In the present work, the detonation wave structure and detonation parameters for nitromethane (NM) and its mixtures with polymethylmethacrylate (PMMA) and glass microballoons (GMB) were studied by a velocity interferometer system for any reflector laser interferometer. The PMMA concentration varied from 2% to 4%. It is shown that PMMA additives lead to a change in the reaction zone structure, which can be observed as an appearance of a cellular instability of the detonation front. The detonation parameters of the mixture up to 3% PMMA are close to those of pure nitromethane and reduced when 4% PMMA is added. The addition of 2% GMB to the NM/PMMA mixture leads to the formation of a detonation front with a characteristic size of heterogeneities on the order of GMB diameter. In this case, the detonation parameters are reduced, and the values of the detonation velocity decrease by about 10% compared to NM/PMMA mixtures.
Investigation of shock-wave compressibility of three anisotropic materials (carbon fibre reinforced plastic, textolite and kevlar) was performed by a VISAR laser interferometer. Two of these composites consist of the same aramid fibers (textolite and kevlar) and two of them have the same structure (CFRP and kevlar). The structure of compression pulse and shock wave velocity of materials were obtained in each experiment. The shock wave structure in tested composites significantly depends on the fibers orientation - a two-wave configuration is recorded in almost the entire range of studied pressures when shock wave propagates along the fibers. Hugoniot parameters of anisotropic materials were obtained in the coordinates of the shock wave velocity D – particle velocity u for two orientations of the fibers. Hugoniots of kevlar, textolite and CFRP with perpendicular orientation of the fibers are parallel to each other. For kevlar and CFRP, the shock wave compressibility almost does not depend on the fibers orientation relative to the direction of the shock wave propagation. In textolite with parallel orientation of the fibers, the shock compressibility is determined by the properties of unidirectional aramid fibers, and Hugoniots for two directions differ significantly.
In this work, the detonation wave structure and detonation parameters of mixtures of gelled nitromethane (NM) with hollow glass microballoons (GMBs) are investigated with a laser velocimetry technique. It is shown that the addition from 0.5 to 13 wt. % GMB with the mean diameter of 70 μm does not qualitatively change the reaction zone structure of gelled NM, and it corresponds to the Zeldovich–von Neumann–Döring theory, predicting the formation of the von Neumann spike. The detonation parameters of the explosive mixture monotonically decrease—in particular, the ideal detonation velocity drops from 6.3 km/s for gelled NM to 3.7 km/s for its mixture with 13 wt. % GMB. The addition of GMB leads to a significant reduction in the critical detonation diameter, which decreases from 16.5 mm in gelled NM to 3.5 mm in the mixture with 8 wt. % GMB. The influence of polymethylmethacrylate concentration in the mixture of gelled NM with GMB on the value of critical diameter of the mixture is observed.
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