*Debond option and VCCT fracture criterion in Abaqus

[mahval]

Dear All,

I am kind of new to abaqus software. I am trying to model a crack propagation with ABAQUS DEBOND at interface layer of two different types of concretes. I would like to know:

1- How can I define “ *Debond” option in abaqus v6.12? I couldn’t find this option in abaqus sub-modules? Should it be plug-in?

2- What is the main difference between “critical stress” and “VCCT” types of fracture criterion?

Thanks a lot in advance.