The Monroe effect
refers to the characteristics of the detonation of a volume of explosive
around a hollow or void, a shaped charge
. Explosive energy is released directly away from (normal to) the surface of an explosive, so shaping the explosive will concentrate the explosive energy in the void. If the void is properly shaped (usually conically), a high-velocity jet of plasma
In military applications, a Monroe-effect shaped-charge warhead can be expected to penetrate armor equal to 150-250% of the warhead diameter.
Compare to the Misznay-Schardin effect.