Residual stresses in injection molded polycarbonate rectangular bars

Abstract

Abstract This study deals with the quantification of the residual stress profiles of injection molded rectangular bars with polycarbonate of various molecular weights. Determinations via the layer removal technique indicated that these bars can possess compressive stress of up to 10 MPa at the surface and up to 9 MPa in tension in the interior. The residual stress profile showed a shape similar to that observed in thermal quenching experiments, i.e., parabolic, for locations far away from the gate of the cavity. At locations near the gate of the cavity and for injection molding at high speed, the residual stress profile changed sign, going from compressive to tension at the surface and vice versa in the interior. These residual stress profiles were very dependent on gating geometry and location.