More on the rheological behavior of collimated fiber thermoplastic composite materials Conference Paper uri icon

abstract

  • Sheet forming of metallic materials is one of the most pervasive manufacturing methods in contemporary manufacturing technology. The development of its counterpart in thermoplastic composite materials has been the subject of numerous recent studies. Although continuous fiber composites possess a direction of inextensibility in the fiber direction, extensibility in the fiber direction can be provided by introducing breaks along the fiber length so that individual fibers are made discontinuous. This technology, along with the introduction of thermoplastic polymer matrices, offers the potential to develop manufacturing methods for these new composite materials that can take advantage of lower cost conventional manufacturing methods. Since the sheet forming of these thermoplastic matrix composites requires the melting and flow of highly anisotropic materials, the ability to predict the effective viscosities of anisotropic thermoplastic sheet materials should prove valuable. The object of the present work is to describe the flow characteristics of fiber-reinforced thermoplastic composites at the melt temperature of the polymer. Previously, relations were developed which predict the primary anisotropic viscosities (η11, η22, η12, and η23) for a suspension consisting of collimated, discontinuous fibers suspended in a Newtonian matrix fluid. The shearing viscosities (η) of many polymeric fluids, however, exhibit Newtonian behavior at low strain rates followed by power-law behavior for increasing strain rates. Therefore, the existing relations were extended to include non-Newtonian behavior by incorporating a power-law and a Carreau constitutive relation for the matrix fluid viscosity. These updated models are compared to experimentally obtained values for the elongational and shearing viscosities of a polypropylene/glass fiber suspension.

author list (cited authors)

  • Pipes, R. B., Coffin, D. W., Creasy, T. S., Shuler, S. F., & Simacek, P.

publication date

  • December 1992