Whoa, whoa, slow down there. Free radicals, usually reactive oxygen species, are some of the most reactive molecules known. They can and will destroy any organic material they come across. Especially DNA. Lengthy PDF and a paywall, but hey, its far more studies than you actually cited.

(opinion starts) That said, I'm not going to argue that antioxidants actually will have some significant effect against aging. You can't just flood your body with enough antioxidants to really slow down aging, without causing other harm, such as compromising your immune system.(opinion ends)

We should. Lets introduce you to what they mean. Diamonds are anything but tough, they don't take much energy to fracture. They are, however, hard, meaning they take a LOT of force to deform (Rockwell Hardness, not Moh's). They also can scratch most other materials without damage (that's Moh's). Carbon fiber composites are NOT tough under impact. They have a very high tensile strength. Tensile strength is the tensile stress (pulling force over area) required to break the material. Titanium alloys have a nice balance of impact toughness, resilience, and density, so they can take a large impact without allowing the object to penetrate the plate or significantly damage the batteries on the other side, while not making the car as heavy as a tank. Wikipedia/google is your friend. They have decent explanations of this sort of thing.