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Talk Abstract
Experimental Observations Concerning the Mesoscopic Origins of the Low Pressure Thermodynamic Equation of State and High Rate Mechanical Behavior of Plastic Bonded Explosives (Invited)

Joseph C. Foster
.Air Force Research Laboratory/Munitions Directorate
101 W. Eglin AFB FL 32542-6810
fosterjc@eglin.af.mil


Joint work with Joseph G. Glenn of Air Force Research Laboratory/Munitions Directorate, 101 W. Eglin AFB FL 32542-6810. and Mike Gunger of Primex Technology /OTI Group,4565 Commercial Drive, Suite A, Niceville FL 32578.

Energetic materials are broadly classified as primary and secondary explosives based on sensitivity. Secondary explosives represent the largest volume percentage of explosives used in the engineering community.Most modern precision secondary explosives are formulated from a selection of energetic crystalline materials and plastics to create a material that accommodates the performance and sensitivity characteristic of the desired application.The use of these materials in engineering design problems is enabled through modeling their behavior using continuum mechanics based codes.The fidelity of the models employed in the codes depends on the accuracy of the physics and mechanics beginning modeled and the ability to accurately calibrate the model for a reasonable range of materials of interest to the designer.These materials are exposed to a variety of thermal-mechanical loads during their service life.Recent interest has focused research on safety and survivability under conditions that produce long duration, low amplitude loads as compared to the stimuli used to initiate detonation. The interest in the safety problem is on ignition of deflagration rather than initiation of detonation. A fully coupled thermal-mechanical-chemical kinetics representation of the problem is contained in a modified form of the Frank-Kamenetskii equations.2 Experimental techniques have been developed to characterize the low-pressure equation of state 3 and the high-rate mechanical behavior of a representative material. 4 These experiments also represent macroscopic measurements.However,the spatial and temporal scale of the safety problem is very different from that of the initiation problem. Therefore, the scale required for understanding the independence of the thermodynamics and chemical kinetics may be significantly different than classical hot spot initiation theory.

REFERENCES

1. Marsh, S.P., LASL Shock Hugoniot Data, University of California Press. 1980, pp. 591-651 ISBN 0-520LA-04008-2, 1080

2. Joseph C. Foster, Jr., Mechanical Ignition of Combustion in Energetic Materials,1996 Gordon Research Conference on Energetic Materials;New Hampton, New Hampshire, June 1996

3. William C. Davis, HIGH EXPLOSIVES The interaction of chemistry and mechanics in Los Alamos Science, Vol.2 No. 1, Winter/Spring 1981

4. Johnson, J.N., Micromechanical Considerations in Shock Compression of Solids,in High-Pressure Shock Compression of Solids, edited by James R Asay and Mohsen Shahinpoor, Springer-Verlag, New york, 1993

5. F.R. Christopher, J.C. Foster Jr., L.L. Wilson, and H. Gilland,The Use of Impact Techniques to Characterize the High Rate Mechanical properties of Explosives in Proceeding of the 11th International Detonation Symposium edited by James M.Short and James E.Kennedy, p.393, (in press)

6. J.C. Foster, Jr., Joseph Gregory Glenn, L.H. Hull, Michael E.Gunger and Michael A, Galloway, Low Pressure Equation of State Measurements using Piston Test Techniques in Proceeding of the 11th International Detonation Symposium edited by James M.Short and James E.Kennedy, p. 413,(in press)

7. Barderhagen, S.G., Brachbill,J.U.,and Sulsky,D.L. Shear Deformation in Granular Materials,in Proceeding of the 11th Detonation Symposium edited by James M.Short and James E. Kennedy ,(in press) pp. 243-251

8. Foster,Jr., J.C., Christopher, F.R., Wilson,L.L., Osborn, J., ``Mechanical Ignition Of Combustion In Condensed Phase High Explosives," presented at the APS Topical Conference on Shock Compression of Condensed Matter, Amherst, MA, August, 1997.



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