Unlocalized crack initiation and propagation in staggered biomaterials

Area of Science:

• Materials Science
• Biomimetics
• Mechanics of Materials

Background:

• Living tissues often combine diverse properties for mechanical functions.
• Nacre, a natural biomaterial, demonstrates remarkable strength and toughness due to its composition and structure.
• Existing models often overlook microscopic crack initiation in nacre's toughness.

Purpose of the Study:

• To investigate crack initiation and propagation mechanisms in staggered biomaterials.
• To model crack behavior without assuming pre-existing cracks.
• To clarify the role of intrinsic material properties in crack development.

Main Methods:

• Fracture mechanics principles.
• Cohesive zone modeling.
• Energy-based stability analysis.

Main Results:

• Identified two crack propagation modes: localized and unlocalized.
• Localized mode: crack initiates and propagates in a small area.
• Unlocalized mode: cracks initiate at multiple points and follow diverse paths.
• Shear interfacial mechanisms were found to significantly delay crack initiation.

Conclusions:

• The study elucidates crack initiation and propagation in biomaterials without pre-existing flaws.
• Intrinsic material properties, particularly shear interfacial mechanisms, are crucial for delaying crack initiation.
• Findings offer insights for designing tougher artificial materials inspired by nacre.