I used to historical fence with a longsword waster (blunt practice sword) made of high-density nylon. I used that thing full-contact for almost two years, against other wasters, shields, and two-handed strikes against pells and it never cracked or split (and believe me after hearing some of the accidents, you check your practice gear religiously for signs of that damage.)
Then I lent it to a 12 year old for Halloween… and got it back snapped off at the hilt after he swung it around carelessly in one hand and struck a tree. How does that make any sense?