Eamonn Slattery 12313584 1 Abstract— Friction stir welding (FSW) is a solid state joining process that was developed in 1991 by The Welding Institute in the UK. Since its development there have been many more innovations discovered in the process, such as: friction stir spot- welding (FSSW), joining of dissimilar materials and the joining of thin sheets less than 1mm thick. These unique advantages of FSW has seen it become more and more prevalent in manufacturing industries across many disciplines, such as; automotive, aerospace, electronics, railways and robotics. FSW is becoming an advantage in transportation industries as it requires no consumable materials during the fusion process and does not require the materials to be heated above their melting point. Another key feature is that FSW has a low environmental impact due to the simple method and no requirement for additional heat input. These are key advantages to consider in an assembly line, as transportation manufacturers try to reduce the CO2 emissions from their vehicles and manufacturing processes. The objective of this research was to develop a novel spot welding method of two dissimilar materials, namely Aluminium 6082-T6 and Carbon Fibre-Reinforced Thermoplastic Polymer Polyetheretherketone (PEEK). Several spot welding tool designs were created using research of state-of-the-art friction stir welding processes. The designs were then fabricated and tested on unreinforced PEEK polymer. One design was successful in joining the 6082-T6 to PEEK and was then used to test the joining of 6082-T6 to Carbon Fibre Reinforced PEEK. The tool design was successful in the joining of 6082 to CF/PEEK, two materials that are among the strongest in their class. The tool is a 15mm pinless FSW tool and produces spot joints in a process called friction lap spot joining (FLSJ). Tensile shear tests were carried out on the successful joints and a qualitative analysis was carried out against the current state-of- the-art. Friction Lap Spot Joining has shown joint strengths higher than the current state-of-the-art and has strong potential for further development. Index Terms— Friction Lap Spot Joining / Friction Stir Welding / Composite / Hybrid joints / Friction Spot Welding / Aluminium / Final Year Project / MAI I. INTRODUCTION T his paper investigates the friction spot welding process of Aluminium to PEEK polymer with 40% weight carbon fibre reinforcement. The aluminium chosen was 6082-T6, a lightweight general-purpose alloy that is found in many automobile and aircraft chassis’. The CFRTP chosen was Toho Tenax carbon fibre in a PEEK polymer matrix, a high- performance thermoplastic composite that is used in applications requiring high stiffness and extremely light weight. This configuration was chosen for several reasons. Firstly, both materials are commonly found in applications requiring a high stiffness to weight ratio. This leads to a high likelihood that the two materials will interface in future automotive, aerospace and rail applications. There are many examples of CFRTP and Aluminium interacting in cutting edge applications such as: the grill opening reinforcement of the Shelby GT350, the fuselage clips of the Airbus A350 XWB and the Kawasaki efWing locomotive bogie. Despite being three different vehicle applications, these examples are related in that they are at the cutting edge of lightweight design in their fields. Whereas CFRP was until recently only affordable in unique cases requiring extremely high stiffness to weight ratios[1], it is becoming more and more affordable as major aerospace and automotive manufacturers introduce it into their designs and develop manufacturing processes capable of meeting a high demand. To manufacture high numbers, manufacturers are using thermoplastic based carbon fibre reinforced thermoplastics (CFRTP) with a thermoplastic polymer such as PEEK, PEI, PA or PPS. This thermoplastic composite is ideal for mass production as it can be manufactured in an automated thermoforming process. Traditional epoxy based CFRP require careful layering of carbon fibre weave, impregnated with epoxy, around a mould until the desired thickness is achieved. It would then be cured in an autoclave until it sets. This complicated process is both time consuming and requires high dexterity, therefore it is traditionally performed manually by skilled workers. Thermoplastic composites, however are ideal for mass production as they are formable at elevated temperatures from Friction Lap Spot Joining of Aluminium Alloy 6082-T6 to Carbon Fibre-Reinforced Polyetheretherketone (April 2017) E. Slattery, MAI (Mechanical Engineering)