Thermographic Characterisation of the Deformation and Fracture Behaviour of Polymers with High Time and Spatial Resolution
The thermo-mechanical coupling of polymers describes the dissipative heating during plastic deformation, which again changes the local molecular mobility. It was investigated at the example of poly(ethylene terephthalate) (PET) and polycarbonate (PC). Depending on the sample geometry certain amount of stored elastic energy is available for neck initiation accompanied by local heating of the sample. In case of the semicrystalline PET temperature jumps until and above the glass transition temperature (T g) can be observed, meanwhile the temperature increase at yield is significant below T g for PC. At crack initiation and fracture a further increase of the temperature is detectable for both materials, for PET close to the melting temperature of the crystalline phase and for PC above T g. The discussion of polymer yielding and fracture with respect to preceding temperature changes casts a new light on relevant molecular processes.
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