An Invariant-Based Damage Model for Human and Animal Skins

Area of Science:

• Biomechanics
• Materials Science
• Dermatology

Background:

• Understanding skin's mechanical properties is crucial for clinical applications like injury assessment and artificial skin development.
• Existing models often lack the ability to accurately capture complex damage mechanisms in diverse skin types.

Purpose of the Study:

• To propose a novel, nonlinear, anisotropic, invariant-based constitutive damage model for human and animal skins.
• To validate the model's performance using experimental data from various species and skin locations.

Main Methods:

• The model is based on the Gasser-Ogden-Holzapfel constitutive law, incorporating collagen fiber orientation and dispersion.
• Material parameters were inversely estimated using uniaxial test data and MATLAB optimization.
• Model performance was assessed using root mean square error and sensitivity analysis.

Main Results:

• The model accurately describes skin behavior across human, swine, rabbit, bovine, and rhino samples, with RMSE between 2.15% and 12.18%.
• Collagen fiber orientation dispersion and mean angle significantly influence model behavior and require histological data for reliable estimation.
• Skin damage can be brittle (fiber breaking) or ductile (fiber and matrix damage), varying by species and anatomical location (back vs. belly).

Conclusions:

• The developed constitutive model provides a robust framework for analyzing skin damage.
• It offers valuable insights for clinical applications involving skin trauma, aging, and biomechanical studies.
• The model's ability to differentiate between brittle and ductile damage expands its utility in understanding tissue response.