Mechanical and failure behaviour of the stratum corneum.

The load-deformation-time behaviour of heat-separated human stratum corneum was investigated using a pure shear specimen geometry. The tissue displayed non-linear load-deformation behaviour and stress relaxation, although the extensibility and amount of stress relaxation was considerably less than that shown by other soft connective tissues. Controlled failure tests were carried out after an edge cut had been made in the pure shear specimen. Sources of secondary failure, either at the free edge of the specimen, or due to the presence of inhomogeneities in the tissues, were common. Analysis of the test results suggested that the fracture surface energy of stratum corneum has a mean value of 3.6 kJ m-2 which is comparable with the tougher synthetic polymers.