I think ECC’s tensile strain-hardening behavior might not be directly captured by the default CDP settings, which are more focused on brittle materials. You would need to modify the model to reflect ECC's ductile behavior after cracking. Additionally, the CDP model may require fine-tuning of parameters such as the dilation angle, flow potential, and damage evolution law to better represent ECC’s specific failure modes.

On the other hand, the Hashin Damage Model was developed primarily for composite materials, where failure mechanisms such as fiber breakage, matrix cracking, and delamination occur. It is a good option for materials that behave in a ductile manner with distinct failure modes in different loading directions.

Now, it depends on your research goal and objectives. If your focus is on traditional concrete-like behavior (cracking and crushing) and ECC's behavior is close to quasi-brittle materials, you should consider using CDP. However, if the focus is on fiber-reinforced composite behavior, particularly if ECC is fiber-reinforced and you are interested in different failure modes (such as matrix cracking or fiber breakage), then the Hashin Damage Model may be more appropriate.

The question now is: What does your model represent in terms of actual behavior in your research work?

Engr. Tufail In my research, the model has to represent the mechanical behavior and failure mechanisms of engineered cementitious composites (ECC) under different loading conditions. Specifically, the aim is to simulate how ECC responds to stress, strain, cracking, and damage progression.