IJSART - Volume 3 Issue 8 –AUGUST 2017 ISSN [ONLINE]: 2395-1052 Page | 7 www.ijsart.com Stiffness Optimization of Composite Laminate Yogesh Shilote 1 , Prof. N.S. Kulkarni 2 1 Post Graduate Student 2 Asst. Professor Mechanical Engg. Dept 1, 2 VIT Pune Abstract- In this study, Stiffness of composite laminate is maximized by minimizing the displacement of a laminate. Laminates taken for this study have symmetricity about middle ply. Three different laminates having different thickness have considered for analysis. Laminate with constant ply thickness is used for thickness maximization while ply angles in discrete form are considered as design variables. It is observed that for given ply thickness maximum stiffness can be achieved by varying the ply orientation. In this study, optimization is carried out using genetic algorithm available in Hyperstudy. These FEA results are verified by experimental means and FEA model is validated. The validated FEA model is then utilized for Bi-axial load conditions and maximum stiffness is obtained and validated with published results. Keywords- Symmetric Composite Laminate, Stiffness, Optimization, Genetic algorithm I. INTRODUCTION Composite material is the combination of two or more materials at macroscopic level which are insoluble into each other. It consists of matrix and reinforcements in form of fibers. The fibers can be oriented at any angle to suit the application. Both fibers and matrix combine to form a single lamina which is a building block of laminate. Composite material is now used in many industries like aircraft, marine, medical, space etc. There are different kind of stresses applied on the material. It is needed to increase the stiffness of the laminate so that it can bear maximum load. Composite laminate generally bears the multi- axial stresses. So, in this paper biaxial stresses on the composite laminate is also studied. Three different composite laminates are considered for the unidirectional stress in given study. These three laminates are balanced symmetrical laminates having symmetry about middle ply. These laminates consist of different number of plies. Laminates have 6, 8 and 10 plies. Thickness also varies as number of plies changes. On these laminates force is applied at one end while at another end laminate is hold fixed. For the bidirectional stresses published results from the work of Daniel are taken and these results are optimized for the maximum stiffness. Optimization done by using the discrete ply orientation as a variable and ply thickness is taken as constant. Displacement of the laminate varies as the orientation of the plies changes. Hyperstudy used for the optimization. In hyperstudy, optimization is carried out using genetic algorithm. Zeid Hasan presented general approach to analyzre composite laminate in uniaxial and biaxial loading using Tsai hill and Tsai Wu theories. [1]. Mohammed Torabizadeh investigated behavior of glass epoxy composite laminate under static loading.[2] C. S. Verma analyzed strength and stiffness of bamboo composite [3] Soden presented details of the mechanical properties of the matrices and unidirectional laminae used in the failure exercise.[4] Rowlands analyze stress and failure analysis of glass epoxy composite plate using strain gauges and FEA.[5] Fereidoon studied progressive failure of glass epoxy laminate under tensile stress.[6] Hisao Fukunaga, Studied failure of composite laminate using statistical method.[7] P. D. Soden analyzed composite laminates having different ply orientation for the biaxial stresses.[8] Daniel studied behavior of graphite epoxy plate under biaxial loading using strain gauges.[9] DV Hemelrijck tested and optimized biaxial stress using the cruciform specimen. [10] M. J. hinton Studied biaxial strength of laminate using laminate theory and simple progressive model. [11] Irina compared mechanical properties of carbon and E- glass fibers with hybrid polymers. [12] II.PROBLEM IDENTIFICATION From Literature review it is clear that tensile stress is generally applied on the composite material. In this study, stiffness of the laminate is increased by decreasing the displacement in the laminate. Optimization is carried out using genetic algorithm by considering discrete ply angles such as 0 0 , ±45 0 , 90 0 for different load cases mentioned in Table 1.