Multifactorial Mechanical Properties Study on Rat Skin at Intermediate Strain Rates - Using Orthogonal Experimental Design

Most of the skin injuries caused by traffic accidents, sports, falls, etc. are in the intermediate strain rate range (1-100s^-1), and the injuries may occur at different sites, impact velocities, and orientations.

To investigate the multifactorial mechanical properties of rat skin at intermediate strain rates, a three-factor, three-level experimental protocol was established using the standard orthogonal table L₉(3⁴), which includes site (upper dorsal, lower dorsal, and ventral side), strain rate (1s^-1, 10s^-1, and 100 s^-1), and sampling orientation (0°, 45°, and 90° relative to the spine). Uniaxial tensile tests were performed on rat skin samples according to the protocol to obtain stress-stretch ratio curves. Failure strain energy was selected as the index, and the influence of each factor on these indexes, the differences between levels of each factor, and the influence of errors on the results were quantified by analysis of variance (ANOVA).

The results show that the site factor has the greatest influence on the skin’s mechanical properties within the intermediate strain rate range, followed by the strain rate factor, and the sampling orientation factor has the least influence. The mechanical properties of the lower dorsal and ventral skin differ significantly, but there is no apparent difference in the mechanical properties between the upper dorsal and ventral skin. As the strain rate increases, the failure strain energy of the skin increases significantly. There are no significant differences in the mechanical properties of skin samples in the three sampling orientations.