From Meyer:
"
Brisance
Brisanz
The performance of an explosive cannot be expressed by means of a single characteristic parameter. Brisance is the destructive fragmentation effect of
a charge on its immediate vicinity. The relevant parameters are the detonation rate and the loading density (compactness) of the explosive, as well as
the gas yield and the heat of explosion. The higher the loading density of the explosive (molding or pressing density), the higher its volume specific
performance; also, the faster the reaction rate, the stronger the impact effect of the detonation. Moreover, an increase in density is accompanied by
an increase in the detonation rate of the explosive, while the shock wave pressure in the detonation front (Detonation) varies with the square of the
detonation rate. Thus it is very important to have the loading density as high as possible.
This is particulary true for Shaped Charges.
Kast introduced the concept of “brisance value”, which is the product of loading density, specific energy and detonation rate.
Brisance tests are upsetting tests according to Kast and Heß; the compression of a copper cylinder is determined by actuating a piston instrument;
alternatively, a free-standing lead cylinder is compressed by the application of a definite cylindrical load of the explosive being tested: Upsetting
Tests.
"
ETN:
Specific Energy = 1091 kJ/kg
Detonation Velocity = 8000 m/s
Density = 1.6 g/cc (obtainable loading density?)
PETN:
Specific Energy = 1205 kJ/kg
Detonation Velocity = 8400 m/s
Density = 1.7 g/cc (obtainable loading density?)
Brisance Value = Loading Density * Specific Energy * Detonation Rate
Brisance ValueETN = 1600 kg/m^3 * 1091 kJ/kg * 8000 m/s
Brisance ValueETN = ca. 14 billion
Brisance ValuePETN = 1700 kg/m^3 * 1205 kJ/kg * 8400 m/s
Brisance ValuePETN = ca. 17 billion
Relative Brisance Value PETN / ETN = 17 / 14 = ca. 1.21
I may have underrated ETN in terms of density, but PETN still comes out significantly ahead in terms of brisance even with more optimistic numbers for
ETN.
Note: Aluminum is added to PBXs and putties(plastic explosives) sometimes, but not in shaped charge applications, from what I understand, or other
applications where brisance is much more important than energy output and a long drawn out impulse. Most applications that use these types of
explosives require a high brisance shattering action. Simply because of the distance between atoms, the relatively poor mixing and the energy
requirements of the reactions (probably other reasons) the secondary oxidation reactions are much slower and add to blast effect, but are not very
helpful to brisance as I understand it. Particles of high explosive are embedded in a binder/plastic matrix (not well mixed at all in comparison to a
molecule of high explosive!).
[Edited on 14-2-2016 by Hennig Brand] |
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