https://www.safeguardclothing.com/uk/articles/how-does-a-stab-proof-vest-work/ Second paragraph of this site refutes your statement regarding Kevlar being ineffective with stabbing attacks. The Wikipedia entry also calls out that Kevlar is commonly used for protection against cuts. Not calling myself an expert here but I find it unlikely that a tight packing of spun fibers would be crap at dealing with a knife.