Layer thickness optimisation in a laminated composite

The paper describes a method to optimise the thickness balance within a composite laminate with layers oriented according to a limited set of angles. The laminate must be symmetric, balanced and loaded in-plane. The optimisation process is particularly suited to be used in conjunction with a finite element program. It provides the designer with the optimal overall engineering characteristics and a list of all the possible orientation combinations ranked with respect to their safety factor. The optimisation method is based on the first order gradient optimum search method and operates iteratively in the engineering elastic characteristics field. The cost function implemented up to now is the structure stiffness but no conceptual limitations exist for different functions. Some simple applications are listed at the end of the paper in order to verify the capabilities of the method. (C) 1997 Elsevier Science Limited.