Any material that fulfills the following characteristics is an explosive.
It must be chemically unstable. Any initiation must produce an explosion accompanied by large changes in pressure. The material must contain enough oxidizer to maintain the extremely rapid combustion. So in order to be classified as an explosive material the product must meet the criteria by containing fuel and oxidizer (in the proper balance)
Classification of Explosive Materials
- 1. Low Explosives
- a. Cannot support a detonation wave
- b. Is a mixture
- c. Initiated by heat.
- d. Confinement required for explosion
- Example: gunpowder
- 2. High Explosives
- a. Undergoes detonation without confinement.
- b. Is a compound
- c. Initiated by shock or heat
- d. The reaction is supersonic.
- e. High brisance.
- Example: Dynamite
Another characteristic of explosive is sensitivity - The amount of external force to initiate the reaction. The force can be anything from shock, impact, friction, electrical discharge, or any other source. Primary Explosives require a small quantity of energy to be initiated and are extremely sensitive but have less power than secondary explosives, they are in detonators and initiation systems (Examples: Lead azide, Mercury fulminate). Secondary Explosives are relatively insensitive but are powerful (Examples: Dynamite, RDX, PETN)
Detonation (Initiation Sequence)
Also called a firing train, this is the sequence of events which cascade from relatively low levels of energy to cause a chain reaction to initiate the final explosive material or main charge. They can be either low or high explosive trains. Low explosive trains are something like a bullet - Primer and a propellant charge. High explosives trains can be more complex, either Two-Step (e.g. Detonator and Dynamite) or Three-Step (e.g. Detonator, Booster and ANFO).
Characteristics of Explosions
Explosive force is released at 90 degree angles from the surface of an explosive. If the surface is cut or shaped the explosive forces can be focused directionally, and will produce a greater effect. The following have been used:
- 1. Conical (Monroe effect, discovered in 1883) - A hollow cone having a metal liner covered by an explosive. The angle of the explosive direct a jet of material towards the target. The basis of hollow-charge.
- 2. Linear - The explosive charge is covered by a liner, but in the shape of a flat plane.
- 3. Platter (Misznay-Schardin effect, discovered in 1944)- A solid piece of metal, with a quantity of explosives placed on only one side or plane, an idea used in the Claymore mine.