Lasers Manuf. Mater. Process. (2017) 4:136–151 DOI 10.1007/s40516-017-0042-2 A Modeling Approach for Plastic-Metal Laser Direct Joining Adrian H. A. Lutey 1 · Alessandro Fortunato 2 · Alessandro Ascari 2 · Luca Romoli 1 Accepted: 29 August 2017 / Published online: 7 September 2017 © Springer Science+Business Media, LLC 2017 Abstract Laser processing has been identified as a feasible approach to direct join- ing of metal and plastic components without the need for adhesives or mechanical fasteners. The present work sees development of a modeling approach for conduction and transmission laser direct joining of these materials based on multi-layer optical propagation theory and numerical heat flow simulation. The scope of this methodol- ogy is to predict process outcomes based on the calculated joint interface and upper surface temperatures. Three representative cases are considered for model verifica- tion, including conduction joining of PBT and aluminum alloy, transmission joining of optically transparent PET and stainless steel, and transmission joining of semi- transparent PA 66 and stainless steel. Conduction direct laser joining experiments are performed on black PBT and 6082 anticorodal aluminum alloy, achieving shear loads of over 2000 N with specimens of 2 mm thickness and 25 mm width. Compar- ison with simulation results shows that consistently high strength is achieved where the peak interface temperature is above the plastic degradation temperature. Compar- ison of transmission joining simulations and published experimental results confirms these findings and highlights the influence of plastic layer optical absorption on process feasibility. Keywords Numerical modeling · Laser direct joining · Plastic-metal joining · Dissimilar materials · Optical propagation  Adrian H. A. Lutey adrian.lutey@unipr.it 1 Dipartimento di Ingegneria e Architettura, Universit` a degli Studi di Parma, Parco Area delle Scienze, 181/A, Parma, Italy 2 Dipartimento di Ingegneria Industriale, Universit` a di Bologna, viale Risorgimento, 2, Bologna, Italy