Resilient 3D hierarchical architected metamaterials.

Area of Science:

• Materials Science
• Mechanical Engineering
• Nanotechnology

Background:

• Hierarchical structures in natural and artificial materials enhance mechanical properties.
• The precise role of hierarchy in material resilience is not fully understood.
• Existing nanolattices lack optimal hierarchical design.

Purpose of the Study:

• To create and investigate hierarchical structural metamaterials using fractal-like geometries.
• To explore the mechanical performance of hierarchical designs in polymer, ceramic, and composite systems.
• To understand the relationship between hierarchical order and material resilience.

Main Methods:

• Fabrication of hierarchical metamaterials from polymer, hollow ceramic, and ceramic-polymer composites.
• In situ nanomechanical testing under compression.
• Development of a computational model for stress distribution analysis.

Main Results:

• Achieved near-theoretical scaling of strength and stiffness with density, surpassing non-hierarchical nanolattices.
• Demonstrated high recoverability (up to 98%) in hollow alumina samples after significant strain.
• Suppressed brittle failure and instabilities in hierarchical ceramic nanolattices.
• Identified tunable deformation mechanisms based on beam slenderness ratios.

Conclusions:

• Hierarchical design significantly enhances mechanical robustness and damage tolerance.
• An optimal degree of hierarchy exists, beyond which strength and stiffness do not increase.
• Computational models can elucidate deformation mechanisms and validate metamaterial properties.