Auxetic multiphase soft composite material design through instabilities with application for acoustic metamaterials

Area of Science:

• Materials Science
• Mechanical Engineering
• Composite Materials

Background:

• Soft composites with periodic inclusions and voids can exhibit auxetic behavior.
• Elastic instabilities are key to microstructural rearrangements in these materials.

Purpose of the Study:

• To investigate instability-induced pattern transformations in 3D-printed soft composites.
• To explore how these transformations lead to tunable negative Poisson's ratio (NPR) behavior.
• To demonstrate potential applications in acoustic-elastic metamaterials.

Main Methods:

• Fabrication of 3D-printed soft composites with controlled microstructures.
• Mechanical testing to induce elastic instabilities and observe pattern transformations.
• Microstructural analysis to characterize new morphologies.
• Acoustic-elastic property evaluation.

Main Results:

• Soft auxetic composites undergo reversible pattern transformations upon reaching elastic instability.
• Identical composites form distinct microstructural patterns based on loading direction.
• These distinct patterns result in significantly different negative Poisson's ratio (NPR) behaviors.
• Tunable NPR properties are achieved through controlled pattern morphing.

Conclusions:

• Instability-induced pattern transformations offer a mechanism for enhanced tunability in soft composite properties.
• Reversible pattern changes enable the development of tunable acoustic-elastic metamaterials.
• These metamaterials can selectively filter low-frequency acoustic ranges based on deformation.