What is cohesive failure in the context of adhesive bonding?

Cohesive failure occurs within the adhesive material or the adherend itself rather than at the interface between them. In the context of adhesive bonding, it implies that the adhesive has lost its integrity due to stress or load, causing a failure within the adhesive layer or the material it is trying to bond. This type of failure indicates that the adhesive was able to form a bond, but the forces acting on it were enough to overcome its internal strength. The adhesive might break or deform, leading to a separation within its own structure rather than a clean separation along the bonded surfaces.

Understanding cohesive failure is crucial for engineers to evaluate and improve adhesive durability, influence bonding strategies, and predict the performance of adhesive joints under various conditions. This knowledge helps in designing better materials and bonding techniques that can withstand anticipated stresses in applications.