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International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November 2018, pp. 704–714, Article ID: IJMET_09_11_071
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=9&IType=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication Scopus Indexed
EXPERIMENTAL INVESTIGATION OF
HYGROTHERMAL BEHAVIOUR OF HYBRID
COMPOSITE MATERIALS
*G. GuruSaiPrasad, V.Ajay, G.Guru Mahesh and D.Raju
Assistant professor, SV College of engineering, Tirupati
*corresponding author
ABSTRACT
In the present work was mainly concern with fabrication and testing of hybrid
composites like Glass-Kevlar, Kevlar-Carbon, and Glass-Carbon. Environmental
exposure can induce various chemical and physical processes of degradation in FRP
composites. The relative rates of these degradation processes depend on the chemistry of
the fibre and matrix, temperature, length of exposure and the stress state.
The hybrid composites are immersed in different chemicals likesaline water, HCL and
H2SO4 solutions for different period of time to evaluate hygrothermal behaviour. For
experimentation, specimens are sized as per ASME standards and analysing the result of
strength, stiffness of hybrid composites by tensile and flexural tests using UTM machine.
Keywords: Glass-Kevlar, Kevlar-Carbon, Glass-Carbon, hygrothermal behaviour, saline
water, HCL and H2SO4 solutions.
Cite this Article G. GuruSaiPrasad, V.Ajay, G.Guru Mahesh and D.Raju, Experimental
Investigation of Hygrothermal Behaviour of Hybrid Composite Materials, International
Journal of Mechanical Engineering and Technology, 9(11), 2018, pp. 704–714.
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=9&IType=11
1. INTRODUCTION
The fiber reinforced polymer (FRP) use is substantial increase in the place of conventional
construction materials in recent years. Many engineers from the world are leaning towards FRP
composite material because of their stiffness characteristics, specific strength, and endurance of
fatigue loading, light weight and ease to fabrication. The advanced composite material
mechanical properties depend on the fabrication technique and environmental condition used to
produce the laminates.
FRP process equipment is used in many industrial applications like chemical storage tanks,
chemical piping system, cooling tower elements, underground fuel storage tanks, oscillating
columns, wind turbines, automobiles, aerospace, ship building etc. The composites like FRP is
found in wide variety of applications in pre-stressing tendons and reinforced bars which are made
from FRP are being used in newly construction projects. By adding to these the FRP also used
for architectural applications like partition walls and roofing.
G. GuruSaiPrasad, V.Ajay, G.Guru Mahesh and D.Raju
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However, the usage of FRP to fullest potential has been hampered in considering the fact
about that their performance and reliability over long period of time. Exposure to water, humidity,
alkalis, temperatures and various harsh condition environment can induce physical and chemical
changes in polymer composites. When there are exposing to water or moisture, the FRP
composites have been showing the parameter line strength, plasticization of matrix and also
degradation of fiber/matrix interface. The environmental exposure can induce various physical
and chemical processes of degradation in FRP composites. The relative rates of degradation
processes will depends on chemistry of the fiber and matrix, length of exposure, temperature and
stress state. Therefore, a better understanding of FRP composites behaviour under the
environment is absolutely essential to aid the optimal design and prediction of service life in
structural components conducted on these meterials.
2. LITERATURE REVIEW
The various physicochemical changes are comes in to picture when polymeric composites are
exposed to moisture. The various experiments has revealed that hydrolysis and plasticization ate
the two main causes of degradation of polymeric matrices and polymeric composites during the
process of hygrothermal aging.
Jiming Zhou, James P. Lucas1was studied on the moisture (H2O) absorption characteristics
of T300/934 a unidirectional epoxy/graphite composite material by the measurement analysis of
change of weight, the hygrothermal induced expansion, formation of surface crack, and loss of
mass on surface. The specimens were immersed in distilled water at 45, 60, 75, and 90 °C for
more than 8000 h. From the theoretical Fickian diffusion law gives the weight change profiles
for the composite exhibited divergence. The SEM (Scanning electron microscopy) gives the
dimension measurement revealed clear evidence of surface peeling and specimen in dissolution.
The mass-loss model has been in order to give explanation about the behaviour of composite
material during water absorption process. The general characteristics of water induced weight
gain in epoxy/graphite composites are discussed with respect to diffusion phenomenon and
deviation in the weight change profiles.
R. Selzer, K. Friedrich2was investigated the effect of moisture in different mechanical
properties and failure behaviour on fiber reinforced polymer composites. The moisture is
introduced in to the specimen by immersing in distilled water. The three different materials which
are reinforced with continuous carbon fibers. The two thermosetting matrices (unmodified and
toughness modified epoxy) and one thermoplasticmatrix (polyetherketone) were used.
E.C. Botelho, L.C. Pardini, M.C. Rezende3 studied that Continuous fiber/metal laminates
(FML) gives the drastic improvements over the present available materials for structures like
aircraft due to their excellent fatigue conditions and low density. Glass fibers/epoxy laminate
and aluminum foil (Glare) are used commonly to gain these hybrid composites. Therefore the
combination of two materials in glare (metal and polymeric composite), can be used to propagate
good beneficial mechanical properties and resistance offers to ensure environmental influences.
In these paper they evaluated the viscoelastic properties such as loss modulus (E″) and storage
modulus (E′) are obtained for glass fiber epoxy composite, the aluminium 2024-T3 alloy and for
a glass fiber/epoxy/aluminium laminate (Glare).
Z. Sereir, N. Boualem4are persons who studied and given exposure of polymeric composite
matrix to the cyclic moist environment which produces transient residual stress to extremely at
the edges of laminated plates, the particularly at first times. In the case of critical cyclic
environmental conditions, the probable the damage of composites occurs, so as durability in
intensively reduced. To avoid the probability of damage, it has to reduce the transient
hygrothermal stresses, in this paper the hybrid composites with optimal stacking sequences are
used.
Experimental Investigation of Hygrothermal Behaviour of Hybrid Composite Materials
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H.K. Cho5has optimized the dynamic responses of an orthotropic plate subjected to
hygrothermal. The Non-gradient evolutionary genetic algorithm (GA) is employed to orthotropic
composite optimize dynamic behaviours. Under the optimization scheme the whose approach is
advantageously conducted in conjunction with FEA, which controls the fiber direction of element
to element.
Y.I. Tsai, E.J. Bosze, E. Barjasteh, S.R. Nutt6are the researches who studied he absorption
and diffusion of water in carbon fiber hybrid composite was investigated. Water sorption
experiments, dynamic mechanical analysis (DMA) and mechanical property tests were performed
by immersing the water at different temperatures for up to 32 weeks of time. The moisture uptake
mechanism will exhibited the hybrid fiber system was determined for more complex than single
fiber type. The weight change profiles of composites are fitted to theoretical fickian diffusion
curve during the initial immersion time, due substantial divergence the time will progressed.
E. Barjasteh, S.R. Nutt7 are investigated the unidirectional hybrid composite rods. When the
rods were conditioned in humidity air to study the sorption kinetics and effects of moisture on
various mechanical and physical properties. The sorption curves can be obtained from both non-
hybrid and hybrid composite rods to determine characteristic parameters which include diffusion
coefficient (D) and the maximum moisture uptake (M∞). The moisture uptake for hybrid
composites will generally exhibited Fickian behaviour (no hybridization effects), behaving much
like non-hybrid composites
Jiming Zhou, James P. Lucas8 are the young researches who studied the nature of absorbed
water and the related hygrothermal effects in epoxy resins. In this paper is the first of a two-
paper series. Three epoxy systems, DGEBA+mPDA, TGDDM+DDS, and Fiberite 934, were
used in the investigation. Water sorption was achieved by immersing the materials in distilled
water at constant temperature of 45°C, 60°C, 75°C and 90°C for 1530 h. The desorption profiles
and water absorption are determine the diffusion paremeters. The solid state nuclear magnetic
resonance (NMR) was conducted to determine the water in epoxy mobility. The study shows that
water molecules bind with epoxy resins through hydrogen bonding.
3. METHODOLOGY
3.1. Mould Preparation
In order to fabricate the laminates of composite materials the first and the foremost requirement
was of a mould. The mould required was of high strength, high thermal resistivity as the laminates
during the course of fabrication could produce lot of heat and can also attain deformation. To
avoid such situations a mild steel mould was used instead of any other material mould like wood,
plastic etc. after the material selection the other main criteria were of the correct geometry of the
mould. Thus a mould with required geometry was designed. The mould was prepared using mild
steel sheets and channels of 5mm thickness. The dimensions of the plate were taken as 325x300
mm. This plate was carefully welded with channels on three sides with one side as a provision
for the removal of laminate. After the welding, to fill the air gaps left after the welding between
the plate and the channels a layer of Janata paste was applied and later the extra material on the
surface was removed by means of coarse emery paper. Later a secondary operation was also
performed by the means of fine emery paper in order to smoothen the whole mould. For the
convenient handling of the mould two handles were welded on either sides of the mould. After
the completion of the bottom part of the mould a top plate with the same dimensions as of the
plate of the bottom part is taken and a handle is welded on the top of it. The top plate not only
helps in covering the laminate but the main purpose of using it is to make sure that the weight is
equally distributed throughout the laminate and to avoid deformation and uneven surface of
laminate. Hence the mould is prepared and ready for the fabrication of laminate.
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Figure 1 Preparation of Mould
3.2 Experimentation
3.2.1 Fabrication
After the preparation of mould the next task was of selecting required materials as to prepare the
laminates with different hybrid combinations. Thus through market research and literature survey
three different composite fibers were selected and they are Kevlar k-29, GFRP woven roving
(WR350/125) and 6k Carbon fiber fabric 2x2 twill weave. These materials were selected because
of their exceptional properties and suitability for project.
Table 1 Material Selected
Material GSM Thickness Weave type
Kevlar k-29 450 0.61mm Plain
Glass fiber 350 0.5µm Woven roving
Carbon fiber 320 0.5µm Twill weave
After the selection of fabric material there was a requirement of matrix suitable to prepare
laminates by combination of these materials. Hence the Epoxy resin LY556 with a hardener
HY951 was selected which is a room temperature curing matrix. These raw materials were cut
into sizes that of the mould i.e., 325x300 mm. Now the cut samples of Kevlar k-29 and 6k Carbon
fiber fabric were taken to prepare a hybrid laminate. Before the fabrication process a moiller film
which acts as a releasing agent. The moiller film is cut same as the size of the mould and placed
before the first layer of the laminate to prevent the sticking between the laminate and the mould.
Now after placing the moiller film in the mould a layer of mixture of hardener and resin is applied
on the moiller film. Then the first layer of Kevlar fiber is placed on the resin applied moiller film
and again a mixture of resin and hardener is applied, then second layer of carbon fiber is placed
on the resin mixture applied Kevlar fiber.
This process is continued until five layers of each Kevlar and carbon fiber are applied one
upon the other with a layer of resin between each layer of them. With this completion of layer
forming the laminate thickness will become around 5mm. At last a layer of resin is applied and
moiller film is placed on the top and the top plate of the mould is placed on the moiller film to
close the mould which will also act as a weight on the laminate. This mould with laminate is kept
around 24 hours in a room temperature for curing. Now the hybrid laminate of Kevlar k-29 and
6k Carbon fiber fabric with an Epoxy resin as matrix is prepared.
Similarly the whole above process is continued to prepare the two other combinations of
Kevlar k-29 & Glass fiber WR hybrid laminate and 6k Carbon fiber fabric & Glass fiber WR
hybrid laminate.
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Figure 2 Mixing of resin and catalyst Figure 3 Preparation of Laminates
Figure 4 Prepared Laminated sheet
3.2.2 Specimen Cutting
Laminates which are ready after the 24 hours of curing are carefully removed from mould and
the moiller film which is attached at the bottom and top of the laminate are peeled off. Now the
laminates are grinded at the corners to smoothen the irregularities. Now there is a need for testing
of the laminates at different conditions. Therefore the laminates are cut into no of specimens of
required dimensions according to the tests to be performed. The dimensions with which the
specimens were cut are 180x30x5 for tensile and 120x30x5 for flexural tests.
Figure 5 marking as per ASME standards Figure 6 Cutting the sheets as per dimensions
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Figure 7 Final specimens
3.2.3 Solutions Preparation
The conditions at which the specimens are subjected are saline water, HCL solution with 3%
concentration and H2SO4 with 3% concentration. Saline water solution is prepared by mixing
NACL granules in a proportion of 3.5gms per 100ml of water. In this proportion the solution is
mixed in the required quantity and NACL granules are well stirred until the granules are
completely dissolved in water. This is how the saline water solution is prepared. The HCL
solution of molecular weight 36.46 and specific gravity 1.18 is mixed in water to dilute and to
form a 3% concentration solution. This is how HCL solution is prepared. The H2SO4 solution of
98% concentration and specific gravity of 1.835 is mixed in water to dilute it up to a 3%
concentrated solution.
Figure 8 Preparation of saline water Figure 9 Preparation of H2SO4 and CL
solution with saline water
Figure 10 Dipping of Glass-Kevlar in solution
3.2.4 Specimens Dipping in Solutions
In saline water solution two specimens of Kevlar k-29 & Glass fiber WR hybrid laminate 6k
Carbon fiber fabric & Glass fiber WR hybrid laminate and Kevlar k-29 &6k Carbon fiber fabric
hybrid laminate are submerged completely in the solution for 2weeks. Similarly same process is
H2SO4
HCL
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carried for 6weeks. In the same way the specimens are submerged in the two solutions of HCL
and H2SO4 solutions. The two specimens of each laminate are one for tensile and one for flexural
tests which were cut accordingly as per the machine requirement and standard.
Figure 11 Dipping of Glass-Carbon in solution Figure 12 Dipping of Kevlar-Carbon in solution
3.3. Testing
The test specimens after the subjection of test conditions are taken to lab. The specimen is gripped
in the jaws with 30mm on both side and leaving gauge length of 120mm. the data of specimen is
to the software and the tear load is applied. Gradually the load is applied on the specimen thus
tearing the specimen and giving the tensile value. Similarly the
Figure 13 Tensile test of specimen in UTM Figure 14 Failure mode of the specimen
Figure 15 Flexural test of specimen in UTM Figure 16 Specimens failure in Flexural test
4. RESULTS AND DISCUSSION
Table 2 Tensile - Ultimate/Break loads (kN).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 30.70 28.540 27.680 27.00 26.740
Glass-Carbon 40.54 34.660 32.320 20.36 30.300
Kevlar-
Carbon 40.36 39.060 38.440 38.84 40.140
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From the table it can be observed that the break load of the glass-carbon/epoxy hybrid
composite is more when compared to other two hybrid combinations of composite in dry
conditions. In the remaining i.e wet condition the break load is more for Kevlar-carbon/epoxy
hybrid composite.
Table 3 Tensile - Maximum Displacement (mm).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 13.500 14.800 11.600 8.000 10.400
Glass-Carbon 14.900 7.400 7.900 9.600 6.100
Kevlar-
Carbon 15.700 16.800 17.900 15.200 10.900
From the table it can be observed that the maximum displacement of the Glass-Kevlar /epoxy
hybrid composite is less when compared to other two hybrid combinations of composites in dry
but in wet conditions Glass-Carbon /epoxy hybrid composite is less when compared to other two
hybrid combinations.
Table 4 Tensile - Ultimate Stress (kN/mm2).
Mat./Sol. Dry SW(2weeks
)
SW(6weeks
) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 0.205 0.190 0.185 0.180 0.178
Glass-Carbon 0.270 0.231 0.215 0.136 0.202
Kevlar-
Carbon 0.269 0.260 0.256 0.259 0.268
From the table it can be observed that the ultimate stress of the glass-carbon/epoxy hybrid
composite is more when compared to other two hybrid combinations of composite in dry
conditions. In the remaining i.e wet condition the ultimate stress is more for Kevlar-carbon/epoxy
hybrid composite.
Table 5 Tensile-Percentage Elongation (%).
Mat./Sol. Dry SW(2weeks
) SW(6weeks) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 6.667 5.833 4.167 5.833 5.000
Glass-Carbon 4.167 4.167 6.667 4.167 5.833
Kevlar-
Carbon 11.60 5.000 8.333 6.667 5.000
From the table it can be observed that the percentage elongation of the Kevlar -carbon/epoxy
hybrid composite is more when compared to other two hybrid combinations of composite in dry
conditions as well as in wet conditions.
Table 6 Tensile - Displacement at FMax (mm).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2 w) H2SO4(2
w)
Glass-Kevlar 11.400 11.800 10.700 5.000 7.200
Glass-Carbon 14.600 6.900 7.000 8.600 5.500
Kevlar-Carbon 15.100 16.100 12.100 10.300 7.100
The displacement at the maximum force is more for Kevlar-carbon/epoxy hybrid composite
in all test condition when compared to the other hybrid composites except in the H2SO4 solution,
where the displacement is more for glass-kevlar/epoxy composite.
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Table 7 Flexural - Ultimate/Break loads (kN).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2
w) H2SO4(2 w)
Glass-
Kevlar 5.060 5.040 4.980 4.820 5.000
Glass-
Carbon 6.160 6.040 6.040 6.000 6.060
Kevlar-
Carbon 6.060 5.740 5.560 5.500 5.860
The table shows that the break load of the glass-Carbon/epoxy composite is high subjected to
three point bending all the test conditions when compared to the other two hybrid composites.
Table 8 Flexural - Maximum Displacement (mm).
Mat./Sol. Dry SW(2week
s)
SW(6week
s) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 30.500 27.500 34.400 34.000 25.600
Glass-Carbon 23.600 27.900 27.900 17.900 25.900
Kevlar-
Carbon 22.800 27.200 26.800 21.300 24.400
The maximum displacement value is more for glass-kevlar/epoxy composite under the test
conditions of dry as well as in wet conditions.
Table 9 Flexural - Ultimate Stress (kN/mm2).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 0.034 0.030 0.033 0.032 0.033
Glass-Carbon 0.041 0.040 0.040 0.040 0.040
Kevlar-Carbon 0.040 0.038 0.037 0.037 0.039
The ultimate stress value of glass-carbon/epoxy hybrid composite is high for all the test
conditions when compared to other two hybrid composites.
Table 10 Flexural - Displacement at FMax (mm).
Mat./Sol. Dry SW(2weeks) SW(6weeks) HCL(2 w) H2SO4(2 w)
Glass-Kevlar 0.700 2.000 2.400 3.700 3.300
Glass-Carbon 3.700 3.700 3.700 1.100 0.900
Kevlar-
Carbon 0.1 2.000 0.100 2.300 0.100
The displacement at maximum force is more for glass-carbon/epoxy composite in the dry as
well as saline water test condition both for 2weeks and 6 weeks and the value is high for glass-
kevlar/epoxy hybrid composites in acid test conditions of HCL and H2SO4 solutions.
5. COMPARING WITH GRAPHS
The following graphs shows the comparison of tensile and flexural test experimental data of
different composite material specimens which dipped in various solutions with parameters like
ultimate bread load, max displacement, ultimate stress, percentage of elongation, and
displacements are evaluated.
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Figure 17 Tensile test on Glass-kevlar Figure 18 Tensile test on Glass-carbon
Figure 19 Tensile test on Kevlar-carbon Figure 20 Flexural test on Glass-kevlar
Figure 21 Flexural test on Glass-carbon Figure 22 Flexural test on Glass-carbon
The above graphs of 5.1, 5.2, 5.3, 5.4, 5.5 and 5.6 which reveals the deviation mentioned
parametric values of hybrid composite materials like glass-Kevlar, glass-carbon, and Kevlar
carbon.
6. CONCLUSION
From the above study it is concluded that:
• The tensile strength of the Kevlar-Carbon/Epoxy was found to be 42% greater than
Glass-Kevlar/Epoxy and 33% greater than Glass-Carbon/Epoxy in wet conditions.
• The tensile strength of the Glass -Carbon/Epoxy was found to be 32% greater than
Glass-Kevlar/Epoxy and 0.4% greater than Kevlar -Carbon/Epoxy in dry conditions.
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• The flexural strength of the Glass -Carbon/Epoxy was found to be 21% greater than
Glass-Kevlar/Epoxy and 6.5% greater than Kevlar -Carbon/Epoxy in wet conditions.
• The flexural strength of the Glass -Carbon/Epoxy was found to be 21% greater than
Glass-Kevlar/Epoxy and 1.6% greater than Kevlar -Carbon/Epoxy in dry conditions.
• The Max. Displacement in bending of the Kevlar-Carbon/Epoxy was found to be 33%
less than Glass-Kevlar/Epoxy and 3.5% less than Glass-Carbon/Epoxy in dry
conditions.
• The Max. Displacement in bending of the Glass -Carbon/Epoxy was found to be 21%
less than Glass-Kevlar/Epoxy and 0.1% less than Kevlar -Carbon/Epoxy in wet
conditions.
• The Max. Displacement in tensile of the Glass - Kevlar /Epoxy was found to be 16%
less than Kevlar- Carbon /Epoxy and 10% less than Glass-Carbon/Epoxy in dry
conditions.
• The Max. Displacement in tensile of the Glass -Carbon/Epoxy was found to be 44%
less than Glass-Kevlar/Epoxy and 96% less than Kevlar -Carbon/Epoxy in wet
conditions.
• The flexural resistance is found to be high in Glass-Carbon/Epoxy.
• The hybrid composite which showed resistance to acidity under tensile load is Kevlar-
Carbon/Epoxy.
• The hybrid composite which showed resistance to acidity under flexural load is Glass-
Carbon/Epoxy.
• Kevlar-Carbon/Epoxy is more resistant to salinity under tensile load.
• Glass-Carbon/Epoxy is more resistant to salinity under flexural.
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