Research on residual stresses of injection molded PC parts

Residual stresses in injection molded parts may have negative effects on optical and mechanical properties. It is usually two types residual stresses in the injection molded parts - flow-induced and thermally-induced stresses. In this paper, thermal residual stresses are investigated by comparing tensile properties of the injection molded PC parts before and after annealing. A dielectrostrictive sensor is developed to conduct the flow-induced stress analysis during filling stage. The physical meaning of obtained dielectrostriction signals is given based on the experimental and numerical results. First the pressure measured by the transducers was compared with the numerical simulated results. These two values agree well, which indicates that the numerical prediction should also be reliable for shear stress analysis. Then the shear stress calculated based on the measured dielectrostriction signal was compared with its corresponding numerical result. And it has been found that the difference between these two values within 5% at the various processing condition.