Crack equivalent concept applied to the fracture characterization of bonded joints under pure mode I loading

In this work, an accurate and suitable data reduction scheme is developed to measure the fracture energy of adhesive joints under pure mode I loading. The method is based on the crack equivalent concept and is applied to the double cantilever beam specimen. Using the proposed methodology it is not necessary to measure the crack length during propagation, which can introduce non-negligible errors on the fracture energy measurements. Moreover, it accounts for the fracture process zone effects which can be significant when ductile adhesives are used. The new method was compared to classical data reduction schemes and was validated numerically using a trapezoidal mixed-mode cohesive damage model. The fracture characterization in mode I using a developed trapezoidal cohesive damage model is performed by an inverse method. Excellent agreement between the numerical and experimental R-curves was achieved demonstrating the adequacy of the proposed method.