MINIMUM WEIGHT DESIGN OF THIN-WALLED COMPOSITE STRUCTURES

The aim of the work presented here is to develop an efficient method for the minimum weight design of thin-walled composite structures. A multilevel approach is used for optimization of the structures modeled with layered shell finite elements subjected to stress, system stability and initial failure constraints. The multilevel optimization permits a large problem to be broken down into a number of smaller ones, at different levels according to the type of problem being solved. The optimization method presented here is based on combining optimality criterion (OC) and mathematical programming (MP) algorithms. The finite element analysis (FEA) is used to compute internal forces at the system level. The local stress and local initial failure load in each independent element are defined as component constraints. The use of this MP algorithm is essential to the multilevel approach and local level since it can handle the highly nonlinear component problem, such as local buckling or special initial failure constraints at the mechanically fastened joints. The multilevel algorithm is applied to the minimum-weight design of complex aircraft structures subject to multiple constraints such as aircraft parachute composite beam.