There is no provision to expel a member, it was considered in drafts for the treaty of Lisbon but not included.

It's possible to suspend members' voting rights but it requires an unanimous vote of the European council (sans the target member who can't vote).

In what way would it just happen? The treaties do not allow it, amending the treaties would require an unanimous vote, trying to circumvent would cause any of the non top members (pop or economy wise) to gtfo asap.