Further exploration of through hole extrusion welding applied to aluminum to polymer joints
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Insinööritieteiden korkeakoulu |
Master's thesis
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Authors
Date
2022-01-24
Department
Major/Subject
Mechanical Engineering
Mcode
Degree programme
Master's Programme in Mechanical Engineering (MEC)
Language
en
Pages
103
Series
Abstract
Dissimilar joining of lightweight metal alloys to structural polymer-based materials is a major challenge demanding research and innovation of new feasible and reliable manufacturing solutions. These joints will open new possibilities in the design of optimized structural performance, with the aim of reaching modern targets of greenhouse gas emission reduction, clean energy production, and creation of high-performance, lightweight structures. Through-hole extrusion welding (THEW) is one such solution. THEW is a friction stir-based processing technique which is being explored in the production of continuous linear joints between aluminium alloy AA5754 and polyether ether ketone (PEEK). The materials are joined with the addition of an integral titanium extrusion die, allowing the formation of a hook-like structure of aluminum in polymer. Mechanical interlocking and adhesive bonding form the primary joining mechanisms of THEW. In this study, a set of 16 overlap joints between AA5754-H111 and PEEK were produced and analyzed for process stability, tensile-shear strength, and microstructure. Four tools with different probe geometries, and four positions relative to the extrusion die, enable an investigation of the technological effects relevant to the THEW process. Four tensile-shear specimens are extracted from each joint to increase the statistical relevance of the results. The cross-section from the most relevant THEW joint is chosen for macro- and microstructural analysis, via optical microscopy. A maximum tensile-shear load of 160 kN/m is achieved at 2.5 mm extension. Shorter probe geometries and a bias toward the flow side of the extrusion slot are shown to improve the strength of joints in steady state operation. Careful balancing of heat input and polymer mobility is essential to the formation of high-performing THEW joints. The process is deemed to be stable, with clear avenues of improvement suggested for future research.Description
Supervisor
Vilaça, PedroThesis advisor
Khadka, PrabilsonKeywords
through-hole extrusion welding, THEW, metal-polymer joint, joining of dissimilar materials, AA5754-H111, PEEK