IZOD Units, kJ/m^2 to ft-lb/in
Yes, mathematically, J/m gives you Newton. But IZOD impact strength test is a dynamics thing, so there is a hidden time element here. That is, the J/m unit is only meaningful when the impact test is done per ASTM D256 specs. That is, it's not only the amount of the energy that matters, it's how fast (time duration) this much energy is delivered matters the most in impact tests. This time element is pre-determined by the testing apparatus and is not apparent if you only look at the J/m numbers.
Bottom line is, the unit J/m needs to be used in conjunction with the IZOD testing specs to be meaningful. If you just apply a static force calculated by Joule divided by meter, most likely you won't be able to break the specimen.