Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session K2: Energetic Materials IV |
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Chair: William Proud, University of Cambridge Room: Hyatt Regency Constellation C |
Tuesday, August 2, 2005 1:30PM - 1:45PM |
K2.00001: Adhesion studies between HMX and EDC37 binder system David Williamson, Stewart Palmer, William Proud EDC37 is a PBX which is composed of 91{\%} HMX and 9{\%} NC/K10 by weight. Previous studies have shown that damage under quasi-static conditions occurs preferentially via the adhesive failure of the HMX/ binder interface. Single crystals of HMX have been grown for use in an idealized experiment in which HMX/ binder joints are broken in a simple tension geometry instrumented with a load-cell of millinewton sensitivity. The aim is to quantitatively assess the parameters involved in this important failure mode. Such data are required for the development and validation of accurate microstructural models of PBXs. This paper outlines the current state of research and details the important observations to date. [Preview Abstract] |
Tuesday, August 2, 2005 1:45PM - 2:00PM |
K2.00002: Fracture studies of three PBX mock materials Stewart Palmer, David Williamson, William Proud Fracture studies have been performed on three mock PBX materials; PBS 9501 which consists of sugar bound in Estane and is a mock of PBX 9501. EDC1037 and EDC1032 which consist of barium sulphate and melamine bound in NC/K10 and Viton-A respectively, and are mocks to EDC37 and EDC32. The effect of microstructure, geometry and testing rate are investigated, and the applicability of elastic-plastic fracture mechanics is considered. Such data are required for the development and validation of accurate models of PBX failure. This paper outlines the current state of research and details the important observations to date. [Preview Abstract] |
Tuesday, August 2, 2005 2:00PM - 2:15PM |
K2.00003: High strain rate characterisation of a Polymer Bonded Sugar Stephen Grantham, Clive Siviour, Phillip Church, Peter Gould, William Proud The mechanical properties of a polymer bonded sugar consisting of sugar crystals dispersed in an HTPB binder have been measured in a split Hopkinson pressure bar system at temperatures from +20 down to --100 \r{ }C. These experiments were supported by further tests in an Instron and DMTA apparatus. The behaviour of this material is compared to that of other polymer bonded explosives and their simulants. A major advance in these experiments was the use of X-ray tomography to examine undeformed and deformed specimens, and to qualify and quantify the damage mechanisms in this material. [Preview Abstract] |
Tuesday, August 2, 2005 2:15PM - 2:30PM |
K2.00004: Comparison of the Influence of Temperature on the High Strain Rate Mechanical Responses of EDC37 and PBX 9501 R.K. Govier, G.T. Gray III, W.R. Blumenthal For the plastic bonded explosive PBX9501, many high strain rate compression measurements have been reported using a specially designed Split Hopkinson Pressure Bar. In contrast, limited amount of data exists for the UK PBX, EDC37. The binder system for each PBX is very different; EDC37 contains a nitro-plasticised nitrocellulose, whilst PBX9501 contains a nitro-plasticised Estane. It is widely believed that the mechanical responses depend strongly on the binder, and evidence for this is presented in this paper. Both PBXs exhibit an increasing elastic loading moduli, E, with increasing strain rate or decreasing temperature, behaviour which is similar to other polymeric composite materials. PBX 9501 exhibited nearly invariant fracture strains of $\sim $1.5{\%} as a function of temperature at high strain rate. EDC37 also displayed an invariant peak strain to failure of $\sim $2-2.5{\%}. Maximum compressive strengths for both PBXs were measured at 150MPa at -55\r{ }C. However, at 55\r{ }C PBX9501 was found to be stronger than EDC37, with maximum compressive strengths of $\sim $55MPa and$\sim $20MPa respectively. [Preview Abstract] |
Tuesday, August 2, 2005 2:30PM - 2:45PM |
K2.00005: SANS and Contrast Variation Measurement of the Different Contributions to the Total Surface Area in PBX 9501 as a Function of Pressing Intensity Joseph Mang, Rex Hjelm We have used small-angle neutron scattering (SANS) with the method of contrast variation to measure the surface area (S$_{HB} $, S$_{HV}$ and S$_{BV}$) associated with the three interfaces (HMX-binder(HB), HMX-voids(HV) and binder-voids(BV)) in pressed pellets of PBX 9501. These interfaces are of interest as they may influence the transmission of microstresses under shock conditions. Because of the difficulty in making measurements, little is known about the microstructure of pressed PBX 9501 parts and thus how it is affected by processing. Here, we explore the effect of varying the pressing intensity on the PBX 9501 microstructure and in particular how the three interfaces are affected. Disk-shaped samples of PBX 9501 were die-pressed with applied pressures ranging between 5,000 - 29,000 psi. SANS measurements were performed, on the LOW-Q Diffractometer at the Manuel Lujan Jr. Neutron Scattering Center, on 4 - 5 pellets at each pressure. Analysis of the SANS data indicates systematic changes in S$_{HB}$, S$_{HV}$ and S$_{BV}$ with applied pressure. Our ability to measure the different contributions to the total surface area is novel for this system and future measurements will aid in the development of full-scale constitutive models for both pristine and damaged high explosive materials. [Preview Abstract] |
Tuesday, August 2, 2005 2:45PM - 3:00PM |
K2.00006: The Strength of Plastic Bonded Explosives as a Function of Pressure, Strain Rate and Temperature Donald Wiegand, Brett Reddingius Measurements as a function of strain rate and temperature have indicated the importance of the polymer binder in determining the strength of plastic bonded explosives at ambient conditions and low strain rate. Recent measurements of strength as a function of pressure further support this conclusion. As pressure or strain rate are increased or temperature is decreased the strength increases as does the strength of many polymers. In addition, at relatively large values of pressure or strain rate and/or relatively low values of temperature the strength is less sensitive to changes of these quantities. These trends suggest that as the polymer binder becomes stronger with increasing pressure or strain rate or with decreasing temperature, the strength of the explosive component of these composites becomes more important in determining the strength of the composite. Results will be presented for plastic bonded explosives, e.g., LX-14, that demonstrate these trends as a function of pressure, strain rate and temperature. [Preview Abstract] |
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