Human skin is the largest organ of the human body. It has a stratified structure consisting of four main layers: the stratum corneum, the viable epidermis, the dermis and the hypodermis. The skin protects the body against external influences when exposed to sun or to undesirable substances in case of pollution and to the direct application of external loads linked to clinical problems or aesthetic treatments. The state of this barrier (intact or damaged) governs its evolution and its answers. Studies of the mechanical behaviour of the human skin have shown that the human skin is a stratified non-homogeneous, anisotropic, non-linear-visco-elastic material which is subjected to a pre-stress in vivo. In addition its properties vary with age, throughout the body and per person. This paper proposes a bi-phasic model within the framework of a general phenomenological thermo-hydro-mechanical and physico-chemical approach of heterogeneous media which incorporates a solid phase with three solid materials (one for each outer layer of the skin) and a fluid phase. In order to write a closed mathematical problem, the field equations that arise from the model are complemented with initial and boundary conditions deduced from experimental tests performed in the laboratory on in vivo human skin on the indentation device developed by the LTDS. Numerical simulations of these indentation tests are proposed and allow the determination of the mechanical properties of the different layers of skin tissues in vivo.
展开▼
