Wood armor - we're back to the medieval days!
As with most (all?) engineered wood products - what about when it gets wet?
Swelling introduces a large number of nano-defects in the cellulose structure. Although there is little swelling of a single CNC, water can penetrate into amorphous cellulose with ease, pushing apart the individual cellulose molecules in those regions. In addition, the bonds and interfaces between neighboring CNC will be disrupted, thereby significantly reducing the strength of any material reinforced with CNCs. To make matters worse, water can move easily over the surface/interfaces of the CNCs, thereby allowing water to penetrate far into a composite containing CNCs.
They suggest painting it. To be honest, I'm a skeptic. We wore body armor during my time in Iraq, and the abuse that our gear received cannot be overstated. Rain, heat, jumping over walls, dealing with mud. No thanks, I'll stick with Kevlar.