Fabrication of welded hybrid joints of aluminum alloys and polymer composites with significantly enhanced long-term reliability

High‐performance composite structures and effective joining processes are important for shipbuilding, and aerospace sectors to perform better in challenging situations. The importance of this study is to analyze the effect of glass powder‐modified adhesive and joining techniques such as co‐curing (CC), co‐bonding (CB), and secondary bonding (SB) on flexural, shear, and free vibrational characteristics such as natural frequency and damping factor for glass fiber‐reinforced polymer (GFRP) composites. Results revealed that, compared to SB and CB composite joints, 1 wt.% glass powder‐modified CC composite single lap joints (SLJ) enhanced the shear properties by 103.04% and 111.74%, respectively, due to rougher surface formation in the adhesive layer. As a result, it enhanced the fiber's adhesion to the matrix. On the other hand, CC bonded joints with 1 wt.% of glass powder exhibited the highest flexural strength (85.99 Mpa). The experimental free vibrational analysis showed that 1 wt.% glass powder CC composite had a high natural frequency, whereas higher wt.% glass powder increased the damping properties due to the matrix and fiber interaction. The current research reveals that CC technique with 1 wt.% of glass powder provided a significant improvement to the adhesively bonded composite's mechanical and free vibrational characteristics. Highlights Four distinct wt.% of glass powder were used to prepare the glass powder‐modified adhesive by sonication. SLJ glass fiber‐reinforced polymer composite joints were fabricated through CC, CB, and SB techniques Maximum shear and flexural strength were found at CC SLJ 1 wt.% glass powder. CC SLJ 1 wt.% glass powder enhanced better vibrational behavior. Failure surface analysis was conducted using FE‐SEM images.

Combination of nano-particle deposition system and friction stir spot welding for fabrication of carbon/aluminum metal matrix composite joints of dissimilar aluminum alloys

Stress corrosion cracking is one of the major issues for welded joints of 6005A-T6 aluminum alloy in high-speed trains. High residual stress in the welded joints under corrosion results in stress corrosion cracking. Ultrasonic impact treatment was used to control the residual stress of the welded joints of 6005A-T6 aluminum alloy. Experimental tests show that ultrasonic impact treatment can induce compressive longitudinal and transverse residual stress in the welded joint, harden the surface, and increase the tensile strength of welded joints. Salt-fog corrosion tests were conducted for both an as-welded sample and an ultrasonic impact-treated sample. The surface of the treated sample had far fewer corrosion pits than that of the untreated sample. The treated sample has higher strength and lower tensile residual stress than the untreated sample during corrosion. Therefore, ultrasonic impact treatment is an effective technique to improve the stress corrosion cracking resistance of the welded joints of 6005A-T6 aluminum alloy.

Recent developments in local concepts of fatigue assessment of welded joints

The application of low-energy methods of metal inert gas welding (ColdArc and CMT) for the manufacture of joints in hard-weldable aluminium alloys is presented. The purpose of the technological research was to show the usefulness of the CMT and ColdArc methods for production of butt and T-joints in 2.0 mm thick aluminium alloy plates. Basic difficulties related to welding of 6xxx and 2xxx series aluminium alloys and the specificity of welding by low-energy methods are discussed. Selected results of metallographic macro- and microscopic examination as well as those of tensile and bend tests are given; detailed analysis of the results is also carried out. The article shows also that ColdArc and CMT methods provide high quality and aesthetic welded joints in aluminium alloys that are considered to be non-weldable or of limited weldability.

High-fidelity prediction of forming quality for self-piercing riveted joints in aluminum alloy based on machine learning

AA2014 aluminum alloy (Al-Cu alloy) has been widely utilized in fabrication of lightweight structures like aircraft structures, demanding high strength to weight ratio and good corrosion resistance. The fusion welding of these alloys will lead to solidification problems such as hot cracking. Friction stir welding is a new solid state welding process, in which the material being welded does not melt and recast. Lot of research works have been carried out by many researchers to optimize process parameters and establish empirical relationships to predict tensile strength of friction stir welded butt joints of aluminum alloys. However, very few investigations have been carried out on friction stir welded lap joints of aluminum alloys. Hence, in this investigation, an attempt has been made to optimize friction stir lap welding (FSLW) parameters to attain maximum tensile strength using statistical tools such as design of experiment (DoE), analysis of variance (ANOVA), response graph and contour plots. By this method, it is found that maximum tensile shear fracture load of 12.76 kN can be achieved if a joint is made using tool rotational speed of 900 rpm, welding speed of 110 mm/min, tool shoulder diameter of 12 mm and tool tilt angle of 1.5°.

Material properties of friction stir spot welded joints of dissimilar aluminum alloys

Joining light metals with polymer composites through metal overcasting

Forming process prediction of a self-piercing riveted joint in carbon fibre reinforced composites and aluminium alloy based on deep learning

(1987). Examining the possibilities of using ultrasonic inspection for detecting oxide films in welded joints in aluminium alloys. Welding International: Vol. 1, No. 11, pp. 1064-1067.

(1992). Physical microheterogeneity of welded joints in aluminium alloys and nucleation of corrosion‐mechanical defects. Welding International: Vol. 6, No. 8, pp. 640-642.

Innovative welding processes are continuously gaining industrial interest. Both hybrid laser welding (HLW) and friction stir welding (FSW) are automated welding processes which allow achieving high quality joints in aluminum alloys, in combination with a high productivity. It is important to assess the capability of the processes, not only in terms of weld quality but also in terms of productivity and profitability. The EN AW-6056 alloy is a recent high strength weldable AlMgSiCu alloy, which is utilised in aviation. This alloy, with a thickness of 2,5 mm, was subjected to HLW and FSW. The optimisation procedure which was used for HLW to assess the most appropriate welding parameters will be discussed in detail. A comparison is made between the mechanical properties in the as-welded and in the T78 post-weld heat treatment (PWHT) temper. Fatigue testing of unnotched welded specimens with a ratio of maximum stress to minimum stress equal to 0,1 was applied to this alloy in the PWHT condition. Results obtained with both welding techniques are compared and discussed in this paper.

Friction stir welded (FSWed) joints of aluminum alloys exhibited a hardness drop in both the advancing side (AS) and retreating side (RS) of the thermo-mechanically affected zone (TMAZ) due to the thermal cycle involved in the FSW process. In this investigation, an attempt has been made to overcome this problem by post weld heat treatment (PWHT) methods. FSW butt (FSWB) joints of Al-Cu (AA2014-T6) alloy were PWHT by two methods such as simple artificial aging (AA) and solution treatment followed by artificial aging (STA). Of these two treatments, STA was found to be more beneficial than the simple aging treatment to improve the tensile properties of the FSW joints of AA2014 aluminum alloy.

(1990). Effect of reinforcement on fatigue strength of butt welded joints in aluminium alloy. Welding International: Vol. 4, No. 7, pp. 509-514.