Three-dimensional structure of a sheet crumpled into a ball

Area of Science:

• Materials Science
• Physics
• Mechanical Engineering

Background:

• Forced crumpling of thin sheets results in low-volume fraction structures with significant resistance to compression.
• This far-from-equilibrium process may not be fully described by initial sheet parameters and final confinement alone.
• The internal geometry and mechanical properties can be influenced by the crumpling preparation history.

Purpose of the Study:

• To investigate the internal three-dimensional geometry of crumpled sheets.
• To determine if crumpling processes leave subtle fingerprints of their preparation history.
• To analyze the relationship between compression, volume fraction, and internal structure.

Main Methods:

• Utilizing X-ray microtomography experiments to probe the internal structure of crumpled sheets.
• Analyzing the three-dimensional geometry and homogeneity of the crumpled state.
• Quantifying the degree of local ordering and its dependence on compression.

Main Results:

• The internal three-dimensional geometry of crumpled balls is largely isotropic and homogeneous.
• This homogeneity is comparable to other non-equilibrium systems like turbulence.
• Local nematic ordering of the sheet into parallel stacks was observed, proceeding radially inward.
• The extent of this layering increases with the volume fraction (degree of compression).

Conclusions:

• Crumpling, while appearing homogeneous, exhibits local ordering influenced by preparation history.
• The observed radial layering provides a subtle but discernible fingerprint of the crumpling process.
• Understanding this internal structure is crucial for predicting the mechanical behavior of crumpled materials.