Effect of Friction in the Punch-to-Specimen Contact Zone Upon the Punching Behaviour of Synthetic Leathers

Abstract

Upholstery materials during their performance experience biaxial deformations, which are effected by friction in the contact zones: material-to-human skin, material-to-material, and material-to-inner parts of the furniture. The aim of this research was to define the effect of friction in the punch-to-specimen contact zone upon the tearing character and strength of non-perforated and perforated synthetic leathers under biaxial punching. Tests were performed with three different punches. The variation of friction coefficients in the punch-to-leather contact zone was achieved by the application of four different lubricants. Leather samples were investigated on the face (vinyl) and reverse (textile) sides. The results of the investigations confirmed that the maximal punching force Pmax increases with an increase in the punch size. The same tendency is valid in cases where different levels of friction act in the punch-to-specimen contact zone or whether the specimens were punched from both sides. Dependencies exist between area S of the punch-to-specimen contact zone during tearing and the average static μSA and dynamic μDA friction coefficients.