Ballistic impact performance of ultra-high molecular ...

Ballistic impact performance of ultra-high molecular weightpolyethylene (UHMWPE) composite armour

NAYAN PUNDHIR, HIMANSHU PATHAK* and SUNNY ZAFAR

School of Engineering, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India

e-mail: [email protected]

MS received 6 March 2020; revised 6 June 2020; accepted 23 August 2021

Abstract. Present work deals with the nonlinear finite element analyses of ultra-high molecular weight

polyethylene (UHMWPE). UHMWPE has been presented for ballistic design investigation of lightweight body

armour using ANSYS-Workbench. The ballistic performance of UHMWPE has been compared with Kevlar/

epoxy composite and alumina. The study is presented in terms of the ballistic limit of UHMWPE, Kevlar/epoxy,

and alumina plate, the implication of obliquity (at 30�, 45�, and 60�), projectile shape (elliptical, conical, and

spherical shape). The sequencing order of material layup for a bi-layer composite and ballistic performance of

single-layered UHMWPE has been compared with the multi-layered plate. The parametric studies have been

presented in the form of residual velocity, the ratio of energy transferred to impact velocity of the ballistic plate,

and perforation rate for the single and multi-layered UHMWPE. The results of the numerical analyses of

UHMWPE have been compared with the Kevlar/epoxy composite. It has been found that the armour system

made of UHMWPE laminate composite resulted in a 40.6% weight reduction compared to Kevlar/epoxy

configuration with a 17.3% higher ballistic limit.

Keywords. AUTODYN; ballistic; impact mechanics; UHMWPE; body armour; kevlar.

1. Introduction

Throughout human civilization, humans have used dis-

parate armour materials to protect themselves in the bat-

tlefield. The demand for lighter protection systems with

good ballistic performance has led to the use of composite

materials in armour due to its good protection/weight

relation. The present emphasis on greater survivability lies

in the reduction in weight and consequently an increase in

mobility.

With the expansion in human society, wooden and

metals were gradually considered for use as armour mate-

rials. In the fifteenth century, Italian and Roman sovereigns

came up with the idea of bulletproof vests. They designed

armour shield made from multiple metallic layers to deflect

the fired bullets. The jackets/armour made of metallic

(steel) layers were heavy and uncomfortable; mobility with

such material configuration was quite challenging [1–3].

Further, the material bulkiness and discomfort must be

resolved, and the need for lightweight armour was felt. The

currently available body armour materials include tough

metals, ceramics, laminated composite structures, and para-

aramid ballistic fabrics.

Aramid fibers (Kevlar�) emerged as potential armour

materials due to their high energy absorbing capacity and

lightweight [4]. Kevlar has a long chain of cross-linked

molecules, making it stiff enough to absorb impact load,

but it is effective up to a limit. The further thickness of the

material has to be increased. It escalates the discomfort [5].

Therefore, multi-layered composites were the alternative

for armour applications. In a multi-layered composite, skin

layer does not contribute much to the ballistic performance

[6–8]. It has been seen that the striking plate blunts the

projectile and absorbs a large fraction of the kinetic energy

[9, 10]. Impact of the projectile can be observed at the back

face of plate/armour. Projectile velocity, shape, weave

architecture are some of the parameters which govern the

rear face deflection [11, 12].

Recently, UHMWPE has emerged as a novel material for

ballistic protection applications. In consequence,

UHMWPE fibers are ballooning acceptance in the field of

survival technology against the impact of projectiles or

explosive blasts. UHMWPE composites have been used to

produce armour materials for personnel protection (vests

and helmets), and in military and civil armoured vehicles.

Weave structure of the UHMWPE have loosely bonded

fibers, which outweighs its energy-absorbing capacity

[13–19]. Hence, the material is best suitable for a ballistic

performance application.

Sapozhnikov et al [20] compared the ballistic perfor-

mance of multi-layered UHMWPE with the aramid fibers

and found out that, UHMWPE outweighs 10% of the*For correspondence

Sådhanå (2021) 46:194 � Indian Academy of Sciences

https://doi.org/10.1007/s12046-021-01730-0Sadhana(0123456789().,-volV)FT3](0123456789().,-volV)

ballistic limit and 25% of absorbed energy. Chen and Chu

[21] found that increasing the bonding of UHMWPE fibers

after certain point fallouts to be a slump in the energy

absorption. Liu et al [9] found that UHMWPE bolsters the

ballistic limit and energy absorption of Ti6Al4V sandwich

composite by using UHMWPE as a middle layer. Zhang

et al [15] explored the weave architecture of the UHMWPE

and found that unidirectional UHMWPE has the highest

energy-absorbing capacity.

The studied literature has explored that UHMWPE holds

the potential for a lightweight body armour application. But

there is no literature scrambling UHMWPE and Kevlar

composites as a bulk material. Therefore, present work

investigates the numerical design of the UHMWPE using

the commercial finite element method (FEM) package,

namely ANSYS-AUTODYN 16.0. In this work, different

design parameters have been investigated to measure the

ballistic limit, residual velocity and ratio of energy trans-

ferred to impact energy. The salient features of this work

are as follows:

• A computational algorithm has been proposed for

numerical design analysis of UHMWPE composite

under a ballistic loading environment.

• A comparative study has been presented for UHMWPE

composite and Kevlar/epoxy with different design

parameters.

• Residual velocity and energy transfer to the ballistic

composite plate have been analyzed with different

design parameters.

• The implication of obliquity, projectile shape, multi-

layering and order of the material layup has been

studied.

• Von-Mises stress distribution for single-layered and

multi-layered UHMWPE has been studied.

2. Problem formulation

The projectile’s kinetic energy is not only a function of the

mass of the projectile; it also depends on the type of gun

from which it is fired. Short barrel gun gives low-velocity

impact compared to long barrel guns. In the high-velocity

impact situation, there is complete penetration of the pro-

jectile. Whereas, low-velocity impact condition has partial

perforation. In fact, the projectile is either embedded in the

specimen or rebounds back depending on the impact

velocity. The projectile will not pierce the given target if

the impact velocity is lower than the ballistic limit.

The kinetic energy of the projectile, upon impact, is

converted to increase the internal energy of the specimen.

At the instant of impact, the transverse waves are gener-

ated. These waves travel to the back face of the specimen as

compressive waves and get reflected as the tensile waves.

These two opposite-nature waves collide while traveling

against each other and liberate some energy. This liberated

energy is responsible for the failure of the armour. The

intensity of the generated waves depends on the velocity of

impact [22]. Friction between projectile and plate, com-

pression and elongation of the material, delamination of

plies occur, which reduces the projectile’s initial kinetic

energy and causes the material’s failure [23]. Energy-ab-

sorbing criteria would be applied for failure analysis if the

impact velocity is below the material ballistic limit [24]. In

the presented condition, the energy transferred to the bal-

listic plate can be estimated by equation (1) [25]:

Et ¼ 1

2mp V2

i �V2r

� � ð1Þ

Then the ratio of energy transferred to the impact energy

of the projectile is calculated by equation (2) [25]:

Et

Ek¼ 0:5mp V2

i �V2r

� �0:5mp V

2i

where Ek ¼ 0:5mp V2i

� � ð2Þ

The residual velocity of perforation can be estimated by

the Recht-Ipson model (equation (3)) [10]:

Vr ¼ FffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiVci �Vc

50

� �c

qwhereF ¼ mp

�mp þmf

� �� ð3Þ

Lambert and Jonas have modified equation (3) for bal-

listic application by assuming constant energy transferred

(c = 2), for residual velocity prediction and proposed

equation (4) [15]:

Vr ¼ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiV2i �V2

50

� �qð4Þ

This model is valid Vi [ V50. Therefore, for the present

work, impact velocity is considered more significant than

the ballistic limit. The value of A is taken unity, as it has

been assumed that the projectile is non-deformable. In this

way, the projectile is chosen as of structural steel material.

The difference between the Recht-Ipson model and Lam-

bert-Jonas model was analytically found by G. Ben-Dor,

and it was reported that the accuracy of both the model is

nearly the same [26].

2.1 Constitutive equations

The constitutive equation provides the relation between

different variables using material constants. The orthotropic

equation of state requires young’s modulus in X, Y, and Z

direction. Poison’s ratio and shear modulus in XY, YZ, and

XZ planes. In the present work, the UHMWPE plate (as a

bulk polymer) and Kevlar/epoxy composite have been

modeled as an orthotropic material (E1, E2, E3,t12, t23, t31,G12, G23, G31). Alumina (99.5%) and structural steel have

been modeled with polynomial and linear equations of

state, respectively. Linear equation of state only requires

bulk modulus to satiate the criteria. A polynomial equation

194 of 15 Sådhanå (2021) 46:194

of state is presented by the Mie-Gruneisen model (equa-

tions (5) and (6)) for compressive and tensile behavior,

respectively) [27].

P ¼ A1 þA2 l2 þA3 l

3 þ Bo þBo lð Þ qo x ð5Þ

P ¼ T1 þ T2 l2 þBo qo x where l ¼ q

qo� 1

� �ð6Þ

The strength and failure model used to govern the failure

of the materials are orthotropic yield in nature, Johnson-

Holmquist, elastic and material stress/strain for the

UHMWPE, alumina (99.5%), Kevlar/epoxy composite and

structural steel, respectively. Orthotropic yield has yielded

in the XY, YZ, and XZ planes. Similarly for the elastic

model, shear modulus must be specified. The material

stress/strain model requires maximum tensile stress and

strain in the XY, YZ and XZ planes to satiate the failure

criteria [6, 28, 29].

The Johnson-Holmquist damage material model is used

to model the mechanical behavior of brittle materials under

the ballistic impact loading. The normalized equivalent

stress can be written as a power-law function. The gener-

alized equivalent stress used for alumina has been presented

by equation (7) [30].

r� ¼ r�u �D r�u � r�f�

ð7Þ

where r� ¼ rrh

r�u ¼ GP

Phþ S

Sh

� �N

1þ H ln _eð Þ and r�f

¼ BP

Ph

� �M

1þ H ln _eð Þ

2.2 Comparative weight

UHMWPE is lighter in weight as compared to Kevlar/

epoxy and alumina. The density of UHMWPE is 980 kg/

m3, whereas the densities of Kevlar/epoxy and alumina are

1650 kg/m3 and 3890 kg/m3, respectively. In the present

work, the dimension of the plates is taken as 200920096

mm3. Hence we can quantify the mobility of UHMWPE

armour in terms of the percent reduction in weight of

armour by equation (8). It can be calculated that UHMWPE

is 40.61% and 74.81 % lighter than Kevlar/epoxy and

alumina, respectively

% reduction inweight ¼ Mm �MU

Mm

� �� 100 ð8Þ

2.3 Meshing of the geometric model

For the numerical analysis, erosion of the damaged ele-

ments ensures the time step’s stability by automatically

deleting damaged elements [31]. For the present work, the

geometric strain has been used as erosion criteria. By

default, the geometric strain of 1.5 has been selected.

Default meshing facilitates to optimize the process solution

time; therefore, present work utilizes default meshing to

have the minimum process time with minimum error in

numerical results.

It can be observed from table 1, that the default mesh

with an average element size took 34.32 min of solution

with a 0.53 % difference in experimental velocity.

Whereas, when the mesh size was decreased, it caused an

increase of the solution time with not much difference in

the residual velocity. And on increasing the mesh size, the

percent difference with the residual velocity increased.

Therefore, default mesh had been used for the study, as it

shows an optimal solution in an optimal time interval. The

mesh topology has been generated with four-node tetrahe-

dral elements with 3 degrees of freedom for each node and

eight-node brick elements with 3 degrees of freedom for

each node for the projectile and striking plate.

2.4 Percent increase in the ballistic limit

The effectiveness of UHMWPE is seen by calculating the

percent increase in its ballistic limit compared to the bal-

listic limit of Kevlar/epoxy composite. The percent increase

in the ballistic limit of UHMWPE is calculated by equation

(9):

% increase in ballistic limit ¼ VU �VK

VK

� �� 100 ð9Þ

Table 1. Convergence study for residual velocity.

Average element size

(mm)

Solution time

(min)

Experimental residual velocity

(m/s)

Simulated residual velocity

(m/s)

Difference with

experimental (%)

1 174.2 939 934.1 0.52

2 64.7 939 934.65 0.46

3 (Default mesh) 34.32 939 944 0.53

4 34.96 939 901.5 3.99

5 36.8 939 897.26 4.44

Sådhanå (2021) 46:194 of 15 194

2.5 Cases studied for numerical modeling

For case 1, the individual ballistic limit for the UHMWPE,

Kevlar/epoxy, and alumina plate have been acquired and

further compared with each other to find out the lower

residual velocity by the Lambert-Jonas equation. A ballistic

plate of dimension 200920096 mm3, where 200 mm is the

length and breadth of the plate, and 6 mm is the thickness

of the plate, has been considered for numerical modeling.

For case 2, the bi-layer composite plate of UHMWPE/

alumina and Kevlar/epoxy-alumina plates are simulated.

The thickness of the bi-layer is 12 mm (6 mm of each plate

in the bi-plate case). The composite bi-plates of UHMWPE/

alumina (UHMWPE as a bulk polymer) and Kevlar/epoxy-

alumina are geometrically modeled in such a way that the

back face of one is in contact with the front face of the

other, and they are glued to each other by add frozen option

in ANSYS workbench. This glue operation will facilitate

the elemental connectivity between the material interfaces.

For a multi-layered composite, the tensile stress is gener-

ated at the interface of the composites, which tries to sep-

arate the two connected layers. Therefore, to maintain the

continuity at the interface of the layers, equation (10) must

be satisfied. Lagrange multiplier (equation 11) has been

introduced to impose equation (10) [32, 33].

X1s1 ¼ X2

s2 and T1s1 þT

2

s2 ¼ 0 ð10Þ

P ¼ZC

kt x1 � x2� �

dC ð11Þ

Where : k ¼ T1 ¼ � T2

Case 3 examines the implication of obliquity on

UHMWPE and Kevlar/epoxy plate. The projectile is

directed to strike at the center of the plate at 30�, 45�, and60�. Case 4 shows the implication of different projectile

shapes on residual velocity and energy transferred on

UHMWPE and Kevlar/epoxy plate. The three different

projectile shapes are elliptical, conical, and spherical faces,

as shown in figures 1(a–c). Figure 1d shows the meshed

model of the plate and the projectile for ballistic simulation.

Case 5 shows the implication of multi-layering on the

UHMWPE plate. A single-layered plate of UHMWPE plate

Figure 1. Types of projectiles used in the simulation work

(a) elliptical, (b) conical, (c) spherical face projectile and

(d) meshed model of the projectile and plate.

Table 2. Mechanical properties of UHMWPE used in the bal-

listic simulation [31].

Property/Parameter Value

Density 980 kg/m3

Young’s modulus (E1) 3.62 GPa



Poisson’s ratio (t12) 0.0013


Shear modulus (G12) 30.70 MPa



A1 0.03

A2 0.5

A3 0.5

Tensile Failure Stress 11 1.010009 1014 (GPa)

Tensile Failure Stress 22 753.0 MPa

Tensile Failure Stress 33 753.0 MPa

Table 3. Mechanical properties of alumina used in the ballistic

simulation [34].


Density 3890 kg/m3

Young’s modulus (E1) –

Bulk Modulus A1 23.10 GPa

Shear Modulus 15.20 GPa

Damage Constant, D1 0.01

Damage Constant, D2 0.7

194 of 15 Sådhanå (2021) 46:194

has a 6 mm thickness, and the multi-layered plate (5 layers

of UHMWPE) has a 1.2 9 5 mm thickness (total thickness

of the multi-layered plate is 6 mm). Case 6 studies armour

composed of four layers of different materials. The thick-

ness of each material layer is 5 mm (the total thickness of

the modeled armour is 20 mm).

Case 6, this section simulates four square plates of

dimensions 200920095 mm3 and further glued with each

other, taking the ’add frozen’ option in the ANSYS.

Therefore, the total thickness is 20 mm. Here two cases

have been studied. Case-A with stacking sequence of

Rubber1-Alumina-Kevlar/epoxy-UHMWPE (R/A/K/U)

and case-B with stacking sequence of Rubber1-Alumina-

UHMWPE-Kevlar/epoxy (R/A/U/K).

3. Results and discussions

In this work, a simulation algorithm for the ballistic study

has been presented using finite element software ANSYS-

AUTODYN 16.0. AUTODYN is a commercial hydrocode

that relates the stress and strain relation and other param-

eters while giving the optimal solution. The projectile is

directed to strike at the center of the front plate. The

shortest distance between the projectile and the striking

face of the plate is taken at 30 mm (the distance between

the projectile and plate is to provide evidence that the

projectile and plate were not initially in contact. Residual

velocity has been recorded when the velocity profile is

parallel to the X-axis of the graph. Therefore, the numerical

analysis results are unaffected by the distance between the

projectile and the plate).

The full geometrical model is simulated to see the best

effect of the designed parameters. In the present work, the

properties of UHMWPE are taken from the literature [31].

Here author used the UHMWPE as the bulk polymer and

performed mechanical testing to get the desired properties

of UHMWPE. Material properties of the UHMWPE, alu-

mina and Kevlar/epoxy used for the numerical analysis at

ambient temperature (228C) are listed in tables 2, 3 and 4

respectively (properties listed in tables are according to the

ANSYS-AUTODYN 16.0 co-ordinate system, where

directions 1, 2 and 3 are the orthogonal Cartesian co-ordi-

nate directions along X, Y and Z respectively. The

Table 4. Mechanical properties of Kevlar/epoxy used in the

ballistic simulation [34].


Density 1650 kg/m3

Equation of State Ortho







Bulk Modulus A1 4.15 GPa

Shear Modulus 1 GPa

Volumetric response Polynomial

Parameter A2 40 GPa

Parameter T1 4.15 GPa

Reference Temperature 300 K

Specific Heat 1420 J/kgK

Strength Elastic

Shear Modulus 1 GPa

Post Failure Option Orthotropic

Residual Shear Stiffness Fraction 0.2

Decomposition Temperature 700 K

Failed in 11, Failure Mode 11 only



Failed in 12, Failure Mode 12 & 11 only



Melt Matrix Failure Mode Bulk

Stochastic failure No

Material Cutoffs -

Maximum Expansion 0.1

Minimum Density Factor 0.00001

Minimum Density Factor (SPH) 0.2

Maximum Density Factor (SPH) 3

Minimum Soundspeed 0.000006 (m/s )

Figure 2. Simulation algorithm for residual velocity.

Sådhanå (2021) 46:194 of 15 194

projectile moves along direction-1, and direction-2 repre-

sents the vertical dimension of the plate, and direction-3 is

orthogonal to directions 1 and 2. Figure 2 shows the

complete simulation algorithm, where the algorithm starts

with CAD geometry generation and meshing of the plate

and projectile. Then from the next step, the algorithm

shows the numerical modelling of the present work, with

the variable assignment and decision making in respect of

perforation.

3.1 Validation of the numerical model

Galvez et al (2009) had proposed an experimental tech-

nique for impact analysis of alumina/aluminum armour by

a tungsten projectile. The presented computational

approach has been validated with the experimental results

of Galvez et al (2009) [35]. From table 5, it can be

observed that the proposed approach is in good agreement

with the experimental results of Galvez et al (2009) [35]having an average deviation of 2% in the presented sim-

ulation results.

3.2 The implication of material on the ballisticlimit

To reveal the ballistic characteristics of considered com-

posite materials, the ballistic limit velocity has been found

for the UHMWPE, Kevlar/epoxy, and alumina (99.5%)

individually. When impacted by an elliptical projectile, the

ballistic limit velocity for UHMWPE, Kevlar/epoxy, and

alumina plate are obtained as 461.5 m/s, 393.5 m/s, and 248

m/s, respectively.

It is evident from the analysis that UHMWPE has better

ballistic limit characteristics than Kevlar/epoxy and alu-

mina. Further, residual velocity has been calculated by the

Lambert-Jonas equation (EQUATION (6)) using the bal-

listic limit velocity. From figure 3(a), it can be seen that

the residual velocity of the UHMWPE plate is less as

compared to Kevlar/epoxy and alumina plate. Thus, the

UHMWPE plate shows good stress distribution

characteristics.

Figure 3(b) shows the ratio of energy transferred to

impact energy, which indicates that the energy absorbed by

UHMWPE is 78.8% of total energy at 520 m/s impact

Table 5. Validation of numerical results.

Thickness alumina/aluminium

(mm)

Galvez et al (2009)Present work

Experimental data (residual

velocity) (m/s)

Simulation data (residual velocity)

(m/s)

% error with experimental

data

20/15 930–960 966 3.87

25/10 960 985 2.60

25/15 939 944 0.53

Figure 3. (a) Residual velocity and (b) ratio of energy transferred to impact energy of projectile impacted on UHMWPE, Kevlar/epoxy

and Alumina plate.

194 of 15 Sådhanå (2021) 46:194

velocity and Kevlar/epoxy takes 52.3% of the impact

energy. Still, alumina plate takes only 27.8% of total energy

at the same impact velocity. Hence, UHMWPE is more

prominent in energy-absorbing than Kevlar/epoxy com-

posite and alumina due to its ductility, which facilitates

absorbing higher impact energy.

Figure 4. Geometrical combination of bi-layer composite plates for projectile impact.

Figure 5. (a) Residual velocity and (b) ratio of energy transferred to impact energy for a composite bi-layer of UHMWPE/alumina and

Kevlar/epoxy-alumina.

Sådhanå (2021) 46:194 of 15 194

As impact energy increases with the increase of impact

velocity, the energy absorption capacities of ballistic plates

diminished, due to the increased velocity of generated

tensile and compressive waves within the plates. The slope

of energy absorption capacity of UHMWPE is higher than

the Kevlar/epoxy and alumina because alumina and Kevlar/

epoxy are harder than UHMWPE can absorb more energy,

but the stress distribution is more favorable in UHMWPE

plate.

3.3 The implication of material layupon the ballistic limit

In this section, the bi-layered armour plate has been sim-

ulated to investigate the implication of material layup on

ballistic performance regarding residual velocity and

energy transferred. Four different material layup combina-

tions have been formed to accomplish the objective, as

shown in figure 4. UHMWPE and Kevlar/epoxy composite

induces ductile hole formation upon impact. In such failure

mode due to plastic deformation of the material, impact the

material absorbs energy. Therefore, in this section effect of

material on the residual velocity with alumina as backing

material has been compared with alumina as striking

material.

In figure 4, case 1(a) and 1(b) depict the impact on the

UHMWPE side and alumina side, respectively for the

UHMWPE/alumina combination. Case 2(a) and 2(b) illus-

trate the impact on Kevlar/epoxy side and alumina side,

respectively, for the Kevlar/epoxy-alumina combination.

Figure 6. (a) Schematic of Oblique impact, (b) residual velocity and (c) ratio of energy transferred to impact energy for oblique impact

on UHMWPE and Kevlar/epoxy plate.

Table 6. Variation of the ballistic limit with the impact angle.

Impact angle (h)

Ballistic limit (V50) (m/s)

UHMWPE Kevlar/epoxy

30� 403.5 381.5

45� 444 451

60� 535.5 580

194 of 15 Sådhanå (2021) 46:194

In the case of the UHMWPE/alumina bi-layer, when the

projectile hits the alumina plate side, the ballistic limit is

found to be 680 m/s, and the ballistic limit for the impact on

UHMWPE side is obtained as 815 m/s. Whereas for the

Kevlar/epoxy-alumina bi-layer, when the projectile hits the

Kevlar/epoxy layer, the ballistic limit is found to be 783.5

m/s, and it is predicted as 745.5 m/s for the alumina side.

Thereby it can be avowed that a soft material as the

striking face facilitates absorbing more energy from the

projectile. When the perforation percolates in the plate,

there is the loss of kinetic energy by the striking plate. After

reaching the backing plate, the (alumina) further loses

kinetic energy as it shows higher energy absorption

capacity. Simultaneously the ballistic limit of a bi-layered

plate is increased.

If the rigid material (alumina) is used as the striking

material, transverse waves enable to travel much faster,

which reduces the dwell time for the projectile.

Therefore, the obtained residual velocity is more for

the cases when the projectile hits the alumina layer for

both the configurations. Figure 5(a) depicts the residual

velocity plot, showing the comparatively lesser residual

velocity for striking on UHMWPE and Kevlar/epoxy

face side.

Figure 5(b) shows the ratio of energy transferred to the

impact energy for the striking on different layers of the bi-

layer. The plot shows that the rate of change of the energy

transferred to the alumina side face is lesser than the

UHMWPE side impact. When the impact velocity is

increased from 840 m/s to 880 m/s, there is approximately a

10% drop in the energy-absorbing capacity when the pro-

jectile impacts on the UHMWPE and Kevlar layers. But

there is approximately 8% drop in the energy-absorbing

capacity when the projectile impacts the alumina layer. As

the impact velocity is increased, the energy absorbing

capacity of UHMWPE and Kevlar decrease at a higher rate

than when compared to alumina.

3.4 The implication of obliquity on the ballisticlimit

In actual impact situation, the impact may not always be

perpendicular to the plate. Therefore, this section examines

the implication of impact angle on the plates. Fig-

ure 6(a) shows the schematic of the computational model

for oblique impact. In the schematic, h represents the

impact angle of the projectile.

Table 7. Effect of projectile shape on the ballistic limit.

Projectile shape

Ballistic limit(V50) (m/s)

% increase in the ballistic limit of UHMWPEUHMWPE Kevlar/epoxy

Elliptical 461.5 393.5 17.28

Conical 471.5 412 14.44

Spherical 506 386 31.09

Figure 7. (a) Residual velocity and (b) ratio of energy transferred to impact energy of the projectile upon impact on UHMWPE and

Kevlar/epoxy plate by different projectiles.

Sådhanå (2021) 46:194 of 15 194

Figure 8. Simulation evolutions of the projectile penetrating process for UHMWPE single-layered plate at (a) 30 ls, (b) 60 ls, (c) 90ls, (d) 120 ls and for multi-layered plate at (e) 30 ls, (f) 60 ls, (g) 90 ls and (h) 120 ls.

194 of 15 Sådhanå (2021) 46:194

From table 6, it can be observed that the ballistic limit of

the projectile is escalating with the increase of the impact

angle. But the ballistic limit of Kevlar is more than that of

UHMWPE beyond 45� of impact angle. It can be observed

that at 45�, the ballistic limit of Kevlar outweighs by

1.58%, and at 60� outweighs by 8.31% than UHMWPE.

Therefore, UHMWPE is effective up to 45� of impact angle

in preventing the perforation.

Figure 6(b) depicts that the residual velocity of the

projectile dwindles as the impact angle increases. It might

be because the effective distance between the projectile tip

and the back face of the plate is increased. As a result, the

dwell time of the projectile is increased. Consequently,

there is a drop in the residual velocity of the projectile.

Thereby, it can be avowed that the ballistic limit of the

material is a function of the impact angle.

Figure 6(c) shows the ratio of energy transferred to

impact energy with respect to impact velocity by changing

the impact angle. It can be observed that there is approx.

41.67% decrease in the ratio of energy transferred to impact

energy at 30� for Kevlar/epoxy when the impact velocity

increases from 760 m/s to 1000 m/s. But for UHMWPE, it

is only 37.5%. Similarly, for Kevlar/epoxy, the percent

change of ratio is approx. 43.1% at 60�, and for UHMWPE,

it is approx. 40.82%. Therefore, it can be avowed that in the

case of obliquity, Kevlar/epoxy is more prominent in

energy absorption.

3.5 The implication of projectile shapeon the ballistic limit

Projectiles fired from different guns are disparate. It can be

observed from figure 1 that the diameter of the projectiles is

13 mm or 12 mm. Such diameter is classified under the

category of Class1 armor-piercing projectiles. The maxi-

mum diameter of class1 projectile is 12.7 mm at halfway of

its length. Ryan et al [36] studied the effect of Class1

armor-piercing projectile on ultra-high hardness armour

steel in support of the U.S. Army Research Laboratory data.

Borvik et al [37] used blunt, hemispherical, and conical

nose tips to study their sensitivity on a steel plate. To

simplify the geometry and to maintain the same weight as

that of the steel core of 12.7 mm projectile, the diameter of

the projectile used in the present work is 12 mm and 13

mm, and conical, spherical, and elliptical projectiles had

been used. Table 7 shows the comparative ballistic limit of

UHMWPE and Kevlar/epoxy for different projectile

shapes.

Figure 7(a) shows that the residual velocity of the

elliptical projectile is approximately twice that of the

spherical projectile for the UHMWPE. But no significant

difference can be observed in the residual velocity of the

elliptical and conical projectile at 520 m/s. It is due to

their face tips which are near of the same shape. The

projectile with a pointed tip induces localized stress at

the point of impact. Therefore, a significant difference

can be observed for pointed projectiles with respect to

other projectiles.

On juxtaposing the residual velocity for Kevlar/epoxy

composite, there is a difference of only 40 m/s for different

projectiles at 520 m/s. It might be due to the less sensitivity

of Kevlar/epoxy for different projectile shapes. A similar

trend can be observed from figure 7(b). The graphs of

Kevlar/epoxy composite for the three projectiles are very

near to each other. But UHMWPE shows a different trend.

It can be observed that UHMWPE has a higher energy

absorbing capacity due to its ductile nature.

Figure 9. (a) Cross-section and (b) residual velocity for composite armour system.

Sådhanå (2021) 46:194 of 15 194

3.6 The implication of plate number

This section expounds on the implication of multi-lay-

ering of the composite plate on von Mises stress. Von-

Mises stress is an essential property to predict the

yielding of the ductile material. More the ductility of

material more will be its energy absorbing capacity.

Consequently, it will lead to a higher ballistic limit.

UHMWPE is a ductile material; therefore, stress values

for a single and multi-layered plate have been compared

in this section. Figures 8(a, b, c and d) and 8(e, f, g, and

h) show the simulation evolutions of the projectile

penetrating process for a single-layered plate and the

multi-layered armour plate, respectively.

Figures 8(d) and 8(h) show that the maximum stress

value for multi-layered UHMWPE outweighs single-lay-

ered plate. It states that a multi-layered plate has a higher-

yielding capacity with respect to a single plate. Moreover,

the ballistic limit for the multi-layered UHMWPE plate is

542.65 m/s, which is higher than the single-layered plate of

490.33 m/s. It might be because the intensity of the trans-

mitted wave decreased in the case of the multi-layered

palate. Which leads to lower stress generation; conse-

quently the ballistic limit for the multi-layered plate

outweighs.

Figure 10. Perforation of elliptical projectile on R/A/K/U composite layer at (a) 10 ls, (b) 20 ls, (c) 30 ls and (d) 40 ls.

194 of 15 Sådhanå (2021) 46:194

3.7 Residual velocity for composite armour system

Rationally there are multiple plates of different materials.

Hence, this section shows the computational analysis of a

complete lightweight armour system. Figure 9(a), plate 3,

and plate 4 are filled with UHMWPE and Kevlar/epoxy

material properties and vice-versa. Plate 2 has been con-

sidered alumina. The ballistic cover plate, i.e., plate 1 is of

a rubber1 material (properties of rubber1 have been taken

for AUTODYN material library). The configurations are

made to strike by an elliptical projectile, and the corre-

sponding ballistic limit is found for the configuration.

It has been observed that the ballistic limit for stacking

sequence R/A/K/U is 970 m/s and for R/A/U/K is 820 m/s.

The residual velocity plots for both configurations have

been shown in figure 9(b). The result shows that the

material sequence of R/A/K/U is much more effective than

a material combination of R/A/U/K. It is due to UHMW-

PE’s higher energy absorbing capacity, which facilitates the

armour to absorb higher energy as projectile had undergone

a large loss of energy before reaching the UHMWPE layer.

Further, UHMWPE facilitates energy absorption by ductile

hole formation.

Figure 10 shows the perforation evaluation at 10 ls, 20ls, 30 ls, and at 40 ls. An illustration of the projectile

perforation has been presented by modeling the half model.

It can be observed from figure 10 (a), that the projectile

penetrates 25% of the armor width. As the perforation

evolves to 20 ls, there is a brittle fracture demonstrated by

the alumina layer, and there is almost 50% of the perfora-

tion. But when the projectile reaches the third layer of

Kevlar/epoxy composite, the projectile is arrested in the

layer due to the ductile nature of the plate. The third layer is

supported by the UHMWPE plate, which is also a ductile

material. Thus the combined effect of the third and fourth

layer facilitates to oppose the movement of the projectile.

4. Conclusions

In the present work, a comparative numerical study has

been presented for UHMWPE composite with Kevlar/

epoxy with different design parameters. The implication of

obliquity, projectile shape, and order of the material layup

have been considered for the comparison. Analyses have

been based on residual velocity and a ratio of energy

transferred to impact energy. The following conclusions

can be drawn based on the presented work:

• The ballistic limit velocity of the UHMWPE plate is

higher among the Kevlar/epoxy composite and alu-

mina plate with lighter weight.

• The energy-absorbing capacity of the UHMWPE is

superior to the other considered materials.

• It has been found that using alumina as a backing layer

of UHMWPE or Kevlar/epoxy composite facilities to

enhance the ballistic performance of the bi-layer

composite armor.

• Obliquity amends the ballistic performance of the

material. UHMWPE has superior ballistic performance

up to 45� of impact angle than Kevlar/epoxy composite

plate.

• The ballistic limit is sensitive to the projectile nose.

However, Kevlar/epoxy composite is significantly less

sensitive to the different projectiles. It was found that

spherical face projectile shows the highest ballistic

limit for both the materials.

• It has been found that a material sequence of R/A/K/U

is much more effective than a material combination of

R/A/U/K. It is due to the higher energy absorbing

capacity of UHMWPE.

• Based on the findings of the presented work,

UHMWPE composite may be preferred over Kevlar/

epoxy composite for ballistic protection purposes.

List of symbolsV50 Ballistic limit velocity

Et Energy transferred to plate by a

projectile

Ek Impact energy of the projectile

Vi The impact velocity of the

projectile

Vr The residual velocity of the

projectile

mp Mass of the projectile

mf Mass of the fractured part

P The pressure at the impact point

A1, A2, A3, Bo, T1, T2 Material constant for Mie-

Gruneisen model

q Density

qo Zero pressure density

x Internal energy per unit mass

r�u Normalize intact strength

r�f Normalized fractured strength

_e Normalized strain rate

S=Sh Normalized strength at Hogonoit

Elastic Limit

P=Ph Normalized pressure at Hogonoit

Elastic Limit

D Scalar damage parameter

(0�D� 1)

G, B, H, N, M Material constants

Mm Mass of Kevlar/epoxy or alumina

plate

MU Mass of UHMWPE plate

VK The ballistic limit for Kevlar/

epoxy plate

VU Ballistic limit of UHMWPE plate

Sådhanå (2021) 46:194 of 15 194

X1s1 and X2

s2Xi is the deformed position at the

end of 1st surface and at the

starting of 2nd surface,

respectively

T1s1 and T2

s2Ti is the traction force at the end of

1st surface and at the starting of

2nd surface respectively

k Lagrange multiplier

C Domain of integral

References

[1] Nayak N, Banerjee A and Sivaraman P 2013 Ballistic impact

response of ceramic-faced aramid laminated composites

against 7.62 mm armor-piercing projectiles. Def. Sci. J.63(4): 369–375

[2] Palta E, Fang H and Weggel D C 2018 Finite element

analysis of the Advanced Combat Helmet under various

ballistic impacts. Int. J. Impact Eng. 112: 125–143[3] Singh B B, Sukumar G, Senthil P P, Jena P K, Reddy P R S,

Kumar K S, Madhu V and Reddy G M 2017 Future armour

materials and technologies for combat platforms. Def. Sci. J.67(4): 412–419

[4] Joselin R and Wilson W J 2014 Investigation on impact

strength properties of kevlar fabric using different shear

thickening fluid composition. Def. Sci. J. 64(3): 236–243[5] Monteiro S N, Milanesi T L, Louro L H L, Lima E P, Braga

F O, Gomes A V and Drelich J W 2016 Novel ballistic ramie

fabric composite competing with KevlarTM fabric in multi-

layered armor. Mater. Des. 96(15): 263–269[6] Goh W L, Zheng Y, Yuan J and Ng K W 2017 Effects of

hardness of steel on ceramic armour module against long rod

impact. Int. J. Impact Eng. 109: 419–426[7] Serjouei A, Gour G, Zhang X, Idapalapati G and Tan G E B

2016 On improving ballistic limit of bi-layer ceramic-metal

armor. Int. J. Impact Eng. 105: 54–67[8] Elshenawy T, Seoud M A and Abdo G M 2019 Ballistic

protection of military shelters from mortar fragmentation and

blast effects using a multilayer structure. Def. Sci. J. 69(6):538–544

[9] Liu W, Chen Z, Chen Z, Cheng X, Wang Y, Chen X, Liu J,

Li B and Wang S 2015 Influence of different back laminate

layers on ballistic performance of ceramic composite armor.

Mater. Des. 87(15): 421–427[10] Palta E, Gutowski M and Fang H 2018 A numerical study of

steel and hybrid armor plates under ballistic impacts. Int.J. Solids Struct. 136–137: 279–294

[11] Mohagheghian I, McShane G J and Stronge W J 2016 Impact

perforation of polymer-metal laminates: projectile nose

shape sensitivity. Int. J. Solids Struct. 88–89(15): 337–353[12] Ha-Minh C, Imad A, Kanit T and Boussu F 2013 Numerical

analysis of a ballistic impact on textile fabric. Int. J. Mech.Sci. 69: 32–39

[13] Mcwilliams B, Yu J, Pankow M and Yen C 2015 Ballistic

impact behavior of woven ceramic fabric reinforced metal

matrix composites. Int. J. Impact Eng. 86: 57–66

[14] Hazzard M K, Hallett S, Curtis P T, Iannucci L and Trask R

S 2016 Effect of fibre orientation on the low velocity impact

response of thin dyneema� composite laminates. Int.J. Impact Eng. 100: 35–45

[15] Zhang D, Sun Y, Chen L, Zhang S and Pan N 2014 Influence

of fabric structure and thickness on the ballistic impact

behavior of Ultrahigh molecular weight polyethylene com-

posite laminate. Mater. Des. 54: 315–322[16] O’Masta M R, Crayton D H, Deshpande V S and Wadley H

N G 2015 Mechanisms of penetration in polyethylene

reinforced cross-ply laminates. Int. J. Impact Eng. 86:

249–264

[17] Pundhir N, Goyal D, Singh P, Pathak H and Zafar S 2019

Numerical simulation of composite armor subjected to

ballistic impact. Mater. Today Proc. 18(3): 696–703[18] Pundhir N, Arora G, Pathak H and Zafar S 2020 Ballistic

Impact Response of HDPE/UHMWPE Polymer Composite.

Biswal B, Sarkar B, Mahanta P Adv. Mech. Eng. Lect. NotesMech. Eng. Springer, Singapore 245–255

[19] Bogetti T A, Walter M, Staniszewski J and Cline J 2017

Interlaminar shear characterization of ultra-high molecular

weight polyethylene (UHMWPE) composite laminates.

Compos. Part A Appl. Sci. Manuf. 98: 105–115[20] Sapozhnikov S B, Kudryavtsev O A and Zhikharev M V

2015 Fragment ballistic performance of homogenous and

hybrid thermoplastic composites. Int. J. Impact Eng. 81:

8–16

[21] Chen X and Chu Y 2016 Failure mechanisms and engineer-ing of ballistic materials, Advanced Fibrous CompositeMaterials for Ballistic Protection, Elsevier Ltd

[22] Kulkarni S G, Gao X L, Horner S E, Zheng J Q and David N

V 2013 Ballistic helmets - Their design, materials, and

performance against traumatic brain injury. Compos. Struct.101: 313–331

[23] Bandaru A K, Chavan V V, Ahmad S, Alagirusamy R and

Bhatnagar N 2016 Low velocity impact response of 2D and

3D Kevlar/polypropylene composites. Int. J. Impact Eng. 93:136–143

[24] Garcıa-Castillo S K, Sanchez-Saez S and Barbero E 2012

Nondimensional analysis of ballistic impact on thin woven

laminate plates. Int. J. Impact Eng. 39(1): 8–15[25] Sheikh A H, Bull P H and Kepler J A 2009 Behaviour of

multiple composite plates subjected to ballistic impact.

Compos. Sci. Technol. 69(6): 704–710[26] Ben-Dor G, Dubinsky A and Alperin T 2002 On the

Lambert-Jonas approximation for ballistic impact. Mech.Res. Commun. 29(2–3): 137–139

[27] Feli S and Asgari M R 2011 Finite element simulation of

ceramic/composite armor under ballistic impact. Compos.Part B Eng. 42(4): 771–780

[28] Krishnan K, Sockalingam S, Bansal S and Rajan S D 2010

Numerical simulation of ceramic composite armor subjected

to ballistic impact. Compos. Part B Eng. 41(8): 583–593[29] Kumar S, Gupta D S, Singh I and Sharma A 2010 Behavior

of kevlar/epoxy composite plates under ballistic impact. J.Reinf. Plast. Compos. 29(13): 2048–2064

[30] GA G 2002 Implementation of the Johnson-Holmquist II

(JH-2) constitutive model into DYNA3D. Army ResearchLaboratory (ARL)

[31] Lassig T, Nguyen L, May M, Riedel W, Heisserer U, Werff

H V D and Hiermaier S 2015 A nonlinear orthotropic

194 of 15 Sådhanå (2021) 46:194

hydrocode model for ultra-high molecular weight polyethy-

lene in impact simulations. Int. J. Impact Eng. 75: 110–122[32] Simo J C, Wriggers P and Taylor R L 1985 A perturbed

Lagrangian formulation for the finite element solution of

contact problems. Comput. Methods Appl. Mech. Eng. 50(2):163–180

[33] Zienkiewicz O, Taylor R and Fox D D 2014 Treatment ofConstraints: Contact and Tied Interfaces, The Finite ElementMethod for Solid and Structural Mechanics, USA: Butter-worth-Heinemann, Elsevier

[34] Ansys-Auotdyn 16.0, Ansys Inc. 2015

[35] Galvez V S and Paradela L S 2009 Analysis of failure of

add-on armour for vehicle protection against ballistic impact.

Eng. Fail. Anal. 16(6): 1837–1845[36] Ryan S, Li H, Edgerton M, Gallardy D and Cimpoeru S 2016

Ballistic evaluation of an Australian ultra-high hardness

steel. In: Proc. - 29th Int. Symp. Ballast 2: 1773–1778[37] Børvik T, Length M, Hopperstad O S H and Malo K A 2002

Perforation of 12 mm thick steel plates by 20 mm diameter

projectiles with flat, hemispherical and conical noses: Part I:

Experimental study. Int. J. Impact Eng. 27(1): 19–35

Sådhanå (2021) 46:194 of 15 194

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