  The mechanical properties of skin are important for a number of applications
including surgery, dermatology, impact biomechanics and forensic science. In
this study we have investigated the influence of location and orientation on
the deformation characteristics of 56 samples of excised human skin. Uniaxial
tensile tests were carried out at a strain rate of 0.012s$^{-1}$ on skin from
the back. Digital Image Correlation was used for 2D strain measurement and a
histological examination of the dermis was also performed. The mean ultimate
tensile strength (UTS) was 21.6$\pm$8.4MPa, the mean failure strain 54$\pm$17%,
the mean initial slope 1.18$\pm$0.88MPa, the mean elastic modulus
83.3$\pm$34.9MPa and the mean strain energy was 3.6$\pm$1.6MJ/m$^3$. A
multivariate analysis of variance has shown that these mechanical properties of
skin are dependent upon the orientation of Langer lines (P$<$0.0001-P=0.046).
The location of specimens on the back was also found to have a significant
effect on the UTS (P =0.0002), the elastic modulus (P=0.001) and the strain
energy (P=0.0052). The histological investigation concluded that there is a
definite correlation between the orientation of Langer Lines and the preferred
orientation of collagen fibres in the dermis (P$<$0.001). The data obtained in
this study will provide essential information for those wishing to model the
skin using a structural constitutive model.
