Fiberglass is commonly used for repairs or reinforcement on materials such as plastic, wood, metal, and even Styrofoam. Fiberglass will bond to almost any surface as long as the surface is properly prepared and scuffed. For repairs on PVC fiberglass works great and if applied properly will most likely last as long as the PVC does. Fiberglass is applied in layers of dry fiberglass mat that's saturated with resin. The resin's a very thick liquid that requires a catalyst in order to harden. You can find fiberglass repair kits with the mat, resin, and catalyst at your local auto parts supply stores.
Put on safety glasses and grind the rough edges of the damaged PVC smooth using a dye grinder. If there is a deep fracture, grind the damaged PVC out of the middle of the crack and gradually taper the edges. Lightly grind six inches all the way around the damage, being careful not to go deep into the PVC.
Wipe the damaged area clean using a rag and acetone.
Cut three layers of fiberglass mat using a razor knife that completely cover the damage. Make each layer 1/4 smaller than the last so the edges of the repair are tapered and not ledges.
Mix the fiberglass resin with the catalyst in a small bucket. Use a wooden stir stick in order to thoroughly mix the resin.
Wet out the surface of the repair with the resin using a four-inch felt roller. Apply the smallest layer of mat first, with the damage directly in the center of the mat. Saturate the mat with the felt roller and roll out any air bubbles using an air roller. Apply the next two layers following the same process and let the fiberglass cure until it's hard and cool to the touch.
Sand the fiberglass patch with 100 grit sandpaper to remove any burs or sharp hairs of fiberglass.