Design and ageing of adhesives for structural adhesive bonding – A review

Abstract

This review outlines some of the issues which have to be addressed when selecting an adhesive for a particular structural adhesive bonding application. The designer may find that a number of adhesives provide the required load bearing properties and the selection may require a more detailed consideration of the processes involved in the fabrication of the joint, the temperature over which it is to work and the environment in which it will have to operate. The article attempts to provide the reader with an insight into the effects of factors such as time and temperature used in the cure process, details of the components in the mixture and the effects of various additives on the physical properties of the adhesives which are created. The performance of an adhesive may vary with time as a consequence of stress-induced changes which are triggered by thermal effects or by hygrothermal factors. The review considers joints created using metal substrates and carbon fibre composites. The performance and durability of an adhesive bond is critically dependent on the stability of the interface between the adhesive and adherend and is sensitive to the pre-treatment processes used in the creation of the bond. The review outlines how broadband dielectric measurements can be used to non-destructively monitor the cure of adhesive bonds and the processes involved in ageing of joint. The dielectric method gives an insight into the fundamental processes which are giving rise to the changes in the mechanical properties of the joint as they age.