| Abstract: | Geometry independent fracture mechanics values – Requierenent for toughness characterization of polymers Starting from the history of introducing the Charpy test to the characterization of plastics, polymer‐specific requirements for the specimen geometry relevant for the determination of fracture mechanics parameters of plastics are summarized. Here, the influence of the specimen thickness, the specimen configuration and size, and a/W‐ratio are considered. In order to characterize the geometry independence of fracture mechanics parameters, in this connection, geometrical factors are used to estimate requirements for the specimen geometry without an experimental determination of the geometry influence. For plastics, these experimentally determined factors vary in a wide range. For this reason, the use of constant geometrical factors must cause a pronounced under‐ or overevaluation of the requirements on the specimens. The relationships between the geometrical factors and the fracture mechanics parameters those are universally valid for plastics are independent from the kind of loading (static, dynamic) and the crack propagation behaviour (stable, unstable). |
