Negative value of energy release for an adhesvely bonded DCB
I'm trying to calculate the mode I of energy release rate in an adhesively bonded DCB. The value of G1 is negative and it is strange. I would be grateful if you could give me your suggestions to solve the problem. The image of the model is as follow:
Boundary conditions: The two middle layers are adhesive and the upper and lower layers are Al.
The calculated value of G1:
The per-Meshed crack