Pulse Wave and Rock Fracturing Characteristics of Composite Energetic Materials Ignited by Underwater Wire Electrical Explosion

In this study, experiments were conducted to investigate the electric explosion initiation of composite energetic materials (CEMs) by using Cu and NiCr wires in water. The composite energetic material is composed of Al powder and a heater, and there are three formulations after mixing according to the mass ratio (1:1, 1:2, and 1:4). Metal wires with a diameter of 0.5 mm and CEMs were placed inside plexiglass tubes, and two water pressure sensors were arranged at a distance of 50 cm from the wire ignition center; the pulse wave peak pressure and impulse were employed as the parameters for the energy output. Finally, rock fracturing experiments and their mechanical principle analysis were carried out. The results indicate that, compared to a single metal wire electric explosion, it can ignite CEMs to form larger pulse wave energy, and the peak pressure is increased by 3.2 times; the pulse wave peak pressure formed by Cu wire ignition of the CEMs was slightly higher than using NiCr wire under the same conditions, but the impulse generated is the opposite. As the Al powder in the CEMs decreases, the peak pressure gradually increases, which is related to the chemical reactions inside the CEMs. In the experiment of fracturing rocks, water jet and strong light radiation phenomena were discovered, and a complex crack network was formed; the cracks near the pulse center were mainly caused by compressive shear stress, while the cracks in the middle and far parts were mainly formed by radial tensile stress and water wedge action. Finally, with the help of high-speed photography technology, the mechanism by which metal wire electric explosions ignite CEMs in water has been clarified; the combined effects of the shock wave, thermal effect, and light emission generated by the electric explosion of the metal wire drove the release of chemical energy from the CEMs, which is of great significance for the development of this technology.