Experimental Study On Cyclic Deformation Of Animal's Skin

Due to the importance in clinical and cosmetic applications, the mechanical properties of skin have been extensively studied by many researchers through experimental and histology methods. Some experiments focused on the tensile, creep, and stress relaxation properties of the skin and their influencing factors. However, few studies concerned the cyclic deformation behavior of skin tissue. Some researchers explained the failure of skin through the variation of tissue structure. However, the change of skin tissue structure during the cyclic deformation has not been investigated in details. Therefore, the cyclic deformation of skin tissue and relative variation in microscopic tissue structure are observed in this work by using the skins of pig and snake. The contents are given as follows:1. Macroscopic observations to the monotonic tensile, creep, stress relaxation and cyclic deformation properties of pig's and snake's skins. The effects of loading rate, direction, and level on the mechanical behaviors of the skins are also addressed.2. Microscopic observations to the changes of tissue structure during the tension, compression, creep, stress relaxation and cyclic deformation by cryotomy technique and optical microscopy method.Based on the mechanical testing and microscopic structure observation, it can be concluded that:1. The complicated mechanical properties of the skins are related with complex tissue structure;2. Skin exhibits obvious ratchetting in the asymmetrical cyclic stressing;3. Skin presents obvious anisotropy during the tension, creep, stress relaxation and ratchetting deformations due to different amount and size of collagen fibers in different loading direction.4. Collagen fiber will move in the direction of applied load, but the movement needs external force and time. Thus, skin exhibits obvious viscous effect, which is observed during the creep, stress relaxation and time dependent ratchetting tests.