I'm wondering if you could make a composite sandwich (to save weight and cost)..
inside and outside sheet aluminum, center piece of the plastic.............
Might actually be stronger than equivalent weight of solid metal.... (or lighter for equivalent strength)
Carbon fiber and kevlar might make something that could withstand the impacts, but it likely would stand up to repetative impacts. Anything from plastic alone would have to be dipped in Line-X to keep it from shattering, and then again it might not hold up that long. When my buddy had his Line-x store he sprayed a cinder block w/line-x and could drop if from the top of his shop(about 25ft) and it would just bounce. But after about 30 drops it started to show wear and tear.
Aluminum diamond plate and a steel frame is about as light as you can go and still have enough strength on the trail for the skid plate to work as impact protection. I have even used the skid plate in my '91 to slide the truck up onto rocks, and it is holding up fine.
