Fracture Behavior of Polymers at Cryogenic Temperatures
Crack propagation behavior of amorphous polymers, Polycarbonate (PC) and Polymethylmethacrylate (PMMA) has been investigated at 77 K by using Chevron-notched specimens. The deformation rate ranges from 10-8 to 10-4 m/s. For PC a strong, and for PMMA nearly no strain rate dependence of the fracture toughness KIc has been observed. KIc, in addition, is greatly influenced by the environment. For PC, the value of KIc in LN2 is more than twice that in He-gas atmosphere at the same temperature. Also the strain rate dependence is influenced by the environment. It is assumed that for PC the craze formation at the crack tip is enhanced by direct contact with LN2. In addition some data on High Density Polyethylene (HDPE) and Polytetrafluoroethylene (PTFE) at elevated temperatures are given.
KeywordsPlastic Zone Energy Release Rate Crack Opening Displacement Crack Opening Displacement Strain Rate Dependence
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