Requirements on the Specimen Geometry to Determine Intrinsic Fracture Mechanics Values of Polymer Materials

ABSTRACT: Specific requirements on the specimen geometry necessary for the determi-nation of fracture mechanics parameters for polymers by using the instrumented Charpy impact test are summarized. As examples, the influences of the specimen thickness and a/W ratio are considered. For characterizing the geometry independence of fracture mechanics parameters, geometrical factors are used, which make possible an estimation of the re-quirements on the specimen geometry without any further experiments. For polymers, the experimentally determined geometrical factors vary in a wide range; this means that the use of constant geometrical factors must cause a pronounced under- or overevaluation of the requirements on the specimens. The relationships between geometrical factors and fracture mechanics parameters, which were found to be generally valid for polymers, are independent of the kind of loading (static, impact-like) and the crack propagation behav-iour (stable, unstable). BASIC REMARKS The geometry dependence of fracture mechanics parameters in terms of B, a and (W–a) is characterized independently of the fracture mechanics concep