Electrically assisted rapid joining of hybrid AA7075–polycarbonate multi-material structures: Process window and joint characterization

Multi-material metal–polymer assemblies are increasingly adopted in lightweight structural applications, yet existing joining technologies suffer from limitations related to energy efficiency, surface alteration, fixturing requirements, or cycle time. In this work, an electrically assisted joining process is proposed for the rapid fabrication of hybrid AA7075 aluminum–polycarbonate (PC) assemblies, combining Joule heating of the metallic substrate with laser-textured micro-interlocks at the coupling interface. A systematic experimental campaign was conducted varying current and heating time, with combined thermal (IR thermography), mechanical (single lap shear), and fractographic characterization. A key finding is that the interface temperature alone is not a sufficient descriptor of joint quality: the electrical input energy E in — rather than peak temperature — governs the process by controlling the time available for viscous polymer flow above the glass transition temperature of PC. Three distinct process regimes were identified as a function of E in : no interlocking, optimal mechanical interlocking with joint strength approaching the load-bearing capacity of the PC substrate, and thermal degradation with bubble formation and increased process scatter. Bubble-induced defects are benign under static loading due to compensation by increasing bonded area, but represent potential fatigue crack nucleation sites under cyclic loading, leading to differentiated optimization criteria for static and dynamic applications. The proposed process requires no consumables, leaves outer substrate surfaces unaltered, and completes the joining cycle in 1–2 s.