We knew the Audi R18 was fast. During the test session at Spa, the R18 was clocked at over 200mph on some turns. Evidently, that type of speed can wreak havoc on bodywork with even the slightest impact causing dramatic collisions. During the race, the R18 appears to have hit some debris, which caused the door the explode. Yes, explode. Luckily no one was hurt.

https://www.youtube.com/watch?v=D6pgNca8Rj0