Macroscale Double Networks: Design Criteria for Optimizing Strength and Toughness

Area of Science:

• Materials Science
• Polymer Science
• Mechanical Engineering

Background:

• The double network concept, utilizing sacrificial bond fracture, has advanced robust soft material development.
• Existing methods often rely on molecular-scale networks and strong interfacial adhesion.

Purpose of the Study:

• To adapt the double network concept for macroscale, 3D-printed rigid sacrificial networks within stretchable matrices.
• To investigate the relationship between sacrificial network strength, density, and material performance.
• To demonstrate a generalizable method for creating tough, dissipative materials without requiring strong interfacial adhesion.

Main Methods:

• Embedding macroscale, 3D-printed rigid sacrificial networks into silicone rubber matrices.
• Systematically varying sacrificial network strength and bond density.
• Analyzing material response, including stiffness, work of extension, yield strength, and energy dissipation.

Main Results:

• Achieved a ~60-fold increase in stiffness and a ~50% increase in work of extension compared to the neat matrix.
• Identified optimal conditions where sacrificial network strength approaches matrix strength for maximized yield strength and multistep fracture.
• Attained toughening efficiencies up to ~70% of theoretical maximums through topological interlocking and high sacrificial bond density.

Conclusions:

• The double network concept is effective at macroscales, extending beyond molecular applications.
• Topological interlocking facilitates efficient force transmission, enabling high toughness and energy dissipation.
• This approach offers a versatile platform for developing advanced structural materials with tunable properties.