Analysis of the Joining Mechanisms in Friction Lap Welding of AA5052/PP using Numerical and Experimental Techniques

Abstract

Friction Lap Welding (FLW) presents a viable and eco-friendly solution for joining lap joints. However, the successful implementation of FLW with hybrid metal-polymer lap joints poses challenges arising from the inherent property differences between metals and polymers. This thesis addresses challenges in the friction lap welding of Aluminum alloy 5052 (AA5052) and Polypropylene (PP) for achieving efficient and reliable joints. The lack of chemical bonding between these materials necessitates the exploration of alternative joining mechanisms, particularly mechanical interlocking, and to achieve this, surface texturing is applied to the Aluminum surface. The objective of this research is to analyze joining mechanisms and enhance the understanding of temperature distribution and its impact on the AA5052-PP interface during FLW. A numerical model is developed and validated to predict the temperature at the interface, providing valuable insights into process optimization. Experimental data on temperatures, forces, and power are utilized to validate the numerical model and establish correlations with process parameters.

To gain further insights into the joining mechanisms, the joint undergoes thermal and chemical characterization using techniques such as thermogravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The experimental results demonstrate the significance of temperature control in achieving optimal mechanical interlocking efficiency.

The findings reveal that interfacial temperatures within the range of 156°C to 316°C yield the best welding temperature range, with appropriate PP flow and interlocking. Below 130°C, insufficient PP flow leads to poor joint formation, while temperatures above 316°C result in over-melting of PP and potential issues such as increased tool plunging force and bubble formation. Among the investigated temperature levels, a temperature distribution of 130-190°C at the cross-section of the PP exhibits superior tensile results, with a maximum load of 1.433 kN and elongation of 52.24%.

This research contributes to the understanding of FLW of AA5052 and PP by addressing the challenges associated with their dissimilar nature. The developed numerical model and experimental investigations provide valuable insights into temperature control and mechanical interlocking optimization. These findings can guide future research and practical applications in joining dissimilar materials, particularly in industries where Aluminum alloys and PP combinations are of interest.

Date of Award	Aug 2023
Original language	American English
Supervisor	Fahad Almaskari (Supervisor)