Calado, Francisco N.Pragana, JoãoBragança, IvoSilva, Carlos M. A.Martins, Paulo A. F.2023-02-132023-02-132021-08Calado, F.N., Pragana, J.P.M., Bragança, I.M.F. et al. Resistance element welding of sandwich laminates with hidden inserts. Int J Adv Manuf Technol 118, 1565–1575 (2022). https://doi.org/10.1007/s00170-021-08063-6http://hdl.handle.net/10400.21/15563This paper presents a new resistance element welding process capable of producing invisible lap joints between steel-polymer-steel composite laminates. The process involves pre-drilling a flat-bottom hole in each laminate to remove the polymer core and one of the steel sheets, and positioning a cylindrical insert inside the two adjoining holes for subsequent resistance welding. Finite element modeling is utilized to construct the weldability lobe and to identify the parameters that lead to the formation of acceptable joints. Experimental results confirm the applicability of the process to produce invisible lap joints without signs of material protrusions or local indentations resulting from squeezing the polymer out to create contact between the steel sheets. Destructive peel and shear tests allow determining the maximum forces that the joints can safely withstand and comparing their performance against alternative joined by forming lap joints in which the mechanical interlocking is also hidden inside the laminates.engResistance element weldingResistance element weldingComposite laminatesLap jointsWeldabilityFinite element methodExperimentationjournal article10.1007/s00170-021-08063-6