If you want to do LARP or something similar, your best bet is to either make them entirely out of foam with perhaps a wood or PVC dowel through the core for stability, or else pep the weapons, make a mold from them, and cast them in something sturdy but flexible, like silicone rubber (again, a dowel suspended into the core during the molding process should give it some strength), but that could get expensive with essentially creating a solid, 2-4 ft piece of silicon. Traditional pep methods would be too brittle to survive more than a few clashes. In fact, most of the methods for weapon and prop making you'll find in the forums wouldn't be good for what you want to do, as they are for making props, show pieces that are not in any way meant to be functional or "combat ready," not even choreographed fighting unless the people wielding them are very, very good at the art of the "pulled blow," rarely, if ever, actually making contact with anyone or anything.