Type: Evaluation Essays
Sample donated: Kent Barker
Last updated: July 21, 2019
terials are frequently used materials now days in engineering applications.
In the present research work similar attempt is made to study the effect ofsilicon di-oxide (SiO2) as filler on mechanical behaviour of glassfiber reinforced epoxy composites, in primary and advanced applications. Thisstudy shows that the addition of SiO2 into GFRP composites hasincreased its mechanical properties. Scanning electron microscope (SEM), amorphological analysis was carried out to observe the bonding between matrixand reinforcement and also clearly indicates the mode of failure in thecombination of crack in matrix, fiber debonding and fiber pullout for all typesof composites. Keywords—Epoxy, Glass fiber, Silicon di-oxide (SiO2),Mechanical properties and SEM analysis.1.
IntroductionGlass fiber reinforced polymer matrix composites have beenextensively used in in various field such as aerospace, marine, industries,automobiles, defense etc. a possibility that the incorporation of bothparticles and fibers in polymers could provide a synergism in terms of improvedproperties and performance has not been adequately explored so far. Howevercertain current reports suggest that by incorporating micro hard filler intothe polymer matrix of fiber reinforced composites. The current paper is tomechanical properties and SEM studies on glass-epoxy based composites withmixture SiO2. 2. Experimental Details2.
1 MaterialsPlainglass fabrics made of 360 g/m2 containing E-glass fabric of diameter12µm. The epoxy resin was mixed with the hardener (HY 951) in the ratio of100:12 by weight; hardener is used in curing of composites due to manyapplications. The filler chosen is silicon di-oxide (SiO2) using asa coupling agent and particle size 15-20µm. The details of mechanicalproperties of constituent are selected for present work shown in Table 1.2.2 Specimen preparationThe specimens are prepared byhand layup process. To prepare laminates with filler, calculated amount ofepoxy resin is weighed and taken in a separate container in calculatedquantity.
Once the materials are prepared for fabrication the next step is toprepare the composite plates using hand layup procedure. This procedure iscarried out for three different compositions 0%, 5%, 7.5%, 10% of SiO2 andglass-epoxy. The composite plates are cured at temperature of 80-900C and which is maintained at atemperature of 800C, to improve mechanical properties of compositeplates. Composite material fabricated is machined into dimensions of length330x330x3mm.Table 1:Composition of materials for required for fabrication of composites Sample Glass fabric weight (gm) Resin+ Hardener weight (gm) Filler weight (gm) Total weight of the plate (gm) 0% SiO2 311 207 0 518 5% SiO2 311 181 26 518 7.5% SiO2 311 168 39 518 10% SiO2 311 155 52 518 Fig 1: shows the hand lay-up procedure carried out for Glass epoxycomposites. 3.
Testing of mechanicalpropertiesThe mechanicalproperties of composite materials mainly depends upon the direction of fiberoriented is different in different direction.3.1 Tensile propertiesTensile strength is amount of materialstrength to resist pull. Tensile strength is also the measurement of materialsstrength when force is functional in two opposite direction. Fig 2: Tensile tested specimensThese resultscan be used to obtain the material characteristics such as brittleness orductility.According to this standard the dimensions of the specimens should be 165*19*3mm,below mentioned figure shows the dimensions of the specimen.3.
2 Flexural propertiesThis test comes underdestructive test method; it is also called as three point bending test. In thistest the specimens are in rectangular or circular shape and transverse bendingload is usually applied. The flexural strength gives the maximum stress withinthe experienced within the material and its moment of failure. The specimen prepared and tested accordingto ASTM D-790 standards. Accordingto this standard the dimensions of the specimen should be as of 80*8*3mm indimension.Fig 3: Flexural tested specimens The felxural strengthand flexural modulus can be calculated as follows:Flexuralstrength = 3FL 2wd2Flexuralmodulus = ML3 4wd3 3.3 Impact propertiesThis test measures the resistance of thespecimens for suddendly applied loads.
There are two methods to conduct thetest.The impact test specimens are cut fromthe hand laid specimens that are prepared before, the specimens are to be cutto the ASTM standards for impact testing, here in this operation the impacttesting is of two types, one is izod testing and the other is charpy testing,the testing for this specimen is done according to the charpy testing. The specimenis then cut from the plate of dimensions of ASTM standards of ASTM-D256, thedimensions of this standard is 65*12.5*3mm in dimension.Fig 4: Impact testedspecimens Impact strength =E/t x 1000E = Energy used to break (J)t = Thickness (mm)4.
Results and Discussion 4.1 Evaluationof mechanical propertiesThe mechanical properties such as density,tensile strength, flexural strength, shearstrength, impact strength and elongation at break of unfilled and SiO2 filledglass epoxy composites are listed in table 2. 4.1 Evaluation of mechanicalpropertiesThe mechanical properties such as density, tensilestrength, flexural strength, shear strength, impact strength and elongation atbreak of unfilled and SiO2 filled glass epoxy composites are listed intable 2.Table 2: Mechanical testingresults of composites Samples Density (gm/cm3) Tensile 0Strength (MPa) Flexural0’Strength (MPa) Impact 0Strength (J) G-E 1.984 213.04 26.
5 11 5%SiO2-G-E 2.06 243.81 27 12 7.
5% SiO2-G-E 2.15 244.52 27.53 16 10% SiO2-G-E 2.19 263.
55 30.59 18 4.2 Variation of densityFig 5: Density variationsBy observingall density variation graphs, it is observed that the density increases byincrease in filler percentage because the density of filler (SiO2)is greater than resin. It also observes that thecombination of Glass and epoxy shows the lesser density values than compared toGlass epoxy with SiO2.4.3 Tensile test resultsThe tensile strength of the%SiO2 specimens are shown in above table.
From the tableand graph shown above we can conclude that as the filler loading %increases, the tensile strength of thecomposite increases it also follow the same trend as that of 0% SiO2 specimens. By the general observationthe tensile stress of these combinations is significantly increasing withincrease in filler loading. The Maximumtensile strength in the current study is obtained for 10% SiO2-G-E composite andis establish to be 263.35 MPa, whichis approximately 1.5 times that of neatGlass-Epoxy composites.
Fig 6: Tensile properties of hybrid glass/SiO2reinforced epoxy composites 4.4 Flexural test resultsThe flexural strength of the compositesvaries from 26.5 to 30.
59 N/mm2and 19.58 to 24.52 N/mm2 and the maximum value is obtained for composite with 10 % of Silicon di oxide (SiO2)with G- E-SiO2. The above fig showsthat the combination of G-E-SiO2 hasmaximum flexural strength and the combination of G-E has minimum flexural strength. As the filler percentage increases the flexural strength of the composites increases. The reduction of flexural strength observed due to increase in filler material andmay be change in matrix properties reduce their strength between fiber and matrix. Fig 7: Flexural properties of hybrid glass/SiO2reinforced epoxy composites 4.
5 Impact test resultsThe above graph shows the impact energy observed variation in different filler loading. It is due to the strongbonding between filler materials and fiber structure. It exhibits higher impact energy observation for the G-E-SiO2 compositecombination compared to G-E composites.The increase of impact energy in G-J-Eis due to the strong bonding between fiber and the filler material. Compared to all the samples of the compositemeasured 7.5% SiO2 filledGalas-Epoxy composites shows advanced tensile strength followed by 5% and 10% SiO2 filledand the least strength is unfilledGlass-Epoxy composites.
Fig 8: Impactstrength of hybrid glass/SiO2 reinforced epoxy composites 5. Scanning Electron Microscope (SEM)SEM analysis is focused on evaluation of dispersion offiller in the matrix. Normally SEM pictures are used to find uniform mixing offiller with resin, dispersion of fillers in the matrix, evaluate the crackformation, effect of pull out of fiber after applying load etc. Fig 9: SEM micrographs of fr The fracture is due to Delamination between two layers of the compositespecimens and fibre pull out (figure a) for glass epoxy sample, the fracture isductile brittle and can be explained by plastic deformation of the matrix afterfiber matrix debonding.
The SEM micrographs shown in figure b supports thisfailure mechanism because the fibres on fractured surfaces are clean, whichshows brittle fracture. Fig10: SEM image of hybrid 5 wt. % of SiO2 filled glass/epoxycomposites after flexural testFigure 10 showsthe SEM characterization of the SiO2 filled G–E fractured surfaceshows that the fibers are more or less covered with the matrix and SiO2particles a qualitative indication of a greater interfacial strength.Disorientation of transverse fibers, fiber bridging, fibers pull out, inclinedfracture of longitudinal fibers, matrix rollers, and matrix cracking is alsoseenFig 11: SEM image of hybridglass/epoxy composites after impact test In the impactspecimen one can see the trans-laminar crack; the trans-laminar crack meansthere is breakage of the specimen surface there is little formation of crack onthe surface. The fibers in the specimens are pulled out in the impact and bendspecimens.
The pull out of the fibers are caused due to the weak interfacebetween the glass fiber and matrix. The laminates that were oriented one abovethe other the laminar strengths may be decreased are as seen in the abovefigure. 6. Conclusion The fabrication and experiment of glass fiber reinforced epoxycomposites with addition of silicon di-oxide (SiO2) weresuccessfully carried out and the results were tabulated along with the comparedresults.
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