Plasticity and aging of folded elastic sheets

Area of Science:

• Materials Science
• Mechanics of Materials
• Metamaterials

Background:

• Creased material sheets exhibit complex behaviors under mechanical loading.
• Understanding dissipative mechanisms like plasticity and relaxation is crucial for material design.
• Crease-based metamaterials offer unique functionalities but require detailed characterization.

Purpose of the Study:

• To investigate the dissipative mechanisms (plasticity and relaxation) in creased material sheets.
• To develop a method for tracking the reference configuration of creases under arbitrary loading paths.
• To explore the relationship between crease-level phenomena and macroscopic material behavior.

Main Methods:

• Mechanical loading experiments on creased material sheets.
• Analysis of plasticity effects on crease rest angles.
• Development of a mapping between crease rest angle and macroscopic system state.
• Characterization of relaxation phenomena, including memory effects, using double-logarithmic time evolution.

Main Results:

• Plasticity primarily influences the rest angle of creases.
• A novel mapping allows tracking of the crease reference configuration during loading, serving as a design tool.
• Complex relaxation and memory effects lead to non-monotonic responses at the crease level.
• Observed phenomena are described by classical time evolution, revealing constitutive behavior linked to the bulk material.

Conclusions:

• Crease mechanics provide magnified access to the underlying material's rheology.
• The developed mapping is a valuable tool for monitoring and designing crease-based metamaterials.
• Understanding crease-level dissipative mechanisms is key to predicting and controlling the behavior of folded and crumpled structures.