International Journal of Mechanical Engineering and Technology (IJMET)
Volume 10, Issue 04, April 2019, pp. 153–165, Article ID: IJMET_10_04_014
Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=4
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(4), 2019, pp. 153–165.
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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
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
of 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 thermomechanical 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
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Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi
Dynamic mechanical Analysis (DMA), Differential scanning Calorimetry (DSC), Thermo
gravimetric analysis (TGA) respectively. The values
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
Orientation
1
0
2
45
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3
90
4
-45
155
5
-45
6
90
7
45
8
0
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
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
Orientation
Fiber
1
0
Carbon
2
45
Glass
3
90
Carbon
4
-45
Glass
5
-45
Glass
6
90
Carbon
7
45
Glass
8
0
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
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Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi
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
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
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
DSC
TGA
Carbon (in mg)
5.2
18.81
Glass (in mg)
5.2
6.472
Hybrid(in mg)
5.2
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 difference 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
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Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi
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 different 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
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
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 different 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
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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, effectively 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)
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
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)
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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 100 0C 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.
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Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites
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.
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