The mechanical properties of injection molded parts in glass reinforced materials is sensitive to processing. A successful design requires a good estimate of performance before production.

The product performance is strongly affected by the fiber orientation field. It is complex and varies tri-dimensionally in the moldings. Some commercial simulation programs already allow the prediction of the fiber orientation induced by the injection flow. However the simulations depend on the definition of the fiber interaction coefficient.

C-Mold simulations were made to determine the best fit to experimental results varying the interaction coefficient between neighboring fibers in center gated circular flat discs.