Whether or not you knew them doesn't change the fact that it happening was completely inexcusable but it can alter your perception. If attacked by complete strangers you may still be able to trust those close to you whereas being attacked by someone you know especially a loved one can make trust something that feels impossible to give. If you can't trust yourself how can you possibly trust others.

I totally relate with self blame for putting yourself at risk. I gave my attacker a lift home when he was drunk and upset. For years I believed that there must have been something I did or said that made him think I wanted him to do what he did. It wasn't until I went over details of my assault with my psychologist that I was able to start to see things differently. Rough sex is one thing if that's what people are into but being beaten and choked when you try to make it stop or get away definitely takes the blame away from the victim. All sexual assaults are an act of violence even if they don't involve a beating. Being unable to fight back successfully to make it stop was also a struggle for me to get past until I realised that I survived my assault at least physically. Nothing anyone says or anything you do can take back what happened to you but by learning to cope with it is how I took back some of the power that was taken away from me that night. 

My assault was 10yrs ago and there are still bad days and triggers that flare up my PTSD but I now have the coping techniques to deal with them when they happen.