Presenting unpublished work at PhD defense. What will happen if the committee are excessively critical of the results?
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.