Can Body Armor Protect Against Cold Weapons?

It is recognized that body armor can provide bulletproof effect, but can body armor protect against cold weapon attacks? In fact, this also depends on what kind of body armor you are wearing. If it's just soft body armor like Kevlar fiber, it won't work. If there is a hard bulletproof plate inside, it may be able to block it.
The main working principle of body armor is to reduce the damage of bullets to the human body by absorbing the kinetic energy of bullets. The tensile strength of Kevlar fiber is very high, so when the bullet hits the Kevlar fiber, it will be stretched, thereby absorbing the kinetic energy of the bullet and spreading to the entire body armor. But this is not absolute. If it is a rifle bullet with high kinetic energy, it may break the Kevlar fiber at the site where the bullet hits. Therefore, most of the current Kevlar body armor will have a hard bulletproof insert added to it. The plate further absorbs the kinetic energy of the bullet to achieve the purpose of protection.
But cold weapons are different.
When you watch war movies, you will see scenes of sandbags being stacked on trenches. In fact, this is the same as the bulletproof principle of body armor. Because the weight of the bullet is small, the kinetic energy of the bullet will be quickly consumed in the sand, and eventually lose its lethality.
Why can a 0.5-inch large-caliber bullet penetrate an earth wall? The reason is that it weighs more and carries more kinetic energy, so it has stronger penetrating power.
The weight of the crossbow arrow alone is comparable to that of a 0.5-inch bullet, not to mention the shaft behind it. Because of this, although crossbow arrows are not as fast as bullets, crossbow arrows can easily pass through sandbags within range.
Summary: Therefore, bullet-proof suits like Kevlar, which are based on the principle of absorbing kinetic energy, cannot prevent crossbow arrows. If you want to protect against cold weapons, it is better to use professional stab-resistant clothing.