An experimental data reduction method for the Mixed Mode Bending test based on the J-integral approach

The Mixed Mode Bending test (MMB) is suitable for measuring the interlaminar fracture toughness of composite materials under mixed-mode loading. Data reduction is usually based on the assumptions of Linear Elastic Fracture Mechanics, which are not fulfilled in configurations involving large scale fracture, such as in adhesive joints. In this work, a J-integral-based method that can be applied in presence of large fracture process zones is presented. The proposed method requires less input information and avoids crack length monitoring during the test, which reduces the uncertainty of the results as compared to traditional methods. The method is shown to accurately compute the fracture toughness in a delamination test campaign and to provide results with lower uncertainty than those of the ASTM standard method.