Thermal characterization of fiber reinforced polymer composites and hybrid composites

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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 unidirectional.

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Nội dung Text: Thermal characterization of fiber reinforced polymer composites and hybrid composites

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 http://www.iaeme.com/IJMET/index.asp 1055 editor@iaeme.com
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 http://www.iaeme.com/IJMET/index.asp 1056 editor@iaeme.com
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 http://www.iaeme.com/IJMET/index.asp 1057 editor@iaeme.com
Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites 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 http://www.iaeme.com/IJMET/index.asp 1058 editor@iaeme.com
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 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 http://www.iaeme.com/IJMET/index.asp 1059 editor@iaeme.com
Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites 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 http://www.iaeme.com/IJMET/index.asp 1060 editor@iaeme.com
Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi 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. http://www.iaeme.com/IJMET/index.asp 1061 editor@iaeme.com
Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites 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 http://www.iaeme.com/IJMET/index.asp 1062 editor@iaeme.com
Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi 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) http://www.iaeme.com/IJMET/index.asp 1063 editor@iaeme.com
Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites 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. http://www.iaeme.com/IJMET/index.asp 1064 editor@iaeme.com
Bhasker Bommara, Dr. M. Devaiah, P. Laxmi Reddy, M. Ravindra Gandhi 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 http://www.iaeme.com/IJMET/index.asp 1065 editor@iaeme.com
Thermal Characterization of Fiber Reinforced Polymer Composites and Hybrid Composites 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. http://www.iaeme.com/IJMET/index.asp 1066 editor@iaeme.com