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Stress oscillation in amorphous copolyesters due to tensile impact
Author(s) -
KargerKocsis J.,
Czigány T.,
Moskala E. J.
Publication year - 1999
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.11531
Subject(s) - necking , materials science , differential scanning calorimetry , amorphous solid , copolyester , composite material , crystallization , oscillation (cell signaling) , glass transition , stress (linguistics) , ultimate tensile strength , polymer , crystallography , thermodynamics , philosophy , biology , polyester , linguistics , chemistry , physics , genetics
Specimens from amorphous copolyester (aCOP) sheets of different composition and molecular mass characteristics were subjected to instrumented tensile impact loading in the speed range of 2 – 3.7 m/s at ambient temperature. Stress oscillation was observed in the necking phase, especially for the aCOP with smaller entanglement density. It was found that the appearance of stress oscillation is limited to a given frequency or strain rate range (estimated by the ratio of the incident speed and clamped specimen length). Necking occurred by cold drawing which was evidenced by the shape recovery of the broken specimens when heated above the glass transition temperature (T g ≈ 90°C). According to polarized light microscopy and differential scanning calorimetry (DSC), the stress oscillation was generated by diffuse shear banding without crystallization. This is the first report according to the authors' knowledge on the stress oscillation phenomenon in amorphous polymers in which crystallization was not involved.