Brisance

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Brisance is a quantitative measure of the shattering power of explosives. Simply, it is the rate at which the explosive develops its maximum detonation velocity. With some exceptions, brisance increases with increased detonation velocity.[1]

Brisance is expressed with respect to TNT, which has a brisance of 1.00.

It is related to, but different than, explosive power. Think of explosive power as the ability to push, while brisance is the ability to shatter. Maximizing the brisance is critical for applications such as steel cutting or armor piercing, where maximixing the explosive power is important for uses such as earthmoving and road cratering.

The number, size distribution, and velocity of fragments produced by an explosive in a projectile is also related to the brisance of the explosive.

Brisance testing

There are several methods for testing brisance, which can give different values for the same explosive. Unfortunately, no single brisance test is practical for all explosives. For example, ammonium nitrate will not completely detonate in sand.

Sand test

In the sand test, 400 milligrams of the explosive are placed in 200 grams of sand and detonated. Brisance is calculated from the amount of sand crushed by the explosive. This test tends to give the lowest values.

Plate dent test

The plate dent test, in which a sample of the explosive is detonated in close proximity to a metal plate, evaluates brisance as a function of the deformation of the plate.

Metal cylinder

Another test places the explosive on top of a standard copper or lead cylinder, detonating the explosive, and calculating brisance from the compression of the cylinder.

Examples

Explosive Brisance
Dextrinated lead azide 0.40
Ammonium nitrate 0.54 (lead cylinder test)
TNT 1.00
HMX (explosive) 1.25 (sand test)
PETN 1.27-1.41 depending on density
Composition C-4 1.34
RDX (explosive) 1.25-1.45 (multiple tests)

References

  1. Military Explosives, U.S. Department of the Army, September 1984, TM 9-1300-214, p. 3-4