Solid-shell mesh connenction, right thickness for a shell skin (transition) elements?

Hello all,

could someone help me with this topic.

I am doing a mesh connectivity between a solid and a shell mesh (I connected the shared nodes, it is a T-junction). I created on a solid surface a thin skin of a shell elements (as a transition between shell and a solid mesh).

How should I choose a correct thickness of that thin (skin) shell elements and how could I validate that the results with this thickness are OK, is there some mechanism to check it.

Are the CTRIA3 elements a bad choice to create a thin skin mesh or should be CQUAD4?

Thanks in advance.

Best regards,

Mario