A complex mixed-mode crack propagation test performed with a 6-axis testing machine and full-field measurements

A new type of mixed mode crack propagation test is proposed. A single crack is initiated and propagates in a stable way up to complete failure. A combination of tensile, shear and in-plane rotation performed by a 6-axis testing machine is prescribed. The rotation creates a tension/compression gradient in the sample ensuring the stability, while the shear direction is closely related to the orientation of the crack and the tensile load is responsible for the actual propagation. The experiment is performed in an interactive manner, namely, depending on the crack tip position estimated by Digital Image Correlation (DIC) during the test, the loading is changed to bifurcate the crack. The displacements of the sample surfaces are assessed using multiple DIC measurements and displacement sensors. The displacement fields on each face of the sample give access to the crack pattern, and also to the actual boundary conditions that are crucial for a faithful numerical analysis of the test. Last, the 6 load components are recorded enabling for a complete description of the 3D mechanical behavior of the specimen.