Additive manufacturing of surface structured metal parts for high strength lightweight injection overmolded polymer-metal hybrid joints

Polymer-metal hybrid structures (PMH) are increasingly used in the automotive and aerospace industries for lightweight applications. In this study, we investigate the integration of emerging additive manufacturing with injection overmolding to produce high-strength lightweight hybrid joints. AlSi10Mg substrates, with and without submillimeter-sized mushroom-shaped surface structures, were additively manufactured using laser powder bed fusion (L-PBF), followed by injection overmolding (IOM) with polycarbonate (PC). Overlap joints with structured metal substrates demonstrated remarkable joining strength (20.5 ± 3.8 MPa), primarily attributed to the micro-mechanical interlocking between the consolidated polymer and the metal surface structure. Fracture analysis revealed two primary modes of cohesive failure (stretching and shear) in the mushroom-shaped structures, contingent on their location on the metal surface. This behavior was attributed to a combination of interfacial shear stress and secondary bending, as elucidated by digital image correlation (DIC) analysis. The fatigue life of hybrid joints was determined to be 38 % of the joining strength at 10⁶ cycles, indicating excellent mechanical performance and high potential for engineering applications.