Not 100% sure on the dates but...
John Watson's car ripped itself in half at Monza in 82 I think - but that was 82, a long time ago. Then again a Footwork/Arrows split into two when it crashed at the Swimming Pool section in Monaco in around 1990, and in 94 an IndyCar was torn in half by a certain J Villeneuve driving straight through it at Phoenix. It's probably happened elsewhere in F1 and Indy, and it is definitely possible, but with the strength of the Carbon Fibre shells these days it's probably not very common or easy.