Viscoelastic stress calculation in multi-layer coextrusion dies: Die design and extensional viscosity effects on the onset of 'wave' interfacial instabilities

Abstract

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 TNSD sign criterion can be used to investigate the role of the die design and elongation viscosities of coextruded materials from the point of view of interfacial instability.