Irreversible deformation of isotactic polypropylene in the pre-yield regime

[Display omitted] In the modeling of the mechanical response of a polymer over a large strain range, the nonlinear viscoelastic and viscoplastic behavior must be considered. For many polymers, nonlinear behavior is observed at low loads, e.g. by a stress-dependence of the creep compliance for stress...

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Bibliographic Details
Published in:European polymer journal 2011-05, Vol.47 (5), p.989-996
Main Authors: Tscharnuter, D., Jerabek, M., Major, Z., Pinter, G.
Format: Article
Language:English
Subjects:
Applied sciences
Cavitation
Deformation
Exact sciences and technology
Mechanical properties
Nonlinearity
Organic polymers
Physicochemistry of polymers
Plastic deformation
Polypropylene
Polypropylenes
Properties and characterization
Recovery
Strain
Strain recovery
Stress whitening
Viscoplasticity
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Summary:[Display omitted] In the modeling of the mechanical response of a polymer over a large strain range, the nonlinear viscoelastic and viscoplastic behavior must be considered. For many polymers, nonlinear behavior is observed at low loads, e.g. by a stress-dependence of the creep compliance for stresses above 2MPa in case of the polypropylene used in this study. Additionally, plastic deformation has been observed at strains below the yield point for several polymers. In this study, the irreversible deformation by cavitation and shear yielding of polypropylene are characterized in the pre-yield regime in uniaxial tensile tests using digital image correlation. The recovery of strain after unloading at a prescribed strain level is measured and used to identify the evolution of the plastic strain during uniaxial tension. An experimental technique for simultaneous determination of the true stress–true strain curve and the degree of stress whitening, which relates to the amount of cavitation, is introduced and the initiation of cavitation is compared to the plastic deformation detected in strain recovery at various temperatures.
ISSN:0014-3057
1873-1945
DOI:10.1016/j.eurpolymj.2011.03.003