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Viscoelastic stress calculation in multi‐layer coextrusion dies: Die design and extensional viscosity effects on the onset of ‘wave’ interfacial instabilities
Author(s) -
Zatloukal M.,
Sáha P.,
Vlček J.,
Tzoganakis C.
Publication year - 2002
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.11048
Subject(s) - materials science , viscoelasticity , extensional viscosity , die (integrated circuit) , composite material , instability , constitutive equation , viscosity , stress (linguistics) , strain hardening exponent , finite element method , mechanics , structural engineering , shear viscosity , engineering , linguistics , philosophy , physics , nanotechnology
Non‐isothermal calculation of flow history‐dependent viscoelastic stresses in an annular coextrusion die is performed using the 8‐mode modified Leonov constitutive equation and the deformation rate field from finite element simulations. The study shows how the recently proposed total normal stress difference (TNSD) sign criterion, which quantifies the relative stretching of coextruded layers across an interface, can be used to investigate the role of the die design and elongational viscosities of coextruded materials from the point of view of interfacial instability. It is shown that both the die geometry and the elongational strain hardening have a crucial effect on the interfacial wave instability.