Q:

What would happen after the big crunch? 

What is the aftermath of the big crunch? 

A:

Singularity.  If a big crunch occurs, the entire universe will collapse under it's own gravity until everything is concentrated at one point.  What happens after that is really up to speculation. 
Moreover, in light of recent discoveries, this theory has been dismissed as being a implausible one.  There is evidence that the universe is expanding at an accelerated rate due to the presence of something known as dark energy, about which little is currently known except for the fact that it is repulsive and counteracts the effect of gravity, allowing the universe to expand.  Attempts at calculations suggest that dark energy increases over time as the universe expands, and this has raised doubts over the current explanations provided by the cosmological model.