ANALYSIS OF EFFECT OF GEOMETRIC DISCONTINUITIES ON BUCKLING BEHAVIOUR OF EPOXY RESIN REINFORCED WITH CARBON FIBER AND SILICON CARBIDE

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1 ANALYSIS OF EFFECT OF GEOMETRIC DISCONTINUITIES ON BUCKLING BEHAVIOUR OF EPOXY RESIN REINFORCED WITH CARBON FIBER AND SILICON CARBIDE Mr.Sagar. G Department of Mechanical Engineering, PES College of Engineering Abstract - There have been numerous studies on the composite laminated structures which find many applications in many engineering fields namely aerospace [1], biomedical, civil, marine and mechanical engineering because of their ease of handling, good mechanical properties and low fabrication cost [2]. They also possess excellent damage tolerance and impact resistance. The mechanical behaviour of composite structures is of particular interest to engineers in modern technology. In aerospace and many other applications these structural components are also made up of composite material to further reduce the weight of the structure [3]. The outstanding mechanical properties of composite structures, such as durability and corrosion-resistance characteristics combined with low density, make it more attractive compared to conventional materials [4].There are few research work carried out on bucking analysis of a composite structure with geometric discontinuities. The objective of this project is to perform linear buckling analysis on laminated composite structure to analyze the effect of different geometric discontinuities on buckling behavior when subjected to in plane loading. Keywords - Buckling analysis, Finite element method, Buckling load per unit length, carbon/epoxy composite plate,ansys 15.0, Rule of mixture and Uniaxial load. I. INTRODUCTION Composite laminated structures find wide applications in engineering fields, such as aerospace, biomedical, civil, marine and mechanical engineering, because of their ease of handling and good mechanical properties [5]. They possess good impact resistance and damage tolerance despite of low weight and low fabrication cost. Only rectangular thin plates are considered in the present study. When a flat plate is subjected to low in-plane compressive loads, it remains flat and is in equilibrium condition [6]. As the magnitude of the in plane compressive load increases, the equilibrium configuration of the plate is eventually changed to a non-flat configuration and the plate becomes unstable. The magnitude of the compressive load at which the plate becomes unstable is called the Critical Buckling Load. Buckling is characterized by a sudden sideways failure of a structural member subjected to high compressive stress, where the compressive stress at the point of failure is less than the ultimate compressive stress that the material is capable of withstanding [7]. In other words, once a critical stress is reached, the component moves aside instead of taking up additional load. This failure can be analyzed using a technique well known as linear buckling analysis. The goal of this analysis is to determine the critical buckling load. II. NUMERICAL ANALYSIS This work is to find the critical buckling load of carbon/epoxy rectangular plate subjected to uniaxial compression using finite element analysis ANSYS 15.0 [8]. In order to find the critical buckling load, buckling load factor is found and it is multiplied by applied load. The analysis is done to the following cases having different percentages of silicon carbide (0%, 5%, 10%) DOI : /IJRTER FR21D 309

2 Case A: Analysis is done on the rectangular plate having no discontinuities. Case B: Analysis is done on the plate which has central circle of radius 28.21mm. Case C: Analysis is done on the plate which has central square of dimension 50 x 50 mm. III. ELEMENT DESCRIPTION SHELL181 is suitable for analyzing thin to moderately-thick shell structures shown in Fig 1. It is a fournode element with six degrees of freedom at each node: translations in the x, y, and z directions, and rotations about the x, y, and z-axes. (If the membrane option is used, the element has translational degrees of freedom only). The degenerate triangular option should only be used as filler elements in mesh generation. SHELL181 is well-suited for linear, large rotation, and/or large strain nonlinear applications [9]. SHELL181 can be used for layered applications for modeling composite shells or sandwich construction. The accuracy in modeling composite shells are governed by the first-order sheardeformation theory (usually referred to as Mindlin-Reissner shell theory) [10].The element formulation is based on logarithmic strain and true stress measures. Figure 1. SHELL 181 Element IV. GEOMETRIC MODELLING The length of the rectangular plate is 300mm width is 200mm and thickness is 3.5mm. The properties of the materials used for the analysis is given below Material Density (ρ) gm/cm 3 Modulus of Elasticity (E) GPa Poisson s ratio (μ) Carbon fiber Epoxy resin SiC Epoxy hardener (DY070) V. CALCULATION OF ENGINEERING PROPERTIES OF RAW MATERIALS Rule of mixture is used to calculate the engineering properties of the composites. The formulae to calculate the property is given below. A. For Density All Rights Reserved 310

3 ρ comp = ρ c V c + ρ E V E + ρ SiC V SiC + ρ H V H B. For Modulus of elasticity (E) E comp = E c V c + E E V E + E SiC V SiC + E H V H C. For Poisson s ratio (μ) μ comp = μ c V c + μ E V E + μ SiC V SiC + μ H V H VI. Calculation of volume percentage of materials in the specimen Vol. fraction of raw material is = Vol.of raw material Total volume of the composite VII. LAYER DEFINITION The composite laminate has 5 layers. The thickness of each layer is 0. 7mm and total thickness of laminated composites is 3.5mm. Lamina stacking sequence is [0/90/0/90/0]. A simulation model has been developed using ANSYS 15.0 APDL software. Buckling load factor is the ratio of buckling loads to the applied loads. Buckling load factor has been considered here since multiplying it with the applied load gives the buckling load. VIII. RESULT OF THE ANALYSIS The results which are obtained after performing the buckling analysis is shown. Analysis is carried for the various compressive loads (250, 500, 750 and 1000 N/mm). Also the analysis is carried for the various % of the SiC For the plate with 0% of SiC loaded With 250 N/mm Figure 2. Plate with 0% of SiC loaded With 250 N/mm. Buckling factor of is obtained which is multiplied by the applied load of 250N/mm. Hence the buckling load is obtained as N/mm For the plate with 0% of SiC having square hole loaded With 250 All Rights Reserved 311

4 Figure 3. Plate with 0% of SiC having square hole loaded With 250 N/mm. Result: Buckling factor of is obtained which is multiplied by the applied load of 250N/mm. Hence the buckling load is obtained as N/mm For the plate with 0% of SiC having circular hole loaded With 250 N/mm Figure 4. Plate with 0% of SiC having circular hole loaded With 250 N/mm Buckling factor of is obtained which is multiplied by the applied load of 250N/mm. Hence the buckling load is obtained as All Rights Reserved 312

5 Buckling Load (N/mm) International Journal of Recent Trends in Engineering & Research (IJRTER) Plate Loaded With 250 N/mm Geometry Rectangular plate Plate with square hole Plate with circular hole Figure 5. Graphical representation of results of a plate having 0%, 5% and 10% SiC loaded with 250 N/mm In the similar manner analysis is carried on the plate having different percentages of silicon carbide with varying compressive loads. Results obtained are verified as to check which has the highest buckling load and lowest buckling load. IX. CONCLUSIONS This study considers the buckling response of the rectangular plate which is fixed at one end and free at the other end. From the analysis the following conclusions can be made. Rectangular plate having 0% of SiC is having the maximum buckling load of N/mm and the plate with square hole has the lowest buckling load of N/mm. Rectangular plate having 5% of SiC is having the maximum buckling load of N/mm and the plate with square hole has the lowest buckling load of N/mm. Rectangular plate having 10% of SiC is having the maximum buckling load of /mm and the plate with square hole has the lowest buckling load of N/mm. By referring to the above results it can also be concluded that; The reduction of the buckling load due to the presence of the cut-out is found to be significant. It is noted that the presence of the cut-out lowers the buckling load and it varies with the cut-out shape. The plate with the square hole yields the lowest buckling load. The buckling strength can be increased by increasing the percentage of reinforcement of silicon carbide as its modulus of elasticity is more. X. SCOPE OF FUTURE WORK The present work is limited to 0%, 5% and 10% of silicon carbide; various percentages of the silicon carbide can be considered for analysis. The present work is limited to reinforcement with SiC. The work can be extended with other reinforcing material such as tungsten carbide to validate the results. The present work is limited to epoxy and unidirectional carbon fiber matrix. The work can be extended by considering glass fiber and validate the All Rights Reserved 313

6 Buckling analysis of laminated woven fiber composite plate with delamination by numerical approach by considering different boundary conditions can be done. Providing multiple notches & removal of material around the discontinuity is to be done. Study Post buckling behaviour of laminated composite material, for which a nonlinear analysis is to be performed. Experimental validation can be performed in order to validate the theoretical results. REFERENCES 1. Rekha Shakya, Tushar Sharma and Rajendra Bahadur., Effect of various cut-out on buckling analysis of laminated composite plate using FE simulation. ELK Asia Pacific Journals Special Issue ISBN: Tinh Quoc Bui., Buckling analysis of simply supported composite laminates subjected to an in-plane compression load by a novel mesh free method., Vietnam journal of mechanics, VAST, 33 (2011) Raguram.R., Buckling Behavior of Rectangular Plates With Different Central Cut-outs., International Journal of Computer & Organization Trends Volume 2 Issue 4 Number 1 Jul Michael P.Nemeth., Buckling and the post-buckling behavior of laminated composite plates with a cut-out., NASA technical paper Parth Bhavsar, Prof. Krunal Shah and Prof. Sankalp Bhatia., An overview of buckling analysis of single ply composite plate with cut-outs., International Journal of Engineering Research and General Science Volume 2, Issue 5, August- September, 2014 ISSN Gokmen Athhan., Buckling analysis of delaminated composite beams. Indian Journal of Engineering & Materials Sciences 20 (2013) Hossein Rahmani, S.Heydar Mahmoudi Najafi, Alizera Ashori and Mahdi Golriz., Elastic properties of carbon fiberreinforced epoxy composites. 8. Mert Muameleci., Linear and Nonlinear Buckling Analyses of Plates using the Finite Element Method., Vietnam journal of mechanics, VAST, 33 (2014) Mohammed Gouse1, Ravi kumbar, T. Madhusudhan., Buckling behavior of composite plates., International Journal of Engineering Research and General Science Volume 3, Issue 2, Part 2, March-April, 2015 ISSN Patrick E., FEA buckling analysis of stiffed plates with filleted junctions & 2012 Elsevier Ltd. 11. M Mohan Kumar, Colins V Jacob, Lakshminarayana N, Puneeth BM, M Nagabhushana., 12. Buckling Analysis of Woven Glass Epoxy Laminated Composite Plate., American Journal of Engineering Research (AJER) e-issn : p-issn : Volume-02, Issue-07, pp P. Ravinder Reddy, P. Surendar Reddy, P.Shashikanth Reddy., Buckling Analysis of Orthotropic Laminated Composite Plate With Rectangular Cut-Outs By Using FEA., International Journal of Emerging Technologies in Computational and Applied Sciences (IJETCAS) I Volume 2, Issue 2, Part 3, March-April, 2012 ISSN Rase, Howard F. (2000). Handbook of commercial catalysts: heterogeneous catalysts. CRC Press. p ISBN All Rights Reserved 314