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T. Koch, R. Lach, S. Seidler:
"Influence of the Specimen Geometry on the Essential Work of Fracture of Polypropylene Materials";
Poster: 5th Intern. Conf. on Fracture of Polymers, Composites and Adhesives, Les Diablerets; 2008-09-07 - 2008-09-11; in: "5th Intern. Conf. on Fracture of Polymers, Composites and Adhesives", European Structural Integrity Society, Les Diablerets (2008).

Essential Work of Fracture (EWF) is a suitable method to characterize toughness behaviour of thin specimens and therefore it should be very recommendable for the description of very small amounts of material which is only available during the first stages of material development. Goal of the work is to find the possibility to a further reduction of the specimen dimensions. The first step is to investigate the thickness dependence of essential work and non-essential work of fracture. Results in the literature are controversially discussed.

Different polypropylene materials were used for those investigations, because in semicrystalline polymers besides the specimen dimensions the morphology parameters play an important role. Specimens with thicknesses of 1, 0.5, 0.3, 0.2 and 0.1 mm were produced by compression moulding. The morphology was checked by DSC, WAXS and optical microscopy to ensure that it is similar for all thicknesses. The deformation behaviour of the DDENT specimens during the EWF test follows the requirements of ESIS TC4.

For the investigated materials the EWF values were independent of thickness although the morphology was identical in the specimens.

Besides the influence of thickness the role of several morphological and molecular parameters will be shown for selected thicknesses.

Essential Work of Fracture (EWF) is a suitable method to characterize toughness behaviour of thin specimens and therefore it should be very recommendable for the description of very small amounts of material which is only available during the first stages of material development. Goal of the work is to find the possibility to a further reduction of the specimen dimensions. The first step is to investigate the thickness dependence of essential work and non-essential work of fracture. Results in the literature are controversially discussed.

Different polypropylene materials were used for those investigations, because in semicrystalline polymers besides the specimen dimensions the morphology parameters play an important role. Specimens with thicknesses of 1, 0.5, 0.3, 0.2 and 0.1 mm were produced by compression moulding. The morphology was checked by DSC, WAXS and optical microscopy to ensure that it is similar for all thicknesses. The deformation behaviour of the DDENT specimens during the EWF test follows the requirements of ESIS TC4.

For the investigated materials the EWF values were independent of thickness although the morphology was identical in the specimens.

Besides the influence of thickness the role of several morphological and molecular parameters will be shown for selected thicknesses.

essential work of fracture, geometry, polypropylene, morphology

Project Head Thomas Koch:
Size effects of near plane-strain fracture parameters of polypropylene thin films with different molecular weight, tacticity and crystalline structure using the essential-work-of-fracture approach