Friction Stir Welding (FSW) is a solid-state joining technique that has gained widespread adoption, particularly for aluminum alloys, due to its ability to produce high-quality welds without melting base materials. This comprehensive review focuses on the influence of process parameters on weld characteristics and performance. Compared to conventional fusion welding methods, FSW offers notable advantages, including superior mechanical properties, fewer defects, enhanced corrosion resistance, and lower environmental impact. The review also addresses key challenges such as tool wear, precise process control, and complications arising from welding dissimilar alloys. By synthesizing recent developments and case studies, this work outlines current limitations and proposes future directions for optimizing the FSW process to expand its applicability in critical engineering sectors.

This study evaluates the influence of rotational speed on the mechanical and microstructural properties of T-joints fabricated via friction stir welding (FSW) using dissimilar aluminum alloys, AA5083 and AA6082, for naval applications. Three types of joints were produced by maintaining a constant traverse speed of 100 mm/min and varying the tool rotational speed at 500, 700, and 900 rpm. Mechanical performance was assessed through pull-out tests and microhardness measurements. The joints fabricated at 500 rpm demonstrated superior mechanical properties, including a more uniform hardness distribution and higher pull-out strength, attributed to optimized material mixing and heat input at this speed. In contrast, higher rotational speeds led to defect formation, such as wormholes, and compromised mechanical performance. These findings underscore the importance of optimizing rotational speed to enhance joint quality, making FSW a viable solution for manufacturing durable, lightweight structures in demanding marine environments.

The objective of this research is to optimize additive manufacturing processes, specifically Fused Filament Fabrication (FFF) techniques, to produce sandwich structures. Mono-material specimens made of polylactic acid (PLA) were produced, where both the skin and core were fabricated in a single print. To optimize the process, variations were made in both the base cell geometry of the core (Tri-Hexagon and Gyroid) and the core infill (5%, 25%, 50%, and 75%), evaluating their effects on static three-point bending behavior. Optical microscopy was employed to assess both the structure generated by additive manufacturing and the fracture modes. The findings reveal that increasing the infill, and thus the core density, enhances the mechanical properties of the structure, although the improvement is such that samples with 50% infill already demonstrate excellent performance. The difference between hexagonal and Gyroid structures is not significant. Based on microscopic analyses, it is believed that the evolution of 3D printers, from open to closed chamber designs, could significantly improve the deposition of the various layers.

This research investigates the optimization of 3D-printed sandwich structures fabricated using fused filament fabrication (FFF) with polylactic acid (PLA) and PLA reinforced with flax fibers. The core of the sandwich structure features a gyroid infill pattern, which is known for its mechanical efficiency. The study delves into the effects of deposition temperature on the adhesion between the core and skin layers, as well as the impact of infill density on the overall mechanical properties. Three-point bending tests are conducted to assess the flexural performance of the structures. The objective is to identify the optimal processing parameters to enhance the performance of PLA-based composite sandwich structures. Potential applications for these structures include lightweight components for automotive interiors, sustainable packaging solutions, and architectural elements requiring a balance of strength and environmental sustainability.