Presenting unpublished work at PhD defense. What will happen if the committee are excessively critical of the results? I am about to defend my thesis and part of my presentation would involve results and conclusions from my two unpublished works. Personally, I am confident about the results and conclusions. My advisor is yet to work on the drafted manuscripts so she is familiar with the results but has not critically thought about the numerical methodology implemented or any other issues with the results. I have presented the results in different conferences, but again, no one really asks questions at conferences. These were not conference proceedings, so no peer review has been carried out yet.

So, I was wondering, what will happen if the committee (who are experts in my field) sees a potential fault with my work which I might have overseen? What if the potential fault undermines the works I have done? Will that lead to a negative outcome in my defense?
While I agree with the comment of Jon Custer, you could, indeed, have an issue if someone, validly, finds a flaw. But, assuming everyone is rational (not always valid, I know), it is unlikely to result in total failure. 

I've had students in such situations (not my own, but I was a committee member). We just sent the student back to work to resolve the issue and re-schedule a defense after the dissertation was revised as appropriate.

But, it is what it is. If objections are raised, do your best to explain why you accepted the papers. That is, show due diligence and that you seriously considered the arguments. But anyone can make a mistake, either you or the person raising an issue. Work it out. 

I hope you have a rational committee. And good luck. If they are rational, then fining a flaw now is better for you than finding it later, I think.