International Journal of Civil Engineering and Technology (IJCIET)
Volume 10, Issue 04, April 2019, pp. 1880–1888, Article ID: IJCIET_10_04_197
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication
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EXPERIMENTAL INVESTIGATION FOR THE
BEHAVIOR OF MULTI–LAYERED TARGET
UNDER PROJECTILE IMPACT
Murtadha Mohsen Mottar Al-Masoudy*
Department of Air conditioning and Refrigeration Technique Engineering Department,
Al-Mustaqbal University College, Babylon, Iraq
*Corresponding Author: Murtadha M. Mottar
ABSTRACT
This paper presents the ballistic performance of transparent polymer materials.
The need to design transparent projectile protective armour leads to research on
ballistic limit for the type of material. The ballistic resistance of different type of
layered sandwich polymer/plates was investigated polycarbonate and
Polymethylmethacrylate materials were chosen as test cases. The materials were
subjected to an impact against a rigid spherical steel projectile in the range of 100 –
650 m/s up impact velocity. The relationship between the initial and final velocity was
correlated and validated against existing literature. A very good agreement between
the experimental result and Ipson and Recht was presented. The propose empirical
equation between initial velocity and final velocity is obtained from statistical analysis
Key words: ballistic limit, high velocity impact, multi–layers polymers, residual
velocity
Cite this Article: Murtadha Mohsen Mottar Al-Masoudy, Experimental Investigation
for the Behavior of Multi–Layered Target under Projectile Impact, International
Journal of Civil Engineering and Technology 10(4), 2019, pp. 1880–1888.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4
1. INTRODUCTION
Transparent armor are commercially in stock and have been applied in a variety of military
and civilian systems and equipment including face shields, goggles, vehicle vision blocks,
windshields and windows, blast shields, and aircraft canopies. This research focuses on the
transparent polymeric materials primarily used for personnel and ground vehicle protection.
The subject of this investigation deals with materials that have the dual properties of being
visually transparent and resistant to penetration by high energy projectiles and fragments.
The layers typically within materials such as fiber-reinforced composites, polymers
materials, ceramics and/or metals. Basically, the aim is to use the polymers materials layer to
defeat, deform and erode the projectile, and use the composite layer to absorb the remaining
energy and increase the fracture and penetration resistance of the armor.
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Experimental Investigation for the Behavior of Multi–Layered Target under Projectile Impact
Ceramic transparently materials have been frequently and successfully used in armour
configurations all over the world [1,2]. Comparison of weights of steel and ceramic composite
transparent armours, which resist to the same type of ammunition, shows that by using
ceramic composite armours the mass can be reduced significantly. For ceramic transparent
armour application whole scale of oxide and non-oxide ceramic materials armours, such as
boron carbide (B4C), alumina (Al2O3), silicon nitride (Si3N4), silicon carbide (SiC), titanium
diboride (TiB2), a composite of Si and SiC (SiC–Si), etc., is considered. Besides final ballistic
properties also price, availability, production technology and workability decide about their
particular uses. From economical and technological point of view, the optimal material is
alumina [2]. This paper present an analytical model the ballistic limit of polycarbonate
materials [3].
There are many works dealt with transparent armoured material. Ballistic impact with
assuring on spherical strikers which provide more in plane damage on transparent material
was investigated by Goldsmith and Louie [4]. The proposed hybrid composite laminate
determinations the ballistic velocity [5]. Theoretical analysis of the impact behaviour of
polycarbonate is reported by Wright et. al [6]. The characterization of the deformation and
fracture behaviour of the transparent material namely Polycarbonate and
Polymethylmethacrylate material were reported by Wright et. al [7] and Wright [8]. This
present the failure forms of transparency polymer under high speed load by using spherical
projectile [9]. An analytical model was also proposed for perforation of ceramic sandwich
plates with honeycomb core as reported by Lo’pez-Puente [10]. The proposed analytical
solution for static analysis of composite materials [11]. More improvement in the
development of analytical model were developed to investigate the effect of perforation in
multi-layered composite planes subjected to high impact [12,13]. The present experimental
results the focused on initial velocity, residual velocity and energy absorption [14].This paper
used an energy balance model for Kevlar-29 and Al2O3 composite materials under high
velocity impact [15].
Finite element modeling has progressed essentially in the ability to predict failure of
materials under extreme dynamic loading conditions. One of the limitations of predictive
models is to simulate a complete dynamic materials properties data base for each of the
materials in the simulations. In order to substitute for parameters whose dynamic values were
extrapolated from their static or quasi-static properties. Baseline experiments are used to
recalibrate the models [16,17]. The proposed experimental method focused on energy
absorption, the ballistic limit for different shapes of bullet [18]. AUTODYN finite element
software [19] was normally used to perform simulation for non-linear transient dynamic
events such as ballistic impact, penetration and blast problems.
The importance of penetration and perforation into targets in both, military and civilian
application has made it the subject of many investigations. This research work is aim to
present an experimental investigation for high velocity impact on transparent materials
namely PC and PMMA. The experimental results will then be compared with Ipson and Recht
[20] equation. An empirical formula expressing a relationship between initial velocity and
final velocity these experimental were presented for polycarbonate and
Polymethylmethacrylate materials impacted with spherical projectile.
2. EXPERIMENTAL SETUP
The National Institute of Justice (NIJ) produced a standard ballistic testing method which is
well known and used worldwide (MIL-STD-662E, NIJ Standard) [21]. The experimental rig
setup according to NIJ is as shown in Figure 1.
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Figure 1. Typical Standard Ballistic testing Setup [21]
These standards are widely used by government agencies and armor manufacturers for
product acceptance testing. The energy absorption values for various hybrid configurations
can be obtained using these standards. Due to the exploratory nature of the ballistic research,
these test standards were chosen because they enable the user to gain an understanding of the
aspects of how to improve the ballistic impact resistance of various systems without requiring
a large amount of costly test samples. Also, these standards test for the maximum degree of
damage a particular projectile can incur. Testing according to these standards does have their
limitations. Because they are based on a limited amount of data points, it is difficult to acquire
results with a good statistical significance. Also, the standards lack a method for obtaining
dynamic information that may help explain the impact event. Damage characterization is
limited to energy absorption values and post impact inspection [21]. For tests with fully
penetration (perforation), a second chronograph was used after the target to measure the
resting velocity and evaluating the observed energy that was equal to the difference between
the incidents and resting kinetic energies. The new development through the building ballistic
test of this work was the design and builds a computerized chronograph not only measure the
after and before impact velocities but also to measure the approximate penetration time using
simplest method, specially, that the techniques use to measure the penetration time were vary
complex and expansive, in addition of that this techniques was covered with securities due to
their military applications, and pointed to their with a fuzzy view through the searches.
Figure 2. Schematic Representation of the Ballistic Rig.
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Experimental Investigation for the Behavior of Multi–Layered Target under Projectile Impact
The ballistic testing rig used in this work is shown schematically in Figure 2. Basically,
the rig consisted of 3 x 0.3 m rigid frame constructed from 2 x (1/8)” L beams to ensure the
rigidity as shown in Figure 3. Two rigid clamps were welded to the front of the frame on
which a gun barrel was mounted. The composite chronograph was fixed behind the gun and
the target holder was welded in location between the second and the third screen of the
chronograph.
Figure 3. Ballistic Impact Rig.
The launching gun used for the test was fabricated and constructed specifically for this
purpose. Briefly, the basic design feature includes a smoothbore gun barrel of 7.85 mm
nominal internal diameter and 750 mm length. The L/D ratio was approximately 95.5. The
smooth bore enable the use of the gun to propel rigid projectile of any head shape. Moreover,
the cartridge housing situated at the end of the gun was constructed so as to accommodate
many kinds of powder gun cartridge. This capability enables accelerating the projectile to
velocity range from 60 to 900 m/s. Finally, the materials and dimensions were chosen so as to
withstand internal pressure as high as 3000 bars resulting from detonation of the powder gun
charge.
The details description of the launching gun parts are as follows:

The gun barrel: A long cylinder made of special treated alloy steel with 27 mm outer diameter
and 7.85 mm bore, one of the barrels end was threaded internally to be fastened to the
envelope housing.

The cartridge envelope: a steel cylinder of 27 mm outside diameter and 55mm length, the
inside configuration was machined so as to envelop the two types of cartridges used in this
work

The envelope housing: A hollow steel structure with an internal thread at one end through
which it is fastened to the gun barrel. The other end is specially designed to be securely
joining to the breach while the inside bore holds the cartridge envelope.

The breech: made to be joined to the envelope housing at one end and to carry the firing pin at
the other.

The firing pin: with conical head configuration suited for the capsule initiated cartridges. The
gun is mounted on two clamps and firmly secured by bolts and nuts. The lower parts of these
clamps are welded to a steel structure that is fixed to the test rigs base.
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The test specimens were rigidly clamped between two steel frames. Bolts at the corners
and mid-sections of the steel frame were tightened to insure a rigid mount on all four edges of
the test specimen. These two steel frames (10 mm thick) were attached to a support structure.
The test specimen was perpendicular to the line of flight of the bullet at the point of impact.
3. RESULTS AND DISCUSSION
Figures 5, 6 and 7 shows photos taken from several targets of several thicknesses of Poly
methyl methacrylate (PMMA) material. The area of impact experiences high stresses both in
the radial and hoop directions upon impact. However, the star crack pattern proves that the
stresses in the hoop direction becomes much higher than the maximum tensile stress
permitted in the material causing eventually the fracture of the material in that vicinity in a
star shape.
As the projectile moves on driven by the driving momentum through the target material,
effected zone shows radial shaped cracks forming several concentric cracks around the
projectile. Target contact zone on further progress of the projectile, the cracked zone is
pushed forward in front of the projectile tip in a conical plug form. Finally the projectile
emerges from the rear target side pushing a plug of two to three times the diameter of the
lumping projectile.
Sandwich plate of Figure 4 shows a photo showing target PC-PMMA after undergoing
impact by the spherical projectile at 616.33 m/s the first PMMA layer showed similar failure
mode to that shown in Figure 5.
PMMA PC
Vi=616. 33 m/s
5 mm 2.5 mm
Figure 4 Final velocity Vr versus initial velocity Vi for PMMA and PC by spherical projectile
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Experimental Investigation for the Behavior of Multi–Layered Target under Projectile Impact
PMMA
Vi=200. 344 m/s
5 mm
Figure 5. Final velocity Vr versus initial velocity Vi for PMMA by spherical projectile
PMMA PMMA
1600
h = 10 mm
Ipson & Recht
Vi=352.34 m/s
exp.
1200
V(r)
5 mm 5 mm
800
400
0
0
400
800
1200
1600
V(i)
Figure 6 Final velocity Vr versus initial velocity Vi for two pieces of PMMA by spherical projectile
1600
PMMA PMMA PMMA
h = 15 mm
Ipson & Recht
exp.
1200
Vi=340. 52 m/s
V(r)
5 mm 5 mm 5 mm
800
400
0
0
400
800
1200
1600
V(i)
Figure 7 Final velocity Vr versus initial velocity Vi for three pieces of PMMA by spherical projectile.
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The final velocity into PC and PMMA targets were plotted against the initial velocity as
shown in Figures 4, 5, 6, and 7 for targets thickness 2.5, 5, 10 and 15 mm respectively. The
comparison is made with an empirical formula suggested by Ipson and Recht [20]. The results
showed a very good agreement between the experimental results and the correlation by Ipson
and Recht.
The Ipson and Recht [20] formula is a power function of the initial velocity and the
ballistic limit as follows:
Vr  Vi 2  Vb2
(1)
Where,
Vr is the final velocity, (m/s)
Vi is the initial velocity, (m/s)
Vb is the ballistic limit, (m/s)
The relationship between initial velocity and final velocity is obtained from statistical
analysis and resulted an empirical formula as follows:
Vr  70.01317  0.931249Vi  96.31TE 
0.041263
(2)
With correlation coefficient = 99.37% and mean error = 7.1%
Where,
T = thickness of targets (mm)
E = modules of elasticity (N/m2)
Figures 8 and 9 shows a comparison of the results obtained applying the empirical
formula from equation (2) that was deduced in this work to the experimental results already
published in literature. It is clearly shown in both Figures 8 and 9 that the correlation is also
applicable to 2024-0 Aluminum material. Carbon Steel were used as targets in the related
works [22,23].
600
empirical formula
Landkof & Goldsmith
V(r)
400
200
0
0
200
400
600
V(i)
Figure 8. Comparison empirical equation with Landkof and Goldsmith [22]. (Targets made of 2024-0
Aluminum, E = 72.4 GPa, thickness = 3.175 mm)
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Experimental Investigation for the Behavior of Multi–Layered Target under Projectile Impact
500
empirical formula
exp. Ghabban
400
V(r)
300
200
100
0
200
300
400
500
V(i)
Figure 9. Comparison empirical equation with Al-Ghabban [23] (Targets made of carbon steel E =
210 GPa, thickness = 6 mm)
4. CONCLUSIONS
The following conclusion can be made:

The ballistic impact behavior of PMMA and PC materials were found to be different.

Different failure mode were found for different thickness of PMMA sandwich plate

A empirical relationship between the initial velocity and the final velocity was found as
V  70.01317  0.931249V  96.31TE 0.041263 . This empirical relationship was found
r
i
applicable to other type of materials other than that studied in this work.
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