PSI - Issue 79

Umberto De Maio et al. / Procedia Structural Integrity 79 (2026) 386–393

390

Figure 3. Adopted computational meshes.

The different nonlinear processes of crack propagation in the multiphase domain, such as within the mortar matrix and along the Interfacial Transition Zone (ITZ), are simulated using the cohesive model described in Section 2, by using a bilinear traction-separation law. The required cohesive parameters for the numerical tests are summarized in Table 1. These include the tensile strength f t , the initial fracture energy G f , and the total fracture energy G F . The table also lists the parameter ψ , which defines the position of the kink point in the adopted bilinear softening curve (Roesler et al., 2007).

Table 1. Material properties and cohesive parameters adopted for analyses.

f t [MPa]

G f [N/m]

G F [N/m]

Materials

ψ

Mortar matrix

3.3 1.0

35

78

0.25 0.33

ITZ

2.2

5.5

The results of the mesh sensitivity analysis are reported in Figure 4 and 5. Figure 4 plots the load versus CMOD curves obtained by using the different computational discretizations. It is evident that the curves are in excellent agreement, showing only minor deviations in the post-peak softening branch. This overlap suggests that the global structural response predicted by the model has largely converged, even with coarsest meshes (Mesh 1 and 2) are employed.

Figure 4. Predicted loading curves.

In contrast, the local fracture behavior, depicted in Figure 5, reveals a clear dependence on the mesh refinement. This figure illustrates the predicted crack trajectories for all four meshes. For the coarsest discretization (Mesh 1), the crack path is visibly jagged and non-physical, as it is artificially constrained to follow the large, angular element