Test MethodEffect of precracking method on KIc results for medium-density polyethylene tested under cryogenic condition

The effect of different precracking methods on the results of linear elastic KIc fracture toughness testing with medium-density polyethylene (MDPE) was investigated. Cryogenic conditions were imposed in order to obtain valid KIc values from specimens of suitable size. Most conservative KIc values were obtained by slow pressing a fresh razor blade at the notch root of the specimen. Due to the low deformation level imposed on the crack tip region, the slow pressing razor blade technique also produced less scatter in fracture toughness results. It has been shown that the slow stable crack growth preceding catastrophic brittle failure during KIc tests in MDPE under cryogenic conditions should not be disregarded as it has relevant physical meaning and may affect the fracture toughness results.