Abstract
The development of lightweight hybrid metal–polymer structures has recently attracted interest from the transportation industry. Nevertheless, the possibility of joining metals and polymers or composites is still a great challenge. Friction Spot Joining (FSpJ) is a prize-winning friction-based joining technique for metal–polymer hybrid structures. The technology is environment-friendly and comprises very short joining cycles (2 to 8 s). In the current work, aluminum alloy 7075-T6 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) friction spot joints were produced and evaluated for the first time in the literature. The spot joints were investigated in terms of microstructure, mechanical performance under quasi-static loading and failure mechanisms. Macro- and micro-mechanical interlocking were identified as the main bonding mechanism, along with adhesion forces as a result of the reconsolidated polymer layer. Moreover, the influence of the joining force on the mechanical performance of the joints was addressed. Ultimate lap shear forces up to 4068 ± 184 N were achieved in this study. A mixture of adhesive–cohesive failure mode was identified, while cohesive failure was dominant. Finally, a qualitative comparison with other state-of-the-art joining technologies for hybrid structures demonstrated that the friction spot joints eventually exhibit superior/similar strength than/to concurrent technologies and shorter joining times.
Highlights
Interest has grown in the transport industry to use fiber-reinforced polymers aiming at reducing weight and fuel consumption in vehicles [1]
The deformation the deformation aluminumretained into the composite the shape of twoinrings. This geometry provides two sites of macro-mechanical interlocking between the geometry provides two sites of macro-mechanical interlocking between the aluminum and composite, aluminum and composite, thereby maximizing the volume of the composite entrapped into the nub thereby maximizing the volume of the composite entrapped into the nub (84 ± 8 mm )
Signs of fiber and matrix entrapment on the aluminum surface were observed in all cases. These results indicate the importance of the nub geometry and its influence on the macro-mechanical interlocking between the joining parts and the mechanical performance of the friction spot joints
Summary
Interest has grown in the transport industry to use fiber-reinforced polymers aiming at reducing weight and fuel consumption in vehicles [1]. Glass- and carbon-fiber-reinforced polymers present optimal specific strength and stiffness, along with improved corrosion properties when compared with conventional materials such as steel [2]. The manufacturing of monolithic structures is not feasible due to technical and economic concerns [2]. There is a growing trend of combining lightweight metal alloys with advanced fiber-reinforced polymers in the development of metal–polymer hybrid structures. Over the past 30 years, aircraft manufacturers have been increasing the use of polymer composites in their products. Some well-known examples include the Boeing 787 (50% in weight composed of composites) [3], the Airbus A350 (53% in weight composed of composites) [4], and recently, the Embraer
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