2017 Volume 58 Issue 3 Pages 499-504
Experimental viscosity measurements (50 to 100 Pas at mold walls, T = 273 to 373 K) of an injection-molded highly-filled glass fiber reinforced polyester bulk molding compound (GFRP-BMC) whose fiber length (lfiber = 0.44 mm) was optimized for tensile mechanical strength agreed well with that previously calculated by Navier-Stokes equation from fiber orientation mapping. The mapping was from 0.44 mm fiber formulation molded sample exhibiting ～60, ～40 and 20% higher tensile strength, strain, and modulus, respectively than commercially used (lfiber = 6.4 mm). Based on the viscosity measurements a new “mold filling” model is constructed with physical meaning to predict needed injection molding parameters pressure (dP), shot time (ts) and shot weight (ms) for various size dog-bone specimens varying length (Ltot), gauge length (LB), width (w) and thickness (th) for the optimized formulation. Moreover, the Mooney-Rabinowitsch calculation is found to be a decent predictor for shear rates across specimen thickness and at mold walls measured from the mapping. This was without buying new equipment, using the existing injection molding machine to save cost.
