High strain rate properties of balanced angle-ply

graphite/epoxy composites

Amol Jadhav*, Eyassu Woldesenbet, Su-Seng Pang

Department of Mechanical Engineering, Louisiana State University, 2508, CEBA Building, Baton Rouge, LA 70803, USA

Received 19 September 2002; accepted 25 November 2002

Abstract

The vast differences in strength, ultimate strain and modulus during high strain rate deformation of materials have been a very

long-standing subject of engineering interest. The present study is carried out in order to understand the effect of fiber orientations on

compressive dynamic properties of balanced angle-ply IM7/8551-7 graphite/epoxy composites using the Split Hopkinson Pressure Bar at

varying strain rates, ranging from 500 to 1500 s21. The ultimate stress–strain behavior with respect to change in strain rates for various fiber

orientations has been studied in depth. Additionally, optical microscopic images of fracture surfaces show that delamination caused by edge

effects is the prominent mechanism of failure. This research provides important data and understanding of composite material structures in

high strain rate applications.

q 2003 Elsevier Science Ltd. All rights reserved.

Keywords: A. Polymer–matrix composites; B. Impact behavior; D. Optical microscopy; Split Hopkinson Pressure Bar

1. Introduction

A large number of the applications of composite

materials involve dynamic loading during their service

life such as a projectile impact on a composite armor.

The stress wave generated during an impact can travel at

velocities considerably greater than the velocity of the

bullet and can cause damage to the body. Therefore, a

full characterization of the mechanical properties of

composite materials at various strain rates is needed.

Various techniques have subsequently been developed for

dynamic testing. The tests involving projectile impact were

found useful but cannot be used directly in determining the

material constitutive relations. Hsio et al. [1] used falling

weight impact system to achieve strain rates up to 300 s21.

The Split Hopkinson Pressure Bar (SHPB), first introduced

by Kolsky [2] is the most widely used technique for direct

determination of high strain rate mechanical properties in

the range of 200–10,000 s21. Since then, a number of

researchers have carried out variety of high strain rate

testing on various metals and non-metals using this

technique [3–12].

Most dynamic studies that were undertaken usually

involve tests in the primary directions, i.e. longitudinal and

transverse directions. Some attempts were made to study

composite properties for off-axis fiber orientation laminates.

Stab and Gilat have investigated the effects of strain rate on

tensile properties of glass/epoxy angle-ply laminates [3].

They showed that the tensile strength is higher in dynamic

tests and this effect is more pronounced when specimen

made of angle-ply laminates of smaller angles are used.

Vinson and Woldesenbet have conducted a series of tests for

the compressive mechanical properties of unidirectional

graphite/epoxy laminate composites at various off-axis

angles [4]. Their study showed that specimens having 608

off-axis fiber orientation failed in shear mode giving lower

amount of stress and strain values than expected. This was

attributed to the in-plane shear stresses coupling. Gilat et al.

[5] studied the strain rate sensitivity of IM-7/977-2 carbon/

epoxy composite under dynamic tensile loading and found

the material to be highly strain rate sensitive. In particular,

they have found that the composite is more strain rate

sensitive at shallower angles. Tensile data of angle-ply

composite laminates at high strain rates (up to 500 s21) were

obtained by Hsio et al. [1] using the expanding ring

technique. However, there are only limited data of dynamic

compressive properties of balanced angle-ply laminates. It is

1359-8368/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.

doi:10.1016/S1359-8368(03)00003-9

Composites: Part B 34 (2003) 339–346

www.elsevier.com/locate/compositesb

* Corresponding author. Tel.: þ1-225-578-5933; fax: þ1-225-578-9195.

E-mail address: amol_mol@yahoo.com (A. Jadhav).

very important to study the high strain rate effects on

balanced angle-ply laminates because they behave as

orthotropic layers with respect to in-plane forces and

strains, that is, there would be no coupling between the

normal stress (or forces) and shear strain. This is possible

when the terms A16 and A26 in an extensional stiffness

matrix, [A ], are zero, as shown in Eq. (1)

Nx

0

0

8>><>>:

9>>=>>;¼

A11 A12 0

A21 A22 0

0 0 A66

2664

3775

10x

10y

g0xy

8>>><>>>:

9>>>=>>>;

ð1Þ

where Nx represents force per unit length applied in the

x-direction and 10x ; 1

0y and g0

xy represent mid-plane strains in

the respective directions.

In the present paper, a systematic study of strain rate

effects on the response of symmetric balanced angle-ply

graphite/epoxy laminates is presented. The compressive

SHPB technique is used to develop the strain rates of

500–1500 s21. Solid cylindrical specimens with an aspect

ratio (L/D) of 1, and fiber orientations of 08 (longitudinal

direction), ^15, ^30, ^45, ^60, ^75 and 908

(transverse direction) are used for the tests. The results of

the high strain rate tests are subsequently compared to

quasi-static tests. Significance of the strain rate effects on

the values of compressive strength, ultimate strain and

modulus has been observed. Also, conclusions regarding the

damage mechanism of laminates under the conditions of

dynamic interlaminar shear are drawn.

2. Split Hopkinson Pressure Bar apparatus

and procedure

A SHPB test setup was designed and built for dynamic

type compression testing of various materials for strain rates

exceeding several hundreds per second. The principal

application of the Hopkinson Pressure Bar has been in the

study of the transient response of a material to dynamic

loading. It basically consists of a pneumatic loading device,

which includes a pressure chamber, gun barrel and release

valve. It also consists of incident and transmitted pressure

bars and a striker bar supported by Teflon bearings.

The material used for striker bar and the pressure bars is a

maraging steel having very high values of yield strength

(1830 MPa) in order to withstand a very high impact

velocity. These pressure bars are mounted on a rigid beam.

Solid cylindrical 76-ply composite specimens with aspect

ratio of one are sandwiched between the two pressure bars.

The overall specimen dimensions are required to be small to

minimize the effects of longitudinal and lateral inertia and

wave propagation within the specimen. In addition, a

frictional constraint exists at the pressure bar–specimen

interface due to the radial expansion of the specimen during

loading. The frictional effects are the highest when

the specimen is at rest and this may produce non-uniform

deformation in the specimen. By applying a thin film of

lubricant at the interfaces, these frictional constraints have

been significantly reduced [6]. Hence, in the present study

molybdenum disulphide lubricant is applied.

The schematic diagram of the SHPB apparatus is shown

in Fig. 1. The loading pulse in these experiments is initiated

by an axial impact on the free end of the input bar by the

striker bar, which is accelerated by a long gun barrel.

To control the velocity of the striker bar to a desired

velocity, the air pressure is controlled by regulators.

Strain gauges (with resistance of 350 V and gauge factor

of 2.10 at room temperature) are mounted on incident and

transmitter pressure bars at the distance of 18.5 cm from the

junction ends of both pressure bars. The gauges are

connected to a signal bridge conditioner. The strain gauge

signal is amplified and recorded by digital processing

oscilloscope. After an impact caused by the striker bar, an

elastic compressive wave of constant amplitude and finite

duration is generated in the input pressure bar. The incident

pulse wavelength can be adjusted by using striker bars of

different lengths, as the pulse in the incident bar is twice the

length of the striker bar. The amplitude of the pulse is also

directly proportional to the impact velocity of the striker bar

[7]. When the compressive loading pulse in the incident

pressure bar reaches the specimen, some part of the pulse

gets reflected from the specimen–input bar interface, while

some part is transmitted to the transmitted bar.

The magnitudes of these reflected and transmitted pulses

will decide the physical properties of the specimen.

High numbers of internal reflections are experienced in

the short specimen during the duration of the loading pulse

since the loading pulse is long compared to the wave transit

time in the specimen. The reflections cause the stress

distribution in the specimen to be uniform [8].

One dimensional wave propagation is assumed to be true

for analyzing the strain signals from the strain gauges. If the

modulus, cross section area and density of bar are denoted

by Eb, Ab and rb and those for specimen are Es, As and rs, the

equations for the strain rate ð _1Þ; strain (1) and stress (s) of

Fig. 1. The SHPB apparatus.

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346340

the specimen are given by [5]:

d1ðtÞ

dt¼

C0

Ls

½1IðtÞ2 1RðtÞ2 1TðtÞ� ð2Þ

d1ðtÞ

dt¼

22C0

Ls

1RðtÞ ð3Þ

The instantaneous strain value can be calculated by

1ðtÞ ¼22C0

Ls

ðt

01RðtÞdt ð4Þ

And the stress by

sðtÞ ¼EbAb

As

1TðtÞ ð5Þ

C0 ¼ffiffiffiffiffiffiffiEb=rb

pð6Þ

where C0 is the velocity of the bar, Ls is the length of the

specimen and 1IðtÞ; 1RðtÞ and 1TðtÞ are the strain gauge

signals of the incident, reflected, and transmitted pulses,

respectively.

Eqs. (2)–(5) are based on the assumption that dynamic

forces in both incident and transmitter bar are equal and can

be expressed as

1I þ 1R ¼ 1T ð7Þ

From Eqs. (3)–(5), it is clear that the strain can be obtained

by integrating the reflected pulse and the stress in the

specimen from the transmitted pulse.

3. Material selection and specimen preparation

The material used was an IM7/8551-7 graphite/epoxy

composite. The laminate included 76-layers of symmetric

balanced angle-ply lay-up. The prepreg lay-up was cured in

a compression molding press by a two-step curing process

under vacuum as per manufacturer’s suggested curing

process. Laminated sheets with the fiber orientation of 08,

[^158]s, [^308]s, and [^458]s and with dimensions of

25 cm £ 25 cm were produced. For static and dynamic

testing of [^308]s, [^458]s, [^608]s, [^758]s, and [908]s,

solid cylinders with 0.952 cm diameter and of the same

length were core drilled. In order to assure specimen failure,

a diameter of 0.673 cm was selected for the dynamic testing

of [08]s and [^158]s samples. The average fiber volume

fraction was found to be approximately 52% in burn-off

tests. The faces of the specimens were polished with

400-grit polish paper.

4. Results and discussion

4.1. Quasi-static tests

The purpose of quasi-static testing is to obtain longi-

tudinal, transverse and axial properties in a form of axial

stress versus axial strain curves for balanced angle-ply

graphite epoxy laminates. This is done in order to compare

the high strain rate responses to quasi-static responses.

The strain rates of about 0.001 s21 are obtained using MTS

servo-hydraulic machine. The tests are conducted

by compressing the cylindrical specimen between two

hardened steel parallel plates. Three specimens of each type

of laminate are tested to obtain consistent results.

The axial ultimate engineering stress and initial modulus

are found to be decreasing with increasing angle.

The decrease in modulus for 15 and 308 is found to be

less than 5% when compared to 08 off-axis (longitudinal)

specimens. The elastic modulus values are minimum for 908

off-axis fiber orientation (transverse direction) where the

properties are controlled by the matrix rather than the fibers.

The ultimate stress range for 45, 60 and 758 fiber orientation

specimens is found to be narrow. However, the 458

specimens show high axial strain (0.105 mm/mm) due to

the fact that there is no lateral constrains placed while

testing. The dominant failure mode observed is delamina-

tion. The presence of interlaminar shear stress caused by

edge effects is expected to be the probable cause for the

delamination to occur. The ultimate axial strength values for

various fiber orientations are plotted in Fig. 2. These values

are similar to published results in the literature [4].

4.2. High strain rate tests

4.2.1. Hopkinson Bar responses

These tests are conducted on a SHPB by varying the air

pressure in the chamber from 100 to 400 psi. The velocity of

the striker bar is shown to vary between 7 and 20 m/s as a

consequence of varying the pressure. The stress wave

produced initially undergoes distorting wave phenomenon

contrary to the basic assumption of uniaxial wave

propagation. It is seen that the pressure wave dispersion is

due to the wave velocities dependence on frequency. It is

recommended that the waves with narrower frequency

bandwidth suffer less from distorting effects of dispersion

Fig. 2. Orientation dependence of maximum stress at various strain rates.

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346 341

and this can be obtained by increasing the rise time of the

wave [6]. This shaping of impact pulse can be obtained by

placing a yielding material (impact plenum) between the

striker bar and the input bar. For our experimental work, two

different mild steel plenums of 0.381 cm thickness are

tested. It can be observed from the results in Fig. 3 that tests

conducted without plenum cause large oscillations in the

bar. This effect is minimized with a 0.953 cm diameter

plenum and can be further reduced with 0.673 cm diameter

plenum. The smaller diameter plenum is used for this study

as it reduces the undesirable oscillations.

It is well known that the strain measurements by SHPB

may not be completely reliable. In order to check the

validity of this technique to measure the strain accurately,

the strain measured directly from the specimen is compared

to the strain calculated from the stress waves obtained from

the strain gauges on the bars. A strain gauge is placed on the

specimen carefully to get accurate values of specimen

strains. It can be seen from the results shown in Fig. 4 that

the strain values obtained from the bar and the actual strain

in the specimen agree well up to the maximum strain values.

The time lag for the transmitted wave compared to the

reflected wave can be used to interpret the results of the

SHPB test. The homogenization time for all specimens is

lower than the corresponding time of failure as shown in

Table 1. The term g represents the number of times the pulse

reflected back and forth, and the value of g for material

system used in the present study is four [9]. The purpose of

these reflections is to ensure the specimen is in equilibrium

at failure and check the validity of the tests. The transient

time, ts, is obtained by measuring the time gap between the

transmitted and reflected waves. This time represents the

delay in the transmitted wave due to the time required for it

to travel through the specimen. In the absence of a

specimen, both transmitted and reflected waves should be

coincident due to the strain gauge placement at the same

distance on the pressure bars. The time to failure is obtained

from experiment. The minimum time to failure is therefore

gts, and is the total time required for the specimen to be

intact, at which time the wave reflects back and forth so that

the uniform stress assumption remains valid.

The strain rate varies during the SHPB test. Initially the

strain rate increases and reaches a relatively steady value.

The average strain rate for a test is obtained and used

to characterize the specific experiment. Based on the

assumption that the dynamic force in both the incident

and the transmitter bars are equal, following equation can be

written

1T 2 1I ¼ 1R ð8Þ

where 1T; 1I; and 1R are pressure bar strains due to

transmitted, incident and reflected pulse, respectively.

This verification of dynamic equilibrium ensures that proper

and valid tests are conducted, Fig. 5. The two curves match

with each other to a large extent.

4.2.2. Stress–strain behavior and strain rate

One of the important aspects of this study is to compare

the stress versus strain behavior of various fiber orientations

of balanced angle-ply laminates at the same strain rate.

Typical dynamic stress versus strain curves for specimens

having different fiber orientations tested at strain rates of

around 1050 s21 is shown in Fig. 6. The ultimate stress

value is seen to be decreasing uniformly as the fiber

orientation angle increases. The summary of results for

various balanced angle-ply laminate specimens is shown in

Fig. 7. From this figure, the significance of strain rate

variation on the ultimate strength properties of various fiber

orientations for balanced angle-ply laminates can be

observed clearly. For all fiber orientations, as the strain

Fig. 3. Plenum size impact on pulse shape.

Fig. 4. Comparison of strain values obtained by direct strain measurement

and by using SHPB.

Table 1

Time to failure for the off-axis specimens

Specimen off-axis

orientation (8)

Transient time

ts (ms)

Minimum time to

failure gts (ms)

Time to failure

tf (ms)

15 8 32 37

30 4 16 18

45 12 48 57

60 8 32 57

75 10 40 59

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346342

rate increases, the ultimate stress value increases. This can

be attributed to the fact that at slower strain rates, the

damage propagates more slowly utilizing most of the

applied energy. However, at higher strain rates, the damage

does not have enough time to initiate and propagate, and

thus a higher amount of energy is absorbed under this

situation. For the increase in ultimate strength of the

specimens tested in transverse direction at high strain rates,

visco-elastic nature of the polymer matrix itself is

responsible in addition to the time dependent nature of

accumulating damage [1]. The high strain rate ultimate

strength values at orientations of 308 and above are close to

each other as they are for quasi-static ultimate strength

values for similar orientations. The main reason for this

occurrence is the matrix domination in determining the

properties of the composites with increasing fiber orien-

tation. It can be inferred from Fig. 6 that the strain rate

sensitivity of the material is prominently high at relatively

low (static to 200 s21) strain rates. Fig. 2 also shows the

compressive ultimate strength at different fiber orientation

angles for high strain rates. It can be seen that the difference

in maximum strength between static and dynamic tests

decreases as orientation of fibers increases. The mode of

failure of fiber-reinforced composites is the determining

factor of the strain rate sensitivity magnitude.

This observation explains why the strain rate effect on

ultimate stress is more pronounced with decreasing fiber

orientation. There is no sudden drop in the ultimate stress

and strain values at ^608 angle laminates, which is contrary

to the previous study done by Vinson and Woldesenbet [4]

for unidirectional off-axis laminates of graphite–epoxy.

The probable cause of failure was given that the 608 plane

could be the plane of maximum dynamic shear stress due to

shear coupling. This coupling of in-plane shear stresses is

avoided in the case of balanced angle-ply laminates for the

same fiber orientation in this study. Instead, delamination

Fig. 6. Axial stress versus axial strain for several fiber orientations at strain

rates of around 1050 s21.

Fig. 7. Ultimate stress values for various fiber orientations at different strain

rates.

Fig. 5. Verification of equation of dynamic equilibrium.

Fig. 8. Ultimate strain values for various fiber orientations at different strain

rates.

Table 2

Longitudinal and transverse modulus values of unidirectional IM7/8551-7

graphite/epoxy composites at various strain rates

Strain rate

(s21)

Modulus,

E1 (GPa)

Percentage

change

Strain rate

(s21)

Modulus,

E2 (GPa)

Percentage

change

0.001 26.66 – 0.001 5.28 –

630 62.14 133.08 800 7.10 34.46

920 77.77 191.71 1140 7.61 44.12

1100 81.00 203.30 1400 8.37 58.52

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346 343

failure caused by the edge effect is a prominent mechanism

of failure in case of these laminates.

Fig. 8 shows the change in the ultimate compressive

strain as a function of strain rate for three different

orientations. It is observed that the ultimate strain values

for 0 and ^158 samples are least affected by the change in

strain rates. The ^45 and 608 are found to have undergone

maximum amount of strain. Most of the ^308 samples

showed relatively less failure strains in high strain rate

testing with a high amount of scatter in values. The highest

fracture strain is obtained under quasi-static loading

conditions. However, in the dynamic region, the strain is

very low (almost 30–40% of static values) for lower strain

rates (500 s21). It increases as the strain rate is increased.

A sharp increase in the strain values is noted for almost all

fiber orientations at strain rates ranging from 800 to

1100 s21. It has been found by a number of researchers

[7,10] that the strain measurement and therefore modulus

determination is difficult by the SHPB and the acquired data

is not very reliable. However, in general, it is observed

that the high strain rate modulus values are approximately

three-fold in longitudinal direction compared to static

values. Also, an appreciable increase in the transverse

modulus is observed at high strain rates. These values

are mentioned in Table 2. Fig. 9 shows compressive stress–

strain curves for [^158]s specimens tested at different strain

rates. As compared to the static stress–strain curve,

significant stiffening of the stress–strain curves can be

observed at higher strain rates due to visco-elastic nature of

polymer matrix. Similar trends are observed for other fiber

orientations as well as exhibiting increased initial modulus

Fig. 9. Static and dynamic stress–strain curves for [^158]s specimens.

Fig. 10. Optical Micrograph of fracture surface of (a) longitudinally loaded specimen under high strain rates, (b) [^608]s specimen loaded under dynamic

conditions, (c) [^458]s specimen loaded under dynamic conditions, (d) transversely loaded specimen under static loading.

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346344

with increasing strain rates. Also, large amount of scatter in

the modulus values is observed in the range of

1000–1500 s21, showing almost no dependence of modulus

on the strain rate except for zero and fifteen degree angles. It

was observed from the shape of the stress–strain curves that

the amount of non-linearity in the curve increases as the fiber

orientation increases from its longitudinal direction to^458.

4.3. Failure mechanisms

Specimens subjected to static compression loading in the

longitudinal direction are mainly found to undergo trans-

verse tensile failure and fiber microbuckling. This could

occur when the transverse tensile strains resulting from the

Poisson’s ratio effect exceed the ultimate transverse strain

capability of the specimen. The high strain rate failure

mechanism for longitudinal fiber orientation specimens

mainly consists of delamination including longitudinal

cracking and fiber buckling. The delamination in this case

is very extensive. Fig. 10a shows the optical microscopic

image of a longitudinal specimen that fails in high strain rate

testing. Similar kind of failure mechanism is seen in the case

of 158 balanced angle-ply laminates. Delamination is the

primary mode of failure for quasi-static as well as high

strain rate testing. The 30, 60 and 758 samples show the

mixed modes of failure in shear as well as delamination for

quasi-static rates. The 308 fiber orientation sample promi-

nently show more shear failure than the delamination.

The introduction of shear failure may be caused by the

initiation of failure due to delamination and subsequent in-

plane shear stress failure of individual laminae. The shear

plane is found to cut through the fibers for some samples.

In the cases of shear failure, two shear bands usually join

together and form a delamination site. In dynamic testing of

60 and 758 specimen, typically delaminated fractured

surfaces joined by some jumps of sheared surfaces are

observed at lower magnifications (Fig. 10b). For all 458

balanced angle-ply laminate specimens, total delamination

is observed. Fig. 10c shows the optical micrograph of a

delaminated surface. The delamination caused by inter-

laminar shear stresses is developed due to edge effects.

The shear mode of failure is totally absent in both cases of

static and dynamic loading. This confirms the decoupling of

in-plane shear in balanced angle-ply laminates.

For transverse specimens, matrix shear failure is seen to

be dominant as suggested by Collings [13]. Under static

compressive loads, shear failure occurs on 458 plane

(Fig. 10d). The shear mode changes to delamination when

the applied stress and strain rates are increased.

5. Conclusions

The graphite/epoxy symmetric balanced angle-ply lami-

nates are found to be highly strain rate sensitive in a manner

similar to unidirectional laminates of the same material.

Continuous increase in maximum axial stress and strain

has been observed with increasing strain rate for the

fiber orientations examined. However, the stress remains

constant with further increase in strain rate after achieving a

certain maximum value of ultimate stress. Contrary to the

behavior of the maximum stress value, the ultimate strain

value increases continuously with increasing strain rate.

The strain rate sensitivity of balanced angle-ply compo-

site materials is observed to be strongly dependent on

the fiber orientation. Even though fibers are strain rate

insensitive, the strain rate effect on the ultimate stress

and ultimate strain values gets more pronounced with

decreasing fiber angle. This could be explained by the

following hypotheses, that is, the mode of failure of fiber

reinforced composite materials is the determining factor of

the strain rate sensitivity magnitude. In addition, a relatively

smooth decrease in maximum stress and strain values with

increase in fiber orientation angle has been obtained. This is

contrary to the observations made for off-axis unidirectional

fiber laminates, which shows sudden decrease in stress and

strain for 608 off-axis fiber orientation due to shear failure

caused by the in-plane shear stresses. This mode of failure is

avoided due to the inherent behavior of balanced angle-ply

laminates. The modulus values generally show an appreci-

able increase in dynamic testing as compared to the static

ones. Delamination and matrix cracking are found to be the

dominant modes of failure for dynamically tested

specimens.

Acknowledgements

The authors are grateful to Dr Isaac M. Daniel at

Northwestern University, Evanston, IL, USA for helpful

discussion of results. The authors are also thankful to Nikhil

Gupta, graduate student at Louisiana Composites Lab at

LSU for help in fabrication of IM7/8551-7 graphite/epoxy

composite laminates.

References

[1] Hsio HM, Daniel IM, Cordes RD. Strain rate effects on the transverse

compressive and shear behavior of unidirectional composites.

J Compos Mater 1999;33(17):1620–42.

[2] Kolsky H. An investigation of the mechanical properties of materials

at very high rates of loading. Proc Phys Soc 1949;B-62:676–700.

[3] Stab GH, Gilat A. High strain rate characterization of angle-ply glass/

epoxy laminates. J Compos Mater 1995;29(10):278–85.

[4] Vinson JR, Woldesenbet E. Fiber orientation effects on high strain rate

properties of graphite/epoxy composites. J Compos Mater 2001;35(6):

509–21.

[5] Gilat A, Goldberg RK, Roberts GD. Experimental study of strain rate

sensitivity of carbon fiber/epoxy composite. Compos Sci Technol

2002;62:1469–76.

[6] Kaiser MA, Wicks A, Wilson L, Saunders W. Advancement in the

Split Hopkinson Bar test. Thesis submitted to Virginia Polytechnic

Institute and State University, Blacksburg, Virginia; 1998. p. 1–84.

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346 345

[7] Gama BA, Gillespie JW, Hassan M, Raines RP, Haque A, Jeelani

S, Bogetti TA, Fink BK. High strain rate behavior of plain-weave

S-2 glass/vinyl ester composites. J Compos Mater 2001;35(13):

1201–28.

[8] Lindholm US. Some experiments with the Split Hopkinson Pressure

Bar. J Mech Phys Solids 1964;12:317–35.

[9] Woldesenbet E, Vinson JR. Effect of specimen geometry in the high

strain rate testing of graphite/epoxy composites. AIAA J 1999;37(9):

1102–6.

[10] Eskandari H, Nemes JA. Dynamic testing of composite laminates with

a tensile Split Hopkinson Bar. J Compos Mater 2000;34(4):260–73.

[11] Deshpande VS, Fleck NA. High strain rate compressive behavior of

aluminium alloy foams. Int J Impact Engng 2000;24:277–98.

[12] Sharma A, Shukla A. Mechanical characterization of soft materials

using high speed photography and Split Hopkinson Pressure Bar

technique. J Mater Sci 2002;37:1005–17.

[13] Agarwal BD, Broutman LJ. Analysis and performance of fiber

composites. New York: Wiley; 1990.

A. Jadhav et al. / Composites: Part B 34 (2003) 339–346346