is carbon fiber the lighterst material or is it that glass?? or is there more? whats the cheapest and the lighest?

 

abs plastic is probably cheapest AND lightest...
What are you looking to replace?
Titanium is also very light but far from "cheap"

 

It pretty much depends on how thick the material is. I've seen paper thin fiberglass hoods that weigh almost nothing compared to trendy carbon fiber hoods that are 90% epoxy and weigh almost as much as a stock steel hood.

Both materials can be very light compared to steel. It's a toss up between weight and strength. You can have a stronger, heavier hood, or a super light hood that offers zero structural strength.