The rheology and mold flow of polyester sheet molding compound

L. J. Lee*, L. F. Marker, R. M. Griffith

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

57 Scopus citations


Flow properties of sheet molding compounds (SMC) were measured by several rhemeters. Shear viscosities of SMC paste can be fitted by the Carreau viscosity equation and reduced to a single master curve by plotting the reduced shear viscosity (η/η0) against reduced shear rate (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} η0/T). The deformation fo glass filled compounds under extensional forces. When the shear forced was applied, the compound defomed like a deck of cards being slid. It behaved essentially like a laminate of many layers. On the other hand, SMC compounds elongated much less before sample failure occurred under the extensional flow. The extensional viscosity was much higher than the shear viscosity. This phenomenon was explained by a solid composite theory and theories developed from local shear flows between adjacent fibers. The flow of SMC compounds during molding showed that the surface layers flowed further than the inner layers when the mold surfaces were hot. This casued inner plies to show through at the surface and resulting in some wavy glass orientation. This phenomenon was explained equalitatively by a heat penetration model.

Original languageEnglish
Pages (from-to)209-218
Number of pages10
JournalPolymer Composites
Issue number4
StatePublished - Oct 1981


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