Quantification of local in-plane displacements of paper by means of a new measuring system

Against the background of studies of the runnability of paper a new method for the measurement of local in-plane displacements of paper during and aft er a tensile test is reported in this paper The measuring system is used in the context of fracture mechanics of paper: The measured displacements are used to calculate strain fields of paper: Strain fields are determined in the area of double edge notches at tensile specimens, which simulate flaws. By means of the measuring system the elastic and plastic proportions of th e local strains can be quantified. The effect of the flaw geometry on strai n fields is demonstrated by variation of the notch length. The results reve al that the strains within 5 mm around the crack tips are significantly lar ger than the average strain of the specimens when strained ciose to the ten sile strength.