Cohesive Zone Model to Investigate Complex Soft Adhesive Failure: State-of-the-Art Review

Soft adhesives are widely used in soft robotics, biomedicine, flexible electronics and other fields. In practical applications, soft adhesives are frequently subjected to monotonic loading, static loading and cyclic loading. It is extremely important but challenging to analyze the failure behavior of soft adhesives due to their complicated mechanical properties and failure mechanisms, as well as the effect of different loading conditions. In this paper, the methodology of developing the cohesive zone model (CZM) for understanding the failure behavior of soft adhesives is systematically reviewed. First, for the one-time failure of soft adhesives, the establishment of the CZM considering the effect of loading rate, fibrillation, and mixed-mode loading is summarized. Second, the delayed failure of soft adhesives is studied. The development of the corresponding CZM considering the creep behavior under constant force and various potential mechanisms to explain the delayed failure under displacement holding is discussed. Then, for the fatigue failure of soft adhesives, remarks for CZM that are capable of expressing the loading-unloading process under the high cycle fatigue process and addressing the effect of viscoelasticity on fatigue damage have been provided. Finally, based on the application of soft adhesives in the frontier areas, the challenges and prospects faced for future research are presented.