Modeling Shear Failure in Sandwich Beam Core

[Settler]

Hello all,

I am modeling a sandwich beam made of two isotropic (for the moment) materials, modeled with continuum shell elements.

Materials are aluminum and balsa wood. As of now, I capture the stiffness reasonably well, and my next step is to capture the failure.

I have tests from three point bending, resulting in the core shear failure, which is the failure mode I want to numerically capture.

I have the crushing strength of balsa wood.

Is there any way you could suggest me to have a damage initiation criterion?

Thanks