I think in all cases, though, you'd need to manage your own expectations of the outcome of telling people - their reaction might be understanding and validating, but it might not.
If you choose not to be specific and only say "trauma" (or, I suppose, "PTSD" if that's generally understood) it's likely that people will guess - rightly or wrongly - that it was rape. This assumption will sit there unspoken for ever more, unless you choose to tell them something different, and heaven only knows what they're imagining.
Some people may gossip about you. You may become an anecdote for them to tell people and your experiences be treated as the subject of idle, or even malicious, speculation.
Once they know, people may be sympathetic in some ways, but in other ways they may be unthinking, callous or even intolerant and impatient. At best, they'll be supportive and wonderful although inevitably they just won't get it some of the time. in the middle, they'll feel bad for you but they'll often forget or can't be bothered to modify their behaviour or conversation. Or they might make all sorts of assumptions which they won't budge from about what you can and can't cope with, how you feel, what you want, what you think. At worst, they won't want to have to deal with any of it and they'll wish you'd kept quiet - if it's an option they'll probably start avoiding you.