I am doing some simulations of drilling carbon fiber reinforced plastics (CFRP) with Abaqus/Explicit. 3D Hashin's damage model with damage evolution has been defined for the CFRP composite. The drill bit was defined as a discrete rigid body. Cohesive contact has been deployed to model the interlaminar properties and simulate the delamination damage. (see model definition 1 and 2)

- Thrust force The main problem of my model exists in the simulated abnormal thrust force. The thrust force returns to zero every once one layer of element is removed as shown on the attached Fig.1 , which I think might be due to elemet deletion. The trend of the trust force is not in agreement with experiment result. The actual thrust force when drilling CFRP can be found on the attached Fig.2 . Looking forward to have some discussion on how to debug the drilling thrust force. Thanks.