STRENGTH CHARACTERIZATION OF GLASSCARON HYBRID REINFORCEMENTS - AN EXPERIMENTAL INVESTIGATION

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International Journal of Civil Engineering and Technology (IJCIET)
Volume 8, Issue 2, February 2017, pp. 338–346 Article ID: IJCIET_08_02_036
Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2
ISSN Print: 0976-6308 and ISSN Online: 0976-6316
© IAEME Publication Scopus Indexed
STRENGTH CHARACTERIZATION OF GLASS-
CARON HYBRID REINFORCEMENTS - AN
EXPERIMENTAL INVESTIGATION
S. Dhipanaravind
Ph.D Research scholar, Department of Structural Engineering,
Annamalai University, Tamil Nadu, India
R. Sivagamasundari
Assistant Professor, Department of Structural Engineering,
Annamalai University, Tamil Nadu, India
ABSTRACT
This study aims to characterize and quantify the mechanical properties of hybrid
reinforcements which have been introduced in the research field of polymer composites as a
facelift. Hybrid reinforcement is the fusion of more than one type of material into one element.
A combination of glass and carbon in the ratio of 60:40 is used as Hybrid reinforcement in this
study. The carbon fiber is used as the inner core surrounded with glass fiber using epoxy
thermo set resin. This present work is mainly centered on the tensile and transverse shear
strength of glass-carbon Hybrid reinforcements. Hybridisation offers a profitable mode for
manufacturing a product with reduced cost, high specific modulus, strength, corrosion
resistance and in many cases excellent thermal stability. Based on the-way of fabrication,
different types of hybrid composites can be prepared. The current study presents the
experiments that has been carried out on 8 mm diameter hybrid rods using ASTM (American
Society for testing and Methods) standards. The results were compared with 10 mm Glass
Fibre Reinforced Polymer (GFRP) reinforcements and 10 mm Conventional (steel)
reinforcements. From the experimental observation, it has been found out that hybrid
reinforcement exhibits a tensile strength 1.5 to 2.0 times higher than GFRP and Conventional
reinforcements. Similarly, hybrid reinforcement performs slightly greater Transverse shear
strength than GFRP and Conventional reinforcements respectively.
Key words: ASTM methods, Hybridisation, GFRP and Steel reinforcements, Tensile
Properties, Transverse shear, strength property.
Cite this Article: S. Dhipanaravind and R. Sivagamasundari, Strength Characterization of
Glass-Caron Hybrid Reinforcements - An Experimental Investigation. International Journal of
Civil Engineering and Technology, 8(2), 2017, pp. 338–346.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=2

S. Dhipanaravind and R. Sivagamasundari
1. INTRODUCTION
More than two decades, the polymeric based composites materials play a vital role in many application
such as automotive, sporting goods, marine, electrical, industrial, construction, household appliances,
etc. The high strength and stiffness, light weight, and high corrosion resistance characteristics of
polymeric composites were ascertained by so many researchers [1-16]. The formation of hybrid
reinforcements is achieved by the continuous fiber rovings glass and carbon fiber reinforced polymer
matrix composites. Hybrid reinforcements used in this study were manufactured by Meena Fiberglass
Industries Puducherry, India. The fibres are reinforced with epoxy resins and are manufactured by
pultrusion process.
Antonio Nanni (1994) [4] presented an initial evaluation of hybrid rods for prestressed and non-
prestressed concrete member which consist of an FRP (Fibre-Reinforced-Plastic) skin with a steel
core. Tensile tests have shown that changing the FRP skin material, FRP skin thickness, steel core
diameter, and steel core yield strength resulted in various stress-strain behaviours. The tensile stress-
strain curves of the hybrid rods displayed a bilinear nature. It was demonstrated that the law of
mixtures can be used to predict the stress-strain behaviour of the hybrid rods.
Saito et al. (2002) [5] investigated the properties of Braided pultruded rods under crush test and
showed that these reinforcements had a better performance in comparison to the unidirectional rods in
terms of energy absorption capabilities and concluded when subjected to compressive loads the
braided layer protects the unidirectional core fibers against axial splitting and consequently makes the
structure absorb more energy before failure.
Satish (2010) [6] studied the effect of hybrid composite specimen subjected to in-plane tensile and
compressive loading and found that the hybrid laminated specimen with higher percentage of steel
sustains greater loads irrespective of fiber orientation. From the literature study it has been concluded
that the hybridization of two different materials improves the strength and stiffness and many more
qualities of the composite reinforcements which are practically needed for many industrial
applications.
Chensong Dong and Ian J Davies (2012) [7] studied the flexural behaviour of Hybrid- three types
of combinations of the carbon and glass fibers, and evaluated the flexural modulus, flexural strength
and strain up to failure under three point bend configuration in accordance with ASTM. .Devendra et
al., (2013) [8] made an investigation on the mechanical properties of E-glass fiber reinforced epoxy
composites filled by various filler materials. The test results showed that composites filled by 10%
volume Mg (OH)2 exhibited maximum ultimate tensile strength and hardness. Fly ash filled
composites exhibited maximum impact strength.
Sakthivel et al., (2014) [9] studied the performance of banana-glass-hybrid composite epoxy
reinforcement under tensile, flexural and impact loadings by increasing volume fraction and by giving
the chemical treatment on the rods according to ASTM standard. In this regard, two important
mechanical behaviours of glass–carbon hybrid reinforced epoxy composites were studied using ASTM
Standards. The first property is tensile strength which is an important characterization of
reinforcements when used as internal reinforcements of concrete members. The second property is
transverse shear strength which provides the strength of the reinforcements while transversely loaded
when used as stirrups or as shear reinforcements.
2. MATERIAL AND FABRICATION
2.1. Material Selection
The glass fibers and carbon fibers are selected as reinforcements and epoxy as matrix material. The
epoxy resin, hardener Tri Ethylene Tetra Amine (TETA) and Catalyst (Methyl ethyl Kethone
Peroxide) are used to form the hybrid rod. The glass fiber of bi-directional woven mat with 200 gsm

Strength Characterization of Glass-Caron Hybrid Reinforcements - An Experimental Investigation
and the density of 2.5 gm/cc are used. The carbon fiber of bi-directional woven mat with 200 gsm and
the density of 1.78 gm/cc are used. The glass fiber and carbon fiber used in the fabrication of hybrid
fiber reinforced composites are shown in Fig.1.
Figure 1 Glass-Carbon rovings
2.2. Fabrication of Hybrid Reinforcements
The Hybrid reinforcements used in the present study were prepared by pultrusion process. Pultrusion
is the pulling of material, such as fiber and resin, through a shaped die. Pultrusion process starts with
racks or creels holding spools of bundled continuous fiber (roving). Most often the reinforcement is
fiberglass, but it can be carbon, aramid, or a mixture. This raw fiber is pulled off the racks and guided
through a resin bath or resin impregnation system. The raw resin is almost always a thermosetting
resin. The fiber reinforcement becomes fully impregnated (wetted-out) with the resin such that all the
fiber filaments are thoroughly saturated with the resin mixture. As the resin rich fiber exits the resin
impregnation system, the un-cured composite material is guided through a series of tooling. This
custom tooling helps arrange and organize the fiber into the correct shape, while excess resin is
squeezed out. Once the resin impregnated fiber is organized and removed of excess resin, the
composite will pass through a heated steel die at a temperature 1450
-1500
C. The profile that exits the
die is now a cured as pultruded Fiber Reinforced Plastic (FRP) composite reinforcements.
Using this manufacturing process the hybrid reinforcements were removed from the mould and to
carry out the desired tests according to ASTM standards, they were cut into suitable dimensions [2, 3].
The test specimens were cut by using a cutting saw in the laboratory. Three identical test specimens
were prepared for each test. The pultrusion process is shown in Fig.2 and the fabricated hybrid
reinforcements are shown in Fig.3.
Figure 2 Pultrusion process

Figure 3 Glass-carbon Hybrid reinforcements
3. EXPERIMENTAL DETAILS
The experimental details regarding the strength characterization of Hybrid reinforcements are
explained as follows.
3.1. Tensile Strength of Hybrid Reinforcements
Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of
isotropic materials. According to ASTM D7205 [3] the tensile test was carried out for the Hybrid
reinforcements. The reinforcement was fixed between two manually adjustable grips of a 100 kN
Universal Testing Machine (UTM) with an electronic extensometer at a surrounding temperature of 35
°C. A total length of 60 cm reinforcements was cut and the area of the reinforcements was calculated
as 50.24 mm2
. The gauge length was properly marked with the help of punch and hammer on the
specimen leaving 10 cm on both ends. The distance between the marks was measured. The specimen
was properly fixed in the UTM grips. The load dial gauge was adjusted to read zero before the load
application.
The tensile load was gradually applied on the reinforcements at a rate of approximately 250
MPa/min and corresponding elongation was measured. When the needle of the loading dial gauge
flickered, that corresponding load was noted as yield load. The load was increased gradually till the
failure occurs. The ultimate load and the breaking load were noted from the dial. Finally the specimen
was removed from the UTM and the cracked portion of the specimen was observed. The experiment
was repeated for three identical 8 mm diameter Hybrid reinforcements designated as H1, H2, H3, Steel
Fe 415 reinforcements designated as S and Sand coated Glass Fibre reinforced Polymer (GFRP)
designated as G. The stress-strain curve of Hybrid reinforcements is obtained using the computerized
extensometer. The experimental setup and the failure of the Hybrid reinforcements is shown in Fig.4
and Table.1 shows the results of the reinforcements after subjected to tension.
Figure 4 Tensile Test setup and rupture of Hybrid reinforcements

Table 1 Tensile Test Results
Specime
ns
Yield load
(Tonnes)
Yield stress
(N/mm2
)
Ultimate load
(Tonnes)
Ultimate stress
(N/mm2
)
Breaking
Load
(Tonnes)
Breaking
stress
(N/mm2
)
H1 4.1 815.76 5.0 994.83 4.6 915.24
H2 4.0 795.86 4.6 915.24 4.4 875.45
H3 3.9 775.97 4.6 915.24 4.2 835.65
S 3.3 420.16 4.75 604.78 3.85 490.19
G 3.95 502.92 4.35 553.85 4.1 552.02
It is assumed that the tensile strain distribution is constant throughout any hybrid reinforcement’s
cross-section during the entire test. This assumption is justified by the observation that no slip
occurred between the skin and core. The stress-strain curve clearly shows that up to the yield point, the
rigidity of the hybrid reinforcements is primarily dependent on the core material. The stress-strain
diagram of Hybrid reinforcements is shown in Fig.5.
Figure 5 Stress-Strain curves of Hybrid reinforcements
Table 2 Tensile properties of reinforcements
Specimens Ultimate tensile stress (MPa) Ultimate tensile modulus (GPa)
H1 994.83 19.26
H2 915.24 20.56
H3 915.24 20.84
S 604.78 205
G 553.85 4.85
From the experimental observation, it has been noted that the ultimate tensile strength of hybrid
reinforcements is 1.5 to 2 times higher than steel reinforcements and GFRP reinforcements whereas
the tensile modulus is found to be 10 times lesser than that of steel and 5 times greater than GFRP
reinforcements.
3.2. Transverse Shear Strength
ASTM D7617 describes the method for sampling, conditioning, fixturing and testing composite
reinforcing bars and smooth round reinforcements in transverse shear [2]. According to ASTM D 7617
the size of the reinforcements were cut and the transverse shear test has been carried out on hybrid,
GFRP and steel reinforcements and compared [2]. The transverse shear test fixture is shown in Fig. 6.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40 50
STRESS
STRAIN

The assembled fixture is inserted into a universal compression machine, compressing the upper blade
with the machine in displacement control. The displacement rate was selected as 1.84mm/min so that
the test article fails at a time between 1 and 3 minutes. Two shear planes are formed during the test so
that the bar fails in double shear, along with a section of 8 mm diameter smooth reinforcement that has
been sheared in the fixture itself. The peak load at which the specimen fails was noted and the
transverse shear stress, was calculated as the one-half of the peak failure load (to account for double
shear) divided by the cross-sectional area of the specimen. The experimental test set up is shown in
Fig.6 and the experimental observations are shown in Table.3.
Figure 6 Transverse shear Test setup and Shear failure of Hybrid reinforcements
According to the Specification of the standards, for each series of test five samples have been
tested and the average (Ẍ), Standard deviation (Ω) and coefficient of variation (COV) were calculated
using the following expressions 1 to 3.
Ẍ =
∑
(1)
(∑ ̈ )/( )
(2)
= ̈
100 (3)
Where Ẍ=Mean of the samples; S n-1=Standard deviation of the sample; n=Number of samples and
xi=Experimental value of each sample.
Table 3 Transverse shear strength of Hybrid rods
Specimens Area Ultimate Load (kN) Shear strength (MPa) COV%
H 50.26 34.959 695.58 1.8
G 78.5 51 649.68 1.96
S 78.5 47.5 604.78 1.28
From the test results it has been observed that the shear strength of hybrid rods is slightly higher
than GFRP rods and steel rods.

Figure 7 Shear stress versus shear strain of Hybrid reinforcement
The transverse shear stress versus strain of Hybrid rebar is shown in fig.7 and from the figure, it
has been noted that the loading is recorded with a precision to three significant digits. The load slightly
drops and the stiffness of the specimen changes at the onset of failure due to the delay in the formation
of the second failure face. The loading has been continued until the load has been dropped to 70-75%
of the observed peak load.
4. RESULTS AND DISCUSSIONS
From the results of tensile test, the stress-strain diagram shows a bilinear curve i.e. starting point to
yield point then secondly yield point to ultimate point. The Hybrid FRP reinforcement stress–strain
curves were linearly elastic, with a definite yield point followed by plastic deformation. The tensile
properties show a perfectly elastic behaviour until tensile failure occurred. Hybrid reinforcements had
brittle failures when compared to Steel reinforcements. Visual observations indicated that the tensile
failures of the Hybrid rebar specimens were accompanied by delamination of the fibers, even if the
failure was always brittle. The rupture of the Hybrid reinforcements takes place firstly in the outer
glass skin and slowly it reaches the carbon core, so the load carrying capacity is more in the Hybrid
reinforcements.
An increasing performance was viewed in the tensile behaviour of Hybrid reinforcements when
compared to the pure GFRP reinforcements. It was clearly depicted that the carbon core contributes a
higher tensile modulus and hence the reinforcements could withstand a higher applied load. Thus the
conducted tensile test conveys that the combination of glass and carbon in the ratio 60:40 holds good
and provides a higher tensile strength, tensile stiffness as well as the tensile modulus of hybrid
reinforcements but a lower tensile strain.
From the transverse shear strength tests, it has been observed better to conduct the test at a higher
speed since the transverse shear strength is a matrix dominant property of the uniaxial reinforcements.
It is therefore recommended that the tests take place over a short period with the failure occurring
between 1 and 3 minutes. The transverse shear test method is useful only for characterizing the
strength of a reinforcement crossing a tight crack or joint, but the method does not provide general
shear strength for design in other situations.

5. CONCLUSION
This paper contributes an experimental program to develop the tensile and transverse shear strength
characterization of hybrid reinforcements. As per the results the hybrid reinforcements show superior
performance in both the cases. The tensile strength of hybrid reinforcements is 50% higher than steel
reinforcements and 45% higher than GFRP reinforcements whereas the tensile modulus is found to be
10 times lesser than that of steel and 5 times greater than GFRP reinforcements. The transverse shear
strength of Hybrid reinforcements is 2-3 times higher than that of GFRP reinforcements and steel
reinforcements. It has been noted that the strength varies according to the test speed and the time taken
by the specimen at failure. The volume fraction of carbon and glass may be varied in the future study.
Also the future tests may be carried out for Hybrid reinforcements with a bigger cross sectional area.
ACKNOWLEDGMENTS
The authors wish to express their gratitude and sincere thanks to the Meena Fiberglass Industries
Puducherry, India for manufacturing and providing the Hybrid Reinforcements from their industry and
also like to thank the technical staff in the strength of materials laboratory Annamalai University for
their assistance in testing the specimens.
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STRENGTH CHARACTERIZATION OF GLASSCARON HYBRID REINFORCEMENTS - AN EXPERIMENTAL INVESTIGATION

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STRENGTH CHARACTERIZATION OF GLASSCARON HYBRID REINFORCEMENTS - AN EXPERIMENTAL INVESTIGATION