The determination of the fracture parameters for polymers in impact

A method of analysis is given by which the critical strain energy release rate G_c for impact tests may be deduced for both Charpy and Izod tests from normal energy measurements. Suitable calibration factors are determined and the method is applied to a range of polymers. Very close agreement is achieved between the Charpy and Izod results except for highly ductile materials for which it was necessary to use a fully plastic analysis. The method is extended to blunt notches and it is shown that the use of a strain energy per unit volume to yielding, together with a blunt notch stress analysis, gives a good description of the results.