It took me a really long time to be able to handle doing a rape scene. Even knowing and trusting my partner, I still would shut down and not feel sexual. You can work towards it with scenes of control and the like but just make sure that they know how to deal if they trigger a panic attack or a flashback in you. They need to be able to ground you and make you feel safe and that can be hard if they are in the head space of kidnapping/raping you.
Communicate ahead of time every possible thing--I did a thread on rape fantasies (R is for Rape Fantasies but here are some questions to ask:
1. Will a weapon be used?
2. Will there be abusive language or name calling?
3. Will humiliation or degradation be involved?
4. Will there be actual penetration?
5. Will there be physical violence?
6. What is the safe word?
7. Will the scene be scheduled or will it be a surprise?
8. Will it involve kidnapping?
9. Will it involve a mask, blindfold, bondage, or costumes?
10. What are the limits (choking, slapping, fisting, etc)?
11. Will it involve bodily fluids? If so what type of precautions will be used (condoms, gloves, etc)?
12. At what point will the scene stop?
I hope that helps.