Dissipation and recovery in collagen fibrils under cyclic loading: A molecular dynamics study

Area of Science:

• Biomaterials Science
• Computational Biology
• Soft Matter Physics

Background:

• Collagen fibrils exhibit hysteretic behavior under cyclic loading, involving strain dissipation and accumulation.
• Partial recovery of strain is observed upon relaxation, with cross-links playing a critical role in mechanical properties.

Purpose of the Study:

• To modify a coarse-grained molecular dynamics model of collagen fibrils to incorporate cross-link reformation.
• To investigate the role of cross-link reformation in the recovery of residual strain and energy dissipation during cyclic loading.

Main Methods:

• Utilized a modified coarse-grained molecular dynamics model for collagen fibrils.
• Simulated cyclic loading and relaxation to observe hysteretic behavior and strain recovery.
• Analyzed the influence of the degree of cross-linking on macroscopic mechanical responses.

Main Results:

• The model successfully replicated experimental observations, including hysteresis loop movement, residual strain evolution, and energy dissipation.
• Simulations demonstrated partial recovery of strain during relaxation, consistent with experimental data.
• The characteristic cycle number for approaching steady state was found to be similar to experimental values.

Conclusions:

• Cross-link reformation is vital for the recovery of residual strain in collagen fibrils during cyclic loading.
• The degree of cross-linking significantly impacts the macroscopic mechanical response of collagen fibrils.
• The developed model accurately captures key hysteretic and recovery features of collagen fibril behavior.