Evaluation and Comparison of the Mechanical Performance of Adhesively Bonded and Self-Piercing Riveted Aluminum Joints Under Tension Loading

Abstract

Vehicle weight reduction and fuel efficiency can be improved using multi-material structures incorporating high-performance materials such as aluminum, ultra-high-strength steel, and carbon fibre reinforced polymer composites. Critical to enabling the adoption of aluminum alloys in lightweight multi-material structures are robust joining methods that play a key role in structural performance; crashworthiness; durability; and noise, vibration and harshness. Recent studies have investigated the mechanical performance parameters (i.e. strength, stiffness and energy absorption) of joints created using adhesive bonding and self-piercing riveting (SPR). However, a number of questions regarding the implications of sheet thickness selection on the mechanical performance parameters of adhesively bonded and SPR aluminum joints subjected to tension loading remain to be addressed in order to improve the mechanical performance of joined structures and maximize weight reduction opportunities. In the present study, experimental testing of adhesively bonded and SPR aluminum joints under tension loading was investigated to evaluate the mechanical performance parameters of individual joining methods across a range of typical aluminum alloy sheet thicknesses used in transportation structures (1, 2 and 3 mm). The experimental results showed that increasing sheet metal thickness significantly improved joint strength and stiffness response in both adhesively bonded and SPR joints owing to reduced compliance of the joint. While adhesively bonded joints provided up to 20.5% higher joint strength and up to 421% higher stiffness response, SPR joints achieved up to 353% higher energy absorption. In adhesively bonded joints, energy absorption increased almost linearly with sheet thickness; however, SPR joints demonstrated an optimum energy absorption for a particular sheet thickness.