Fracture modeling using CZM in ANSYS APDL.

In CZM modeling, using a mixed configuration, in which the fracture formation is considered, both normal stresses (mode I) and shear (mode II), it is necessary to supply the parameters, through TBDATA, C1, C2, C3, C4, C5 and C6.

The corresponding values ​​are:

C1 - maximum normal stress at the interface;

C2 - maximum value of the separation between the interfaces after rupture, due to normal voltage;

C3 - maximum shear stress due to shear;

C4 - maximum value of the displacement between the interfaces after the rupture, due to the shear.

C5 - ratio between the maximum displacement, before the complete rupture and that corresponding to the beginning of the rupture process;

C6 - weight factor, designed to weigh the contribution of normal and shear stresses in the rupture process.

My doubt concerns parameter C5, since, in the mixed rupture mode, there is the contribution both of normal stresses and of shear. As C5 is the ratio between maximum displacements, which one to use? The ratio between maximum displacements due to shear or due to normal shear or stresses?