Hydroxy-terminated polybutadiene (HTPB) is commonly used as a binder system in rocket propellants and plastic bonded explosives (PBXs). As such, the investigation of this material under high-strain-rate and shock-loading conditions is of importance if the response of propellants and PBXs is to be understood. Therefore, the Hugoniot of two different HTPB compositions has been investigated, using manganin stress gauges. Both materials have a linear Us–up relationship, with the material having a higher plasticizer content having a lower value of c0. It has been suggested that additions of plasticizer increase the compliance of the material. In addition, in one composition, shock recovery experiments have been performed. Results indicate that no changes in glass transition temperature, decomposition temperature, or molecular weight occur in the range of shock stresses investigated.
Publicly available video recordings of the explosion in Beirut on August 4, 2020, were examined and from them it was possible, in conjunction with the well‐known Google Maps website, to obtain estimates for the locations of the observers’ cameras with respect to the blast, and estimates for the blast wave arrival time. A publicly‐available blast wave calculator was then used to estimate the size of the explosion in terms of the equivalent quantity of TNT that would produce the same blast wave arrival time at the observers’ distance. This work estimates the Beirut explosion to have been equivalent to 637 tons TNT, with a lower bound estimate of 407 tons and an upper bound estimate of 936 tons.
The effect of particle size on the shock response of three soda-lime glass-hydroxyterminated polybutadiene composites has been investigated. While the shock velocity–particle velocity relationship has been shown to be nearly identical in all three materials, thus indicating that the hydrodynamic response is particle size independent, the shock stresses have been shown to be strongly dependent upon particle size. It has been proposed that this be due to the nature of the microstructure, with the larger particles restricting flow, and thus increasing shear strength, while the finer microstructure can flow as a whole.
Smart fluids in the form of electro-rheological (ER) fluids are among the most spectacular of the smart materials. ER fluids are typically suspensions of semiconducting, solid particles dispersed in an insulating carrier liquid, which show a dramatic increase in flow resistance when an external electric field is applied. This reversible and rapid change in flow properties has potential applications in many electronically controlled mechanical devices. This article gives a short overview of the field of ER materials and their basic properties. Current and future developments with particular attention to electrorheological polymers have been reviewed.
Currents drawn under high fields often present practical limitations to electrorheological (ER) fluids usefulness. For heavy-duty applications where large torques have to be transmitted, the power consumption of a ER fluid can be considerable, and for such uses a current density of ~100 uA cm" 2 is often taken as a practical upper limit. This investigation was conducted into designing a fluid which has little extraneous conductance and therefore would demand less current.Selected semi-conducting polymers provide effective substrates for ER fluids. Such polymers are soft insoluble powdery materials with densities similar to dispersing agents used in ER formulations. Polyaniline is a semi-conducting polymer and can be used as an effective ER substrate in its emeraldine base form. In order to provide an effective ER fluid which requires less current polyaniline was coated with an insulating polymer. The conditions for coating was established for lauryl and methyl methacrylate. Results from static yield measurements indicate that ER fluids containing coated polyaniline required less current than uncoated polyaniline ie 0.5 uA cm" 2 . The generic type of coating was also found to be important.
IntroductionElectrorheology 1 " 4 (ER) is the study of the effect of an applied electric field on the flow of matter. The positive electrorheological effect concerns the rapid and reversible change in the viscosity of a suspension due to the application of an electric field, and an accompanying change in the suspension structure from an initially random distribution of particles to a more ordered structure of fibrils which span the electrode gap. Suspensions displaying these characteristics are usually non-aqueous and composed of polarisable particles suspended in an insulating medium. Conventional fluids have required the active substrate to be moist to create an ER effect. However, the presence of water causes a number of problems notably excessive electrical power dissipation causing heating and further increasing the currents drawn, loss of ER effect due to evaporation when under load, and inherent problems of using aqueous systems and high tension power sources. More recently ER fluids have been developed which do not require water as a promoter, 1931 Int. J. Mod. Phys. B 1999.13:1931-1939. Downloaded from www.worldscientific.com by YALE UNIVERSITY on 07/01/15. For personal use only.
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