If the bumper is made from ABS then an ABS solvent could be used to solvent weld strips of ABS on the back of the bumper across the crack to provide the necessary strength to prevent the crack opening again.
The solvent used for solvent welded waste pipes might work but something like Plastick 1506 would be much more agressive and hence make a better bond.
Test on a clean bit of the back of the bumper and don't get any solvent on the front.
The solvent used for solvent welded waste pipes might work but something like Plastick 1506 would be much more agressive and hence make a better bond.
Test on a clean bit of the back of the bumper and don't get any solvent on the front.