For home-brewed armor, you're going to need to go hardened tool steel, and fairly thick. Heat-treating it the same way you heat-treat an AK's receiver might be a good choice, as it's really hard but has a degree of spring to it.    Covering it with something to reduce fragmentation isn't a bad idea, but I wouldn't use wood. Carpet squares would do a better job of catching fragments, and you can get the adhesive variety. Not sure how well that'll stand up, but it'd be worth trying out at least.