Laboratory‐Scale Method for Estimating Explosive Performance from Laser‐Induced Shock Waves

Abstract

[a] 1IntroductionThe development and characterizationo fn ew typeso fe xplosive materials designedt op rovide increased performance, improved sensitivityp roperties, and/or reduced toxicity is of interest for military and industrial applications. Reliable experimental measurement of detonation properties remainsc hallenging because of theire xtreme values. Detonation events result in rapid decompositiononananosecond timescale in ac hemicalr eactionz one af ew mm or less in length [1],t emperatures up to 6000 K[ 2],d etonation pressures up to 40 GPa [3],a nd detonation velocities up to 10 km s À1 [3].C ommon diagnostic methods used to measure these parameters includee mbedded pressure gauges, embedded particle velocity gauges, optical pyrometry,l aser interferometric techniques, and streak camera imaging.T he extreme conditions during an explosionr esult in numerous safetyh azards whichi ncrease the time and cost involved in detonation testing to ensure personnel safety.In addition to the challenging experimental conditions, conventional detonationt esting methods require grams of explosive, e.g., the sand [4],f ragmentation [4],l ead block [5],b allistic mortar [4,5],p late dent [ 4,6,7],r ate stick [8], cylinder expansion [ 4,9],m odified aquarium [10],o rd isc acceleration experiments [11].S caling-up the synthesis of new energetic materials to gram quantities is expensive and resource-limited, thus many potential candidate materials are never fully tested.Ap re-screening testc apable of estimating the large-scale detonation performance of energetic materials using only milligram quantities of material would significantly decrease the development time for new explosives.Here, am ethod for estimating the detonationp erformance of milligrams of explosive material based on initiation of the material via ap ulsed laser rather than ad etonative event is demonstrated. The laser pulse is focused on the surfaceo ft he energetic material residue,r esultingi n ablation of the energetic material and the formation of laser-induced plasma. The subsequent plasma emission has been used for both the detection of explosiver esidues [12] and studyingt he high-temperature chemistry of energetic materials [13,14].T he temperature and pressure differential betweent he laser-induced plasma and the surrounding atmosphere also results in the formation of as hock wave which travels through the air normal to the sample surface.Abstract:Anew laboratory-scale methodf or predictinge xplosive performance (e.g.,d etonation velocitya nd pressure) basedo nm illigram quantitieso fm aterial is demonstrated. This technique is based on schlieren imaging of the shock wave generated in air by the formation of al aser-induced plasma on the surface of an energeticm aterial residue. The shock wave from each laser ablatione vent is tracked for more than 100 msu sing ah igh-speed camera.A suite of conventional energetic materials including DNAN, TNT,H NS, TATB, NTO,P ETN, RDX, HMX,a nd CL-20 was used to develop calibration curvesr elatingt he charact...

Improving the Explosive Performance of Aluminum Nanoparticles with Aluminum Iodate Hexahydrate (AIH)

“…In contrast, the TNT-AIH samples resulted in a significant increase in laser-induced shock velocities. Using the calibration fit determined for military explosives 3 , the estimated detonation velocities for the TNT-AIH6 and TNT-AIH15 composite materials are 8.69 ± 0.24 km/s and 9.10 ± 0.26 km/s, respectively (compared to an estimated TNT detonation velocity 3 of 7.03 ± 0.12 km/s).…”

“…The LASEM experimental setup has been described previously 2,3 . Briefly, a 6-ns pulsed Nd:YAG laser (Quantel Brilliant b, 1064 nm, 900 mJ) is focused just below the sample surface with a 10 cm lens.…”

“…The resulting data is fit to a polynomial; the y-intercept of the fit is the characteristic shock velocity for the sample under the given experimental conditions and is used to compare the fast energy release of the materials. For energetic materials, the measured characteristic shock velocity can be used to estimate the detonation velocity of the sample (at the theoretical maximum density) using the previously determined calibration fit 3 . Additional diagnostics for the LASEM setup used in this study included a CCD spectrometer (Ocean Optics USB4000, 200–890 nm, 100-ms integration time) to investigate the chemical reactions of the laser excited material and an infrared-sensitive photodiode (New Focus Model 2053, 900–1700 nm, 10 2 gain) to measure the extent (i.e., peak emission intensity and duration) of the combustion reactions.…”

“…Exothermic reactions were subsequently shown to increase the laser-induced shock wave velocity and/or the laser-induced deflagration reaction following pulsed laser excitation of energetic materials 2 . The strong correlation between the measured laser-induced shock velocities produced by laser ablation of energetic materials and the reported detonation velocities from large-scale detonation tests provides a laboratory-scale method for estimating the fast (i.e., microsecond-timescale) energy release from milligram quantities of energetic materials 3 . The laser-induced air shock from energetic materials (LASEM) technique has recently been used to estimate the detonation velocities of novel energetic materials 4,5 and conventional military explosives doped with Al or boron (B) additives 6 .…”

Review on Promising Insensitive Energetic Materials

“…sensitivity of the materials in realistic situations and at a more reasonable cost than all-up munitions testing. The Swedish Defence Research Agency [18] has developed FOX-7, which attracted considerable attention because of its sensitivity being lower than TATB [19] and its performance being comparable with RDX and HMX [20]. Politzer et al [21] have pointed out that this compound has the same molecular stoichiometry as RDX and HMX.…”