Fibre Orientation Mechanisms for Injection Molding of Long Fibre Composites

Abstract

The development of skin/core fibre orientations in injection molded fibre reinforced compounds is considered, and the applicability of the Tadmor fountain-flow mold filling mechanism to long fibre reinforced is investigated. A disc and plaque mold cavity are used to consider the influence of each injection molding cycle parameter upon the skin/core structure. The influence of the flow path length is also considered. The independent orientation controlling mechanisms identified (the injection speed, melt temperature and the holding pressure cycle all of which influence the fibre orientation favourably) can be used in combination to achieve a optimised microstructure for the cavities under study.

Evaluation of wood fiber composites based on a novel simultaneous defibration and compounding process

“…The increase of polymer near the surface is formed by the mold filling mechanism and the flow pattern during injection‐molding in a manner of a fountain flow . During injection molding three microstructural regions are formed: a core, a shear zone, and a skin . All these regions are created by different shear rates .…”

Injection moulding of long glass fiber reinforced polyamide 66: Processing conditions/microstructure/flexural properties relationship

“…Even if a multilayered structure is kept, an increase of the core layer thickness with increasing fiber length is observed, thus suggesting a different mechanism. 6,18,19 Bijserbosch and Gaymans 18 have noticed for example a long fiber orientation mechanism similar to that observed for short fibers, which depend on the flow behavior of the polymer melt during the filling and packing stages on the injection process with a great influence on the gate geometry. During the filling stage, some fiber accumulations that limit the reinforcement efficiency have also been revealed for both long and short fibers.…”

Analysis of injection molding for computer cooling fans by Taguchi method and grey relational analysis

“…Blane et al [13] has studied fiber array in injection molding strengthened thermoset plastics and found that with low injection flow, the fiber forms a quite thick core area in the cavity through-thickness (about 5-6% of half the cavity thickness). Bailey and Rzepka [14] have conducted disk and cavity experiments to study fiber structure in the surface/core layer of a cavity and found that low injection speed, high pressure, low mold temperature, and short fiber can result in quite a thin core area (about 5% of half the cavity thickness), and the fiber in the flow front is arrayed in a parabola because of the fountain flow effect.…”

“…4. Length of fiber: Bailey and Rzepka [14] stated that, based on research, the differences in fiber length may cause different effects of fiber rolling. Since a long fiber is confined on the coplanar, it needs a comparatively greater force to roll; however, the short fiber is easier to move and roll.…”