Abstract:
Adhesive bonding is the process of joining two adherends together with the use of an adhesive. Steel adhesive bonding refers to when steel is one, or both, of the adherends. There is limited knowledge, when compared to other adherends that currently use adhesive bonding in industry, about steel adhesive bonding. The advantage of steel adhesive bonding is that the use of it will widen the current use of steel in structural and mechanical environments. This is due to not limiting the steel to welding or riveting as the only means of bonding, which is particularly relevant for naval use. This project investigates mechanical tests in three adhesive systems, bonding steel to composite fibreglass and the analysis of the failure modes and mechanisms. It was found that the quality of bonding of steel to composites is heavily based on three variables: The preparation of the adherends, the adhesive system used in testing and the environmental conditions the samples are subjected to. From this project, it was determined that the epoxy system was the adhesive system that showed the most consistent results and potential. It was determined that the likely cause of weakness was the BoGel, a commercially available primer for aluminium, on the basis of preliminary testing that showed an increase in bond strength. The methacrylate had slightly lower results compared to the epoxy. The methacrylate however, had voids present at the bonding surface that was determined to reduce strength in testing. This makes the methacrylate system less desirable than the epoxy, but still applicable. The flexible (terostat) had high results with all but shear testing. This was expected for a soft adhesive however, the adhesive displayed a high level bonding indicating it is suitable for specific applications such as impact loading. In summary, the epoxy system is the system best suited for further investigation but the other systems are still comparable. The major flaw for all adhesives was the response to the environmental conditions they were placed in, which caused the majority of change in the failure modes. This is because the environment can drastically alter strengths, in particular of the methacrylate system when subject to both loading and the presence moisture, undergoing sudden failure, in contrast to the results seen in the control.