Composite Structures 277 (2021) 114638
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Composite Structures
journal homepage: www.elsevier.com/locate/compstruct
Effect of the temperature on ballistic performance of UHMWPE laminate
with limited thickness
Mingjin Cao, Li Chen *, Rongzheng Xu, Qin Fang
Engineering Research Center of Safety and Protection of Explosion & Impact of Ministry of Education, Southeast University, Nanjing 211189, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
UHMWPE laminate
Ballistic
Temperature
Thickness
Projectile penetration
Ultra-high molecular weight polyethylene (UHMWPE) is widely used as bulletproof material, but it has evident
temperature sensitivity, which can lead to the fluctuation of impact resistance. To explore the effect of tem­
perature on the ballistic performance of UHMWPE laminates, ballistic experiments were conducted at different
temperatures of − 20, 10, 80, and 95 ◦ C, respectively. The ballistic efficiency, back face deformation and opening
hole characteristic of the laminates were compared and analyzed. At all considered temperatures, the laminates
with a thickness of 10 mm were perforated, while those with thicknesses of 20 and 30 mm were not, and the
ballistic response of the 20 mm laminates changed most strongly with the variation of the temperature. The
temperatures of 10 and 80 ◦ C had no significant effect on the deformation and failure of UHMWPE laminates,
while the laminates hardened evidently at − 20 ◦ C and softened evidently at 95 ◦ C, and the temperature treat­
ments at − 20 ◦ C and 95 ◦ C generally led to the highest and lowest protection performance, respectively. The
bulletproof application of UHMWPE laminates at temperatures above 80 ◦ C need extra attention and further
investigated. The results of this study will be useful for the design of more flexible and effective UHMWPE-based
protective equipment.
1. Introduction
homogeneous armor steel[12], high-hardness armor steel[13] and highperformance aluminum alloy[14]. They found that, at the same areal
density, v50 of the UHMWPE laminate was up to two to three times
higher than that of the metal materials. Reddy et al.[15] compared the
ballistic efficiency and failure mechanism of UHMWPE laminate with
that of E-glass laminate against same lead-core bullets. It was found that
the E-glass laminate was perforated, while the UHMWPE laminate sur­
vived. Videos captured with a high-speed camera revealed that under
the impact of a bullet at 370 m/s, the E-glass laminate is mainly sub­
jected to shear failure and local deformation, while the UHMWPE
laminate is mainly subjected to fiber tension and global deformation
[15]. This indicates that the UHMWPE material is not only lightweight
but also has the advantage of high energy dissipation capability due to
the large deformation. Furthermore, studies have also been conducted
on factors that affecting the ballistic performance of UHMWPE com­
posites. Zhang et al.[16] investigated the influence of the ply stacking
angle on the penetration resistance of UHMWPE laminates and found
that, laminates with an orthogonal stacking sequence have a higher
ballistic limit, while ARL X hybrid laminates (fibers rotated by 22.5◦
every two plies for the rear 25% of plies) experience smaller back face
Ultra-high molecular weight polyethylene (UHMWPE) is an un­
branched linear polyethylene with especially high specific strength and
specific modulus. In 1979, the DSM company produced a highperformance polyethylene fiber through the gel spinning process and
patented it[1], attracting interest of a wide range of researchers.
UHMWPE has been commercially produced since the 1990 s and
UHMWPE materials are now widely used for various applications such
as protective armors[2], anchor ropes[3], fishing nets[4], and cutresistant clothing[5]. Due to its excellent impact resistance and low
enough density[6], UHMWPE fiber has a broad application potential in
ballistic protection and material weight reduction.
Nguyen et al.[7–9] studied the ballistic efficiency of UHMWPE
laminate under the impact of wedge-shaped fragment simulated pro­
jectile. They found that the ballistic limit (v50 ) of the UHMWPE laminate
is approximately 40–90% higher than those of Kevlar KM2 and E-glass
[10] composite laminates at the same areal density. Similar conclusion
was also draw by Bajya et al.[11]. Nguyen et al.[8] also compared the
protection efficiency of the UHMWPE laminate with rolled
* Corresponding author.
E-mail address: li.chen@seu.edu.cn (L. Chen).
https://doi.org/10.1016/j.compstruct.2021.114638
Received 11 July 2021; Accepted 2 September 2021
Available online 6 September 2021
0263-8223/© 2021 Elsevier Ltd. All rights reserved.
M. Cao et al.
Composite Structures 277 (2021) 114638
deformation (BFD). Similar characteristics were also observed by Lionel
et al.[17,18]. Wang et al.[19] studied the influence of the matrix type on
the anti-penetration performance of UHMWPE laminates and found that
when a flexible matrix is used, the laminate experiences a large defor­
mation, whereas when a rigid matrix is used, the laminate shows sig­
nificant local area failure and a lower ballistic limit. Tan et al.[20]
investigated the influence of the projectile geometry on the failure
mechanism of UHMWPE laminates and found that when the laminates
were penetrated by flat-nosed and hemispherical projectiles, shear and
fiber tensile failure were the dominant failure mechanisms, respectively.
However, sufficient small damage and delamination of the laminates
were observed when conical and ogival projectiles were used. Nguyen
et al.[7] studied the effects of the laminate thickness on the ballistic
performance of UHMWPE laminate, and it was showed that the lami­
nates have evident staged failure characteristics during the penetration
process, i.e., the penetration failure characteristics change along the
thickness. Thin laminates are dominated by punching failure and BFD,
while thick laminates also exhibit large-area delamination. Similar
phenomenon was also observed by Irenmonger et al.[21,22].
Despite numerous ballistic studies that have been conducted on
UHMWPE laminates, studies on the penetration resistance of UHMWPE
laminates at different temperatures are still rare[23,24]. Such in­
vestigations are of great significance for elucidating the protection
reliability of UHMWPE laminates under different environments. Peijs
et al.[25] studied the mechanical properties of UHMWPE fibers at
various temperatures in the range from − 40 to 80 ◦ C and found that
UHMWPE fibers tend to become brittle at low temperatures. As the
temperature decreased, they observed an increase in the tensile modulus
and strength but a decrease in the failure strain. By contrast, at high
temperatures, they observed that the fiber exhibited ductile tensile
fracture, and the tensile modulus and strength decreased with increasing
temperature. Kromm et al.[26] and Dangora et al.[27] studied the ten­
sile properties of UHMWPE fiber in high-temperature environments
experimentally. It was found that the crystalline structure of the
UHMWPE fiber is damaged at high temperatures[28], causing a
decrease in the tensile modulus and strength of the fiber. The modulus
decreased faster for temperatures below 70 ◦ C, while the strength
decreased faster for temperature above 70 ◦ C. Lässig et al.[29] reported
that the tensile modulus and tensile strength of the fiber have a signif­
icant impact on the ballistic performance of the UHMWPE laminate.
According to the reports by Kromm et al.[26] and Dangora et al.[27], a
temperature of approximately 70 ◦ C might be the transition temperature
for the ballistic characteristics of UHMWPE laminates, however, there is
still limited confirmatory research in the open literature. It is known that
UHMWPE fiber has low melting point, about 130–145 ◦ C, which has
been a limitation for its application in protection field. According to
Yang[24], thermal damage of UHMWPE fibers is obvious and will lead
to a non-negligible degradation in impact resistance of UHMWPE plates,
however, the specific influence has not been clearly identified. Sap­
ozhnikov et al.[30] studied the influence of temperature on the ballistic
performance of UHMWPE laminates in the temperature range from − 60
to 60 ◦ C. The results indicate that although the influence of temperature
in this range on the v50 of UHMWPE laminates is negligible, at low
temperatures, the variation in the protective performance of the lami­
nates is slightly greater and should be considered. However, failure
characteristics of the UHMWPE laminates outside the temperature range
of − 60 to 60 ◦ C were not further investigated.
In our previous study, the ballistic performance of UHMWPE lami­
nates at room temperature (10 ◦ C) has been fully discussed[31]. To
address the limitations of the existing research, field firing tests of
UHMWPE laminates at − 20, 80, and 95 ◦ C were further investigated.
The deformation process, failure characteristics, and penetration depth
of the laminates at different temperatures were compared and discussed.
The influence of temperature on the penetration resistance and failure
mechanism of the UHMWPE laminate were analyzed and summarized.
2. Experiment
2.1. Preparation of the specimen
The UHMWPE laminate studied in this research was manufactured
by North Jiarui Defense Technology Co., Ltd. (China). The laminates
were molded through the hot-pressing technology, and unidirectional
laminas (fibers were produced through gel spinning-ultra-drawing
technology and laid in parallel in each lamina) were stacked orthogo­
nally and then pressed into a composite laminate with a [0/90]n struc­
ture by a precision hydraulic molding machine under high pressure and
high temperature. The fiber volume content of the UHMWPE laminate
was 90%, and thermoplastic polyurethane was utilized as the matrix.
The density of the laminate is 0.97 g/cm3. The laminate in-plane
dimension was 500 × 400 mm, and the laminate thicknesses were 10,
20 and 30 mm, respectively.
The experimental bullet was a standard steel core bullet with a
caliber of 7.62 × 39 mm. Its warhead length, and weight (no cartridge
case) were 26.8 mm and 7.9 g, respectively. The material composition of
the warhead jacket and the steel core were copper-clad steel and lowcarbon steel, respectively.
2.2. Temperature treatment
The temperature treatment of the UHMWPE laminates consists of
three parts: temperature change, temperature measurement, and tem­
perature preservation, as shown in Fig. 1. The outdoor temperature of
the shooting field was 10 ◦ C. An electrically controlled low-temperature
container was employed to decrease the temperature of the UHMWPE
laminate down to − 20 ◦ C, and two hydrothermal containers with an
Fig. 1. Temperature treatment procedure of the UHMWPE laminates.
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Composite Structures 277 (2021) 114638
accuracy of ± 1 ◦ C were used to increase the temperature of the laminate
to 80 and 95 ◦ C, as shown in Fig. 1a. All laminates were treated at a
constant temperature for 24 h prior to firing test. Because the boiling
point of water at standard atmospheric pressure is 100 ◦ C and consid­
ering the actual heating capacity and safety of the hydrothermal
container, the maximum temperature was set to 95 ◦ C. A pre-prepared
film-type temperature sensor was embedded into the laminate (in the
middle, along the thickness), as shown in Fig. 2. A handheld 4-channel
K-type thermocouple thermometer with an accuracy of ± 0.1% was used
to measure the laminate temperature; the thermocouple converts the
temperature signal into a thermoelectromotive force signal and then
converts the thermoelectromotive force signal into the temperature of
the measured medium. Due to the limited thickness of the laminate, the
temperature in the middle of the laminate along the thickness direction
was used as a rough estimate of the bulk temperature of the laminate,
and the temperature difference between the surface and the core of the
laminate was ignored. It is assumed that the temperature value indicated
by the sensor is not affected by the in-plane position when the minimum
distance, Ls , from the outer edge of the sensor to the edge of the laminate
is greater than 50 mm; thus, the value of Ls was approximately 50 mm.
To reduce the local pre-delamination of the laminate that will affect the
accuracy of the ballistic test results due to the built-in temperature
sensor wire, a transition area of approximately 20 × 20 mm was added
at the location of the exposed wire during the laminate manufacturing
process, as indicated by the red circle in Fig. 2.
Due to the limited test conditions, it was not possible to complete the
shooting during the temperature change procedure (Fig. 1a). Therefore,
cotton cloths were placed together with the laminates in the constant
temperature containers for 24 h treatment (Fig. 1a). And when the
cotton cloths and the laminates were removed together before firing
testing, the laminates were wrapped in the thick cotton cloth and
insulated in a foam box (Fig. 1b) to reduce the heat change during the
removal of the target laminates from the constant temperature con­
tainers and their fixation on the bracket and shooting (this process took
approximately 3–5 min). For each laminate, only the sample to be shot
was removed from the temperature container to the shooting field.
Table 1 lists the actual bulk temperature of the UHMWPE laminates
at the time of shooting (Fig. 1c). Because the laminate inevitably un­
dergoes temperature change, the actual test temperature will deviate
from the design temperature. In the − 20 ◦ C firing test, the actual
temperature of the laminate was in good agreement with the design
temperature. Except for the slightly large deviation of the 10 mm
laminate at 80 and 95 ◦ C, the temperature deviations of the laminates
were all in the range of 1–8 ◦ C. According to Kromm et al.[26] and Zhu
et al.[28], when the temperature was approximately 80 or 95 ◦ C, the
variation of the temperature within 8 ◦ C had no significant effects on the
Table 1
Temperature of the UHMWPE laminates at the time of shooting.
Laminate
Temperature
10 mm
Design (◦ C)
− 20
80
95
20 mm
− 20
80
95
30 mm
− 20
80
95
Actual (◦ C)
− 18
60
80
− 19
73
87
− 16
74
90
tensile modulus and fracture strain of UHMWPE fiber. Besides, although
the temperature sensitivity of the tensile strength of the UHMWPE fiber
increased when the temperature exceeded 80 ◦ C, it is considered that the
decrease of laminate temperature within 8 ◦ C would not cause a sig­
nificant change in the tensile strength of the UHMWPE fiber because the
damage of the fiber was irreversible and the temperature change was
small. Therefore, the decrease in the temperature within 8 ◦ C will not
lead to an evident change in the ballistic resistance of the UHMWPE
materials[26], and the actual test temperature is considered to generally
meet the shooting requirements.
2.3. Field firing
The experimental arrangement of the field firing is illustrated in
Fig. 3. After bullets launched perpendicularly by an 81–1 automatic
rifle, the bullet initial velocity (approximately 715 ~ 720 m/s) was
measured through a pair of paralleled light screens. The laminate to be
tested were bolted and fixed at four corners. The distance L1 ,L2 and L3 in
Fig. 3 were 6.0, 1.1 and 1.2 m, respectively. As shown in Fig. 4, a highspeed camera was utilized to record the laminate deformation process
and the residual velocity of the bullet, it was located to the right (relative
to the incident direction) of the laminate horizontal centerline. Ac­
cording to GJB4300A − 2012[32], the influence of the boundary con­
ditions and the mutual interference of impacts can be ignored when the
distance between impact points and the distance from impact points to
the laminate edges were no less than 51 and 75 mm, respectively. In
addition, to avoid the influence of fiber pre-damage on the ballistic
response of the laminate, the impact points must be set on different fiber
bundles. Therefore, one laminate was arranged to be shot three times, as
shown in Fig. 4. In the test conducted at 10 ◦ C, each bullet was fired and
measured separately; for the tests at − 20, 80, and 95 ◦ C, three bullets
were fired at once.
3. Results and analysis
3.1. Deformation process and BFD depth
The laminate deformation process was recorded compared with the
test at 10 ◦ C used as control, as shown in Table 2. Images obtained at
other temperatures that were highly similar to the deformation process
at 10 ◦ C are omitted. Under penetration, the 10 mm laminate structures
did not bend. It is observed from the moment 2 of the 10 mm laminates
(both 10 and 95 ◦ C) that when the bullet penetrated into the interior of
Fig. 2. Location of the temperature sensor.
Fig. 3. Experimental arrangement of the field firing.
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Composite Structures 277 (2021) 114638
3.2. Final failure
3.2.1. UHMWPE laminates
The final failure characteristics of the 10 mm UHMWPE laminates
were given in Fig. 6. It was observed that there was no opening
expansion and no evident difference in the appearance of these openings
on the front surface, suggesting that the early failure of the laminates
treated at different temperatures was shear failure and the penetration
law was similar. On the back surface, a diamond-shaped BFD with a
diagonal length of approximately 100 mm (the length of the black
square lattice on the laminate is 50 mm) can be observed on the lami­
nates treated at − 20 and 10 ◦ C (results at 80 ◦ C was also the same). The
laminate treated at 95 ◦ C displayed a smaller-area BFD, but the fibers
were strongly torn from the back-face lamina. This indicated that it was
easier to perforate the laminate and that there was a decrease in the
shearing resistance of the laminas under 95 ◦ C. It is observed from
Fig. 6b that all of the delamination of the 10 mm laminates was local­
ized. Compared to the 10 ◦ C treatment, both the − 20 and 95 ◦ C treat­
ments had an effect of decreasing the delamination of the laminate, and
the effect at 95 ◦ C was more pronounced.
As observed in Fig. 7a, the failure characteristic of the front faces on
the 20 mm UHMWPE laminate was similar to that of the 10 mm lami­
nates. However, because the laminates with a thickness of 20 mm were
not perforated, there was no through-hole, and all of the laminates
displayed a diamond-shaped BFD on their back faces. With the increase
in the testing temperature from − 20 to 95 ◦ C, the BFD area of the
laminates tends to increase monotonically. For example, the diagonal
lengths of the BFD areas were approximately 80, 100 (results at 80 ◦ C
was also the same) and 150 mm after the treatments at − 20, 10, and
95 ◦ C, respectively. Therefore, the delamination of the 20 mm laminates
showed a global tendency, and the BFD depth of the 20 mm laminates
did not increase significantly even though high-temperature softening
occurred (Fig. 5b). The degree of delamination increased monotonically
with the rising treatment temperature, as shown in Fig. 7b. It can be
conjectured that for the laminates with large BFD, the lateral delami­
nation was closely related to the area of BFD.
For the 30 mm UHMWPE laminates, there was no evident difference
in the front openings at all temperatures, as can be seen in Fig. 8a. At
10 ◦ C, the back bulge of the 30 mm laminates was sufficiently small and
was approximately circular (results at − 20 ◦ C was also the same). With
the increase in the test temperature, the back face of the laminates began
to display a diamond-shaped BFD at 80 and 95 ◦ C, and the BFD depth at
95 ◦ C was approximately 2.5 times greater than that at 10 ◦ C (Fig. 5c).
Different from that of the 20 mm laminates, the delamination of the 30
mm laminates decreased with increasing temperature (Fig. 8b). This
may be due to the fact that although the laminate softened at high
temperature, the deformation resistance of the 30 mm laminate was
larger than that of the 20 mm laminate due to the larger thickness.
Under the combined action of the temperature and laminate thickness,
the failure occurred locally.
Fig. 4. Details of UHMWPE laminates.
the laminates, there was no BFD on the laminate, indicating that the
laminates were dominated by shear plugging failure. In the deformation
process of moments 3–5, slight BFD was observed. After the perforation
at 10 ◦ C, the ejection of shear plug and the disintegrated warhead
structure were photographed, and the bullet core was slightly deformed,
as shown at moment 5. However, after the perforation of 10 mm lami­
nate at 95 ◦ C, the bullet was still intact with no pronounced damage and
separation, and only the ejection of the fiber and matrix can be observed
on the back of the target laminate. It is suggested that the temperature
treatment from − 20 to 80 ◦ C has no evident effect on the failure
characteristic of 10 mm laminates. However, the UHMWPE laminate
treated at 95 ◦ C softened significantly, and the decrease in its ballistic
performance was nonnegligible. The 20 and 30 mm laminates were not
perforated at all testing temperature. During the firing tests from 10 to
95 ◦ C, the 20 mm laminates displayed no overall bending. However, due
to the low-temperature hardening at − 20 ◦ C, the BFD of the 20 mm
laminate was significantly lighter that at 10 ◦ C. Under the impact from
− 20 to 80 ◦ C, there was almost no visible deformation in 30 mm
laminate. However, due to the material softening caused by 95 ◦ C
treatment, an evident BFD was observed in the 30 mm UHMWPE
laminate, as shown at moment 4.
It can be seen from Fig. 5a that during penetration, the 10 mm
laminates treated from − 20 to 80 ◦ C has maximum BFD depths of
12–16 mm, while after heat treatment at 95 ◦ C, the BFD of the laminate
dropped sharply under the same shooting conditions, and no obvious
deformation was observed with the high-speed camera (Table 2). This
implies that the laminate softened and was easily perforated at tem­
perature higher than 80 ◦ C . For the 20 mm laminates treated from 10 to
95 ◦ C, the BFD depths were in the range of 16–18 mm (Fig. 5b). How­
ever, the smallest BFD depth was observed at − 20 ◦ C. This may be due
to the hardening at low temperatures[25,33] that increased the defor­
mation stiffness of the laminate, and because there was no penetration in
the 20 mm laminate, the increase in the deformation stiffness resulted in
a reduced deformation. At 95 ◦ C, the 20 mm laminates shown no sharp
decrease of BFD depth like that of the 10 mm laminate, this is due to the
bullet was intercepted and large area delamination occurred in lami­
nates, which will be discussed in detail in section 3.3. With the continue
increase in laminate thickness, the deformation resistance of UHMWPE
laminates was enhanced, and the BFD depths of the 30 mm laminates
treated from − 20 to 80 ◦ C decreased to the range of 4–7 mm. It is
important to note that for the 30 mm laminate treated at 95 ◦ C, the BFD
depth increased sharply and reached 12.5 mm, which was 2.5 times
greater than that of the laminate treated at 10 ◦ C. This shows that in the
thick (30 mm) laminates, the influence of the decrease in the deforma­
tion stiffness due to the high-temperature softening[26] on the BFD was
greater than the effect of the increase in the deformation resistance due
to the increase in the thickness.
3.2.2. Bullet cores
Bullets that perforated the 10 mm laminates were not recovered.
However, an examination of the videos captured by the high-speed
camera revealed that there was a separation between the bullet com­
ponents (except for the test at 95 ◦ C), and no evident upsetting defor­
mation occurred in the bullet core, as shown in Fig. 9a-1. During the
impact on the thicker laminates, the bullets core experienced “mush­
room head” shaped deformation, as can be seen from Fig. 9b, where D0
and Dt are the bullet diameters before and after penetration, and Lb is the
residual bullet core length after penetration. Due to the water jet cutting
conducted on the cross section of the impact points, the bullet cores are
half displayed in Figs. 9a-2 and 9a-3. And it can be seen from the
comparation of deformed bullet cores after penetrating the 20 and 30
mm laminates (Fig. 9a-4) that, the thicker the laminates are, the larger
the deformation degree of the bullet cores will be. The large deformation
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Composite Structures 277 (2021) 114638
Table 2
Deformation process of UHMWPE laminates.
Thickness (mm)
Moment 1
Moment 2
Moment 3
Moment 4
Moment 5
vr (m/s)
10(10 ◦ C)
577.7
10(95 ◦ C)
619.0
20(10 ◦ C)
0
20(− 20 ◦ C)
30(10 ◦ C)
0
3–4(95 ◦ C)
5
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Composite Structures 277 (2021) 114638
Fig. 5. BFD depth of UHMWPE laminates at different temperatures.
Fig. 6. Failure characteristics of 10 mm UHMWPE laminates.
of the bullets means that the UHMWPE laminate has high protection
efficiency for low carbon steel projectile.
Table 3 lists the average dimensions (one laminate was shot three
times) of the bullet cores after deformation. The results at 80◦ C are not
shown here because the bullets could not be retrieved during the water
jet cutting process. However, according to the UHMWPE laminates
treated at 10 and 80 ◦ C displayed similar failure characteristics, it can be
inferred that the bullet deformation degree at 10 ◦ C can be an approx­
imation for that at 80 ◦ C. It is observed from the data presented in
Table 3 that for a given thickness, the average degree of deformation of
the bullet cores was the lowest at 95 ◦ C. Compared to those of the bullet
at 10 ◦ C, the residual lengths Lb of the bullet cores at 95 ◦ C were
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Composite Structures 277 (2021) 114638
Fig. 7. Failure characteristics of 20 mm UHMWPE laminates.
Fig. 8. Failure characteristics of the 30 mm UHMWPE laminates.
Fig. 9. Upset and deformed bullet cores.
6.4–8.7% longer, and the maximum upset diameter was 6.8–13.8%
smaller. Although the dimensions of bullet cores at − 20 ◦ C were similar
to those at 10 ◦ C after penetrating the 20 mm laminates, Lb of the bullet
cores after the penetration of 30 mm laminates at − 20 ◦ C was the
smallest and was 5.8% lower than that at 10 ◦ C. It can be inferred that
for the bullet cores processed from low-carbon steel materials, the lowtemperature treated UHMWPE laminates have higher protection effi­
ciency, while the opposite is true for high-temperature treated
UHMWPE laminates.
Table 3
Average dimensions of the deformed bullet core.
Laminate
Temperature (◦ C)
Lb (mm)
Dt (mm)
20 mm
10
− 20
95
10
− 20
95
10.9
10.9
11.6
10.4
9.8
11.3
13.2
12.9
12.3
13.8
13.9
11.9
30 mm
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Composite Structures 277 (2021) 114638
3.3. Penetration depth and diameter
Therefore, when the laminate thickness was close to the critical perfo­
ration thickness (without evident thickness effect of 30 mm laminate
that leads to deformation resistance), L of the 20 mm laminate was
smaller than that at 10 ◦ C due to the laminate consumed a high amount
of energy through the larger BFD depth (Fig. 5) and a wider range of
delamination.
3.3.1. Defensive capability
Due to the perforation of 10 mm UHMWPE laminates at all tem­
peratures, the bullet residual velocities vr were utilized for the com­
parison of the defensive capability of 10 mm laminates. As shown in
Fig. 10a, vr of the bullets increased monotonically with increasing
temperature. The bullet residual velocity at 10 ◦ C was 577.7 m/s, and
the laminate absorbed approximately one-third of the bullet energy,
while at − 20 ◦ C, vr was 5.7% lower and the kinetic energy absorption
rate was 7.2% higher, and at 80 and 95 ◦ C, vr of the bullet was 2.9% and
7.1% higher, and the energy absorption rate was 3.7% and 9.5% lower,
respectively. These results showed that the energy absorption capacity
of the laminates treated at 80 ◦ C was the closest to that of the laminates
treated at 10 ◦ C. Compared to that at 10 ◦ C, the anti-penetration ability
of the laminate was enhanced at low-temperature (− 20 ◦ C) and reduced
at high temperature (95 ◦ C). At − 20 ◦ C, the energy absorption rate of
the laminate was 15% higher than that at 95 ◦ C, indicating that extreme
temperatures had a significant effect on the penetration resistant of the
UHMWPE laminates.
The maximum penetration depths L of the 20 and 30 mm laminates
at different temperatures were compared to explore the influence of
temperature on ballistic efficiency, as shown in Fig. 10b. As the tem­
perature increased from − 20 to 95 ◦ C, L of the 20 mm laminate first
increased and then decreased, while for the 30 mm laminate, there was a
monotonically increasing trend. At 10 ◦ C, L of the 20 and 30 mm
laminate were 13.1 and 7.9 mm, respectively. Due to the bullet core
experienced more severe deformation when impacted the 30 mm
laminate, its penetration ability decreased evidently. Among the inves­
tigated temperatures, the penetration depths of the laminates were the
smallest at − 20 ◦ C. Compared to that at 10 ◦ C, L of the 20 and 30 mm
laminates at − 20 ◦ C were 57.3% and 16.5% lower, respectively. This
confirmed that the low-temperature treatment increased the ballistic
efficiency of the UHMWPE laminate. At 80 ◦ C,L of the 20 and 30 mm
laminates were closest to those at 10 ◦ C, and the maximum depths de­
viation was approximately 3 mm. This indicated that the 80 ◦ C treat­
ment had a relatively limited influence on the ballistic performance of
UHMWPE laminates. At 95 ◦ C, according to literature[28,33,34],
UHMWPE fiber would undergo thermal softening and crystal structure
damage[28], leading to a decrease in the fiber tensile modulus and
tensile strength[34,35]. Therefore, the penetration depth of the 30 mm
laminate was 58.2% higher than that at 10 ◦ C. And according to the
testing results of this study, at such high temperature, UHMWPE lami­
nates were also more prone to delamination failure, as shown in Fig. 11c.
3.3.2. Failure mechanism
The cross-sections of laminate opening holes were given in Fig. 11.
The results at 80 ◦ C were omitted because the failure characteristic at
80 ◦ C were similar to those at 10 ◦ C. From Fig. 11a, it can be seen that
the perforated part of the 10 mm laminate at all temperatures showed
two-stage characteristics. In the first stage, a small punching hole with
uniform diameter formatted, as shown schematically in Fig. 12a, where
Di and Li were hole diameter and penetration depth, respectively. The
next stage was the formation of a large punching hole with variable
cross-section, as shown schematically in Fig. 12a, where Du , Dp and Lp
were the initial perforation diameter, the perforation diameter of the
ejection position and the penetration depth, respectively. The diameter
decreased from Du to Dp was due to that the fibers on the back of the
laminate were stretched, resulting in a smaller fiber failure length by the
same size openings. It is observed from Fig. 11 that the 20 and 30 mm
laminates at each testing temperature showed three-stage failure char­
acteristics, and Fig. 12b gives the schematic sketch. The first stage was
the formation of a uniform small-diameter punching hole. In the second
stage, the hole diameter increased due to the upsetting deformation of
the bullet, and a uniform shear opening formed. In the third stage, the
laminate began to further dissipate bullet energy through BFD and
delamination because the penetration capability of the bullet decreased.
The diameter of the opening increased to Du2 , and the maximum
diameter of the expansion of delamination was Dp . During the third
stage, the bullet cores underwent larger upsetting deformation and had
no sharp edge to cut the fiber quickly, it is likely that the fiber failure at
this period is due to indirect tension[36–38].
As observed from Fig. 11, the temperature variations from − 20 to
95 ◦ C did not fundamentally change the failure mechanism of the
opening holes in the UHMWPE laminates. However, the difference in the
size of the opening holes indirectly reflected the effect of the tempera­
ture on the penetration resistance. It is shown in Table 4 that the 10 mm
laminates did not undergo an evident change in the horizontal dimen­
sion D of the opening holes with the changes in the temperature, indi­
cating that there was no significant difference in the degree of bullet
upsetting deformation. Moreover, temperature treatments from − 20 to
80 ◦ C had little effect on the staged penetration depths. However, the
Fig. 10. Comparison of ballistic efficiency of the UHMWPE laminates at different temperatures.
8
M. Cao et al.
Composite Structures 277 (2021) 114638
Fig. 11. Cross-section of the impact points at different temperatures.
Fig. 12. Characteristics of opening holes of UHMWPE laminates.
high temperature reduced the anti-penetration capability of the lami­
nate. In the second stage, at − 20 ◦ C, Du1 of the laminate was the largest
and was 26.0–50.5% higher than that of the laminate treated at 10 ◦ C,
and Lp1 was the smallest among all temperatures. This showed that at
low temperatures, the bullet deformation occurred earlier and more
pronounced. In the last stage, the first large-area delamination interface
(transition interface) was observed. The main failure of the partial
laminate in front of the transition interface was shear failure, while the
BFD was the main energy consumption mechanism of the remaining
laminate behind the transition interface. During this stage, the fibers and
the matrix were squeezed outwards by the heavily deformed bullet. And
considering that the damage depth during this stage was small, the en­
ergy dissipation was limited; therefore, this process is not the focus of
this research. Due to the increase in the laminate thickness or the low
temperature treatment, the deformation resistance of the laminates
increased, the bulge deformation decreased, and the energy consump­
tion of the laminate through in-plane delamination increased. Thus, Dp
of the 30 mm laminates are greater than those of the 20 mm laminates at
10 and 80 ◦ C, and Dp of the 20 mm laminate at − 20 ◦ C is larger than that
Table 4
Dimension of opening holes of 10 mm UHMWPE laminates.
Temperature (◦ C)
Di (mm)
Du (mm)
Dp (mm)
Li (mm)
Lp (mm)
10
− 20
80
95
5.6
5.4
5.6
5.7
10.7
11.2
11.2
11.0
7.3
7.9
8.2
7.8
3.0
3.6
3.3
6.0
7.0
6.4
6.7
4.0
value of Li at 95 ◦ C was 100% greater than that at 10 ◦ C, indicating that
the UHMWPE laminate treated at 95 ◦ C was perforated more easily.
As observed from the data presented in Table 5, the temperature
treatment had little effect on Di of the laminates that thicker than 20
mm, but compared to that at 10 ◦ C, Li of the laminate at − 20 ◦ C
decreased significantly, particularly for the 30 mm laminate that
showed a 37.9% drop, while at 95 ◦ C there was a 62.1–71.4% rise. This
indicated that the hardening of the UHMWPE laminate due to the lowtemperature treatment accelerated the bullet upsetting deformation
and enhanced the anti-penetration capability of the laminate, while the
Table 5
Dimension of opening holes of 20 and 30 mm UHMWPE laminates.
Laminate
T (◦ C)
Di (mm)
Du1 (mm)
Du2 (mm)
Dp (mm)
Li (mm)
Lp1 (mm)
Lp2 (mm)
L(mm)
20 mm
10
− 20
80
95
10
− 20
80
95
5.4
6.0
5.5
5.3
5.9
6.1
5.5
5.6
10.2
12.8
11.6
11.9
11.1
16.6
10.0
9.6
16.2
17.8
23.4
29.5
23.0
18.1
14.2
23.1
63.2
127.1
70.8
221.2
200.0
50.4
151.8
127.1
3.5
3.3
3.3
6.0
2.9
1.8
3.1
4.7
8.6
2.1
5.0
2.6
4.5
4.4
5.2
4.9
1.0
0.2
1.7
0.3
0.5
0.4
0.2
2.9
13.1
5.6
10.0
8.9
7.9
6.6
8.5
12.5
30 mm
9
M. Cao et al.
Composite Structures 277 (2021) 114638
at 10 ◦ C. However, for the 30 mm laminate, Dp at − 20 ◦ C is smaller than
that at 10 ◦ C due to the severe deformation of bullet core that decreased
its penetration capability. For the laminates treated at 95 ◦ C, due to the
high temperature damage,Dp of the 20 mm laminate is greater than that
at 10 ◦ C; however, due to the increase of thickness and enhancement of
local penetration effects (Figs. 5c and 10b), Dp of the 30 mm laminate is
smaller than that at 10 ◦ C.
4. Discussion
The protection level of the 7.62 × 39 mm steel core bullet investi­
gated herein corresponds to the sub-top protection level of American
body armor standard NIJ-0101.07[39], British police bulletproof vests
standard[40] and Chinese police bulletproof vests standard[41]. And
according to standards mentioned above[32,41], the maximum value of
BFD depth of a bulletproof plate should be no greater than 25 mm. Based
on the experimental results from − 20 to 95 ◦ C, BFD depths of UHMWPE
laminates with a thickness equal to or greater than 20 mm meets all
these standards. The maximum penetration depths of the 10, 20 and 30
mm laminates at 10 ◦ C are 10.0, 13.1, and 7.9 mm, respectively. If the
absorbed kinetic energy of the bullet is distributed evenly on the pene­
trated thickness (yellow part in Fig. 11) of the laminate, the protection
efficiency of the UHMWPE laminate can be approximately represented.
And it can be seen from Fig. 13 that with the laminate thickness in­
creases, the energy absorption efficiency per unit thickness increases
approximately linearly.
Among the considered temperatures, the − 20 ◦ C treated UHMWPE
laminates showed the greatest protective performance. The protective
performance and damage degree of the laminates treated at 80 ◦ C are
close to those of the laminates treated at 10 ◦ C. Therefore, in practice,
the influence of the temperature in the range of 10–80 ◦ C can be ignored.
However, at 95 ◦ C, the protective efficiency of UHMWPE laminates nonnegligibly degraded. When the laminates were not penetrated at 95 ◦ C,
the delamination failure area of the 20 mm laminate and the penetration
depth of the 30 mm laminates were the greatest among the laminates
with the same thickness. Despite the testing groups and data in this study
are limited, it is revealed that the ballistic performance of UHMWPE
laminates will be reduced at high temperature above 80 ◦ C, which
should be a special point for attention in use and be of certain signifi­
cance to the guidance of the actual ballistic defense design.
Fig. 14 shows a comparison of the energy consumption efficiency per
unit thickness of the perforated part (yellow part in Fig. 11) of the
laminates at different temperatures. The energy consumption efficiency
of the laminate at − 20 ◦ C was always the highest among the laminates
Fig. 14. Average energy absorption efficiency of UHMWPE laminates at
different temperatures.
of the same thickness, while the lowest energy absorption efficiency did
not always occur at the highest temperature (95 ◦ C). Increases in the
temperature of laminates with thicknesses of 10 and 30 mm led to a
monotonic decrease in the energy absorption efficiency. This shows that
for the defense of a 7.62 mm caliber bullet, 10 and 30 mm UHMWPE
laminates are sufficiently thin (easily perforated) and thick (hard to
perforate), respectively, and these two laminates are weak in dispersion
with temperature. However, the laminate thickness with 20 mm is closer
to the critical perforation thickness of the target laminate, and it is
referred to as the medium thickness. The medium-thick UHMWPE
laminates are in the range of thicknesses where the ballistic performance
of the laminates is susceptible to temperature. For example, when the
temperature rises from − 20 to 95 ◦ C, the energy absorption efficiency of
the laminates first strongly decreased and then increased. The reason for
the decrease is that, compared to the laminate treated at − 20 ◦ C, there
was no low-temperature hardening effect for the laminate treated at
10 ◦ C. And the bullet deformation at 10◦ C was smaller, indirectly
leading to a stronger penetration capacity. The reason for the
enhancement is that as the temperature increased, the laminate was
more likely to delaminate and deform, resulting in stronger energy
dissipation capacity. To minimize the cost and improve mobility in the
actual protection design process, the protection thickness of the
UHMWPE laminates is usually close to the critical perforation thickness.
According to the results of this study, it is likely that the impact response
of the medium-thick UHMWPE laminate will vary significantly due to
temperature variations. The experimental results of Nguyen et al.[9]
showed that when the bullet velocity was slightly higher than the bal­
listic limit of UHMWPE laminate, the target would be perforated and the
bullet residual velocity will increase sharply, indicating that a slight
ballistic performance deviation of the laminates will give rise to severe
threats. Therefore, the penetration resistance of the medium-thick
laminates should be investigated further.
5. Conclusion
The ballistic performance of UHMWPE laminates at elevated tem­
peratures from − 20 ◦ C to 95 ◦ C against 7.62 × 39 mm bullets were
evaluated. The main conclusions are as follows:
(1) At all temperatures, the 10 mm UHMWPE laminates were
perforated, while the 20 and 30 mm laminates were not. The
maximum BFD depth and penetration depth of the 20 and 30 mm
laminates investigated from − 20 to 95 ◦ C are 18.0 and 13.1 mm,
Fig. 13. Average energy absorption efficiency of the UHMWPE laminates at
10◦ C.
10
M. Cao et al.
Composite Structures 277 (2021) 114638
respectively. The energy absorption efficiency of the laminate
increased monotonically with the increase of laminate thickness.
(2) The temperature treatment from − 20 to 95 ◦ C has no essential
effect on the failure modes of UHMWPE laminates, but the degree
of damage varies. During penetration, the 10 mm laminate
showed a failure characteristic with two stage, while the 20 and
30 mm laminates showed three-stage failure characteristics.
(3) Compared to the experimental results at 10 ◦ C, the penetration
resistance of UHMWPE laminates was enhanced by the − 20 ◦ C
low-temperature treatment while the influence of the 80 ◦ C
treatment was limited and can be ignored. Generally, under the
high temperature of 95 ◦ C, the degree of damage to the laminate
increased, and the bulletproof performance of the laminate
decreased. Studies of UHMWPE laminates should be further
conducted on the ballistic behavior at temperatures higher than
80 ◦ C.
(4) With respect to the defense against 7.62 mm steel core bullet, the
UHMWPE laminates with limited thicknesses of 10, 20 and 30
mm can be considered as thin, medium-thick, and thick, respec­
tively. The thin laminate was easily perforated while the thick
laminate was difficult to perforate. The medium-thick laminate is
closest to albeit slightly greater than the critical penetration
thickness of the bullet. The penetration depth of the mediumthick laminate is approximately more than half the thickness of
the laminate, and the BFD and delamination are large. Compared
to that of the thin and thick UHMWPE laminate, the impact
damage and anti-penetration reliability of the medium-thick
laminates fluctuated evidently with temperature, which should
be further investigated.
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
Declaration of Competing Interest
[27]
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.
[28]
[29]
Acknowledgements
[30]
The authors acknowledge the financial support from National Nat­
ural Science Foundation of China (No. 51978166) and the Fundamental
Research Funds for the Central Universities.
[31]
[32]
References
[1] van der Werff H, Heisserer U. High-performance ballistic fibers: Ultra-high
molecular weight polyethylene (UHMWPE). In: Advanced Fibrous Composite
Materials for Ballistic Protection; 2016. p. 71–107.
[2] Chen X. Advanced Fibrous Composite Materials for Ballistic Protection. Elsevier;
2016.
[3] Dingenen JLJV. Gel-spun high-performance polyethylene fibres. High-Perform
Fibres 2001:62–92.
[4] Peter W.R. Beaumont, Carl H. Zweben, Comprehensive Composite Materials II,
Elsevier; 2018.
[5] W. Shen, Q. Zhu, Q. Chen, Method for Preparing Highly Cut-resistant Ultrahigh
Molecular Weight Polyethylene (UHMWPE) Fiber and Use Thereof, United States
Patent Application 20170058431; 2017.
[6] Shim VPW, Guo YB, Tan VBC. Response of woven and laminated high-strength
fabric to oblique impact. Int J Impact Eng 2012;48:87–97.
[7] Nguyen LH, Ryan S, Cimpoeru SJ, Mouritz AP, Orifici AC. The effect of target
thickness on the ballistic performance of ultra high molecular weight polyethylene
composite. Int J Impact Eng 2015;75:174–83.
[8] Nguyen LH, Ryan S, Cimpoeru SJ, Mouritz AP, Orifici AC. The efficiency of ultraHigh molecular weight polyethylene composite against fragment impact. Exp Mech
2016;56(4):595–605.
[9] Nguyen LH, Lässig TR, Ryan S, Riedel W, Mouritz AP, Orifici AC. A methodology
for hydrocode analysis of ultra-high molecular weight polyethylene composite
under ballistic impact. Compos A Appl Sci Manuf 2016;84:224–35.
[10] Cunniff, P. Dimensionless parameters for optimization of textile based body armor
systems, in: Proc. 18th Int. Symp. of Ballistics; 1999.
[11] Bajya M, Majumdar A, Butola BS, Arora S, Bhattacharjee D. Ballistic Performance
and Failure Modes of Woven and Unidirectional Fabric based Soft Armour Panels.
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
11
Compos Struct 2021;255:112941. https://doi.org/10.1016/j.
compstruct.2020.112941.
Jones TL, Delorme RD, Burkins MS, Gooch WA. Ballistic performance of
magnesium alloy AZ31B, 23RD International Symposium on Ballistics. Spain:
Tarragona; 2007.
Showalter DD, Gooch WA, Burkins MS, Thorn V, Cimpoeru SJ. Ballistic testing of
australian bisalloy steel for armor applications. 23RD. Tarragona, Spain:
International Symposium on Ballistics; 2007.
Showalter DD, Placzankis BE, Burkins MS. Ballistic performance testing of
aluminum alloy 5059–H131 and 5059–H136 for armor applications. USA: Army
Research Laboratory; 2008.
Reddy TS, Reddy PRS, Madhu V. Response of E-glass/Epoxy and Dyneema
Composite Laminates Subjected to low and High Velocity Impact. Procedia Eng
2017;173:278–85.
Zhang TG, Satapathy SS, Vargas-Gonzalez LR, Walsh SM. Ballistic impact response
of Ultra-High-Molecular-Weight Polyethylene (UHMWPE). Compos Struct 2015;
133:191–201.
Vargas-Gonzalez LR, Gurganus JC. Hybridized composite architecture for
mitigation of non-penetrating ballistic trauma. Int J Impact Eng 2015;86:295–306.
Vargas-Gonzalez, L.R. Walsh, S.M. Gurganus, J.C. Examining the relationship
between ballistic and structural properties of lightweight thermoplastic
unidirectional composite laminates, SAMPE Proceedings Fall 2011 Conference;
2011.
Wang H, Hazell PJ, Shankar K, Morozov EV, Escobedo JP. Impact behaviour of
Dyneema® fabric-reinforced composites with different resin matrices. Polym Test
2017;61:17–26.
Tan VBC, Khoo KJL. Perforation of flexible laminates by projectiles of different
geometry. Int J Impact Eng 2005;31(7):793–810.
Rosenberg, Z. Dekel, E. Terminal Ballistics; 2012.
Irenmonger MJ. Polyethylene composites for protection against high velocity small
arms bullets. In: Proceedings of the 18th International Symposium on Ballistics;
1999. p. 946–53.
Cheeseman BA, Bogetti TA. Ballistic impact into fabric and compliant composite
laminates. Compos Struct 2003;61:161–73.
Yang Y, Chen X. Investigation of failure modes and influence on ballistic
performance of Ultra-High Molecular Weight Polyethylene (UHMWPE) unidirectional laminate for hybrid design. Compos Struct 2017;174:233–43.
Govaert LE, Peijs T. Tensile strength and work of fracture of oriented polyethylene
fibre. Polymer 1995;36:4425–31.
Kromm FX, Lorriot T, Coutand B, Harry R, Quenisset JM. Tensile and creep
properties of ultra high molecular weight PE fibres. Polym Test 2003;22:463–70.
Dangora LM, Hansen CJ, Mitchell CJ, Sherwood JA, Parker JC. Challenges
associated with shear characterization of a cross-ply thermoplastic lamina using
picture frame tests. Compos A Appl Sci Manuf 2015;78:181–90.
Zhu X, Xiong J, Shuyan Xu, Song Y, Huo P. Influence of treatment conditions on
properties of UHMWPE fibers. J Textile Res 2009;30(6):10–4 (in chinese).
Lässig T, Riedel W, Heisserer U, Werff HVD, Hiermaier S. Numerical sensitivity
studies of a UHMWPE composite for ballistic protection. Structures Under Shock &
Impact XIII 2014;141:371–81.
Sapozhnikov SB, Kudryavtsev OA, Zhikharev MV. Fragment ballistic performance
of homogenous and hybrid thermoplastic composites. Int J Impact Eng 2015;81:
8–16.
Chen Li, Cao M, Fang Q. Ballistic performance of ultra-high molecular weight
polyethylene laminate with different thickness. Int J Impact Eng 2021;156:103931.
https://doi.org/10.1016/j.ijimpeng.2021.103931.
GJB 4300A− 2012, Requirements of safety technical performance for military body
armor, National special protective clothing quality supervision and Inspection
Center, China, 2012. (in chinese).
Peijs T, Smets EAM, Govaert LE. Strain rate and temperature effects on energy
absorption of polyethylene fibres and composites. Appl Compos Mater 1994;1:
35–54.
Forster AL, Forster AM, Chin JW, Peng J-S, Lin C-C, Petit S, et al. Long Term
Stability of UHMWPE Fibers. Polym Degrad Stab 2015;114:45–51.
Dangora LM, Mitchell C, White KD, Sherwood JA, Parker JC. Characterization of
temperature-dependent tensile and flexural rigidities of a cross-ply thermoplastic
lamina with implementation into a forming model. Int J Mater Form 2018;11(1):
43–52.
Woodward RL, Egglestone GT, Baxter BJ, Challis K. Resistance to penetration and
compression of fibre-reinforced composite materials. Compos Eng 1994;4(3):
329–41.
O’Masta MR, Crayton DH, Deshpande VS, Wadley HNG. Mechanisms of
penetration in polyethylene reinforced cross-ply laminates. Int J Impact Eng 2015;
86:249–64.
Attwood JP, Russell BP, Wadley HNG, Deshpande VS. Mechanisms of the
penetration of ultra-high molecular weight polyethylene composite beams. Int J
Impact Eng 2016;93:153–65.
NIJ Standard 0101.07, Ballistic Resistance of Body Armor, National Institute of
Justice, U.S. Department of Justice, Washington, DC; 2018.
Croft J, Longhurst D. HOSDB Body Armour Standards for UK Police (2007) Part 2:
Ballistic Resistance. United Kingdom: Home Office Scientific Development Branch;
2007.
A 141− 2010, Police ballistic resistance of body armor, The Ministry of Public
Security of the People’s Republic of China, China; 2010. (in chinese).