Keywords: laminated composite plates, modified feasible direction, Tsai-Hill, optimal designs.

This current paper addresses the optimization of laminated composite plates subjected to uniform loading. The finite element method and the modified feasible direction method have been used to obtain an optimum laminate in terms of minimizing the deflection and weight of a graphite/epoxy (T300/5208) laminate. The optimal design problem consists of two stages. In the first stage, the fibre orientation is considered as the design variable for the minimizing maximum deflection design and in the second stage, minimum weight is obtained using the Tsai-Hill failure criterion with the optimizing variable then becoming the laminate thickness. Finally, the results are presented for different number of layers, boundary conditions and aspect ratios and compared.

The optimal design of laminated plates for minimum weight and minimum deflection has been investigated by several authors. Adali et al. [1] investigated optimal design of thick laminated sandwich plates based on a higher-order theory of plates including the effects of the normal and shear deformation. Two designs were considered, namely, the minimum weight design and minimum deflection design. Johnson and Sims [2] studied the optimal design of symmetric simply supported plates for two types of loading, applied at the centre of the plate. The plate deflection and optimal fibre angles is calculated using a one term Rayleigh-Ritz approximation. Iyengar and Umeratiya [3] considered symmetrically laminated plates with a combination of simply supported and clamped boundary conditions. Maximum deflection, using the fibre angles as the optimising variable, was minimised for various hybrid laminates. Rahul et al. [4] investigated of hybrid fibre reinforced plastic laminated plates subjected to impact loading. The finite element method and a genetic algorithm have been used to obtain an optimum laminate in terms of minimizing the cost, weight or both cost and weight of graphite/epoxy (T300/5208)-aramid/epoxy (Kevlar 49) hybrid laminates while maximizing the strength.

1

S. Adali, E.B. Summers, V.E. Verijenko, "Minimum weight and deflection design of thick sandwich laminates via symbolic computation", Composite Structures, 29(2), 145-160, 1994. doi:10.1016/0263-8223(94)90096-5

2

A.F. Johnson, G.D. Sims, "Simplified design procedures for composite plates under flexural loading", Composite Structures 2, ed. I. H. Marshall. Applied Science Publishers, London, 20-15, 1983.

3

N.G. Iyengar, J.R. Umeratiya, "Optimisation of hybrid laminated composite plates", ICAS, 1172-1178, 1984.

4

Rahul, G. Sandeep, D. Chakraborty, A. Dutta, "Multi-objective optimization of hybrid laminates subjected to transverse impact", Composite Structures, 73, 360-369, 2006. doi:10.1016/j.compstruct.2005.02.008

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