This photo was taken of a 2008 Honda Civic. It's looking down on the trunk floor right in front of the left tail light inside the trunk. The left frame member is below it, it looks just like this floor. The car was hit from behind right on left side right square on the reinforcement. There is no damage to the quarter panel (well a tiny bit right at the edge) and hardly any damage to the luggage lid. But it was hit REAL hard as you can tell. Yet the left rear door just a few feet in front of this opened and closed as new with hardly a change in the door to quarter gap! The reason I posted it is to show how energy management in a late model car helps in a impact.
People will often see a late model car damaged in an accident and say something like "it crumpled up like a tin can". Ladies and gentlemen, that is exactly what it is supposed to do. Not only that, it is what you WANT it to do!
This little area absorbed all nearly every big of the impact instead of passing it on thru the car and to YOU. Every bit of the damage is what you are looking at. You can see that a little bit of bending is going on just at the right of the photo, but honestly, just an inch or two out of this photos range the floor was PERFECT, as was the rest of the floor and car!
This area has what are called "crumple zones". These areas have little "ripples" in them like an accordion. They collapse in the first thousands of a second and absorb energy instead of passing it on further.
To repair this car the floor, the left frame rail extension get replaced and you are good to go.