Extensional and shearing flow of a glass-mat-reinforced thermoplastics (GMT) material as a non-Newtonian viscous fluid

The isothermal squeezing flow of glass-mat-reinforced thermoplastics (GMT) has previously been confirmed to behave anisotropically, and a transversely isotropic Newtonian fluid model was applied to fit the experimental data. The model was used to calculate the extensional viscosities, and was compar ed to the viscosity calculated from an isotropic model, showing a differenc e up to 20% between the two models. In this work the GMT squeezing flow has been modelled as a transversely isotropic power-law fluid. The equations o f motion were solved for the three power law viscosity parameters, which we re found from the geometrical shape of the elliptically deformed specimens, the applied force and the strain rates in the three directions. Good agree ment between the experimental applied stress and the predicted curves from the model was achieved. The influence of shear on the compression moulding was also investigated with a special model being developed for the case of non-lubricated mould-plate surfaces. An expression for the shear force at t he walls has been derived. The GMT compression moulding was modelled as a c ombination of extensional and shearing flows. Non-Newtonian anisotropic ext ensional and shear viscosities were determined for the GMT isothermal compr ession moulding. (C) 1999 Elsevier Science Ltd. All rights reserved.