Suppression of Jet Formation During Explosive Dispersal of Concentric Particle Layers

The explosive dispersal of a spherical layer of solid particles surrounding a high-explosive charge is investigated. The shock-consolidated particle layer fractures into discrete fragments which move radially outwards shedding particles in their wakes and forming jet-like structures. The tendency to form jets is partially dependent on the material properties of the particles with brittle ceramic particles as well as soft, ductile metal particles being more susceptible to forming jets, whereas particles that are comprised of materials with moderate hardness, high compressive strength and high toughness are much less prone to jet formation. During the explosive dispersal of binary mixtures of "jetting" and "non-jetting" particles, the particles rapidly segregate. The jetting response present in these binary mixtures persists to volume fractions as low as 10% with respect to the "jetting" species. In the present study, we examine the effect that concentrically layering the same two powder species, silicon carbide and steel shot, at varying volumetric ratios, has on the resulting particle dispersal. It is seen that through the inclusion of an inner layer of sufficient thickness of "non-jetting" particles (steel shot), the strength of the initial shock wave can be attenuated and the jetting response of a typically "jetting" material (silicon carbide) can be suppressed. Measurement of the velocity of the two types of particles shows that the velocity, normalized by the Gurney velocity, is not a function of the volume fraction of the particles or the geometrical arrangement.