Fiber Orientation Morphological Layers in Injection Molded Long Fiber Reinforced Thermoplastics

Abstract

Flow-induced fiber orientation can vary significantly across the thickness of injection molded parts and is usually present in the form of through-thickness layers. In this work, fiber orientation was examined both on the flow plane and through the thickness. The thickness of a shell layer with fiber orientation in the flow direction and a core layer with a fiber orientation mainly transverse to the flow were measured via microscopy. The effect of filling speed and mold thickness on the molded plaque morphology was identified. Mold-filling simulations were undertaken in order to provide the characteristic shell and core layer fiber orientations as well as the frozen layer thickness at the end of filling and the gap-wise shear rate gradients. The combined frozen and high shear rate regions were correlated with the experimental shell layer thicknesses.

Keywords

long-fiber-reinforced thermoplastics injection molding fiber orientation morphological layers shell/core morphology

References

1. Matsuoka, T. 1995. "Fiber Orientation Prediction in Injection Molding," Polypropylene, Structure, Blends and Composites, Vol. 3: Composites, J. Karger-Koscis , ed., Chapman and Hall, 3:113-141.

2. Gupta, M. and K. K. Wang . 1993. "Fiber Orientation and Mechanical Properties of Short-Fiber Reinforced Injection Molded Composites," Polymer Composites, 14:367-382.

3. Altan, M. C. , S. Subbiah , S. I. Guqeri and R. B. Pipes . 1990. "Numerical Prediction of Three Dimensional Fiber Orientation in Hele-Shaw Flows," Polymer Engineering and Science, 30:848-859.

4. Bay, R. S. and C. L. Tucker . 1992. "Fiber Orientation in Simple Injection Moldings I: Theory and Numerical Methods," Polymer Composites, 13:317-330.

5. Bay, R. S. and C. L. Tucker . 1992. "Fiber Orientation in Simple Injection Moldings II: Experimental Results," Polymer Composites, 13:332-341.

6. Bright, P. F. and M. W. Darlington . 1981. "Factors Influencing Fiber Orientation and Mechanical Properties in Fiber Reinforced Thermoplastic Injection Moldings," Plastics and Rubber Processing and Applications, 1:139-147.

7. Darlington, M. W. and A. C. Smith . 1987. "Some Features of the Injection Molding of Short Fiber Reinforced Composites in Center Sprue-Gated Cavities,"' Polymer Composites, 8:16-21.

8. Folgar, F. and C. L. Tucker . 1984. Journal of Reinforced Plastics and Composites, 3:98-103.

9. Halpin, J. 1969. "Stiffness and Expansion Estimates for Oriented Short Fiber Composites," Journal of Composite Materials, 3:732-734.

10.

10. Sanschagrin, B. , M. Thiery and B. Fisa . 'A Study of Long Glass Fiber Orientation in Reinforced Injection Molded Parts," 46th Annual Conference of the Composites Institute, SPI.

11.

11. Hieber, C. A. and S. F. Chen . 1978. "Flow Analysis of the Non-Isothermal Two-Dimensional Filling Process in Injection Molding," Israel Journal of Technology, 16:248-254.

12.

12. Hieber, C. A. and S. F. Chen . 1980. 'A Finite Element/Finite-Difference Simulation of the Injection Molding Filling Process," Journal of Non-Newtonian Fluid Mechanics, 7:1-32.

13.

13. Shanker, R. , J. W. Gillespie Jr. and S. I. Guqeri . 1991. "On the Effect of Nonhomogeneous Flow Fields on the Orientation Distribution and Rheology of Fiber Suspensions," Polymer Engineering and Science, 31:161-171.

14.

14. Crochet, M. J. , F. Dupret and V. Verleye . 1994. "Injection Molding" from Flow and Rheology in Polymer Composites Manufacturing, S. G. Advani , ed.