Numerous experimental investigations reported in the open literature over the past decade have clearly demonstrated that the use of polyurea external coatings and/or inner layers can substantially enhance both the blast resistance (the ability to withstand shock loading) and the ballistic performance (the ability to defeat various high-velocity projectiles such as bullets, fragments, shrapnel, etc. without penetration, excessive deflection or spalling) of buildings, vehicles, combat-helmets, etc. It is also well established that the observed high-performance of polyurea is closely related to its highly complex submicron scale phasesegregated microstructure and the associated microscale phenomena and processes (e.g., viscous energy dissipation at the internal phase boundaries). As higher and higher demands are placed on blast/ballistic survivability of the foregoing structures, a need for the use of the appropriate transient nonlinear dynamics computational analyses and the corresponding design-optimization methods has become ever apparent. A critical aspect of the tools used in these analyses and methods is the availability of an appropriate physically based, high-fidelity material model for polyurea. There are presently several public domain and highly diverse material models for polyurea. In the present work, an attempt is made to critically assess these models as well as the experimental methods and results used in the process of their formulation. Since these models are developed for use in the high-rate loading regime, they are employed in the present work, to generate the appropriate shock-Hugoniot relations. These relations are subsequently compared with their experimental counterparts in order to assess the fidelity of these models.
The present work describes the procedures and results from the first temperature measurements in closed chamber detonations obtained using the thermoluminescence (TL) of particles specifically developed for temperature sensing. Li 2 B 4 O 7 :Ag,Cu (LBO), MgB 4 O 7 :Dy,Li (MBO) and CaSO 4 :Ce,Tb (CSO) were tested separately in a total of 12 independent detonations using a closed detonation chamber at the Naval Surface Warfare Center Indian Head Explosive Ordnance Disposal Technology Division (NSWC IHEODTD). Detonations were carried out using two different explosives: a high temperature plastic bonded explosive (HPBX) and a low temperature plastic bonded explosive (LPBX). The LPBX and HPBX charges produced temperatures experienced by the TL particles to be between ~550-670 K and ~700-780 K, respectively, depending on the shot. The measured temperatures were reproducible and typically higher than the thermocouple temperatures. These tests demonstrate the survivability of the TL materials and the ability to obtain temperature estimates in realistic conditions, indicating that TL may represent a reliable way of estimating the temperature experienced by free-flowing particles inside an opaque post-detonation fireball.
Abstract. We previously developed and tested thermally sensitive particles that, when seeded into an explosive event, flow with the expanding post-detonation fireball and provide ex-situ measurements of this thermal environment. This current work presents the development and testing of tracking particles that are used in concert with the thermally sensitive particles to encode the initial positions of materials recovered for ex-situ analysis. These tracking sensors consist of fully-crystallized (c)
] 1IntroductionBacterial spores such as Bacillus anthracis (anthrax) are potentially highly dangerous to human health, see for example Whitney et al. [1].E nergetic materials offer ap otential for rapid neutralization of such threats in operational environments since detonation and combustion can produce hot and in some cases corrosiveg ases, whichh ave ab iocidal effect.R ecent work by McCartt,G ates, and co-workers [2-4] and references cited therein has studied spore resistance to gasdynamic heating using aerosolized spores suspended in as hock tube and finds that significant neutralization occurs at temperatures above 650 K. Significant endospore damage is observed at temperatures above 750 K. Gottiparthi et al. [5] have built on the above data in numerical studies of neutralization of spores in post-detonation (using nitromethane as the explosive) free-field flows. There they considerasimple neutralization model where spores are neutralized if their temperature exceeds ac ritical temperature, which they take to be 670 K. Schulz et al. [6] have carried out systematic sensitivity studies basedo nt his modeling techniquea nd conclude that the residence time in the hot gases is ad ominant parameter.In our workw ec onsider detonation in an enclosed environment, where residence times are naturally much longer than in free field. The energetic material studied is Valimet H-2 aluminum powder,s hock dispersed by detonation of ac entral high explosive( HE) core. The experimental apparatus consists of two coupled closed chambers. The first chamber contains the energeticm aterial and is initially filled with Bacillust huringiensis Al Hakam (BtAH) sporesi n an aerosol. On detonation, the gasesa re free to vent into the second (exhaust) chamber, simulating venting from as tructure damaged by ab io-agent defeat strike. After the event, spores are captured from both chambers for postprocessing to determine the fraction remainingv iable. The primary diagnosticsa re the conditions in the detonation chamber and the resultingp ercentage of surviving spores.We also report the results of ar ange of numerical modeling studiesc arried out to aid the interpretation of these ex- Abstract:T his paper reports an experimental and modelling study of the biocidal effect of an energeticm ixture which is detonated in ac losed chamber containing an initial spore distribution. The resulting spore neutralization efficiency is recorded as af unctiono fm easuredd etonation and combustion performance. We also report the results of ar ange of numerical modelling studies carried out to aid the interpretation of these experiments and to guide future developments. We find that the current energetic mixture (aluminum powder whichi ss hock dispersed by detonation of ac entralh igh explosivec ore)g ives variable combustion efficiency.T he Al powder ignites on impact with the walls. In the modelling we matcht he recorded quasi-static pressures in each experiment and compare predicteds pore neutralization with measured values. Using ac riticals pore tempe...
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