306 Int. J. Bio-Inspired Computation, Vol. 3, No. 5, 2011 Copyright © 2011 Inderscience Enterprises Ltd. Optimal design of multilayered composite plate using bio-inspired optimisation techniques M. Amrita* Department of Mechanical Engineering, GIT, GITAM University, Gandhi Nagar, Rushikonda, Visakhapatnam-530 045, Andhra Pradesh, India E-mail: amritraj_vib@yahoo.co.in *Corresponding author N. Mohan Rao Department of Mechanical Engineering, University College of Engineering, Kakinada, Jawaharlal Nehru Technological University, Kakinada – 533 003, Andhra Pradesh, India E-mail: nmohan72@rediffmail.com Abstract: Fibre reinforced composite materials are widely used in construction of components of aircraft, ships and marine structures that are subjected to high compression loads. One of the important problems in fibre reinforced composite markets is to find the optimal stacking sequence which tailors the properties of the composite structures. The motivation of the study is to apply the newly developed bio-inspired technique particle swarm optimisation (PSO) and compare its effectiveness with other optimisation techniques genetic algorithm (GA) and pattern search method in the design of composite structures. As a case study, a square and rectangular thick plate subjected to uniaxial or biaxial loading is considered and it is optimised to find the layer orientation which maximises the buckling load. This work showed that GA performs better than PSO and pattern search method and so is the preferable method in design of composite plate structures. Keywords: composite laminates; fibre orientation; uniaxial loading; biaxial loading; optimal design; first-order shear deformation theory; FSDT; buckling analysis; thick plate; particle swarm optimisation; PSO; genetic algorithm; GA; pattern search. Reference to this paper should be made as follows: Amrita, M. and Mohan Rao, N. (2011) ‘Optimal design of multilayered composite plate using bio-inspired optimisation techniques’, Int. J. Bio-Inspired Computation, Vol. 3, No. 5, pp.306–319. Biographical notes: M. Amrita is presently working as an Assistant Professor in the Department of Mechanical Engineering, Gitam Institute of Technology, Gitam University, Visakhapatnam, Andhra Pradesh, India. She has nine years of teaching experience in engineering colleges. She had enrolled for PhD and her areas of interest are composites and optimisation. N. Mohan Rao is presently working as an Associate Professor in the Department of Mechanical Engineering, Jawaharlal Nehru Technological University, Kakinada, Andhra Pradesh, India. He has two years of industrial experience and 12 years of teaching experience in engineering colleges. He had completed his PhD in ‘Robot arm manipulators’. His areas of interest are robotics, composites and optimisation. He has 16 publications in different conferences and journals. 1 Introduction Composite materials are widely used in construction of components of aircraft, ships and marine structures that are subjected to high compression loads, which lead at most of times to the instability problems, by mean of buckling phenomenon. Thus, their buckling response should be given renewed attention. The primary objective in the design of laminated fibre reinforced structures is the selection of lamination arrangement so as to achieve an efficient design. Several authors have discussed the optimum design procedure for thin laminated plates under flexural loading and inplane loading based on maximisation of fundamental frequency, minimisation of maximum stress or both. Very limited work has been done on the optimisation of thick