RESIDUAL-STRESSES IN INJECTION-MOLDED POLYCARBONATE RECTANGULAR BARS

This study deals with the quantification of the residual stress profil es of injection molded rectangular bars with polycarbonate of various molecular weights. Determinations via the layer removal technique indi cated that these bars can possess compressive stress of up to 10 MPa a t 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 que nching experiments, i.e., parabolic, for locations far away from the g ate of the cavity. At locations near the gate of the cavity and for in jection molding at high speed, the residual stress profile changed sig n, going from compressive to tension at the surface and vice versa in the interior. These residual stress profiles were very dependent on ga ting geometry and location.