This article was downloaded by: [Indian Institute of Technology Roorkee]On: 30 June 2015, At: 04:23Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Click for updates

International Journal for Computational Methods inEngineering Science and MechanicsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/ucme20

Prediction of Behavior of Ceramic/Metal CompositePanels Under Two Consecutive Ballistic ImpactsA. Prakasha, J. Rajasankara, N. R. Iyera, N. Anandavallia, S. K. Biswasb & A. K.Mukhopadhyayb

a CSIR-Structural Engineering Research Centre, Chennai, Indiab CSIR-Central Glass & Ceramic Research Institute, Kolkata, IndiaAccepted author version posted online: 06 Feb 2014.Published online: 10 Apr 2014.

To cite this article: A. Prakash, J. Rajasankar, N. R. Iyer, N. Anandavalli, S. K. Biswas & A. K. Mukhopadhyay (2014)Prediction of Behavior of Ceramic/Metal Composite Panels Under Two Consecutive Ballistic Impacts, International Journal forComputational Methods in Engineering Science and Mechanics, 15:3, 192-202, DOI: 10.1080/15502287.2014.882431

To link to this article: http://dx.doi.org/10.1080/15502287.2014.882431

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

International Journal for Computational Methods in Engineering Science and Mechanics, 15:192–202, 2014Copyright c© Taylor & Francis Group, LLCISSN: 1550-2287 print / 1550-2295 onlineDOI: 10.1080/15502287.2014.882431

Prediction of Behavior of Ceramic/Metal Composite PanelsUnder Two Consecutive Ballistic Impacts

A. Prakash,1 J. Rajasankar,1 N. R. Iyer,1 N. Anandavalli,1 S. K. Biswas,2

and A. K. Mukhopadhyay2

1CSIR-Structural Engineering Research Centre, Chennai, India2CSIR-Central Glass & Ceramic Research Institute, Kolkata, India

This article presents a numerical investigation to predict thebehavior of ceramic (Al2O3 99.5)/metal (Al5083 H116) compositepanels under two consecutive high-velocity impacts of 7.62 mmsharp-nosed small projectiles. A numerical model is developed us-ing the advanced nonlinear software AUTODYN. The aim of thestudy is to predict the impact behavior of ceramic/metal compos-ite panels. The study mainly focuses on the effect of arrangementof front ceramic tiles having collinear and non-collinear joints onthe impact damage pattern. The novelty of the study presented inthis article is the prediction of high-velocity-impact response un-der two consecutive and closely spaced hits on composite panelscarried out in a more realistic manner. Numerical responses, suchas depth of penetration, and deformation in back plate and crackpatterns, are found to match well with the experimental results. Itis believed that the outcome of this study is helpful in the design ofa ceramic tile joint arrangement to minimize damage in the targetpanel.

Keywords Ceramic/metal composite, Ballistic impact, Ceramic tilejoints, 7.62 mm projectile

1. INTRODUCTIONIn recent years, advanced ceramics have been extensively

used in various innovative applications (e.g., artificial bones,complete engines, space shuttles, etc.). Advanced ceramicsexhibit excellent characteristic properties such as high melt-ing point, oxidation resistance, high hardness, non-magnetism,

The authors acknowledge the participation of CSIR-Central Glassand Ceramic Research Institute (CGCRI), Kolkata, in the developmentof ceramic-based composite panels and involving authors in the exper-imental programme at TBRL, Chandigarh (India). This paper is beingpublished with the permission of the Director, CSIR-SERC, Chennai.

Address correspondence to Amar Prakash, Senior Scientist, CSIR-Structural Engineering Research Centre, CSIR Campus, Chennai600113, India. E-mail: amar@serc.res.in or amarsercm@gmail.com

Color versions of one or more of the figures in the article can befound online at www.tandfonline.com/ucme.

chemical stability, and less weight. A ceramic-based compos-ite panel is a composite system incorporating ductile metallicplates bonded with hard ceramic tiles to defeat the ballistic pro-jectile [1–5]. On impact, the kinetic energy of the projectileis absorbed in fracturing the ceramic tile, deforming the targetand projectile, and increasing in temperature. The remainingenergy is absorbed by the metallic/composite backing, whichcontains the remnants of the projectile and the ceramic debris[6]. Ceramic/metal composite panels are extensively used inlightweight armors. One of the limitations with ceramic/metalcomposite targets under ballistic impact is that the ceramic tilegets fragmented and thus the panels become vulnerable for thenext hits. This issue has been overlooked so far in the existing lit-erature. Therefore, it is essential to understand the effect of jointpatterns in ceramic tiles to minimize the impact damage area.In this way, the multi-hit resistance capability of ceramic/metalcomposites can be enhanced significantly. Therefore, the moti-vation here is to reduce the damage area in targets under multiplehits.

Many research studies have been reported on analyti-cal, numerical, and experimental investigations on the high-velocity-impact performance of ceramic/metal composite pan-els. Willkins [1] first implemented numerical analysis of ceramicarmors subjected to normal impact using HEMP code. A fewother pioneering studies have been conducted by Hetheringtonand Rajagopalan [2], Navarro et al. [3], Benloulo and Galvez[4], and Fawaz et al. [5].

Zaera et al. [6] studied both numerically and experimen-tally the behavior of alumina/aluminum composite panels. Ithas been reported that a thicker layer of adhesive causes a largearea to be affected by plastic deformation of the metallic plate inthe composite armor consisting of alumina tiles and aluminumplate. Roeder and Sun [7] investigated the effects of structurallayering and thermal residual stresses on impact resistance ofalumina/aluminum laminated structures. Layered targets in var-ious thicknesses have been tested under incident velocities in

192

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

CERAMIC/METAL COMPOSITE PANELS AND BALLISTIC IMPACTS 193

the range of 100 m/s to 300 m/s. It has been observed thatthick-layered laminates allow less penetration than thin-layerlaminates for the same areal density. Kaufmann et al. [8] haveconducted depth of penetration tests on four different ceramics,out of which alumina ceramic outperformed silicon carbide andboron carbide.

Holmquist-Johnson [9] reported a numerical and experimen-tal study of impact performance evaluation of composite panelmade of SiC (front tiles) and aluminum alloy as the backingplate. A steel projectile of diameter 7.62 mm and mass 8.32 gimpacted on the panels. Lopez et al. [10] studied both numeri-cally and experimentally the effect of adhesive layer thicknesson the efficiency of alumina/aluminum armors using 7.62 APprojectiles. Two configurations of the ceramic/metal compos-ite panel have been studied for different tile sizes, of which0.3 mm thickness of adhesive provided a better result. Mangap-atnam [11] reported an experimental study of dynamic strengthof epoxy adhesive. Ramakrishna et al. [12] reported experimen-tal work on an uncoated SiC/SiC composite and found that forvelocity above 300 m/s, the projectile penetrated through thecomposite target. Hassan et al. [13] investigated the effect ofhigh-velocity impact of integral armour using the finite elementmethod. They have showed that the rubber composite interfacefails by delamination, believed to be due to interlaminar shearstress rather than interlaminar tensile stress.

Sadanandan et al. [14] and Jena et al. [15] have studiedthe effect of oblique impact. Sadanandan et al. [14] reportedthat the ballistic limit velocity increases with obliquity. Beppuet al. [16] reported the damage evaluation of concrete plate byhigh-velocity impact. In their tests, failure processes of crater-ing and spalling were captured by a high-speed video camera.Strabburger et al. [17] studied ballistic behavior of transpar-ent armor ceramics. It was reported that protection efficiencyof ceramic/glass/polycarbonate targets increases as the ceramicthickness increases. The modelling of high-strain-rate behaviorof materials for ceramic tiles and ductile backplate of metal arereported in Johnson-Holmquist [18] and reviewed by Lamberts[19]. Ubeyli [20] experimentally investigated the effect of dif-ferent types of adhesives on the performance of Al2O3/Al2024-laminated composite armors against 7.62 AP projectiles. Theresults showed that polyurethane exhibited more resistance tospalling of ceramic tiles than those bonded with epoxy. Karamiset al. [21] studied the ballistic behavior of composite materialssubjected to high-velocity impact.

A number of recent research studies being conducted in thefield of ceramic/metal armor have shown a vast spectrum ofresults. Fernandez et al. [22] have proposed a new constitutivematerial model for simulating the behavior of material frag-mentation under impact loading. Liu et al. [23] have shownthe method for the preparation of an interface. Ong et al. [24]have simulated advanced personnel armor using the commer-cial software AUTODYN [35]. Savio et al. [25] have studiedthe ballistic performance of boron carbide ceramic. Feli andAsgari [26], Daniel et al. [27], and Tasdemirci et al. [28] have

focused on the numerical simulation of layered ceramic/metal orceramic/fiber composites. Chi et al. [29] have presented a semi-analytical approach to studying the ballistic impact responseof the ceramic/metal composite panels. Compton et al. [30],Kolopp et al. [31], and Gamble et al. [32] recently presentedsimilar studies of hybrid layered composite targets. Previousresearch has shown that numerical simulations often neglectthe effect of the gilding jacket of the projectile; this issue wasstudied by Hazell et al. [33], who showed that for correct pre-dictions about ballistic performance, the bullet jacket should beconsidered in the model.

From the reported studies, it is observed that emphasis inprior research has been given to the optimization of the layers’thickness in the design of ceramic-based armours. Most of thestudies have been conducted to determine ballistic efficiency,effect of ceramic tile thickness, ratio of front ceramic tile andback plate thickness ratios, and effect of adhesive types andthickness on impact performance of composite targets. Thereis a scarcity of information on the effect of types of ceramictile joints on impact resistance and performance under multi-hitscenarios. The reason for this may be the high demand on com-putational resources and their non-availability. However, due toadvancements in computational tools and resources, research onnumerical simulations of physical phenomena such as consecu-tive multi-hits is possible.

The aim of the present study is to find the effect of thearrangement of front ceramic tiles having collinear and non-collinear joints on the impact damage pattern. The novelty ofthe study presented in this article is that the prediction of high-velocity-impact response under two consecutive and closelyspaced hits on composite panels is carried out in a more realisticmanner.

2. DESCRIPTION OF THE PRESENT STUDY

2.1 Criteria for Selection of MaterialThe main requirements of materials involved in any protec-

tive system or armor design are [2–5]: low density, to reducethe total weight of the armor; high bulk and shear modulus,to prevent large deformations; high yielding stress, to preservearmor resistance to failure; and high dynamic tensile stress, toavoid material rupture when shock waves appear in the materialafter impact. Metals usually fulfill all of the mentioned crite-ria, except for density. Ceramics, on the other hand, are brittle,because they get fragmented extensively when tensile wavesappear in the material. However, they fulfill other requirements,as mentioned above. It is obvious that a single material can notsatisfy all of the requirements. Therefore, ceramic tile backed bya thin metal plate is the solution to circumvent the limitations ofceramic and metal. Thus, a ceramic-metal composite combinesthe lightweight and high impact resistance of ceramic with theductility of metallic materials at the back face.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

194 A. PRAKASH ET AL.

tnioj raenilloC )b( tnioj raenilloc-noN )a(

300

mm

25 mm

300 mm

Ceramic tiles

Alum

iniu

m a

lloy

back

plat

e

Fixed support

Epoxy resin

300

mm

25 mm

300 mm

Ceramic tiles

Alum

iniu

m a

lloy

back

plat

e

Fixed support

Epoxy resin

FIG. 1. Typical target geometry.

2.2 Geometry DetailsImpact responses of ceramic/metal composite panels under

normal impact of a 7.62 mm sharp-nosed steel projectile witha caliber radius head of 3.0 are numerically predicted. Impactvelocity of the projectiles having mass of 10.3 g is consideredto be about 820 m/s (more than Mach 2). Two consecutive im-pacts are numerically generated to execute with a preset timeinterval for their activation in succession. The spatial locationsof both impacts are separated to occur on two nearby ceramictiles of composite panels. The Lagrangian-approach-based fi-nite element model is generated to simulate the high-velocityimpact on ceramic/metal composite panels using the commer-cial software AUTODYN [35]. The details of material modelsrelated to high strain rate and large deformation phenomenon asrequired for the present simulation are provided. Figure 1 showsa typical arrangement of ceramic tiles in the composite targetwith non-collinear joints and collinear joints.

2.3 Mechanism of Impact Resistance in Ceramic/MetalComposite Panels

When a projectile impacts on a ceramic/metal compositepanel, the ceramic at the point of contact gets comminuted. Thispowder-like material behaves like a fluid in the tip contact area.That is why researchers, namely Tate-Alekseevski proposed anequation to model the projectile behavior [3]. More precisely,at high impact velocity the material behaves hydrodynamicallyand is in a plastic state, and this equation is a modification ofBernoulli’s equation. This proposed equation has been success-fully used since 1966 and shows good agreement with othermethods of analysis. A comprehensive detailed description ofthese formulations can be found in the literature [1–4]. The an-alytical solution using these equations needs assumptions forsimplification. It is assumed in the existing literature, with re-gards to analytical solutions, that only the back plate undergoesdeflection; failure modes such as tearing or petaling of the plate

are often neglected; the composite panel is assumed fixed at theboundaries. Due to shock wave propagation, tensile weak zonesdeveloped within the ceramic tile, which results in a conoid, asshown in Figure 2a. The cross-section area of this conoid is morethan the projectile’s [6]. Thus, the impact force gets distributedon a larger area of the ductile backplate, as depicted in Figure 2b.The adhesive layer bonds ceramic tile with metal backplate sub-jected to interface shear, which results in delamination at theinterface.

FIG. 2. Mechanism of impact resistance in ceramic/metal composite panels.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

CERAMIC/METAL COMPOSITE PANELS AND BALLISTIC IMPACTS 195

The backplate undergoes various failure modes, such aspetaling, tearing, plugging, etc., depending upon the projec-tile energies, strength, and size. Normally, the sharp-nosed pro-jectiles are converted to equivalent cylindrical projectiles in theanalytical approach [4], whereas the numerical simulations con-sider maximum features of complex geometries, materials, andphysics of the impact process. The details of the numericalmodel developed in the present article are provided in the fol-lowing sub-sections.

3. NUMERICAL SIMULATIONA numerical model using the Lagrangian approach is devel-

oped for the simulation of high-velocity impact carried out toassess the impact resistance of a ceramic-based composite panel.The details of the target, projectile, and support conditions areprovided in the following sections.

3.1 Geometry and Finite Element DiscretizationThree-dimensional finite element meshes of the target panel

and projectile used in the finite element model are shown inFigure 3. The minimum size of the element used is 0.5 mm.The umber of eight-noded solid Lagrangian finite elements forthe projectile geometry and target bodies is about 14112 and478085, respectively. After various trials on mesh size, the finaltarget discretized with uniform refined mesh, as shown in Fig-ure 3, is used. To model the geometry of the non-collinear jointpattern of ceramic tiles, the fragment/brick feature available inAUTODYN [35] is adopted. This feature provides ease in cre-ating a geometric model with staggering joints with number oflayers. Although the projectile’s actual configuration comprisesthin casing and inner core, for the simulation a monolithic pro-jectile is used to save computational time. It is kept in mind thatthe momentum and kinetic energy of the projectile used in thesimulation must be the same as that used during the impact tests.

FIG. 3. Finite element model and mesh for target and projectile.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

196 A. PRAKASH ET AL.

3.2 Interface ModelThe front ceramic tile and ductile backplate of the target are

bonded with the epoxy resin. This bonded interface is mod-elled using the surface-to-surface contact feature available inAUTODYN.

3.3 Boundary ConditionsPart of the bottom edge of the ductile backplate in the com-

posite panel is fixed using a bench vice during an impact test.A clear margin of 75 mm is provided between the front tileedge and backplate edge of the composite panel (Figure 3). Thisboundary condition is modelled by assigning three-dimensionalgeneral velocities as zero for the selected bottom edge. Dueto this condition, any movement in the specified region getsstopped, which is similar to that of the fixed boundary in quasi-static tests.

3.4 Material ModelsIt is vital to use improved material models and their input data

when modelling any material under shock loads to obtain betterresults. Knowledge of exact model parameters over a wide rangeof strain rates is therefore a case of absolute necessity in thenumerical simulation. Three important descriptors are neededfor representing material behavior under high-velocity impact,as given below:

• An equation of state (EOS) which relates the density(or volume) and internal energy (or temperature) of thematerial to pressure;

• A constitutive relationship which describes the strengthof the material by relating the stress in the material tothe amount of distortion (strain) required to producethis stress;

• A failure model to predict the failure of material.

In addition to the above requirements, an erosion criterion isalso required as an effective numerical tool to handle severemesh distortion in both projectiles and target. However, it needscareful tuning of the correct values of geometric strains forthe material so that numerical computation is not interrupted.It is observed from the literature that different values of thegeometric erosion strains may be possible for same materialsbecause this is not a material property but a numerical techniqueto remove severely distorted elements from computation.

3.4.1 Strength and Damage ModelFor the inelastic behavior of brittle material (like ceramic)

whose strength is affected due to crushing, a suitable constitutivemodel given by Johnson-Holmquist [18] is adopted. Strengthparameters such as yield and shear modulus can be reducedwith the damage as calculation proceeds.

A Johnson-Holmquist model (JH-Model) for both strengthand damage modelling in the ceramic tiles is used. This modelconsiders both compression and shear-induced strength in ce-ramic materials. Accumulated damage is computed as the ratioof incremental plastic strain over the current estimated fracturestrain. The effective fracture strain is pressure-dependent. Thework done in deforming the material elastically in shear can beconverted into a pressure increase; hence volumetric dilatationoccurs. The amount of work which is converted into a dilatationpressure is controlled through the bulking constant. This canhave values ranging from 0.0 (representing no shear-induceddistance) to 1 (maximum dilatancy effects). If the bulking con-stant is greater than zero, then the JH model should be used inconjunction with a polynomial equation of state. The improvedtensile behavior of the model has been used to allow for prin-cipal tensile failure initiation in addition to the hydrodynamictensile limit. The crack-softening algorithm can also be used inconjunction with principal stress failure criteria.

3.4.2 Materials UsedA Johnson Cook model [20] for strength and failure is

adopted for the steel used in the projectile. Ceramic (Al2O3-99.5), epoxy resin, and aluminum alloy (Al5083 H116) are usedin the target composite panel. The material models used for thesematerials are defined in Table 1. Instantaneous geometric-strain-based erosion criteria are considered to get rid of severely dis-torted elements. The input values provided for various materialparameters are given in Table 2.

4. DETAILS OF IMPACT TESTSImpact tests were carried out on the ceramic-metal com-

posite panel. The objective of the test was to investigate theperformance of the composite panel under the normal impactof 7.62 AP projectiles. Penetration depths were measured usingconventional methods with adequate accuracy. The first hit wasconsidered at the center of the central ceramic tile in the tar-get with collinear joints as shown in Figure 4a, followed by a

TABLE 1Material models used in simulation

Descriptor Al2O3-99.5 Epoxy Resin Steel 4340 Al5083 H116

Equation of state Polynomial Shock Linear LinearStrength Johnson-Holmquist Cowper-Symonds Johnson-Cook Johnson-CookFailure Johnson-Holmquist Hydro (Pmin) Johnson-Cook Hydro (Pmin)Geometric strain 2.0 1.5 2.1 2.0

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

TAB

LE

2M

ater

iali

nput

para

met

erus

edfo

rva

riou

sm

odel

s

Mat

eria

lD

escr

ipto

r→

Equ

atio

nof

Stat

eSt

reng

thPa

ram

eter

Failu

rePa

ram

eter

AL

UM

INA

AL

2O

3-9

9.5

Poly

nom

ial

John

son-

Hol

mqu

ist

John

son-

Hol

mqu

ist

Ref

eren

ceD

ensi

ty(g

/cc)

3.8

Shea

rM

odul

us(k

Pa)

1.35

E+0

8H

ydro

Tens

ileL

imit

(kPa

)−2

.90E

+04

Bul

kM

odul

usA

1(k

Pa)

2.00

E+0

8M

odel

Type

Con

tinuo

us(J

H2)

Mod

elTy

peC

ontin

uous

(JH

2)H

ugon

iotE

last

icL

imit

(kPa

)5.

90E+0

6D

amag

eC

onst

ant,

D1

0.00

1D

amag

eC

onst

ant,

D2

1B

ulki

ngC

onst

ant

1D

amag

eTy

peG

radu

al(J

H2)

Tens

ileFa

ilure

Hyd

ro(P

min

)

EPO

XY

RE

SIN

Shoc

kC

owpe

r-Sy

mon

dsH

ydro

(Pm

in)

Ref

eren

ceD

ensi

ty(g

/cc)

1.18

6Sh

ear

Mod

ulus

(kPa

)1.

60E+0

6H

ydro

Tens

ileL

imit

(kPa

)−1

.50E

+05

Gru

neis

enC

oeffi

cien

t1.

13Y

ield

Stre

ss(k

Pa)

4.50

E+0

4Pa

ram

eter

C1

2730

Para

met

erS1

1.49

3

STE

EL

4340

Lin

ear

John

son-

Coo

kJo

hnso

n-C

ook

Ref

eren

ceD

ensi

ty(g

/cc)

7.86

E+0

0Sh

ear

Mod

ulus

(kPa

)7.

70E+0

7D

amag

eC

onst

ant,

D1

5.00

E-0

2B

ulk

Mod

ulus

(kPa

)1.

59E+0

8Y

ield

Stre

ss(k

Pa)

7.92

E+0

5D

amag

eC

onst

ant,

D2

3.44

E+0

0H

arde

ning

Con

stan

t(kP

a)5.

10E+0

5D

amag

eC

onst

ant,

D3

−2.1

2E+0

0H

arde

ning

Exp

onen

t2.

60E

-01

Dam

age

Con

stan

t,D

42.

00E

-03

Stra

inR

ate

Con

stan

t1.

40E

-02

Dam

age

Con

stan

t,D

56.

10E

-01

The

rmal

Soft

enin

gE

xpon

ent

1.03

E+0

0M

eltin

gTe

mpe

ratu

re(K

)1.

79E+0

3M

eltin

gTe

mpe

ratu

re,K

1.79

E+0

3R

ef.S

trai

nR

ate

(/s)

1

AL

UM

INU

ML

inea

rJo

hnso

n-C

ook

Hyd

ro(P

min

)A

LL

OY

Ref

eren

ceD

ensi

ty(g

/cc)

2.70

E+0

0Sh

ear

Mod

ulus

(kPa

)2.

69E+0

7H

ydro

Tens

ileL

imit

(kPa

)−1

.50E

+06

AL

5083

-H

116

Bul

kM

odul

us(k

Pa)

5.83

E+0

7Y

ield

Stre

ss(k

Pa)

1.67

E+0

5R

efer

ence

Tem

pera

ture

(K)

2.93

E+0

2H

arde

ning

Con

stan

t(kP

a)5.

96E+0

5Sp

ecifi

cH

eat(

J/kg

K)

9.10

E+0

2H

arde

ning

Exp

onen

t5.

51E

-01

The

rmal

Con

duct

ivity

(J/m

Ks)

0.00

E+0

0St

rain

Rat

eC

onst

ant

1.00

E-0

3T

herm

alSo

ften

ing

Exp

onen

t8.

59E

-01

Mel

ting

Tem

pera

ture

,K8.

93E+0

2R

ef.S

trai

nR

ate

(/s)

1

197

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

198 A. PRAKASH ET AL.

TABLE 3Comparison of depth of penetrations

DOP into back Joint type inDescription Impact velocity (m/s) Location of impact plate (mm) ceramic tiles

Numerical Prediction 820.9 Center of central tile 4.1 Collinear joints831.1 Center of corner tile 7.2 Collinear joints

Numerical Simulation (with offset in 820.9 Center of central tile 6.5 Non-collinear jointshit locations bothways) 831.1 Center of corner tile 5.1 Non-collinear joints

Experimental 820.9 Center of central tile 2.4# Non-collinear joints831.1 Center of corner tile 6.3 Non-collinear joints

#This value need to be checked because the comunited ceramic material was found embedded in the crator hole.

second hit at the lower right-side tile. For non-collinear jointedtiles, the location of hit 1 and hit 2 is shown in Figure 4b.An impact experiment was conducted on the target havingnon-collinear jointed tiles using the test set-up as shown inFigure 4c.

4.1 Procedure for Impact Test• Well-wrapped ceramic-metal composite panel was

mounted on the bench vice (Figure 4c). One of theedges of the panel was gripped between the jaws ofthe bench vice and the other edges were kept uncon-strained.

• Arrangements were made to determine the velocity ofthe projectile before impact.

• Adequate attention was paid before triggering the7.62AP projectile to ensure that no person stayed nearthe composite panel.

• First, the composite panel had an impact having pro-jectile velocity 820.9 m/sec at the center of the panelwhere two tile edges meet, as shown in Figure 4b.

• Then, on this damaged composite panel, a second hitwith an impact velocity of 831.1 m/s was made atlocation Hit 2, as shown in Figure 4b.

• Measurements were taken for the depth of penetrationwith the help of a special gauge. The criteria relatedto the DOP measurement as reported (NIJ-[34]) wasfollowed.

• Thin wrapping was removed and the composite panelalong with the debris of the fractured tile were pho-tographed as shown(Figure 6c).

5. RESULTS AND DISCUSSION

5.1 Prediction of Impact Response for Target withCollinear Jointed Tiles (Symmetric Hits)

On first impact at the location marked hit 1 (Figure 4), theplaner stress wave moves in-plane and starts reflecting from themidpoints of the edges at the same time due to equal distancefrom the point of impact. However, it reaches the corner laterin time due to the longer distance as compared to the midpointson the edges. During this time lag, stress wave transmission at

FIG. 4. Ceramic tile patterns: (a) collinear joint; (b) non-collinear joint; (c) test set-up.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

CERAMIC/METAL COMPOSITE PANELS AND BALLISTIC IMPACTS 199

FIG. 5. Damage contours for collinear joints for consecutive hits.

the midpoint of all four edges of the impacted tile takes place.This transmitted stress wave, originating at the interface, movesas a circular wave front and is met with edges normal to thedirection of propagation in the adjacent tile. Because of theearly reflection from the sides, a longitudinal crack developsfirst and a transverse crack appears later. Transverse cracks inthe adjacent tiles result due to the late reflection of the stresswave from the distal edge. Similar central tensile cracks developin all four adjacent tiles, as shown in Figure 5.

The depth of penetrations obtained from numerical and ex-perimental studies are compared in Table 3. A predicted re-sponse for depth of penetration in the case of collinear jointsis obtained as 4.1 mm and 7.2 mm for the first and secondhits, respectively. The corresponding damage contours for frontceramic tiles are shown in Figure 5.

5.2 Simulation of Impact Test on Target withNon-Collinear Jointed Tiles (Asymmetric Hits)

To simulate the experimental behavior, the eccentric impactlocation is deliberately considered; for this reason, the transmit-ted stress wave reaches with a delay in the downward ceramictile and very few cracks appear, even at the end of 84 μs (whichis considered as the end of the first hit response). The main crackin the bottom tile is mainly due to the reflection from sides onlybecause the stress wave could not reflect by the time kineticenergy in the first hit was dissipated.

The damage contours obtained numerically and cracked tilesexperimentally after two consecutive hits are shown in Figure 6.The developed cracks in ceramic tiles with collinear and non-collinear joints show different patterns.

FIG. 6. Damage contours of non-collinear joints for consecutive hits.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

200 A. PRAKASH ET AL.

FIG. 7. Depth of penetration into the back plate in the composite target (side views).

5.3 Depth of Penetration (DOP)As per numerical prediction, the projectile is found to pene-

trate into the backplate to a depth of 6.5 mm and 5.1 mm for thefirst hit and second hit, respectively. The experimental valuesof penetration depth for first and second hits of non-collinearjointed tiles were measured as 2.4 mm and 6.3 mm, respec-tively. It is noted that the comminuted ceramic material wasembedded into the aluminum back plate. Due to this, the re-ported measured depth of penetration for a central hit of 2.4 mmneeds the proper removal of foreign material for actual DOP inthe aluminum back plate. One of the possible reasons for thedifference between experimental and numerical values of DOP

may be due to the covering of the ceramic tiles by thin linenin the experiment. Although it was assumed that the thin linenwrap would not affect impact behavior, it seems to have littleinfluence on response as per the experimental result. Negligiblebulging (less than 1 mm) at the back face is observed for boththe non-collinear and collinear joint cases, as shown in Figure 7.

5.4 Kinetic Energy VariationThe kinetic energy (KE) variation during both consecutive

hits is shown in Figure 8. Based on the preliminary trial, the timeof cut-off is determined to make the second hit. It can be seen

0.0

1.0

2.0

3.0

4.0

0.00 0.04 0.08 0.12 0.16

Kin

etic

Ene

rgy,

kJ

Time, ms

Collinear joint Non-collinear joint

0.0

1.0

2.0

3.0

4.0

0.00 0.04 0.08 0.12

Kine

tic e

nerg

y, k

J

Time (ms)

First hitFirst hit Second hitSecond hit

FIG. 8. Kinetic energy of the projectile for non-collinear ceramic joints.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

CERAMIC/METAL COMPOSITE PANELS AND BALLISTIC IMPACTS 201

that the projectile’s entire kinetic energy has been dissipatedinto various mechanisms, namely deformation of target, heat,etc. Therefore, the next hit is generated after this time interval.The pattern of KE dissipation history is found to be the samefor both cases, as shown in Figure 8.

6. SUMMARY AND CONCLUSIONSSimulations of two consecutive normal impacts of 7.62 mm

sharp-nosed projectiles on ceramic/metal composite panels arepresented. The two impacts are numerically generated with apreset delay in their activation time.

• It is observed that the ceramic tile arrangement andimpact locations influence the damage caused due tohigh-velocity multiple impacts on adhesively bondedceramic/metal composite targets.

• Damage contours obtained from the simulations indi-cate the tensile failure of material at a scale from 0 to 1,and exhibit the shock wave propagation phenomenon.One can clearly identify the effect of joints from thesecontours.

• Maximum depth of penetration found for collinearjoints was 7.2 mm at the corner tile hit, whereas fornon-collinear joints it was 5.1 mm, compared with theexperimental value of 6.3 mm. Therefore, a variationin the depth of penetration obtained is in the range of14–19%.

• An eccentricity in the location of actual impact duringtests has been observed from the crack patterns ob-tained. Therefore, to simulate this behavior, a suitableoffset regarding actual impact locations in tests hasbeen considered.

• Both experimental and numerical responses exhibiteda close agreement in terms of depth of penetration aswell as crack patterns typical for a non-collinear jointpattern of tiles. Further investigations are necessary toarrive at the optimum size of the tile and effective jointpatterns for reducing the damage in the target.

• The understanding about the damage under consecu-tive impacts and the crack patterns can provide sig-nificant input for designing protective ceramic/metalcomposite panels.

REFERENCES1. M.L. Wilkins, Mechanics of Penetration and Perforation, Intl. Journal En-

gineering Science, vol. 16, pp. 793–807, 1978.2. J.G. Hetherington and B.P. Rajagopalan, An Investigation into the Energy

Absorbed During Ballistic Perforation of Composite Armors, InternationalJournal Impact Engineering, vol. 11(1), pp. 33–40, 1991.

3. R. Zaera and G.V. Sanchez, Analytical Modelling of Normal and ObliqueBallistic Impact on Ceramic/Metal Lightweight Armours, InternationalJournal of Impact Engineering, vol. 21, pp. 133–148, 1998.

4. C. Benloulo and G.V. Sanchez, A New Analytical Model to Simulate Impactonto Ceramic/Metal Composite Armours, International Journal of ImpactEngineering, vol. 21, pp. 461–471, 1998.

5. Z. Fawaz, W. Zheng, and K. Behdinan, Numerical Simulation of Normaland Oblique Ballistic Impact on Ceramic Composite Armours, CompositeStructures, vol. 63, pp. 387–395, 2004.

6. R. Zaera, S.S. Sanchez, C. Perez, and C. Navarro, Modelling of AdhesiveLayers in Mixed Ceramic/Metal Armours Subjected to Impact, Composite:Part A, vol. 31, pp. 823–833, 2000.

7. B.A. Roeder and C.T. Sun, Dynamic Penetration of Alumina/AluminumLaminates: Experiments and Modeling, International Journal of ImpactEngineering, vol. 25, pp. 169–185, 2001.

8. C. Kaufmann, D. Cronin, M. Worswick, G. Pageau, and A. Beth, Influenceof Material Properties on the Ballistic Performance of Ceramics for PersonalBody Armour, Shock and Vibration Journal, vol. 10(1), pp. 51–59, 2003.

9. T.J. Holmquist and G.R. Johnson, Characterization and Evaluation of Sili-con Carbide for High-Velocity Impact, Journal of Applied Physics, vol. 97,pp. 493–502, 2005.

10. J. Lopez-Puente, A. Arias, R. Zaera, and C. Navarro, The Effect of Thick-ness of Adhesive Layer on the Ballistic Limit of Ceramic/Metal Armours,An Experimental and Numerical Study, International Journal of ImpactEngineering, vol. 32, pp. 321–336, 2005.

11. A. Mangapatnam and V. Parameswaran, Dynamic Strength of AdhesiveSingle Lap Joints at High Temperature, International Journal of Adhesionand Adhesives, vol. 28, pp. 321–327, 2008.

12. T. Ramakrishna Bhatt, R. Sung Choi, M.L. Cosgriff, S.D. Fox, and N. KangLee, Impact Resistance of Uncoated SiC/SiC Composite, Materials Scienceand Engineering, vol. 476, pp. 20–28, 2008.

13. M. Hassan, Y. Zhu, A. Haque, A. Abutalib, U. Vaidya, S. Jeelani, B. Gama,and B. Gillespie Fink, Investigation of High-Velocity Impact on IntegralArmor Using Finite Element Method, International Journal of Impact En-gineering, vol. 24, pp. 203–217, 2000.

14. S. Sadanandan and J.G. Hitherington, Characterization of Ceramic/Steeland Ceramic/ Aluminium Armours Subjected to Oblique Impact, Interna-tional Journal of Impact Engineering, vol. 19, pp. 811–819, 1997.

15. P.K. Jena, N. Jagtap, K. Sivakumar, and B.T. Balakrishna, Some Exper-imental Studies on Angle Effect in Penetration, International Journal ofImpact Engineering, vol. 37, pp. 489–501, 2010.

16. M. Beppu, K. Miwa, M. Itoh, M. Katayama, and T. Ohno, Damage Eval-uation of Concrete Plate by High-Velocity Impact, International Journal ofImpact Engineering, vol. 35, pp. 1419–1426, 2008.

17. E. Strabburger, Ballistic Testing of Transparent Armour Ceramics, Journalof the European Ceramic Society, vol. 29, pp. 267–273, 2009.

18. T.J. Holmquist and G.R. Johnson, Modeling of Ceramic Dwell and InterfaceDefeat, Ceramic Armor Material Design, pp. 309–316, 2001.

19. A.P.T.M.J. Lamberts, Numerical Simulation of Ballistic Impacts on Ce-ramic <aterial, MT07.33, Department of Mechanical Engineering, Mate-rials Technology PDE Automotive B.V. CAE, Eindhoven Univ. of Tech,http://www.mate.tue.nl/mate/pdfs/8206.pdf.

20. M. Ubeyli, O.R. Yildirim, and O. Bilgehan, Investigation on the BallisticBehavior of Al2O3/Al-2024 Laminated Composites, Journal of MaterialProcessing Technology, vol. 196, pp. 356–364, 2008.

21. M.B. Karamis, F. Nair, and A.A. Cerit, The Metallurgical and Deforma-tion Behaviors of Laminar Metal Matrix Composite after Ballistic Impact,Journal of Material Processing Technology, vol. 209, pp. 4880–4889, 2009.

22. D.F. Fernandez, R. Zaera, and J. Saez, A Constitutive Equation for CeramicMaterials Used in Lightweight Armors, Computers and Structures, vol. 89,pp. 2316–2324, 2011.

23. G. Liu, C. Ni, Q. Xiao, F. Jin, G. Qiao, and T. Lu, Preparation and In-terface Structures of Metal-Encased SiC Composite, Armors with Inter-penetrating Structure, Rare Metal Materials and Engineering, vol. 40(12),pp. 2076–2079, 2011.

24. C.W. Ong, C.W. Boey, R.S. Hixson, and J.O. Sinibaldi, Advanced LayeredPersonnel Armor, International Journal of Impact Engineering, vol. 38(5),pp. 369–383, 2011.

25. S.G. Savio, K. Ramanjaneyulu, V. Madhu, and T. Balakrishna Bhat, AnExperimental Study on Ballistic Performance of Boron Carbide Tiles, In-ternational Journal of Impact Engineering, vol. 38(7), pp. 535–541, 2011.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5

202 A. PRAKASH ET AL.

26. S. Feli and M.R. Asgari, Finite Element Simulation of Ceramic/CompositeArmor Under Ballistic Impact, Composites Part B: Engineering, vol. 42(4),pp. 771–780, 2011.

27. B. Daniel, R.F. Alfredo, F.M.A. Sergio, C.L.M. Francisco, and V.D.Maurı́cio, Ballistic Impact Simulation of an Armour-Piercing Pro-jectile on Hybrid Ceramic/Fiber Reinforced Composite Armours, In-ternational Journal of Impact Engineering, vol. 43, pp. 63–77,2012.

28. A. Tasdemirci, G. Tunusoglu, and M. Guden, The Effect of the Interlayeron the Ballistic Performance of Ceramic/Composite Armors: Experimentaland Numerical, International Journal of Impact Engineering, vol. 44, pp.1–9, 2012.

29. R. Chi, A. Serjouei, I. Sridhar, and G.E.B. Tan, Ballistic Impact on Bi-layerAlumina/Aluminium Armor: A Semi-analytical Approach, InternationalJournal of Impact Engineering, vol. 52, pp. 37–46, 2013.

30. B.G. Compton, E.A. Gamble, and F.W. Zok, Failure Initiation During Im-pact of Metal Spheres onto Ceramic Targets, International Journal of ImpactEngineering, vol. 55, pp. 11–23, 2013.

31. A. Kolopp, R. Samuel, and B. Christophe, Experimental Study of SandwichStructures as Armour Against Medium-velocity Impacts, International Jour-nal of Impact Engineering, in press.

32. E.A. Gamble, B.G. Compton, and F.W. Zok, Impact Response of LayeredSteel–Alumina Targets, Mechanics of Materials, vol. 60, pp. 80–92, 2013.

33. P.J. Hazell, G.J.A. Thomas, D. Philbey, and W. Tolman, The Effect of Gild-ing Jacket Material on the Penetration Mechanics of a 7.62 mm Armour-piercing Projectile, International Journal of Impact Engineering, vol. 54,pp. 11–18, 2013.

34. National Institute of Justice (NIJ), Standard-0101.06, Ballistic Resistanceof Body Armor, July ‘08, http://www.ojp.usdoj.gov/nij.

35. AUTODYN, Release 12.1, ANSYS, Inc., Canonsburg, PA, USA, 2009.

Dow

nloa

ded

by [

Indi

an I

nstit

ute

of T

echn

olog

y R

oork

ee]

at 0

4:23

30

June

201

5