High-temperature large strain viscoelastic behavior of polypropylene modeled using an inhomogeneously strained network

• Published in: Journal of applied polymer science Vol. 72; no. 4; pp. 563 - 575
• Main Authors: Sweeney, J., Collins, T. L. D., Coates, P. D., Duckett, R. A.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 25-04-1999; Wiley
• Subjects: Applied sciences; constitutive equation; Exact sciences and technology; finite element; large deformation; necking; Organic polymers; Physicochemistry of polymers; polypropylene; Properties and characterization; Structure, morphology and analysis; Hot deformation; Constitutive equation; Finite element method; Tensile stress; Stress strain relation; Propylene polymer; Necking; Uniaxial strain; Numerical simulation; Experimental study; Modeling; Elongation (mechanics)
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/(SICI)1097-4628(19990425)72:4<563::AID-APP13>3.0.CO;2-#

The effects of microstructural rearrangements during the stretching of semicrystalline polymers and the resultant inhomogeneous strains are modeled by rigid spheres embedded in a polymer network. This results in strain concentrations in the network, which is then caused to yield at realistic overall strains. To simulate the collapse of the original spherulitic morphology, the radii of the spheres decrease at a rate dependent on the shear stress imposed on them by the surrounding network. This results in time‐dependent behavior. The resultant large strain viscoelastic model is implemented in a commercial finite element code and used to predict shapes of necking polypropylene sheet specimens at 150°C. Rate dependence of stress and stress relaxation are also predicted, and the model is shown to be generally effective in its predictions of shapes and forces up to large deformations. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 563–575, 1999