Computational analysis of injection-molding residual-stress development in direct-adhesion polymer-to-metal hybrid body-in-white components

To overcome some of the main limitations of the current polymer metal hybrid (PMH) technologies, a new approach, the so-called “direct-adhesion” PMH process, has been recently proposed [Grujicic, M., Sellappan, V., Arakere, G., Seyr, N., Erdmann, M., in press. Computational feasibility analysis of direct-adhesion polymer-to-metal hybrid technology for load-bearing body-in-white structural components, J. Mater. Process. Technol.]. Within this approach, the necessary level of polymer-to-metal mechanical interconnectivity is attained through the use of polymer-to-metal adhesion promoters. Such promoters are applied to the metal stamping prior to their placement into the injection mold for plastic-subcomponent injection molding. The resulting enhanced polymer-to-metal adhesion affects the way injected plastic develops residual stresses while it is cooled from the plastic-melt temperature down to room temperature. In the present work, injection-molding mold-filling and material-packing analyses are combined with a structural analysis involving polymer/metal adhesion analysis to assess the extent of residual stresses and warping in a prototypical direct-adhesion PMH component. The magnitude and the distribution of such stresses and distortions are critical for the component assembly, performance and durability. The results obtained show that adhesion at the metal-stamping/plastics-subcomponent interfaces, whose presence is the bases for the direct-adhesion PMH technology, has a profound effect on the distribution and magnitude of residual stresses/distortions in the PMH component and that it must be taken into account when the component and its manufacturing processes are being designed.