THERMAL CHARACTERIZATION OF FIBER …...Department of Mechanical Engineering, Geethanjali College of...

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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 10, Issue 03, March 2019, pp. 1055–1066, Article ID: IJMET_10_03_106

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

THERMAL CHARACTERIZATION OF FIBER

REINFORCED POLYMER COMPOSITES AND

HYBRID COMPOSITES

Bhasker Bommara, Dr. M. Devaiah*, P. Laxmi Reddy, M. Ravindra Gandhi

Department of Mechanical Engineering, Geethanjali College of Engineering and Technology,

Hyderabad, Telangana State, India

*Corresponding Author

ABSTRACT

Hybrid composite materials are the great potential for engineering material in many

applications. Hybrid polymer composite material offers the designer to obtain the

required properties in a controlled considerable extent by the choice of fibers and

matrix. The properties are tailored in the material by selecting different kinds of fibre

incorporated in the same resin matrix.

In this paper, the thermal properties of GFRP, CFRP, and Carbon and Glass fibers

reinforced epoxy hybrid composite will be studied. The composites using are all uni-

directional. The compression moulding technique will be adopted for the fabrication of

hybrid composite materials. The thermal properties such as Glass transition

temperature, Thermal conductivity, Specific heat capacity are calculated using

Dynamic mechanical Analysis (DMA), Differential scanning Calorimetry (DSC),

Thermo gravimetric analysis (TGA) respectively.

Key words: Hybrid polymer Composites, fibers, thermal properties, compression

moulding technique.

Cite this Article: Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra

Gandhi, Thermal Characterization of Fiber Reinforced Polymer Composites and

Hybrid Composites, International Journal of Mechanical Engineering and Technology

10(3), 2019, pp. 1055–1066.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3

1. INTRODUCTION

Composites are one of the most advanced and adaptable engineering materials known to men.

Progresses in the field of materials science and technology have given birth to these fascinating

and wonderful materials. A composite material can provide superior and unique mechanical

and physical properties because it combines the most desirable properties of its constituents

while suppressing their least desirable properties. When considering high end engineering

applications, composites are to be made lightweight and strong so as to improve the

performance of the application. The in plane properties like tensile strength and stiffness of

Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites


fiber reinforced composites are known to be high. But fiber reinforced composites performs

poorly when under in plane compression or when through thickness properties are considered.

At present composite materials play a key role in aerospace industry, automobile industry and

other engineering applications as they exhibit outstanding Strength to weight and modulus to

weight ratio. Whereas thermo-mechanical properties like storage modulus, loss factor and glass

transition temperature of fiber reinforced composite is not up to the mark. High performance

rigid composites made from glass, graphite, Kevlar, and boron or silicon carbide fibers in

polymeric matrices have been studied extensively because of their application in aerospace and

space vehicle technology. Since the application of composites spread into almost all

engineering applications, it became a necessity to improve their thermo-mechanical properties.

The properties of these composite materials can be further enhanced by integrating both CFRP

and GFRP composites in a particular orientation and mixing ratio. Several fundamental

constitutive relations have been developed throughout the later part of 20th century which helps

in predicting the mechanical properties of the above mentioned materials. These relations can

be of consequence to the composition of the material before its preparation. In the recent year

considerable amount of research has been done on the composites for improvement in thermo-

mechanical properties of the composites.Lei Zhang et al. [1],studied thermal response of the

GFRP multi cellular specimens assembled with different fire resistant panels namely glass

magnesium (GM) board, gypsum plaster (GP) board and light weight calcium silicate (CS)

board. He measured and comparatively analyzed, in association with the damage patterns

observed. It was found that the fire resistant panels effectively mitigated the temperature

progressions developed in the GFRP components, thereby improving the fire insulation

performance of those structural assemblies. The GM board provided the best fire insulation

performance, with the highest temperature at the outer face of the upper GFRP flat panel being

less than 1200C after 90 minutes of fire exposure. Further, the effects of cavities and end closure

configurations of the multicellular assemblies on the heat transfer were evaluated and

highlighted.N Dubary et al. [2], investigated the impact damage tolerance of hybrid carbon and

glass fibers woven-ply reinforced Poly Ether Ether Ketone (PEEK) thermoplastic (TP)

laminates obtained by consolidation process is investigated. Service temperature being one of

the most important parameters to screen TP or thermosetting matrix for aeronautical purposes,

impact testing at room temperature (RT) and near the glass transition temperature (TG) has

been conducted. From the results, it turns out that temperature has little influence on the impact

behavior in terms of maximum force developed or maximum deflection, though it reduces the

dissipated energy especially at lower impact energy. Geortzen et al. [3],found the viscoelasticity

behavior of a carbon fiber/epoxy matrix composite material system used for pipeline repair has

been evaluated though dynamic mechanical analysis. The effects of the heating rate, frequency,

and measurement method on the glass transition temperature (TG) were studied. The increase

in TG with frequency was related to the activation energy of the glass transition relaxation. The

activation energy can be used for prediction of long term performance. All results indicate that

TG increases and the magnitude of the tan delta peak decreases with increasing levels of cure.

The measured tan delta peak TG’S of room temperature cured and post-cured composite

specimens ranged from 60 to 1290C .The largest overall variation in Tg for room temperature

cured specimens due to combined changes in heating rate, frequency, and measurement method

(tan δ or loss modulus peak) was 20.60C. In this paper, the thermal properties of GFRP, CFRP,

and Carbon and Glass fibers reinforced epoxy hybrid composite will be studied and compared

with. The composites using are all uni-directional. The compression moulding technique will

be adopted for the fabrication of hybrid composite materials. The thermal properties such as

Glass transition temperature, Thermal conductivity, Specific heat capacity are calculated using

Dynamic mechanical Analysis (DMA), Differential scanning Calorimetry (DSC), Thermo

gravimetric analysis (TGA) respectively. The values

Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi


2. FABRICATION AND EXPERIMENTATION

The fabrication of the sample is done by using compression molding technique. The specimen

has undergone some standard cuttings and weight measurements after the fabrication. The

thermal properties namely heat conductance, thermal transitions of the material has investigated

using Differential Scanning Calorimeter (DSC) and thermal stability of the material by Thermo

gravimetric Analysis (TGA).The epoxy used in this consists of LAPOX L12 as resin and K-6

as a hardener in the mixing ratio of 10:1 ratio resin and hardener respectively. For each sample

we have maintained this fixed ratio. Hardener is the material that causes the epoxy resin to get

stiff. Essentially it is the catalyst. The epoxy resin and hardener in 10:1 weight ratio is mixed

thoroughly to use preparation of the composite. The fibers used in this work are unidirectional

and having a thickness of 0.35mm. The weight of the carbon fiber is 230 gsm and weight of the

glass fiber is 220 gsm. Aunidirectional (UD) fabric is one in which the majority of fibers run in

one direction only. A small amount of fiber or other material may run in other directions with

the main intention being to hold the primary fibers in position, although the other fibers may

also offer some structural properties. Some weavers of 0/90° fabrics term a fabric with only

75% of its weight in one direction as a unidirectional, whilst for others the unidirectional

designation only applies to those fabrics with more than 90% of the fiber weight in one

direction. Unidirectional fibers usually have their primary fibers in the 0° direction (along the

roll a warp UD) but can also have them at 90° to the roll length (a weft UD). True unidirectional

fabrics offer the ability to place fiber in the component exactly where it is required, and in the

optimum quantity (no more or less than required). As well as this, UD fibers are straight and

uncrimped. This results in the highest possible fiber properties from a fabric in composite

component construction. For mechanical properties, unidirectional fabrics can only be

improved on by prepreg unidirectional tape, where there is no secondary material at all holding

the unidirectional fibers in place. In these prepreg products only the resin system holds the

fibers in place.

2.1. Fabrication of Specimen

The fabrication of the composite materials has done in the following procedure using

compression molding technique.

2.1.1. Preparation of Epoxy Resin

Initially, the Resin and Hardener are to be weighed to make sure available content of the

mixture. Then, using calculator estimate the amount of resin and hardener to be applied to the

fabricating material. The ratio of the mixture should be 10:1 resin and hardener respectively.

We have taken 300gm of resin and 30gm of hardener total constituting 330gm of epoxy resin

mixture. After mixing both the materials in a well defined ratio, stir the mixture with a spatula

so that the mixture will undergo some saturation. Allow the mixture to become a single content,

and then it can be used up to a limited time.

2.1.2. Preparation of carbon fiber composite using compression molding technique

Initially, cut the carbon fiber material according to the dimensions. Then, arrange each layer in

such a way that they are according to the orientation as shown below.

Table 1.Orientation of carbon composite layers

Layer number 1 2 3 4 5 6 7 8

Orientation 0 45 90 -45 -45 90 45 0

If you observe the orientation of each layer, it is a symmetrical composite with 8 layers and

thickness of whole composite is 3.2mm in which each layer constitutes a thickness of 3.5mm

without taking the thickness of epoxy resin which is applied to the layers of the composite. If



we consider the thickness of epoxy resin too, then it will become 0.4mm for each layer. Before

the fabrication of the composite, the mold should be cleaned properly to avoid any damages

caused due to the irregularities of the molds. The surfaces of the molds should be cleaned by a

material known as PV to wipe off the previously accumulated materials on the base mold as

well as covering mold. Now, one by one the layers of the material are placed on the base mold,

starting from the base layer fixed amount of epoxy resin is applied between each and every

layer. Every time the epoxy resin is applied make sure that the layers not moving from their

initial position and no other tangential force should applied on the layer, because while applying

the epoxy resin, the movement of the applier may disturb the orientation leading to induced

forces as discussed above. After completion of arrangement of the layers successfully, the

covering mold should be placed on the layered material in such a way that the orientation of the

layers should not be displaced and also the load or force applied on the mold should be

acceptable by the material without squeezing of epoxy resin from the layers of the material

which may vary from the desired output sample.

2.2.3. Preparation of glass fiber composite using compression molding technique

For the fabrication of glass fiber composite, the same method is followed and the orientation of

the layers is as same as carbon fibers as shown in table 1. The glass fiber is entirely different

from the carbon fiber in its behavior. The fibers are very sensitive to handle and even they peel

off one by one while applying the epoxy resin mixture to the layers, they just depart from each

other even small amount of force is applied on them. So, while applying the mixture, tale care

about the fibers not to peel off from the matrix.

2.1.4. Preparation of hybrid composite material using compression molding technique

In case of hybrid composite material, the orientation of layers is entirely different from that of

a carbon composite or glass fiber composite. In this composite each fiber layer will be attached

to other type of fiber layer i.e. one carbon fiber layer is attached with other glass fiber layer. As

in the case of carbon and glass fiber individual composites, the arrangement and orientation is

not so difficulty as they are same type of fibers. But, in case of hybrid there are two different

types of fibers and the interface between them should be strongly made by applying required

amount of epoxy resin between each and every layers. The orientation of the hybrid composite

layers is as follows

Table 2. Orientation of hybrid composite layers

Layer number 1 2 3 4 5 6 7 8

Orientation 0 45 90 -45 -45 90 45 0

Fiber Carbon Glass Carbon Glass Glass Carbon Glass Carbon

2.1.5. Description of Compression Molding Technique

Compression molding is a well known technique to develop variety of composite products. It

is a closed molding process with high pressure application. In this method, as shown in figure



Figure 2 Compression molding schematic view

2, two matched metal molds are used to fabricate composite product. In compression

molder, base plate is stationary while upper plate is movable. Reinforcement and matrix are

placed in the metallic mold and the whole assembly is kept in between the compression molder.

Heat and pressure is applied as per the requirement of composite for a definite period of time.

The material placed in between the molding plates flows due to application of pressure and heat

and acquires the shape of the mold cavity with high dimensional accuracy which depends upon

mold design. Curing of the composite may carried out either at room temperature or at some

elevated temperature. After curing, mold is opened and composite product is removed for

further processing. In principle, a compression molding machine is a kind of press which is

oriented vertically with two molding halves (top and bottom halves). Generally, hydraulic

mechanism is used for pressure application in compression molding. The controlling

parameters in compression molding method to develop superior and desired properties of the

composite are shown in figure 2. All the three dimensions of the model (pressure, temperature

and time of application) are critical and have to be optimized effectively to achieve tailored

composite product as every dimension of the model is equally important to other one. If applied

pressure is not sufficient, it will lead to poor interfacial adhesion of fiber and matrix. If pressure

is too high, it may cause fiber breakage, expulsion of enough resin from the composite system.

If temperature is too high, properties of fibers and matrix may get changed. If temperature is

low than desired, fibers may not get properly wetted due to high viscosity of polymers

especially for thermoplastics. If time of application of these factors (pressure and temperature)

is not sufficient (high or low), it may cause any of defects associated with insufficient pressure

or temperature. The other manufacturing factors such as mold wall heating, closing rate of two

matched plates of the plates and de-molding time also affect the production process. Generally,

some amount of temperature is applied in this process, it may be room temperature or some

other temperature based on the criteria of fabrication of composite. We have kept the whole

setup in room temperature as the system is adapted to room temperature and no more heat sore

has been used in order to generate additional amount of heat.

Figure 3. Composites fabricated by layup technique (a) CFC (b) GFC (c) HFC

2.2. Testing Methods Used in experimentations

We have investigated thermal characterization of composites using Differential Scanning

calorimeter and Thermogravimetric analyzer. The amount of samples used in the tests is as

follows.

Table 3 Weight of test specimen

Carbon (in mg) Glass (in mg) Hybrid(in mg)

DSC 5.2 5.2 5.2

TGA 18.81 6.472 34.94



2.2.1. Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry, or DSC, is a thermo-analytical technique in which difference

in the amount of heat required to increase the temperature of a sample and reference is measured

as a function of temperature. Both the sample and reference are maintained at nearly the same

temperature throughout the experiment. Generally, the temperature program for a DSC analysis

is designed such that the sample holder temperature increases linearly as a function of time.

The reference sample should have a well-defined heat capacity over the range of temperatures

to be scanned. The technique was developed by E. S. Watson and M. J.O'Neill in 1962 and

introduced commercially at the 1963 Pittsburgh Conference on Analytical Chemistry and

Applied Spectroscopy. The first adiabatic deferential scanning calorimeter that could be used

in biochemistry was developed by P.L.Privalov and D.R.Monaselidze in 1964 at Institute of

Physician Tbilisi, Georgia. The term DSC was coined to describe this instrument, which

measures energy directly and allows precise measurements of heat capacity.

Figure 4 Schematic view of DSC Figure 5. A working DSC setup

here are two types of DSC, one is Power compensated DSC in which power supply is kept

constant the other one is Heat flux DSC in which heat flux is kept constant.

2.2.2. Detection of phase transitions

The basic principle underlying this technique is that when the sample undergoes a physical

transformation such as phase transitions, more or less heat will need to flow to it than the

reference to maintain both at the same temperature. Whether less or more heat must flow to the

sample depends on whether the process is exothermic or endothermic. For example, as a solid

sample melts to a liquid, it will require more heat flow to the sample to increase its temperature

at the same rate as the reference. This is due to the absorption of heat by the sample as it

undergoes the endothermic phase transition from solid to liquid. Likewise, as the sample

undergoes exothermic processes (such as crystallization) less heat is required to raise the sample

temperature. By observing the diff erence in heat flow between the sample and reference,

differential scanning calorimeters are able to measure the amount of heat absorbed or released

during such transitions. DSC may also be used to observe more subtle physical changes, such

as glass transitions. It is widely used in industrial settings as a quality control instrument due to

its applicability in evaluating sample purity and for studying polymer curing.

An alternative technique, which shares much in common with DSC, is Differential thermal

analysis (DTA). In this technique it is the heat flow to the sample and reference that remains

the same rather than the temperature.When the sample and reference are heated identically,

phase changes and other thermal processes cause a difference in temperature between the

sample and reference. Both DSC and DTA provide similar information. DSC measures the

energy required to keep both the reference and the sample at the same temperature where as

DTA measures the difference in temperature between the sample and the reference when they

are both put under the same heat.The result of a DSC experiment is a curve of heat flux versus

temperature or versus time. There are two diff erent conventions: exothermic reactions in the

sample shown with a positive or negative peak, depending on the kind of technology used in



the experiment. This curve can be used to calculate enthalpies of transitions. This is done by

integrating the peak corresponding to a given transition. It can be shown that the enthalpy of

transition can be expressed using the following equation. Where ∆H is the enthalpy of

transition, K is the calorimetric constant, and A is the area under the curve. The calorimetric

constant will vary from instrument to instrument, and can be determined by analyzing a well-

characterized sample with known enthalpies of transition. DSC is used widely for examining

polymeric materials to determine their thermal transitions. The observed thermal transitions can

be utilized to compare materials, although the transitions do not uniquely identify composition.

The composition of unknown materials may be completed using complementary techniques

such as IRspectroscopy DSC makes a reasonable initial safety screening tool. In this mode the

sample will be housed in a non-reactive crucible (often gold or gold – plated steel), and which

will be able to with stand pressure (typically up to 100bar). The presence of an exothermic event

can then be used to assess the stability of a substance to heat. However, due to a combination

of relatively poor sensitivity, slower than normal scan rates (typically 2–3 °C/min, due to much

heavier crucible) and unknown activation energy, it is necessary to deduct about 75–100°C

from the initial start of the observed exotherm to suggest a maximal temperature for the

material. A much more accurate data set can be obtained from an adiabatic calorimeter, but

such a test may take 2–3 days from ambient at a rate of a 3°C increment per half-hour.

2.2.3. Thermo Gravimetric Analysis (TGA)

Thermo gravimetric analysis or thermal gravimetric analysis (TGA) is a method of thermal

analysis in which changes in physical and chemical properties of materials are measured as a

function of increasing temperature (with constant heating rate), or as a function of time (with

constant temperature and constant mass loss). TGA can provide information about physical

phenomena, such as second-order phase transitions, including vaporization, sublimation, and

absorption and desorption. Likewise, TGA can provide information about chemical phenomena

including chemisorptions, desolation (especially dehydration), decomposition, and solid-gas

reactions. TGA is commonly used to determine selected characteristics of materials that exhibit

either mass loss or gain due to decomposition, oxidation, or loss of volatiles. Common

applications of TGA are materials characterization through analysis of characteristic

decomposition patterns, studies of degradation mechanisms and reaction kinetics,

determination of organic content in a sample, and determination of inorganic (e.g. ash) content

in a sample, which may be useful for corroborating predicted material structures or simply used

as a chemical analysis. It is an especially useful technique for the study of polymeric materials,

including thermoplastics, thermosets, elastomers, composites, plastic films, fibers, coatings and

paints. Discussion of the TGA apparatus, methods, and trace analysis will be elaborated up on

below. Thermal stability, oxidation, and combustion, all of which are possible interpretations

of TGA traces, will also be discussed.

Thermo gravimetric analysis (TGA) relies on a high degree of precision in three

measurements: mass change, temperature, and temperature change. Therefore, the basic

instrumental requirements for TGA are a precision balance with a pan loaded withthe sample,

and a programmable furnace. The furnace can be programmed either for a constant heating rate,

or for heating to acquire a constant mass loss with time. Though a constant heating rate is more

common, a constant mass loss rate can illuminate specific reaction kinetics. For example, the

kinetic parameters of the carbonization of polyvinyl butyral were found using a constant mass

loss rate of 0.2 wt %/min. Regardless of the furnace programming, the sample is placed in a

small, electrically heated furnace equipped with a thermocouple to monitor accurate

measurements of the temperature by comparing its voltage output with that of the voltage-

versus-temperature table stored in the computer’s memory.



Figure. 6 Schematic view of TGA Figure 7 a working TGA setup

A reference sample may be placed on another balance in a separate chamber. The

atmosphere in the sample chamber may be purged with an inert gas to prevent oxidation or

other undesired reactions. A diff erent process using a quartz crystal micro balance has been

devised for measuring smaller samples on the order of a microgram (versus milligram with

conventional TGA). The TGA instrument continuously weighs a sample as it is heated to

temperatures of up to 2000°C for coupling with FTIR and Mass spectrometry gas analysis. As

the temperature increases, various components of the sample are decomposed and the weight

percentage of each resulting mass change can be measured. Results are plotted with temperature

on the X-axis and mass loss on the Y-axis. The data can be adjusted using curve smoothing and

first derivatives are often also plotted to determine points of inflection for more in-depth

interpretations.If the identity of the product after heating is known, then the ceramic yield can

be found from analysis of the ash content (see discussion below). By taking the weight of the

known product and dividing it by the initial mass of the starting material, them as percentage

of all inclusions can be found. Knowing the mass of the starting material and the total mass of

inclusions, such as ligands, structural defects, or side-products of reaction, which are liberated

up on heating, the stoichiometric ratio can be used to calculate the percent mass of the substance

in a sample. The results from thermo gravimetric analysis may be presented by mass versus

temperature (or time) curve, referred to as the thermogravimetric curve,or rate of mass loss

versus temperature curve, referred to as the differential thermo gravimetric curve.

2.2.4. Thermal stability by TGA

TGA can be used to evaluate the thermal stability of a material. In a desired temperature range,

if a species is thermally stable, there will be no observed mass change. Negligible mass loss

corresponds to little or no slope in the TGA trace. TGA also gives the upper use temperature of

a material. Beyond this temperature the material will begin todegrade. TGA has a wide variety

of applications, including analysis of ceramics and thermally stable polymers. Ceramics usually

melt before they decompose as they are thermally stable over a large temperature range, thus

TGA is mainly used to investigate the thermal stability of polymers. Most polymers melt or

degrade before 200°C. However, there is a class of thermally stable polymers that are able to

withstand temperatures of at least 300°C in airand500°C in inert gases without structural

changes or strength loss, which can be analyzed by TGA. For example, the polyimide Kapton

loses less than10% mass when held in 400°C air for 100 hours. High performance fibers can be

compared using TGA as an evaluation of thermal stability. From the TGA, Poly oxazole (PBO)

has the highest thermal stability of the four fibers as it is stable up to ca. 500 °C. Ultra high-

molecular-weight polyethylene (UHMW-PE) has the lowest thermal stability, as it begins to

degrade around 200°C. Often the onset of mass loss is seen more prominently in the first

derivative of the mass loss curve. High performance fibers used in bullet proof vests must

remain strong enough mechanically so as to protect the user from incoming projectiles. The

thermal and photo chemical degradation of the fibers causes the mechanical properties of the

vests to decrease, eff ectively rendering the armor useless. Thus, thermal stability is a key

property when designing these vests. Three ways a material can lose mass during heating are



through chemical reactions, the release of adsorbed species, and decomposition. All of these

indicate that the material is no longer thermally stable. Out of the four fibers shown in the

previous example, only Terlon shows loss of adsorbed species, most likely water, as the mass

loss occurs after 100°C. Because the TGA is performed in air, oxygen reacts with the organic

fibers which eventually degrade completely, evidenced by the 100% mass loss. It is important

to link thermal stability to the gas in which the TGA is performed.

3. RESULTS AND DISCUSSIONS

3.1. Differential Scanning calorimetry

3.1.1. Differential Scanning Calorimetry of Carbon Fiber Reinforced Polymer

As shown in the graph, there are some transitions that took place in carbon fiber composite

during differential scanning calorimetry. So, coming to the graph, it has exhibited an exothermic

property by conducting heat through it up to a temperature of 400C and from that point there

has been a decrease in conduction of heat through it and the change is varied linearly with a

negative slope indicating the endothermic reaction in which the material absorbs the heat

flowing through it and which is responsible for the decrease in the conduction of heat energy.

From 400C to 64.520C the conduction has fallen to a value of 1.790 J/g. there is a further

decrease in heat conduction from 64.520C to 70.200C but the graph has some disturbances in

its path so that the graph is not linear in this particular case due to a transition. After that

transition, the heat conduction again increased up to a temperature of 1280C approximately and

from there the conductance has again decreased. This is the variation of heat conduction in

carbon fiber composite through varying temperatures. Text values from the given graph (Fig 8)

(40,0.05) (50,0.75) (65,-0.1) (70,-0.15) (90,-0.125) (190,-0.175)

Figure 8 Differential Scanning Calorimetry of Carbon Fiber Reinforced Polymer

3.1.2. Differential Scanning Calorimetry of Glass Fiber Reinforced Polymer

From the graph, we can say there are many transitions in the composite at which there is a

change in conduction of heat and it has not followed any trend in the graph. Starting from a

point of temperature (40oC), there is a gradual increase in heat conductance up to 440C and

again sudden fall from 440C to 67.860C. The material has exhibited transitions in between

67.860C and 850C.at which there are irregular deflections in heat conductance without following

any trend. As the temperature increases from 1400C to 2000C there is a smooth negative curve

representing the endothermic process in which, conduction is further decreased due to

absorption of heat by the sample text values from the given graph (Fig 9) (42,0.15) (50,-0.1)

(65,-0.1) (67.86,-0.175) (72.71,-0.25) (85,-0.2) (140,-0.175)(195,-0.25)



Figure 9 Differential Scanning Calorimetry of (a) GFRP (b) HFRP

3.1.3. Differential Scanning Calorimetry of Hybrid Fiber Reinforced Polymer

The graph shows a regular trend in case of a hybrid material. The heat conductance has

increased from a point of room temperature to 410C exhibiting exothermic reaction in which,

heat is rejected or released by the sample. There is a smooth curve with negative slope indicating

the endothermic process in which the heat is absorbed by the sample and due to this, the

conduction decreased to a value of 1.206J/g till the sample reached a temperature of 62.980C

and there is a transition of sample at 68.58 C at which the sample reached a value of minimum

conduction of heat. There is again transition occured in between temperature of 90.82 C and

100 C at 92.19 C. an increase in heat conductance from point of 1000C to 1600C approximately

and from that there is a gradual decrease in conduction taking place.Text values from the given

graph (Fig 9) (45,0.075) (62.98,-0.1) (68.58,-0.25) (80,-0.175) (90.82,-0.25) (91,-0.285)

(92.19,-0.35) (104,-0.317)

3.2. Thermo Gravimetric Analysis

3.2.1. Thermo Gravimetric Analysis of Carbon Fiber Reinforced Polymer

In this test, initially the sample has no change in its mass up to 1000C from room temperature.

From 1000C it has deviated from its original mass and there is a slight decrease in its mass up

to 2000C from where the slope of the graph has an increase in its slope negatively, which

determines, increase in the rate of change in mass up to 3300C, this decrease in mass up to this

point denotes the evaporation of volatile substances from the sample. So, the sample has low

rate of mass change for a certain scale of temperature. From 3300C to 4500C there is a decrease

in the mass of the sample drastically, which indicates the evaporation of resin and hardener

mixture. But, still there is a further decrease in mass indicating the small traces of resin and

hardener mixture which, attached to the fibers of the sample. The final amount of traces left

over at 779.640C is the amount of pure fiber present in the sample. The percentage of mass fiber

in the whole sample is 51.71% indicating 9.729mg of fiber out of 18.8150mg of total sample.



Figure 10 Thermo Gravimetric Analysis of (a) CFRP (b) GFRP

3.2.2. Thermo Gravimetric Analysis of Glass Fiber Reinforced Polymer

Initially, for the sample, the volatile particles have been evaporated up to 2800C approximately,

up to which, the change in mass is very less when compared to that of rest of the graph. From

3000C to 4000C the mass has decreased drastically i.e. the percent of mass change is nearly

32.18% within a gap of 400C, indicating the evaporation of resin and hardener content in the

sample. The sample has further lost its mass up to 779.6400C gradually and the left over mass

is known as the fiber content in the sample. The graph has represented that the sample contains

57.53% of fiber content i.e. 3.7362 mg of fiber out of 6.4720 gm of total sample weight.

3.2.3. Thermo Gravimetric Analysis of Hybrid Fiber Reinforced Polymer

Same as both CFRP and GFRP, the Hybrid composite has lost its volatile substances up to

3000C from 2200C, similarly, the hardener and resin mixture in the sample has been undergone

vaporization from 3000C to 4100C which is represented by a steep slope of the curve as shown

by a tangent drawn normal to it at both the temperatures. The fiber content in the sample is

22.40 mg out of 34.9430 mg of total content, which constitutes a weight percent of 64.11% of

the total sample.

Figure 11 Thermo Gravimetric Analysis of Hybrid Fiber Reinforced Polymer

4. CONCLUSIONS

From both the tests, it is clear that no product is having thermal stability as they are changing

their properties with respect to change in temperature. The fiber content is more in GFRP

composite compared to CFRP and Hybrid fiber content. When coming to the transitions in DSC

test, the hybrid composite has shown a good transition than GFRP & CFRP composites it may

be due to the fiber and epoxy resin combination. Anyway, the GFRP composite has a good heat



conduction compared to both the composites but, the sample is not having stability as of CFRP

and Hybrid composite samples.

REFERENCES

[1] Bhagavan D. Agarwal, Lawrence J. Broutman, K. Chandrashekara. Analysis and

performance of fiber composites. Wiley studentedition.

[2] Mallik PK. Fiber reinforced composites. New York: CRC Press;2007.

[3] . IzzuddinZaman, Tam ThanhPhan, Hsu-Chiang Kuan, Qingshi Men, Ly TrucBao La, Lee

Luong, Osama Youssf, Jun Maa. Epoxy/graphene platelets nanocomposites with two levels

of interface strength. Polymer 52 (2011) 1603- 1611

[4] Ming-Yuan Shen, Tung-Yu Chang, Tsung-Han Hsieh, Yi-Luen Li, Chin-Lung Chiang,

Hsiharng Yang, and Ming-Chuen Yip. Mechanical Properties and Tensile Fatigue of

GrapheneNanoplateletsReinforced Polymer Nanocomposites. Journal of Nanomaterials

Volume 2013, Article ID 565401, 9pages.

[5] G.-H.Chen,D.-J.Wu,W.-G.Weng, andW.-L. Yan. Preparation of polymer/graphite

conducting nanocomposite by intercalation polymerization. Journal of Applied Polymer

Science, vol. 82, no. 10, pp. 2506–2513,2001.

[6] J. Li, M. L. Sham, J.-K. Kim, and G. Marom. Morphology and properties of UV/ozone

treated graphite nanoplatelet/epoxy nanocomposites. Composites Science and Technology,

vol. 67, no. 2, , (2007)296–305..

[7] Keith jamahl green. Multiscale fiber reinforced composites using a corbonnanofiber/epoxy

nanophased matrix: processing, and thermomechanicalbehaviour. Thesis submitted to

University of Alabama at Birmingham,2007.

[8] Kabalsinghbhangu. Mechanical properties of glass finer reinforced epoxy nanocomposites:

effect of different nanoclays. Thesis submitted to Thapar University Patiala,2014.

[9] Dr. Ronnie Bolick. Composite fabrication via the VARTM process. North Carolina A&T

State University: STTR N064 – 040 – 0400

[10] H Fukushima and L. T. Drzal, 2001. Graphite nanoplatelets as reinforcements for polymers.

Polymer Preperation. Volume 45, Pages 42-47.

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