Laser Dissimilar Joining of Al7075T6 with Glass-Fiber-Reinforced Polyamide Composite

Dissimilar joining between metal and composite sheets is usually carried out by mechanical or adhesive joining. Laser dissimilar joining between metal and composite sheets could be an alternative to these methods, as it is a cost-effective and versatile joining technique. Previously, textured metallic and composite parts have been held together and heated with a laser beam while pressure is applied to allow the melted polymer to flow into the cavities of the metal part. The main issue of this process relates to reaching the same joint strength repetitively with appropriate process parameters. In this work, both initial texturing and laser joining parameters are studied for Al 7075-T6 and glass-fiber-reinforced PA6 composite. A groove-based geometry was studied in terms of depth-to-width aspect ratio to find an optimal surface using a nanosecond fiber laser for texturing. Laser joining parameters were also studied with different combinations of surface temperature, heating strategy, pressure, and laser feed rate. The results are relatively good for grooves with aspect ratios from 0.94 to 4.15, with the widths of the grooves being the most critical factor. In terms of joining parameters, surface reference temperature was found to be the most influential parameter. Underheating does not allow correct material flow in textured cavities, while overheating also causes high dispersion in the resulting shear strength. When optimal parameters are applied using correct textures, shear strength values over 26 kN are reached, with a contact area of 35 × 45 mm2.This research was funded by the Basque Government grant number KK-2017/00088

Influence of temperature and clamping force on the strength of the joint over different composite-metal combinations joined by laser

Vehicle weight in automobile industry is a strict limitation which can be overcome with novel material combinations. Laser conduction joining is an arising alternative but it still poses challenges for joining dissimilar metal-composite materials. Up to now, main research lines have been developed using constant process parameters (laser power and clamping force), so, the behavior of these composite-metal joints under different process parameters, and the control of the process itself, are unknown areas of investigation so far. This paper is focused on the implementation of closed-loop control systems for temperature and clamping force. Tests at different set-points have been carried out for different composite-metal combinations, and the strength of the joints has been assessed by single lap shear tests. The optimal joining process parameters have been found for each material combination.The research leading to these results has received funding from the European Union’s Horizon 2020 programme under grant agreement Nº 677625 within FlexHyJoin Project