In this Instructable, a user named "hobbyman" sets out to reinforce a 3D printed bike part with fiberglass and epoxy resin. In the first method, he models the part and then fills and cures it. But then he realizes it would make an even stronger part if he created a 3D printed empty shell of the part, and then took his time to add the resin and fiberglass. He recommends the second method for the strongest part, and don't forget that the original part model has to be designed with the idea that the 3D printed plastic portion will simply be peeled away before it is used for assembly. Check out the full instructions at http://3dprint.com/108318/strengthening-3d-parts/