Shear Flow Properties of Semiconcentrated Fiber Suspensions with Uniform Fiber Orientation

BARBOSA, SILVIA ELENA; BIBBO, MIGUEL A

JOURNAL OF APPLIED POLYMER SCIENCE

Wiley

Año: 1991 vol. 49 p. 127 - 139

0021-8995

The transient rheological properties of fiber suspensions, viscosity and normal stress differences, are measured in start-up of steady shear flow using a parallel-plate geometry starting with a sample with uniform (deltafunction) fiber orientation distribution. The fluids used in the suspension are Newtonian liquids. The fibers are rigid, cylindrical and monodisperse. There are n fibers each of length L per unit volume. The results are compared against those obtained on samples with initial random fiber orientation distribution. Semi-concentrated fiber suspensions with uniform fiber orientation distribution are obtained using a high voltage source (12000 V) inside of the flow test geometry. This technique is based on the orientation of dielectric particles in an electric field. There is an important difference between the transient rheological response of suspensions with initial uniform and random fiber orientation distribution. This difference is more pronounced in the normal stress. The transient behavior of these material functions is well described by the constitutive equation proposed by Dinh and Armstrong. The experimental results have shown that the transient rheological properties of the suspension can be used to determine the fiber orientation in the composite. The transient first normal stress coefficient difference is the property to be measured in order to determine whether the suspension has a random fiber orientation or not.are n fibers each of length L per unit volume. The results are compared against those obtained on samples with initial random fiber orientation distribution. Semi-concentrated fiber suspensions with uniform fiber orientation distribution are obtained using a high voltage source (12000 V) inside of the flow test geometry. This technique is based on the orientation of dielectric particles in an electric field. There is an important difference between the transient rheological response of suspensions with initial uniform and random fiber orientation distribution. This difference is more pronounced in the normal stress. The transient behavior of these material functions is well described by the constitutive equation proposed by Dinh and Armstrong. The experimental results have shown that the transient rheological properties of the suspension can be used to determine the fiber orientation in the composite. The transient first normal stress coefficient difference is the property to be measured in order to determine whether the suspension has a random fiber orientation or not.