An Inverse Analysis Approach for the Identification of the Cohesive Zone Model Parameters of CFRP-to-steel Bonded Joints

Cohesive zone model approach represents a valid solution for the description of interfaces between two adherends, as in the case of CFRP-to-steel bonded joints. In the recent years, the application of externally bonded CFRP reinforcements has shown its effectiveness in the strengthening of existing metallic structures. Proper investigation of the interfacial behaviour is deemed necessary, since it is crucial in allowing stress exchange and avoiding failure mechanism which usually occurs due to cohesive de-bonding at the interface. A correct calibration of the model parameters is therefore needed to provide a reliable representation of the bonded joint response. In this paper, a robust inverse analysis procedure for the identification of the model parameters governing the interfacial bond behaviour is presented. Single-lap direct shear specimens tested under monotonic loading are considered for the numerical investigation. An exponential cohesive zone law is adopted and so the main parameters to be estimated are the peak shear strength and the interfacial fracture energy. The inverse analysis problem is formulated by using load-displacement curves and the shear stress transfer length as input data, with the latter being measured by digital image correlation technique. The identifiability of the sought model parameters is then investigated by means of virtual data, affected by different levels of noise, within a stochastic context implemented through Monte Carlo analyses. The robustness and performances of the proposed methodology are highlighted solving different numerical inverse problems, through the variation of the main properties of the bonded joint, in particular of the adhesive used, supporting thus possible planning of measurements setups for laboratory investigations.