Development of hybrid friction stir welding and adhesive bonding single lap joints in aluminium alloys

Ricardo Maciel,Pedro Moreira,Virginia Infante,Daniel Braga,Tiago Bento,Lucas Da Silva

doi:10.3221/igf-esis.48.28

Abstract

Aircraft have been manufactured for decades using a wide variety of welding and joining techniques. There have been signiﬁcant developments in techniques over the last 15–20 years. In civil aeronautical industry the main materials used for the fuselage and structural parts are aluminium alloys. In order to reduce weight, leading to a better fuel and economic efficiency, there is the need to find innovative solutions to join aluminium components in a single lap joint (SLJ) configuration with higher strength to weight ratio than riveting and fastening. In this work, a combination of the friction stir welding (FSW) and adhesive bonding (AB) processes is presented. Quasi-static mechanical properties, fatigue behaviour and other properties of the friction stir weld-bonding joints were assessed and compared with adhesive only and friction stir welded only joints. The development of this new joining technology, the combination of FSW with AB, forming friction stir weld-bonding, aims to incorporate properties and characteristics of both joining technologies, as well as improving damage tolerance. The present research involved the production of two types of overlap joints - FSW and hybrid friction stir weld-bonding. The main objective of this study is to compare the different joining technologies in lap joint conﬁguration and evaluate the inﬂuence of different parameters on the mechanical behavior of the joints. The hybrid joints present better overall results, and the best joint was efﬁciency achieved with the hybrid joint produced with 450 kgf. The average efﬁciency value in this case was 73.75%, however in a particular specimen it reached the value of 85.21%. From the results it is possible to afﬁrm that the hybridization process confers an improvement between 20-30 % in most cases.

Highlights

A combination of regulatory requirements [1] and market demand [2, 3] have pushed for continuous improvements in energy efficiency and performance in transport solutions
The aeronautical industry has been shy of welding processes in primary structures due to the related loss of mechanical properties from large heat inputs, weld quality control and the impossibility of welding precipitated hardened alloys (e.g. AA2024 aluminum alloy), in which cracks tend to form from the arc welding process
In all the welds manufactured this defect was quite significant and that is a result of the pin shearing effect but mainly due to the relatively high welding speed, 20 cm/min, which increases the pin cavity volume per tool rotation, which stimulates the downward flow to fill that gap. Both defects mentioned above result in thinning of the single lap joint (SLJ) joints and degradation of mechanical performance because they result in stress concentration areas

Summary

Introduction

A combination of regulatory requirements [1] and market demand [2, 3] have pushed for continuous improvements in energy efficiency and performance in transport solutions. The aeronautical industry has been shy of welding processes in primary structures due to the related loss of mechanical properties from large heat inputs, weld quality control (process reliability) and the impossibility of welding precipitated hardened alloys (e.g. AA2024 aluminum alloy), in which cracks tend to form from the arc welding process. Friction stir welding has shown to produce sound quality, high performing joints making it the most appealing welding technology for aeronautical structures [4]. In its most basic form, FSW is performed with a tool composed of shoulder and pin, fractioning and mixing the material to weld. The shoulder is mainly responsible for providing heat from friction on to the sheets or plates to be welded, while the pin’s main job is mixing the materials to be joined

Objectives

Results

Conclusion