Numerical simulation of the effect of fiber content on residual stresses in fiber reinforced injection molding

The injection process of notched plate with short-fiber-reinforced(SFR) polyamide composites was simulated by commercial software Moldflow. The five different elements in the proximity of the notch were studied to attain fiber orientation and stress distribution at ejection through the thickness, and the effects of fiber content and mold shape change on residual stresses in fiber reinforced injection molding were in-depth analyzed. Results show that with increase of the fiber content, the fibers interaction coefficient Ci decreases; larger values for Ci, tend to make the fiber orientation close to a random in-plane distribution whereas lower values predict a clear alignment in the flow direction; Ci also affects the thickness of the core and shell layers, decreasing the core and increasing the shell thickness as Ci is increased. As the fiber content increases, the magnitude of the coolant pressure and the residual stresses of the part through the thickness at ejection increase; fiber orientation and stress distribution are also affected by the cross-sectional shape change in the proximity of the notch.