Technology of Rivet: Adhesive Joints

Abstract

In general hybrid bonding allows to match together the properties of two different joining techniques, with the aim to obtain a joint with a better set of properties (that could involve strength, energy absorption at failure, cost, etc.) with respect to the simple joints. In the literature, several works dealing with the evaluation of the strength for this kind of joints and a global enhancement of the properties, in terms of static strength, fatigue strength and energy absorption are found. The first hybrid technique “discovered” was the weld bonding and therefore in the literature it is the most deeply analyzed. In terms of mechanical performance, weld-bonding is the hybrid joining technique where better result are obtained with respect to other hybrid joining techniques such as rivet bonding, clinch bonding, etc., but at the same time it is the most troublesome in terms of joint manufacturing (influence of the presence of the adhesive on the welding performance, weld compliant adhesive requirements, etc.). On the opposite, the hybrid techniques which combine adhesive with mechanical fastening (like rivet, clinching, self piercing riveting) give in general a lower enhancement of performance if compared with weld bonded joint, but certainly they are characterized by an easier and trouble less manufacturing. In this chapter, a brief introduction to the rivet bonding technology is given, dealing with why the hybrid joints are useful and which kind of industrial requirements this kind of joints are able to satisfy. Later on, the adhesive requirements are discussed with the aim to find the best adhesive for different purposes. One of the most important benefits of the rivet bonded joints is the ease of manufacture, therefore the way to produce rivet bonded joints is discussed, and a literature example is shown with the aim to emphasize the different manufacture procedure of rivet bonded joints when compared with traditional weld bonding techniques. In this case, a noticeable benefit in terms of manufacture cost is also shown with respect to traditional joining techniques. An example of the evaluation of the strength of rivet bonded joints (pop rivet and self piercing rivet) in comparison with the performances of simple riveted and simple bonded joint, is then given. It is shown how the performance of hybrid joints depend mostly on the strength of the adhesive bond, and that the rivet becomes relevant only when the adhesive performance decreases (i.e. when the service temperature is higher than the adhesive glass transition temperature for example) or in general when the adhesive fails. Finally, the failure mode is discussed for both pop rivet bonded and self piercing rivet bonded joints. The failure of a pop rivet bonded joint is simulated using appropriate damage models for the rivet and for the adhesive. In particular the parameters of the damage models are tuned by comparison with experiments performed on simple joints and they seem to be adequate for the simulation of the failure behaviour of rivet bonded joints.