Experimental analysis of ballistic trauma in a human body protected with 30 layer packages made of biaxial and triaxial Kevlar 29 fabrics

Abstract

Behind armour blunt trauma (BABT) is a body injury resulting from the deformation of the back surface of armour as a result of a bullet impact. In the case of textile body armour, the severity of the injury may depend on the material of the fibres, but also on the geometric structure of the fabric. The article focuses on experimental research into injuries of the human body protected by ballistic packets made of biaxial and triaxial fabrics, during a non-penetrating impact from a Parabellum 9 × 19 Full Metal Jacket (FMJ) bullet, at a speed of 406 ± 5 m/s. In experimental research, the fabrics had a comparable surface weight and were made of the same Kevlar 29 yarn. The ballistic packages were made of 30 layers. As part of the work, a physical model of the human body was developed. The human body model consisted of a model of the heart, lungs, and skeletal and muscular systems. During the bullet impact, the pressure forces were recorded using sensors located at selected points of the human body. The bullets hit five selected places on the body that were considered critical, from the point of view of maintaining a human’s vital functions. It was found that, during firing, pressure increases both at the site of impact and in the internal organs, which can lead to multi-organ damage. As a result of the experimental analysis, it has been shown that the pressures exerted on specific organs are always lower in the case of body protection with a ballistic packet made of triaxial fabrics, compared to a packet made of biaxial fabrics.

Full text

Experimental analysis of ballistic trauma in a human body protected
with 30 layer packages made of biaxial and triaxial Kevlar®29 fabrics
Justyna Pinkos
a
,
*
, Zbigniew Stempien
a
, Anna Sme˛dra
b
a
Institute of Textile Architecture, Lodz University of Technology, Lodz, Poland
b
Chair and Department of Forensic Medicine, Medical University of Lodz, Lodz, Poland
article info
Article history:
Received 29 March 2022
Received in revised form
7 June 2022
Accepted 11 July 2022
Available online xxx
Keywords:
BABT
Kevlar®29
Biaxial fabrics
Triaxial fabrics
Human body model
Parabellum 9x19 mm bullet
abstract
Behind armour blunt trauma (BABT) is a body injury resulting from the deformation of the back surface
of armour as a result of a bullet impact. In the case of textile body armour, the severity of the injury may
depend on the material of the fibres, but also on the geometric structure of the fabric. The article focuses
on experimental research into injuries of the human body protected by ballistic packets made of biaxial
and triaxial fabrics, during a non-penetrating impact from a Parabellum 9 mm 19 mm Full Metal Jacket
(FMJ) bullet, at a speed of 406 ±5 m/s. In experimental research, the fabrics had a comparable surface
weight and were made of the same Kevlar®29 yarn. The ballistic packages were made of 30 layers. As
part of the work, a physical model of the human body was developed. The human body model consisted
of a model of the heart, lungs, and skeletal and muscular systems. During the bullet impact, the pressure
forces were recorded using sensors located at selected points of the human body. The bullets hit five
selected places on the body that were considered critical, from the point of view of maintaining a
human’s vital functions. It was found that, during firing, pressure increases both at the site of impact and
in the internal organs, which can lead to multi-organ damage. As a result of the experimental analysis, it
has been shown that the pressures exerted on specific organs are always lower in the case of body
protection with a ballistic packet made of triaxial fabrics, compared to a packet made of biaxial fabrics.
©2022 China Ordnance Society. Publishing services by Elsevier B.V. on behalf of KeAi Communications
Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/
licenses/by-nc-nd/4.0/).
1. Introduction
Textile ballistic shields are designed to protect the wearer when
struck by a low-energy bullet, usually fired from a handgun. It
should be noted that, despite the retention of the bullet in the
structure of the ballistic packages, potential ‘behind armour blunt
trauma’(BABT) injuries may occur due to excessive deformation
and the possibility of the significant transmission of impact energy
to the human body. BABT injuries involve the risk of external and
internal injuries to the human body, causing disturbances in the
functioning of the body, which, depending on the scale, may cause
death or severe disability [1e3]. Studies in the field of bullet
wounds [4e8] and animal injuries [9e12] show that the velocity of
the bullet, the type of ballistic shield and the weight of the
bulletproof vest wearer all have an impact on the scale of the
ballistic impact. Numerical research mainly considers the evalua-
tion of the physiological effects of a ballistic strike as a bullet hits
the numerical model of a human body protected by a ballistic
packet [13e16]. On the other hand, the development of numerical
models of lungs, livers or cardiovascular systems, allow for a better
understanding of the phenomenon of ballistic trauma in a specific
organ [18e20]. Published studies on the BABT phenomenon show
that a very important factor leading to bodily injuries is a sharp
increase in pressure at the point of bullet impact (i.e. the stress
wave and energy transmission to the human body [21]). It is
claimed that, as a result of a rib rupture, the parenchyma of the
lungs may tear and numerous bruises may appear [1]. Cases of
blunt ballistic injuries, as a result of a non-penetrating shot,
allowed the definition of the phenomenon of ballistic trauma as a
clinical unit, the scale of which depends on the anatomical hit of the
bullet [2]. Taking into account the location of the bullet’s impact in
the area protected by the armour, the greatest risk of death occurs
when the strike affects the heart, lungs and liver; while the fat
tissue, muscles and skin strongly suppress the shock wave [13,14].
Due to these threats, there has been continuous research into
*Corresponding author.
E-mail address: justyna.pinkos@p.lodz.pl (J. Pinkos).
Peer review under responsibility of China Ordnance Society
Contents lists available at ScienceDirect
Defence Technology
journal homepage: www.keaipublishing.com/en/journals/defence-technology
https://doi.org/10.1016/j.dt.2022.07.004
2214-9147/©2022 China Ordnance Society. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-
ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Defence Technology xxx (xxxx) xxx
Please cite this article as: J. Pinkos, Z. Stempien and A. Sme˛dra, Experimental analysis of ballistic trauma in a human body protected with 30
layer packages made of biaxial and triaxial Kevlar®29 fabrics, Defence Technology, https://doi.org/10.1016/j.dt.2022.07.004

obtaining textile ballistic packages that minimise lateral deforma-
tion during a non-penetrating impact, as well as the scale of BABT
injuries [13e17].
Current developments in the field of material engineering (in
terms of ballistic fabrics) consist of improving their strength
properties. It should be noted, however, that the ballistic effec-
tiveness of textile covers is also influenced by the geometric
structure of individual layers [22e25]. A bullet impact into the
textile-based ballistic material is associated with many complex
penetration mechanisms, which depend on the properties of the
fibre and ballistic materials, including the properties of fabrics, such
as weave, fabric density or the type of fabric. On the other hand,
they depend on the ballistic impact methodology, ballistic target
arrangement and bullet parameters. From the point of view of the
correct assessment of the dynamic deformation and failure mech-
anisms of ballistic materials, it is important to take into account all
the parameters affecting ballistic resistance. Currently, in order to
better understand the ballistic impact mechanism, apart from
experimental research, research using the finite element method is
very often used [26].
Multi-axial fabrics are promising textile structures for soft bal-
listic packages. Multi-axis textile structures result from the inter-
weaving of at least three thread systems. This type of multi-axis
structure is referred to as a fabric with a triaxial base weave. The
triaxial fabric is characterised by two warp thread arrangements
and one weft thread arrangement. Both warp thread systems are
directed at an angle of ±60

, with respect to the weft thread sys-
tem. As a result of the bullet hitting the triaxial fabric with the base
weave, the shock wave propagates radially along all the systems,
making the area of the fabric absorbing the kinetic energy of the
bullet much larger than the biaxial fabrics of the plain weave. This
results in significantly lower transverse deformation of the pack-
ages made of triaxial fabrics, compared to the packages made of
biaxial fabrics, while maintaining the same yarns constituting the
structure of both fabrics and the surface weight of the bundle
[22,23]. Therefore, when using triaxial fabrics in the layers of the
ballistic packages, significantly less injury to the human body is
expected from a non-penetrating bullet impact.
Understanding the scale of injuries and the size of blunt BABT
injuries resulting from a non-penetrating bullet hitting a human
body protected by armour, is a difficult and complicated issue. From
an ethical point of view, such research cannot be carried out with
human subjects. Significant research into ballistic impacts on bio-
logical organisms, which occurs when they are hit by a non-
penetrating high-energy bullet, was carried out in Sweden [9,10].
The aim of the research was to understand the effects and patho-
physiological mechanisms of a non-penetrating NATO
7.62 mm 51 mm missile hitting a pig's body, at a speed of 800 m/s
and protected by soft and hard ballistic packages. Non-penetrating
impact tests confirmed the presence of apnoea for several minutes,
leading to a severe drop in blood oxygen saturation, immediate
hypotension, a decrease in cardiac output, an increase in mean
pulmonary artery pressure, and a decrease in electroencephalo-
gram (EEG) activity. Sometime after the injury, cardiovascular
function returned to baseline levels but then slowly deteriorated,
possibly due to oxygen deficiency. Soon after a lung injury, cell
damage caused short-term hyperkalemia (increase in blood po-
tassium) which, in some cases, resulted in fatal cardiac arrhyth-
mias. Animals suffering from acute organ hypoxia for an extended
period of time, died. The conducted research documented changes
in the EEG graph after a ballistic impact. Research has documented
changes in the EEG pattern following a ballistic impact.
During each non-penetrating bullet impact, the process of
damaging the organs and tissues of the body took place, the scale of
which depended on the place of impact, its parameters and the
effectiveness of the ballistic shield. The resulting injuries and dis-
eases, to which people are exposed to as a result of shelling, are
numerous and varied [27e29]. The classification of gunshot wound
injuries, taking into account the wounded person's condition and
the types of injuries suffered, was based on [30,31]. In practice,
mechanical injuries are usually divided into ‘penetrating open’or
‘penetrating’(in which the continuity of the body shell is
damaged) and ‘non-penetrating’or ‘closed’injuries (in which the
continuity of the body shell is not broken). However, the lack of a
systemised criterion of the phenomenon of ballistic trauma for the
thoracic and abdominal cavities contributed to the implementation
of extensive scientific research, showing the scale of the problem.
Due to the fact that experimental BABT research cannot be carried
out with human participation or with the use of a human corpse,
physical models of the human body are used for this purpose,
which usually take into account the most important internal organs
for vital functions, i.e. the heart, lungs, liver, skeletal and muscular
systems [32,33]. The models are usually equipped with sensors,
which record the pressure and allow the scale of the internal
damage to be known during the non-penetrating impact of the
bullet. 3D models of internal organs are made of thermoplastic
plastics, the chemical composition of which varies depending on
the organ. In physical models of the human body, the mapping of
the muscular system is possible because of the use of silicone gel,
which has strength parameters similar to the muscle tissues of the
human body. The research conducted into the impact of a 9 mm
bullet, moving at a speed of 430 m/s and hitting the chest (in line
with the heart) covered in armour with a bullet resistance class III-
A, showed that the highest pressure (0.85 MPa) occurred on the
surface of the heart. In other organs, the pressure values were
lower, e.g. for the left lobe of the liver it was 0.12 MPa. In the event
of a bullet hitting the central area of the liver, apressure of 1.64 MPa
in the left lobe of the liver was recorded. Pressures of 0.74 MPa and
0.62 MPa were recorded in the right lobe of the liver and in the
stomach. In turn, the sensor located in the heart recorded a value of
0.2 MPa.
In order to compare the effects of BABT during a non-
penetrating 9 mm Parabellum bullet hitting ballistic packages
composed of biaxial and triaxial fabrics, experimental research was
carried out using a physical model of the human body. The fabrics
were made of the same Kevlar®29 yarn. Such comparative
research has not yet been carried out and published.
As part of this work, a physical model of the human body was
developed. The model of the human body consisted of a model of
the heart, lungs, and the skeletal and muscular systems. During the
bullet impact, the pressure forces were recorded by sensors placed
at selected points of the human body, which were then converted
into pressures. During the firing, the bullet hit five selected places
on the body, which were considered critical from the point of view
of maintaining human vital functions. It was found that pressure
increases both at the site of the impact and in the internal organs,
which can lead to multi-organ damage. As a result of the experi-
mental analysis, it has been shown that the pressures exerted on
specific organs are always lower when the body is protected with
ballistic packages made of triaxial fabrics. Based on the results
obtained by experimental research, a medical analysis of possible
injuries during a non-penetrating bullet hitting the human body,
protected by a ballistic packet made of biaxial and triaxial fabrics,
was carried out.
2. Ballistic fabrics
Two ballistic fabrics were used in this research: biaxial
(Changzhou Utek Composite, China) and triaxial (Triaxial Struc-
tures, USA), both comprising identical Kevlar®29 yarn. The
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
2

detailed structural parameters of these fabrics are presented in
Table 1.
3. Physical model of the human body
As part of this work, a physical model of the human body was
developed, consisting of a model of the heart, lungs, and the skel-
etal and muscular systems. The lung and heart models were made
of Gumosil S silicone (Silikony, Poland), which was obtained by
combining polycondensation rubber, N catalyst and methyl silicone
oil. In order to select the strength parameters of silicone similar to
those of the biological heart and lungs, in the first stage of the
uniaxial static compression study of samples prepared from the
lung and heart organs from pigs, the characteristics of the stress as
a function of material deformation were determined. In order to
carry out these studies no pigs were killed specifically to provide
organs but they were taken from a commercial slaughterhouse in
which the slaugher is carried out for nutritional purposes in
accordance with the standards in force in the European Union.
Experimental static compression tests were carried out on pre-
pared samples using a Hounsfield H10KeS testing machine
(Hounsfield, USA), equipped with a force sensor and a displacement
sensor. Ten cylindrical-shaped samples, with a diameter of 20 mm
and a height of 10 mm, were taken from the collected animal or-
gans (lungs and hearts). Each of the samples was placed between
the movable and stationary plates and, during compression, the
force was recorded as a function of the displacement of the movable
plate moving at a constant speed of 2 mm/s. Fig. 1 shows the
samples of the lung and heart organs placed on the testing machine
before the compression process.
The characteristics of the stress-strain curves (Fig. 2) of the
tested samples of the heart and lungs show the features of a non-
linear material. These types of curves are divided into several re-
gions, the characteristics of which may be related to the structure
and specific physiological function of the tissue [34,35]. There are
three phases of the stress relationship with the soft tissue strain. An
initial zone (with low pre-tension) is followed by a zone of prac-
tically flat compaction and then an exponential compaction zone.
In the initial region, the soft tissue has stiffness, due to its strength.
When the stiffness limit is exceeded, the forces associated with the
compression of the elastin and collagen fibres in the heart and
alveoli in the lungs, begin to act when the tissue is compressed
further [34,36].
In order to select the materials forming the physical models of
the heart and lungs, a series of uniaxial compression tests of sam-
ples made of a hardened mixture of polycondensation rubber, N
catalyst and methyl silicone oil for various weight proportions were
carried out. The obtained stress-elongation characteristics were
compared with the approximate stress-elongation functions ob-
tained from the compression of the biological samples. For each of
the variants, cylinder-shaped samples, with a diameter of 20 mm
and a height of 10 mm, were made. The weight proportions of
polycondensation rubber, N catalyst and methyl silicone oil com-
ponents in the mixture (in the case of lungs for the individual
variants P_1 ÷P_6) were 8.3/1/16.6 (P_1), 8.3/1/20.75 (P_2), 8.3/1/
24.9 (P_3), 8.3/1/12.45 (P_4), 8.3/2.5/14.53 (P_5) and 8.3/3.35/14.53
(P_6), respectively. Fig. 3 shows examples of the photographs of the
sample made in the P_1 variant, from the uniaxial compression
tests.
On the basis of the results obtained from the compression
testing of silicone samples, the stress-elongation characteristics
were determined. Fig. 4 presents a summary of the obtained
characteristics for the adopted variants, which were then compared
with the approximating curves from the experimental testing of
biological samples of the lungs and the heart taken from a pig. It
was noted that, by modelling the weight ratio between the com-
ponents of the silicone mixture, one can obtain stress-elongation
characteristics similar to those obtained for biological samples.
On this basis, a variant of the mixture of silicone P_5 and S_6 was
adopted for making physical models of the lungs and the heart.
Table 1
Detailed parameters of Kevlar®biaxial and triaxial fabric 29.
Parameters Biaxial fabric Triaxial fabric
Weave type Plain weave Basic triaxial
The linear mass of the yarn/dtex 1500 1500
The number of threads in the fabric/(threads$cm
1
) Weft Warp Weft Warp 60

Warp 60

77 44 4
Surface mass/(g$m
2
) 200 ±10 198 ±10
The thickness of the fabric/mm 0.28 ±0.03 0.26 ±0.03
Fig. 1. Samples of organs from pigs before the compression process: (a) Lung; (b) Heart.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
3

In order to make silicone models of the lungs and the heart,
gypsum forms were made first, which were obtained by placing
anatomical plastic models of the lungs and heart (with dimensions
typical for a male) in a rectangular container, then filling the whole
with gypsum. After hardening of the gypsum, the moulds obtained
were cut into two parts and the remnants of the anatomical models
of the heart and lungs were removed. Fig. 5 shows the gypsum
moulds created.
The silicone models of the lungs and the heart were made by
filling gypsum moulds with a mixture of polycondensation rubber,
N catalyst and methyl silicone oil, in the variant P_5 for the lungs
and S_6 for the heart. Pressure force sensors CP18-151AS (IEE S.A.,
Luxembourg), with a diameter of 12 mm and a measuring range
from 0.2 N to 100.0 N, were used to measure the pressure exerted
on the lungs and heart as a result of a ballistic strike after a bullet
impact. Pressure force sensors were placed in the front part of the
Fig. 2. Compression characteristics and approximation curves for: (a) Lungs; (b) Heart.
Fig. 3. Compression strength test of a silicone sample in variant P_1: (a) Before the compression process; (b) During the compression process.
Fig. 4. The results of the compressive strength tests of silicone samples compared with the approximating function obtained from the testing of biological samples for: (a) Lungs; (b)
Heart.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
4

right and left lungs before filling the lung moulds with silicone.
After both parts of the lung mould were filled with the silicone
mixture, they were joined and allowed to cure for 24 h. Fig. 6 shows
the right and left lung models obtained, with sensors. A similar
methodology was used for the production of a silicone heart model,
in which pressure sensors were placed on the outer surface and in
the centre of the heart. Fig. 7(a) shows a pressure sensor placed
inside the heart after filling one part of the plaster with a silicone
mixture. Fig. 7(b) shows a front view of the silicone heart model
with the pressure sensor placed on the outer surface of the heart.
In the next stage of development of the physical model of the
human body, a gypsum form of the human body was made, which
had the actual dimensions of a man's chest. For this purpose, a
clothing mannequin with the characteristic proportions of typical
men aged 25e30 was used. In order to make a plaster mould, a
clothing mannequin was placed in a wooden box with the di-
mensions taking into account the mould allowance, in relation to
the external dimensions of the mannequin. In the next step, the
whole structure was filled with gypsum and allowed to harden for
about 14 days. The cured gypsum mould was then cut into two
parts. Fig. 8 shows a view of a clothing mannequin adopted as a
model of the human body (Fig. 8(a)), a box filled with gypsum, left
to harden (Fig. 8(b)), and the gypsum forms obtained after cutting
the hardened casting (Fig. 8(c)).
In the next stage, a model of the skeletal system, consisting of
the sternum, ribs and spine, was developed. The bridge model was
made using a Bungard CCD numerical milling machine (Bungard,
Germany) after making a numerical model of the bridge using the
software. The shape and dimensions of the sternum were deter-
mined on the basis of computed tomography scans of the chest of a
30-year-old man. The bridge model was made of a 10 mm thick
porous PVC plate. The front and back of the obtained model of the
bridge, with the pressure force sensor attached, is shown in Fig. 9(a)
to Fig. 9(c).
The next task in the implementation of the skeletal system was
the preparation of rib models. Ribs material was selected based on
the reports of human rib strength testing. Stein and Granik [37]
reported that the relationships between human age a
h
and flexural
strength
s
flex
as well as breaking load Pfor human ribs during
three-point bending of them can be determined by the experi-
mental Eq. (1) and Eq. (2)
s
flex
¼131 1:03$a
h
(1)
P¼254 3:34$a
h
(2)
where the
s
flex
and Pare given in MPa and N, respectively. Ac-
cording to these equations, the value of flexural strength and
breaking load for the 30-year-old man ribs can be calculated as
100.1 MPa and 153.8 N, respectively. Yoganandan and Pintar [38]
experimentally determined the flexural modulus of human ribs at a
level of 2.08 ±0.45 GPa, while three-point bending the 120 post-
mortem ribs taken from individuals aged between 29 and 81. The
breaking load of ribs from 137 to 162 N was noted, depending on
the rib number. Pezowicz and Głowacki [39] under similar test
conditions determined the flexural modulus of human ribs in
young adults at a level of 4.71 ±1.67 GPa. While analysing the re-
ported strength parameters of human ribs a similar performance of
the poly(methyl methacrylate) PMMA was found out. Al-Dwairi
et al. [40] reported the flexural modulus and strength of conven-
tional heat-cured PMMA equal to 2.1172 GPa and 93.33 MPa,
respectively. Kurguzov and Demeshkin [41] reported the flexural
strength of PMMA at a level of 102.827 MPa during three-point
bending. Di Carlo et al. [42] reported the flexural modulus and
strength of conventional PMMA of 2.88 GPa and 96.32 MPa,
respectively. It can be compared that the values of flexural modulus
and strength for human ribs are similar to the reported values for
conventional PMMA. On the base of this comparison, the conven-
tional PMMA was selected as ribs material in developed human
model. To fabricate the physical model of ribs a 4 mm thick PMMA
plexiglass plate was purchased from Akces Co. (Poland). In order to
determine the strength parameters of this plexiglass plate, 6 bars of
size of 4 20 160 mm
3
were cut and subjected to a three-point
Fig. 5. Gypsum moulds of: (a)The right and left lobe of the lung; (b) The heart.
Fig. 6. The silicone models of the right and left lung with sensors placed on the
surface.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
5

bending test on an Instron 3366 testing machine with a span length
of 100 mm. It was determined that the flexural modulus and
strength for this PMMA plexiglass were 2.7 ±0.23 GPa and
98.0 ±8.2 MPa, respectively. Assuming the value of breaking load P
calculated from Eq. (2) for the 30-year-old man ribs equal to
153.8 N, finally the width bof PMMA plexiglass bars, which
modelled the ribs in a physical model of the human body was
calculated from Eq. (3)
b¼3$P$L
2$
s
PMMA
$a
2
(3)
where Lis the span length,
s
PMMA
is the flexural strength of PMMA
plexiglass and ais the thickness of PMMA plexiglass plate. For the
span length, flexural strength and thickness of PMMA plexiglass of
100 mm, 98.0 MPa and 4 mm, respectively, the width of bars of
14.7 mm was calculated. In order to reproduce the shape of the rib,
Fig. 7. The pressure force sensor in the heart model: (a) Placed inside; (b) Placed on the outside.
Fig. 8. Photos from the stages of developing a physical model of the human body: (a) Stage one - a view of the adopted clothing mannequin; (b) Stage two - a gypsum block with a
clothing mannequin; (c) Stage three - gypsum forms of the front and back of the body after cutting.
Fig. 9. View of the skeleton model with the sternum, ribs and spine: (a) From the front; (b) From the back; (c) back of the sternum with the pressure sensor visible.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
6

each flat bar was plasticised by annealing at a temperature of
90e100

C for approximately 10 min and then formed to the
assumed rib curvature. The rib pairs were attached to a sternum
and spine, constructed from an aluminium profile with a cross-
section of 4 4cm
2
and screws (Fig. 9(a) and Fig. 9(b)).
The developed models of the lungs, heart and skeletal system, as
well as the pressure force sensors located in accordance with
Table 2, were placed in plaster moulds of the human body model. In
the next step, 20% Synthetic Ballistic Gelatin (Clear Ballistics, USA)
was melted at a temperature of 126

C and filled into gypsum
moulds of the human body. The whole was left to fully harden the
ballistic gel for 48 h and then the finished model was removed from
the gypsum mould. For the ballistic tests, two identical human body
models were made (one for the biaxial fabric packet and the other
for the triaxial fabric packet). Fig. 10 shows the front and back views
of the model of the human body.
The physical model of the human body in the ballistic studies
did not include the liver model or the small and large intestine
model. The pressure force sensors were embedded in ballistic gel in
the anatomical location of the centre of the liver, at a depth of
22e24 mm and, in the case of the small and large intestines, at a
depth of 18e19 mm.
Experimental research was carried out in a ballistics laboratory.
The diagram of the ballistic stand is shown in Fig. 11. The stand was
equipped with a ballistic test barrel to launch bullets, a system of
gates for measuring the velocity of impact, a frame generating a
signal for triggering the signal registration system from the sensors
and a human body model with ballistic packages. In the experi-
mental research, Winchester 9 19 mm FMJ Parabellum bullet was
used, with a lead core and a shell made of ballistic brass. The weight
of the bullet was 8 g. The signal recording system comprised Tex-
tronics digital multi-channel oscilloscopes.
Each pressure force sensor was connected to the measuring
system and contained a voltage divider and a voltage follower
(Fig. 12). The measured output voltage was equal to
U
out
¼U
ref
$
R
s
R
s
þR(4)
Prior to the placement of the sensors in the human body model,
they were calibrated by placing each sensor between the 12 mm
diameter pneumatic actuator stem and the force measuring head.
During the calibration, the air pressure values were adjusted so that
the pressure force was at a set level, and then the output voltage
U
out
was measured.
The experiments were carried out for each of the pressure force
sensors used in the human body model. The calibration process was
carried out three times for each of the sensors and, based on the
recorded values, the equation of the calibration curve was
determined
F¼F
0
þA
1
exp
ððU
out
U
out0
Þ=t
1
Þ
þA
2
exp
ððU
out
U
out0
Þ=t
2
Þ
(5)
where
Fegiven force,
U
out
emeasured voltage in the measuring system,
F
0
,A
1
,A
2
,U
out0
,t
1
,t
2
eparameters of the approximating
function.
An exemplary graph of the dependence of the pressure force as a
function of voltage is shown in Fig. 13.
The calibration of the sensors allowed further experimental
research to calculate the pressure force, based on the recorded
voltage values. Knowing the values of the pressure force and the
sensor surface, the pressure exerted at the sensor location was
calculated from the quotient of these values.
4. Ballistic packages for experimental research
Before starting the experimental research in the ballistic tunnel,
packages consisting of 30 layers were prepared from the tested
ballistic fabrics. For this purpose, a design for the front of the ar-
mour was constructed based on the dimensions of the human body
model. The layers were then cut from the ballistic fabrics and joined
with a double lock-stitch, using 100% Twaron NM 50/2 aramid
threads. Several point stitches, at a distance of approximately 1 cm
from the edge of the packages, were carried out with a stitching
length of about 5 cm. Fig. 14 shows a view of two identical models
Table 2
Location of pressure sensors in the human body model.
Location of the pressure sensors
Chest cavity Heart Inside (H1)
On the surface (H2)
Right Lung On the surface (Lu1)
Left Lung On the surface (Lu2)
Sternum On the internal surface of the sternum between the second and third ribs (S1)
Rib On the second rib on the left - exterior surface, (R1)
On the third rib on the left side internal surface (R2)
On the third rib on the right - internal surface (R3)
Abdominal cavity Liver In the gel on the right under the ribs (Li1)
Small and large intestine In the gel in the umbilical area (I1)
Fig. 10. Front and back view of the human body model with the heart, lungs, skeletal
and muscular systems and pressure sensors.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
7

of the human body, with applied ballistic packages made from
biaxial and triaxial fabrics, before firing.
At a later stage, the sensors recording the pressure forces were
connected to multichannel digital oscilloscopes and each of the
ballistic packages received five hits from Winchester 9 mm 19
mm FMJ Parabellum bullets, in accordance with the selected firing
points (Fig. 15). These were considered critical, from the point of
view of maintaining a functioning person's life. Firing point 1 cor-
responds to the bullet where the sternum is located, behind which
is the heart and large blood vessels. Firing point 2 is the site of one
of the ribs, behind which is the pleural cavity with a lung. Firing
point 3 was located in the projection of one of the intercostal
spaces, under which there is also the pleural cavity with a lung.
Firing point 4 is projected onto the medial epigastric region,
beneath which the liver is located, and firing point 5 corresponds to
the medial epigastric projection of the intestines. The listed organs
are important from the point of view of maintaining vital functions
and their damage, directly or indirectly, may be life-threatening.
Fig. 11. Diagram of the ballistic stand.
Fig. 12. Diagram of the connection of a pressure force sensor with the measuring
system.
Fig. 13. Graph of the dependence of the pressure force on the function of the voltage
U
out
.
Fig. 14. View of human body models before the firing with applied ballistic packages
made of fabrics: (a) Biaxial, (b) Triaxial.
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8

5. Results of experimental research depending on the
location of the bullet impact
5.1. Bullet hitting the sternum on the heart position line
In the case of the bullet hitting the sternum in line with the
heart position, fractures in the sternum model (Fig. 16) were noted
for both ballistic packages, made of biaxial and triaxial fabrics.
During examination of the external injuries of the physical
model of the human body, localised microdamage of the ballistic
gel was observed. The sternum model suffered the greatest internal
injuries, as it suffered numerous cracks in the ballistic packages
made of biaxial and triaxial fabrics. It should be noted that the
number of cracks and the area of damage were greater in the
sternum model protected by packets made of biaxial fabrics. The
medical analysis of the situation showed that the breakdown of the
anatomical continuity of the sternum may damage the internal
structure of the chest (e.g. lungs, heart) covered by the sternum. It
should be noted that bone fractures may be multi-fragmentary and
the damaged bone fragments may constitute the so-called ‘sec-
ondary bullet’, which can expand the area of damage.
In the next stage, the results of the pressure values on the in-
ternal surface of the sternum, after the bullet hit the line of the
heart position, were analysed (Fig. 17). The tendency of the occur-
rence of higher pressure values in the sternum when protecting the
human body model with ballistic packages made of biaxial fabrics,
rather than triaxial fabrics, was noted. The maximum pressure for
protection with a ballistic package made of biaxial fabrics was
12 MPa while, for protection with a package of triaxial fabrics, it was
7 MPa. It can be concluded that, as a result of the bullet hitting the
packages made of biaxial fabrics, the pressure is more localised and
covers a smaller body surface, which results in greater pressure at
the point of impact. On the other hand, for the second variant, the
acting pressure force of the packages made of triaxial fabric is
distributed over a larger surface, resulting in a lower value of
maximum pressure at the point of impact [29,32]. On the basis of
the pressure course, it can be concluded that the characteristic
decrease and then increase of the pressure value is a result of the
rupture of the sternum model. Injury to the anterior chest wall from
a non-penetrating impact can further injure internal organs. The
recorded pressure values in the internal organs, in the case of body
protection with packages made of both biaxial and triaxial fabrics,
are shown in Fig. 18.
The protection pressure with packages made of biaxial fabrics
reaches a higher value for the H1 and H2 sensors: 0.05 MPa and
0.7 MPa, respectively. While, for packages made of triaxial fabrics,
the pressure values were lower, i.e. 0.04 MPa and 0.32 MPa. In the
published studies, using the same type of bullet [32,33], the highest
pressure value recorded on the heart’s surface was 0.85 MPa. On
the basis of medical descriptions [27], pressure values in the range
of 0.5 MPae1.0 MPa in the heart muscle, cause injuries such as:
haemorrhages of the anterior and posterior walls of the heart and,
in extreme cases, rupture of the pericardial sac. The impact on the
Fig. 15. Selected places of bullet impact on the physical model of the human body,
where: 1 - sternum in line with the heart position, 2 - rib II, 3 - intercostal space in line
with the lungs, 4 - liver, 5 - small and large intestine.
Fig. 16. Damage to the sternum model after experimental research with the use of a
packet made of fabrics: (a) Biaxial; (b) Triaxial.
Fig. 17. The pressure course for the S1 sensor during the bullet impact on the centre
line of the sternum, with body protection by ballistic packages made of biaxial and
triaxial fabrics.
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9

lower pressure amplitudes for the H1 and H2 sensors, when pro-
tected with packages made of triaxial fabrics, may result from the
transmission of the stress wave through the three main thread
systems in contact with the face of the bullet. When a bullet hits a
package made of triaxial fabrics, the shock wave propagates radially
along all the systems, causing the area of the fabric absorbing the
kinetic energy of the bullet to be larger than for a package made of
biaxial fabrics. The increase in the area covered by the deformation
depends on the speed of propagation of the stress wave in the plane
of the triaxial fabric. BABT injury in the human body during a firing
on the sternum in line with the heart position, may lead to bruising
of the integuments (abrasion of the epidermis, bruising and
swelling), bruising of the subcutaneous tissue and muscles
(ecchymosis and swelling) or haematomas within them (fluid res-
ervoirs filled with blood). It should be noted that the fractures in
the sternum are not dangerous in themselves but their complica-
tions, such as the possibility of pneumothorax or haematoma of the
pleural cavity, are much more dangerous. In such cases, one would
expect bruising of the lungs. It can also bruise the heart, which can
result in heart rhythm disturbances and, possibly, fatal
consequences.
The pressure values for Lu1 and Lu2 sensors were also lower
when protected with packages made of triaxial fabric. The
maximum pressure value of the Lu1 sensor was 0.06 MPa and, for
the Lu2 sensor, it was 0.13 MPa, while for the packages made of
biaxial fabrics it was 0.1 MPa and 0.18 MPa, respectively. The
recorded pressure courses of the Lu1 and Lu2 sensors cover a
similar time period. Higher pressure values for the Lu1 and Lu2
sensors, when protected with packages of biaxial fabrics, depend on
the structure. Rapidly changing local displacement of the threads
towards the bullet's flight path causes the formation of a stress
wave, which propagates along the threads of the weft and warp,
symmetrically in all four directions. Higher pressure values for the
ballistic packets made of biaxial fabrics result from the nature of the
local deformation of the shield and the impact of pressure on the
human body model in a point-like manner.
The other three sensors (R1, R2 and R3) also registered lower
pressure values while protecting the packages made of triaxial
fabrics. The courses of the pressure curve for sensor R1, in both of
the tested ballistic packages, shows significant increases and dy-
namic decreases in the pressure value. It is claimed that the impact
of the bullet causes a dynamic deformation of the packet, which
translates into the BABT strike, leading to the phenomenon of
deflection and relaxation of the chest. As a result, the recorded
pressure curves of sensor R1 record high, instantaneous pressure
peaks and then a rapid drop. For the pressure curves of sensors R2
and R3, the amplitudes are smaller than for the pressure curves of
sensor R1. This may be due to the location of these sensors, which
were located below the line of fire and on the inside of the ribs.
5.2. Bullet impact on rib II
In the next stage, the blunt BABT trauma was analysed in the
human body model during a non-penetrating bullet impact in the
line of the second rib on the left hand side. It should be noted that
after the first shot at the sternum on the line of the heart position,
both the sternum model and the S1 sensor were destroyed.
Therefore, it can be assumed that reducing the stability of the
connection of the rib models with the sternum model could in-
crease the injuries in the area of the II rib and thus the obtained
pressure values recorded by sensors located in the place of the
bullet impact. In the first stage, the human body model was
examined at the point of bullet impact. For the packages made of
biaxial fabrics, it was found that the rib model cracked at the site of
the bullet impact, which was not found after hitting the packages
made of triaxial fabrics. Fig. 19 shows a photograph of the location
of the broken rib model. A fracture in the first three ribs can lead to
a BABT injury and contribute to an injury to the respiratory tract. In
contrast, fragments of a broken rib can stick into the structure of
the lung parenchyma, leading to internal haemorrhaging. Research
has shown that this type of injury can be reduced by using soft
ballistic packages made of triaxial fabrics.
BABT injuries in bone are different from injuries in the areas of
Fig. 18. Pressure course for sensors H1, H2, Lu1, Lu2, R2, R3 and R4 during the bullet hitting the sternum with body protection with ballistic packages made of fabrics: (a) Biaxial; (b)
Triaxial.
Fig. 19. The site of a broken second rib with the use of a ballistic package made of
biaxial fabrics.
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muscle tissue. This is mainly due to the greater stiffness and lower
flexibility of the bones. The characteristics presented in Fig. 20
confirm that, when using the ballistic packet made of biaxial fab-
rics, the recorded pressure from the R1 sensor reaches higher
values than for the packet made of triaxial fabrics. The maximum
value of the sensor pressure R1 for packages made of biaxial fabric
was 11 MPa while, for protection with packages made of triaxial
fabric, it was equal to 3 MPa. It should be noted that the timing of
the BABT impact by the registered pressure of the R1 sensor, was
shorter for the packages made of biaxial fabrics and amounted to
approximately 0.3 ms; for the packages made of triaxial fabrics, the
pressure was gradually released in the time close to 1 ms. This
tendency may depend on the geometric structure of the fabrics
tested. During the impact of the bullet against the packages made of
biaxial fabrics, the area of propagation of the stress wave is smaller,
resulting from the two main systems of threads. The pressure de-
pends on the surface and the force acting on it. In the case of
packages made of triaxial fabrics, which have three main systems of
threads in its structure, the surface of the propagating stress wave
is increased and, consequently the decay time is extended.
Fig. 21 shows the pressure courses recorded by the other sensors
(H1, H2, Lu1, Lu2, R2, and R3), which were located in the chest of the
human body model. The graphs do not show the waveforms from
the sensor located in the bridge (S1) because it was damaged
during the first attempt, when the bullet hit the bridge. Addition-
ally sensor Li1 and the sensorI1 did not register any values during
this bullet shot. Therefore, it can be assumed that the human body
model did not experience BABT injuries in the area of the intestine
and liver. For the H1 and H2 sensors placed in the heart model, the
pressure values are also lower when protected with ballistic
packages made of triaxial fabrics. The pressure of the H1 sensor is
close to zero and the pressure of the H2 sensor is less than 0.1 MPa.
In the case of the ballistic packages made of biaxial fabrics, the
pressure was about 0.1 MPa and 0.45 MPa, respectively. It should be
noted that, despite the differences in the pressure values of the H1
and H2 sensors, the shape of the pressure curve is similar. It is also
worth noting that, for the H2 sensor, when protected with packages
made of triaxial fabrics, there is a pressure time delay of 0.1 ms,
compared to packages made of biaxial fabrics. This is probably due
to the geometric structure of the triaxial fabric, which provides a
transmission delay and a reduction in the maximum pressure
amplitude on the human body model.
The graphs in Fig. 21 also show the pressure courses of the Lu1
and Lu2 sensors. In the case of the right lung (Lu1), the pressure
value was close to zero for both tested soft ballistic packages. On the
other hand, for Lu2, when protected with a bundle of biaxial fabrics,
the pressure value was about 3.8 MPa and, when protected with a
bundle of triaxial fabrics, it was 1.65 MPa. Again, this result con-
firms the advantage of triaxial fabrics over biaxial fabrics. The
additional system of threads allows an increase in the speed of
wave propagation, which should be as high as possible, from the
point of view of the ballistic effectiveness of fabrics.
For the R3 sensor, the pressure value for both of the tested soft
packets was close to zero. The pressure was registered by the R2
sensor located on the left hand side of the chest, in the area where
the second shot was fired. The pressure value of the R2 sensor,
when protected with packages made of biaxial fabrics, was about
2.3 MPa and, for packages made of triaxial fabrics, it was about
1 MPa. The tendency to achieve twice the pressure values when
protected with packages made of biaxial fabrics, compared to
packages made of triaxial fabrics, was confirmed once more. It
should be noted that the time of action of the blunt BABT trauma
exerted by the third left-hand rib (R2) is longer when protected by
packages made of triaxial fabrics. On the other hand, with packages
made of biaxial fabrics, the pressure in the R2 sensor is temporary
but its amplitude is twice as high as that for packages made of
triaxial fabrics. In both cases of protection with human body bun-
dles, BABT can lead to banded effusions along the ribs and cause rib
fractures but there are also potential complications, such as pneu-
mothorax or pleural haematoma, as well as lung rupture.
Fig. 20. Pressure course for the R1 sensor during the impact of a bullet against rib II
while protecting the body with ballistic packages made of biaxial and triaxial fabrics.
Fig. 21. The pressure course for sensors placed in the chest during the impact of the bullet against rib II while protecting the body with ballistic packages made of fabrics: (a) Biaxial;
(b) Triaxial.
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11

5.3. Bullet impact in the intercostal space on the lung position line
The main type of lung lesions resulting from a non-penetrating
bullet impact and deformation of the ballistic shield are local
parenchymal deformities that cause banded haemorrhages along
the ribs. The mechanism for the formation of banded haemorrhages
on the surface of the lungs and their potential injuries depends on
the scale of the displacement of the skeletal system into the
structure of the lung parenchyma [29]. The destruction of the
sternum model and the sensor S1 during the first impact of the
bullet could reduce the stability of the connection of the rib models
with the sternum model. Therefore, it could increase the injuries in
the intercostal area and thus obtain higher pressure values recor-
ded by sensors located near the point of bullet impact. Fig. 22 shows
the pressure courses for the Lu1 sensor with protection from
packages made of biaxial and triaxial fabrics. It should be noted that
the influence of the tested ballistic structures on the maximum
pressure amplitude was visible. For the right lung (Lu1), the sensor
registered twice the pressure value when protected with packages
made of biaxial fabrics (4 MPa) and for packages made of triaxial
fabrics, it was 2.1 MPa. It is confirmed that the use of multi-axis
fabrics for soft ballistic shields has the advantage of significantly
reducing the maximum pressure amplitude at the point of bullet
impact. By analysing the pressure curves of the Lu1 sensor, it can be
concluded that the nature of the shape and time of the pressure
curves is similar for both tested fabrics. In the final phase (from
t¼0.3 ms to t¼0.4 ms) of the impact of the BABT injury, when
protected with packages made of biaxial fabrics, a pressure increase
close to 2 MPa was noted. The probable reason for this may be the
stress and deformation waves of the soft ballistic packages, which
are generated during the dynamic interaction with the bullet.
Fig. 23 shows the pressure courses recorded by the sensors H1,
H2, Lu2, R2 and R3. The graphs do not show the waveforms from
the sensor located in the bridge (S1) because it was damaged
during the first attempt, when the bullet hit the bridge. Addition-
ally sensor Li1 and the sensorI1 did not register any values during
this bullet shot. Therefore, it can be assumed that the human body
model did not experience BABT injuries in the area of the intestine
and liver. Also, for the R1 sensor, no significant changes in the
pressure course were recorded. The pressure value for the H1
sensor was 0.14 MPa and for H2 it was 0.8 MPa, when protected
with packages made of biaxial fabrics. For the second tested fabric,
the values were lower and amounted to 0.05 MPa and 0.38 MPa,
respectively. The nature of the pressure curves for the H1 and H2
sensors for the tested ballistic fabrics, is similar. It should be noted
that there is a slight delay in the timeline, when protected with
packages made of triaxial fabrics. This is due to the geometric
structure of the triaxial fabric, which allows the kinetic energy of
the bullet to be distributed over a larger area than for a biaxial
fabric. As a result, the shock wave action is delayed and the
maximum pressure amplitude affecting the human body model is
reduced.
It should be noted that there was little pressure in the left hand
lobe of the lung (Lu2). A significantly low pressure value from the
Lu2 sensor was recorded, when protected with packages made of
triaxial fabrics while, during protection with packages made of
biaxial fabrics, it was about 0.07 MPa. Also, the sensor located on
the third rib on the left hand side (R2) registered small pressure
amplitudes. In the case of protection with packages made of triaxial
fabrics, the pressure value was only 0.02 MPa and, in the case of
protection with packages made of biaxial fabrics, the pressure was
about 0.07 MPa. It can be concluded that the stress waves and
deformations during the firing in the intercostal space along the
lung position is accumulated mainly on the right side of the chest,
i.e. in accordance with the place where the bullet was fired. It is in
this part of the chest that the greatest pressure amplitudes recor-
ded by the R3 sensor appear. During protection with packages
made of biaxial fabrics, the maximum pressure value of the R3
sensor was about 1.5 MPa. On the other hand, when protected with
packages made of triaxial fabrics, the pressure value of the R3
sensor was twice as low and amounted to 0.7 MPa. This confirms
the influence of the geometric structure of the multi-axial fabric
over the biaxial fabric. A significant advantage of the triaxial fabric
is having three systems of threads, which allow it to absorb a sig-
nificant part of a bullet’s impact energy and spread it over the
largest possible area, thus reducing the deflection of the ballistic
packages. This, in turn, leads to lower pressure amplitude at the
point of impact of the bullet and, possibly, less physiological com-
plications in the body. Medically, a BABT injury can cause pneu-
mothorax or haematoma, and bruise or rupture the lungs.
5.4. Bullet impact along the line of the liver
The abdominal wall is made of skin, subcutaneous tissue and
muscles that easily transfer energy and deformation to the internal
organs. The literature shows that the liver is an organ which is
susceptible to injuries, mainly due to its size and its location in the
abdominal cavity, as well as its structure (parenchymal organ). The
human body model did not have a liver model but in ballistic
research, the pressure on liver surface was measured by the sensor
Li1 located inside of gel in place where there is centre point on liver
surface. The pressure courses resulting from the impact of the
bullet in line with the liver position, depending on the tested bal-
listic fabric, are presented in Fig. 24.
According to Fig. 24, the pressure value for the Li1 sensor is,
again, lower when protected with packages made of triaxial fabrics
and amounts to approximately 0.7 MPa. However, for the second
tested fabric, the value is equal to 1 MPa. The dynamics of the
pressure increase of the Li1 sensor is similar for both of the tested
ballistic fabrics. After reaching the maximum values, the curves
gently descend. The structure of the biaxial fabric, which leads to
propagation of the shock wave in only two directions, may have an
influence on the maximum amplitude and the momentary pressure
increases and drops. As a result, the area covered by deformation is
smaller and the accumulated energy of the deformation and
destruction of the textile barrier may cause the packages to un-
dulate, leading to momentary pressure increases and drops in the
Li1 sensor curve.
The graphs in Fig. 25 do not show the waveforms from the
sensor located in the bridge (S1) because it was damaged during
Fig. 22. Pressure course for the Lu1 sensor during the impact of the bullet in the
intercostal space while protecting the body with a ballistic package made of biaxial and
triaxial fabrics.
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12

the first attempt, when the bullet hit the sternum. Also, for the
sensors H1, R1, R2 and R3, no significant changes in the course of
the pressure were recorded. In the case of protection with ballistic
packages made of biaxial fabric, after 0.9 ms the pressure was
recorded for the H2 sensor, which was about 10 kPa. The apparent
time delay may indicate blunt BABT trauma in the area of the heart
surface, caused by the shockwave following a non-penetrating
bullet impact. It should be noted that no significant changes were
recorded in the pressure course of the H2 sensor, when protected
with packages made of triaxial fabrics. It is, therefore, assumed that
the geometric structure of the triaxial fabric led to minimisation of
the BABT trauma to the heart surface.
The pressure curves for the Lu1 and Lu2 sensors were also
recorded while protected with packages made of biaxial fabrics,
and these were 15 kPa and 47 kPa, respectively. For the second
tested ballistic fabric, no significant changes were recorded for the
Lu1 sensor, while the pressure value was 16 kPa for the Lu2 sensor.
The tendency towards higher pressure values for the ballistic
packages made of biaxial fabrics was again visible, which may
result from the nature of the local deformation of the cover and the
impact on the body in a point-like manner. On the other hand, for
the structure of the ballistic packages made of triaxial fabrics, the
pressure force of the shield covers a larger area of the human body
model, which translates into a lower pressure value at the point of
impact. It should also be noted that, during a hepatic impact, the
shock wave is transmitted to the thoracic human body model. The
structure of the multi-axis fabric better absorbs the shock waves,
which leads to a reduction in the pressure value for the Lu2 sensor
and minimisation to values close to zero, for the Lu1 sensor.
It should also be noted that the sensor I1 only recorded a value
of about 8 kPa when protected with packages made of biaxial
fabrics. This confirms the belief that the biaxial structure leads to
Fig. 23. Pressure course for sensors placed in the chest during the impact of the bullet in the intercostal space on the line of the right lung while protecting the body with a ballistic
package made of fabrics: (a) Biaxial; (b) Triaxial.
Fig. 24. Pressure course for the Li1 sensor during the impact of the bullet on the line of
the liver with body protection from ballistic packages made of biaxial and triaxial
fabrics.
Fig. 25. Pressure course for sensors located in the chest and abdominal cavity during the impact of the bullet on the liver line while protecting the body with ballistic packages
made of fabrics: (a) Biaxial; (b) Triaxial.
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13

easier transfer of the stress wave in the area of the small and large
intestine, due to the weave geometries during the impact of the
bullet; this was not observed in the case of the packages made of
triaxial fabric. It should be stated that, in the model of the human
body there was no model of the small and large intestine, and the
recorded pressure values represented the responses of the ballistic
gel. The sequence of the BABT trauma during the impact of the
bullet along the line of the liver position may lead to breaking the
coatings (abrasion of the epidermis, bruising, swelling), bruising of
the subcutaneous tissue and muscles (ecchymosis, swelling) and
haematomas within them (fluid reservoirs filled with blood), to
rupture the liver with complications, i.e. bleeding into the
abdominal cavity.
5.5. Bullet impact in line with the location of the small and large
intestines
One of the types of abdominal damage that occurs when a non-
penetrating bullet hits the ballistic shield is the rupture of organs
containing gases or digestive contents. Fig. 26 shows the pressure
increase as a result of the impact, as a function of time, depending
on the given textile structure. During the impact of the bullet along
the line of the location of the small and large intestines, no sig-
nificant changes in the course of the pressure were recorded for the
sensors H1, H2, Lu1, Lu2, R1, R2, R3 and Li1. The waveforms from the
sensor located in the sternum (S1) were also not given, because it
was damaged during the first attempt when the bullet hit the
sternum.
The pressure value for the I1 sensor shown in Fig. 26 is lower
when using packages made of triaxial fabrics and amounts to
3.3 MPa. For packages made of biaxial fabrics, the pressure value for
the I1 sensor is 5.7 MPa. The tendency towards higher pressure
values for the ballistic packages made of biaxial fabrics was again
visible, which may result from the nature of the local deformation
of the cover and the impact on the body in a point-like manner. It
should also be noted that the duration of the potential BABT in-
juries is longer and that the pressure amplitudes over this period
are greater in the case of packages made of biaxial fabrics. There
was no model of the small and large intestines in the human body
model and so the recorded pressure values are the response of the
ballistic gel. The results of the ballistic tests showed that higher
pressure values, when protecting the body with a ballistic packet
made of biaxial fabrics, may lead to integuments of subcutaneous
tissue and muscles, mesenteric tearing or even intestinal rupture.
The mesentery is a thin membrane composed of two adjacent
peritoneal plaques, acting as a ligament for the internal organs of
the abdominal cavity, mainly the small intestine. A complication of
mesenteric rupturing may be life-threatening bleeding into the
peritoneal cavity and intestinal rupture may cause peritonitis. Both
of these conditions can be directly or indirectly fatal.
6. Conclusions
This article focuses on experimental research into the injuries on
the human body during the non-penetrating impact of a Para-
bellum 9 mm 19 mm FMJ bullet at a speed of 406 ±5 m/s, pro-
tected by ballistic packets made of biaxial and triaxial fabrics. In
experimental research, the fabrics had a comparable surface weight
and were made of the same Kevlar®29 yarn. The ballistic packages
were made of 30 layers.As part of this study, a physical model of the
human body was developed. The human body model consisted of a
model of the heart, lungs, and skeletal and muscular systems.
During bullet impact, the pressure forces were recorded using
sensors located at selected points of the human body. During the
firing, the bullet hit five selected places on the body that were
considered critical from the point of view of maintaining vital
functions. It was found that, during firing, pressure increases both
at the site of impact and in the internal organs, which can lead to
multiple organ damage. The experimental analysis shows that the
pressures exerted on specific organs are always lower in the case of
body protection with a ballistic packet made of triaxial fabrics
compared to a packet made of biaxial fabrics.
Experimental research has shown that, for the ballistic packages
made of triaxial fabrics, the pressure values were usually more than
half that for the ballistic packages made of biaxial fabrics. Addi-
tionally it was noted that for these packages, the number of shot
through layers was 12 for triaxial and 10 for biaxial type of con-
struction in each points of bullet impact. The larger number of shot
through layers in the ballistic package made of triaxial fabrics is
influenced by the hexagonal openings in the structure of the fabric,
as opposed to the biaxial fabric, which is completely enclosed.
It is assumed that the geometric structure of the fabric has a
significant influence on the maximum pressure amplitude. When
the bullet hit packages made of biaxial fabrics, the pressure was
more localised and covered a smaller area of the human body
model, which resulted in greater pressure at the point of impact.
However, for the second variant, the acting pressure force of the
packages made of triaxial fabrics was distributed over a larger area,
resulting in a lower value of maximum pressure at the point of
impact of the bullet. It should also be noted that the blunt BABT
trauma caused by hitting the sternum along the line of the heart
showed sternum fractures using both the packages made of biaxial
and triaxial fabric. The number of cracks and the area of damage to
the sternum were smaller when using the ballistic packages made
of triaxial fabrics. As a result of breaking the anatomical continuity
of the sternum, the internal structure of the chest (e.g. lungs, heart),
covered by the sternum, may be damaged. It should be added that
bone fractures may be multi-fragmentary and the damaged bone
fragments may constitute a so-called ‘secondary bullet’, which can
extend the area of damage. When the bullet was shot into the II rib,
while protecting the human body model with ballistic packages
made of biaxial fabrics, a rib fracture was found. This type of injury
was not found when examining a human body model protected by
packages made of triaxial fabrics.
Blunt BABT trauma can lead to a wide variety of injuries, ranging
from minor, non-life threatening injuries (with no significant
consequences for those affected) to significant, potentially fatal,
injuries.
Fig. 26. Pressure course for the I1 sensor during the impact of a bullet along the line of
the navel with the protection of the body by ballistic packages made of biaxial and
triaxial fabrics.
J. Pinkos, Z. Stempien and A. Sme˛dra Defence Technology xxx (xxxx) xxx
14

Declaration of competing interest
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
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