Experimental and numerical characterization of adhesive joints with composite substrates by means of the Arcan test

An experimental and numerical investigation on adhesive joints subjected to three different loading conditions (pure shear, combined shear-tensile load and pure tensile) has been carried out through the Arcan test. The aim of this work is to investigate the effect of compliant substrates on the mechanical performances of the adhesive. Differently from traditional Arcan tests, where highly rigid substrates are used, U-shaped specimens made of carbon prepreg, final thickness 1 mm and 2 mm, have been bonded with a stiff epoxy and polyurethane adhesives. Nonlinear finite element analyses were performed to assess the stress state in the adhesives obtained by the experimental tests and showed a good correlation with the experimental results. In particular, the shear and tensile tests with the thicker substrates were used to determine the properties of the adhesives, while the 45◦ loading case combined with the thinner substrate results were used for validation. Results show that the compliance of the substrates significantly affects the fracture propagation of both adhesives in Mode I, as well as the maximum load of the epoxy-based joint for all the loading conditions. The results suggest that the Arcan test is suitable for the complete characterization of this type of adhesive joints.