Optische Verformungsmessung an heterogenen Werkstoffsystemen

Zugleich: Dissertation, Universität Kassel, 201

Role of bonding defects in a self-reinforced polypropylene (PURE) under fatigue loading

Self-reinforced plastics are manufactured by producing partly crystallized tapes, weaving fabrics, and hot-pressing of several layers of fabric. As there is no matrix accommodating the reinforcing elements the apes are locally welded to each other during hot-pressing. Upon loading pronounced strain localizations can be found using digital image correlation DIC. The localization occur on a mesoscopic scale near crossing points of the tapes and on microscopic scale between different fabric layers, if there are imperfect bondings of between the tapes. These imperfections are more likely to occur in the center of the specimen as can be visualized using computer tomography. The size and number of the bonding defects can be changed by modifying the parameters during hot pressing and by choosing different numbers of fabric layers. The paper deals with the fatigue behavior of this type of material and the role of the bonding imperfections on the damage accumulation process. For this purpose local deformation fields using DIC determined after quasi- static loading, step-wise increased loading and cyclic loading are compared with each other. These findings are related to the damage pattern observed after final fracture