Address for Correspondence 1,2 Department of Mechanical Engineering R.I.T. Islampur , Maharashtra India.

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1 ABSTRACT Jadhav, et al., International Journal of Advanced Engineering Technology E-ISSN Research Paper FEM& EXPERIMENTAL ANALYSIS OF COMPOSITE LAMINATE WITH ELLIPTICAL CUT OUT USING REFLECTION POLARISCOPE *Sangram S. Jadhav 1, Prof. Durgeshkumar S. Chavan 2 Address for Correspondence 1,2 Department of Mechanical Engineering R.I.T. Islampur , Maharashtra India. Composite materials are widely used in various applications such as automobile industries, aircraft, marine etc. Composites are made up of individual materials referred to as constituent materials. The constituents are combined on a macroscopic scale and are insoluble to each other. Generally, a composite material is composed of reinforcement (fibers, particles, flakes, and/or fillers) embedded in a matrix (polymers, metals, or ceramics). The matrix holds the reinforcement to form the desired shape while the reinforcement improves the overall mechanical properties of the matrix. When designed properly, the new combined material exhibits better strength than that of each individual material. Composites offer several other advantages over conventional materials. These include improved strength, stiffness, fatigue and impact resistance, thermal conductivity, corrosion resistance, etc. In this paper the work is carried out on carbon FRC laminate with elliptical cut out by varying major minor axis dimensions for stress analysis using reflection polariscope as a photoelasticity technique. 1. INTRODUCTION In the last two decades, the use of fiber reinforced materials has become widespread not only because of their high strength-to-weight ratio but also the possibility of tailoring them to meet specific design requirements by selecting the fiber materials and their orientation. A fiber-reinforced composite (FRC) consists of three components, the fibers as the discontinuous or dispersed phase, the matrix as the continuous phase, and the fine interphone region, also known as the interface. A lamina, also called a ply or layer is a single flat layer of unidirectional fibers or woven fibers arranged in a matrix. A laminate is a stack of plies of composites. Each layer can be laid at various orientations and can be of different material systems. Considering its light weight, a lamina (ply) of fiber reinforced composite is remarkably strong along the fiber direction. However, the same lamina is considerably weaker in all off-fiber directions. To address this issue especially in terms of withstanding loadings from multiple angles, one would use a laminate constructed by a number of lamina oriented at different directions. When each layer is oriented in a different direction, it gives different strength and stiffness in various directions as a whole. The cut outs are often required for ventilation aesthetic or design requirements such as square rectangular elliptical etc. the stress concentration is more in case of square or rectangular cut out rather than elliptical so to minimize the stress in laminate the elliptical cut out is selected. 2. Basic terms of composite:- 2.1 LAMINA- A lamina or a ply is formed by a combination of a large number of fibers in a thin layer of matrix. Fiber in the lamina may be continuous or discontinuous, arranged in specific direction or in a random orientation. A unidirectional lamina is one where the fibers in a lamina run parallel to one another in particular direction. It is natural that discrete fiber composite will have lower strength and modulus than continuous fiber composites. However, with the random orientation of the fiber, it is possible to obtain nearly equal mechanical and physical properties in all direction in the plane of the lamina. Two typical flat laminae along with their principal material axes that are parallel and perpendicular to the fiber direction are shown in figure 2.1 Figure Two principal types of laminae 2.2 LAMINATE- A laminate is formed by stacking several laminas. It is the most common form of fiber reinforced composite. It is made of desired thickness so as to enable it to support a given load and maintain a given deflection. Fiber orientation of each lamina and stacking sequence of various layers can obtain a wide of physical and mechanical properties of composites. Figure 2.2 shows a laminate in which the fiber orientation of the layers is symmetric about the middle surface of the laminate.

2 Figure 2.2-unbonded view of laminate construction The layers of a laminate are usually bonded together by the same matrix material that is used in the individual laminae. That is, some of the matrix material in a lamina coats the surfaces of a lamina and is used to bond the lamina to its adjacent laminae without the addition of more matrix material. A major purpose of lamination is to tailor the directional dependence of strength and stiffness of a composite material to match the loading environment of the structural element. Laminates are uniquely suited to this objective because the principal material directions of each later can be oriented according to need. For example, six layers of a ten layer laminate could be oriented in one direction and the other four at 90 to that direction: the resulting laminate then has a strength and extensional stiffness roughly 50% higher in one direction than the other. 2. PROPERTIES OF CARBON-EPOXY COMPOSITE 3.3 Result For [0 2 /±45/90] s with major axis=25mm & minor axis=15mm 3.4 Graphical Representation of Stain with Elliptical Cut out. For the analysis of FRC laminate the stacking sequence is selected as C/C/C/C where C-carbon fiber. The orientation of the fiber is [0 2 /±45/90] s 3. FEM ANALYIS Finite Element Analysis (FEA) is a computer-based numerical technique for calculating the strength and behavior of engineering structures. It can be used to calculate deflection, S/D/F, vibration, buckling behavior and many other phenomena. It also can be used to analyze either small or large-scale deflection under loading or applied displacement. It uses a numerical technique called the finite element method (FEM). The following element types are available to model layered composite materials: SHELL 99, SHELL181, SHELL281, SOLSH190, SOLID185 Layered Solid, and SOLID186 Layered Solid.

3 4. EXPERIMENTAL ANALYSIS The reflection polariscope is used for experimental method to find stress distribution in a material. The method is mostly used in cases where mathematical methods become quite cumbersome. Unlike the analytical methods of stress determination, photo elasticity gives a fairly accurate picture of stress distribution, even around abrupt discontinuities in a material. The method is an important tool for determining critical stress points in a material, and is used for determining stress concentration in irregular geometries. The various parts of the reflection polariscope are- Polariscope head Polariscope light source Light source Power supply Laser light source Polariscope and video camera mounting plate Electronic compensator. Video camera. (Remote control, Mounting hardware, Power supply). Test specimen. Heavy duty tripod. 3. The cured coating is pasted to the specimen by using silver cement adhesive. Then specimen is keep for 18-22hrs for firmly attachment of coating to specimen. 4. Once the coating is firmly attached to specimen then it is ready for further analysis Fig 4.2 coating material Fig 4.3 bonded specimen with coating Fig 4.1 reflection polariscope Reflection polariscope works on the photoelasticity principle i.e. when the light is passing through polarizer (which converts ordinary light into plane polarizes light or circularly polarized light) & reflects from coated surface of specimen and observed through analyzer. The generation of various fringes observed in analyzer. 4.1Procedure for reflection polariscope 1. For the analysis of the specimen the reflective coating is applied to the specimen is necessary to reflect the light from specimen surface. 2. The coating is made up from resin & hardener which mixed & poured on casting plate, cure for 1.30hr take the sheet in semi cured state, cut the required size and put it for complete cure. Approximately it requires 24hr to cure. Fig 4.4 Experimental set up 5. Specimen is loading on the UTM for compressive load is applied. as the load is increases the fringe pattern is observed through analyzer 6. By passing the black fringe through point of interest taken on the specimen the compensator show the fringe order reading. 7. This compensator reading is put in the following equations which give the values for stress & strain. For the principal stress and strain measurement the following equations are used σ 1 - σ 2 = E/(1+µ) (R 1 -R 0 ) f ε (1) ε 1 ε 2 = (R 1 -R 0 ) f ε (2) f ε =287.5/(t k) Where, σ 1 - σ 2 = principal stress difference E = modulus of elasticity (N/mm 2 )] ε 1 ε 2 = principal strain difference

4 µ = poisons ratio R1 = final compensator reading R 0 = initial compensator reading f ε = calibration value for coating material t = thickness of coating k = strain optic coefficient( ) 4.2 Experimental values. 4.3 Comparison of result The comparison of stress & strains for [0 2 ±45/90] s with major axis=25mm & minor axis=15mm as follows. 1. Stress 2. Strain Fig 4.5 compensator reading 4.3 Fringe pattern observed from no load to300kg 5. CONCLUSION In this paper the analysis is carried out on the FRC laminate. For this laminate the variation in the elliptical cut out dimensions of major & minor axes were taken. The values observed from experimentally and using ANSYS are shown in the graph. From the result it is conclude that the when the dimensions of elliptical cut out when minor axes kept constant & variation of major axes gives minimum stress & strains in FRC laminate. In this analysis for the orientation [0 2 ±45/90] s And elliptical dimensions major axis=25mm & minor axis=15mm gives minimum stress & strains in laminate. REFERENCES 1. Manoharan R. and Jeevanantham A. K stress and load-displacement analysis of fiber reinforced composite laminates with a circular hole under compressive load,aprn journal of engineering &sciences vol.6,no.4(64-74). 2. Robin Olsson, Jonas Iwarsson Experiments and analysis of laminates with artificial damage. Composites science and technology. 63:

5 3. Hakim S. Sultan Aljibori, W.P. Chong Load displacement behaviour of glass fiber/epoxy composite plates with circular cut-outs subjected to compressive load. Materials and design. 31: Takeda T, Takano S, Shindo Y, Narita F Deformation and progressive failure behaviour of woven fabric reinforced glass/epoxy composite laminates under tensile loading at cryogenic temperatures. J. Compos Sci Technol. 65: Wu Zhen, Chen Wanji Stress analysis of laminated composite plates with a circular hole according to a single-layer higher-order model. Composite Structures. 90: S.A.M. Ghannadpour, A. Najafi On the buckling behaviour of cross-ply laminated composites plates due to circular /elliptical cut-outs. Composite structures. 75: Damodar R. Ambur, Navin Jaunky, Mark Hilburger, Carlos G. D_avila Progressive failure analyses of compression-loaded composite curved panels with and without cut-outs Composite Structures 65 (2004) M. Saha, R. Prabhakaran, W.A. Waters Jr. Compressive behaviour of pultruded composite plates with circular holes Composite Structures 65 (2004) D.K. Nageswara Rao, M. Ramesh Babu, K. Raja Narender Reddy, D. Sunil Stress around square and rectangular cut-outs in symmetric laminates. Composite Structures 92 (2010) Toshio Nakamura, Li-Chun WuE effects of ply-arrangement on compressive failure of layered structures Vishay precision group LFZ reflection polariscope