Hybrid Friction Stir Joining/Channeling of Dissimilar Metal-polymer Joints

Cristina Andreia da Silva Penas

Key information

Authors:

Cristina Andreia da Silva Penas (Cristina Andreia da Silva Penas)

Supervisors:

Arménio Neves Correia (Arménio Neves Correia); Virgínia Isabel Monteiro Nabais Infante (Virgínia Isabel Monteiro Nabais Infante)

Published in

June 30, 2025

Abstract

The advancement of dissimilar metal-polymer joining technologies has played a crucial role in the advancement of lightweight structures, particularly in the aeronautical sector. This evolution, aligned with the pursuit of climate neutrality, has encouraged the adoption of novel materials and design strategies. Among existing joining configurations, overlap joints are commonly employed in metal-polymer assemblies, primarily due to the limitations of conventional welding, mechanical fastening, and adhesive bonding. However, this configuration often suffers from misaligned neutral axes between the joined materials, leading to secondary bending moments and associated bending stresses that limit their loading capacity. To overcome these issues, this study explores a buttstrap configuration for friction stir joining two AA6082-T6 aluminum plates and a NORYLTMGFN2 glass fiber-reinforced polymer plate. This alternative aims to minimize bending issues by aligning the materials’ neutral axes. An iterative exploratory approach was adopted, resulting in the successful production of dissimilar joints. A total of nine joints were fabricated and tested, showing a maximum ultimate tensile strength (UTS) of 138.9MPa (8431.6±582.7N) with a corresponding joint efficiency of 47.9% of aluminum’s UTS. Microstructural analysis revealed a characteristic interface defect resembling a combination of a hook-shaped defect and an unwelded root defect, common in overlap and butt joints, respectively, ultimately reducing the effective joining thickness among aluminum plates and impacting mechanical performance. Additionally, preliminary friction stir channeling trials confirmed the feasibility of simultaneously joining and integrating internal channels, demonstrating promising multifunctionality for lightweight components, paving the way towards the development of integrated structures in next-generation aeronautical applications.