropic auxetic networks from random networks

Area of Science:

• Materials Science
• Mechanical Engineering
• Physics

Background:

• Auxetic materials possess a negative Poisson's ratio (ν), exhibiting unique deformation characteristics.
• Approaching the isotropic mechanical limit (ν = -1) enhances resistance to impact and shear, crucial for advanced applications.
• Previous attempts to achieve near-limit isotropic auxetic behavior were hindered by anisotropy or 3D fabrication challenges.

Purpose of the Study:

• To present a novel design strategy for creating isotropic auxetic materials.
• To overcome limitations of previous designs, enabling practical 3D fabrication and enhanced auxetic properties.

Main Methods:

• Development of a design strategy based on disordered networks.
• Fabrication of the designed structures in a laboratory setting.
• Experimental characterization to validate predicted mechanical behavior, including Poisson's ratio measurement.

Main Results:

• Achieved isotropic auxetic materials with Poisson's ratios as low as ν = -0.98.
• Successfully fabricated materials that exhibit predicted auxetic behavior.
• Identified the dependence of ν on network structure and bond strengths, elucidating key design principles.

Conclusions:

• The proposed design strategy effectively generates isotropic auxetic materials with near-limit properties.
• The findings provide fundamental insights into the structural features governing auxetic behavior.
• The approach is generalizable to various materials, dimensions, and scales, offering a versatile platform for technological innovation.