Exploiting Semi-analytical Sensitivities From Linear and Non-linear Finite Element Analyses for Composite Panel Optimization

This paper presents a solution procedure developed in the SAMCEF finite element code for the advanced optimal design of stiffened composite panels of an aircraft fuselage. The BOSS quattro, a task manager and optimization toolbox, is used for defining and running the optimization problem. The objective function to be minimized is the weight, and the restrictions depend on structural stability requirements, such as buckling and collapse. The design variables are the panel and stringer thicknesses of the conventional proportions (i.e. 0∘, 90∘ and ±45∘) in a homogenized laminate. Since a collapse analysis introduces geometric nonlinearities into the design process, the function evaluation can take a long time. In order to obtain a rapid optimal solution, a gradient-based method is used, and the first order derivatives need to be computed, in this case with an original semianalytical approach. The sensitivity analysis of buckling and collapse is reviewed. Numerical tests on an industrial case study demonstrate the possibility and the reliability of the approach. Solving such problems is clearly difficult and remains a challenge. Through the applications, this paper provides the opportunity to discuss convergence issues and the use of such advanced optimization techniques in the overall aircraft design process.