The multi-factor effects study on mechanical properties of rat skin using orthogonal experimental design

Skin is highly susceptible to damage and laceration in various scenarios such as traffic accidents, sports or daily falls. These injuries can occur at anywhere on the body, in any direction, and at varying stretching speeds, making skin a kind of material influenced by multiple factors. To obtain a comprehensive understanding of the mechanical properties of skin across the entire body, a multi-factor effects study was conducted using Rats. An experiment design utilizing an orthogonal table was established, incorporating three pivotal factors: Site, Strain Rate, and Sampling Orientation, each with multiple levels to explore their respective impacts. Skin samples collected from four different anatomical locations, with each location being sampled in three directions, were tested using uniaxial tensile test at three different stretching speeds to obtain stress-strain curves. From these curves, key mechanical indices were derived, including ultimate stress, ultimate strain, failure strain energy, and elastic modulus, were acquired from the curves as the indices. By utilizing Analysis of Variance with these four parameters as indices, the sum of squares of deviations was calculated, and this enabled the precise quantification of each factor's contribution rate to the indices, the variability among the levels within each factor, and the impact of errors on the experimental results. The results indicate that the site factor has the greatest impact on the mechanical properties of rat skin, followed by the Strain rate factor, and then the Sampling orientation factor. Specifically, their integrated contribution rates are 59.00 %, 27.88 %, and 1.93 %, respectively.