Friction Stir Spot Welding of Aluminium Alloy AA5052 With and Without Carbon Fiber-reinforced Polymer Composite Interlayer

In this dissertation, similar aluminum alloys AA5052 with additional carbon fiber reinforced polymer composite (CFRP) interlayer were selected to investigate the effect of welding parameters (rotational speed and dwell time) on the mechanical properties, joint efficiency, and microstructure of friction stir spot weld joint. The maximum tensile shear load was 1779.6 N with joint efficiency of 14.6% obtained at rotational speed of 2,000 rpm and 2 s dwell time, which is 39.5% higher than the value at low rotational speed 850 rpm and 2 s dwell time whereas the joints without interlayer the maximum tensile shear load was 2439 N with joint efficiency of 19.4% obtained at 1300 rpm and 2 s dwell time, which is 48% higher than the value at low rotational speed 850 rpm and 5 s dwell time. Meanwhile, the maximum microhardness 58 HV was attained in the keyhole region at rotational speed of 2,000 rpm and dwell time of 5 s, which is 22.4% higher compared to low rotational speed. On the other hand the specimens without carbon fiber interlayer, the maximum microhardness was 37.2 HV was obtained at 850 rpm and 2 second dwell time in thermal mechanical affect zone, which is about 51% higher compared to low rotational speed. The SEM-EDS results reveal the presence of intermetallic compounds (Al–Mg–C), which enhance the intermetallic bonding between elements. The microstructure without interlayer images showed that welding parameters such as rotational speed and dwell time have high effect on hook deformation and penetration around the pin area. It was proposed a novel prediction model to predict tensile shear load of samples with and with CFRP interlayer by applying various machine learning models i.e. artificial neural network (ANN), Adopted neuro fuzzy-inference system (ANFIS), support vector machine (SVM) and multi linear regression (MLR). According to test results, it has an incentive effect for future studies to know that MLR model produce better results to estimate tensile shear load in both cases of with and without additional interlayer rather than the other model and the average error was just 0.333% and 3.64 % respectively.