Comparative assessment on weldability of Al 6061 to polycarbonate for dissimilar sheets placement in friction stir lap welding using sensor signals

Abstract

The thermoplastic polymers and precipitation hardened aluminium alloys are highly popular in the aerospace and automobile sectors as a replacement of metallic materials to improve the strength to weight ratio. Thus, the unlike aluminium alloy to polycarbonate assembled structures are often necessary for which mechanical fastening and adhesive bonding are the primary methods for joining as fusion welding processes are inadequate. However, the dissimilar joint efficiency is found to be less. Thus, the ultrasonic and friction welding processes are developed. The friction stir welding is one such advanced material stirring technique without any melting of base materials. The present work addresses metallic aluminium (Al6061) to polycarbonate sheet materials joining using friction stir welding in overlap configuration using tapered H13 tool steel. The thrust force with associated tool stirring torque has been acquired in real time during plunging followed by welding phase. The weld bead profile with respective force-torque signals was analysed for the process monitoring. The tensile test has been carried out on the lap welds. The weld interface of the unlike sheets have also been scrutinised. Initially, the aluminium sheet was partially overlapped on polycarbonate for the parametric study. The highest joint efficiency was found to be 40.2% at 1400 rpm tool rotational speed and 75 mm/min traverse speed due to improper material mixing at the weld interface. Therefore, the feasibility of the process have been tested by placing thermoplastic polycarbonate over aluminium alloy through which the joint efficiency was further improved (48.57%) at comparatively low tool rotational speed (1100 rpm) with lower welding speed (55 mm/min) as the minute metallic particles uniformly mixed with melted and solidified polycarbonate due to more uniform torque in the welding phase. The tool stirring torque and axial thrust was found to be higher in this overlap position.

Monitoring of friction stirred spot weld quality for dissimilar Al6061 to polycarbonate using tool assisted thrust-torque signatures

“…The lower polycarbonate locally melted along the weld interface and expelled towards both sides as well as over the metallic aluminium sheet which was found to be solidified just after welding. 36 This polycarbonate expulsion surrounding the upper metallic sheet was also considered as an inaccuracy in weld quality. The parametric effect on the width of this undesired solidified material expulsion has also been studied.…”

“…The spot welds' interface macrographs that is, the lower surface of metallic aluminium and the upper surface of polycarbonate weld sheets have been examined where sticking phenomenon was noticed in most of the cases rather than any intermetallic bonding. 36,52 The centre point experiment (Expt. #14, N2000-T40-D0.5) has been repeated thrice (Expt.…”

Optimizing the input parameters setting for least hole defects while drilling CFRP laminates by multi-objective optimization on the basis of ratio analysis (MOORA) method

“…Composites are also considered the favorite materials for marine industries due to their high fatigue strength and ability to withstand highly corrosive environments [2]. However, complex structures such as aircraft manufacturing need a near-net-shape component which is almost impossible to make in a single structure [3]. Therefore, they were produced separately and finally assembled by a joining process where riveting has an upper hand as it facilitates repair works that necessitate a hole-making process [4].…”

Application of machine learning approaches to predict joint strength of friction stir welded aluminium alloy 7475 and PPS polymer hybrid joint

“…Polymer and metal hybrid structures have gained considerable interest in the automotive and aerospace sectors. 1,2 Hybrid structures can enhance the product's performance by taking advantage of the different material systems. The inclusion of hybrid structures into the vehicle industry reduces the vehicle weight without sacrificing structural performance.…”

“…Goswami et al 2 analysed the influence of torque on weld quality characteristics of friction stir lap welded AA6061 and polycarbonate sheets using real-time torque sensor signals. The authors stated that smaller metallic particles are uniformly mixed with melted and solidified polycarbonate due to more uniform torque during the welding process.…”