Mechanical characterization of the plantar skin tissue: experimental tests and constitutive analysis [English translation]

The study of the mechanical characteristics of the plantar skin has various applications both in the industrial field, such as investigating the interaction between the foot and biomedical devices (e.g., footwear or insoles), and in the clinical domain for diagnosing and monitoring pathologies affecting this anatomical area, such as diabetes, skin tumors, or infections. This paper aims to characterize the mechanical behavior of plantar skin through an experimental and constitutive modeling approach.
Experimental tests were conducted at the Laboratory of Biological Tissue Mechanics at the University of Padua, using human samples from different subjects. The tests that were performed are: compression load-unload tests, uniaxial tensile tests until sample failure and stress-relaxation tests. The results revealed a nonlinear anisotropic behavior concerning both geometry and material, consistent with the current state of the art for this type of tissue.
To describe these characteristics, a visco-hyperelastic fibrous-reinforced model was formulated. Constitutive parameters were determined through a hybrid stochastic and deterministic approach. The analytical model obtained was then used to simulate tensile tests at various angles and deformation speeds. The conducted study allowed for the development of a constitutive model suitable for interpreting the mechanical response of human plantar skin, which can be implemented in a finite element model of the foot.