CP620, Shock Compression of Condensed Matter - 2001
edited by M. D. Furnish, N. N. Thadhani, and Y. Horie
© 2002 American Institute of Physics 0-7354-0068-7/02/$ 19.00
DETONATION MESO-SCALE TESTS FOR ENERGETIC MATERIALS
I. Plaksin, J. Campos, J. Ribeiro, R. Mendes, J. Gois,
A. Portugal*, P. Simoes* and L. Pedroso*
Lab. of Energetics and Detonics, Mechanical Eng. Dept. and ^Chemical Eng. Dpt., Fac. of Sciences and
Technology, University ofCoimbra, 3030 Coimbra, Portugal
Abstract. The objective of the present study is to characterize, on the meso-scale level, the detonation
behaviour of PBX based on HMX , based in the minimisation of the test samples of energetic materials
up to 10 mg. The development of a non-intrusive, high resolution, optical metrology procedures, using
multi-fibber strip, allows the testing of PBX micro-samples, formed by few crystals surrounded by
binder, with the simultaneous registration of parameters as local detonation velocity and pressure,
geometrical shape of detonation front and the structure of the shock-to-detonation transition zone. The
enhanced information allows a better understanding of the processes of formation and propagation of
detonation wave. This procedure can be applied to the study of new advanced energetic materials.
developed using the multi-fibber optical technique.
These characteristic tests are: Long Channel Test1"3'6
(V0=0.5 to 1 cm3), with crystal scale resolution;
Conical Tube Test3 (V0 = 0.3 to 1 cm3); Corner
Turning Test1"3'6 (V0 = 1.5 cm3); Colliding Tests4
(V0 = 1.5 cm3); mini-Gap Test3'6 (V0 = 0.5 cm3); pGap Tests3 of crystals, particles and their clusters
(V0 < 2 mm3 m0 < 4 mg).
These tests allow to identify the phenomena of
pulsing detonation, in PBX, as well as the two main
regimes of the unstable DW propagation, in long
explosive charges, namely the quasi-periodical
longitudinal oscillations (of the continuous DF) and
the longitudinal/transversal oscillations (of the
cellular DF) and the limits of the existence of the
two outlined DW regimes. The obtained results
seem to show a strong evidence of the selforganisation establishment in detonation of PBX,
behind the DF, where the reaction instability (in
shocked energetic particles) and the small
fluctuations
(through
the
initial
particleheterogeneities) generate a new regime DW
propagation, rising to a bigger scale instabilities.
The results of the developed p-Gap Test, with
INTRODUCTION
The development of new classes of molecules of
Energetic Materials [EM] needs new metrology
techniques able to test small amounts of EM.
Therefore, to minimise sample sizes, and at the
same time, to optimise the information collected
from each experiment, in order to a deeper
phenomenological study, it was the main present
challenges of present contribution.
The application of multi-fibber optical systems,
developed in LEDAP1"6, gave the first important
results in testing EM (PBX1"4'6 and propellants5)
with mini-samples [m-samples] and micro-samples
[p-samples] formed by the collection of few coarse
crystals surrounded by binder3. It allows the
simultaneous registration of two/three parameters
such as shock and detonation velocity [US,D] and
pressure [Pa], detonation front [DF] curvature, sizes
of the dark zones in the DF corner turning, shockto-detonation transition [SDT] phenomena, and
Mach Wave formation and attenuation processes.
Characteristic tests of m-samples and p-samples,
with typical mass (m0) and volume (V0) less than
2000 mg and 2 cm3, respectively, have been
922
the collection of HMX crystals, and the Coaxial
Double Charge Test, of small PBX samples, are
here presented and discussed, showing the
capabilities of multi-fibber optical technique in
detonation study on the meso-scale level.
(d5o=17 pm) with 47.7% of binder (respectively
inert binder HTPB or energetic binder GAP) in
order to simulate the typical PBX compositions.
Consequently, it was tested simultaneously four
different p-samples of PBX, based on HMX,
representing the collection of two coarse crystals
(HMX or its inert mimic sugar) surrounded by the
mentioned fine HMX crystals (d50 = 17 pm) within
energetic (GAP) or inert (HTPB) binder (p-PBX-1
= HMXcoarse +HMXfine + GAP; p-PBX-2 =
HMXcoarse + HMXfine + HTPB; p-PBX-3 =
Sugar+HMXfine+GAP;
p-PBX-4
Sugar+HMXfine+HTPB).
The photo-chronogram, combined with the photos
of p-PBX-1 to p-PBX-4 samples, is shown in
Figure 2. The streak record shows successively the
initial SW input and output, in the upper 250 pm
Kapton barrier, the light impulses emitted by the
reactive SW during the time ti of its propagation
into the 1.20 mm thick p-PBX specimens, and
finally, the time intervals of the SW crosses of two
Kapton layers placed in the contact with MFOP.
The input pressure evaluated from the mean
velocity, in the upper Kapton barrier is 9.2 Gpa.
The obtained results show, by the enhanced light
radiation emitted by the shock front (Figure 2 and
3), the existence of more intense shock reaction in
p-PBX-1 and p-PBX-3 (with GAP binder) than in
PBX-2 and p-PBX-4 (with HTPB binder). The time
intervals of the shock run tl, for the first pair of
these p-PBX, are 11% less then for the second one,
while the maximum values of shock velocity [Us] in
Kapton are increased of 11%. The relatively low
effect of shock reaction of HMX coarse crystals is
proved by a very small difference, in tl and Us
amplitudes, between samples with coarse HMX
particles and sugar. The differences between pPBX-1 and p-PBX-3 (Figure 3) seem to show the
contribution, in the energy release process, of HMX
coarse crystals surrounded by energetic binder GAP
and HMX fine crystals. The results also show the
bigger effects of the HMX coarse crystals, in the
energy release process, in the case of energetic
binder GAP (p-PBX-1) than in the case of inert
binder HTPB (p-PMX-2), proving previous
predictions and results3.
EXPERIMENTS, RESULTS, DISCUSSION
Recording Optical System
A high resolution optical method1"6 based on 6490 fibbers strip, connected directly to a fast
electronic streak camera (THOMSON-TSN 506 N)
was used for registration of the DW propagation in
PBX mini and p-samples, with a maximum
temporal resolution of 0.6 ns. The main element of
the optical method is a polymeric 64 optic fibber
ribbon, with the diameter of each fibber (as well as
the inter-axis distance between two adjacent fibbers)
equal to 250±lpm. Few variants of Multi-fibber
Optical Probes [MFOP] were developed for the
direct registration of light emitted by shock or
detonation front.
Micro Gap Test
The p-Gap Test of coarse HE crystals,
surrounded by binder, was developed to study the
ignition phase of DW formation, as a function of
binder and size of crystals. Experimental set up is
shown in Figure 1. Four PBX p-samples (collection
of the pairs of coarse crystals, with characteristic
sizes between 540 and 740 pm) were placed in
individual cells and then surrounded by a
composition of 52.3% of the fine HMX crystals
PBX(OB)
'VC
—Kapton (250 jim)
^^Kapton (2x125 urn)
Kapton (250 \im)
y HMX Fine Crystals
within binder, GAP or HTPB
Kapton (2x125 JJJTI)
Coarse HMX or sugar
Fibres
FIGURE 1 - Experimental set-up of u-Gap-Test with the photo
of the multi-fibber optical matrix (MFOP-2) with the collection
of two HMX coarse crystals (u-PBX-2) in its background.
923
(i-PBX-4
mm
p-PBX-3
mm
ji-PBX-2
mm
lOOmg, in combination with the standard PBX. The
idea of CDC Test is based in the surrounding of the
tested PBX p-samples by a PBX ambient charge,
that is large enough, in order to avoid the relief and
decay effects (quenching layer) related to the critical
diameter of detonation. Few CDC Tests
configurations have been developed and applied for
simultaneous registration of D, Pd and DF curvature
in both PBX (PBXX p-sample and surround standard
PBXst). An example of CDC Test is presented, with
PBX composition based on HMX (82% of coarse
crystals, d50=204 um, with 18% of epoxy binder)
with an initial density equal 1.82g/cm3.
Validation of CDC Test implies the correlation
of the DW parameters, D and Pd, of the same PBXX,
measured by two independent tests, with different
sizes of PBXX samples. In CDC Test (Figure 4), usamples have the size 1.9x5x7 mm. In the typical
scale test the sample of the same PBXX, of size of
025 x 30 mm, was initiated by the long charge
(025 x 100 mm) of a standard PBX (PE-4A - initial
density 1.57 g/cm3, 85% of RDX with 15% of a
polyurethane binder). The PBXSt in CDC Test was
the same PE-4A composition.
u-PBX-1
FIGURE 2 - p-photos of PBX p-samples (A=500 jam) and
photo-chronogram obtained in u-Gap-Test.
In compositions with energetic binder GAP, the
local fluctuations of the light irradiation and the
heterogeneities are clearly observed, showing the
formation of the longitudinal/transversal oscillations
in the process of SW propagation.
Kapton (125
Kapton (125^jm x4)—-
^
(0
d.
-•— p-PBX-1
5.00 -i
A
to" 3-°° ~
2.50 -
C
1.50-
"0
LOO-
<; 0.50 -
*^o
o
^
f\
PE-4A 10x22x90
Tested gample: PBX 1,9x5x7mm
(HMX 82 wt% +epQxy wt 48 wt%)
t1 = 24915ns
t1 = 22415ns
v
———r———'o
625Mm
—
-^!!t-^l-PBX-4
[\
§—
"O
nov o
-O-M-PBX-3
E 4-50
-H 4-°° -
t1 = 22915ns
o
t1 =25 015ns
FIGURE 4 - Experimental set-up of CDC Test.
o
{z} Run distance in Kapton (jam)
Us (JJ-PBX-1)
Us (M-PBX-2)
Us (M-PBX-3)
Us ((J-PBX-3)
[mm/ps]
[mm/ps]
[mm/[js]
[mm/jjs]
0.00
0.00
0.00
0.00
0.00
62.50
4.1810.10
3.70 1 0.09
4.2110.11
3.7010.09
187.50
4.2210.11
2.76 1 0.07
3.6610.09
3.1810.08
The photo-chronograms, obtained in CDC and
typical scale tests, are presented in Figure 5. They
show the records of the pulsing DW propagation, in
both tests, fluctuation of light irradiation emitted by
irregular DF and the following run, of the derived
SW with the fluctuations, in the multi-layer Kapton
barrier. The photo-chronogram, obtained in typical
scale test of PBXX, presented in Figure 5 (b), also
shows the derived SW, in the multi-layer Kapton
barrier (consisting of eight Kapton films of
thickness of successively, 100 um, 50 pm and
6x125 pm).
FIGURE 3 - SW attenuation in down Kapton (2x125 um)
barrier.
Coaxial Double Charge Test
Coaxial Double Charge Test (CDC) was
developed for the simultaneous testing of u -samples
of unknown EM, with total mass on the level of
924
the validity of CDC Test, using u -sample mass of
~900 times less the mass of the typical scale test.
CONCLUSIONS
The developed optical non-intrusive methods in
characteristic tests, based on the application of
multi-fibber optical strip, allows the registration of
shock and DW in PBX on the meso-scale level,
providing the observation of the phenomenological
behaviour of PBX detonation. The results obtained
in detonation study of mini and micro samples of
PBX, allow the characterisation of the detonation
process in this strongly non-equilibrium composite
energetic material (coarse HE - fine HE particles binder) as an oscillating interacting process with a
tendency, in its development, to the selforganisation into more regular and a larger scale
process.
(a)
(b)
FIGURE 5 - Photo-chronograms obtained in (a) CDC Test and
in (b) Typical Scale Test.
In both tests, the measured mean values of D (mean
velocity of pulsing DW), Dt (velocity of pulsing
DW in the terminal point of its run, closely to the
PBX-Kapton interface), UsKapton and PKapton (shock
velocity and SW pressure into the Kapton barrier)
and Pd (detonation pressure amplitude) are
presented in Figure 6 and Table 2. Results show, for
both of PBX samples (u-sample and typical scale
sample) an agreement of the measured values of D,
USKapton and Pd, and an inaccuracy, in the measured
values of Dt, that not exceeds the experimental error
of these tests.
REFERENCES
1. L Plaksin, J. Campos, R. Mendes and J. Gois, Interaction of
Double Corner Turning Effect in PBX, Proceedings of the
Conf. on the American Phys. Soc. Topical Group on Shock
Compression of Condensed Matter, Amherst, Massachusetts,
July 27-August 1, 1997, pp. 755-758
2. I. Plaksin, J. Campos, R. Mendes, J. Ribeiro and J. Gois,
Pulsing Behaviour and Corner Turning Effect in PBX,
Proceedings of the llth Detonation Symposium, Aspen, CO,
Aug. 29 - Set. 4,1998, pp. 658-664
3. I. Plaksin, J. Campos, R. Mendes, J. Ribeiro and J. Gois,
Mechanism of Detonation Wave Propagation in PBX with
Energetic Binder, Proceedings of the Conf. of the American
Phys. Soc. Topical Group on Shock Compression of
Condensed Matter, Snowbird, Utah, June 27-July 2, 1999,
pp. 817-820
4. R. Mendes, I. Plaksin, J. Campos and J. Ribeiro, Double
Slapper Initiation of PBX Proceedings of the Conf. of the
American Phys. Soc. Topical Group on Shock Compression
of Condensed Matter, Snowbird, Utah, June 27-July 2, 1999.
pp. 915-918
5. P. Simoes, L. Pedroso, I. Plaksin, J. Campos and A.
Portugal, New Propellant Component: 2. Study of a
PSAN/DNAM/HTPB Based Formulation, Propellants,
Explosives, Pyrotechnics, (in publishing)
6. I. Plaksin, A. Portugal, L. Pedroso, P. Simoes and J.
Campos, Detonation Properties of HMX-DNAM-GAP
Compositions, Abstracts of the International Conference in
Shock Waves in Condensed Matter, St Petersburg,
September 8-13, 2000. pp. 31-33
- Ambient PBX PE4A - Zone A
^^Ambient PBX PE4A - Zone B
-»-PBXx (TS Test)
-*- P B X x |j,-sample
I
^
=i
{z} Run distance in Kapton (jxm)
FIGURE 6 - SW attenuation (USKapton vs z) in Kapton barrier
and Detonation Pressure profiles. All samples are CDC test
except PBXx (as noted)
TABLE 2 - Results obtained in CDC Test and in TS Test.
Test
CDC
CDC
TS
Tested PBX
Ambient
charge PE-4A
PBXX(82%
HMX+epoxy)
PBXX(82%
HMX+epoxy)
UsKapto
D,
Dt,
,um/}i Pd,
urn/us urn/us
GPa
s
7.96
6.04
7.79
1.57
24.2
±0.08 ±0.32 ±0.12
8.64
8.93
6.65
1.82
35.3
±0.09 ±0.36 ±0.13
8.54
8.30
6.88
1.82
35.4
±0.09 ±0.33 ±0.10
A),
g/cc
The correlation between the main parameters of
DW, detonation velocity and detonation pressure,
recorded in CDC and in typical scale tests, proves
925