Abstract

The viscoelastic properties obtained from tensile stress-strain curves on leather and a number of poromerics are compared. It is found that a unique correlation exists for all shoe upper materials between the energy input to a stress-strain cycle and the hysteresis in that cycle. The amount of tension-set at a particular strain for leather is larger than for the poromerics and this gives leather an enhanced comfort property. The paper shows how this initial set is related to the amount of stress softening (difference between first and subsequent extension curves) in the material. The change of tension set with time of recovery, after extension to a particular strain, is shown to be similar for leather and poromerics.