Two-level optimization on layout and ply for composite airtight port of airplane

A two-level optimization method for lightweight design of composite airtight port of airplane is proposed. The layout optimization of transverse stiffeners is performed to minimize the strain energy in the first level. Based on the results of the first level optimization, the ply optimization for the inner skin, outer skin, frame and transverse stiffeners is carried out subjected to intensity, rigidity and composite failure criteria constraints in the second level by means of equivalent bending stiffness method and genetic algorithm. The optimal design scheme of the structural layout and ply is achieved by the iteration between the first and second level. A practical airplane port is utilized as an example. The maximum displacement and maximum stress are reduced by 22.7% and 11.2% respectively after layout optimization, the intensity and rigidity of the port are improved obviously. The weight of the port is reduced by 7.69% after ply optimization. This paper provides an effective method for the lightweight design of the composite airtight port.