Investigation of the deformation and failure of polypropylene under indenters of different shapes

Abstract

In order to study the residual strain distribution in a nontransparent polymer (polypropylene) under identers of various shapes (sphere, cone, cylinder) multilayer colored specimens with a predetermined distribution of the layers were used. By cutting along selected planes it was possible to estimate the residual strains in the interior of the specimen, both qualitatively and quantitatively. By this means we investigated the relations between the reversible and residual strains in polypropylene as a function of the indenter penetration depth and, moreover, the relations between the deformed and failed volumes of polymeric material under indenters of different shapes. It was shown that a change in indenter shape may produce a considerable change (by a factor of 3 or more) in the relations between the penetration, strain propagation, and failure volumes, which should be taken into account both in determining the hardness of polymeric materials by different methods and in selecting the shape of sealing elements.