Bio-inspired space-filling fractal metamaterial

Area of Science:

• Materials Science and Engineering
• Mechanical Engineering
• Bio-inspired Design

Background:

• Mammal cranial sutures exhibit spatiotemporal morphological variation, inspiring novel material design.
• Fractal geometry offers a framework for creating complex, hierarchical structures.
• Metamaterials possess engineered properties not found in naturally occurring materials.

Purpose of the Study:

• To design and fabricate two-phase space-filling fractal metamaterials inspired by cranial sutures.
• To evaluate the mechanical performance of these metamaterials with varying complexity.
• To understand the relationship between structural hierarchy and mechanical properties.

Main Methods:

• Bio-inspired design of two-phase space-filling fractal metamaterials with hierarchical number N.
• Fabrication using multi-material polymer jetting.
• Mechanical testing (tensile tests) and finite element (FE) simulations.

Main Results:

• Increasing hierarchical number N enhances stiffness, strength, and toughness under tensile loading.
• FE simulations reveal that the hard phase contributes increasingly to strain energy density with higher N.
• Overall mechanical properties are dominated by the volume fraction and stiffness ratio of the hard phase.

Conclusions:

• Hierarchical complexity is a critical factor in tuning the mechanical behavior of these metamaterials.
• The hard phase's properties and fraction are key design parameters for optimizing mechanical performance.
• Bio-inspired fractal metamaterials show promise for energy dissipation, impact mitigation, and damage retardation in engineering applications.