why would you have to reinforce it? that's backwards thinking, cars are made to be shock absorbing so you don't have to, it is safety, I rather loose a car than get a lifetime of meds and therapy because my truck didn't have a strong bumper.
80's and before cars used to projectile people out of them, mortality rate on car wrecks is less, example the dude sandwiched between 2 18 wheelers...
I know cars are made to crush and absorb the impact so your neck and the rest of the body can walk just fine. but dude there is a balance between absorbing the impact and getting torn appart for a 15 mph hit.
I don´t expect to have a war tank so I can ram other cars without a scratch, but on the other side I will not accept to take my truck to a shop and leave it there for a two week body repair just because a soccer mom in minivan hit me in a parking lot.