Development of advanced methods to characterise the fracture behaviour of flexible bonded joints: An overview

Abstract

In some cases, the scope of bonded joint characterisation methods applied in laboratory may not be aligned with the bonded joints used in industry. Experimental results produce uncertainty and cause the bonded joints to be replaced by mechanical joints. Experimental procedures evidence a strong dependence on specimen dimensions, type of adhesive, ageing and crack measurement. They are suitable for bonded joints with thin adhesive layers and rigid behaviour while bonded joints in industrial applications have many different geometries and types of adhesive. Moreover, they must withstand external loads and environmental conditions simultaneously, while cracks may not be visible. The present work summarises the methodologies developed to overcome the limitations of current experimental procedures. An analytical method is developed to evaluate the fracture toughness of bonded joints with any width-to-thickness configurations. It is also demonstrated that external loads accelerate the degradation of bonded joints exposed to environmental conditions. Consequently, a new durability test has been developed for bonded joints that considers sustained loads during environmental exposure. Finally, it is demonstrated that the Acoustic Emissions technique is suitable for crack growth monitoring in bonded joints, providing a reliable alternative to locate the cracks when they are not visible.

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