Science and Technology of Energetic Materials

Vol.71, No.5 (2010)

Research paper

Card gap tests of plastic high explosive by using mortar,light weight concrete and sand as gap materials
Tomoharu Matsumura, Koki Ishikawa, Tomotaka Homae,
Kunihiko Wakabayashi, and Yoshio Nakayama


The series of card gap test like experiments were carried out to examine the relation between gap length and sympathetic detonation of plastic high explosive, and the scale effect of shock initiation sensitivity of the explosive. Composition C-4 explosive charges (1400kg∙m-3 in density) of cylindrical shape and with same weight, were used as donor and accepter charges. The ratio of charge length to diameter (L/D) was set to be one. The experiments have been conducted with five explosive weights; 10g, 40g, 320g, 2.5kg, and 20kg. Three kinds of gap materials, i.e., mortar, light weight concrete and sand with various thicknesses, were used. The sand layer was sandwiched by two thin mortar disks. Detonation or no-detonation of accepter charge was determined by observing the situation of a mild steel witness plate after the experiment. It became clear that, even in the case for 20 kg charge, the critical gap length of detonation and no-detonation can be evaluated in the range of 20mm or so. Furthermore, in log-log coordinate system of gap length as a function of explosive weight, it was found that all three gap materials showed good linear relationship, and those inclinations were larger than the value of the scale factor of explosive weight ( =0.333). It was obtained a tendency that the material with higher density showed higher obstruction effects to prevent the sympathetic detonation.


shock sensitivity, sympathetic detonation, gap test, scale effects, composition C-4.

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