MULTIDISCIPLINARY DESIGN OF COMPOSITE AIRCRAFT STRUCTURES BY LAGRANGE

This paper deals with the application of a structural optimization method in order to find optimal layouts of fibre composite structures in aircraft construction. The goal of the optimization process is to minimize the structural weight and, simultaneously, to fulfil multidisciplinary constraints concerning failure criteria, stability requirements, dynamic responses, aeroelastic efficiencies and flutter speeds. Considering these requirements, the optimal values for the layer thicknesses and the fibre orientations of composite structures must be determined. This problem can be efficiently solved by structural optimization methods. The model formulation in structural optimization will be described in general as well as the special optimization model and the structural and sensitivity analysis for fibre composite structures. An application example demonstrates the performance of the whole procedure. This example shows that the structural optimization method is very useful in increasing the efficiency of the design process as well as the quality and performance of aircraft structures.