I. Plaksin

New Propellant Component, Part II. Study of a PSAN/DNAM/HTPB Based Formulation

A study of DNAM as a candidate ingredient for propellant formulations is reported. A formulation including DNAM and based on Phase Stabilized Ammonium Nitrate (PSAN) and Hydroxy-Terminated-Poly Butadiene (HTPB) was selected for the study. This includes thermoanalytical measurements on the mixtures of solid components and propellant samples. Performance is assessed by burning rate measurements. A new small-scale shock sensitivity test developed for studying the propellant under consideration is described. A good potential for DNAM was found for this formulation as revealed by the performance and low vulnerability of the PSAN/DNAM/HTPB composition.

Effect of GMB on Failure and Reaction Regime of NM/PMMA‐GMB Mixtures

The effect of the addition of small amounts of glass microballoons (GMB) on heterogeneous explosives has been investigated with the aim of understanding mechanisms that lead to the strong reduction of its critical diameter. However, there is no clear identification of the changes on detonation wave propagation and its structural features. To obtain a better understanding of the contribution of GMB as a particular heterogeneity, the detonation failure and the re‐initiation of NM/PMMA‐GMB mixtures is studied. Corner turning configuration was performed in order to determine the influence of the GMB concentration and size on failure phenomena by observing the trajectories of the divergent shock waves around the corner. The shape of the printed traces on a copper witness plate, coupled with detonation velocity and front curvature measurements, was used to evaluate the evolution of the detonation reaction regime and its cellular structure. The obtained results of printed flow lines show significant changes of t...

Instrumented Floret Tests of Detonation Spreading

The floret test was originally devised to permit comparison of detonation‐spreading performance of various insensitive explosive materials, using only the dent in a copper witness plate as a metric. Dent depth in the copper plate is directly related to the fraction of a thin acceptor pellet that was detonated by impact of a small explosive‐driven flyer plate. We have now added instrumentation to quantitatively measure the detonation corner‐turning behavior of IHEs. Results of multi‐fiber optical probe measurements are shown for LLM‐105 and UF‐TATB explosive materials. Results are interpreted and compared with predictions from one reaction‐rate model used to describe detonation spreading, and may be advantageous for comparison with other reactive‐flow wave‐code models. Detonation spreading in UF‐TATB occurred with formation of a non‐detonating region surrounding a detonating core, and re‐establishment of detonation in a “lateral” direction beyond that region.

Effect of Shear Stress in Shock Initiation of PBX

Initiation of hot spots‐reaction sites in PBX explosives by a linear shock generator has been studied under wide variation of the input shock pressure, from 3 GPa up to 20 GPa. A multi‐channel high‐resolution optical method based on application of a 96 optical fiber strips has been used for a comprehensive registration of the reaction spot initiation and following the processes of reaction growth or extinction. We have obtained strong evidence that reaction originates in the shear regions established by the induced shock. This suggests that shear has a major role in shock initiation. The pressure field in the front of reacted flow and the minimum size of reaction sites, which results in reaction growth, are defined as a function of the input shock pressure. Effect of shear stress is discussed concerning the grain sizes and mass concentration of HMX in the PBX’s.

Detonation Meso‐Scale Tests for Energetic Materials

The objective of the present study is to characterize, on the meso‐scale level, the detonation behaviour of PBX based on HMX , based in the minimisation of the test samples of energetic materials up to 10 mg. The development of a non‐intrusive, high resolution, optical metrology procedures, using multi‐fibber strip, allows the testing of PBX micro‐samples, formed by few crystals surrounded by binder, with the simultaneous registration of parameters as local detonation velocity and pressure, geometrical shape of detonation front and the structure of the shock‐to‐detonation transition zone. The enhanced information allows a better understanding of the processes of formation and propagation of detonation wave. This procedure can be applied to the study of new advanced energetic materials.

Shock Wave Propagation Process in Epoxy Syntactic Foams

The Shock Wave Propagation Process [SWPP] in epoxy syntactic foams [SF] (Hollow Glass Micro Spheres [HGMS] within an epoxy binder) with a nano‐second temporal and micrometer spatial resolution is presented and discussed. Samples with three different characteristic HGMS sizes were studied (42, 92 and 135 μm). For the samples with characteristic HGMS size of 92 μm, the effects of the density (0.64, 0.81 and 0.92 g/cm3) and of the loading pressure (20.0 and 9.6 GPa) were also analyzed. The obtained results show the effects of self‐organization (synergetic/cooperative) in the initial phase of the SWPP, associated to a layer‐by‐layer collapse of HGMS, and in the following phase of propagation, associated to the cellularization of the SW front. Specific experimental results, showing the SWPP in one or two layers of HGMS, and numerical simulations (LS‐DYNA 2D), of the pore collapse process in one layer of HGMS, were also performed in order to clarify the mechanisms of SW propagation.

Non ideal detonation of emulsion explosives mixed with metal particles

The detonation of ammonium nitrate based compositions like emulsion explosives mixed with metal particles was experimentally investigated. Aluminum powder with a mean particle size of 6 μm was used, and the mass concentration of aluminum on the explosive charge ranged from 0 to 30% wt. The values of the detonation velocity, the pressure attenuation – P(x) – of the shock front amplitude in a standard PMMA monitor and manganin gauges pressure-time histories are shown as a function of the explosive charge porosity and specific mass. All these parameters except the pressuretimes histories have been evaluated using the multi-fiber optical probe (MFOP) method which is based on the use of an optical fiber strip, with 64 independent optical fibers. The MFOP allows a quasicontinuous evaluation of the detonation wave run propagation and the assessment of spatial resolved measurements of the shock wave induced in the PMMA barrier. Results of that characterization process are presented and discussed for aluminized an...

Single and two initiation points of PBX

The initiation of PBX based on RDX (85% mass fraction-initial density >95% TMD) induced by single and double initiation points is studied experimentally. A thin 64 optical fibers strip, connected to a fast electronic streak camera allows to observe detonation wave profile and Mach stem zone evolution. The setup is formed by one or two initiation channels with 5 mm square cross section separated, between them, by 15 mm. The optical strips are placed along the wave collision zone and around the initiation point at several circles and different angles θ from channel axis. The results show explicitly the non monotonous (pulsing) behaviour of diverging detonation wave propagation with different velocities in central and periphery zones. At different run distances, the periphery zone (40° 60°). After this transition, the central zone accelerates and overtakes the periphery zone and the detonation front becomes almost spherical. Quantitative results clarify the models o...

Interaction of double corner turning effect in PBX

The corner turning effect in PBX has been studied. The setup built with Cu or PMMA plates, has a channel with a square cross section of 5×5 mm and 10×10 mm, corresponding respectively to 1.33 and 2.67 of PBX failure diameter. A thin optical fibre (250 μm) strip, connected to a fast electronic streak camera, and the printed erosion figure on an witness plate (base plate and internal walls of setup) allows clear quantification of the detonation wave turning phenomena and the printed current lines of the products of detonation. The optical probes allow in real time, an original, direct front observations of multiple zones, by the registration of the interacting waves. Even in the cases of Cu-confinement, the corner turning effect shows the existence of non-detonated PBX (“dark zone”). The correlation between the non-monotonic (x-t) diagrams and light pulsations, recorded during the propagation of detonation wave inside the channels and after the corner section, proves the existence of pulse behaviour and cel...

Failure and re-initiation detonation phenomena in NM/PMMA-GMB mixtures

The addition of a small amount of glass microballoons (GMB) on nitromethane/polymethylmethacrylate (NM/PMMA) mixture reduces strongly the failure thickness and increases the detonation sensitivity. Based in an explosive mixture of NM/PMMA (96/4 by weight) with 1% of GMB (QCel 520 FPS, mean particle diameter of 45 μm), the failure and re-initiation phenomena are investigated experimentally using the corner turning experiments. The printed erosion figure on a polished copper plate, is used as a witness surface. This witness plate not only shows the shock oblique waves but also, around the corner, the re-initiation points and curves. In the dark zone two re-initiation fronts are observed. Two detonation curve fronts can be observed, corresponding to behaviours of homogeneous and heterogeneous explosives. In order to evaluate the influence of shear and normal stress waves, the original set-up has been modified, fixing a thin sheet of a kapton barrier (50 μm thickness) at different angles from the corner. It h...