Even though friction stir welding (FSW) has been shown to produce high performing butt joints, stress concentration at the weld edges in overlap FSW significantly reduces the performance of these joints. By combining FSW and adhesive bonding into a friction stir (FS) weld bonding, joint mechanical performance is greatly improved. Quasistatic and fatigue strength of the proposed FS weld‐bonding joints was assessed and benchmarked against overlap FSW and adhesive bonding. The characterization of the structural adhesive is also presented, including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), as well as mechanical characterization with curing temperature. A small process parameter study was made to select proper FSW parameters for AA6082‐T6 overlap FSW and FS weld‐bonded joints. FS weld bonding achieved a significant increase in quasistatic and fatigue strength when compared with overlap FSW, with 79.9% of the fatigue strength of adhesive‐bonded joints at 106 cycles, whereas FSW had 41.6%.
The need for weight reduction and leaner manufacturing and assembly processes in aircraft construction has led to the pursuit of welding technologies. One such technology that has been considered for this application is friction stir welding (FSW). Since it is a solid‐state joining method, it creates high performing joints in a wide range of materials while avoiding overlap lengths and added weight from fasteners, crack stoppers, doublers, etc. However, the adoption of this technology to the assembly of large fuselage shell components is challenging, due to geometric tolerance management requirements. In this paper, a hybrid joining method is proposed for such application, involving FSW and adhesive bonding. Fatigue performance of single lap joints of AA2024‐T3 Al‐Mg‐Cu alloy was assessed and benchmarked against FSW overlap and adhesive bonded joints. Significant strength and ductility increase was achieved through the hybridization of the overlap FSW joints. Fatigue strength of the hybrid joints was also higher than FSW overlap joints, although not as high as adhesive bonded joints.
Aeronautical structures have been assembled for decades using a wide variety of welding and joining techniques. Over the last 15-20 years significant developments in joining techniques have occurred. Aluminium alloys have been the main traditional materials in civil aeronautical industry for the fuselage and structural parts. In order to reduce weight, improving fuel efficiency, there is the need to develop innovative solutions to join aluminium components in a single lap joint (SLJ) configuration with higher strength to weight ratio than riveting and fastening. In this work, a combination of the friction stir welding (FSW) and adhesive bonding (AB) processes is presented. Quasi-static mechanical properties, fatigue behaviour and other properties of the friction stir weld-bonding joints were assessed and compared with adhesive only and friction stir welded only joints. The development of this new joining technology, combining FSW with AB, resulting in friction stir weld-bonding, aims to incorporate properties and characteristics of both joining technologies, as well as improving damage tolerance. The present research involved the production of two types of overlap joints-FSW and hybrid friction stir weld-bonding. The main objective of this study is to compare the different joining technologies in lap joint configuration and evaluate the influence of different parameters on the mechanical behavior of the joints. The hybrid joints present higher strength, ductility and hardness, with the highest joint efficiency achieved in the hybrid joint produced with 450 kgf. These findings lead to the conclusion that-hybridization process confers a joint efficiency improvement between 20-30 % in most cases.
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