Prediction of yield and long-term failure of oriented polypropylene: Kinetics and anisotropy

Polymer products are often manufactured by injection molding in which the molten material is subjected to shear and elongational flow, inducing a degree of orientation

Tim B. van Erp; Chris T. Reynolds; Ton Peijs; Johannes A. W. van Dommelen; Leon E. Govaert

2009

Scholarcy highlights

  • Polymer products are often manufactured by injection molding in which the molten material is subjected to shear and elongational flow, inducing a degree of orientation
  • The present study is focussed on the deformation kinetics of oriented polypropylene tapes and a viscoplastic model is proposed to predict the off-axis yield and failure behavior
  • An isotactic polypropylene tape is extruded and subsequent solid state drawing is performed at a drawing temperature of 120◦C producing different tapes with draw ratios of λ = 1, 4 and 6
  • The model is developed such that the anisotropy is decoupled from the deformation kinetics
  • A failure criterion is adopted which states that the product of the time and strain rate at failure is constant for any stress
  • The presented anisotropic viscoplastic model is based on factorization of the strain rate and draw ratio dependence and is capable of quantitatively predicting the strain rate, angle and draw ratio dependence of the yield stress as well as time-tofailure in various off-axis static loading conditions characterized solely of the transverse direction

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