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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


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


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.



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.



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



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



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



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).


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.



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).


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).


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.



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.



• 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.

REFERRENCES [1] Jiming Zhou, James P. Lucas “The effects of a water environment on anomalous absorption behavior

in graphite/epoxy composites” Composites Science and Technology, Volume 53, Issue 1, 1995, Pages

57–64

[2] R. Selzer, K. Friedrich “Mechanical properties and failure behaviour of carbon fibre-

reinforced polymer composites under the influence of moisture”Composites Part A: Applied

Science and Manufacturing, Volume 28, Issue 6, 1997, Pages 595–604

[3] E.C. Botelho, L.C. Pardini, M.C. Rezende “Hygrothermal effects on damping behavior of

metal/glass fiber/epoxy hybrid composites” Materials Science and Engineering: A, Volume

399, Issues 1–2, 15 June 2005, Pages 190–198

[4] Z. Sereir, N. Boualem “Damage of hybrid composites under long term hygrothermal loading

and stacking sequence” Theoretical and Applied Fracture Mechanics, Volume 47, Issue 2,

April 2007, Pages 145–163

[5] H.K. Cho “Optimization of dynamic behaviors of an orthotropic composite shell subjected to

hygrothermal environment” Finite Elements in Analysis and Design, Volume 45, Issue 11,

September 2009, Pages 852–860

[6] Y.I. Tsai, E.J. Bosze, E. Barjasteh, S.R. Nutt “mechanical properties of carbon fiber/fiberglass

hybrid composites” Composites Science and Technology, Volume 69, Issues 3–4, March

2009, Pages 432–437

[7] E. Barjasteh, S.R. Nutt “Moisture absorption of unidirectional hybrid composites”

Composites Part A: Applied Science and Manufacturing, Volume 43, Issue 1, January 2012,

Pages 158–164

[8] Jiming Zhou, James P. Lucas “Hygrothermal effects of epoxy resin. Part I: the nature of water

in epoxy” Polymer, Volume 40, Issue 20, September 1999, Pages 5505–5512

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