What is the bottom of the car made of ?

Hello, There may be damage if you scrapped the bottom of the vehicle on something. There are many plastic guards, and operational components underneath, but there are also hard suspension components that can help protect the engine, though not meant to. Feel free to have someone take a look, and you may want to consider using a body shop instead of a mechanical repair facility. The chances are, if anything is damaged, it is probably just plastic guards. Just be sure, and either look under to make sure nothing is amiss, or have it inspected.