What are the advantages / disadvantages of a rock climbing hat made from hard plastic to one made out of carbon fibre?
I have done a Google search already, but wanted some pointers with people who have experience.
I don't have any specifics on carbon fibre, but from indoorclimbing.com:
Fiberglass and polycarbonate composite (which would include carbon fibre) climbing helmets absorb the shock energy by breaking. The outer shell of the composite helmet absorbs the energy. Plastic and nylon helmets transfer the shock to the inner cradle harness. Helmets made from fiberglass or polycarbonate are good choices for ice climbing.
Plastic climbing helmets are lighter than the fiberglass or polycarbonate composite helmets, they can also survive more wear and tear.
I use plastic helmets, as I mostly sport climb, and rarely use multiple pitches so I just want a helmet that is light, will take the odd bash from small stones without shattering and will be cheap to replace when I need to.
Since a high quality polycarbonate helmet is now so light, affordable and durable; the added cost and limited weight benefit of carbon fiber seems to be of limited use for all but the most weight conscious or sponsored mountaineers. Plastic fails in a much more human friendly manner without sharp edges of carbon and hard resin that it's generally superior for helmet covering and strong enough for protection from sharp objects.