StudyOn Mechanical & Cryogenic Properties of Carbon Epoxy CompositesSunil Kumar B.V *1,Dr.
Neelakantha V.Londe 21 Assistant Professor, Mechanical EngineeringDepartment, Canara Engineering College, Mangalore, VTU, Karnataka, India2 Professor, Mechanical Engineering Department,Mangalore Institute Of Technology and Engineering, Moodabidri, VTU, Karnataka,India(*Corresponding author E-mail: [email protected]) Abstract.
Carbon-fiber-reinforcedpolymers are composite materials. In this case the composite consists of twoparts: a matrix and reinforcement. In CFRP the reinforcement is carbon fiberwhich provides the strength. The matrix is usually a polymer resin such asepoxy to bind the reinforcements together. The material properties depend onthese two elements.
The reinforcement will give the CFRP its strength andrigidity measured by stress and elastic modulus respectively. Unlike isotropicmaterials like steel and aluminium CFRP has directional strength properties.The properties of CFRP depend on the layouts of the carbon fiber and theproportion of the carbon fibers relative to the polymer. This paper deals withthe studies done on cryogenic treatment (Liquid Nitrogen) of composites havingdifferent fiber and matrix composition. In this work studies are done to findthe effects caused by the liquid nitrogen on composites mechanical propertiesand change in properties due to different fiber and matrix composition in composites.
It was observed that due to cryogenic treatment there was changes in thephysical properties of the specimens. The specimens had deformed in theirshape. The more deformation was seen in 60:40 specimen which was treated for 48hrs and tensile strength of the composites at cryogenic temperature had highervalues than that normal temperature for 70:30 specimen which was treated for24hrs. The flexure strength of the composites at cryogenic temperature hadhigher values than the normal temperature for all the specimens. The flexurestrength is more for 70:30 specimen which was treated for 48hrs.1.
IntroductionInthe current quest for improved performance which may be specified by numerouscriteria comprising less weight, more strength and lower cost currently usedmaterials frequently reach the limit of their utility. Thus materialresearchers, engineers and scientists are always determined to produce eitherimproved traditional materials or completely novel materials 12. Compositeshave already proven their worth as weight-saving materials; the currentchallenge is to make them cost effective.
The hard work to produce economicallyattractive composite components has resulted in several innovativemanufacturing techniques currently being used in the composites industry. Thecomposites industry has begun to recognize that the commercial applications ofcomposites promise to offer much larger business opportunities than theaerospace sector due to the sheer size of transportation industry 13. The biggestadvantage of modern composite materials is that they are light as well asstrong. By choosing an appropriate combination of reinforcement material andmatrix, a novel material can be made that exactly meets the requirements of aspecific application.
Composites also give design flexibility because many ofthem can be moulded into complex shapes 17.Carbonfiber alternatively graphite fiber carbon graphite or CF is a materialconsisting of fibers about 5–10 ?m in diameter and composed mostly of carbon atoms.To produce carbon fiber the carbon atoms are bonded together in crystals thatare more or less aligned parallel to the long axis of the fiber as the crystalalignment gives the fiber high strength-to-volume ratio (making it strong forits size).
Several thousand carbon fibers are bundled together to form a towwhich may be used by itself or woven into a fabric 15.Figure 1.1 shows acarbon fiber fabric.
Theproperties of carbon fibers such as high stiffness, high tensile strength, lowweight, high chemical resistance, high temperature tolerance and low thermalexpansion make them very popular in aerospace, civil engineering, military, andmotorsports, along with other competition sports. Composites made from carbonfiber are five times stronger than grade 1020 steel for structural parts yetare still five times lighter. Figure1.1.
CarbonFiber Cryogenicsis defined as the branches of physics and engineering that study very low temperatures.How to produce them and how materials behave at those temperatures. Rather thanthe familiar temperature scales of Fahrenheit and Celsius, cryogenicists usethe Kelvin and Rankine scales 8.
Theword cryogenics literally means “the production of icy cold”; howeverthe term is used today as a synonym for the low-temperature state. It is notwell-defined at what point on the temperature scale refrigeration ends andcryogenics begins. Cryogenic temperatures are achieved either by the rapidevaporation of volatile liquids or by the expansion of gases confined initiallyat pressures of 150 to 200 atmospheres 10. Liquefied gases such as liquidnitrogen and liquid helium are used in many cryogenic applications. Liquidnitrogen is the most commonly used element in cryogenics and is legallypurchasable around the world. Liquid helium is also commonly used and allowsfor the lowest attainable temperatures to be reached.
These gases are held ineither special containers known as Dewar flasks which are generally about sixfeet tall (1.8 m) and three feet (91.5 cm) in diameter or giant tanks in largercommercial operations.2.
Experiment Details2.1. Fabricationof compositesThree different laminates with different carbon epoxy proportions arefabricated using hand layup technique. Carbon fiber was selected asreinforcement and epoxy as matrix material. Figure 2.
1. Preparing Mould Figure 2.2. Mould after curing Figure 2.3.
Specimen Cutting Figure2.4. Specimens after cutting2.
2. CryogenicTreatment (Liquid Nitrogen)Thecomposite specimens prepared of three different composition were immersed inliquid nitrogen tank. The specimens were inserted in liquid nitrogen tank for aduration of 24 hrs and 48 hrs. Figure2.5.
Specimens immersed in liquidnitrogen tank for 24 hrs and 48 hrs 2.3. Testingof Specimens2.3.1. Tensile Test Figure2.
6. Computerized Universal testing machine andDimensions of Tensile test specimen (mm) Ø Specimen is cut according to ASTM D-638 dimensions shown in figure 2.6Ø Specimen plate is enclosed between the grippers of universal testingmachine shown.Ø Load is applied by deforming the specimen and corresponding todeformation is noted down.Ø Stress strain for corresponding load and corresponding deformation arecalculated and repeated for different trials.2.
3.2. Flexure TestØ Specimen is cut according to ASTM D-790 dimensions shown in figure 2.7Ø Specimen plate is placed as simply supported beam of flexural testingmachine and a central load is applied as shownØ Load is slowly applied by deforming the specimen.
Ø Load at which maximum deformation is noted down and repeated fordifferent trials. Figure2.7.
Flexure testing machine and Flexure testing specimen (mm) 3. Results and DiscussionThe results and discussion consists of studying andanalyzing results of tensile strength and flexure strength of three differentcomposition of specimens at normal condition. It also consists of studying andanalyzing results of tensile strength and flexure strength of three differentcomposition of specimens when they are cryogenically treated for 24hrs and48hrs respectively.
3.1. TensileStrengthThe tensile strength obtained for all the different conditions anddifferent compositions discussed previously are as shown in table 3.
1 Table3.1: Results of tensile strength Sl No Specimen No / Composition Tensile Strength (Mpa) Normal 24 Hrs Treated 48 Hrs Treated 1 S1 / (70:30) 168 303 286 2 S2 / (60:40) 82.7 84.9 74.5 3 S3 / (50:50) 80 82.4 78.
2 Figure3.1. Results of tensile strength From the table 3.1 and figure 3.
1 it is observed that the 70:30specimen which was 24 hrs treated had more tensile strength when compared toother specimens. It was also observed that the tensile strength had increasedfor 24 hrs and then reduced for 48 hrs cryogenic treated specimens. For 60:40and 50:50 specimens the values reduced for 48 hrs treated specimens than thenormal values.
3.2. FlexureStrengthThe flexure strength obtained for all the different conditions anddifferent compositions discussed previously are as shown in table 3.2 Table3.
2: Results of flexure strength Sl No Specimen No / Composition Flexure Strength (Mpa) Normal 24 Hrs Treated 48 Hrs Treated 1 S1 / (70:30) 568 573 589 2 S2 / (60:40) 146 334 375 3 S3 / (50:50) 125 135 148 Figure3.2. Results of flexure strength From the table 3.
2 and figure 3.2 it is observed that the 70:30specimen which was 48 hrs treated had more flexure strength when compared toother specimens. It was also observed that the flexure strength had increasedfor 24 hrs and for 48 hrs cryogenic treated specimens.
The flexure strengthgradually increased for 24 hrs and 48 hrs treated specimens. 3.3. SEMAnalysis3.3.1.
Normal Specimens Figure3.3. SEM images of 70:30 composition – Normalspecimens Figure 3.3 shows the SEM analysis of normal specimens of 70:30composition.
From the figures we can see that the fiber layers are bondedcorrectly and the fracture is of brittle fracture nature. Figure3.4.
SEM images of 60:40 composition – Normal specimens Figure 3.4 shows the SEM analysis of normal specimens of 60:40composition. From the figures we can see that the fiber and epoxy bonding isnot as strong as the 70:30 composition and the fracture is of brittle fracturenature.
3.3.2. Cryogenic Treated – 24Hours Figure3.5.
SEM images of 70:30 composition – Cryogenictreated 24 hrs Figure 3.5 shows the SEM analysis of 24 hrs treated specimens of 70:30composition. From the figures we can see the adhesion between fiber and matrixdue to liquid nitrogen penetration and the fracture is of brittle fracturenature.
Figure3.6. SEM images of 60:40 composition – Cryogenictreated 24 hrs Figure 3.
6 shows the SEM analysis of 24 hrs treated specimens of 60:40composition. From the figures we can see the bonding between fiber and matrixdue to liquid nitrogen penetration and the fracture is of brittle fracturenature. The bonding is less when compared to 70:30 composition3.3.3. Cryogenic Treated – 48HoursFigure 3.
7 shows the SEM analysis of 48 hrs treated specimens of 70:30composition. From the figures we can see the bonding between fiber and matrixdue to liquid nitrogen penetration. The bonding or adhesion is more whencompared to 70:30 composition treated for 24 hrs. Figure3.7. SEM images of 70:30 composition – Cryogenictreated 48 hrs Figure3.
8. SEM images of 60:40 composition – Cryogenictreated 48 hrs Figure 3.8 shows the SEM analysis of 48 hrs treated specimens of 60:40composition. From the figures we can see the bonding or adhesion between fiberand matrix. The bonding is more when compared other specimens which weretreated for 24 hrs and 48 hrs.
This is due to more liquid nitrogen penetrationand the fiber content is less in this composition.4. ConclusionsFrom the results, discussion and analysisthe following conclusions are drawn.Ø Due to cryogenic treatment there waschanges in the physical properties of the specimens. The specimens had deformedin their shape. The more deformation was seen in 60:40 specimen which wastreated for 48 hrs.
Ø The tensile strength of the composites atcryogenic temperature has higher values than that normal temperature for 70:30specimen which was treated for 24hrs.The tensile strength for 60:40 and 50:50specimens which were treateated for 48 hrs had lesser values than the normalspecimens. This may be due to the deformation which had occurred.Ø The flexure strength of the composites atcryogenic temperature had higher values than the normal temperature for all thespecimens.
The flexure strength is more for 70:30 specimen which was treatedfor 48hrs.Ø The improvement in the strength valueafter cryogenic conditioning is probably due to differential thermalcontraction of the matrix during sudden cooling which leads to the developmentof greater cryogenic compressive stresses. Ø This may increase the resistance todebonding and better adhesion by mechanical keying factor at the interfacebetween fiber and the matrix.Ø The SEM analysis showed that the liquidnitrogen penetration along the fiber/matrix interfaces caused resistance todebonding and better adhesion.5. References1 Prashanth Banakar and H.
K. Shivananda,”Preparation and Characterization of the Carbon Fiber Reinforced Epoxy ResinComposites”, IOSR Journal of Mechanical and Civil Engineering (IOSRJMCE),ISSN: 2278-1684 Volume 1, Issue 2 (May-June 2012), PP 15-182 T D Jagannatha and G Harish, “Mechanicalproperties of carbon/glass Fiber reinforced epoxy hybrid polymer Composites”,Int. J. Mech. Eng.
& Rob. Res. 2015, Vol. 4, No. 2, April 20153 S.Pichi Reddy1, P.
V.Chandra SekharRao, A.Chennakesava Reddy,G.Parmeswari, “Tensile and flexuralstrength of glass fiber epoxy composites” International Conference onAdvanced Materials and manufacturing Technologies (AMMT) December 18-20, 2014.4 Amit Kumar Tanwer, “MechanicalProperties Testing of Uni-directional and Bi-directional Glass Fibre ReinforcedEpoxy BasedComposites”, International Journal of Research inAdvent Technology, Vol.2, No.
11, November 2014.5 Jane MariaFaulstich de Paiva, Sérgio Mayerc, Mirabel Cerqueira Rezende, “Comparison of Tensile Strength ofDifferent CarbonFabric Reinforced Epoxy Composites”, Materials Research, Vol. 9, No. 1,83-89, 2006.6 P. Baldissera andC. Delprete, “DeepCryogenic Treatment: A Bibliographic Review”, The Open Mechanical EngineeringJournal, 2008, 2, 1-11.7 Seyed Ebrahim Vahdat and Keyvan SeyediNiaki, “Design of metal matrix composite with particle reinforcementproduced by deep cryogenic treatment”, IOP Conf. Series: Materials Scienceand Engineering 87 (2015) 012003.8 Surendra Kumar M, Neeti Sharma and B.C. Ray, “Mechanical Behavior of Glass/Epoxy Composites at Liquid NitrogenTemperature”9 Blaise Solomon, Davis George, K.Shunmugesh, and Akhil K.T., “The Effectof Fibers Loading on the Mechanical Properties of Carbon Epoxy Composite” Polymers& Polymer Composites, Vol. 25, No. 3, 2017.10 Shangtan Liu, Xiaochun Wu, Lei Shi,Yiwen Wu and Wei Qu, “Influence ofCryogenic Treatment on Microstructure and Properties Improvement of Die Steel”,Journal of Materials Science and Chemical Engineering,2015, 3, 37-46.11 Jatinder Singh, Arun Kumar and Dr.Jagtar Singh, “Effect Of CryogenicTreatment On Metals & Alloys”.12COMPOSITE MATERIALS Web-based Course13Composite design Section 1 of 3: Composite design theory, AMTS standard workshoppractice14http://en.wikipedia.org/w/index.php?title=Carbon_ (fiber) &oldid=61426915315http://en.wikipedia.org/w/index.php?title=Epoxy&oldid=61316984116http://en.wikipedia.org/w/index.php?title=Carbon-fiberreinforced polymer &oldid = 61319814717K.Chawla, “Composite Materials”. Second Edition.18https://en.wikipedia.org/wiki/Strength_of_materials19https://ocw.mit.edu/courses/materials-science-and-engineering/3-11-mechanics-of-materials-fall-1999/20https://www.coursera.org/learn/mechanics-1