DETONATION AND COMBUSTION OF NEW HETEROGENEOUS COMPOSITE EXPLOSIVES CONTAINING ALUMINUM PARTICLES

XIth
INTERNATIONAL ARMAMENT CONFERENCE
ON SCIENTIFIC ASPECTS OF ARMAMENT AND SAFETY TECHNOLOGY
Detonation and combustion of new heterogeneous
composite explosives containing aluminum particles
Lotfi MAIZ*, Waldemar A. TRZCIŃSKI
Military University of Technology – Kaliskiego2, 00-908 Warsaw, Poland,
*
corresponding author, e-mail: lotfi.maiz@wat.edu.pl
Abstract. A new class of energetic composites with enhanced blast and combustion
characteristics are investigated. The slurry method for preparation of two types of these
granular RDX-based composites is shortly described. Optical characterisation of the
composites confirmed the macroscopic structure of the granules. Sensitivity of the
composites and compatibility of their components are tested. Confined and semi-closed
explosions of cylindrical pressed and layered charges containing the composites are
investigated. For comparison, charges of TNT and phlegmatized RDX (RDXph) are
also studied. The effect of the type of the granular composite, the charge form
(cylindrical pressed or layered charges), oxygen availability (air or argon atmosphere)
and the aluminium particle size on various blast and explosion parameters including
fireball temperatures were determined. The analysis of all results enables us to draw
conclusions about the aluminium combustion during the explosion of composite
thermobaric and enhanced blast explosives.
Keywords: TBXs, EBXs, composite explosives, confined explosion, semi-confined
explosion
1. INTRODUCTION
The first source of energy during explosion comes from the detonation.
Later, depending on the explosive and explosion conditions, more or less energy
can be available and could be released during the afterburning process of
unreacted carbon, carbon monoxide and hydrogen contained in the detonation

L Maiz, W A. Trzciński2
products [1]. To increase the heat effect, chemically active metals mainly
aluminium and magnesium are added to condensed explosives. Their
combustion energy is three to five times higher comparing to detonation energy
of classical explosives. Despite the combustion rate is not fast enough to enable
these metals to take part in the reactions in the detonation zone, they may react
with detonation products of the explosion and oxygen from air and significantly
increase the explosion energy [2]. When detonated in closed spaces shock wave
reflections and mixing of the metallic fuel with detonation products and air
enhance more the afterburning reactions. Thermobaric explosives (TBXs) and
enhanced blast explosives (EBXs) belong to this type of explosive formulations.
They are fuel-enriched heterogeneous explosive formulations with high
destructive ability and thermal effects. These effects are enhanced in closed and
semi-closed spaces and they are weapons of first choice for this kind of targets
[2,3,4]. However; the major problem with this kind of heterogeneous metalized
formulations is that only part of the available energy from the combustion of the
metallic fuel is used effectively during the explosion. Recently, new composites
in form of macroscopic multi-components energetic granules are reported in US
patents to have the best combustion efficiency of the metallic fuel, this may
probably enhance their blast and explosion characteristics [5-9]; however, no
data are available in the existing literature concerning the investigation of such
composites.
A new class of energetic composites with high blast and explosion
parameters is investigated in the present work. These composites are in a form
of macroscopic granules and are obtained using a new slurry process called
“wet method‟‟. These composites are considered as thermobarics when used in
layered charges or enhanced blast explosives when pressed. Confined and semi-
closed explosions of cylindrical pressed and layered charges containing the
prepared composites are investigated and compared to explosions of charges
made from simple mixtures and classical high explosives. The presented results
of investigations include also measurements of fireball temperatures by the
mean of optical spectroscopy. This may be an important contribution for the
existing literature since this parameter is a major metric especially for
volumetric explosives but unfortunately very difficult and often omitted by
explosives community.
2. MATERIALS AND METHODS
2.1.Preparation and characterization of the composite materials
Large macroscopic particles were prepared using the “wet method” [4].
The wet method is a safe, low cost and non-polluting slurry process for
obtaining a new class of energetic composite molding granules. Each granule is
a complete multi-components energetic macroscopic composite, homogeneous

Detonation and combustion of new composite explosive 3
or with granular core-shell structures, comprising a number of crystals of a high
explosive, an oxidizer and a metallic fuel, the whole is coated and consolidated
by a binder. Two kinds of these macroscopic granules were prepared. Each kind
of contains cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) as a high
explosive powder, ammonium perchlorate (AP) as an oxidizer, aluminium (Al)
as a metallic fuel, Viton (copolymer of vinyliden fluoride and
perfluropropylene) as a binder. Crystalline AP with particle sizes bellow 0.8
mm and two types of aluminium powder were used. The first type Al1 with
particles size bellow 44 µm (325 mesh) and the second Al2 with particle sizes
between 44 and 149 µm (325 to 100 mesh). The first type of granules has
homogeneous structure and symbolized by the letter A in Figure 1. The second
type is denoted by B in Figure 1 and has a core-shell structure. The core
comprises a mixture of AP with Al powder consolidated by Viton and the whole
is surrounded by an explosive shell.
Fig. 1. Structures of the macroscopic multi-components granules prepared by the wet
method: A-homogeneous configuration, B-core-shell configuration
During the wet slurry method process, Viton as a binder was dissolved in
ethyl acetate as a solvent. RDX, AP and aluminium particles were put into this
lacquer solution and properly mixed. The macroscopic granules start to form
due to the slow dropwise addition of an anti-solvent. Later, a carrier thermally
stable fluid (pharmaceutical paraffin) is added to gradually evaporate both the
solvent and the anti-solvent. The wet method needs to be conducted under
optimal conditions to obtain homogeneity in granules size, uniformity in coating
and high yield. In both A and B configurations, the obtained granules are
spherically shaped with a diameter ranging from 1.1 to 1.6 mm. Mass
percentage of each ingredient in the composite (granule) is listed in Table 1.
Exemplary photos of the granules are shown in Figures 2 and 3. A complete
consolidation of the particles and high welding by the binder produces very low
voids or cleaved surfaces in the case of the granules of 21-A. More internal
voids are observed in the 21-B granules due probably to the large diameter of
the RDX particles. Analysis of SEM pictures of the 21-B granules and their
cross sections showed that granules with a core-shell morphology were

obtained. The AP-Al-Viton core is surrounded by RDX grains consolidated by
Viton.
Table 1. Compositions of the prepared macroscopic multi-components granules
Structure Configuration A Configuration B
Granule name 11-A 12-A 21-A 22-A 11-B 21-B
Ingredients Composition (wt.%)
RDX (crystalline) 50 18.2 50 18.2 50 50
NH4ClO4 (AP) 10 18.2 10 18.2 10 10
Al1 30 54.5 - - 30 -
Al2 - - 30 54.5 - 30
Viton (binder) 10 9.1 10 9.1 10 10
(a) (b)
Fig. 2. Optical microscope picture (a) and SEM image (b) of composite granules 21-A
(a) (b)
Fig. 3. Optical microscope picture (a) and SEM image (b) of composite granules 21-B
For comparative studies, mixtures of components were also prepared and
named C (Table 2). Each component was phegmatized separately using the wet
method. The amount of binder (Viton) for each component was chosen to be
proportional to each component contents percent that the final mixture had the
same mass composition as formulations A from Table 1.

Table 2. Compositions of the mixtures
Mixture name 11-C 12-C 21-C 22-C
Ingredients Compositions [wt.%]
RDX (crystalline) 50 18.2 50 18.2
NH4ClO4 (AP) 10 18.2 10 18.2
Al1 30 54.5 - -
Al2 - - 30 54.5
Viton (Binder) 10 9.1 10 9.1
Compatibility of components composing the composites and the mixtures
was studied using TG/DTA analysis. Exemplary thermograms of composites A
are shown in Figure 4. All thermolysis phenomena of all compositions start in a
temperature range almost same such as RDXc (RDX crystalline). For
compositions containing 50% of RDX, the nature of thermograms are similar to
that of crystalline RDX, since the thermal degradation occurring in a single
rapid step. Samples containing 18.17% of RDX (12-A, 22-A, 12-C, 22-C) show
a shoulder after the first mass lose, indicating a second thermal decomposition.
Fig. 4. Exemplary TG/DTA curves for RDXc and macroscopic composites A
Sensitivity tests were also performed and results were compared to that of
RDX phlegmatized with 6% of wax. Sensitivity to impact was determined using
a BAM apparatus with 5 kg hammer. The highest impact energy at which no
reaction took place in six consecutive trials was determined. The friction
sensitivity was determined by a Julius-Peters apparatus. In this test, the value of
the minimum force of friction was determined at which at least one reaction was
recorded in six consecutive trials. The results are shown in Table 3. All
compositions show more or less similarity to RDXph in both impact and
friction sensitivity tests, however, small differences were recorded in sensitivity
to friction in case of mixture compositions (TBX-C). This means that an

improvement in friction and impact sensitivity was introduced in these
composites, which concords with the optical microscopy and SEM
observations.
Table 3. Table summarizing sensitivity tests
Composition Sensitivity to impact [J] Sensitivity to friction [N]
11-A 6.5 200
12-A 7.5 200
21-A 6 160
22-A 8.5 175
11-B 6 175
21-B 6.5 160
11-C 5 140
12-C 7 200
21-C 5.5 140
22-C 6.5 140
RDXph 7 180
2.2.Preparation and characteristics of the charges
To investigate the influence of charge type, aluminium particle size and
configuration of the composites (structures A, B or mixture C) on the blast and
explosion parameters in a confined and semi-closed explosions, two kinds
(layered and pressed) cylindrical charges containing the different composites
were prepared. All composites and mixtures containing 50% of RDX in
configurations A, B and C were pressed using a hydraulic press into cylindrical
pellets. This type of charges is named hereafter as pressed charges TBX-x1-a,
where symbol x denotes a type of aluminium (1 – fine Al or 2 – coarse Al) and
symbol a corresponds to a type of composite configuration or mixture (A, B or
C) – Table 4. A cross section of a pressed charge is shown in Figure 5. The
second kind of charge is described in Table 5 and Figure 6. The cylindrical
layered charge consists of a core and an external layer. The core is composed
from two cylindrical pellets of RDX phlegmatized by 6 wt.% of wax (RDXph).
This type of charges is named hereafter as layered charges TBX-x2-a, where
symbol x denotes a type of aluminium (1 or 2) and symbol a corresponds to a
type of composite configuration or a mixture (A or C) – Table 5. For
comparison, tests were also carried with pressed TNT (trinitrotoluene, 1.53
g/cm3) and pure RDXph. Charges were investigated firstly in a small explosion
chamber, weight of each charge was 43 g, the diameter d of the pressed charges
was 25 mm, the core of the layered charges had a diameter d of 16 mm and an

external diameter D of 30 mm. The charges used in a semi-closed bunker were
247 g weight. The diameter d of the pressed charges was 50 mm. Layered
charges had the core of 30 mm and external diameter 50 mm.
Fig. 5. Schematic of the investigated
pressed charge: 1 –
composite, 2 – detonator
Fig. 6. Schematic of the investigated
layered charge: 1 – RDXph
core, 2 – composite, 3 – paper
tube, 4 – detonator
Table 4. Characteristics of cylindrical pressed charges
Symbol TBX-
11-A
TBX-
21-A
TBX-
11-B
TBX-
21-B
TBX-
11-C
TBX-
21-C
Mass (g) 43 43 43 43 43 43
Density (g/cm3
) 1.87 1.90 1.73 1.74 1.76 1.79
Diameter (mm) 25 25 25 25 25 25
Composite or
mixture
11-A 21-A 11-B 21-B 11-C 21-C
Table 5. Characteristics of cylindrical layered charges
Symbol TBX-12-A TBX-22-A TBX-12-C TBX-22-C
Mass (g) 18.3/24.7 (core/layer) 18.3/24.7 18.3/24.7 18.3/24.7
Density (g/cm3
) 1.69/1.23 (core/layer) 1.69/1.23 1.69/1.21 1.69/1.22
Diameter (mm) 16/30 (core/layer) 16/30 16/30 16/30
Composite or mixture 12-A 22-A 12-C 22-C
2.3. Experimental site
Confined explosions investigations were carried in a small closed
explosion chamber of 0.15 m3 volume. Dimensions of the explosion chamber
are shown in Figure 7. A charge was hung in the center of the chamber and a

standard fuse was used to initiate detonation. An electrical standard detonator
was enough to detonate all layered charges and TBX-A charges, however, a
booster consisting of 5 g of pressed RDXph was necessary to initiate the
detonation of TBX-B charges and homogeneous TBX-C charges. Primary tests
were carried in air atmosphere under normal pressure of about 0.1 MPa and at
ambient temperature. Then four types of charges were selected for further tests
in argon under the same conditions. In both atmospheres, air and argon, at least
three tests were performed for each investigated charge. Signals of overpressure
from two piezoelectric gauges (PCB Electronics, Inc.) located at the chamber
wall were recorded by a digital storage scope. Light from the fireball was
collected and sent through a fiber optic cable to the spectrometer. This latter
was connected via a USB cable to a computer, and data acquisition was handled
using the manufacturer software.
Experiments with larger charges were performed in a semi-closed bunker.
A schematic, charges location and the different measuring gauges are shown in
Figure 8. The bunker has a volume of about 40 m3
with four 0.05 m2
small
openings and a 1.3 m2
frontage opened door. Tested charges were placed 1.7 m
above the ground, an electrical standard detonator was used to initiate
detonation for all charges. Also, at least three tests were performed for each
investigated charge. For each shot; Pressure histories were recorded at 2m and
2.5m from the center of the charge, one light intensity history was collected by
the photodiode and a spectrum was recorded by the spectrometer.
Fig. 7. Schematic of the 0.15
m3 explosive chamber (side
view): 1 – explosive charge, 2
– pressure gauges, 3 – optical
fiber
Fig. 8. Schematic of the 40 m3 semi-closed bunker
(side view): 1 – explosive charge, 2 – fiber optic
sensor, 3 – pressure gauges, 4 – photodiode

3. RESULTS AND DISCUSSION
3.1. Confined explosion investigations
3.1.1. Quasi-static pressure results in air atmosphere
Overpressure history records have oscillating nature. eq. (1) was used for
overpressure history approximation.
∆Papp=c∙exp-dt
+ a∙(1-exp-bt
) (1)
Where a, b, c and d are constants. Exemplary overpressure histories
recorded for some charges as well as their approximations are shown in Figure
9. Function (1) reaches a maximum value pmax for a time tmax (eq. (2))
tmax=Ln(a∙b/c∙d)∙(1/(b-d)) (2)
Thermochemical calculations were also made to estimate the final
overpressure in the chamber. CHEETAH code with modified library was used
for this purpose with the set of values of the BKW parameters: α=0.50, β=0.40,
κ=10.86 and ϴ=5441 [10]. Theoretical calculations were made with an
assumption of aluminium reaction with gases inside the chamber (pcal) and
also for inert aluminium (pinr). The constant volume explosion state was
determined for an explosive charge and air or argon closed in the chamber. The
fuse explosive (PETN) was included in the calculation. Values of pmax (QSP)
with standard deviations determined on the basis of at least six overpressure
histories recorded in chamber filled with air and pcal obtained from
thermochemical calculations are summarized in Table 6 for all tested charges.
Fig. 9. Exemplary overpressure histories recorded for RDXph core and TBX-22-A
charges in air atmosphere

Table 6. Values of the maximum overpressure measured in air atmosphere and
calculated by CHEETAH code
Charge
pmax
[MPa]
pcal
[MPa]
pmax/pcal
[%]
pmax/pRDX core
[%]
pinr
[MPa]
TBX-11-A 0.79±0.02 0.98 80.61 - 0.50
TBX-12-A 0.77±0.03 0.98 78.57 2.08 0.50
TBX-21-A 0.76±0.04 0.98 77.55 - 0.50
TBX-22-A 0.79±0.08 0.98 80.61 2.14 0.50
TBX-11-B 0.82±0.06 1.04 78.85 - 0.56
TBX-21-B 0.78±0.03 1.04 75.00 - 0.56
TBX-11-C 0.80±0.03 1.04 76.92 - 0.56
TBX-12-C 0.74±0.02 0.98 75.51 2.00 0.50
TBX-21-C 0.78±0.06 1.04 75.00 - 0.56
TBX-22-C 0.80±0.07 0.98 81.63 2.16 0.50
TNT 0.75±0.06 1.03 72.82 - -
RDXph 0.70±0.01 0.92 76.09 - -
RDXph (core) 0.37±0.03 0.47 78.72 1 -
Analysis of the data in Table 6 shows that all values of pmax are lower than
the calculated pcal for all charges. QSP values of aluminized charges are lower
than theoretical ones if it is assumed that all aluminium reacts but significantly
higher than those calculated under the assumption of thermochemical
equilibrium and non-reactivity of aluminium particles. Moreover, all maximum
overpressures measured for aluminized charges are superior than those of TNT
or RDXph. This indicates that aluminium from the compositions reacts with
detonation products or/and air in the explosion chamber resulting in an
additional heat which increases temperature and pressure of the gaseous
mixture. When applied to the RDXph core, the cylindrical rich-fuel layer
increases at least twice the value of the overpressure. Aluminium powder size,
charge type and composite structures (A, B or mixtures C) affect the ratio of the
measured maximum overpressure and the calculated average
pressurepmax/pcal. In fact, pressed charges with small aluminium particle size
have this ratio higher than pressed charges with larger aluminium particle size
and inverse tendency is observed in the case of layered charges. If it comes to
comparison between pressed and layered charges, obviously, the pressed
charges are better than the layered ones for small aluminium particles but worse
for larger aluminium particles. These ascertainment is valid for the A
composites and also the C mixtures. Concerning the composite granular
structure effect, it is observed that the overpressure ratio is superior for charges
containing composite A than B than mixture C for all aluminized charges. This
order is also preserved in case of smaller aluminium particles (except the
composition TBX-22-C) or larger particle size. Unlike our expectations, the
outer RDX-viton shell surrounding the Al-AP core in the macro fragments B
did not have an enhancing effect on aluminium combustion.

3.1.2. Quasi-static pressure results in argon atmosphere
To investigate the detonation and explosion of aluminized charges in absence of
oxygen (air), further tests were carried out in the chamber filled with argon
atmosphere. These tests allowed us to determinate the contribution of the
anaerobic reactions of aluminium particles in the overpressure history inside the
explosion chamber after comparing them with tests in air. The compositions
TBX-A were selected for these trials. Eq.(1) was used to determine the
maximum overpressure inside the chamber. Theoretical calculations were
performed with the assumption of reaction of aluminium with hot detonation
gases and for inert aluminium. Average QSP or pmax of all TBX-A charges,
TNT and RDXph charges measured in argon are summarized in Table 7. The
parameter of pO-Ar is the difference in values of maximum overpressure
determined experimentally in air and argon. Concerning aluminized charges in
argon, the values of the maximum average overpressure are smaller than those
in air because of the absence of oxygen from the latter. It means that aerobic
reactions of aluminium take place in in the chamber filled with air and they lead
to the liberation of additional heat and the overpressure increases. However, the
QSP values in the chamber filled with argon are higher than pinr which means
that aluminium also takes part in the anaerobic afterburning reactions with the
hot detonation products.
Table 7. Values of the maximum overpressure measured in argon atmosphere and
calculated by CHEETAH code for TBX-A, TNT and RDXph charges
Charge
pmax
[MPa]
pcal
[MPa]
pmax/pcal
[%]
pinr
[MPa]
pO-Ar
[MPa]
TBX-11-A 0.66±0.06 0.96 68.75 0.47 0.13
TBX-12-A 0.60±0.02 0.96 62.50 0.47 0.17
TBX-21-A 0.69±0.04 0.96 71.88 0.47 0.07
TBX-22-A 0.61±0.02 0.96 63.54 0.47 0.18
TNT 0.52±0.05 0.47 110.64 - 0.23
RDXph 0.52±0.05 0.70 74.29 - 0.18
It is clear that in absence of oxygen from air, the pressed charges have higher
values of QSP than the layered ones. Moreover, pO-Ar for the pressed charges
are lower than pO-Ar for layered charges especially for TBX-21-A. It
demonstrates that the pressed charges can be considered as enhanced blast
explosives (EBXs). In the layered charges, pO-Ar is high, which means that
unlike the pressed charges, the explosion of the layered charges promote aerobic
afterburning reactions of aluminium, since they are thermobarics. The value of
pcal determined experimentally for TNT charges under argon atmosphere is
similar to that of RDXph. Moreover, it is unexpectedly higher than the
theoretical one. This could be attributed to the detonation products equilibrium

in the presence of argon during the explosion, argon acts as a diluent and also as
a physical barrier between the different chemical species inside the chamber
[11-15].
3.1.3. Fireball temperature history results
Fireballs temperatures histories of all charges detonated in air and argon
atmospheres are shown in Figure 10 and 11 respectively. Method of
determining temperature from spectroscopic data is presented in ref. 16.
Aluminium powder size, charge type affect the measured temperatures. In fact,
the fireball temperatures of pressed charges with big aluminium particle size are
clearly higher than those with smaller aluminium particles by a minimum 200
K. This difference is very small in the case of layered charges where
temperature profiles are similar. If it comes to comparison between the charge
types, pressed composite charges generate higher fireball temperatures than
layered charges and this is true for both aluminium particle sizes. The explosion
process of pressed charges inside the confined explosion chamber provides
better conditions for the combustion of aluminium particles (better mixing,
better contact between the chemical species in the early time).
Fig. 10. Temperature profiles of the charges detonated in the small explosion chamber
in air atmosphere

Temperatures could not be measured for homogeneous charges when
detonated under argon atmosphere, simply because no light was recorded by the
spectrometer for all shots (3 shots for RDXph and 6 shots for TNT).This means
that after detonation; the afterburning reactions of the detonation products were
not able to sustain an explosion fireball in the absence of oxygen. Concerning
aluminized charges detonated in argon, as it was expected, due to the oxygen
lack, the values of the measured fireballs temperatures are smaller than those
measured in air (about 700 K and 200 K lower for pressed and layered charges
respectively).
Fig. 11. Temperature profiles of the charges detonated in the small explosion chamber
in argon atmosphere
3.2. Semi-closed explosion investigations
3.2.1. Overpressure history, peak overpressure, specific and total
impulses
The pressure time histories ∆P(t), light output and spectra recorded after
the detonation of the big charges enabled us to study the blast and explosion
characteristics of the composites. Exemplary blast wave measurements are
shown in Figure 12. These overpressure profiles are used to determine the
maximum overpressure and the specific impulse of each charge. Results are
presented in Figure 13 and 14 respectively. Peak overpressure values were
obtained after approximation of the first incident blast wave using a modified
Friedlander equation [17] and the specific impulses by integrating the
overpressure during the time where this later is positive (only for the first
incident blast wave). By comparison with ideal charges; aluminized charges
generate higher peak pressures than TNT and quiet similar to that of RDXph at
both gauges. Also, the measured peak pressures for pressed composite charges
are higher than for layered ones. Histogram in Figure 14 shows clearly the
superiority of the composite charges concerning the generated specific impulses
at both 2 and 2.5 m. This blast wave enhancement is due to the additional
energy released after the combustion of the aluminium metallic fuel contained

in the composite charges. Similarly to peak pressure results; the specific
impulses determined for pressed aluminized charges are higher than those
determined for layered charges. This means that during a time period
corresponding to the first blast wave registration, the amount of aluminium
combusted is higher in the case of pressed charges detonations than in the case
of layered charges. Unfortunately, the answer to the question which aluminium
particle size provides better blast performance (Peak overpressure and specific
impulse) is not clear, it seems that smaller aluminium particles sizes are better;
however differences are very small, that a net conclusion cannot be taken, same
ascertainment was reported in the reference [18].
Fig. 12. Recorded overpressure histories after the detonation of TBX-12-A charge in
the semi-closed bunker
Overpressurepeak[KPa]
0
10
20
30
40
50
60
70
80
90
100
gauge at 2.5 m
gauge at 2 m
TNT RDXph RDXph core TBX-11-A TBX-12-A TBX-21-A TBX-22-A
Fig. 13. Specific impulse results at
distances of 2 and 2.5 m
Specificimpulse[Pas]
0
5
10
15
20
25
30
35
40
45
50
gauge at 2.5 m
gauge at 2 m
TNT RDXph RDXph core TBX-11-A TBX-12-A TBX-21-A TBX-22-A
Fig. 14. Peak overpressure results at
distances of 2 and 2.5 m
The blast overpressure in semi-closed structures can also be characterized
by the total impulse defined as follow:
(3)
The impulse histories calculated for a period of 60 ms after the shock
wave reached the gauges are presented in Figures 15 and 16. The superiority of

the composite charges in the impulse comparing to high explosives charges
continue during the first 60 ms. The gap increases with increasing time. Still,
the effect of fuel particle size is not clearly observed as well as the charge kind
(pressed or layered) this time. Application of the outer explosive layer increased
the impulses about twice.
Fig. 15. Impulse histories at a distance
of 2 m
Fig. 16. Impulse histories at a distance of
2.5 m
3.2.2. Light output and fireball temperatures
Light output histories recorded by the photodiode are presented in the
Figure 17. Appearance of the signal corresponds to the initiation of the
explosion. For all tested charges a quick initial increase in the light output is
observed, this corresponds to the detonation and the early explosion stage. After
light intensity increases a second time for all charges, however, duration of light
emission is much longer for TNT and composite charges comparing to RDXph
and RDXph core. The late time light output results from the reaction of different
species and detonation products in the explosion fireball, so, it can be
considered as an indicator of the afterburning reactions. These latter are
combustion reactions of aluminium and detonation products after mixing with
air in the case of aluminized charges. In the case of TNT, it is caused by the
afterburning reactions of the under-oxidized TNT detonation products after
mixing with air also, since this latter has a very low oxygen balance.
Temperature measurements presented in Figure 17 shows that unlike
detonations in the small explosion chamber, the composite charges generate
much higher fireball temperatures than the high explosives. The layered charges
showed here the highest values of the measured temperatures; despite that the
pressed ones had higher peak pressure and specific impulses values. This means
that layered charges are better to produce heat than the pressed ones in semi-
closed spaces and they be considered as thermobarics. From comparison of
temperature changes in the confined explosion chamber and the semi-closed
bunker it follows that the generated fireball temperatures are strongly affected
by the confinement volume.

Time [ms]
-20 0 20 40 60 80 100 120 140 160 180
Voltage[V]
-0.2
0.0
0.2
0.4
0.6
0.8
TNT
RDXph
TBX-11-A
TBX-12-A
TBX-21-A
TBX-22-A
RDXph core
Fig. 17. Light output recorded by the
photodiode
Time [ms]
0 5 10 15 20 25 30 35
Temperature[K]
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
TNT
RDXph core
RDXph
TBX-11-A
TBX-21-A
TBX-12-A
TBX-22-A
Fig. 18. Fireball temperature histories in
the semi-closed bunker
4. Conclusions
A water free slurry method for explosive flegmatization and multi-
components rich-fuel macroscopic granules preparation was elaborated with
success. Confined explosion investigations showed that the structure of the
macroscopic granular composite, charge type, aluminium particle sizes and
oxygen availability inside the explosion chamber affect strongly the QSP and
the aluminium afterburning reactions in the confined space. Effect of the charge
type is also highlighted in the semi-closed investigations, results showed that
pressed charges are EBXs and the layered ones can be considered as TBXs.
However, role of the aluminium fuel particle size seems to not be clearly
palpable. All fireballs temperatures results of charges investigated in this work
could be a contribution for the existing literature since a big lack is noticed;
especially for thermobaric explosives were temperature is a major metric.
Comparison between the obtained results for the composites with the classical
explosives as well as with previous works showed that a new metal containing
explosive composite with high blast and explosion characteristics has been
obtained. However, still not the whole energy of metallic fuel is effectively
used.
ACKNOWLEDGMENTS
The authors express there sincere appreciation and gratitude to all contributors
of this work. Special thanks to Drs. Józef PASZULA and Mateusz SZALA.
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DETONATION AND COMBUSTION OF NEW HETEROGENEOUS COMPOSITE EXPLOSIVES CONTAINING ALUMINUM PARTICLES