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  1. 1. Ramanatha Dash, F.Anand Raju / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.2044-2048 Buckling Behaviour Of Compression Loaded Composite Cylindrical Shells With Reinforced Cutouts Ramanatha Dash *, F.Anand Raju ** * PG Student, CAD/CAM, Siddharth Institute of Engineering & Technology (SIETK), Puttur - 517583 ** Department of Mechanical Engineering, SIETK College, Puttur, Chittoor Dist, Andhra Pradesh, INDIA.ABSTRACT In the recent times, Composite thin concentrations that can cause local buckling orcylindrical shells are most widely used structural premature material failures. In addition it isforms in Aerospace and Missile applications. In important to understand performance enhancementsdesigning efficient and optimized shell structure, that can be obtained by using light weight fibre-they become increasingly sensitive to buckling. It reinforced composite materials. Fuethermore theseis well known that the experimental display is structures experience compression loads duringmainly attributed to geometrical imperfection vehicle operation and as a result, their bucklinglike damage in the structure, or ovality or local response and material failure characteristics must bethining of material etc. in missile and Airframe , understood and accurately predicted in order tothe composite cylindrical shell structure is devlop efficient,safe design.generally provided with cutouts for accessinginternal components during integration. The Many numerical and experimental studiescutouts invariably reduce the strength of the of the buckling behaviour of cylindrical shells havecomposite cylindrical shell and more specifically been conducted since the early 1900s.It took nearlythe buckling load. It has been a design practice to 100 years to reach the point whereimprove strength by addition of reinforcement robust,measurement technologies were available thataround cutouts. The cutout not only introduces could be used to conduct test-analysis correlationsstress concentration but also significantly reduce that include the effect of initial geometric,material,buckling load. Which will results to eliminate the and manufacturing perfections and the effect of loadInterlaminar and intralaminar failure by change introduction and support addition ,thein material properties through dimensional use of advanced composite materials allows thecomputational analysis was carried out using designer to tailor the stiffness properties of theANSYS as the preprocessing software and FE as structure to obtain a structurally efficient design.the solver and post processor. Thin walled cylindrical shells are found in many aerospace structural applications because of theirKeywords: Acoustic, reinforcement, FEA high load carrying capacity and low structural weight.Many of these aerospace shell structures1. INTRODUCTION: have cutouts or openings that serve as The composite is a combination of two or doors,windows, or access ports and thesr cutouts ormore materials combine on a microscopic scale to openings often require some type of reinforcinggive superior properties than original materials structure to control local structural deformations andinclude strength,fatigue life, stiffness ,temperature stress near the cutout.many studies have beendependent behaviour,corrosion resistance,thermal conducted which shows that a cutout in an isotropicinsulation,wear resistance,thermal shell structure can have a significant effect on theconductivity,attractiveness,acoustical insulation and response of the shell.Towards this objectives,weight. The composites find its application in numerically predicted results that shows the effect ofAerospace,Defence,Automobiles,Machine tool, change in material properties of graphite/EpoxyMarine, Construction industry,chemical industry and composite shell with reinforcement configuration onbiomedical equipments etc. In general structural the response of these shell structures are presented.discontiuities in the form of cutouts are inevitable in Results include the variation of Buckling factor,the design and construction particularly in the Deformation, Interlaminar shear stresses change inAerospace industry.Thin-walled shell structures are Et/El, Gxy/El, and Gyz/El.a fundamental component found in Initially straight, then the direction ofAircraft,spacecraft, and launch vehicles. In most buckling will be very sensitive to any lateral forceapplications,these structural components contain applied to the middle of the card. If you push gentlycutouts or openings that serve as doors,windows, or to the left on the middle of the card and then squeezeaccess ports, or used to reduce weight.often some it, it will buckle to the left. If you push gently to thetype of reinforcement is used around a cutout to right and then squeeze, it will buckle to the right.eliminate local deformations and stress Once the card has begun to buckle in one direction it 2044 | P a g e
  2. 2. Ramanatha Dash, F.Anand Raju / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.2044-2048is difficult to force it in the other direction. In short, 2D-DRAWINGSa small lateral force applied to the card as an "input Fig 1, Fig 2 , Fig 3 & fig 4 shown below thesignal" can control the direction of the large lateral finite element model of a composite shell withdisplacement produced as an "output signal" when centrally located square cutouts dimensions of athe card is buckled by a force applied from the top as 1*1mm.a "clock signal"2.BUCKLING OF CYLINDRICAL SHELL: This buckling arrangement can be used todefine logic operations. If one or more input forcesare applied laterally to the midsection of the shell,then the midsection will be pushed either somewhatto the left or somewhat to the right, depending on thesum of the applied forces. When the large clockingforce is applied, the initial direction of deformationwill be continued, and with greater force. This canbe viewed as a threshold device, for the output stateis controlled by the sum of the input forces. Oncebuckled in one direction or the other, the shell willremain in that state and will be resistant to a changeto the other stable state (in which it is buckled in the Fig1:.Front view of composite shellother direction). The cylindrical shell is uniformly Fig2: Composite shell with holecompressed in the axial directions,bucklingsymmetrical with respect to the axis of cylinder. Thecritical value of compressive force Ncr per unitlength of the edge of the shell can be obtained byusing the energy method.2.1 FINITE ELEMENT MODEL: Fig3.Composite shell with reinforced holeFig. shows the structural analysis of shells. 2045 | P a g e
  3. 3. Ramanatha Dash, F.Anand Raju / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.2044-2048 Fig4.Top view of composite shell2.2 DIMENSIONS OF A MODEL: Length of the shell =16 mm Fig Shell99 element geometry Radius of the shell =8mm Xij = Element x-axis if ESYS is applied. Thickness of shell =0.04mm X=Element x-axis if ESYS is supplied. No. of plies =8 LN= layer Number Dimension of cutout =1mm*1mm NL=Total number of Layers.3. BOUNDARY CONDITIONS: 4.0 MESHING: The one end of the shell constrained all The results are studied to understand theDegree of freedom( Bottom ) and other end of the influence of cutouts on buckling strength of shell ofshell is applied compressive load of 2000N(Top). same material and also the extent of improvement by providing reinforcement around cutouts.3.1 SPECIFY MATERIAL PROPERTIES: (GRAPHITE/EPOXY) 4.1 WITHOUT REINFORCEMENT Longitudinal modulus,El = Composite shell without hole Composite shell with127.46Gpa one hole Transverse modulus, Et = 11.3Gpa In-plane shear modulus,Gxy = 6Gpa In-plane shear modulus,Gyz = 3.514Gpa Major Possions ratio,v =0.303.2 SHELL99 ELEMENT DESCRIPTION: SHELL99 may be used for layeredapplications of a structural shell model. WhileSHELL99 does not havsome of the nonlinearcapabilities of SHELL91, it usually has a smallerelement formulation time. SHELL99 allows up to250 layers. If more than 250 layers are required, auser-input constitutive matrix is available. The element has six degrees of freedom ateach node: translations in the nodal x, y, and zdirections and rotations about the nodal x, y, and z-axes. 2046 | P a g e
  4. 4. Ramanatha Dash, F.Anand Raju / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.2044-2048 Composite shell with reinforcement of one, twoComposite with two holes Composite shell with holes respectivelyfour holes 4. RESULTS: CHANGE IN RATIO OF ET/EL TABLES Without With With Et/El hole 1hole 2holes with4holes 0.02 7.181 7.186 7.287 7.212 0.04 7.298 7.302 7.398 7.325 0.06 7.413 7.416 7.508 7.437 0.08 7.575 7.578 7.664 7.595 0.10 7.639 7.641 7.725 7.657 Table4.1 Variation of buckling factor with change in ratio of Et/ElDeformation without hole Deformation with oneholeFig shows the interlaminar shear stress of shell with 7.8one hole, the max, min interlaminar shear stress is 7.714.625,-9.208MPa respectively. maximum 7.6interlaminar shear stress is observed at free edge of 7.5the hole of composite shell. 7.4 7.3 7.2 7.1 7 6.9 0.02 0.04 0.06 0.08 0.1 Buckling factor Vs Change in ratio of Et/ElInterlaminar shear stress of without hole, with onehole4.2 WITH REINFORCEMENT OFCOMPOSITE SHELL Deformation Vs Change in ratio of Gxy/El 6. CONCLUSION: Results from a numerical study of the response of thin-wallcompression-loaded laminated composite cylindrical shells with reinforced and unreinforced square cutouts have been presented. The results identify some of the effects of cutout-reinforcement, size, and 2047 | P a g e
  5. 5. Ramanatha Dash, F.Anand Raju / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.2044-2048thickness on the linear response of the shells. The composite Materials and Structures”subspace algorithm is used to determine buckling 8. Hilburger, M. W., Britt, V. O., andfactor, under buckling load the interlaminar shear Nemeth, M. P., “Buckling Behavior ofstress obtained from ANSYS releace-10 FEA Compression-Loaded Quasi-Isotropicsoftware. In general, the addition of Curved Panels with a Circular Cutout,"reinforcement around a cutout in a compression- International Journal of Solids andloaded shell can have a significant effect on the Structures, Vol. 38, 2001, pp. response. Results have been presented 9. Hashin Z. Failure criteria for unidirectionalindicate that the reinforcement can affect the fibre composites. J Appl Mech 1980; 47:local deformations and stresses near the 329–34cutout and retard or suppress the onset of 10. Almroth, B. O. and Holmes, A. M. C.,local buckling in the shell near the cutout. "Buckling of Shells with Cutouts, 1. The maximum interlaminar shear stress is Experiment and Analysis," International observed at bottom of shell without cutout. Journal of Solids and Structures, Vol. 8, 2. The maximum interlaminar shear stress is 1972, pp. 1057-1071. observed at free edge of cutout in case of without reinforcement. AUTHORS BIOGRAPHY: 3. The maximum interlaminar shear stress is observed at away from cutout of shell with RAMANTHA DASH was born in reinforcement. India,Orissa in 1975. He received his 4. Interlaminar failures are reduced by AMIE(Mechanical) The Institution of increasing the Gxy/El as compared with Engineers,India increasing the Gyz/El and Et/El. from June 2001 to till date working 5. Deformations are greatly reduced by adding as a Production Engineer in GODREJ AGROVET reinforcement. LTD, Present he is doing M.Tech (CAD/CAM)from Critical loading also increased considerably by SIETK College, Affliated from JNTUA Ananthapur,adding reinforcement PUTTUR , Chittoor DIST, Andhra Pradesh. His research areas are Modelling &Analysing onREFERENCES composite materials. 1. Lure, A. I., “Statics of Thin-walled Elastic Shells, State Publishing House F.ANAND RAJU was born in of Technical and Theoretical Literature, India,A.P in 1976. He received his Moscow, 1947; translation, AEC-tr-3798, Diploma in GMR Polytechnic Atomic Energy Commission, 1959. college,srisailam on September 2. Lekkerkerker, J. G., “On the Stress 1995,He completed his Distribution in Cylindrical Shells B.Tech(Mechanical) in 2000 from Weakened by a Circular Hole, SVU college of Engineering,Tirupati in Ph.D. Dissertation, Technological May2002.He did M.Tech (Production Engineering) University, Delft, The Netherlands, 1965. from S.V University,tirupati in 2002.He having 10 3. Brogan, F. A. and Almroth, B. O., years Teaching Experience,At Present he is working “Buckling of Cylinders with Cutouts, as a HOD of Mechanical Engineering in SIETK AIAA Journal, Vol. 8, No. 2, February College,Puttur,Chittoor Dist,A.P,India 1970, pp. 236-240. 4. Tennyson, R. C., “The Effects of Unreinforced Circular Cutouts on the Buckling of Circular Cylindrical Shells, Journal of Engineering for Industry, Transactions of the American Society of Mechanical Engineers, Vol. 90, November 1968, pp. 541-546. 5. Starnes, J. H., “The Effect of a Circular Hole on the Buckling of Cylindrical Shells, Ph. D. Dissertation, California Institute of Technology, Pasadena, CA, 1970. 6. Cervantes, J. A. and Palazotto, A. N., "Cutout Reinforcement of Stiffened Cylindrical Shells," Journal of Aircraft, Vol. 16, March 1979, pp. 203-208. 7 Madhujit Mukhopadhyay “Mechanics of 2048 | P a g e