Dear Dave, 

I managed to couple the nodes. In "mesh by Id", I verified that the command selected the

 correct nodes. The command was written like this:

But after that, the results increased a lot. The response obtained by the authors of the article was 11,8 N/mm.  Coupling the nodes, I obtained 1,2487e+018 N/mm and without the coupling 7.4 N/mm. 

I have experience with composite plate models. I don't know what could have happened for the value to increase so much after the nodes were coupled.

Can you help me?