In all three Iron Man movies as well as The Avengers, the Iron Man suit utilized by Tony Stark was rather heavily damaged in the various fights. This is especially true in the first Iron Man movie where his suit was crushed by Obadiah.
However, I noticed that the Arc Reactor in Tony's chest basically sustained no physical damage. There were several scenes (Iron Man, The Avengers) where his Arc Reactor stopped working for a short period of time but there was no visible damage to the structure of the Arc Reactor itself.
Is there an in-universe explanation of this?