Friction stir welding (FSW) has emerged as a solid-state joining technique offering notable advantages over traditional welding methods. Gas metal arc welding (GMAW), a fusion-based process, remains widely used due to its high efficiency, productivity, weld quality, and ease of automation. To combine the benefits of both techniques, a hybrid welding approach integrating GMAW and FSW has been developed. This study investigates the impact of this hybrid technique on the joint quality and properties of AA5083-H111 and AA6082-T6 aluminum alloys. Butt joints were produced on 6 mm thick plates, with variations in friction process parameters. Characterization included macro- and microstructural analyses, mechanical testing (hardness and tensile strength), and corrosion resistance evaluation through stress corrosion cracking tests. Results showed that FSW significantly refined and homogenized the microstructure in both alloys. AA5083-H111 welds achieved a joint efficiency of 99%, while AA6082-T6 reached 66.7%, differences attributed to their distinct strengthening mechanisms and the thermal–mechanical effects of FSW. To assess hydrogen-related behavior, slow strain rate tensile (SSRT) tests were conducted in both inert and hydrogen-rich environments. Hydrogen content was measured in arc, friction, and overlap zones, revealing variations depending on the alloy and microstructure. Despite these differences, both alloys exhibited negligible hydrogen embrittlement. In conclusion, the GMAW–FSW hybrid process successfully produced sound joints with good mechanical and corrosion resistance performance in both aluminum alloys. The findings demonstrate the potential of hybrid welding as a viable method for enhancing weld quality and performance in applications involving dissimilar aluminum alloys.

Understanding the deterioration and predominant damage mechanisms of structures is highly relevant, especially for safety-critical components. Non-Destructive Testing (NDT) plays a crucial role in assessing and monitoring their integrity by evaluating damage evolution. However, when it comes to complex structures, the existing NDT methods face challenges in their application, as is the case with sandwich structures. This study employs two NDT methods to analyze the initiation of damage in such structures during a fatigue test. The Acoustic Emission (AE) technique utilizes membrane-free microphones with a broad bandwidth to capture acoustic events from difficult-to-access areas. A machine learning algorithm is used to classify these events to determine their source and associated damage mechanisms. Additionally, Digital Image Correlation (DIC) is employed to measure strain evolution without contact during the test. This method is particularly relevant due to the complex and thin geometry of sandwich structures, where other methods are not applicable. Strain redistributions are considered relevant damage indicators. The results indicate that Acoustic Emission serves as an early indicator of damage, with the cumulative number of events and peak frequency correlating well with the severity of the damage. In contrast, DIC revealed clear indications of damage or deterioration, albeit at a later stage compared to AE.

Friction stir welding (FSW) has been proposed as an alternative modern joining technology and demonstrated important benefits for the manufacturing of efficient and lightweight aircraft structures using high-strength aluminium alloys. These structures are required to be corrosion- resistant and thus, it is necessary to use technologies such as surface treatments and sealants in their manufacturing and assembly. In this work, the feasibility of combining innovative Cr-free surface treatments, sealants and FSW technology was investigated with the focus on the durability of the joints in fatigue. FSW lap joints were produced using AA2099-T83 extrusions and AA2060-T8E30 sheets in the as-received or surface-treated condition. A sealant was also applied in some cases at the overlapping interface before the FSW process. Static tensile tests and fatigue tests were carried out applying hoop-stress loading conditions. Different fracture modes were identified depending on the stress levels applied in the fatigue tests: High stress levels resulted in fractures in the HAZ of the FSW joints, while the specimens tested at low stress levels showed fractures out of the FSW joint. In general, FSW joints produced using surface-treated aluminium components and sealant presented improved fatigue life and extended durability in comparison with non-treated aluminium joints. The surface treatments and sealant at the interface of AA2099-T83 extrusions and AA2060-T8E30 sheets reduced the friction and local damage produced due to the sliding movement during the fatigue tests, minimizing the fretting fatigue effect, which was found to be the main limiting factor on the durability and fatigue life of the FSW joints.

Hybrid Laminar Flow Control (HLFC) is a promising technology for reducing aircraft drag and, therefore, emissions and fuel consumption. The integration of HLFC systems within the small space of the wing leading edge, together with de-icing and high lift systems, is one of the main challenges of this technology. This challenge can be tackled by using microholes along the outer skin panels to control suction without the need for an internal chamber. However, microperforations modify the mechanical properties of titanium sheets, which bring new challenges in terms of wing manufacturability. These modified properties create uncertainty that must be investigated. The present paper studies the mechanical properties of micro-drilled titanium grade 2 sheets and their modeling using the Finite Element Method (FEM). First, an experimental campaign consisting of tensile and Nakajima tests is conducted. Then, an FEM model is developed to understand the role of the anisotropy in sheet formability. The anisotropy ratios are found by combination of Design of Experiments (DoE) and the Response Surface Method (RSM); these ratios are as follows: 1.050, 1.320, and 0.975 in the directions Y, Z, and XY, respectively. Some mechanical properties are affected by the presence of microholes, especially the elongation and formability that are significantly reduced. The reduction in elongation depends on the orientation: 20% in longitudinal, 17% in diagonal, and 31% in transversal.

Residual stress (RS) in additive manufactured (AM) alloys is a key issue that typically causes damage to printed parts. Hole-drilling and diffraction techniques can estimate the stress level in a comparatively large volume of material; however, it is difficult to relate these results to the microstructural features typical of AM alloys. The newly developed focused ion beam-digital image correlation (FIB-DIC) approach allows RS estimation at a specific location, which helps to understand the nature of RS in relation to microstructure and, as a result, to prevent critical states in the printed material. In the present study, the FIB-DIC approach was applied to estimate RS in an AM AlSi7Mg0.6 alloy produced using the laser powder bed fusion technique. The obtained results were discussed with respect to microstructural observations and compared with finite element modeling and X-ray diffraction analysis. The FIB-DIC RS results were in align with other analytical methods. The strong deviation in RS measurements was associated with RS variations across individual grains. Meantime, it did not reveal differences in RS in the plane transverse to the build direction across the melt pool.

Aircraft heat exchangers play a crucial role in maintaining thermal balance and ensuring that essential components operate efficiently and safely. In this context, it is highly relevant to gain knowledge about the deterioration and the predominant damage mechanisms of these components. In this study, two different non-destructive methods are employed to analyze the damage initiation of a heat exchanger part during fatigue test. On the one hand, Acoustic Emission technique is employed using membrane-free microphones capable of capturing a broad bandwidth. The acoustic events were classified by a machine learning algorithm to determine their source and damage mechanisms. On the other side, Digital Image Correlation (DIC) allowed the measurement of the strain evolution along the test and more precisely, redistributions were considered as damage indicators. As a result, it was identified that AE served as early damage indicator as the cumulative number of events was in good agreement with the severity of the damage. With respect to classification two clear clusters ascribed to different type of events were identified. In the case of DIC, strain redistributions gave clear indications of damage or deterioration but at a later stage compared to AE