Test MethodUse of digital image correlation to measure large-strain tensile properties of ductile thermoplastics

This paper presents an experimental investigation of the mechanical behaviour of a talc and elastomer modified polypropylene compound subjected to large strains. 3D digital image correlation with two cameras and stereo-vision was used to determine full-field displacements during uniaxial tensile tests on specimens with rectangular cross-section. Local strains were derived from the displacement field and used to calculate the current cross-sectional area of the specimen during the whole loading process. Points on the true stress-strain curve (Cauchy stress versus logarithmic strain) were then calculated from the data. Volume dilatation was separated into elastic and plastic parts through tests where the specimens were unloaded after varying degree of stretching. The unloading events were also used to investigate damage evolution as function of plastic straining.