An innovative study of the debonding process for adhesively bonded interfaces under different loading conditions

The prediction of the interfacial failure mechanisms for adhesively bonded joints and composite structures is a well-known issue that has been studied both theoretically and/or numerically [1,2]. Small loads usually leave an adhesive junction bonded, where a jump of displacements is allowed due to the compliance of the interface. An increasing load, instead, can lead to adhesive breaks in one or more interface points where a crack starts and propagates along the interface, up to the complete detachment of the adherends. This work focuses on the development of a new theoretical approach to determine the debonding onset and propagation along weak interfaces under different loading conditions. The interfacial problem is addressed by means of the cohesive crack modeling, assuming a linearelastic behavior for the adherends and concentrating all non-linearities at the interface. This means that interfaces are considered as an assemblage of two sublaminates partly bonded together by an elastic interface. Such interface can be modeled as a continuous distribution of elastic springs acting along the normal and/or tangential direction depending on the interfacial loading condition. This generalizes the idea suggested recently in [3] for a single mode-I debonding. The analytical predictions of crack advancement, length of the process zone, maximum load and load-deflection response, are compared to the numerical results as provided by a simple nodeto- segment contact formulation. This is here generalized to handle cohesive forces along the normal and tangential directions, as employed in [4]. The very good agreement between analytical and numerical results confirms the accuracy of the theoretical proposed formulation.