The incidence angle of a detonation wave in a conventional high explosive influences the acceleration and terminal velocity of a metal flyer by increasing the magnitude of the material velocity imparted by the transmitted shock wave as the detonation is tilted towards normal loading. For non-ideal explosives heavily loaded with inert additives, the detonation velocity is typically subsonic relative to the flyer sound speed, leading to shockless accelerations when the detonation is grazing. Further, in a grazing detonation the particles are initially accelerated in the direction of the detonation and only gain velocity normal to the initial orientation of the flyer at later times due to aerodynamic drag as the detonation products expand. If the detonation wave in a non-ideal explosive instead strikes the flyer at normal incidence, a shock is transmitted into the flyer and the first interaction between the particle additives and the flyer occurs due to the imparted material velocity from the passage of the detonation wave. Consequently, the effect of incidence angle and additive properties may play a more prominent role in the flyer acceleration. In the present study we experimentally compared normal detonation loadings to grazing loadings using a 3-mm-thick aluminum slapper to impact-initiate a planar detonation wave in non-ideal explosive-particle admixtures, which subsequently accelerated a second 6.4-mm-thick flyer. Flyer acceleration was measured with heterodyne laser velocimetry (PDV). The explosive mixtures considered were packed beds of glass or steel particles of varying sizes saturated with sensitized nitromethane, and gelled nitromethane mixed with glass microballoons. Results showed that the primary parameter controlling changes in flyer velocity was the presence of a transmitted shock, with additive density and particle size playing only secondary roles. These results are similar to the grazing detonation experiments, however under normal loading the largest, higher density particles yielded the highest terminal flyer velocity, whereas in the grazing experiments the larger, low density particles yielded the highest terminal velocity.

1.
J. E.
Backofen
and
C. A.
Weickert
,
“The effects of plate thickness and explosive properties on projection from the end of a charge
,” in
16ᵗʰ International Symposium on Ballistics
(
San Francisco, CA
,
1996
), pp.
641
650
.
2.
J. E.
Backofen
and
C.
Weickert
,
“Initial free-surface velocities imparted by grazing detonation waves
,” in
Shock Compression of Condensed Matter–1999
,
AIP Conference Proceedings
505
, edited by
M. D.
Furnish
,
M. C.
Chhabildas
, and
R. S.
Hixson
(
American Institute of Physics
,
Snowbird, UT
,
2000
), pp.
919
922
.
3.
J. E.
Backofen
,
“Modeling a material’s instantaneous velocity during acceleration driven by a detonation’s gas push
,” in
Shock Compression of Condensed Matter–2005
,
AIP Conference Proceedings
845
, edited by
M. D.
Furnish
,
M.
Elert
,
T. P.
Russell
, and
C. T.
White
(
American Institute of Physics
,
Baltimore, MD
,
2006
), pp.
936
939
.
4.
J.
Loiseau
,
O. E.
Petel
,
J.
Huneault
,
M.
Serge
,
D. L.
Frost
, and
A. J.
Higgins
,
“Acceleration of plates using non-conventional explosives heavily-loaded with inert materials
,” in
Shock Compression of Condensed Matter–2011
,
Journal of Physics: Conference Series
500
, edited by
W. T.
Buttler
and
W. J.
Evans
(
American Institute of Physics
,
Seattle, WA
,
2014
) p.
182027
.
5.
J.
Loiseau
,
W.
Georges
,
D. L.
Frost
, and
A. J.
Higgins
,
“Acceleration of planar flyers by explosives heavily loaded with inert materials
,” in
Proc. 15ᵗʰ International Symposium on Detonation
, edited by
J. R.
Carney
and
J. L.
Maienschein
(
Office of Naval Research
,
San Francisco, CA
,
2014
), pp.
1381
1391
.
6.
F.
Findik
,
Materials & Design
32
,
1081
1093
(
2011
).
7.
L. L.
Davis
and
L. G.
Hill
,
“Anfo cylinder tests
,” in
Shock Compression of Condensed Matter–2001
,
AIP Conference Proceedings
620
, edited by
M. D.
Furnish
,
N. N.
Thadhani
, and
Y.
Horie
(
American Institute of Physics
,
Atlanta, GA
,
2002
), pp.
165
168
.
8.
M.
Short
and
S. I.
Jackson
,
Combustion and Flame
162
,
1857
1867
(
2015
).
9.
J. T.
Dehn
, “Models of explosively driven metal,” in
Proc. 8ᵗʰ International Symposium on Detonation
, edited by
J. M.
Short
(
Office of Naval Research
,
Albuquerque, NM
,
1985
), pp.
602
612
.
10.
S. I.
Jackson
,
Proceedings of the Combustion Institute
35
,
1997
2004
(
2015
).
11.
S. A.
Sheffield
,
R.
Engelke
, and
R. R.
Alcon
, “In-situ study of the chemically driven flow fields in initiating homogeneous and heterogeneous nitromethane explosives,” (
Office of Naval Research
,
Portland, OR
,
1989
), pp.
39
49
.
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