Thesis Abstracts 2005
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The Fragmentation of Metal Cylinders by Thermobaric Explosives
By: Mike Dunning, MSc
Supervisors: Dr. W.S. Andrews and Capt. K.M. Jaansalu
Abstract
Thermobaric explosives (TBXs) are mixtures of conventional explosives and specific additives, such as aluminium, that undergo combustion after the detonation reaction. This secondary combustion phenomenon leads to specific shape and propagation characteristics in the resulting shock wave. To complement the many recent studies on such blast-related properties, this research concentrated on the resulting fragment mass distribution and fragment velocity trends when TBXs were placed in metal cylinders. Comparisons were made with similar cylinders containing C4 explosive, as well as with in-service stake mines of similar geometry.
Most of the secondary combustion occurred after the fragments had passed beyond its influence. Consequently, the fragment mass distribution and fragment velocity were well predicted by the detonation properties of the conventional explosive bases. Explosives with higher detonation velocities and higher densities generated smaller and higher-velocity fragments. As casing wall thickness was increased, fragments became larger and slower. Increasing casing ductility led to larger fragments but had little effect on fragment velocity.
There is a threat that TBXs similar to those studied in this research could be used in fragmenting munitions. However, due to their reduced detonation properties, the metal casings of these warheads would need to be either thinner or less ductile than those that carry conventional explosives, in order to generate fragments of comparable mass. Infrastructure and personnel protected from the fragments generated by conventional fills would therefore also be protected against the fragments from TBX fills.
