NUMERICAL INVESTIGATION OF FRP LAMINATE SUBJECTED TO THERMAL BUCKLING USING FEM

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 9, Issue 11, November2018, pp , Article ID: IJMET_09_11_241 Available online at ISSN Print: andISSN Online: IAEME Publication Scopus Indexed NUMERICAL INVESTIGATION OF FRP LAMINATE SUBJECTED TO THERMAL BUCKLING USING FEM M. Rajinikannan, S. Jaiganesh, R. Kuppuchamy, R. Muthumeenakshi PSNA College of Engineering and Technology, Dindigul, Tamilnadu, India C. Dharmaraj Anna University, University College of Engineering, Dindigul, Tamilnadu, India ABSTRACT In this research work it deals with the effect of temperature for a thin FRP laminate composite subjected to uniformly distributed thermal load sat which the failure occurs in buckling mode and also the effects of geometrical parameter such asi) In-plane aspect ratio, and material parameters ii) Fiber orientation, iii) Fiber stacking sequence on failure temperature is studied. Thermal stresses in composite structures are usually known as a destructive phenomenon which should be avoided or compensated. The problem is modeled in commercial FEA software ANSYS. Key Words: Thin Laminate; FRP; FEM; Thermal Buckling Cite this Article: M. Rajinikannan, S. Jaiganesh, R. Kuppuchamy, R. Muthumeenakshi, C. Dharmaraj, Numerical Investigation of FRP Laminate Subjected to Thermal Buckling using FEM, International Journal of Mechanical Engineering and Technology (IJMET), 9(11), 2018, pp INTRODUCTION Study of thermo-mechanical response is necessary for the design of structures working under static and thermal environments. Most of the structures in space applications are made of FRP composites and thin to reduce the weight. Thin structures are usually weak in buckling. Therefore it is required to check the buckling strength of a structure before finalizing the designs. Though approximate, analytical way of research reduces cost and design time, and is a powerful tool to grade the structures based on parametric studies. Contributions of various authors in this area are presented in the following section. The use of the structural members made of laminated composite and sandwich materials has been increased significantly due to their merits such as low density, high stiffness and high strengths. Composite structures, which are being widely used in engineering applications like aerospace industry, are often under thermal loads. Thermal loads usually bring thermal stresses in the structure which can significantly affect its static and dynamic behavior [1-10]. When the editor@iaeme.com

2 Numerical Investigation of FRP Laminate Subjected to Thermal Buckling using FEM thermal stresses increase to a certain level, the structure may lose its elastic stability, and thermal buckling occurs Review of Literature Khaled and Aly [1] have studied the effect of aspect ratio on elastic buckling load of uniaxially loaded rectangular plates of simply supported in the out- of- the plane direction. Correia et al [2, 3] investigated experimental buckling and post-buckling characteristics of GFRP beams and compared with finite element analyses. Jifeng et al [4] reviewed various analytical and numerical methods used for prediction of buckling and post buckling of composite structures. Manoj Kumar [5] investigated vibration and buckling behavior of laminated composite plates subjected to varying temperature and moisture concentration. Lee et al [6] studied bucking behaviors of WBK (Wire-woven Bulk Kagome) cored sandwiches under longitudinal compression. Sreenivasa Rao et al [7] analyzed buckling of a thin FRP laminate under temperature load Problem Statement The objective of the present work is to identify the mode of failure, i.e. static or buckling, of a thin FRP rectangular plate with different stacking sequences, subjected to uniform thermal load on all over the plate with two transverse edges fixed using 2-D finite element analysis. The scope of the work includes study of the effect of (i) aspect ratio (a/b) and (ii) effect of fiber orientation. 2. PROBLEM MODELLING An FRP composite thin rectangular plate of in-plane dimensions: length a=2m and width b=1m (Fig. 1) is considered for the present analysis. The thickness of the plate is taken as 20mm.Laminates with eight number of layers of uniform thickness and with different orientationsi) Symmetric Cross-ply (0/90/90/0/0/90/90/0), ii) Symmetric Angle-ply (θ/-θ/- θ/θ/θ/-θ/-θ/θ),θ varied as0,15,30,45,60,75,90, and iii) Symmetric quasi isotropic (90/45/- 45/0/0/- 45/45/90) are analyzed. Modelling includes construction of required geometry, defining element type, real constants, assigning material properties, generation of finite element mesh, imposing constraints and application of loads. In this study, shell 99 of ANSYS software [8]is selected as the element type which is suitable for analyzing thin to moderately thick structures and well suited for layered composites. Clamped boundary condition is given for two sides of dimension b (Fig. 1) Figure 1 Geometry and meshed model of laminate with a/b= editor@iaeme.com

3 M. Rajinikannan, S. Jaiganesh, R. Kuppuchamy, R. Muthumeenakshi, C. Dharmaraj 2.1. Material Properties The following material properties are considered for the present analysis [9]. i) Young s Modulus: E1=147GPa, E2= E3 =10.3GPa ii) Poisson s Ratio:ν12=ν13=0.27, ν23= 0.54 iii) Rigidity Modulus: G12 = G13=7GPa, G23=3.7GPa iv) Coefficient of thermal expansion: α1 = -0.9e-6/0C, α2 =α3 =27e-6/0C v) Longitudinal tensile strength: F1t=2280MPa; Transverse tensile strength: F2t=57MPa vi) Longitudinal compressive strength: F1c=1725MPa; Transverse compressive strength: F2c=228MPa vii) In-plane shear strength, F6=76MPa 3. ANALYSIS OF RESULTS Temperatures corresponding to static failure and for first five buckling modes are evaluated. Fig. 2 shows the mode shapes and static failure index of an eight layered symmetric cross-ply square laminate with a/b=2 Figure 2 Buckling modes and static failure index of the plate 3.1. Effect of Aspect Ratio Tables 2-4 show the variation of buckling and static failure temperatures with respect to a/b for the three types of laminates considered. It can be observed that the buckling strength increases with decrease in a/b ratio. This is due to the reason that increases in length of laminate (a)decreases the plate resistance towards buckling. From the Table 2, it can be observed that up to the value of a/b=1.25, failure occurs due to buckling. Beyond this value, the laminate fails due to compression. In case of quasi isotropic laminate for all the values of a/b considered, failure is noticed due to buckling only (Table 3). This is due to the less number of longitudinal fibers in the laminate when compared to previous case. In case of angle-ply laminate with 450 layers, buckling occurs up to a/b=1.5, beyond which the failure mode turns to compression (Table 4) editor@iaeme.com

4 Numerical Investigation of FRP Laminate Subjected to Thermal Buckling using FEM 3.2. Effect of Fiber Angle Table 5 shows the variation of buckling and static failure temperatures with respect to θ for symmetric angle-ply laminates considered. It can be observed that the buckling strength is maximum at θ =300.Later there is a continuous decrease in buckling strength. This is due to the resultant effect of thermal expansion and Young s modulus of the laminate in a particulardirection due to change in fiber orientations. It is also observed that the failure mode shifts from compression to buckling for θ >30 0. Fig. 3 shows the variation of temperature corresponding to failure in buckling and compression with respect to a/b ratio for cross-ply laminate. Static failure temperature is not varying with respect to a/b ratio. For the value of a/b up to 1.2, the laminate fails in static mode and later in buckling mode editor@iaeme.com

5 M. Rajinikannan, S. Jaiganesh, R. Kuppuchamy, R. Muthumeenakshi, C. Dharmaraj Figure 3 Effect of Aspect Ratio (For a=2m, b=1m and for the stacking sequence (0/90/90/0/0/90/90/0) for 1st Mode) Fig. 4 shows the variation of temperature corresponding to failure in buckling and compression with respect to a/b ratio in case of a symmetric angle-ply laminate at θ=450. For the value of a/b up to 1.4, the laminate fails in static mode and later in buckling mode. Figure 4 Effect of fiber angle (For a=2m, b=1m and s=100 for the stacking sequence (θ/-θ/-θ/θ/θ/-θ/- θ/θ) for 1st Mode) 4. CONCLUSIONS Two dimensional finite element analysis is performed to predict the failure mode in terms of temperature withstanding capacity in direct compression and buckling of a thin FRP composite laminate when exposed to heat. Three different configurations are chosen for layup and the effect of in-plane aspect ratio and fiber orientation on buckling and compression failure loads is studied. Following conclusions are drawn. Aspect ratio should be 1 for better buckling resistance. There is no significant effect of aspect ratio on static failure. Fiber angle should be 300for high buckling strength in case of symmetric angle-ply laminates. Failure mode shifts from compression to buckling for θ >300in case of angle-ply laminates with a/b= editor@iaeme.com

6 Numerical Investigation of FRP Laminate Subjected to Thermal Buckling using FEM For the value of a/b up to 1.2, the laminate fails in static mode and later in buckling mode for cross-ply laminates. For the value of a/b up to 1.4, the laminate fails in static mode and later in buckling mode for angle-ply laminates at θ=450. REFERENCES [1] M. Khaled EI- Sawy and Aly S. Nazmy, Thin-Wall Structures 39 (2001) [2] J.R.Correia, F.A. Branco, N.M.F. Silva, D. Camotim, N. Silvestre, Computers & Structures 89 (2011) [3] N.M.F. Silva, D. Camotim,, N. Silvestre, J.R. Correia, F.A. Branco, Composites & Structures, 89 (2011) [4] JifengXu, Qun Zhao, PizhongQiao, Frontiers in Aerospace Engineering 2 (2013) [5] R. Manoj Kumar, Advanced Materials Manufacturing & Characterization 4 (2014) [6] M.G.Lee, J.W. Yoon, S.M. Han, Y.S. Suh, K.J. Kang, Procedia Materials Science, 4 (2014) [7] B. SreenivasaRao, G. SambasivaRao and J. Suresh Kumar, Materials Today: Proceedings 2 (2015) [8] ANSYS Reference Manuals [9] Isaac M.D. and Orilshai, Engineering Mechanics of Composite Materials, Oxford University Press, [10] rmal_buckling.pdf editor@iaeme.com